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1.0 Description The Work shall consist of constructing permanent SOIL SCREW™ Retention Wall System as specified herein and shown on the Plans. The Contractor shall furnish all labor, materials and equipment required for completing the Work. The Contractor shall select the method of excavation, drilling method and equipment, to meet the performance requirements specified herein. Soil nail walls are built from the top down in existing ground. The work shall include excavating in accordance with the staged lifts shown in the Plans; installing screw anchors to the specified minimum length and orientation indicated on the Plans; providing and placing drainage elements; placing shotcrete reinforcement; applying shotcrete facing over the reinforcement; attaching bearing plates and nuts; performing nail testing; and installing instrumentation (if required). Shotcrete facing and wall drainage construction is covered by the Shotcrete Facing and Wall Drainage Specification. CIP concrete facing construction (if required) is covered by the Standard Specifications and/or CIP Facing Special Provisions. Wall instrumentation (if required) is covered by the SOIL SCREW® Retention Wall System Instrumentation Specification. The term "soil nail" as used in these specifications, refers to a screw anchor. Soil properties, strength parameters, safety factors, design requirements and other criteria are shown on the Plans. In addition to the subsurface information presented in the Plans, Geotechnical Report(s) titled __________ are also available to bidders and can be obtained from __________. 1.1 Soil Nail Contractor’s Experience Requirements and Submittal - The soil nailing Contractor shall submit a project reference list verifying the successful construction completion of at least 3 permanent soil nail retaining wall projects during the past 3 years, totaling at least 10,000 square feet of wall face area and at least 500 permanent soil nails. Alternatively, experience of 2 projects using screw anchor tiebacks totaling 750 square meters over the past 3 years is acceptable. A brief description of each project with the Owner's name and current phone number shall be included. A Registered Professional Engineer employed by the soil nailing Contractor and having experience in the construction of permanent soil nail retaining walls on at least 3 completed projects over the past 3 years shall supervise the Work. The on-site supervisor and drill rig operators shall have experience installing permanent soil nails on at least 3 projects over the past 3 years. At least 30 calendar days before starting the wall, the soil nail Contractor shall submit 5 copies of the completed project reference list and a list identifying the supervising Engineer, drill rig operators, and on-site supervisors assigned to the project. The personnel list shall contain a summary of each individual's experience 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 1 calendar day after receipt of a complete submission. Work shall not be started nor materials ordered until the Engineer's written approval of the Contractor's 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. 1.2 Construction Site Survey - Before bidding the Work, the Contractor shall review the available subsurface information and visit the site to assess the site geometry, equipment access conditions, and location of existing structures and above-ground facilities. The Contractor is responsible for field locating and verifying the location of all utilities shown on the Plans prior to starting the Work. Maintain uninterrupted service for those utilities designated to remain in service throughout the Work. Notify the Engineer of any utility locations different from those shown on the Plans that may require nail relocations or wall design modification. Subject to the Engineer's approval, additional cost to the Contractor due to nail relocations and/or wall design modification resulting from utility locations different from shown on the Plans will be paid as Extra Work. Prior to start of any wall construction activity, the Contractor and Engineer shall jointly inspect the site to observe and document the pre-construction condition of the site, existing structures and facilities. During construction, the Contractor shall observe the conditions above the soil nail wall on a daily basis for signs of ground movement in the vicinity of the wall. Immediately notify the Engineer if signs of movements such as new cracks in structures, increased size of old cracks or separation of joints in structures, foundations, streets or paved and unpaved surfaces are observed. If the Engineer determines that the movements exceed those anticipated for typical soil nail wall construction and require corrective action, the Contractor shall take corrective actions necessary to stop the movement or perform repairs. When due to the Contractor's methods or operations or failure to follow the specified/approved construction sequence, as determined by the Engineer, the costs of providing corrective actions will be borne by the Contractor. When due to differing site conditions, as determined by the Engineer, the costs of providing corrective actions will be paid as Extra Work. 1.3 Construction Submittals - Upon approval of the soil nailing Contractor's qualifications submittal set forth in Section 1.1, submit 5 copies of the following information, in writing, to the Engineer for review and approval. Provide submittal item numbers 1 through 1D at least 15 calendar days prior to initiating the soil nail wall construction and submittal items 2 through 4 at least 15 calendar days prior to start of nail installation or incorporation of the respective materials into the Work:
