Article 1 — Description
Construct reinforced soil nail anchors.
Article 2 — Materials
Provide materials in accordance with the following requirements.
2.1 Hydraulic Cement Concrete. Use materials that meet the requirements of Item 421, “Hydraulic Cement
Concrete.” Provide a neat cement or sand-cement mixture for the grout for soil nail anchors with a 7- day compressive strength of 3,000 psi. Determine grout strength by testing the grout used for the test soil nai l anchors in cubes in accordance with Tex -422-A or cylinders in accordance with Tex -418-A . Test further as directed or if the grout mixture is modified. Fly ash may be included in the grout. Do not use grout mixed in a mobile continuous volumetric mixer. Provide a grout mix with a minimum water- cement ratio of 0.4 and a minimum specific gravity of 1.85. Test for specific gravity in accordance with Tex -130-E . When a sand- cement mixture is used for grouting soil nail anchors, provide a grout mixture with a minimum slump flow of 20 in. Test the slump flow of the grout in accordance with ASTM C1611. The need for stiffer grout may arise when the hollow -stem auger drilling method is used or it is desired to control leakage of grout into highly permeable granular soils or highly fractured rock. In these instances, the Engineer may waive the requirements of slump flow testing.
2.2 Pneumatically Placed Concrete . Use materials that meet the requirements of Class II concrete in Item 431,
“Pneumatically Placed Concrete,” unless otherwise shown on the plans.
2.3 Reinforcing Steel . Use materials that meet the requirements of Item 440, “Reinforcement for Concrete.”
Provide epoxy -coated reinforcing steel bar of the size and grade shown on the plans for permanent walls. The minimum allowable epoxy coating thickness is 12 mils. Temporary walls are not required to provide epoxy -coated steel bars unless otherwise shown on the plans.
2.4 Bar Couplers . Provide bar couplers that develop the full nominal tensile capacity of the soil nail bars as
certified by the manufacturer.
2.5 Nail Centralizers. Provide expanded slit PVC centralizers with a minimum diameter of 1 in. less than the nail
hole. Wheel -type centralizers are not allowed.
Article 3 — Equipment
Furnish suitable equipment to drill the holes to the specified diameter, depth, and line. Provide a drill rig with an articulating head in the vertical plane and continuous flight augers. If an auger becomes worn to the degree that the drilled hole is less than the required diameter, remove the auger from service until it is repair ed and can provide a hole of at least the required diameter. Furnish a hydraulic jack and reaction frame for stressing the test anchors. Furnish a pressure gauge for the jack that is graduated in 75- psi increments or less. Furnish at least two dial gauges capable of measuring to 493 0.001 in. Calibrate the hydraulic jack and ram used together as a system, and furnish certified copies of load calibration curves for all jacks and ram systems to be used in the work. Calibrate the jack and ram as a unit no more than 6 mo. before starting work. Recalibrate stressing systems when directed or at least every 6 mo. Furnish a grout mixer and pump of enough capacity to place grout properly in the required quantities.
Article 4 — