MSE Retaining Walls – General Requirements MSE RETAINING WALL S – GENERAL REQUIREMENTS
Part 1 — General
1.1 Section Includes
A.General requirements for mechanically stabilized earth (MSE) retaining walls of the following types:
1.Concrete panel MSE retaining walls using metal or geogrid soil reinforc ement .
2.Modular block MSE retaining walls using metal or geogrid soil reinforc ement .
3.Permanent Wire Face MSE retaining walls using metal soil reinforc ement .
1.2 Related Sections
A.Section 02832: MSE Backfill
B.Section 02833: Concrete Panel MSE Retaining Wall
C.Section 02835: Modular Block MSE Retaining Wall
D.Section 02837 : Wire Face MSE Retaining Wall
1.3 References
A.AASHTO M 111: Zinc (Hot -dip Galvanized) Coatings on Iron and Steel Products
B.AASHTO LRFD Bridge Design Specifications
C.FHWA -NHI-10-025 “Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Slopes – Volume s I and II”, November 2009 (GEC 11)
D.UDOT Geotechnical Manual of Instruction (GMOI)
1.4 DEFINITIONS Not Used
MSE Retaining Walls – General Requirements
1.5 Submittals
A.Contractor -selected retaining wall system for information before the preconstruction meeting.
1.Refer to this Section, Article 2. 1.
2.Include the name and experience for the Wall Company technical representative assigned to the project.
B.Qualifications for review
1.MSE Wall Quality Coordinator
a.Include the name and MSE wall construction experience.
2.MSE Wall On-Site Supervisor(s)
a.Include the name and MSE wall construction experience for each person that provides direct supervision over each MSE wall construction crew.
C.Quality Control Plan for review
1.Include at least the following:
a.Methods and procedures that will be used to verify the wall will be built per the authorized plans, tolerances and other specification requirements specific to the wall system being used will be met .
b.Methods to verify proper MSE backfill is being used and compaction requirements are being met.
c.Procedures to correct out of -tolerance alignments and joints
d.Measurements, checklists, and dail y documentation that will be maintained during construction to assure consistency in meeting specification requirements . 1) Include appropriate control points where measurements are taken to verify compliance with facing tolerances. 2) Include checklists that document compliance with the quality control plan, the W all Company’s construction manual and specification requirements. a) Use the MSE Wall Construction Checklist available on the Department’s website as a baseline . Refer to http://www.udot.utah.gov/go/standardsreferenc es
e.Wall Company’s construction manual for the selected wall system
2.Describe process of c oordinat ing quality control measures with the MSE Wall Company’s technical representative. MSE Retaining Walls – General Requirements
D.Samples for verification
1.Concrete Panel MSE Retaining Walls
a.Panel surface texture before casting of the panels.
2.Modular Block MSE Retaining Walls
a.Modular block unit that meets the face pattern, texture and color requirements shown.
E.Working Drawings
1.Retaining wall drawings for review.
a.Include the following: 1) Plans, profiles, cross- sections , quantities, and details for each retaining wall . 2) Cast-in-place concrete coping or cap to the facing panels or blocks . a) Aesthetically pleasing b) Adequately support s fence, barrier, or both as shown. c) Do not use precast coping without the Engineer’s prior approval. 3) Measures for protecting metal soil reinforcement and metal reinforcement connections from corrosion . 4) Provisions for facilities that penetrate the wall face or soil reinforc ement , such as drainage catch basins, piping, foundation elements, guard- rail posts, and other buried facilities. 5) Surface and subsurface drainage details. 6) Architectural treatment detail s for wall facing elements and concrete color as shown. 7) Structure number details
b.Include supporting calculations sufficient to demonstrate that the retaining walls are designed according to the required criteria.
c.Provide the seal of a Professional Engineer (PE) or Professional Structural Engineer (SE) licensed in the State of Utah on the drawings and calculations.
