546.01 Description.
b.Trench Excavation. Excavation shall be kept as nearly as possible to the minimum width, depth, and length shown on the plans.
c.Drain Placement and Protection . Precast drains shall be installed to the li nes and grades shown on the plans or as directed by the Engineer. The trench slot shall be protected during installation by a removable wood strip, heavy duty tape, or other suitable material, affixed to the slot to prevent infiltration of material into t he drain. After finishing the surface, the protective covering shall be removed and any debris that entered the trench shall be removed.
c.Concrete Placement . The furnishing and placement of the concrete shall be in accordance with the requirements given in Section 501. The prefabricated trench drain components shall be supported or held in place in such a manner as to permit flow of the concrete backfill material around the drain. The concrete encasement adjacent and beneath the drain channel shall be a minimum thickness of 6 inches (150 mm}. Drain channels shall be positioned in the excavated trench so that, when finished, the surrounding concrete backfill will encase the channel. Concrete backfill shall be placed in the trench against undisturbed materi al at the sides and bottom of the trench and in a manner that will prevent floating or shifting of the trench drain components and voids in, or segregation of, the concrete. Where necessary, earth plugs shall be constructed and compacted at the ends of the planned concrete backfill to contain the concrete within the trench. Concrete shall be finished flush with adjacent surfacing. The surface of the concrete shall be textured with a broom or burlap drag to produce a durable skid- resistant surface. Under no circumstances shall any portion of the trench drain slot extend above the paving material or curb and gutter section.
539.04 Method of Measurement.
The trench drain will be measured in linear feet {meters} along the top of the drain. Connections to other structures (i.e. elbows, pipe, joints, etc.) will not be measured for payment unless shown otherwise on the plans. Excavation and backfill will not be measured for payment.
539.05 Basis of Payment.
a.Unit Price Coverage . Trench Drain will be paid for at the contract unit price, which shall be full compensation for fabricating, furnishing and installing the trench drain components. It shall also be full compensation for furnishing and installing connections to other structures, for all concrete, excavat ion, backfill, satisfactory disposal of surplus materials, and for all equipment, tools, labor, and incidentals necessary to complete the work.
b.Payment will be made under Item No .: 539-A ___ inch {mm} Trench Drain - per linear foot {meter} MICRO PILES
546.01 Description.
This Section shall cover the work of constructing, furnishing, and installing micropiles as shown on the contract plans, approved working drawings, and as specified herein. The Contractor shall be responsible for furnishing all design, materials, products, accessories, tools, equipment, services, transportation, labor and supervision, and manufacturing techniques required for design, installation, and testing of micropiles and top attachments. The Contractor shall select micropile type, size, micropile top attachment, and construction methods. The Contractor shall estimate the ground to grout bond value and determine the required
546.02 Materials.
bond length. The Contractor shall install a system that will provide the load capacities shown in the working drawings.
546.02 Materials.
a.General. Handling, storage, and control of materials shall comply with appropriate portions of Section 106. All materials shall conform to the requirements set forth in Division 800, Materials. Specific reference is made to applicable portions of the Specifications: Section 802 – Fine Aggregate
Article 807 — 01 – Water
b.Cement. Cement shall be Type I, Type II, or Type I L and shall meet the requirements of Section 815.
c.Steel Reinforcement. Reinforcing steel shall be Grade 75, and shall meet the requirements given in AASHTO M31 and Section 835. Bars shall be threaded a minimum of six inches or continuous spiral deformed bars designed for coupling. Bar couplers, if required shall develop the ultimate tensile strength of the bars without any evidence of failure.
d.Pipe/Casings. Permanent steel casting/pipe shall meet the tensile requirements of American Petroleum Institu te (API) N80 as used in the design submittal, having the diameter and minimum wall thickness shown in the working drawings. Micropile casing shall be smooth, non -corrugated, clean, watertight steel, and threaded to develop the required design strength of t he casing section. Welded splices will not be allowed. Casings shall be new the use of used casings will not be allowed. The Contractor shall provide documentation stating the origin in accordance with the requirements given in Subarticle 106.01(a), pipe description, and quantity of pipe/casing delivered to the project. Additionally, the Contractor shall submit a minimum of two representative coupon tests from an independent testing laboratory or mill certifications, for each load of pipe/c asing delivered for use on the project.