The Engineer will approve or reject the Contractor's submittals within 15 calendar days after receipt of a complete submission. The Contractor will not be allowed to begin wall construction or incorporate materials into the work until the submittal requirements are satisfied and found acceptable to the Engineer. Changes or deviations from the approved submittals must be resubmitted for approval. No adjustments in contract time will be allowed due to incomplete submittals. 1.4 Pre-Construction Meeting - A pre-construction meeting will be scheduled by the Engineer and held prior to the start of wall construction. The Engineer, prime Contractor, soil nail specialty Contractor and geotechnical instrumentation specialist (if applicable) shall attend the meeting. The excavation Contractor, shotcreting Contractor and survey Contractor, if different than the prime or soil nail specialty contractor, shall also attend. 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, particularly those pertaining to wall excavation, nail installation and testing, excavation and wall alignment survey control, and shotcrete and CIP facing construction. Soil nail wall construction requires excavation in staged lifts and excavation in the vicinity of the wall face requires special care and effort compared to general earthwork excavation. The Contractor shall take this into account during bidding and shall consult the Wall Excavation and Measurement/Payment Sections of this Specification for details. 2.0 Materials Furnish materials new and without defects. Remove defective materials from the job site at no additional cost. Materials for soil nail structures shall consist of the following: Screw Anchors and Bolts: The screw anchors shall have a minimum ultimate tensile capacity of 70,000 lbs., and a minimum working torque capacity of 5500 foot-pounds, as manufactured by the A. B. Chance Company (Centralia, Missouri). The anchors shall have 8 inch diameter helices at 29-inch nominal spacing along their length. Connecting bolts for the screw anchors shall have a minimum ultimate double shear strength of 70,000 lbs. The manufacturer shall have in effect industry-recognized written quality control for all materials and manufacturing processes. All welding shall be done by welders certified under section 5 of AWS code D1.1.
Vertical Wall Drains - Provide as required and shown on the plans, prefabricated, fully wrapped geocomposite drains. The core, not less than 0.25 or more than 0.50 inches (0.6 to 1.2 cm) thick, shall be either a preformed grid or embossed plastic or a system of plastic pillars and interconnections forming a semi-rigid mat. The core material, when covered with filter fabric, shall be capable of maintaining a drainage void for the entire height of permeable liner. Preformed drains shall be no wider than 12 inches (30 cm) unless special methods are used to ensure adherence of the shotcrete to the fabrics and to preclude the fabrics from sagging under the weight of the shotcrete. They shall be suitably outletted or connected to a longitudinal drain at the bottom of the structure. When splicing of drains is required, full flow through the splice shall be maintained, and splices shall be suitably protected from damage and contamination during subsequent shotcreting. The shotcrete shall be of full thickness over the drain. 2.1 Materials Handling And Storage - Store cement to prevent moisture degradation and partial hydration. Do not use cement that has become caked or lumpy. Store aggregates so that segregation and inclusion of foreign materials are prevented. Do not use the bottom 6 inches of aggregate piles in contact with the ground. Store steel reinforcement on supports to keep the steel from contacting the ground. Do not ground welding leads to screw anchors. 