F.Certificate of compliance for incorporated materials with test results of tests performed for information. Include at least the following in addition to the certificate of compliance general requirements:
1.Modular blocks and cap blocks.
a.Include certified test reports for compressive strength, freeze- thaw durability, absorption, density, and dimensional tolerances. MSE Retaining Walls – General Requirements
2.Metal soil reinforcement ( strips, welded wire and grid, wire facing, cap mes h, woven wire mesh) and other steel elements (l oop embeds, fasteners, tie strips, lifting devices, connector rods, hairpin connectors )
a.Signed Mill Test Reports with at least the following: 1) Ultimate tensile strength 2) Ultimate weld strength for mesh soil reinforcement 3) Galvanization coverage including amount applied and average thickness
3.Geogrid soil reinforcement
a.Manufacturer’s product data sheet and installation instructions
b.Certified test reports that demonstrate the average roll value for each geogrid product is greater than or equal to the geogrid ultimate wide width tensile strength published in the manufacturer’s product data sheet and installation instructions.
c.Include the Long Term Factored Tensile Design Strength and the following reinforcement reduction factors: 1) Long term tension creep 2) Durability 3) Installation damage
4.Filter fabric, filter fabric adhesive, cap block adhesive, concrete panel bearing pads, facing infill rock, and modular block fill
a.Certify compliance with specified requirements.
b.Include t est results for tests performed by the Contractor or the manufacturer that are necessary to verify compliance with the specifi ed requirements.
5.Include a statement that the products used satisfy the design requirements for the authorized retaining wall drawings .
G.Test results for source material of MSE Backfill for review. Include the following:
1.Organic content
2.Sodium sulfate soundness
3.Gradation
4.Plasticity Index
5.Internal friction angle
6.Electrochemical properties
H.Gradation Substitution Request where MSE backfill meeting metal reinforcement gradation is to be used in a wall that uses geogrid reinforcement for review.
1.Include test results and calculations for determining the installation damage reduction factor. MSE Retaining Walls – General Requirements
2.Refer to Section 02832.
I.Construction Documentation for information .
1.A letter at wall completion signed by the on -site supervisor and Wall Quality Coordinator certifying that the wall construction complies with the specified requirements and the authorized quality control plan.
a.Include the completed checklist.
2.Test results for electrochemical properties of MSE backfill.
J.Field Observations Report from the Wall Company for information
1.Include a signed letter stating that the wall meets Department and Wall Company requirements based upon the Wall Company’s technical representative’s onsite observations .
1.6 Quality Control
A.Wall Company’s Technical Representative
1.Provide a qualified technical representative from the selected Wall Company. The Wall Company’s technical representative must:
a.Have MSE retaining wall design and construction experience on at least five walls of similar size and type within the previous five years.
b.Provide technical a nd constructability support and training to the Contractor’s wall construction crew(s) and Department inspectors regarding proper quality control for construction of the walls.
c.Be available and provide technical assistance during all phases of wall construction.
d.Be present during wall construction at least as follows: 1) The first five working days of the construction of each wall and until all aspects of wall construction have been satisfactorily demonstrated to the Wall Company’s technical representative and the Engineer. a) Be at the project site for at least the first five working days of both the first and second stage of wall construction for two- stage wall systems. 2) The Department reserves the right to require the Wall Company’s technical representative to be onsite at no additional cost to the Department if at any time the Engineer is concerned with the construction quality.
e.Meet with the Engineer near the conclusion of each site visit to report on the observed wall construction procedures. MSE Retaining Walls – General Requirements
B.MSE Wall Quality Coordinator
1.Designate a qualified MSE wall quality coordinator. The MSE wall quality coordinator must:
a.Have MSE wall construction experience on at least five MSE retaining walls of similar size and type within the previous five years.
b.Coordinate closely with t he Wall Company ’s technical representative and the Engineer to verify issues and potential issues are properly addressed in a timely manner.
c.Be responsible for ensuring that the quality control procedures are implemented according to the MSE w all quality plan.
d.Have sufficient authority to carry out quality coordinator responsibilities
e.Be in the field during MSE w all construction
f.Maintain required checklists and other documentation according to the MSE wall quality plan.
g.Verify that wall construction personnel attend the MSE wall construction training.
2.The MSE w all quality coordinator cannot be an on- site supervisor when the MSE wall exposed area for the project is greater than 20,000 sq ft.