e.Plates and Shapes. Structural steel plates and shapes for micropile top attachments shall conform to ASTM A36 or ASTM A572 Grade 50 and Section 836.
f.Centralizers. Centralizers shall be installed to align the reinforcing bars in the micropile. Centralizers shall be manufactured from Schedule 40 PVC pipe, steel or other material that will not be detrimental to the performance of the micropile. The use of wood centralizers will not be allowed. Centralizers shall have a means for being securely attached to the reinforcing bar. The centralizers shall be sized to position the reinforcing bar within 1 inch of the center of the micropile to allow tremie pipe insertion to the bottom of the micropile and to allow free fl ow of grout.
g.Grout. The grout shall be a neat cement or sand/cement grout. The Contractor shall submit the proposed grout mix design to the Materials 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 2000 psi at 3 days, and a minimum compressive strength of 4000 psi at 28 days. Compressive strength shall be tested in accordanc e 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 grout mix that have been completed within one year of the start of work, and that have been pe rformed by an ALDOT approved testing laboratory, may be submitted for verification of the mix design.
546.03 Micropile Design and Submittals
546.03 Micropile Design and Submittals
a.Contractor Qualifications. The micropile Contractor shall be experienced in the design, construction, and load testing of micropiles and have at least five years of experience and constructed at least three projects of similar size and capacity to those required by this project. The Contractor shall have previous micropile drilling and grouting experience in soil/r ock similar to project conditions. The Contractor shall submit construction details, structural details and load test results for at least three previous successful micropile load tests from different projects of similar scope to this project. The Contrac tor shall assign a supervising project manager with experience on at least three projects of similar scope to this project completed over the past five years to supervise the work performed. The Contractor shall not use consultants or manufacturers’ repres entatives to satisfy the supervising manager requirements of this Section. The on -site foremen and drill rig operators shall also have experience on at least three projects over the past five years installing micropiles/pre -bored pile retaining wall struct ures.
b.Micropile Design. The micropiles shall be designed in accordance with the guidelines given in FHWA NHI -05-039 “Micropile Design and Construction Reference Manual”, by a Professional Engineer licensed in the State of Alabama, with experience in th e design of at least three successfully completed micropile projects over the past five years. The overall length of a micropile will be selected such that the required capacity is developed by skin friction between grout and rock socket over a suitable continuous length in competent rock. A factor of safety of 2.0 shall be used when calculating the allowable geotechni cal capacity of the bond zone. The micropile top attachment shall effectively distribute the design load to the concrete footing such that the concrete bearing stress does not exceed American Concrete Institute (ACI) Building Code and the bendi ng stress in the steel plates does not exceed American Institute of Steel Construction (AISC) allowable stresses for steel members. The geotechni cal capacity shall not rely on bond from clay soils or fractured weathered rock layers, intermitt ent rock layers with clay seams, rock under lain by voids or boulders above the competent rock. The Contractor may indepen dently conduct any geotechnical investigation necessary to provide a proper design and installation of the system. Any additional investigation needed during construction to define foundation conditions will be at no additional cost to the Department . If a manmade obstruction is encountered during installation of a micropile that prevents the advancing of the micropile; the micropile shall be abandoned and filled with grout. The Contractor and ALDOT shall determine an acceptable alternative plan. Contractor shall be paid for abandoned holes that are due to no fault of the Contractor.
c.Submittal of Micropile Design, Details, and Installation Plan
1.Completed Project Reference and Personnel Lists At least 30 calendar days before the planned start of micropile construction, the Contractor shall submit 5 copies of the completed project reference list and a personnel list. The project reference list shall include a brief project description with the owner’s name and current phone number and load test reports. Th e personnel list shall identify the micropile system design engineer (if applicable), supervising project engineer, drill rig operators, and on - site foremen to be assigned to the project. The personnel list shall contain a summary of each individual’s expe rience and be complete enough for the Engineer to determine whether each individual satisfies the required qualifications. The Engineer will approve or reject the Contractor’s qualifications within 15 calendar days after receipt of a complete submission. Additional time required due to incomplete or unacceptable submittals will not be cause for time extension or impact or delay claims. All costs associated with incomplete or unacceptable submittals shall be borne by the Contractor. Work shall not be start ed, nor materials ordered, until the Engineer’s written approval of the Contractor’s experience qualifications is given. The Engineer may suspend the work if the Contractor uses non- approved personnel. If work is suspended, the Contractor shall be fully liable for all resulting costs and no adjustment in contract time will result from the suspension.
