Retaining Walls Art. 522.03 SECTION 522. RETAINING WALLS
522.01 Description. This work shall consist of furnishing and constructing the
retaining wall system(s), as specified to the lines, grades, and dimensions shown on the plans and as directed by the Engineer. This work also includes the preparation of design computations and shop drawings when required for the various retaining walls specified herein.
522.02 Materials. Materials shall be according to the following.
Item Article/Section
a.Structural Steel .................................................................................. 1006.04
b.Steel Casing ...................................................................................... 1006.05
c.Steel Piling ......................................................................................... 1006.05
d.Sheet Piling (Note 1) ...................................................................... 1006.05(c)
e.Steel Soil Reinforcing for Retaining Walls ......................................... 1006.21
f.Structural Timber ............................................................................... 1007.03
g.Controlled Low Strength Material (CLSM) .............................................. 1019
h.Portland Cement Concrete (Note 2) ........................................................ 1020
i.Fine Aggregate for Select Fill ............................................................ 1003.07
j.Fine Aggregate for Porous Granular Embankment ............................ 1003.04
k.Coarse Aggregate for Select Fill ........................................................ 1004.06
l.Coarse Aggregate for Porous Granular Embankment ....................... 1004.05
m.Coarse Aggregate for Leveling Pads ...................................................... 1004
n.Geotextile Filter Material for MSE and Modular Retaining Walls ....... 1080.05
o.Geosynthetic Soil Reinforcement for Retaining Walls ........................ 1080.06
p.Precast Concrete .................................................................................... 1042
q.Geotextile Reinforcement .............................................................. 1080.06(d)
r.Bearing Pads and Pins (Note 3) Note 1. For temporary sheet piling, the Contractor may utilize used material which shall be identifiable and in good condition, free of bends, and other structural defects. The minimum yield strength for temporary sheet piling shall be 38.5 ksi (265 MPa). The Contractor shall furnish a copy of the published sheet pile section properties and yield strength(s) to the Engineer for verification purposes. Note 2. Soldier pile encasement and concrete leveling pads shall be Class SI concrete. Note 3. The material for the bearing pads and pins shall be per the wall supplier’s specifications. CONSTRUCTION REQUIREMENTS
522.03 General. Structure excavation shall be according to Section 502, cast-
in-place concrete work shall be according to Section 503, structural steel fabrication and installation shall be according to Section 505, driving of piling shall be according to Section 512, and construction of drilled shafts shall be according to Section 516. Art. 522.04 Retaining Walls
522.04 Prequalified Retaining Wall Systems. The Department will maintain
a list of pre-qualified design concepts and/or proprietary products allowed for the following wall systems.
a.Mechanically Stabilized Earth (MSE) Retaining Walls
b.Temporary Mechanically Stabilized Earth (TMSE) Retaining Walls
c.Precast Modular Retaining Wall Systems These systems have been reviewed for structural feasibility and adequacy only. Presence on this list shall in no case relieve the Contractor of the site specific design or QC/QA requirements stated herein.
522.05 Submittals. Submittals shall include all shop drawings and when
required design computations. The submittals shall address all details, dimensions, quantities, general notes, and cross sections necessary to construct the retaining wall. The submittal shall be submitted to the Engineer for review and approval no later than 90 days prior to construction of the retaining wall. Approval shall be contingent upon acceptance by the utilities and/or railroad companies involved. When design computations are required, both the computations and the shop drawings shall be prepared and sealed by an Illinois Licensed Structural Engineer. All designs shall be according to the AASHTO design code specified on the plans, except as modified herein. Shop drawings shall be prepared according to
Article 1042 — 03(b).
522.06 Sheet Piling. The Contractor shall furnish sheet piling with a
published section modulus which meets or exceeds the required section modulus specified on the plans or in the approved design. The Contractor shall drive the sheeting to the tip elevation(s) specified on the plans. The Engineer’s approval will be required prior to driving any sheet piling. All driven sheeting not approved by the Engineer shall be removed at the Contractor’s expense. The sheet piling shall be driven, at a minimum, to the tip elevation(s) specified, or according to the Contractor’s approved design for sheet piling, prior to commencing any related construction. If unable to reach the minimum tip elevation, the adequacy of the sheet piling design will require re-evaluation by the Department prior to allowing construction adjacent to the sheet piling in question. Sheet piling shall be installed according to the following.
a.Temporary Sheet Piling. The Contractor may propose an alternate design for supporting the excavation, subject to the approval of the Engineer, and provided it is at no additional cost to the Department. Alternate designs shall be according to the requirements of Article 522.07. The Contractor shall not excavate below the maximum excavation line shown on the plans without the prior approval of the Engineer. The sheet piling shall remain in place until the Engineer determines it is no longer required, at which time the sheet piling shall be removed. When allowed, the Contractor may elect to cut off a portion of the sheet piling, Retaining Walls Art. 522.08 leaving the remainder in place. The remaining sheet piling shall be a minimum of 12 in. (300 mm) below the finished grade.
b.Permanent Sheet Piling. The selection of the sheet pile section shall not relieve the Contractor of the responsibility to satisfy all details including minimum clearances, cover, reinforcement, shear stud locations, interlocking, and field cutting. Any modifications of the plans to accommodate the Contractor’s selection shall be at no additional cost to the Department and will be subject to the approval of the Engineer.
522.07 Temporary Soil Retention System. The temporary soil retention
system shall be designed by the Contractor to retain the exposed surface area specified on the plans as a minimum, or the exposed surface area needed by the Contractor to complete the work. Design computations and shop drawings shall be submitted according to Article 522.05. The soil retention system shall be installed at the locations shown in the plans according to the Contractor’s approved design prior to commencing any related excavation. If unable to install the temporary soil retention system as specified in the approved design, the Contractor shall re-evaluate the adequacy of the design. Any re-evaluation shall be submitted to the Engineer for approval prior to commencing the excavation adjacent to the area in question. The Contractor shall not excavate below the maximum excavation line shown in the approved design without the prior approval of the Engineer. Temporary soil retention systems utilized for multiple stages of construction shall include any adjusting required to transition from one stage to the next as required. The retention system shall remain in place until the Engineer determines it is no longer required and shall be removed. When allowed, the Contractor may elect to cut off a portion of the retention system leaving the remainder in place. The remaining temporary soil retention system shall be removed to a depth which will not interfere with the new construction, and at a minimum, to a depth of 12 in. (300 mm) below the finished grade.
522.08 Soldier Pile Retaining Walls. Soldier pile wall may be specified as
either driven or drilled and set into position to the specified elevation(s). This work shall also include the furnishing and installation of the lagging.
a.Fabrication. The soldier pile is defined as the structural steel section(s) shown on the plans, including connecting plates used to join multiple sections. The types of soldier piles shall be defined as HP, W sections, or built-up sections. Built-up soldier piles shall require the submittal of shop drawings according to Article 522.05. The soldier pile shall be shop fabricated such that no field welding is required, except for splices. Cleaning and painting of all steel components, when specified, shall be as shown on the plans and performed according to Section 506.
b.Soldier Pile Installation. Soldier pile installation shall be according to the following.
1.Drilled Soldier Piles. The drilling methods used to maintain the shaft excavation during the various phases of shaft excavation and concrete Art. 522.08 Retaining Walls placement shall be according to the methods in Section 516 and appropriate for the site conditions encountered. The Contractor shall attach suitable bracing or supports to maintain the position of the soldier pile. The bracing or supports shall remain in place until the concrete for encasement has reached a minimum compressive strength of 1500 psi (10.35 MPa). If the type of soil or rock encountered is not similar to that shown in the subsurface exploration data, or if the top of rock encountered is below that estimated on the plans such that the soldier pile length above rock is increased by more than ten percent, the Engineer shall be notified to determine if any soldier pile design changes are required. When embedment in rock is indicated on the plans, the top of rock shall be defined according to Article 516.09 and modification to the length of a soldier pile may be required to satisfy the required embedment. The modification shall be made to the top of the soldier pile unless otherwise approved by the Engineer. When the top of rock encountered is above the estimated elevation indicated on the plans, the soldier piles shall be cut to the required length. If the top of rock encountered is below that estimated on the plans by less than ten percent of the pile length, the Contractor shall either furnish longer soldier piles or splice on additional length of soldier pile per Article 512.05(a) to satisfy the required embedment in rock. The soldier pile encasement concrete placement shall be made in a continuous manner from the bottom of the shaft excavation to the elevation indicated on the plans. Concrete shall be placed as soon as possible after the excavation is completed and the soldier pile is secured in the proper position. Uneven levels of concrete placed in front, behind, and on the sides of the soldier pile shall be minimized to prevent soldier pile movement, and to ensure complete encasement. Following the soldier pile encasement concrete placement, the remaining portion of the shaft excavation shall be backfilled with CLSM according to Section 593. CLSM secant lagging placement shall be placed as soon as practical after the shaft is cleared of excavated material.
2.Driven Soldier Piles. Piles shall be supplied and driven without splices unless approved by the Engineer. Soldier piles furnished with extra length shall be driven to the required tip elevation and cut to satisfy the top of pile elevation or driven past the required tip elevation to avoid cutting. Vibratory or impact hammers may be used to install the soldier piles. The Contractor may choose to install drilled soldier piles in lieu of driven soldier piles at no additional cost to the Department.
3.Construction Tolerances. Soldier pile installation shall satisfy the following construction tolerances.
a.The center of the soldier pile shall be within 2 in. (50 mm) of plan location in any direction at the top of the pile. Retaining Walls Art. 522.08
b.The out of vertical plumbness of the soldier pile shall not exceed 1/8 in./ft (10 mm/m).
c.The top of soldier pile shall be within ± 2 in. (± 50 mm) of plan elevation. Failure to meet these tolerances may require modifications to the wall up to and including removal and reinstallation of the affected portions of the wall.
c.Lagging. Permanent exposed lagging shall be according to the details on the plans. Temporary lagging shall be according to the details on the plans and may be either treated or untreated structural timber, precast concrete, or CLSM secant lagging. Timber or precast concrete lagging, installed below the original ground surface, shall be placed from the top down as the excavation proceeds. Lagging shown above grade shall be installed and backfilled against prior to installing any permanent facing to minimize post construction deflections. Over-excavation required to place the lagging behind the flanges of the soldier piles shall be the minimum necessary to install the lagging. Voids produced behind the lagging shall be filled with porous granular embankment, but the volume will not be measured for payment. When the plans require the Contractor to design the temporary lagging, the design shall be based on established practices published in FHWA or AASHTO documents considering lateral earth pressure, construction loading, all surcharge loads, and the lagging span length(s). Design computations shall be submitted according to Article 522.05. The nominal thickness of timber lagging shall not be less than 3 in. (75 mm) and shall satisfy the minimum tabulated unit stress in bending (Fb) of 1000 psi (6.9 MPa). When the nominal timber lagging thickness(s) and allowable stress are specified on the plans, the timber shall be rough cut or surfaced according to Article 1007.03. When precast lagging is specified to be used, shop drawings shall be submitted according to Article 522.05. The precast lagging shall be reinforced with a minimum of 0.31 sq in./ft (655 sq mm/m) of horizontal and vertical reinforcement per unit width of lagging with a minimum thickness of 3 in. (75 mm). The Contractor shall be responsible for the successful performance of the lagging system until the concrete facing is installed.