C.MSE Wall On -Site Supervisor
1.Provide an MSE wall on- site supervisor at each wall construction site. MSE wall onsite supervisor(s) must:
a.Have MSE wall construction experience on at least five MSE retaining walls of similar size and type within the previous five years, at least three of which were in a supervisory role .
b.Provide continual supervision during all phases of wall construction.
D.MSE Wall Construction Training
1.Provide training for Contractor and Department personnel before wall construction begins. Include at least the following:
a.Correct MSE wall construction procedures
b.Important aspects for the selected wall system from the Wall Company’s construction manual.
c.Procedures, methods, and documentation according to the MSE wall quality plan.
2.The MSE wall quality coordinator and the Wall Company’s technical representative conduct the training.
3.Attendance is mandatory for the following:
a.MSE wall quality coordinator MSE Retaining Walls – General Requirements
b.On-site supervisors
c.All personnel who participate in the wall construction
d.Wall Company’s technical representative
4.The MSE quality coordinator trains new personnel who did not attend the initial training.
5.Document training attendance.
E.Complete documentation according to the MSE w all quality plan
1.Maintain quality records and make available to the D epartment upon request.
2.Checklists for each MSE wall are signed by the MSE wall on- site supervisor and MSE w all quality coordinator.
1.7 Acceptance
A.The Engineer may allow a concrete panel or modular block MSE retaining wall to remain in place at a reduced price when the w all facing elements do not meet the specified tolerances , provided that the retaining wall is adequate to serve the design purpose.
1.The Engineer determines whether a retaining wall is adequate to serve the design purpose.
a.Adequacy to serve the design purpose is determined based upon aesthetics, geometry, and structural integrity.
2.The wall facing will be evaluated in 100 ft se gment s by wall station.
a.The wall facing will be measured after the wall construction is complete. 1) Measurements may be taken before the wall coping is placed to facilitate measuring.
b.The Engineer may determine the measurement locations and types by visual inspection.
c.The Engineer will determine the segment pay factor for each measurement type (vertical alignment, plumbness, facing element levelness, joint width, and joint offset) according to Table 1 .
3.The Engineer will combine the segment pay factors resulting in a total pay factor for the wall for each measurement type.
a.The total pay factor s for the wall are calculated using a weighted average. 1) The weighted average is calculated by multiplying the segment pay factor by the segment wall area divided by the total wall area and combining the result s for all wall se gment s. MSE Retaining Walls – General Requirements
b.Wall s egments with measurements listed as "Reject" in Table 1 must be corrected or deemed adequate to serve the design purpose with a segment pay factor determined by the Engineer before final payment for the wall is made. 1) A pay factor of 0.5 will be used for wall segments that are allowed to remain in place when listed as “Reject”.
4.The governing pay factor is the lowest total pay factor for the wall from the total pay factors for each measurement type.
5.The reduced price for the wall is calculated by multiplying the lump sum price for the wall in the Bid Schedule by the governing pay factor.
6.A spreadsheet is available on the Department’s website to assist in the pay factor calculations.