2.Working Drawings
546.03 Micropile Design and Submittals
The Contractor shall submit working drawings and relevant structural design calculations for the micropile system to the Bridge Engineer for review prior to the start of any work. A Registered Professional Engineer in the State of Alabama shall stamp the submittal. The following information shall be included with the working drawings and design calculations submittal(s): • A written summary report which describes the overall micropile design. • Micropile details for each micropile type (load) showing: o Micropile design load. o Elevation view showing type and size of permanent casing and reinforcing steel, o Minimum total bond length o Total micropile length. o Micropile top attachment. • Micropile numbering system for records. • Grouting plan and grout mix designs, including: o Procedur e for placing the grout, and methods for accurately monitoring and rec ording the grout depth and grout volume. o The Contractor shall clearly identify the minimum specified grout compressive strength at which load tests shall be performed. o Estimated curing time for grout to achieve specified strength. o Procedur e and equipment for Contractor ’s monitoring of grout quality and volume installed. • Detailed, step-by-step description of the construction procedur e and sequence, including personnel and a qu ality control plan . This step-by-step procedur e shall be shown on the working drawings in sufficient detail to allow monitoring of the construction and quality of the micropiles. • Information on headroom and space requirements for installation equipment that verify that the proposed equipment can perform at the site. • Details for plumb hole drilling. • Details for centralizers. • Pipe and reinforcement splice type and locations. • Details of the load testing apparatus for verification and proof loading tests. • Calibration documentation of the hydraulic jack(s) to be used for load testing. • Details for exploratory drilling of micropiles with rock sockets The Engineer will review the design calculations, working drawings, and material requirements, and construction procedure for conformanc e to the plans and specifications. The Engineer will not approve these parts of the submittal but will review them to ensure that they are sufficiently complete to allow the construction of the micropiles. The Engineer will return the submittal for correct ions, distribute the submittal for construction inspection, or contact the Contractor to establish a mutually agreeable date and time for a meeting to discuss the submittal. The Contractor will be notified of changes in the submittal deemed necessary withi n seven days after the meeting. Micropile construction shall not begin until the submittal has been distributed for construction inspection and the Engineer informs the Contractor in writing that the proposed working drawings, design calculations, material requirements, and micropile construction procedure are complete. Distribution of the submittal for construction inspection shall not relieve the Contractor of the responsibility to satisfactorily complete the work as detailed on the plans and in the speci fications. Any proposed modification of the construction procedure during construction shall be submitted to the Bridge Engineer for review and distribution.
d.Construction Site Survey. The Contractor shall revie w the available subsurface information and visit the site to assess the site conditions, equipment access conditions, and location of the existing structures and above ground facilities.
546.04 Construction Requirements.
The Contractor is responsible for field locating and verifying the location of all utilities shown on the plans prior to beginning any work. The Contractor shall not interrupt any existing utility services unless authorized in writing. The Contractor shall notify the appropriate parties of any utility locations different from those on the provided plans that may require modification to the micropile locations or design modifications.
e.Pre -Construction Meeting. A pre- construction meeting will be scheduled by the Engineer and held prior to the start of micropile construction. The Engineer, Geotechnical Engineer, Area Materials Engineer, Bridge Engineer, Construction Engineer, prime Contractor, micropile specialty Contractor, micropile design engineer, excavation Contractor and geotechnical instrumentation specialist (if applicable) shall attend the meeting. Attendance is mandatory. The pre -construction meeting will be conducted to clarify the construction requirements for the work, to coordinate the construction schedule and activities, and to identify contractual relationships and delineation of responsibilities amongst the prime Contractor and the various Subcontractors —specifically those pertaining to excavation for micropile structures, anticipated subsurface conditions, micropile installation and testing, micropile structure survey contr ol and site drainage control.