d.Geocomposite Wall Drain. When required, the geocomposite wall drain shall be installed according to Section 591, except that, in the case where a concrete facing is specified on the plans, the wall drain shall be installed on the concrete facing side of the lagging with the pervious (fabric) side of the drain installed to face the lagging. When a concrete facing is not specified on the plans, the pervious (fabric) side of the drain shall be installed to face the soil. In this case, the drain shall be installed in stages as the lagging is installed. The wall drain shall be placed in sections and spliced, or kept on a continuous roll, so that as each lagging is placed, the drain can be properly located as the excavation proceeds. Art. 522.09 Retaining Walls
522.09 Mechanically Stabilized Earth Retaining Walls and Temporary
Mechanically Stabilized Earth Retaining Walls. Mechanically stabilized earth (MSE) walls shall consist of a MSE wall design, concrete leveling pad, precast concrete face panels, a soil reinforcing system, select fill, concrete coping (when specified), and any other construction accessories necessary to construct the wall. Temporary mechanically stabilized earth (TMSE) walls shall consist of a TMSE wall design, sacrificial fascia, a soil reinforcing system, and select fill. The soil reinforcement shall have sufficient strength, quantity, and pullout resistance beyond the failure surface within the select fill, as required by design. The material, fabrication, and construction shall also meet the requirements specified by the supplier of the wall system selected by the Contractor. The options for MSE and TMSE wall systems shall be according to Article 522.04.
a.Design Criteria. Design computations and shop drawings shall be submitted according to Article 522.05. The Contractor shall be responsible for all internal stability aspects of the wall design and shall submit to the Engineer computations for each designed wall section. The Department will be responsible for the analysis of settlement, bearing capacity, and overall slope stability. The wall shall not be designed for seismic loading unless noted on the plans. For design purposes of the wall system, embankment placed behind the reinforced volume of select fill shall be assumed to have a unit weight of 120 lb/cu ft (1922 kg/cu m) and an effective friction angle of 30 degrees. External loads, such as those applied through structure foundations, from traffic or railroads, slope surcharge, etc., shall be accounted for in the internal stability design. The presence of all appurtenances behind, in front of, mounted upon, or passing through the wall volume such as drainage structures, utilities, structure foundation elements, or other items shall be accounted for in the internal stability design of the wall. The design of the soil reinforcing system shall be according to the applicable AASHTO LRFD Bridge Design Specifications for inextensible steel or extensible geosynthetic reinforcement criteria. The shop drawings shall show the limits of soil reinforcement and stations where changes in length and/or size of soil reinforcement occur. All details of the soil reinforcement placement around all appurtenances located behind, on top of, or passing through the soil reinforced wall volume such as parapets with anchorage slabs, coping, foundations, and utilities, etc., shall be addressed. Modifications to the design of these appurtenances to accommodate a particular system shall be submitted to the Engineer. The equivalent uniform applied service (unfactored) nominal bearing pressure shall be shown for each designed wall section.
1.MSE Walls. The reduced section of the soil reinforcing system shall be sized to allowable stress levels at the end of a 75-year design life. The design life for aluminizing shall be assumed to be 16 years. The corrosion protection for the balance of the design life shall be provided using a sacrificial steel thickness computed for all surfaces. Retaining Walls Art. 522.09 To prevent out of plane panel rotations, the soil reinforcement shall be connected to the standard full height panels at a minimum of two different elevations, vertically spaced between 15 and 30 in. (375 and 750 mm) apart. The panels shall be erected so that the horizontal panel joint line is discontinuous at every other panel. This shall be accomplished by alternating standard height and half height panel placement along the leveling pad. Panels above the lowest level shall be standard size, except as required to satisfy the top of exposed panel line shown on the plans. At locations where the plans specify a change of panel alignment creating an included angle of 150 degrees or less, precast corner joint elements will be required. This element shall separate the adjacent panels by creating a vertical joint secured by means of separate soil reinforcement. Isolation or slip joints, which are similar to corner joints in design and function, may be required to accommodate differential settlement at locations indicated on the plans or as recommended by the wall supplier. Wall panels with areas greater than 30 sq ft (2.8 sq m) may require additional slip joints to account for differential settlement. The maximum standard panel area shall not exceed 60 sq ft (5.6 sq m).
2.TMSE Walls. The reduced section of the soil reinforcing system shall be sized to allowable stress levels at the end of a 36-month design life. Steel soil reinforcement and sacrificial fascia for TMSE walls need only be sized using a sacrificial steel thickness for the design life specified. All soil reinforcement elements shall be directly connected to the sacrificial fascia and shall have a connection capacity equal to the pull out capacity based on the maximum tensile loading occurring in the soil reinforcement. The soil reinforcement’s maximum vertical center to center spacing shall be 20 in. (500 mm) and in the horizontal direction, the clear distance between the edges of one soil reinforcement to the next shall not exceed 30 in. (750 mm).
b.MSE and TMSE Wall Installation. MSE and TMSE wall installation shall be according to the following.
1.General. The Contractor shall obtain technical assistance from the supplier prior to and during wall erection to ensure proper construction of the wall. The foundation soils supporting the structure shall be graded for a width equal to or exceeding the length of the soil reinforcement. Prior to wall construction, the foundation soils shall be compacted according to Section 205, except the minimum required compaction shall be 95 percent of maximum density as determined by Illinois Modified AASHTO T 99. Any foundation soils found to be unsuitable shall be Art. 522.09 Retaining Walls removed and replaced, as directed by the Engineer. Unsuitable material shall be disposed of according to Article 202.03. The select fill shall be defined as the material placed in the reinforced volume behind the wall panels or sacrificial facing. When pile sleeves are specified they are to reduce skin friction between the select fill and the pile. The pile sleeve material, shape, and wall thickness shall be submitted to the Engineer for approval. It shall have adequate strength to withstand the select fill pressures without collapse until after completion of the wall settlement. The annulus between the pile and the sleeve shall be as small as possible while still allowing it to be filled with loose, dry sand after wall erection.
2.MSE Walls. The concrete leveling pads shall have a minimum thickness of 6 in. (150 mm) and shall be placed according to Section 503. The top of the leveling pad shall be located at or below the theoretical top of the leveling pad line shown on the plans. The theoretical top of leveling pad line shall be 3 1/2 ft (1.1 m) below finished grade line at the front face of the wall. As select fill material is placed behind a panel, the panel shall be maintained in its proper position according to the supplier specifications. A 3/4 in. (19 mm) joint separation shall be provided between all adjacent face panels to prevent direct concrete to concrete contact. This gap shall be maintained by the use of bearing pads and/or alignment pins. The back of all panel joints shall be covered by a geotextile filter material attached to the panels with a suitable adhesive. The minimum fabric width shall be 12 in. (300 mm) and laps shall be a minimum of 6 in. (150 mm). No adhesive will be allowed directly over the joints. Where concrete coping or barrier is specified, the panels shall extend up into the coping or barrier as shown on the plans. The top of the panels may be level or sloped to satisfy the top of exposed panel line shown on the plans. Cast-in-place concrete will not be an acceptable replacement for panel areas below the top of exposed panel line. As an alternative to cast-in-place coping, the Contractor may substitute a precast coping, the details of which shall be included in the shop drawings and approved by the Engineer.
3.TMSE Walls. If a fine aggregate is used for the select fill, the maximum lift thickness placed within the 3 ft (1 m) behind the sacrificial fascia shall be reduced to 5 in. (125 mm). As an alternative, a coarse aggregate may be used without a reduced lift thickness.
4.Select Fill. The select fill and embankment placement shall closely follow the erection of each lift of panels. At each soil reinforcement level, the fill material shall be leveled and compacted before placing and attaching the soil reinforcing system. The soil reinforcement and the select fill shall be placed according to the supplier’s recommended Retaining Walls Art. 522.10 procedures, except the lifts for select fill shall not exceed 10 in. (250 mm) loose measurement. Embankment shall be constructed according to Section 205. At the end of each day’s operations, the Contractor shall shape the last level of select fill to permit runoff of rainwater away from the wall face. Select fill shall be compacted according to Section 205, except the minimum required compaction shall be 95 percent of maximum density as determined by Illinois Modified AASHTO T 99, except select fill gradations CA 7, 8, 11, 13, 14, 15, and 16 shall be compacted, using a growth curve or other method, to a density acceptable to the Engineer. For fine aggregates, the minimum percent of maximum density, as determined by Illinois Modified AASHTO T 99, may be increased as specified by the Engineer if needed to achieve the required friction angle. Select fill compaction shall be accomplished without disturbance or distortion of the soil reinforcing system or panels. Compaction of the 3 ft (1 m) wide strip adjacent to the backside of the facing shall be achieved using a lightweight mechanical tamper, roller, or vibratory system.
5.Construction Tolerances. Construction tolerances shall be as follows.
a.MSE Wall.
1.Vertical and horizontal alignment of the wall shall be within 3/4 in. (19 mm) of the plan location when measured along a 10 ft (3 m) straightedge.
2.The maximum allowable offset in any panel joint shall be 3/4 in. (19 mm).
3.The overall vertical (plumbness from top to bottom) shall not exceed 1/2 in. per 10 ft (13 mm per 3 m) of wall height.
4.The precast face panels shall be within 1 in. (25 mm) of the plan offset at any location to ensure proper wall location at the top of the wall.
b.TMSE Walls. The sacrificial fascia shall be within 3 in. (75 mm) from the plan offset at any location. Failure to meet these tolerances may require modifications to the wall up to and including removal and reinstallation of the affected portions of the wall.
522.10 Precast Modular Retaining Wall Systems. The precast modular wall
system shall consist of precast concrete modules, select fill, joint separation material, geotextile, a concrete or aggregate leveling pad, and any other accessories needed to construct the wall. The precast concrete modules shall be sized to have sufficient stability at each module course to satisfy the design criteria. The material, fabrication, and construction shall also meet the requirements specified by the supplier of the wall system selected by the Contractor. Art. 522.10 Retaining Walls
a.Design Criteria. Design computations and shop drawings shall be submitted according to Article 522.05. The design shall be according to AASHTO LRFD Bridge Design Specifications for Prefabricated Modular Walls, except as modified herein. The Contractor shall be responsible for internal and external stability aspects of the wall design (including sliding, overturning, and bearing pressure). The Department will be responsible for the analyses of settlement and overall slope stability. For design purposes of the wall system, embankment placed behind the precast modules or behind the reinforced volume of select fill shall be assumed to have a unit weight of 120 lb/cu ft (1922 kg/cu m) and an effective friction angle of 30 degrees. External loads, such as those applied through structure foundations, from traffic or railroads, slope surcharge, etc., shall be accounted for in the external stability design. The presence of all appurtenances behind, in front of, mounted upon, or passing through the wall volume such as drainage structures, utilities, structure foundation elements or other items shall be accounted for in the internal and external stability design of the wall. The maximum applied equivalent uniform bearing pressure under each precast concrete module shall be clearly indicated on the shop drawings submitted and shall be less than the allowable bearing pressure of the soil shown on the plans. Footings or other treatments to satisfy the bearing pressure requirements shall be designed by the Contractor. All module types shall be detailed. The details shall show all dimensions necessary to cast and construct each type of module, all reinforcing steel in the module, and the location of any shear key or connection devices. All details of the wall module placement around all appurtenances located behind, on top of, or passing through the wall modules and select fill such as traffic barriers, coping, foundations, utilities, etc. shall be clearly indicated. Any modifications to the design of these appurtenances to accommodate a particular system shall also be submitted. When specified on the plans, all details of architectural treatment for the exposed surfaces of the module, including color, texture, and form liners shall be shown. If additional information is needed to complete the design, the Contractor shall be responsible for obtaining the information.
b.Installation Requirements. Installation requirements shall be as follows.
1.General. The Contractor shall obtain technical assistance from the supplier prior to and during wall erection to ensure proper construction of the wall. The foundation soils for the structure shall be graded for a width equal to or exceeding the precast concrete module width. Prior to wall Retaining Walls Art. 522.10 construction, the foundation soils shall be compacted according to Section 205, except the minimum required compaction shall be 95 percent of maximum density as determined by Illinois Modified AASHTO T 99. Any foundation soils found to be unsuitable shall be removed and replaced, as directed by the Engineer. Unsuitable material shall be disposed of according to Article 202.03. Precast concrete modules shall be lifted and supported at the points indicated on the shop plans. They shall be stored off the ground. Stacked precast concrete modules shall be separated by battens across the full width of each bearing point to prevent concrete to concrete contact. The concrete leveling pads may be precast or cast-in-place and shall have a minimum thickness of 6 in. (150 mm) and shall be placed according to Section 503. Aggregate leveling pads shall be compacted coarse aggregate with a gradation of CA 6 or CA 10. The top of the leveling pad shall be located at or below the theoretical top of the leveling pad line shown on the plans. The theoretical top of leveling pad line shall be 3 1/2 ft (1.1 m) below finished grade line at the front face of the wall. The first course of precast concrete modules shall be erected with particular care and adjustment to correct the vertical, horizontal, and transverse alignment. A 1/4 in. (6 mm) minimum and 3/4 in. (19 mm) maximum joint separation shall be provided between adjacent precast concrete modules at the face to prevent direct concrete to concrete contact. This joint separation shall be maintained by the use of bearing pads and/or alignment pins. The rear face of all precast concrete module joints shall be covered by a geotextile filter fabric, according to the wall supplier’s recommendations. No adhesive will be allowed directly over the joints. The minimum fabric width shall be 12 in. (300 mm) and laps shall be a minimum of 6 in. (150 mm). The select fill and embankment placement shall closely follow the erection of each course of precast concrete modules. The select fill shall be placed according to the supplier's recommended procedures, except the lifts shall not exceed 10 in. (250 mm) loose measurement. At the end of each day’s operations, the Contractor shall shape the last level of select fill to permit runoff of rainwater away from the wall face. Select fill shall be compacted according to Section 205, except the minimum required compaction shall be 95 percent of maximum density as determined by Illinois Modified AASHTO T 99, except select fill gradations CA 7, 8, 11, 13, 14, 15, and 16 shall be compacted, using a growth curve or other method, to a density acceptable to the Engineer. For fine aggregates, the minimum percent of maximum density, as Art. 522.11 Retaining Walls determined by Illinois Modified AASHTO T 99, may be increased as specified by the Engineer if needed to achieve the required friction angle. Where concrete coping or barrier is specified, the modules shall extend up into the coping or barrier a minimum of 2 in. (50 mm). The top of the modules may be level or sloped to satisfy the top of module line shown on the plans. Cast-in-place concrete will not be an acceptable replacement for module areas below the top of module line. Precast coping may be substituted for the cast-in-place coping if approved by the Engineer.
2.Construction Tolerances. Construction tolerances shall be as follows.
a.Vertical and horizontal alignment of the wall shall be within 3/4 in. (19 mm) of the plan location when measured along a 10 ft (3 m) straightedge.
b.The overall conformance to the specified batter from top to bottom shall not exceed 1/2 in. per 10 ft (13 mm per 3 m) of wall height. Failure to meet these tolerances may require modifications to the wall up to and including removal and reinstallation of the affected portions of the wall.
522.11 Geotextile Retaining Walls. Geotextile walls shall consist of
successive layers of geotextile fabric anchored by placing select fill retained at the face by extending the fabric over a removable form brace and re-embedding the remaining fabric back into the select fill. The material specifications and construction methods shall comply with the requirements specified by the geotextile supplier selected by the Contractor.
a.Design Criteria. Design computations and shop drawings shall be submitted according to Article 522.05. The Contractor shall select a geotextile fabric which will provide an allowable tensile strength larger than the minimum value (Tmin) specified on the plans. The Contractor shall consider the project specific strength reduction due to long-term creep, as well as installation damage in their calculations to determine the required tensile strength of the geotextile selected for use. The determination of the required tensile strength of the fabric shall follow the AASHTO LRFD Bridge Design Specifications for Mechanically Stabilized Earth Wall Design, using geosynthetic reinforcement. The design life for the wall shall be 36 months.
b.Installation Requirements. Installation requirements shall be as follows.
1.General. Prior to wall construction, the foundation soils supporting the wall shall be graded to a level uniform condition and compacted such that it is free from ruts and protruding objects such as rocks or sticks for a width equal to the length of the geotextile reinforcement. Any foundation soils found to be unsuitable shall be removed and replaced, as directed by the Engineer. Retaining Walls Art. 522.11 Each layer of the wall shall be placed horizontally as shown in the construction sequence on the plans. The geotextile shall be stretched out in the direction perpendicular to the wall face to ensure that no slack or wrinkles exist in the geotextile prior to select fill placement. The select fill shall be placed or pushed onto the geotextile in a manner that does not distort or distress the fabric. The select fill shall not be dropped onto the fabric from a distance of more than 4.75 ft (1.5 m) and end dumping select fill from trucks directly onto the fabric will not be permitted. A minimum of 4 in. (100 mm) of select fill material shall be present between the geotextile and any equipment tires or tracks. Sudden turning of equipment on the select fill will not be permitted. Any damage to the fabric shall be repaired. As select fill material is placed against the form brace, the form brace shall be maintained in position to produce proper fabric face alignment after the form brace is removed. The removable form brace detail shown in the plans is provided as a guide, the Contractor shall be responsible for the actual form brace used to support the fabric face. Select fill shall be compacted in 6 in. (150 mm) maximum lifts and the minimum required compaction shall be 95 percent of maximum density as determined by Illinois Modified AASHTO T 99, except select fill gradations CA 13, 14, 15, and 16 shall be compacted, using a growth curve or other method, to a density acceptable to the Engineer. For fine aggregates, the minimum percent of maximum density, as determined by Illinois Modified AASHTO T 99, may be increased as specified by the Engineer if needed to achieve the required friction angle. Compaction in a 3 ft (1 m) wide strip adjacent to the backside of the panels shall be achieved using a lightweight mechanical tamper, roller, or vibratory system. The embankment placement shall closely follow the erection of each lift of geotextile and select fill. The select fill material shall be leveled and compacted prior to placing the next level of geotextile. Where geotextile fabric splices perpendicular to the wall face are required to connect separate pieces of geotextile, the fabric shall be overlapped by at least 4 ft (1.2 m). No splices are allowed parallel to the wall face as the geotextile must extend continuously from the rear limits of the soil reinforcement, around the face, and terminate at the end of the re-embedment length. At locations where the plans specify a change of wall alignment, the fabric shall be neatly folded over itself to create inside turns, or it may be cut perpendicular to the wall face and lapped at the wall face for outside wall turns to ensure no loss of select fill. Fabric layers shown terminating against a cut slope, sheet piling, concrete walls, or other structures shall have at least 3 ft (1 m) of additional fabric extending past or placed against the surface, folded back in such a manner to ensure adequate embedment and no loss of select fill. At the end of each day’s operations, the Contractor shall shape the last level of select fill to permit runoff of rainwater away from the wall face. Art. 522.12 Retaining Walls
2.Construction Tolerances. Construction Tolerances shall be as follows.
a.The thickness of each geotextile reinforcement layer shall be within 3 in. (75 mm) of that shown on the plans.
b.The offset of the wall face bulge shall be within 5 in. (125 mm) of that shown on the plans at each layer, and along the entire length of wall. Failure to meet these tolerances may require modifications to the wall up to and including removal and reinstallation of the affected portions of the wall.
522.12 Segmental Concrete Block Retaining Walls. Segmental concrete
block walls shall consist of precast segmental concrete blocks, select fill, a concrete or aggregate leveling pad, and, if required by the design, soil reinforcement. The wall shall be designed and constructed according to the lines, grades, and dimensions shown on the plans and approved shop drawings.
a.Design Criteria. Design computations and shop drawings shall be submitted according to Article 522.05. The design shall be according to the AASHTO LRFD Bridge Design Specifications for Prefabricated Modular Walls, except as modified herein. The Contractor shall be responsible for internal and external stability aspects of the segmental concrete block wall design (including sliding, overturning, and bearing pressure). The Department will be responsible for the analyses of settlement, bearing capacity, and overall slope stability. If required by design, soil reinforcement shall be utilized and the loading at the segmental concrete block/soil reinforcement connection as well as at the failure surface shall be indicated. The calculations to determine the resistance of the soil reinforcement including pullout shall also be included. External loads such as those applied through structure foundations, from traffic or railroads, slope surcharge, etc., shall be accounted for in the internal stability design. The presence of all appurtenances behind, in front of, mounted upon, or passing through the wall volume such as drainage structures, utilities, structure foundation elements, or other items shall be accounted for in the internal stability design of the wall. All details of the block and/or soil reinforcement placement around all appurtenances located behind, on top of, or passing through the wall shall be clearly indicated. Any modifications to the design of these appurtenances to accommodate a particular design arrangement shall also be submitted. All details of the blocks, including color and texture shall be shown. The exterior face shall preferably be straight, textured with a “split rock face” pattern, and dark gray in color. All block types (standard, cap, corner, and radius turning blocks) shall be detailed showing all dimensions. Retaining Walls Art. 522.12 All blocks shall have alignment/connection devices such as shear keys, leading/trailing lips, or pins. The details for the connection devices between adjacent blocks and the block to soil reinforcement shall be shown. The block set back or face batter shall be limited to 20 degrees from vertical.
b.Installation Requirements. Installation Requirements shall be according to the following.
1.General. The Contractor shall obtain technical assistance from the supplier prior to and during wall erection to ensure proper construction of the wall. The foundation material for the leveling pad and select fill shall be graded to the design elevation and compacted according to Section 205, except the minimum required compaction shall be 95 percent of maximum density as determined by Illinois Modified AASHTO T 99. Any foundation soils found to be unsuitable shall be removed and replaced as directed by the Engineer. Unsuitable material shall be disposed of according to Article 202.03. The concrete leveling pads may be precast or cast-in-place and shall have a minimum thickness of 6 in. (150 mm) and shall be placed according to Section 503. Aggregate leveling pads shall be compacted coarse aggregate with a gradation of CA 6 or CA 10. The top of the leveling pad shall be located at or below the theoretical top of the leveling pad line shown on the plans. The theoretical top of leveling pad line shall be 1 1/2 ft (450 mm) below finished grade line at the front face of the wall. The select fill lift placement shall closely follow the erection of each course of precast segmental concrete blocks. The top of the precast segmental concrete blocks shall be clean prior to placing the next block lift. If soil reinforcement is used, the select fill material shall be leveled and compacted before placing and attaching the soil reinforcement to the precast segmental concrete blocks. The soil reinforcement shall be pulled taut, staked in place, and select fill placed from the rear face of the precast segmental concrete blocks outward. The lift thickness shall be the lesser of 10 in. (250 mm) loose measurement or the proposed precast segmental concrete blocks height. The select fill shall be compacted according to Section 205, except the minimum required compaction shall be 95 percent of maximum density as determined by Illinois Modified AASHTO T 99, except select fill gradations CA 7, 8, 11, 13, 14, 15, and 16 shall be compacted, using a growth curve or other method, to a density acceptable to the Engineer. For fine aggregates, the minimum percent of maximum density, as determined by Illinois Modified AASHTO T 99, may be increased as specified by the Engineer if needed to achieve the required friction angle. Compaction shall be achieved using a lightweight mechanical tamper, roller, or vibratory system. The top 12 in. (300 mm) of backfill Art. 522.13 Retaining Walls shall be topsoil according to Section 211, capable of supporting vegetation. When a fine aggregate is selected, the rear of all block joints shall be covered by a non-woven needle punch geotextile filter material. All fabric overlaps shall be 6 in. (150 mm) and non-sewn. As an alternative to the geotextile, a coarse aggregate shall be placed against the back face of the blocks to create a minimum 12 in. (300 mm) wide continuous gradation filter to prevent the select fill material from passing through the block joints. Cap blocks shall be used to cover the top of the standard block units. The top course of blocks and cap blocks shall be stepped to satisfy the top of block line shown on the contract plans.
2.Construction Tolerances. Construction Tolerances shall be as follows.
a.Vertical and horizontal alignment shall not exceed 1/2 in. (13 mm) when measured along a 10 ft (3 m) straight edge.
b.The overall conformance to the specified batter from top to bottom shall not exceed 1/2 in. per 10 ft (13 mm per 3 m) of wall height. Failure to meet these tolerances may require modifications to the wall up to and including removal and reinstallation of the affected portions of the wall.
522.13 Cast-in-Place Concrete Retaining Walls. Cast-in-place concrete
walls shall consist of reinforced cast-in-place concrete, which may be supported on spread footings, piles, or drilled shafts. The design and details shall be as shown on the plans. Subject to the approval of the Engineer, the Contractor may substitute precast modular concrete for the cast-in-place concrete wall shown. The precast modular wall shall be according to Article 522.10. Any redesign necessary to accommodate the precast option shall be the responsibility of the Contractor and shall be submitted for approval according to Article 522.05 prior to starting the work.
522.14 Obstruction Mitigation. For sheet pile, temporary soil retention, and
soldier pile walls, obstructions shall be addressed according to Article 516.14.
522.15 Method of Measurement. This work will be measured for payment as
follows.
a.Contract quantities. The requirements for the use of contract quantities shall conform to Article 202.07(a).
b.Measured quantities. Both temporary and permanent sheet piling will be measured for payment in place in square feet (square meters). Any temporary sheet piling cut off, left in place, or driven to dimensions other than those shown on the contract plans without the permission of the Engineer will not be measured for payment. Permanent sheet piling that is Retaining Walls Art. 522.15 cut off or driven beyond those dimensions shown on the plans will not be measured for payment. If the Contractor is unable to drive temporary sheeting to the specified tip elevation(s) and can demonstrate that any further effort to drive it would result in damaging the sheeting, then the Contractor shall be paid based on the plan quantity of temporary sheeting involved. However, no additional payment will be made for any walers, bracing, or other supplements to the temporary sheet piling, which may be required as a result of the re- evaluation in order to ensure the original design intent was met. Temporary soil retention systems furnished and installed will be measured for payment in place, in square feet (square meters). The area measured shall be the minimum vertical exposed surface area envelope of the excavation supported by the temporary soil retention system. Portions of a temporary soil retention system or temporary sheet piling left in place for reuse in later stages of construction will only be measured for payment once. The furnishing of soldier piles will be measured for payment in feet (meters) along the centerline of the soldier pile for each of the types specified. The length will be determined as the difference between the plan top of soldier pile and the final as built shaft excavation bottom, or the plan shaft excavation bottom, whichever is less. The driving of soldier piles will be measured for payment in feet (meters) along the centerline of the soldier pile. The length will be determined as the difference between the plan top of soldier pile and the final as built shaft excavation bottom, or the plan shaft excavation bottom, whichever is less. The drilling and setting of soldier piles in soil and rock will be measured for payment and the volumes computed in cubic feet (cubic meters) for the shaft excavation required to set the soldier piles according to the plans. These volumes will be the theoretical volumes computed using the diameter(s) of the shaft(s) shown on the plans and the depth of the excavation in soil and/or rock. The depth in soil will be defined as the difference in elevation between the ground surface at the time of concrete placement and the bottom of the shaft excavation or the top of rock (when present), whichever is encountered first. The depth in rock will be defined as the difference in elevation between the measured top of rock and the bottom of the shaft excavation. Drilling and placing CLSM secant lagging will be measured for payment in cubic feet (cubic meters) of the shaft excavation required to install the secant lagging as shown on the plans. This volume shall be the theoretical volume computed using the diameter(s) shown on the plans and the difference in elevation between the ground surface at the time of CLSM placement and the as built shaft excavation bottom, or the plan shaft excavation bottom, whichever is less. Art. 522.15 Retaining Walls Timber and precast concrete lagging will be measured for payment in square feet (square meters) of lagging installed to the limits as shown on the plans. The quantity will be calculated using the minimum lagging length required on the plans multiplied by the as installed height of lagging, for each bay of lagging spanning between the soldier piles. MSE retaining walls will be measured for payment in square feet (square meters). The MSE wall will be measured from the top of exposed panel line to the theoretical top of leveling pad line for the length of the wall as shown on the plans. TMSE retaining walls will be measured for payment in square feet (square meters). The TMSE wall will be measured from the top of exposed sacrificial fascia line to the theoretical bottom of sacrificial fascia line for the length of the wall as shown on the plans. Geotextile retaining walls will be measured for payment in square feet (square meters) of completed wall face. The area will be calculated from the top limits of the geotextile to the bottom level of fabric reinforcement at each variation along the length of the wall as shown on the plans. Segmental concrete block retaining walls will be measured for payment in square feet (square meters) of wall face from the top of block line to the theoretical top of the leveling pad for the length of the wall in a vertical plane as shown on the plans. Precast modular retaining walls will be measured for payment in square feet (square meters). The precast modular wall will be measured from the “top of exposed module line” to the theoretical top of leveling pad line for the length of the wall as shown on the plans. Cast-in-place concrete retaining walls will be measured for payment in cubic yards (cubic meters) according to Article 503.21. Reinforcement bars for cast-in-place concrete retaining walls will be measured for payment in pounds (kilograms) according to Article 508.10. Backfill placed outside of the select fill volume for MSE walls will be measured according to Sections 202 and/or 204. Removal and disposal of unstable and/or unsuitable material will be measured for payment according to Article 502.12(b). When structure excavation is necessary it will be measured for payment according to Section 502.12 except:
1.For MSE walls, the horizontal limits for structure excavation shall be from the rear limits of the soil reinforcement to a vertical plane 2 ft (600 mm) in front of the finished face of the wall. The depth shall be from the top of the original ground surface to the top of the leveling pad. The additional excavation necessary to construct the concrete leveling pad will not be measured for payment. Retaining Walls Art. 522.16
2.For soldier pile walls, to place a concrete facing, the horizontal limits for structure excavation shall be from the front face of the soldier pile to a vertical plane 2 ft (600 mm) from the finished face of the wall. The depth shall be from the top of the original ground surface to the bottom of the concrete facing.
3.For precast modular retaining walls and segmental concrete block retaining walls, the horizontal limits for structure excavation shall be from the rear limits of the precast concrete modules or precast segmental concrete blocks to a vertical plane 2 ft (600 mm) in front of the finished face of the wall. The depth shall be from the top of the original ground surface to the base of the precast concrete modules or precast segmental concrete blocks. The additional excavation necessary to construct the soil reinforcement, if required, will not be measured for payment.
