570.02 Materials.
required tests and submit the test results and shall be full compensation for site restoration after the test.
b.Payment will be made under Item No.: 546–A Micropiles – per linear foot 546–B Micropile Verification Load Test Pile – per each 546–C Micropile Proof Load Test – Per each SOIL NAIL RETAINING WALL
570.01 Description.
This work shall consist of designing and constructing soil nail retaining walls at the locations shown on the Plans. The work shall include excavating in staged lifts in accordance with the approved Contractor’s plan; drilling and installation of the soil nails to the diameter and length required to develop the specified capacity; grouting the nails; providing and installing the specified drainage features; providing and installing bearing plates, washers, nuts, and other required miscellaneous materials; and constructing the temporary shotcrete f ace if required and constructing the final structural facing. The Contractor shall select the excavation, drilling, and grouting methods and the diameter of the drill holes to meet the performance requirements specified herein or as shown on the plans. Soil nail walls used for temporary shoring and which will have a service life less than 18 months may be designed with the less design stringent criteria outlined in Section 570.09 below. The requirements for the construction of shotcrete facing for the wall are given in Section 571.
570.02 Materials.
a.Steel Bars for Soil Nails. The steel bars shall be straight, solid or hollow core and continuous (without splices). The bars shall conform to the requirements given in AASHTO M 31, for Grade 60 or 75, or the requirements given in ASTM A 722 for Grade 150. The bars shall be either deformed bars (deformations for the anchorage coupling), reinforcing bars that are threaded at the end for the anchorage coupling or continuous spiral deformed bars. Bars shall be t hreaded a minimum of 6 inches at the wall anchorage to allow proper attachment of a bearing plate and nut. The threading for the anchorage may also be the continuous spiral deformed ribbing of bar deformations designed for coupling, or threads that are cut into a reinforcing bar. If threads are cut into a reinforcing bar, the threaded portion of the bar shall be 6 inches long and the Contractor shall install the next larger sized bar above the size of the required bar. Larger bars shall be furnished without extra compensation.
b.Coating and Encapsulation of Steel Bars for Soil Nails.
1.Coating. If epoxy coating is shown to be required on the plans, the bars shall be coated by fusion bonded (electrostatically applied) epoxy coating in accordance with the requirements given in ASTM A 775 with the exception that the minimum thickness of coating shall be 0.012 inches. Bend tests will not be required. All other test results shall be furnished to the Engineer before the Engineer will allow the installation of th e bars. Coating will not be required over the threaded end at the wall anchorage. The Contractor shall handle and store epoxy coated bars in a way that will prevent them from being damaged beyond what is permitted by ASTM D 3963. The Contractor shall repai r damaged epoxy coating in accordance with the requirements given in ASTM A 775 and the coater’s recommendations using an epoxy field repair kit recommended by the epoxy manufacturer. All repaired areas shall have a minimum 0.012 inch coating thickness.
2.Encapsulation. The steel bars shall be encapsulated if this is shown to be required on the Plans. The encapsulation shall be a sheath that is composed of grout injected into a tube surrounding the bar. The tube shall be corrugated HDPE tube conforming to the requirements given in AASHTO M 252 for Type C or shall be corrugated PVC tube conforming to ASTM D 1784, Class 13464- B. The wall of the plastic tube shall be a minimum 0.04 inches thick. A minimum of 0.2 inches of grout cover shall be placed over the e poxy coated bar within the plastic tube.
570.02 Materials.
Encapsulated bars shall not be moved or transported until the encapsulation grout has reached a compressive strength of at least 1500 psi but not before 24 hours. The Contractor shall replace damaged encapsulated ba rs.
3.Sampling of Bars. The Contractor shall arrange for the Engineer to select a sample of one bar of each diameter bar for testing after epoxy coating or after encapsulation if encapsulation is required.
c.Sacrificial Steel Loss. If epoxy coating and /or encapsulation are not shown as required in the Plans, the soil nail bars shall be designed for sacrificial steel loss. The following procedure shall be used to calculate the effective bar properties for design:
1.Obtain the values of cross sectional area, A c, nominal (average) inner diameter, di, nominal yield strength, F Y, and nominal ultimate strength, F U, from the manufacturer's data.
2.Calculate the outer diameter, d o, as d o = [(4A c/π) + (d i2)] 0.5
3.Reduce the value of d o by the 0.315 inches. Call this the effective diameter d eff.
4.Calculate the effective area, A ceff, by using d eff instead of d o as A ceff = (π/4) (d eff2 – di2)
5.Calculate the effective section modulus, S eff, and the effective moment of inertia, I eff, for the
6.reduced section as follows: S eff = [(π/32) (d eff4 – di4)]/d eff ; Ieff = (π/64) (d eff4 – di4)
7.Calculate the effective nominal yield strength, F Yeff, and effective nominal ultimate strength, F Ueff, as foll ows: F Yeff = FY (Aceff/Ac) ; F Ueff = FU (Aceff/Ac) The reduction in steel thickness shall also be taken into account for the couplers and nuts.
d.Bearing Plates, Welded Shear Stud Connectors, Nuts and Washers for Anchorage of Soil Nails. Bearing plates, nuts and washers shall conform to the requirements given in Section 836. Bearing plates shall be galvanized according to the requirements given in AASHTO M 111 for Grade 85. Nuts and washers shall be galvanized according to the requirements given in AASHTO M 232 for Class C. Welded shear stud connectors shall be one of those shown in List II -4 of the ALDOT manual "MATERIALS, SOURCES, AND OTHER DEVICES WITH SPECIAL ACCEPTANCE REQUIREMENTS". Studs shall be attached in accordance with the requirements given i n ANSI/AASHTO/AWS D1.5/D1.5M 2008 Bridge Welding Code and Article 836.46. Welded shear studs shall be galvanized according to the requirements given in AASHTO M 111 for Grade 85.
e.Welded Wire Steel Reinforcement for the Shotcrete Wall Face. The welded wire reinforcement shall be the dimensions and wire thickness as shown in the contractor final design drawings and in conformance with the requirements given in Article 835.03. The welded wire mesh shall be galvanized according to the requirements given in AASHTO M 111 for Grade 85.
f.Centralizers for Alignment of Soil Nail. Centralizers shall be installed to align the soil nail in the hole drilled in the soil. Centralizers shall be manufactured from Schedule 40 PVC pipe, steel or other material that will not be detrimental to the performance of the soil nail (wood shall not be used). Centralizers shall have a means for being securely attached to the soil nail. The centralizers shall be sized to position the nail bar within 1 inch of the center of the dril l hole to allow tremie pipe insertion to the bottom of the drill hole and to allow grout to freely flow up the drill hole.
g.Grout. The grout shall be a neat cement or sand/cement grout. The Contractor shall submit the proposed grout mix design to the M aterials and Tests Engineer for approval no later than 30 calendar days prior to production. The Contractor shall make arrangements for an ALDOT approved testing laboratory to test the proposed grout mix design. The mix design shall include the following:
1.A list of all the materials used in the design of the mix with the source and vendor code indicated.
2.Compressive strength test results verifying that the proposed mix design will have a minimum compressive strength of 1500 psi at 3 days, and a minimum comp ressive
570.04 Soil Nail Wall Design and Drawing Submittal.
strength of 3000 psi at 28 days. Compressive strength shall be tested in accordance with the requirements given in AASHTO T 106, " Compressive Strength of Hydraulic Cement Mortar (Using 50 mm or 2 inch Specimens)" . Test results for the proposed gro ut mix that have been completed within one year of the start of work, and that have been performed by an ALDOT approved testing laboratory, may be submitted for verification of the mix design.
h.Shotcrete. Shotcrete shall meet the requirements given in S ection 571.
i.Cement. Cement shall be meet the requirements given in Section 815 and shall be either Type I or III.
j.Film Protection for Overnight Exposure. Sheet materials for overnight exposure protection shall be waterproof material and/or polyeth ylene film conforming to the requirements given in AASHTO M 171.
k.Drainage Materials.
1.Geocomposite Sheet Drain. Geocomposite Sheet Drain shall be manufactured with a drainage core and a drainage geotextile encapsulating the core such as Mirafi G100N, SiteDrain Sheet 184, or an approved equal. The drainage core shall be manufactured from long chain synthetic polymers composed of at least 85 % by weight of polypropylenes, polyester, polyamine, polyvinyl chloride, polyolefin, or polystyrene and shall have a minimum compressive strength of 40 psi when tested in accordance with ASTM D 1621 Procedure A. The geotextile shall have a min imum flow rate of .08 gallons per second per foot of width when tested in accordance with the requirements given in ASTM D 4716. The test conditions shall be an applied load of 10 psi at a gradient of 1.0 after a 100 hour seating period. The Contractor sha ll furnish manufacturer's certified test reports for the geocomposite sheet drain. The test results shall include quantity of material represented by the tests. The material tested shall be taken from the actual production run of material that is furnished for installation. The lot size shall be equivalent to the total amount of drainage mat required for each retaining wall on the project.
2.Underdrain Outlet Pipe. Underdrain and drainage outlet pipe shall meet the requirements given in Section 606.
570.03 Soil Nail Wall Design Requirements.
The soil nail walls shall be designed using the Service Load Design (SLD) procedures contained in the Federal Highway Administration (FHWA) publication “Geotechnical Engineering Circular No. 7, Soil Nail Walls”, Report No. FHWA -NHI-14-007. The required partial safety factors, allowable strength factors and minimum global stability soil factors of safety shall be in accordance with the guidelines given in the FHWA manual, unless specified otherwise by the Engineer. Soil nail corrosion protection requirements, known utility locations, easements, and right of way will be as shown in the plans. Structural design of any individual wall elements not covered in the FHWA manual shall be by the service load or load factor design methods in conformance with "Combinations of Loads" and other appropriate articles of the 17th Edition of the AASHTO Standard Specifications for Highway Bridges including current interim specifications. The Contractor shall be fully responsible for all as sumptions made about the strength of the soil and rock and all implications that the properties of the soil and rock have on the design, constructability and stability of the wall. In accordance with FHWA Geotechnical Engineering Circular No. 7, for design with permanent applications, no more than 56% of the nail’s yield capacity (less any calculated sacrificial steel loss) shall be used.
570.04 Soil Nail Wall Design and Drawing Submittal.
a.Initial Submittal of Design Calculations and Construction Drawin gs. The Contractor shall submit 3 sets of design calculations and Wall Construction Drawings to the State Construction Engineer as an initial submittal. The initial submittal shall also identify the soil nail contractor, the on -site supervisors, and the drill operators and include the experience requirements given in Article 570.05 and Item 570.06(h)3. Changes in personnel will not be permitted without a
570.04 Soil Nail Wall Design and Drawing Submittal.
written request by the Contractor. This submittal should be made within 14 calendar days after the date of the "Notice to Proceed". If clarifications are required, one set will be returned to the Contractor with comments for clarification. The initial submittal will be returned to the Contractor for clarification within 21 calendar days after the receipt of the initial submittal. The Contractor will be allowed 7 calendar days for each clarification of the initial submittal and the Engineer will be allowed 7 calendar days to determine if further clarification is necessary. The Engineer will not approve the s ubmittal of design calculations and Wall Construction Drawings but will review the submittal for completeness. The initial submittal of the design calculations and Wall Construction Drawings shall be sealed by a Licensed Professional Engineer licensed in the State of Alabama , but not employed by the Department .
b.Final Submittal of Design Calculations and Wall Construction Drawings. When the Materials and Tests Engineer informs the Contractor that the design calculations and Wall Construction Drawings ar e complete, the Contractor shall submit 5 sets of calculations and drawings, a Mylar sepia set of the drawings and an electronic file in Adobe Acrobat format of the drawings as a final submittal. The Contractor will be allowed 5 calendar days to make the f inal submittal. The Contractor shall not begin wall construction or incorporate materials into the work until the Materials and Tests Engineer returns one set of the completed design calculations and Wall Construction Drawings to the Contractor. The final submittal of the design calculations and Wall Construction Drawings shall be sealed by a Licensed Professional Engineer licensed in the State of Alabama.
c.Minimum Requirements for the Submittal of Design Calculations.
1.Configuration of the Design Sub mittal. The design calculation sheets shall have the project number, wall location, initials of preparer, and page number at the top of each page. An index page shall be provided to provide a list of the pages of the design calculations. The design calcu lations shall include an explanation of all symbols on the calculations and a description of computer programs used in the design.
2.Description of Design Methodology. The design calculations shall contain a summary of the overall soil nail wall design methodology including references to the applicable design code requirements.
3.Diagrams of the Critical Cross Sections. The design calculations shall include diagrams of the critical design cross section geometry including soil and rock strata and the location, magnitude, and direction of the design slope, external surcharge loads and piezometric levels. The design cross sections shall also include the critical slip surface shown where it will result in the minimum factor of safety, the required na il lengths, and the strengths of the soil nails (nail bar sizes and grades) for each nail row.
4.Physical Properties of the Rock and Soil. The soil and rock shear strengths (friction angle and cohesion), unit weights, and ground -grout pullout resistances and nail drill hole diameter assumptions shall be shown for each soil and rock strata. Geotechnical data is provided in the contact documents. Supplementary geotechnical data may be available and may be obtained from the Materials and Tests Engineer.
5.Factors of Safety and Load Combinations. Partial safety factors and strength factors (for Service Load Design, "SLD") or load and resistance factors (for Load and Resistance Factor Design, "LRFD") shall be shown for the global stability, pullout resistance, nail bar tensile strength, surcharges, soil and rock unit weights, nail head strengths, and steel, shotcrete, and concrete materials. Load combinations and design loads used shall be given for a 75 year service life design for each wall on the project.
6.Wall Facing and Soil Nail Anchorage. The design calculation submittal shall also include design calculations for the wall facing and nail anchorage including an analysis of the facing flexural strength, punching shear strength, tensile strength of the headed studs if used, and the upper cantilever and minimum reinforcement ratio.
570.04 Soil Nail Wall Design and Drawing Submittal.
d.Minimum Requirements for the submittal of Wall Construction Drawings.
1.Plan View of the Wall. A drawing of the plan view of the wall shall be submitted. The following deta ils shall be shown on the plan view: • A reference baseline and elevation datum; • The offset from the construction centerline or baseline to the face of the wall at its base at all changes in horizontal alignment; • Beginning and end of wall stations; • Right -of-way and permanent or temporary construction easements limits, location of all known active and abandoned existing utilities, adjacent structures and other potential interferences. • The centerline of any drainage structure or drainage pipe behind, passing through, or passing under the wall; • Limit of longest nail.
2.Elevation View of the Wall. A drawing of the elevation view of the wall shall be submitted. The following details shall be shown on the elevation view: • The elevation at the top of the wall, at all horizontal and vertical break points, and at least every 30 feet along the wall; • Elevations at the wall base and the top of leveling pads for any cast in place facing; • Beginning and end of wall stations; • The distance along the face of the wall to all steps in the wall base; • Vertical and horizontal nail spacing with identification number assigned for each nail; • The location of wall drainage elements; • Expansion/contraction joints in the facing (if applicable); • Existing and finish grade profiles both behind and in front of the wall; • A listing of the quantities for each partial view of the wall.
3.Plan Notes and Miscellaneous Details. Plan notes shall be placed on the Wall Construction Drawings to provide the information required to identify the design process and to serve as the requirements for the construction of the wall. This information shall be: • A description of the design parameters with references to the applicable design codes; • General notes for constructing the wall including construction seq uencing; • Horizontal and vertical curve data affecting the wall and wall control points; • Match lines and other details to tie the wall stationing to the centerline stationing; • A listing of the total summary of quantities showing the square yards of wall fac e areas, length of nails, amount of grout and other items of work; • Nail wall typical sections including staged excavation lift elevations, the batter of the wall and excavation face, and nail size, spacing and inclination, and the details of corrosion prot ection; • Drilling methods and equipment, including the drill hole diameter and any variation of the required diameters along the wall alignment; • Grouting placement procedures and equipment; • Provisions for drain holes behind the wall; • Typical details of production nails and test nails defining the nail length, minimum drill hole diameter, inclination, and test nail bonded and unbonded test lengths; • Details, dimensions, and schedules for all nails, reinforcing steel, wire mesh, bearing plates, headed studs and/or attachment devices for shotcrete, cast -in- place or prefabricated facings; • Dimensions and schedules of all reinforcing steel including reinforcing bar bending details;
570.05 Approved List of Soil Nail Wall Specialty Contractors.
• Details and dimensions of all wall appurtenances such as barriers, coping, drainage g utters and fences; • Details for constructing walls around drainage facilities; • Details for terminating walls and adjacent slope construction; • Details and procedures for performing the soil nail load capacity verification tests; • Typical details of instrument ation installation along the verification nails, including the list of proposed instruments, complete and detailed installation procedures, a wiring diagram detailing the wiring of the instruments to the central readout panels, shop drawings and specificat ions for ancillary equipment such as readout panels, protective covers, conduit, and enclosures; • Details and procedures for performing the soil nail proof load tests; • Examples of forms used for documentation of installation and testing.
570.05 Approved Li st of Soil Nail Wall Specialty Contractors.
The following soil nail wall design -build specialty Contractors are approved: Richard Goettle, Inc. 12071 Hamilton Ave. Cincinnati, OH 45231 Rick Slack Phone: 513 -825-8100 Hayward Baker, Inc. 515 Nine North Court Alpharetta, GA 30004- 3961 John Wolosick, P.E. Phone: 770 -442-1801 Schnabel Foundation Co. 1654 Lower Roswell Road Marietta, GA 30068 Stephen Dimino Phone: 770 -971-6455 F & W Construction PO Box 1549 Ozark, AL 36361 Phone: 334- 774-2678 GeoStabilization International 2841 North Avenue Grand Junction, CO 81501 Reid Bailey Phone: 423- 619-8576 www.geostabilization.com Russo Corporation 1421 Mims Avenue SW Birmingham, AL 35211 Phone: 205- 923-4434 www.russocorp.com Other soil nail wall specialty Contractors will be given consideration for approval. Consideration for approval will be given to specialty Contractors that can provide documentation that they have successfully designed and constructed at least 3 projects in the last 3 years where the construction of permanent soil nail retaining walls totals at least 1000 square yards of wall face area and at least 500 permanent soil nails.
570.06 Construction Requirements.
a.Site Drainage Control. The Contractor shall control all surface water that will affect construction of the soil nail retaining wall. The Contractor shall maintain all pipes or conduits used to control surface water during construction. Damage caused by surface water shall be repaired without extra compensation. Upon substantial completion of the wall, surface water control pipes or conduits shall be removed from the site as directed by the Engineer. Alternatively, with the approval of the Engineer, pi pes or conduits that are left in place may be fully grouted and abandoned or left in a way that protects the structure and all adjacent facilities from the migration of fines through the pipe or conduit creating potential ground loss. Localized areas of pe rched water seepage may be encountered during excavation at the interface of geologic units or from localized groundwater seepage areas. The Contractor shall immediately notify the Engineer if unanticipated existing subsurface drainage structures are disco vered during excavation. The work shall be suspended in these areas until remedial measures meeting the Engineer’s approval are implemented. The cost of remedial measures required to capture and dispose of water resulting from encountering unanticipated su bsurface drainage structures will be paid for as Extra Work. All surface water runoff flows and flows from existing subsurface drainage structures shall be captured and directed separately from the wall drainage network. These flows shall be conveyed to an outfall structure or storm sewer, as directed by the Engineer.
b.Excavation.
1.Safety During Excavation and Compliance With Wall Construction Drawings. The Contractor shall carefully monitor the excavation work to make sure that the soil nail wall is safely constructed. The wall construction and excavation sequence shall be performed in accordance with the requirements shown on the submitted Wall Construction Drawings as distributed
570.06 Construction Requirements.
by Engineer. Excavations that are steeper or deeper than those shown on the Wall Construction Drawings shall not be made without written approval of the Engineer.
2.Excavation and Wall Alignment Survey Control The Contractor shall provide all the necessary survey and alignment controls for all excavation work. The Contract or shall locate and drill each drill hole within the allowable tolerances. The excavation shall be performed in a manner which will allow the construction of the shotcrete construction facing to the required minimum thickness and to the required lines and grades. Where the as -built location of the front face of the shotcrete exceeds the allowable tolerance from the wall control line shown on the Wall Construction Drawings, the Contractor shall be responsible for determining and bearing the cost of remedia l measures necessary to provide proper attachment of nail head bearing plate connections and satisfactory placement of the final wall facing.
3.Coordination of General Roadway Excavation with Wall Excavation. The Contractor shall complete the clearing, grubbing, grading and excavation above and behind the wall before beginning the wall excavation. The initial excavation shall not extend beyond the original ground elevation behind the wall or at the ends of the wall or beyond the limits shown on the soil na il Wall Construction Drawings. Due to the close coordination that is required between the work of the soil nail wall design -build specialty Contractor and the forces performing the excavation work, the excavation shall be performed as directed by the Engin eer. The Engineer will be advised by the soil nail wall specialty Contractor of the need for setting the limits of excavation to allow the construction of the wall as proposed by the specialty Contractor. For any required rock blasting within 200 feet of t he soil nail wall the contractor shall submit a plan for the blasting using controlled blasting techniques. The plan shall be designed by a qualified Blasting Consultant deemed qualified for this work by the Engineer. Blasting shall not begin until the Engineer informs the Contractor that the blasting plan is adequate to describe the blasting and the Contractor accepts complete responsibility for the results of the blasting. Blasting shall not damage completed soil nail work or disrupt the areas where soil nails are required to be installed and shotcrete placed for the wall. The contractor shall repair any damaged areas without compensation. General roadway excavation shall be done in coordination with the soil nailing work.
4.Soil Nail Wall Structure Excav ation. The Contractor shall perform the excavation to the final wall face using procedures that: • Prevent over excavation; • Prevent ground loss, swelling, air slaking, or loosening; • Prevent loss of support for completed portions of the wall; • Prevent loss of soil moisture at the face; • And prevent ground freezing. There will be no extra payment for costs associated with additional thickness of shotcrete or concrete or other remedial measures required due to irregularities in the cut face, excavation overbreak o r inadvertent over excavation. The exposed unsupported final excavation face cut height shall not exceed the vertical nail spacing plus the required reinforcing lap or the short -term stand -up height of the ground, whichever is less. The Contractor shall complete excavation to the final wall excavation line and complete the application of the shotcrete in the same work shift unless approved otherwise by the Engineer. Application of shotcrete may be delayed up to 24 hours if the Contractor can show that the delay will not adversely affect the stability of the excavation face of the wall. Placement of a polyethylene film over the face of the excavation may be required by the Engineer to reduce degradation of the cut face caused by changes in moisture. Damage to existing structures or completed portions of the wall structure shall be repaired without extra compensation where approval is given by the Engineer for the extended face exposure period. At the Contractor’s option, during each excavation lift, nails may be drilled and installed through a temporary stabilizing berm if this is shown on the Wall Construction Drawings. The purpose of the stabilizing berm is to prevent or minimize instability or sloughing of the final excavation face due to ground conditio ns and drilling action. The stabilizing berm geometry shall be such that the top of berm extending horizontally out from the bottom front face of the overlying shotcrete a distance of 1 foot and cut down from that point to the base grade for that excavatio n lift at the slope not steeper than 1H:1V. The Contractor may use different berm geometry, upon satisfactory demonstration that the different geometry provides satisfactory performance.
570.06 Construction Requirements.
Following the installation of nails in that lift, the Contractor shal l excavate the temporary stabilizing berm to the final wall face excavation line and clean the final excavation face of all loose materials, mud and other foreign matter which could prevent or reduce shotcrete bond. The Contractor shall ensure that install ed nails and corrosion protection are not damaged during excavation of the stabilizing berm. The Contractor shall repair or replace nails or corrosion protection that are damaged or disturbed during excavation of the stabilizing berm as directed by the Eng ineer without extra compensation. The Contractor shall not excavate the stabilizing berm until the nail grout has achieved a compressive strength of 1500 psi but not before 24 hours. Hardened nail grout protruding from the final wall excavation line more than 2 inches shall be removed in a manner that prevents the fracturing of the grout at the nail head. Sledge hammer removal of grout is not allowed. The use of hand held rock chippers is acceptable provided their use does not damage or disturb the remaini ng grout at the nail head, the nail bar or corrosion protection. Alternate excavation and soil nail installation methods that meet these objectives may be submitted to the Engineer for consideration by the Engineer. Excavation to the next lift shall not pr oceed until nail installation, reinforced shotcrete placement, attachment of bearing plates and nuts and nail testing has been completed and accepted in the current lift. Nail grout and shotcrete shall have cured for at least 72 hours and shall have a minimum compressive strength of 1500 psi before the excavation of the next underlying lift. The Contractor shall notify the Engineer immediately if raveling or local instability of the final wall face excavation occurs. Unstable areas shall be temporarily st abilized by means of buttressing the exposed face with an earth berm or other methods. The Contractor shall suspend work in unstable areas until remedial measures are developed.
5.Wall Discontinuities. Where the Contractor’s excavation and installation m ethods result in a discontinuous wall along any nail row, the ends of the constructed wall section shall extend beyond the ends of the next lower excavation lift by at least 10 feet. Slopes at these discontinuities shall be constructed to prevent sloughing or failure of the temporary slopes. If sections of the wall are to be constructed at different times, prevent sloughing or failure of the temporary slopes at the end of each wall section.
6.Excavation Face Protrusion, Voids, or Obstructions. The Contract or shall remove all or portions of cobbles, boulders, rubble or other subsurface obstructions encountered at the wall final excavation face which will protrude into the design shotcrete facing. The Contractor shall be responsible for determining the metho d of removal of face protrusions, including the method required to safely secure remnant pieces left behind the excavation face and for promptly backfilling voids resulting from removal of protrusions. The Contractor shall notify the Engineer of the propos ed method for removal of face protrusions at least 24 hours prior to beginning removal. Voids, overbreak and excessive excavation beyond the wall excavation line shall be backfilled with shotcrete. Removal of face protrusions and backfilling of voids and a reas of excessive excavation shall be incidental to the work of constructing the wall.
c.Shotcrete. Shotcrete shall be placed in accordance with the requirements given in Section 571. Where shotcrete is used to complete the top ungrouted zone of the nai l drill hole near the face, the nozzle shall be placed in the mouth of the drill hole to completely fill the void. The contractor shall attach a bearing plate and nut to each nail head as shown on the Wall Construction Drawings. While the shotcrete is stil l plastic the bearing plate shall be uniformly seated on the shotcrete by hand wrench tightening of the nut. If uniform contact is not achieved between the plate and shotcrete, the nut shall be tightened by hand wrench tightening after the shotcrete has ac hieved initial set at 500 psi. (Initial set of the shotcrete is defined in Section 571.) The plate shall be set in a bed of grout where uniform contact between the plate and shotcrete cannot be provided. The nut shall be tightened by hand wrench tightening after the grout has achieved 1500 psi but not before 24 hours. If headed studs are required on the anchor plates they shall be located within the tolerances shown on the Wall Construction Drawings.
d.Nail Installation.
1.Contractor's Responsibility for Soil Nail Configuration. The Contractor shall determine the required drill hole diameters, soil nail orientation, drilling method, grout composition and installation method necessary to achieve the nail pullout resistances shown in the Wall Construction D rawings.
570.06 Construction Requirements.
2.Load Verification Testing. Drilling and installation of production nails will not be permitted in any soil or rock strata unit until successful load verification testing of nails is complete in that unit and the results are acceptable to the E ngineer. If requested in writing, the Contractor may begin installation of production soil nails before verification testing is complete if approved in writing by the Engineer. If verification testing results in a change to the original soil nail design, then the Contractor will be responsible at no additional cost to the Department for the installation of any additional soil nails required to meet the new soil nail design requirements. Load verification test nails shall be installed using the same equip ment, methods, nail inclination and drill hole diameter as planned for the production nails. The number and location of the verification test nails shall be as shown on the Wall Construction Drawings. Verification test nails may be installed through the ex isting slope face prior to start of wall excavation, drill platform work bench, stabilization berm or into slot cuts made for the particular lift in which the verification test nails are located. Slot cuts shall only be large enough to safely accommodate t he drill and test nail reaction set up. If approved by the Engineer, verification test nails may also be installed at angle orientations other than perpendicular to the wall face or at different locations than required, as long as the Contractor can demons trate that the test nails will be bonded into the ground which is representative of the ground at the verification test nail locations designated on the Wall Construction Drawings.
3.Allowable Placement of Facing Before Installation of Soil Nails. At the request of the Contractor, and with the Engineer's approval, the shotcrete facing may be placed before drilling and installing the nails. A blockout shall be provided through the shotcrete facing at drill hole locations using PVC pipe or other suitable mat erial, to prevent damage to the facing during drilling. As part of the required design submittals, the Contractor shall provide the Engineer with acceptable structural design calculations demonstrating that the facing structural capacity will not be reduc ed and that the bearing plates are adequate to span the nail drill hole blockout through the construction facing. If the presence of a blockout requires larger size bearing plates or additional reinforcement beyond that shown on the Wall Construction Draw ings, there will be no extra compensation for this work.
4.Optional Sealing Layer for Protection of Face Of Excavation. Where necessary for stability of the excavation face, the Contractor shall have the option of placing a sealing layer (flashcoat) of un reinforced shotcrete or steel fiber reinforced shotcrete or of drilling and grouting of nails through a temporary stabilizing berm of native soil to protect and stabilize the face of the excavation. There will be no extra compensation for a sealing layer.
5.Adjustments to Number and Location of Soil Nails. The Engineer may add, eliminate, or relocate nails to accommodate actual field conditions. Cost adjustments associated with these modifications shall be made as Extra Work. There will be no extra comp ensation for the cost of any redesign, additional material, or installation modifications resulting from actions of the Contractor.
6.Orientation and size of Drilled Holes for the Soil Nails. The drill holes for the soil nails shall be made at the locatio ns, orientations, and lengths shown on the Wall Construction Drawings as directed by the Engineer. The Contractor shall select the drilling equipment and methods suitable for the physical properties of the ground where the nails will be installed. The Cont ractor shall set the diameter of the drill hole that will result in the required load capacity of the nail and to also provide a minimum of 1/2 inch grout cover over the soil nail bars.
7.Removal of Drill Cuttings. Drilling muds such as bentonite slurry shall not be used to assist in drill cutting removal. Compressed air may be used for cutting removal. The Contractor may be allowed to use water, neat cement grout, or foam flushing upon successful demonstration to t he Engineer that the installation method provides adequate nail pullout resistance. If caving ground is encountered, the Contractor shall use cased drilling methods or other suitable means to support the sides of the drill holes.
570.06 Construction Requirements.
8.Drilling through Hard M aterials. Where hard drilling conditions such as rock, cobbles, boulders, or obstructions are expected or encountered during drilling, percussion or other suitable drilling equipment capable of drilling and maintaining stable drill holes through these mate rials shall be used. If percussion drilling is used the drilling operations shall be immediately suspended or modified if ground subsidence is observed, if the soil nail wall is adversely affected, or if adjacent structures are damaged. The Contractor shal l immediately stabilize the excavation, wall and adjacent structures if adverse conditions occur. This stabilization shall be done without extra compensation.
9.Placement of Soil Nail Bars in Drilled Holes. Centralizers shall be spaced along each soil nai l so that the maximum spacing does not exceed 10 feet between the centers of the centralizers. Centralizers shall also be located 2 feet from the top and bottom of the drill hole. Centralizers shall be securely attached to the bar so they will not shift during handling or insertion into the drill hole. Centralizers shall be oriented to allow grout tremie pipe insertion to the bottom of drill hole and allow the grout to flow freely up the hole. Each soil nail bar shall be inspected before installation and sh all be repaired or replaced if the encapsulation is damaged. Uncased drill holes shall be checked for cleanliness prior to insertion of the soil nail bar. The Contractor shall provide a light source capable of adequately illuminating the bottom of each soi l-nail drill hole. The light source shall be provided for the exclusive use of the Engineer. Soil nail bars shall be inserted without forcing the insertion in a way that may damage the drill hole or the soil nail bar. Partially inserted soil nail bars shal l not be driven into the drill hole. Soil nails which cannot be fully inserted to the required depth shall be removed and the drill hole shall be cleaned to allow unobstructed installation. When using cased or hollow stem auger drilling equipment which does not allow for the centralizers to pass through the casing or auger stem, the Contractor may delete the centralizers if the grout pumped through the casing is placed using grout pressures greater than 150 psi or if the grout placed through the stem of the auger has a consistency of less than 125 % when tested in accordance with the requirements given in ASTM C 1107, " Standard Specification for Packaged Dry, Hydraulic -Cement Grout (Nonshrink)" .
10.Soil Nail Installation Tolerances. Soil nails shall not extend beyond the right -of-way or easement limits shown on the Plans. The allowable deviation of the soil nail head location shall be a maximum of 6 inches in any direction. The allowable deviation in the soil nail inclination shall be a maximum of 3 degre es. Location tolerances are applicable to only one nail and are not accumulative over large wall areas. The soil nail bars shall be centered within 1 inch of the center of the drill hole. Soil nails that are not installed within the allowable tolerances due to the Contractor’s installation methods shall be replaced without extra compensation.
11.Abandoned Drill Holes. Drill holes where unanticipated obstructions are encountered during drilling shall be relocated, as directed by the Engineer. The cost of drilling and backfilling drill holes abandoned due to unanticipated obstructions will be paid as Extra Work. There will be no extra compensation for the cost of drilling and backfilling drill holes abandoned due to errors made by the Contractor.
e.Grou ting.
1.Testing of Grout placed for Anchorage. Grout placed for the anchorage of the soil nails shall have a minimum compressive strength of 1500 psi at 3 days, and a minimum compressive strength of 3000 psi at 28 days when tested in accordance with the requirements given in AASHTO T 106. The Contractor shall make arrangements for an ALDOT approved testing laboratory to make specimens and test the grout each day that grout is being placed. Three cubes (2 inch x2 inch) for each test age shall be produced at a frequency of at least once per every 30 cubic yards, or fraction thereof, of grout placed. Cubes shall be molded and cured in accordance with the requirements of AASHTO TP 83, “Sampling and Fabrication of 50- mm (2in.) Cube Specimens Using Grout (Non- Shrink) or Mortar”, and tested in accordance with the requirements given in AASHTO T 106. Test reports shall be delivered to the Engineer within 24 hours from testing.
570.06 Construction Requirements.
2.Grouting Equipment. Grout equipment shall produce a uniformly mixed grout free of lumps and shall be capable of continuously agitating the mix. A positive displacement grout pump shall be used. The grout pump shall be equipped with a pressure gauge which can measure at least twice but not more than three times the intended grout pressure. Th e grouting equipment shall be sized to enable the entire nail to be grouted in one continuous operation.
3.Time of Placing Grout. Grout shall be placed within 60 minutes after mixing. Grout not placed in the allowed time limit will be rejected.
4.Grouting Methods. Each drill hole shall be grouted during drilling or within 2 hours of completion of drilling, unless otherwise approved by the Engineer. Grout shall be injected through a tremie, casing, hollow -stem auger, or drill rods at the lowest point of each drill hole. The outlet end of the conduit delivering the grout shall be kept below the surface of the grout as the conduit is withdrawn to prevent the creation of voids. The drill holes shall be filled in one continuous operation. Cold joints i n the grout column are not allowed except at the top of the test bond length of proof load tested production nails. At the Contractor’s option, the tremie may remain in the hole provided it is filled with grout. Grouting before insertion of the nail is all owed provided the nail bar is immediately inserted through the grout to the specified length without difficulty. During casing removal for drill holes advanced by either cased or hollow -stem auger methods, a sufficient level of grout shall be maintained within the casing to offset the external groundwater and soil pressure and prevent hole caving. The grout head or grout pressures shall be maintained to ensure that the drill hole will be completely filled with grout and to prevent unstable soil or groundw ater from contaminating or diluting the grout. The grout pressures shall be recorded for soil nails installed using pressure grouting techniques. Grout pressures shall be controlled to prevent excessive ground heave or fracturing. The grout pressure gaug e shall be capable of measuring at least twice but not more than three times the intended grout pressure. The grout and soil nail shall be removed if grouting is suspended for more than 30 minutes or grouting is not in compliance with the general requireme nts for grouting. Fresh grout and an undamaged soil nail bar shall be placed without extra compensation if the grouting is unacceptable.
f.Wall Drainage Network. The contractor shall install and secure all elements of the wall drainage network as shown o n the Wall Construction Drawings or as required by the Engineer to suit the site conditions. The drainage network shall consist of installing geocomposite drain strips, connection pipes and wall footing drains as shown on the Wall Construction Drawings or as directed by the Engineer. Exclusive of the wall footing drains, all elements of the drainage network shall be installed prior to shotcreting. Unanticipated subsurface drainage features exposed in the excavation cut face shall be captured independentl y of the wall drainage network and shall be mitigated prior to shotcrete application. Costs due to the required mitigation will be paid for as Extra Work. Geocomposite Drain Strips shall be installed with the drain strips centered between the columns of nails as shown on the Wall Construction Drawings. The drain strips shall be at least 12 inches wide and shall be placed with the geotextile side against the ground. The contractor shall secure the strips to the excavation face and prevent shotcrete from con taminating the ground side of the geotextile. Drain strips shall be vertically continuous. Splices shall be made with a 12 inch minimum overlap so that the flow of water will not be impeded. The contractor shall repair any damage to the geocomposite drain strip, which may interrupt the flow of water. The contractor shall install footing drains at the bottom of each wall shown on the Wall Construction Drawings. The drainage geotextile shall envelope the footing drain aggregate and pipe and shall conform to t he dimensions of the trench. The drainage geotextile shall overlap the top of the drainage aggregate as shown on the Wall Construction Drawings. The contactor shall repair or replace damaged or defective drainage geotextile without extra compensation. Connection pipes, as shown on the Wall Construction Drawings, shall direct water from the geocomposite drain strips into the footing drain or to the exposed face of the wall. The connection pipes shall be connected to the drain strips using either prefabricated drain grates as shown on the Wall Construction Drawings or the alternate method of connection. The drain grate shall be installed
570.06 Construction Requirements.
per the manufacturer’s recommendations. The joint between the drain grate and the drain strip and the discharge end of the c onnector pipe shall be sealed to prevent shotcrete intrusion. An alternative method for connecting the connector pipe to the drain strip shall be cutting a hole slightly larger than the diameter of the pipe into the strip plastic core but not through the geotextile. The contractor shall wrap both ends of the connection pipe in the geotextile in a manner that prevents migration of fines through the pipe. The connector pipe inlet end where it penetrates the drain strip and the discharge end shall be taped o r sealed in a manner that prevents penetration of shotcrete into the drain strip or pipe. To assure passage of groundwater from the drain strip into the connector pipe, the contractor shall slot the inlet end of the connector pipe at every 45 degrees aroun d the perimeter of the pipe to a depth of 0.25 inches. Weepholes shall be provided through the construction facing to drain water from behind the facing. Weepholes shall be installed as shown on the Wall Construction Drawings. Drainage outlet pipe shall be used to form the weephole through the shotcrete. The end of the pipe contacting the soil with the drainage geotextile shall be covered. Intrusion shall be prevented into the discharge end of the pipe.
g.Load Testing of Soil Nails. The Contractor shall perform both load capacity verification testing prior to the installation of production nails and proof load testing of designated production test nails. Load capacity verification tests shall be performed on sacrificial test nails at the locations shown on the Wall Construction Drawings. Proof load tests shall be performed on production nails at locations selected by the Engineer. The required load test data will be recorded by the Engineer.
h.Verification Testing of Sacrificial Test Nails.
1.Purpose an d Extent of Load Capacity Verification Tests. Load capacity verification testing shall be performed prior to installation of production nails as a means to validate the theoretical nail pullout resistance. It shall also be a demonstration of the Contractor ’s installation methods. A minimum of 2 verification tests shall be performed in each different soil or rock strata and for each different drilling or grouting method proposed to be used. Tension loads shall be applied to a sacrificial test nail in increasing increments. The movement of the nail due to the increasing load will be monitored. The load in the nail and the corresponding movement of the nail will be used in evaluating the proposed construction methods and details. Excessive movement of the nail due to the loading is evidence that the details of the soil nail are inadequate to carry the load of the wall. Verification test nails shall be sacrificial and shall not be incorporated as production nails. The bars installed for testing shall be epoxy coated and encapsulated, if epoxy coating and/or encapsulation is required, in the same manner as the production bars.
2.Submittal of Details of Load Capacity Verification Tests. The Contractor shall submit the details of the verification testing arrange ment including the method of distributing test load pressures to the excavation surface (reaction frame), test nail bar size, grouted drill hole diameter and reaction frame dimensioning. Testing equipment shall include dial gauges, dial gauge support, a jack and pressure gauge, an electronic load cell, strain gauges, and readout panels. The load cell is required for the creep test portion of the verification test. Where temporary casing of the unbonded length of test nails is proposed, the details shall be submitted to show how the casing will be prevented from reacting with the grouted bond length of the nail and the testing apparatus. The Engineer will review the submittal for completeness. The requirement for this submittal is given with the requirements for the submittal of the details of the wall. The testing shall not begin until the Engineer informs the Contractor that the submittal is complete.
3.Instrumentation Details of Load Capacity Verification Tests. The Contractor shall instrument the verification test nails to obtain direct measurements of axial strains and evaluate the load transfer along the length of the nails. The instrumentation shall be installed within both the bonded and unbonded portions of the verification nails. The gauges shall be installed either along the length of the nail or, in the case of hollow bar soil nails, within the hollow portion of the bar, after final grouting. The Contractor shall develop an instrumentation plan which s hall be submitted with the Wall Construction Drawings. The instrumentation shall be installed by a qualified geotechnical instrumentation specialist having experience in the design and installation of instrumentation systems on at least 3 similar projects. The Contractor shall submit the experience record(s) of the individual(s)
570.06 Constr uction Requirements.
responsible for instrument installation and testing. The requirement for this submittal is given with the requirements for the submittal of the details of the wall design and draw ings. At the completion of each verification nail test, the Contractor shall supply the Engineer with a plot of the load versus depth along the length of the nail, along with calculations of bond stresses along the bond zone of the tested nail. The Engineer will verify that the load transfer values used in the design are valid based on the verification test results.
4.Load Capacity Verification Test Equipment. The reaction frame shall be sufficiently rigid and of adequate dimensions so that excessive deformation of the testing equipment does not occur. If the reaction frame will bear directly on the shotcrete facing, it shall be designed to prevent cracking of the shotcrete. The reaction frame shall be supported independently of the soil nail and shall be configured to allow the placement of the jack over the nail bar so that the bar does not carry the weight of the testing equipment. The configuration of the testing apparatus shall be designed so that the jack, bearing plates, and stressing anchorage will not need to be repositioned during a test. The load shall be applied with a hydraulic jack and measured with a pressure gauge. The pressure gauge shall be graduated in 75 psi increments or less. The jack and pressure gauge shall have a load range not exc eeding twice the anticipated maximum test pressure. Jack ram travel shall be sufficient to allow the test to be done without resetting the equipment. All jacks, pressure gauges, pumps and load cells shall have been calibrated with each other within the las t 6 months by an independent AASHTO accredited laboratory or by a Department laboratory. Calibrated jacks, gages, pumps and load cells shall have identifiable serial numbers to insure traceability to calibration tests. The nail head movement shall be measu red with a dial gauge capable of measuring the movement to an accuracy of 0.001 inch. The dial gauge shall have a travel sufficient to allow the test to be done without having to reset the gauge. The dial gage shall be designed to be aligned parallel with the axis of the nail. The dial gage shall be supported independently from the jack, wall and reaction frame. Two gages will be required when the load reaction is placed on the face of a soil cut.
5.Installation of Sacrificial Test Nail for Load Verific ation Tests The Contractor shall install the sacrificial test nails using the same equipment, installation methods, nail inclination, and drill hole diameter that is proposed for the production nails. Changes in the drilling or installation method will re sult in the requirement for additional verification testing as determined by the Engineer. Additional verification testing shall be performed by the Contractor without extra compensation. Payment for additional verification tests required due to differing site conditions, if determined by the Engineer, will be made at the contract unit price for this work.
6.Required Strength of Nail Grout and Shotcrete Prior to Load Testing. Verification load testing shall not be performed until the nail grout and shotcr ete facing have cured for at least 72 hours and have attained the required compressive strength of 1500 psi. Load testing in less than 72 hours may be allowed if the Contractor submits compressive strength test results showing that the compressive strength of the grout and shotcrete is 1500 psi, but no load test shall be performed before 24 hours regardless of the strength of the grout and shotcrete. The Contractor shall make arrangements for an ALDOT approved testing laboratory to test the grout.
7.Bonde d and Unbonded Lengths of Sacrificial Test Nails. Load verification test nails shall have both bonded and unbonded lengths. The bonded length of the nail shall be grouted prior to testing. The bonded length shall be determined based on the nail bar grade a nd size and the theoretical pullout resistance of the nail. The bonded length shall not be less than 10 feet. The unbonded length shall not be less than 3 feet.
8.Allowable Load on Bar of Sacrificial Test Nail. A test load shall be determined based on th e theoretical pullout resistance of the soil or rock that a production nail will be embedded in. This test load shall not be greater than the allowable tensile stress of the bar. The allowable tensile stress during testing shall not be greater than 90 % of the yield strength for Grade 60 and Grade 75 bars, or 80 % of the ultimate strength for Grade 150 bars. Loads larger than the load capacity of the production bars may be required to safely test the theoretical pullout resistance where the minimum 10 -foot bonded length is required. The Contractor shall provide larger verification test bar sizes if a larger bar is required to safely apply the load required for the measurement of the movement of the test nail under load.
570.06 Construction Requirements.
9.Determination of the Maximum Bonded Length of a Sacrificial Test Nail. A maximum bonded length shall be constructed for the verification test of a sacrificial test nail. The maximum bonded length shall first be calculated based on the strength of the production soil nail bar and the pullou t resistance of the soil or rock. The required test load shall then be calculated based on the bonded length of the test nail and the pullout resistance. If the maximum bonded length from the initial calculation is less than 10 feet the required maximum bo nd length shall be 10 feet. The required test load shall then be calculated based on the bonded length of the test nail and the pullout resistance of the 10 foot bonded length. The load carrying capacity of the nail bar shall then be checked. A larger size bar shall be furnished if this is required to carry the test load. The following equation shall be used for determining the verification test nail maximum bonded length: LBV = C f y As/2 Q d, or 120 inches, whichever is greater; • LBV = Maximum Verification Test Nail Bonded Length (inches); • C = 0.9 for Grade 60 and 75 bars and 0.8 for Grade 150 bars; • fy = Bar Yield or Ultimate Stress (pounds per square inch); (Note: fy = 60,900 psi, 75,400 psi and 150,100 psi respectively for grade 60, 75 and 150 bars) ; • As = Bar Steel Area (square inches); • 2 = Pullout resistance safety factor; • Qd = Allowable pullout resistance (pounds per inch) of grouted nail.
10.Determination of th e Verification Test Load. The following equation shall be used for determining the Verification Test Load (VTL): VTL = L BV X Q d; • VTL = Verification Test Load (pounds).
11.Verification Loading of a Sacrificial Test Nail. Verification test nails shall be incrementally loaded to a maximum load of 200 % of the Verification Test Load (VTL) in accordance with the following loading schedule. The soil nail movements shall be recorded at the end of each load increment. VERIFICATION TEST LOADING SCHEDULE LOAD HOLD TIME AL = 0.05 VTL, Max. 1 minute 0.25 VTL 10 minutes 0.50 VTL 10 minutes 0.75 VTL 10 minutes 1.00 VTL 10 minutes 1.25 VTL 10 minutes 1.50 VTL (Creep Test) 60 minutes 1.75 VTL 10 minutes 2.00 VTL (Max. Test Load) 10 minutes The alignment load (AL) shall be applied to align the testing apparatus and shall not exceed 5 % of the Verification Test Load (VTL). Dial gauges for measuring the movement of the test nail shall be set to “zero” after the alignment load has been applied. Each load increment after the alignment load shall be held for at least 10 minutes except for the creep test load increment. The verification test nail shall be monitored for creep for a minimum of 60 minutes at the 1.50 VTL load increment. Nail movement sha ll be recorded during the creep portion of the test at 1 minute, 2, 3, 4, 5, 6, 10, 20, 30, 50, and 60 minutes. The load during the creep test shall be maintained within 2 % of the required load by use of the load cell.
i.Proof Load Testing of Productio n Soil Nails.
1.Purpose and Extent of Proof Load Testing. Load capacity proof load testing shall be performed on production nails to make sure that the actual installation of these nails is adequate to support the soil nail wall structure. Proof load test ing shall be performed on at least 5 % (1 in 20) of the production nails in each nail row or a minimum of 1 nail per row. Prior to soil nail installation on each row, the testing locations
570.06 Construction Requirements.
will be selected with the random number method outlined in ALDOT- 210. The Contractor shall proof load the soil nails selected by the Engineer. A verification test nail that acceptably passes the verification test shall not be considered equivalent to a proof load test nail and shall not be used in determining the number r equired proof load tests. Tension loads shall be applied to a proof load test nail in increasing increments. The movement of the nail due to the increasing load will be monitored. The load in the nail and the corresponding movement of the nail will be use d in evaluating the acceptability of the soil nails that are represented by the proof load test nail. Excessive movement of the nail due to the loading is evidence that the installed soil nails are inadequate to carry the load of the wall.
2.Submittal of Details for Proof Load Testing. The Contractor shall submit the details of the proof load testing apparatus. The Engineer will review the submittal for completeness. The requirement for this submittal is given with the requirements for the submittal of th e details of the wall. The testing shall not begin until the Engineer informs the Contractor that the submittal is complete. Most of the testing equipment should be the same, or be very similar to the equipment required for the load capacity verification t ests.
3.Required Strength of Nail Grout and Shotcrete prior to Proof Load Testing. Proof load testing shall not be performed until the nail grout and shotcrete have reached the strengths required for the grout and shotcrete when performing a load capacity verification test.
4.Bonded and Temporary Unbonded Lengths of Proof Load Test Nails. Proof load test nails shall have both bonded and temporary unbonded lengths. The bonded length of the nail shall be grouted prior to testing. The bonded length s hall be determined based on the production nail bar grade and size and the theoretical pullout resistance of the nail. The bonded length shall not be less than 10 feet for soil nails that are 13 feet long and longer. The bonded length may be less than 10 f eet for soil nails that are shorter than 13 feet long. The temporary unbonded length shall not be less than 3 feet unless otherwise approved by the Engineer.
5.Allowable Load on Bar of Proof Test Nail. The allowable tensile stress during testing shall no t be greater than 90 % of the yield strength for Grade 60 and Grade 75 bars, or 80 % of the ultimate strength for Grade 150 bars.
6.Determination of the Maximum Bonded Length of a Proof Load Test Nail. A maximum bonded length shall be constructed for the proof load test of a production soil nail. The maximum bonded length shall first be calculated based on the strength of the production soil nail bar and the pullout resistance of the soil or rock. The required test load shall then be calculated based on t he bonded length of the test nail and the pullout resistance. If the maximum bonded length from the initial calculation is less than 10 feet and the bar is 13 feet long or longer the required maximum bond length shall be 10 feet. If the maximum bonded leng th from the initial calculation is less than 10 feet and the bar is shorter than 13 feet long, the required maximum bond length shall be the length determined from the calculation. The required test load shall then be calculated based on the bonded length of the test nail and the pullout resistance of the bonded length. The following equation shall be used for determining the proof test nail maximum bonded length: L BP= C f Y AS/ 1.5 Q d, or 120 inches if the bar is 13 feet long or longer; • LBP= Maximum Proof Load Test Nail Bonded Length (inches); • C = 0.9 for Grade 60 and 75 bars and 0.8 for Grade 150 bars; • fY = Bar Yield or Ultimate Stress (pounds per square inch); (Note: fy = 60,900 psi, 75,400 psi and 150,100 psi respectively for Grade 60, 75 and 150 bars) ; • AS = Bar Steel Area (square inches); • 1.5 = Pullout resistance safety factor; • Qd = Allowable pullout resistance (pounds per inch) of grouted nail.
7.Determination of the Proof Test Load. The following equation shall be used for determining the Verificatio n Test Load (VTL): PTL = L BV X Q d; • PTL = Proof Test Load (pounds).
570.06 Construction Requirements.
8.Proof Loading of a Test Nail. Proof tests shall be performed by incrementally loading the proof load test nail to a maximum test load of 150 percent of the Proof Test Load (PTL) in ac cordance with the following loading schedule. The nail movement shall be recorded at the end of each load increment. At load increments other than the maximum load, the load shall be held long enough to obtain a stable reading. PROOF TEST LOADING SCHEDULE LOAD HOLD TIME AL = 0.05 PTL Max. Until stable 0.25 PTL Until stable 0.50 PTL Until stable 0.75 PTL Until stable 1.00 PTL Until stable 1.25 PTL Until stable 1.50 PTL (Max. Test Load) See Below (Creep Test) The alignment load (AL) should be the minimum load required to align the testing apparatus and should not exceed 5 percent of the Proof Test Load (PTL). Dial gauges for measuring the movement of the test nail shall be set to “zero” after the alignment load has been applied. All load increments shall be maintained within 5 percent of the intended load. Depending on performance, either 10 minute or 60 minute loading duration creep tests shall be performed at the maximum test load (1.50 PTL). The creep test period shall start as soo n as the maximum test load is applied and the nail movement shall be measured and recorded at 1 minutes, 2, 3, 5, 6, and 10 minutes. Where the nail movement between 1 minute and 10 minutes exceeds 0.04 inches, the maximum test load shall be maintained an additional 50 minutes and movements shall be recorded at 20 minutes, 30, 50, and 60, minutes.
j.Acceptance Criteria for Verification and Proof Load Testing.