3.0 Construction Requirements 3.1 Site Drainage Control - Provide positive control and discharge of all surface water that will affect construction of the soil nail retaining wall. Maintain all pipes or conduits used to control surface water during construction. Repair damage caused by surface water at no additional cost. Upon substantial completion of the wall, remove surface water control pipes or conduits from the site. Alternatively, with the approval of the Engineer, pipes or conduits that are left in place may be fully grouted and abandoned or left in a way that protects the structure and all adjacent facilities from migration of fines through the pipe or conduit and potential ground loss. The regional groundwater table is anticipated to be below the level of the wall excavation based on the results of the geotechnical site investigation. Localized areas of perched water or seepage may be encountered during excavation at the interface of geologic units or from localized groundwater seepage areas. Immediately contact the Engineer if unanticipated subsurface drainage structures are discovered during excavation. Suspend work in these areas until remedial measures meeting the Engineer's approval are implemented. Capture surface water runoff flows and flows from existing subsurface drainage structures independently of the wall drainage network and convey them to an outfall structure or storm sewer, as approved by the Engineer. Cost of remedial measures required to capture and dispose of water resulting from encountering unanticipated subsurface drainage structures will be paid for as Extra Work. 3.2 Excavation Coordinate the work and the excavation so the SOIL SCREW® Retention Wall System is properly constructed. Perform the wall construction and excavation sequence in accordance with the Plans and approved submittals. No excavation steeper than those specified herein or shown on the Plans will be made above or below the soil nail wall without written approval of the Engineer. 3.2.1 Excavation and Wall Alignment Survey Control - Unless specified otherwise, the Engineer will provide survey reference and control points at or offset along the top of wall alignment at approximate 30 foot intervals prior to starting wall excavation. The Contractor will then be responsible for providing the necessary survey and alignment control during excavation of each lift, locating and installing each nail within the allowable tolerances, and for performing the wall excavation and nail installation in a manner which will allow for constructing the shotcrete construction facing to the specified minimum thickness and such that the finish CIP structural facing can be constructed to the specified minimum thickness and to the line and grade indicated in the Plans. Where the as-built location of the front face of the shotcrete exceeds the allowable tolerance from the wall control line shown on the Plans, the Contractor will be responsible for determining and bearing the cost of remedial measures necessary to provide proper attachment of nail head bearing plate connections and satisfactory placement of the final facing, as called for on the Plans. 3.2.2 General Roadway Excavation - Complete clearing, grubbing, grading and excavation above and behind the wall before commencing wall excavation. Do not overexcavate the original ground behind the wall or at the ends of the wall, beyond the limits shown on the Plans. Do not perform general roadway excavation that will affect the soil nail wall until wall construction starts. Roadway excavation shall be coordinated with the soil nailing work, and the excavation shall proceed from the top down in a horizontal staged excavation lift sequence with the ground level for each lift excavated no more than mid-height between adjacent nail rows, as illustrated on the Plans. Do not excavate the full wall height to the final wall alignment as shown on the Plans but maintain a working bench of native material to serve as a platform for the drilling equipment. The bench shall be wide enough to provide a safe working area for the drill equipment and workers. Perform any rock blasting within 200 feet of the soil nail wall using controlled blasting techniques designed by a qualified blasting consultant or a Professional Engineer registered in the state where the blasting is taking place. Blasting shall not damage completed soil nail work or disrupt the remaining ground to be soil nailed or shotcreted. Repair damaged areas at no additional cost. 3.2.3 Soil Nail Wall Structure Excavation - Structure excavation in the vicinity of the wall face will require special care and effort compared to general earthwork excavation. The excavation Contractor should take this into account during bidding. Due to the close coordination required between the soil nail Contractor and the excavation Contractor, the excavation Contractor shall perform the structure excavation for the soil nail wall under the direction of the soil nail specialty Contractor. The structure excavation pay limits are shown on the Plans. Excavate to the final wall face using procedures that: (1) prevent over-excavation; (2) prevent ground loss, swelling, air slaking, or loosening; (3) prevent loss of support for completed portions of the wall; (4) prevent loss of soil moisture at the face; and (5) prevent ground freezing. Costs associated with additional thickness of shotcrete or concrete or other remedial measures required due to irregularities in the cut face, excavation overbreak or inadvertent over-excavation, shall be borne by the Contractor. The exposed unsupported final excavation face cut height shall not exceed the vertical nail spacing plus the required reinforcing lap or the short-term stand-up height of