522.16 Basis of Payment. This work will be paid for at the contract unit price
per square foot (square meter) for TEMPORARY SHEET PILING, PERMANENT SHEET PILING, TEMPORARY SOIL RETENTION SYSTEM, MECHANICALLY STABILIZED EARTH RETAINING WALL, TEMPORARY MECHANICALLY STABILIZED EARTH RETAINING WALL, GEOTEXTILE RETAINING WALL, PRECAST MODULAR RETAINING WALL, or SEGMENTAL CONCRETE BLOCK WALL. Concrete coping for MSE walls and precast modular walls, when specified on the plans, will not be paid for separately. Other concrete appurtenances for MSE walls such as anchorage slabs, parapets, abutment caps, etc., are not included in this work and will be paid for separately. The furnishing of soldier piles will be paid for at the contract unit price per foot (meter) for FURNISHING SOLDIER PILES, of the type specified. The driving of soldier piles will be paid for at the contract unit price per foot (meter) for DRIVING SOLDIER PILES. Any bracing, cutoffs, or splicing required will not be paid for separately but shall be included in this item. The drilling and setting of soldier piles will be paid for at the contract unit price per cubic foot (cubic meter) for DRILLING AND SETTING SOLDIER PILES (IN SOIL) or DRILLING AND SETTING SOLDIER PILES (IN ROCK). The required shaft excavation, soldier pile encasement concrete, and any CLSM backfill required around each soldier pile will not be paid for separately but shall be included in this item. Soldier pile wall components, such as concrete facing, shear studs, reinforcement bars, tie backs, hand rails, and various drainage items, etc., are not included in this work and will be paid for separately. The timber lagging will be paid for at the contract unit price per square foot (square meter) for UNTREATED TIMBER LAGGING or TREATED TIMBER LAGGING. Art. 522.16 Retaining Walls The precast concrete lagging will be paid for at the contract unit price per square foot (square meter) for PRECAST CONCRETE LAGGING. The secant lagging will be paid for at the contract unit price per cubic foot (cubic meter) for SECANT LAGGING. The required shaft excavation and CLSM backfill required to fill the excavation will be included in this item. Cast-in place concrete retaining walls will be paid for at the contract unit price per cubic yard (cubic meter) for CONCRETE STRUCTURES (RETAINING WALL). Reinforcement bars for cast-in-place concrete retaining walls will be paid for according to Article 508.11. If a precast alternate is substituted for a cast-in-place concrete retaining wall, no adjustment in the cost for the specified cast-in-place wall will be allowed. Compensation under the contract bid items for concrete structures (retaining wall) and reinforcement bars shall cover the cost of the precast concrete wall alternate. If a temporary soil retention system is substituted for a temporary sheet piling wall at the Contractor’s request, no adjustment in the cost for the specified wall will be allowed. Compensation under the contract bid item for temporary sheet piling shall cover the cost of the temporary soil retention system alternate. If a drilling and setting soldier alternate is substituted for a driven soldier pile installation, no adjustment in the cost for the specified wall will be allowed. Compensation under the contract bid item for driving soldier piles shall cover the cost of the soldier pile installation. Geocomposite wall drains will be paid for according to Section 591. Backfill placed outside of the select fill volume for MSE walls will be paid for according to Sections 202 and/or 204. Removal and disposal of unstable and/or unsuitable material will be paid for according to Article 502.13. Payment for any excavation, related solely to the installation and/or removal of a temporary retaining wall system and/or its components, or for the installation of lagging will not be paid for separately but shall be included in the unit bid price for that system. Payment for any other excavation performed in conjunction with this work as previously defined shall be as specified in Article 502.13. Obstruction mitigation will be paid for according to Article 109.04. Any costs related to obtaining technical assistance for the construction a wall system from a particular supplier will not be paid for separately but shall be included in the unit price bid for that item of work. Box Culverts Art. 540.02 SECTION 523. DRAINAGE SYSTEM FOR STRUCTURES
523.01 Description. This work shall consist of constructing a bridge drainage
system.
523.02 Materials. Materials shall be according to the following.
Item Article/Section
a.Reinforced Thermosetting Resin Pipe (RTRP) .................................. 1040.09
b.Metal Hardware Cast into Concrete ................................................... 1006.13
c.Grout .................................................................................................. 1024.01 CONSTRUCTION REQUIREMENTS
523.03 General. The Contractor shall make allowances for the differential
expansion and contraction expected between the superstructure and substructure, both horizontal and vertical, to which the drainage system is attached. All connections of pipes and fittings shown on the plans to facilitate maintenance cleanout shall be made with a threaded, gasketed coupler or a bolted gasketed flange system. Adhesive bonded joints will be permitted for runs of pipes between such connections. The end run connection shall feature a minimum nominal 6 in. (150 mm) female threaded fiberglass outlet. Straight runs may utilize a 45 degree reducing saddle bonded to the pipe. The female outlet shall be filled with a male threaded PVC plug. When drainage systems connect with concrete drainage structures, the connection between the end run and the drainage structure shall be sealed with grout.
523.04 Basis of Payment. This work will be paid for at the contract lump sum
price for DRAINAGE SYSTEM FOR STRUCTURES. CULVERTS SECTION 540. BOX CULVERTS
540.01 Description. This work shall consist of constructing cast-in-place
concrete and precast concrete box culverts.
540.02 Materials. Materials shall be according to the following.
Item Article/Section
a.Cast-In-Place Culverts ......................................................................... 503.02
b.Precast Culverts ................................................................................ 1042.05
c.Coarse Aggregate (Note 1) ................................................................ 1004.05
d.Mastic Joint Sealer for Pipe .................................................................... 1055
e.External Sealing Band ............................................................................ 1057
Referenced in this section
Sections that cite this one
RETAINING WALLS in other states
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Source: Illinois Standard Specifications for Road and Bridge Construction, 2022 Edition. Pages 444–464 of 1,217. View official source ↗