a.Refer to: http://www.udot.utah.gov/go/standardsreferences . MSE Retaining Walls – General Requirements Table 1 Pay Factors For Out -Of-Tolerance M SE Wall Facing Elements * Measurement Type Pay Factor Wall Facing Measurements Over 1%** Over 10 %** Over 20 %** Over 30%** Applicable to Concrete Panel and Modular Block MSE Wall Types Vertical Alignment*** (percent ) Spec: 0.7% 1.00 --- --- --- ---
0.95 over 1.75 over 1.40 over 1.05 over 0.70
0.90 over 2.10 over 1.75 over 1.40 over 1.05
0.80 over 2.45 over 2.10 over 1.75 over 1.40
0.60 over 2.80 over 2.45 over 2.10 over 1.75
Reject over 3.15 over 2.80 over 2.45 over 2.10 Plumbness (percent) Spec: Positive: 0.7% Negative: -0,4% Reject over 4.20 over 3.70 over 3.20 over 2.70
0.60 over 3.70 over 3.20 over 2.70 over 2.20
0.80 over 3.20 over 2.70 over 2.20 over 1.70
0.90 over 2.70 over 2.20 over 1.70 over 1.20
0.95 over 2.20 over 1.70 over 1.20 over 0.70
1.00 --- --- --- ---
0.95 over -1.30 over -1.00 over -0.70 over -0.40
0.90 over -1.60 over -1.30 over -1.00 over -0.70
0.80 over -1.90 over -1.60 over -1.30 over -1.00
0.60 over -2.20 over -1.90 over -1.60 over -1.30
Reject over -2.50 over -2.20 over -1.90 over -1.60 Levelness (percent) Spec: 0.5% 1.0 --- --- --- ---
0.95 over 0.80 over 0.70 over 0.60 over 0.50
0.9 over 0.90 over 0.80 over 0.70 over 0.60
0.8 over 1.00 over 0.90 over 0.80 over 0.70
0.6 over 1.10 over 1.00 over 0.90 over 0.80
Reject over 1.20 over 1.10 over 1.00 over 0.90 MSE Retaining Walls – General Requirements Table 1 (continued) Pay Factors For Out -Of-Tolerance M SE Wall Facing Elements * Measurement Type Pay Factor Wall Facing Measurements Over 1 %** Over 10 %** Over 20 %** Over 30%** Applicable to Concrete Panel MSE Retaining Walls Only Joint Width (inches) Spec:
0.5 to 1.25
Reject under 0.062 under 0.062 under 0.125 under 0.250
0.6 N/A under 0.125 under 0.250 under 0.375
0.8 under 0.125 under 0.250 under 0.375 under 0.500
0.9 under 0.250 under 0.375 under 0.500 N/A
1.0 --- --- --- ---
0.9 over 1.625 over 1.500 over 1.375 over 1.250
0.8 over 1.750 over 1.625 over 1.500 over 1.375
0.6 over 1.875 over 1.750 over 1.625 over 1.500
Reject over 2.000 over 1.875 over 1.750 over 1.625 Joint Offset (inches) Spec: 0.375
1.0 --- --- --- ---
0.95 over 0.750 over 0.625 over 0.500 over 0.375
0.9 over 0.875 over 0.750 over 0.625 over 0.500
0.8 over 1.000 over 0.875 over 0.750 over 0.625
0.6 over 1.125 over 1.000 over 0.875 over 0.750
Reject over 1.250 over 1.125 over 1.000 over 0.875 * Tolerances are according to Sections 02833 and 02835. ** Wall percentage corresponding to out -of-tolerance measurements. Wall percentage is based on face area, wall lineal footage, or length of joints, as applicable for the measurement type. For plumbness of concrete panel walls, the Over 1% column represents one 10 ft wide section of panels that is out of tolerance, the Over 10% column represents two panel columns out of tolerance, etc. *** Vertical alignment is measured as the difference in percent slope at a bulge or depression. For concrete panel walls, measurement is between adjacent panels. For modular block walls , the slope measurement is between points of maximum and minimum horizontal offset .
Part 2 — Products
2.1 Mse Retaining Wall Types
A.Use a Department approved retaining wall system of the retaining wall type shown.
1.A list of approved retaining wall systems is maintained by the Department.
a.Refer to : http://www.udot.utah.gov/go/standardsreferences MSE Retaining Walls – General Requirements
2.Provide a complete retaining wall system from the Wall Company.
a.Obtain wall system components from the Wall Company or the Wall Company’s authorized supplier.
3.Wall system and system components must meet the Wall Company’s published requirements.
B.Concrete Panel MSE Retaining Wall
1.Refer to Section 02833 if a concrete panel MSE retaining wall is shown.
C.Modular Block MSE Retaining Wall
1.Refer to Section 02835 if a modular block MSE retaining wall is shown.
D.Wire Face MSE Retaining Wall
1.Refer to Section 028 37 if a wire face MSE retaining wall is shown.
E.Use only one retaining wall system for each wall type shown.
1.Do not change the wall system after the preconstruction meeting without the Engineer ’s approval .