the ground, whichever is less. Complete excavation to the final wall excavation line and application of the shotcrete in the same work shift unless otherwise approved by the Engineer. Application of the shotcrete may be delayed up to 24 hours if the Contractor can show that the delay will not adversely affect the excavation face stability. A polyethylene film over the face of the excavation may reduce degradation of the cut face caused by changes in moisture. Damage to existing structures or structures included in the Work shall be repaired and paid by the Contractor where approval is granted for the extended face exposure period. At the Contractor's option, during each excavation lift, nails may be installed through a temporary stabilizing berm, as illustrated on the Plans. Purpose of the stabilizing berm is to prevent or minimize instability or sloughing of the final excavation face due to ground conditions and/or drilling action. The stabilizing berm geometry illustrated on the plans shows the top of berm extending horizontally out from the bottom front face of the overlying shotcrete a distance of 1 foot and cut down from that point to the base grade for that excavation lift at a slope not steeper than 1H:1V. The Contractor may use a different berm geometry than illustrated on the Plans, upon satisfactory demonstration that the different geometry provides satisfactory performance. Following the installation of nails in that lift, excavate the temporary stabilizing berm to the final wall face excavation line and clean the final excavation face of all loose materials, mud, and other foreign matter which could prevent or reduce shotcrete bond. Ensure that installed nails and corrosion protection are not damaged during excavation of the stabilizing berm. Repair or replace nails damaged or disturbed during excavation of the stabilizing berm, to the Engineer's satisfaction, at no additional cost. Alternative excavation and soil nail installation methods that meet these objectives may be submitted to the Engineer for review in accordance with the Submittals section. Excavation to the next level shall not proceed until nail installation, reinforced shotcrete placement, attachment of bearing plates and nuts and nail testing has been completed and accepted in the current lift. Shotcrete shall have cured for at least 72 hours or attained at least its specified 3-day compressive strength before excavating the next underlying lift. Excavating the next lift in less than 72 hours will only be allowed if the Contractor submits compressive strength test results, for tests performed by a qualified independent testing lab, verifying that the shotcrete mix being used will provide the specified 3-day compressive strengths in the lesser time. Notify the Engineer immediately if raveling or local instability of the final wall face excavation occurs. Unstable areas shall be temporarily stabilized by means of buttressing the exposed face with an earth berm or other methods. Suspend work in unstable areas until remedial measures are developed. 3.2.4 Wall Discontinuities - Where the Contractor's excavation and installation methods result in a discontinuous wall along any nail row, the ends of the constructed wall section shall extend beyond the ends of the next lower excavation lift by at least 10 feet. Slopes at these discontinuities shall be constructed to prevent sloughing or failure of the temporary slopes. If sections of the wall are to be constructed at different times, prevent sloughing or failure of the temporary slopes at the end of each wall section. 3.2.5 Excavation Face Protrusions, Voids or Obstructions - Remove all or portions of cobbles, boulders, rubble or other subsurface obstructions encountered at the wall final excavation face which will protrude into the design shotcrete facing. Determine method of removal of face protrusions, including method to secure remnant pieces left behind the excavation face and for promptly backfilling voids resulting from removal of protrusions extending behind the excavation face. Notify the Engineer of the proposed method(s) for removal of face protrusions at least 24 hours prior to beginning removal. Voids, overbreak or over-excavation beyond the plan wall excavation line resulting from the removal of face protrusions or excavation operations shall be backfilled with shotcrete or concrete, as approved by the Engineer. Removal of face protrusions and backfilling of voids or over-excavation is considered incidental to the work. Cost due to removal of unanticipated man-made obstructions will be paid as Extra Work. 3.3 Nail Installation Determine installation method necessary to achieve the nail pullout resistance(s) specified herein or on the Plans, in accordance with the nail testing acceptance criteria in the Nail Testing section. No installation of production nails will be permitted in any soil unit until successful pre-production verification testing of nails is completed in that unit and approved by the Engineer. Install verification test nails using the same equipment, methods, nail inclination and nail type as planned for the production nails. Perform pre-production verification tests in accordance with the Verification Testing Section prior to starting wall excavation and prior to installation of production nails in the specific lift in which the designated verification test nails are located. The number and location of the verification tests will be as indicated on the Plans or specified herein. Verification test nails may be installed through either the existing slope face prior to start of wall excavation, drill platform work bench, stabilization berm or into slot cuts made for the particular lift in which the verification test nails are located. Slot cuts will only be large enough to adequately accommodate the drill and test nail reaction setup. Subject to the Engineer's approval, verification test nails may also be installed at angle orientations other than perpendicular to the wall face or at different locations than specified, as long as the Contractor can demonstrate that the test nails will be installed into ground which is representative of the ground at the verification test nail locations designated on the Plans or herein. Install the production soil nails before the application of the reinforced shotcrete facing. At the Contractor's request and subject to the Engineer's written approval, the shotcrete facing may be placed before installing the nails. Provide a blockout through the shotcrete facing at drillhole locations using PVC pipe or other suitable material, to prevent damage to the facing during drilling. As part of the required construction submittals, provide the Engineer with acceptable structural design calculations demonstrating that the facing structural capacity will not be reduced and that the bearing plates are adequate to span the nail drillhole blockout through the construction facing. If this requires larger size bearing plates and/or additional reinforcement beyond that detailed on the Plans, the extra cost will be incidental. Where necessary for stability of the excavation face, the Contractor shall have the option of placing a sealing layer (flashcoat) of unreinforced shotcrete or steel fiber reinforced shotcrete or of installation of nails through a temporary stabilizing berm of native soil to protect and stabilize the face of the excavation per Section 3.2.3 Wall Structure Excavation. Cost shall be incidental to the Work. During installation of nails, the torque required to install the nail shall be recorded. The Engineer may add, eliminate, or relocate nails to accommodate actual field conditions. Cost adjustments associated with these modifications shall be made in accordance with the General Provisions of the Contract. The cost of any redesign, additional material, or installation modifications resulting from actions of the Contractor shall be borne by the Contractor. 3.3.1 Installation - The installation of the soil nails shall be made at the locations, orientations, and lengths shown on the Plans or as directed by the Engineer. Select installation equipment and methods suitable for the ground conditions described in the geotechnical report and shown in the boring logs. Select anchors required to develop the specified pullout resistance. It is the Contractor's responsibility to determine the final anchor configuration required to provide the specified pullout resistance. Where hard drilling conditions such as rock, cobbles, boulders, or obstructions are described elsewhere in the contract documents or project Geotechnical Report, other suitable drilling equipment and anchors capable of drilling through such materials, will be used. 3.3.2 Nail Installation Tolerances - Nails shall not extend beyond the right-of-way or easement limits shown on the Plans. Nail location and orientation tolerances are:
Soil nails which do not satisfy the specified tolerances due to the Contractor's installation methods, will be replaced at no additional cost. Nails which encounter unanticipated obstructions during drilling shall be relocated, as approved by the Engineer. Cost of drilling new nails abandoned due to unanticipated obstructions will be paid as Extra Work. 3.4 Nail Testing Perform both verification and proof testing of designated test nails. Perform pre-production verification tests on sacrificial test nails at locations shown on the Plans or listed herein. Perform proof tests on production nails at locations selected by the Engineer. Required nail test data shall be recorded by the Engineer. Do not perform nail testing until the shotcrete facing has cured for at least 72 hours and attained at least its specified 3-day compressive strength. Testing in less than 72 hours will only be allowed if the Contractor submits compressive strength test results for tests performed by a qualified independent test lab verifying that the shotcrete mix being used will provide the specified 3-day compressive strength in the lesser time. Alternatively, soil nails may be tested immediately after installation without a shotcrete facing, as long as precautions to maintain face stability are made (i.e., temporary lagging, etc.). 