546.04 Construction Requirements.
a.Installation. The contractor shall install the micropile using core drilling, rotary drilling, percussion drilling, auger drilling, driven casing or other acceptable means unless otherwise directed. Micropiles can be installed in the drilled hole after drilling or can be advanced by the drill.
1.Exploratory Drilling of Micropiles with Rock Sockets When the micropiles design capacity is developed from a rock socket, the contractor shall perform exploratory drilling or probing to determine the location, extent, and quality of the rock in which the socket will be constructed. A minimum of 30% of the micropile locations in each footing shall be drilled or probed. The drilling/probing l ocations shall be selected such that three (3) subsurface profiles are generated transverse to the long dimension of the footing and two (2) subsurface profiles are generated transverse to the short dimension of the footing. The drilling or probing shall extend into competent rock a minimum of 1.5 times the length of the proposed micropile design rock socket. Production micropile drilling and installation for a given footing shall not begin until the results of this exploration are submitted and approved by the Engineer. This submittal shall include the following: • A plan view showing all micropiles in the footing with corresponding micropile numbers and locations of exploratory borings. • Drill logs indicating the existing ground elevation at the time of drill ing, micropile number, bottom of footing elevation, elevations of soil and rock layers, estimate of rock quality, and proposed micropile tip elevations. Subsurface information contained in the contract plans may be used in lieu of exploratory drilling for individual micropiles with prior approval of the Materials and Tests Engineer.
2.Drilling and Grouting All foreign material dislodged or drawn into the hole during construction of the micropiles shall be removed. Centralizers shall be used when installing central bar reinforcement. The contractor shall allow free flow of the grout and provide a positive means of support for maintaining the position of the casing and reinforcement until the grout has set. Reinforcement shall be lowered in the stabilized ho le. Reinforcement shall not be forced or driven into the hole. The Contractor shall dispose of cuttings, construction debris, and spilled or wasted grout in accordance with the Plans and federal, state and local laws. The grout shall be mixed to produce a uniform mixture free of lumps and undispersed cement. The grout pump shall be equipped with a pressure gauge to monitor grout pressures. Provide a pressure gauge capable of measuring pressure of at least 150 psi or twice the actual grout pressures used, whichever is greater. Use grouting equipment capable of pumping the grout in one continuous operation. Continuously agitate the mixed grout during pumping operations. The grout shall be injected from the lowest point of the drilled borehole and filled wit hout voids to the top of the micropile. The grout may be pumped through grout tubes, casing, hollow - stem-augers or drill rods.
546.04 Construction Requirements.
The quantity of the grout and the grout pressures shall be recorded. The contractor shall control the grout pressures to prevent excessive heave but shall fill the entire micropile with grout. Grout test specimens shall be made on production grout to ensure that the grout meets the requirements of Subarticle 546.02(g). The grout test specimens shall be molded and tested in accordan ce with the requirements given in AASHTO T 106. The Contractor’s testing technicians shall clearly label each grout cube test specimen and identify the micropiles associated/represented by each set of specimens. A set of tests specimens is comprised of three grout cubes. The requirements for grout testing are as follows:
a.Batch Grouting If small batch grouting operations are used a minimum of three sets of grout test specimens shall be created for each batch of micropile grout produced. One set of test specimens shall be designated for three -day compressive strength testing and one set shall be designated for 28 -day compressive strength testing. One set of test specimens shall be given to the Engineer for transport to the Department Laboratory for verifi cation testing.
b.Continuous Grouting If continuous grouting operations are used a minimum of three sets of grout test specimens shall be created for every 30 cubic yards or portion thereof of mircopile grout produced One set of test specimens shall be desig nated for three -day compressive strength testing and one set shall be designated for 28 -day compressive strength testing. One set of test specimens shall be given to the Engineer for transport to the Department Laboratory for verification testing. The Dep artment will perform random verification testing for 28 -day compressive strength on a frequency of one test for every 5 batches for batch grouting operations or one test for every 150 cubic yards or fraction thereof for continuous grouting operations. The test verification sample will be selected as outlined in ALDOT -210 “Selecting Samples By The Random Numbers Method”. The Department will test the remaining four samples in the event of a low break.