2.2 Design Requirements
A.Design retaining walls according to the UDOT GMOI and the AASHTO LRFD Bridge Design Specifications, as modified by the following:
1.Provide seismic design according to the UDOT GMOI.
2.Design retaining wall panel and block connections in all cases to hold the facing elements in place during the seismic event corresponding to 3 percent probability of exceedance in 75 years .
a.Use the factored site acceleration, as shown.
3.The Wall Company is responsible for all stability calculations, except global stability and bearing capacity.
4.Provide a service life of at least 75 years.
5.The Wall Company is responsible to verify that drainage features do not negatively impact the wall system .
6.Design the retaining wall to accommodate drainage features to function properly through/beneath the wall without negatively impacting the wall system.
a.This includes checking the drainage system details, and developing appropriate MSE soil reinforcement design details in the vicinity of the drainage features (pipes, catch basins, for example) within the reinforcement mass, and for the outlet point at the wall face. MSE Retaining Walls – General Requirements
7.Provide corrosion protection for metal soil and exposed facing reinforcement by one of the following two measures:
a.Design the metal soil reinforcement to provide sacrificial steel sufficient for a corrosion rate of at least 0.80 mils per exposed surface per year after 16 years of corrosion protection service provided by the galvanized coating.
b.Provide a protective geomembrane (either PVC or HDPE) of at least 30 mils thickness at least 2 ft below the base of the pavement section (below the bottom of the granular borrow layer) . 1) S lope the geomembrane at a grade of 4 percent downwards towards the back of the reinforced mass (for example, away from the wall face) to a point at least 5 ft beyond the back of the soil reinforcement zone, and lap upward against the back side of the wall facing. 2) D esign the metal soil reinforcement to provide sacrificial steel sufficient for the following minimum corrosion rates per exposed surface per year after 16 years of corrosion protection service provided by the galvanized coating: a) Above the Geomembrane: 0.80 mils b) Below the Geomembrane: 0.50 mils
8.Use a vertical spacing of primary soil reinforcement not exceeding 30 inch for single- stage walls, or 24 inch for two- stage walls to provide a coherent MSE reinforced soil mass. a. This may require modification of panels.
9.P rovide horizontal benches with at least a 4 ft width at the base of walls founded on earth slopes as shown .
10.Design wall corners with an acute angle less than 70 degrees as internally tied structure s.
a.Use full at-rest earth pressures.
b.Neglect design benefits from soil arching effects.
c.Provide at least 3 inch vertical separation between geosynthetic soil reinforcement when overlapping.
d.Provide full -height vertical slip joints at the acute angle corner and after the last column of panels where the full length of soil reinforcement can be placed. 1) Orient the soil reinforcement attached to the slip joints perpendicular to the slip joint panels. 2) Use soil reinforcement with the full design length.
e.Provide compaction and reinforcement connection details in the MSE retaining wall drawings MSE Retaining Walls – General Requirements
B.Modify the soil reinforcement design using one of the following alternatives where the soil reinforcement conflicts with obstructions in the wall soil reinforcement zone, such as piles, drilled shafts, guardrail posts, catch basins, drop inlets, and culverts:
1.Design the surrounding soil reinforcement layers to carry the additional load that would have been carried by the severed reinforcement .
2.Place a structural frame around the obstruction that is capable of transferring loads from the soil reinforcement on one side of the obstruction to the soil reinforcement on the other side of the obstruction.
3.Splay the soil reinforcement around the obstruction i f the soil reinforcement consists of discrete strips or bar mats rather than continuous sheets.
C.Structure Number Details
1.Place the structure number on the exposed face of the retaining wall as shown using one of the following methods.
a.Cast the structure number into the concrete fac ing (panel , modular block unit , or coping) .
b.Cut the structure number into a steel plate and attach the steel plate to the wall face. 1) Completely remove excess material from the outline of each character. 2) Hot dip galvanize the plate after cutting the numbers into the plate. a) Refer to AASHTO M 111.
2.Locate the structure number at the beginning of each retaining wall and at 500 ft intervals.
Part 3 — EXECUTION Not Used
Source: Utah Standard Specifications for Road and Bridge Construction, 2026 Edition. Pages 666–678 of 1,331.