3.4.1 Proof Test Nail Unbonded Length - Provide lengths of smooth extensions without helices for each test nail. Isolate the test nail bar from the shotcrete facing and/or the reaction frame used during testing. Isolation of a test nail through the shotcrete facing shall not affect the location of the reinforcing steel under the bearing plate. Submit the proposed test nail isolation methods, and the location and length of smooth extensions and test nails prior to testing to the Engineer for review and approval in accordance with the Submittals section. 3.4.2 Testing Equipment - Testing equipment shall include dial gauges, dial gauge support, jack and pressure gauge, electronic load cell, and a reaction frame. The load cell is required only for the creep test portion of the verification test. Provide description of test setup and jack, pressure gauge and load cell calibration curves in accordance with Submittals section. Design the testing reaction frame to be sufficiently rigid and of adequate dimensions such that excessive deformation of the testing equipment does not occur. If the reaction frame will bear directly on the shotcrete facing, design it to prevent cracking of the shotcrete. Independently support and center the jack over the nail bar so that the nail does not carry the weight of the testing equipment. Align the jack, bearing plates, and reaction frame with the nail such that unloading and repositioning of the equipment will not be required during the test. Apply and measure the test load with a hydraulic jack and pressure gauge. The pressure gauge shall be graduated in 50 psi increments or less. The jack and pressure gauge shall have a pressure range not exceeding twice the anticipated maximum test pressure. Jack ram travel shall be sufficient to allow the test to be done without resetting the equipment. Monitor the nail load during verification tests with both the pressure gauge and the load cell. Use the load cell to maintain constant load hold during the creep test load hold increment of the verification test. Measure the nail head movement with a dial gauge capable of measuring to .001 inch. The dial gauge shall have a travel sufficient to allow the test to be done without having to reset the gauge. Visually align the gauge to be parallel with the axis of the nail and support the gauge independently from the jack, wall, or reaction frame. Use two dial gauges when the test setup requires reaction against a soil cut face. One dial gauge should measure movement of the reaction relative to the soil face, and one relative to the reaction frame. 3.4.3 Pre-production Verification Testing of Sacrificial Test Nails - Pre-production verification testing shall be performed prior to installation of production nails to verify the Contractor's installation methods and nail pullout resistance. Perform pre-production verification tests at the locations and elevations shown on the Plans or herein, and per Nail Installation Section 3.3, unless otherwise approved by the Engineer. Perform a minimum of two verification tests in each different soil unit and for each different drilling method proposed to be used, at each wall location. Verification test nails will be sacrificial and not incorporated as production nails. Black steel anchors can be used for the sacrificial verification test nails. Develop and submit the details of the verification testing arrangement including the method of distributing test load pressures to the excavation surface (reaction frame), and reaction frame dimensioning to the Engineer for approval in accordance with Submittals section. Construct verification test nails using the same equipment, installation methods, nail inclination, and drilling equipment as planned for the production nails. Changes in the installation method may require additional verification testing as determined by the Engineer and shall be provided at no additional cost. Payment for additional verification tests required due to differing site conditions, if determined by the Engineer, shall be per the contract unit price. Test nails shall have lengths of smooth extensions in addition to the test nail with helices. The length of the smooth extensions within the test nail shall be at least 3 feet. The number of helices on the test nail shall be determined based on the production nail strength and helix configuration such that the allowable soil nail structural load is not exceeded during testing, but shall not be less than 3. The allowable soil nail structural load during testing shall not be greater than 80 percent of the rated minimum ultimate strength of the nail. The Contractor shall provide larger verification test soil nails, if required, to safely accommodate the 3-helix minimum and testing to 1.5 times the allowable pullout resistance per helix, at no additional cost. The Design Test Load (DTL) shall be determined by one of the following two methods. The first method is based on ultimate pullout capacity and is explained below. The second method is based on the nail with the highest load as determined by the internal and compound stability analysis.