1.Verification Test Acceptance Criteria for Creep Test. The test is acceptable when the total creep movement is less than 0.08 inches per log cycle of time between the 6 and 60 minute readings measured during creep testing and the creep rate is linear or decreasing throughout the creep test load hold period.
2.Proof Load Test Acceptance Criteria for Creep Test. The test is acceptable when a total creep movement of less than 0.04 inches is measured between the 1 and 10 minute readings or a total creep movement of less than 0.08 inches is measured between the 6 and 60 minute readings and the creep rate is linear or decreasing throughout the creep test load hold period.
3.Verification and Proof Load Test Acceptance Criteria for Elongation. The test is acceptable when the total measured movement at the maximum test load exceeds 80 percent of the theoretical elastic elongation of the test nail unbonded length.
4.Verification and Proof Load Test Failure due to Pullout. The test is acceptable when a pullout failure does not occur at the maximum test load. Pullout failure shall be defined as the loa d at which attempts to further increase the test load simply result in continued pullout movement of the test nail. The pullout failure load shall be recorded as part of the test data.
k.Criteria for Incorporating Proof Load Tested Nails as Production Na ils. Proof loaded test nails that meet the acceptance criteria may be incorporated as production nails if: • The unbonded length of the test nail drill hole has not collapsed during testing; • The minimum required drill hole diameter has been maintained; • The s pecified corrosion protection is provided and; • The test nail length is equal to or greater than the scheduled production nail length. Proof loaded test nails meeting these requirements shall be completed by satisfactorily grouting up the unbonded test len gth. The Contractor shall be responsible for maintaining the temporary unbonded test length for subsequent grouting. If the unbonded test length of production proof load test nails cannot be satisfactorily grouted subsequent to testing, the proof test nail shall become sacrificial and shall be replaced with an additional production nail installed without extra compensation.
570.09 Temporary Soil Nail Walls.
l.Work Required to Address the Failure of a Load Verification Test. The Engineer will evaluate the results of each verification test . Propose installation methods which do not result in acceptable load verification tests will be rejected. The Contractor shall proposed alternative methods and shall install replacement verification test nails. Replacement test nails shall be installed a nd tested without compensation.
m.Required Work After Failure of a Proof Load Test. The Engineer may require the Contractor to replace some or all of the installed production nails between a failed proof load test nail and the adjacent passing proof test nail. Alternatively, the Engineer may require the installation and testing of additional proof test nails to verify that adjacent previously installed production nails have sufficient load carrying capacity. Contractor modifications may include, but are not limited to; the installation of additional proof test nails; increasing the drill hole diameter to provide increased capacity; modifying the installation or grouting methods; reducing the production nail spacing from that shown on the Plans and instal ling more production nails at a reduced capacity; or installing longer production nails if sufficient right -of-way is available and the pullout capacity behind the failure surface controls the allowable nail design capacity. The nails may not be lengthene d beyond the temporary construction easement or the permanent right -of-way shown on the Plans. Installation and testing of additional proof load test nails or installation of additional or modified nails as a result of proof load test nail failure(s) shal l be done without compensation.
n.Records of Soil Nail Wall Construction. Records documenting the soil nail wall construction, including records of the installation and testing of soil nails, shall be produced and maintained in a manner acceptable to the Engineer. The Contractor shall provide the Engineer with copies of these records at the times designated by the Engineer.
570.07 As -Built Drawings and Revised Design Calculations.
The Contractor shall revise the Wall Construction Drawings when plan dimens ions are revised due to field conditions or for other reasons. Within 30 calendar days after completion of the work, the Contractor shall submit as- built drawings to the Engineer. The Contractor shall also provide revised design calculations signed by the Licensed Professional Engineer that sealed the submittal of the design of the wall.
570.08 Workmanship Warranty.
The soil nail contractor will warrant the stability and workmanship of the slope following the techniques specified in this special provision. The warranty shall be for a period of 5 years from date of acceptance of the work. The warranty shall not reduce or affect any separate warranty on materials or products as stated in this special provision. The warranty applies to all perils which may af fect the work, any area that becomes unstable, i.e., a failure within the modeled cross sections and potential failure planes, and the work of any subcontractor or vendor of the soil nail contractor. If an unstable condition occurs, then the soil nail con tractor shall repair all failures within 30 days of receipt of verbal or written notification by ALDOT. This warranty excludes acts of God and except as stated above, work of a third party that causes an unstable condition or damages the work performed by the soil nail contractor.
570.09 Temporary Soil Nail Walls.
Temporary Soil Nail Walls are those walls used for excavation shoring and which have a service life less than 18 months. Temporary soil nail walls shall be designed and constructed as required herein, with the following exceptions: • Soil nail walls for temporary applications in non -aggressive environments can be designed with no corrosion protection except grout encapsulation of the bars. Centralizers on the bars at minimum 10 feet spacing are required. • An as -shot or rough -screeded finish is satisfactory. • The minimum shotcrete thickness shall be at least the design thickness less 0.5 inches. • Minimum reinforcing cover shall be 2 inches. • No contraction joints or special construction jo ints are required. • Except for protection from freezing, no special protection or curing of the shotcrete is required.
570.10 Method of Measurement.
570.10 Method of Measurement.
The Soil Nail Wall will be measured in units of square yards of the shotcrete face of the wall. Measurement will not be made outside of the limits (vertical and horizontal) of the shotcrete face of the wall shown on the plans or designated by the Engineer. Excavation for Construction of Soil Nail Wall will be measured as the theoretical volume in cubic yards wit hin the structure excavation limits shown on the Plans. This will be the excavation volume within the zone measured from the top of the shotcrete wall facing to the bottom of the wall. There will be no measurement of the excavation beyond the limits of exc avation shown on the Plans.
570.11 Basis of Payment.
a.Unit Price Coverage. The Soil Nail Wall will be paid for at the contract unit price. This payment shall be full compensation for all submittals, labor, equipment, tools, materials, material tests, f ield tests and incidentals necessary to acceptably fabricate and test the wall components and construct the wall. This shall also be full compensation for furnishing and placing the reinforcing steel for the wall facing. The contract unit price for Excava tion for Soil Nail Wall shall be full compensation for all equipment, tools and labor required for the excavation and disposal of the excavated materials.
b.Payment will be made under Item No.: 570-A Soil Nail Wall – per square yard 570-B Excavat ion for Soil Nail Wall – per cubic yard 570-C Temporary Soil Nail Wall – per square yard SECTION 571 SHOTCRETE
571.01 Description.
This work shall consist of furnishing and placing one or more courses of shotcrete and reinforcing steel on a prepared surface. The shotcrete shall be a concrete mixture that is pneumatically projected at high velocity onto the surface.
571.02 Materials.
a.General. Materials shall conform to the requirements given in Division 800, Material s. Specific reference is made to applicable portions of the following Sections: Section 801 Coarse Aggregate Section 802 Fine Aggregates Section 806 Mineral Admixtures Section 807 Water Section 808 Air Entraining Admixtures Section 809 Chemical Admixtures for Concrete Section 815 Cement Section 835 Steel Reinforcement Section 852 Underdrain Pipe Materials
b.Aggregates. When coarse aggregates are used, the coarse and fine aggregate shall be weighed separately to avoid segregati on. Oversize pieces of aggregate shall be removed by screening. The combined aggregates shall meet one of the following gradations:
Source: Alabama Standard Specifications for Highway Construction, 2022 Edition. Pages 432–448 of 934.