b.Installation and Post Construction Records. The Contractor shall maintain an independent record of all field installation activities. An ALDOT Representative shall also maintain an independent record of all field installation activities. At the end of each day; the Contractor and the ALDOT Representative sh all reconcile and agree upon the quantities installed. A log for each micropile shall be created and signed by a representative of the Contractor and ALDOT. The micropile records shall be submitted to the Project Manager within 48 hours after installation is completed for each micropile. The records shall include the following information: • Micropile drilling duration. • Final tip elevation. • Total micropile length. • Description of unusual installation behavior or conditions. • Grout quantities pumped. • Grout test specimen compressive strength results. • Micropile materials and dimensions. Post construction records shall be submitted to the Project Manager wi thin 30 calendar days after completion of work and shall include the following : • As-built drawing showing locations of the micropiles and length. • Detailed drilling records. • Grouting records indicating the cement type and quantity injected.
c.Performance and Testing. The Contractor shall perform both load capacity verification testing prior to the installation of production micropiles and proof load testing of designated production micropiles. Proof load tests shall be performed on production micropiles at locations selected by the Project Manager. No load tests shall be performed before the grout h as reached the minimum specified compressive strength. All load tests shall be performed with a jack calibrated in accordance with ALDOT- 358 and Subitem 505.03(g)1d.
1.Verification Testing of Test Pile. The contractor shall install a minimum of one (1) no n-production test pile for performance verification load testing outside of the proposed footing at the location shown on the plans or
546.04 Co nstruction Requirements.
as designated by the Engineer. The test pile shall not be a production pile. The test pile shall be loaded to 200 percen t the design load and evaluate the ultimate pile capacity to insure compliance with job performance requirements. The Contractor shall notify the Engineer one week before installing test micropile groups that are to be performance tested. No micropile, test pile or production piles shall be load tested until three days after grouting operations are complete. Load tests shall be performed in accordance with ASTM D1143, “Standard Test Methods for Deep Foundations Under Static Axial Compressive Load”, using Pr ocedure A – Quick Test. The axial compressive load shall be applied with a calibrated hydraulic jack. Apply the test load in increments of 5% of the anticipated failure load to maximum of a 200 percent of the foundation load shown on the Bridge Layout. Add load increments until reaching a failure load, but do not exceed the maximum testing load (200% of the foundation load). During each load interval, maintain load increments for 5 min and record test readings taken at 0.5, 1, 2 and 4 min after completing the application of each load increment. Use the same time interval for all loading increments through the test. Creep tests shall be performed at the test interval equal to 130 percent of the design load. Remove the load in six approximately equal increment s. Keep the load constant for 5 min using the same time intervals for all unloading decrements. Record test readings taken at 1 and 4 min after completing each load decrements. Take and record readings at 1, 4, 8 and 15 min after removing all loads. Refer to a constant elevation benchmark for readings of settlements and rebounds. Record them to 0.01 in. for each increment or decrement of load. Test piles will be considered acceptable if results meet the following criteria: • No failure occurs. • The ultimate pi le capacity from the load test is not less than 200 percent of its design load. • The measured total pile head movement for the required load hold at 130 percent of the design load does not exceed 0.04 inches between one and five minutes, the micropile shall be considered acceptable with respect to creep. For verification load tests where the measured total movement exceeds this criteria, the load shall be held for an additional 55 minutes. If the measured total movement over this additional time period does not exceed 0.08 inches between six and 60 minutes, the micropile shall be considered acceptable with respect to creep. If the test pile fails, the contractor shall modify the design and/or the construction procedure and install and test another pile at no additional expense to the Department. Any design modifications that require changes to the micropile type or to the structure shall be submitted in writing to the Bridge Engineer for review and acceptance. Any micropile production price increases due to design modifications and/or changes in the construction procedure shall be incurred by the Contractor.