If the Design Test Load (DTL) is based on the internal and compound stability analysis, DTL should be equal to the highest nail load determined by said analysis, but should never exceed 0.49 times the allowable soil nail structural load. Verification test nails shall be incrementally loaded to a maximum test load of 150 percent of the Design Test Load in accordance with the following loading schedule. The soil nail movements shall be recorded at each load increment.
The alignment load (AL) should be the minimum load required to align the testing apparatus and should not exceed 20 percent of the Design Test Load (DTL). The alignment load (AL) should be released to 5 percent, and then dial gauges should be set to "zero." Each load increment shall be held for at least 10 minutes. The verification test nail shall be monitored for creep at the 1.50 DTL load increment. Nail movements during the creep portion of the test shall be measured and recorded at 1 minute, 2, 3, 5, 6, 10, 20, 30, 50, and 60 minutes. The load during the creep test shall be maintained within 2 percent of the intended load by use of the load cell. 3.4.4 Proof Testing of Production Nails - Perform proof testing on 3 percent (1 in 33) of the production nails in each nail row or minimum of 1 per row. The locations shall be designated by the Engineer. A verification test nail successfully completed during production work shall be considered equivalent to a proof test nail and shall be accounted for in determining the number of proof tests required in that particular row. Production proof test nails shall have lengths of smooth extensions in addition to the soil nail with helices. The temporary smooth extension length of the test nail shall be at least 3 feet. The number of helices shall be determined based on the allowable design load not being exceeded during testing, but shall not be less than 3. The allowable soil nail structural load during testing shall not be greater than 80 percent of the rated minimum ultimate strength for the soil nail. The minimum length of proof tested production nails is 10 ft. The Design Test Load (DTL) shall be determined by one of the following two methods. The first method is based on ultimate pullout capacity and is explained below. The second method is based on the nail with the highest load as determined by the internal and compound stability analysis.
If the Design Test Load (DTL) is based on the internal and compound stability analysis, DTL should be equal to the highest nail load determined by said analysis, but should never exceed 0.49 times the allowable soil nail structural load. Proof tests shall be performed by incrementally loading the proof test nail to a maximum test load of 150 percent of the Design Test Load (DTL). The nail movement at each load shall be measured and recorded by the Engineer in the same manner as for verification tests. The test load shall be monitored by a jack pressure gauge with a sensitivity and range meeting the requirements of pressure gauges used for verification test nails. At load increments other than maximum test load, the load shall be held long enough to obtain a stable reading. Incremental loading for proof tests shall be in accordance with the following loading schedule. The nail movements shall be recorded at each load increment.
The alignment load (AL) should be the minimum load required to align the testing apparatus and should not exceed 5 percent of the Design Test Load (DTL). Dial gauges should be set to "zero" after the alignment load has been applied. All load increments shall be maintained within 5 percent of the intended load. Depending on performance, either 10 minute or 60 minute creep tests shall be performed at the maximum test load (1.5 DTL). The creep period shall start as soon as the maximum test load is applied, and the nail movement shall be measured and recorded at 1 minute, 2, 3, 5, 6, and 10 minutes. Where the nail movement between 1 minute and 10 minutes exceeds .08 inches, the maximum test load shall be maintained until the soil nail movement is less than .08 inches for any one log increment (i.e., 2 minutes and 20 minutes, etc.). 3.4.5 Test Nail Acceptance Criteria - A test nail shall be considered acceptable when the following criteria are met: 1. For verification tests, a total creep movement of less than .08 inches per log cycle of time between the 6 and 60 minute readings is measured during creep testing, and the creep rate is linear or decreasing throughout the creep test load hold period. 2. For proof tests, a total creep movement of less than .08 inches is measured between the 1 and 10 minute readings, or a total creep movement of less than .08 inches is measured between the subsequent log cycles, and the creep rate is linear or decreasing throughout the creep test load hold period. 3. For proof and verification tests, a pullout failure does not occur at the maximum test load. Pullout failure is defined as the load at which attempts to further increase the test load simply result in continued pullout movement of the test nail. The pullout failure load shall be recorded as part of the test data. Successful proof tested nails meeting the above test acceptance criteria may be incorporated as production nails, provided that the number of helices on the test nail is equal to or greater than the scheduled production nail length. If the production proof test nail does not meet this criteria, it shall become sacrificial and shall be replaced with an additional production nail installed at no additional cost. 3.5 Test Nail Rejection If a test nail does not satisfy the acceptance criterion, the Contractor shall determine the cause. 3.5.1 Verification Test Nails - The Engineer will evaluate the results of each verification test. Installation methods which do not satisfy the nail testing requirements shall be rejected. The Contractor shall propose alternative methods and install replacement verification test nails. Replacement test nails shall be installed and tested at no additional cost. 3.5.2 Proof Test Nails - The Engineer may require the Contractor to replace some or all of the installed production nails between a failed proof test nail and the adjacent passing proof test nail. Alternatively, the Engineer may require the installation and testing of additional proof test nails to verify that adjacent previously installed production nails have sufficient load carrying capacity. Contractor modifications may include, but are not limited to; the installation of additional proof test nails, modifying the installation method; reducing the production nail spacing from that shown on the Plans and installing more production nails at a reduced capacity; or installing longer production nails if sufficient right-of-way is available, and the pullout capacity behind the failure surface controls the allowable nail design capacity. The nails may not be lengthened beyond the temporary construction easements or the permanent right-of-way shown on the Plans. Installation and testing of additional proof test nails or installation of additional or modified nails as a result of proof test nail failure(s) will be at no additional cost. 3.6 Nail Installation Records - Records documenting the soil nail wall construction will be maintained by the Engineer, unless specified otherwise. The Contractor shall provide the Engineer with as-built drawings showing as-built nail locations and as-built shotcrete facing line and grade within 5 days after completion of the shotcrete facing, and as-built CIP facing line and grade within 5 days after completion of the CIP facing. 4.0 Method of Measurement The unit of measurement for production soil nails will be per lineal foot. The length to be paid will be the length measured along the bar centerline from the back face of shotcrete to the bottom tip end of nail bar as shown on the Plans. No separate measurement will be made for proof test nails, which shall be considered incidental to production nail installation. Specified verification test nails will be measured on a unit basis for each verification test successfully completed. Failed verification test nails or additional verification test nails installed to verify alternative nail installation methods proposed by the Contractor will not be measured. Structure Excavation for Soil Nail Wall will be measured as the theoretical plan volume in cubic meters within the structure excavation pay limits shown on the Plans. This will be the excavation volume within the zone measured from top to bottom of shotcrete wall facing and extending out 6 feet horizontally in front of the plan wall final excavation line. Additional excavation beyond the plan wall final excavation line resulting from irregularities in the cut face, excavation overbreak or inadvertent excavation, will not be measured. General roadway excavation will not be a separate wall pay item, but will be measured and paid as part of the general roadway excavation including haul pay item. The final pay quantities will be the design quantity increased or decreased by any changes authorized by the Engineer. 5.0 Basis of Payment The accepted quantities of soil nails and soil nail wall structure excavation will be paid for at the contract unit prices. Payment will be full compensation for all labor, equipment, materials, material tests, field tests and incidentals necessary to acceptably fabricate and construct the soil nails and perform the structure excavation, including the excavation and wall alignment survey control, for the soil nail wall(s) in accordance with all requirements of the contract. Payment will be made for each of the following bid items included in the bid form:
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0.49 allowable soil nail structural
load (Kips)