2.Proof Load Testing of Production Micropiles. Load capacity proof load testing shall be performed on production micropiles to ensure that the Contractor ’s construction procedure has remained constant and that the micropiles have not been placed in a soil zone not represented by the test pile verification testing. Proof load testing shall be performed on a minimum of five percent (1 in 20) of the productio n micropiles with a minimum of one proof load test per footing. The Engineer will randomly select the micropile locations for testing as outlined in ALDOT- 210. Proof load test shall be performed as described in Item 546.04(c)1. except that micropiles shall be tested to a maximum load of 130 percent of the design load and the test shall be performed in accordance with the requirements given in ASTM D3689, “Standard Test Methods for Deep Foundations Under Static Axial Tensile Load”, using Procedure A – Quick Test. A test pile that acceptably passes the verification test shall not be considered equivalent to a proof load test micropile and shall not be used in determining the number required proof load tests. Proof load tests shall be considered acceptable if results meet the following criteria: • No pull out failure occurs at or before the maximum load. Pullout failure is defined as the load at which attempts to further increase the test load result in continued pullout movement of the micropile.
546.05 Method of Measurement.
• The measured tot al pile head movement for the required load hold at 130 percent of the design load does not exceed 0.04 inches between one and five minutes, the micropile shall be considered acceptable with respect to creep. For verification load tests where the measured total movement exceeds this criteria, the load shall be held for an additional 55 minutes. If the measured total movement over this additional time period does not exceed 0.08 inches between six and sixty minutes, the micropile shall be considered acceptab le with respect to creep. If a proof load test on a production pile fails, the Contractor will be directed to proof test another nearby micropile. The failed micropile test will not be considered for the minimum five percent requirement for proof load test ing of production micropiles. For failed micropiles and further construction of other micropiles, the Contractor shall modify the design, the construction procedure, or both. Modifications may include installing replacement micropiles, incorporating additi onal micropiles of reduced load capacities, modifying installation methods, increasing the bond length, or changing the micropile type. Any design modifications that require changes the micropile type or to the structure shall be submitted in writing to th e Bridge Engineer for review and acceptance. Any micropile production price increases due to design modifications and/or changes in the construction procedure shall be incurred by the Contractor.
3.Allowable Tolerances. • Centerline of piling shall not be m ore than two inches from the indicated plan position. • Micropile alignment shall be within two percent of design alignment. • Top elevation of micropile shall be within two inches of the design elevation. • Centerline of reinforcing steel shall not be more than 0.75 inches from the indicated horizontal location. • The length of micropiles/depth of the socket shall not exceed 20 percent of the design length without written approval from the Engineer. Failure to obtain written approval may result in the rejectio n of the micropile.
546.05 Method of Measurement.
a.Micropiles. Measurement will be made as follows for the quantity, as specified or directed by the Engineer: Micropiles will be measured in linear feet, installed, and accepted. The accepted length of micropiles will be no more than 20 percent of the design length without written approval from the Engineer.
b.Verification Load Test Pile. The verification test micropile installed as directed by the plans and these Specifications, will be measured complete and in place. The Verification test micropile will not be included in the measurement of the linear feet of production piles. No measurement or direct payment will be made for test pile cut -offs. Verification test micropiles will be measured per each.
c.Proof Load Testing. Micropile Proof Load Tests will be measured per each.
546.06 Basis of Payment.
a.Unit Price Coverage. The contract unit price paid for mi cropile includes full compensation for designing and furnishing all labor, materials, tools, equipment, and incidentals, and for doing all the work involved in constructing micropiles, including casings, grout, reinforcement, cutting tips, drill bits, pile anchorage, and disposing of materials resulting from pile installation, complete in place, as shown on the plans, as specified in this specification and as directed by the Engineer. No payment will be made for micropiles that are damaged either during ins tallation or after the micropiles are complete in place. No payment will be made for additional excavation, backfill, concrete, reinforcement, nor other costs incurred from footing enlargement resulting from replacing rejected micropiles. No payment will b e made for micropile lengths longer than the accepted micropile length unless written approval is obtained prior to the installation of the micropile. The contract unit price paid for micropile verification load test shall be full compensation for all labo r, materials, equipment, devices, submittals, and incidentals necessary to perform the
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 SECTION 570 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.
Source: Alabama Standard Specifications for Highway Construction, 2022 Edition. Pages 424–431 of 934.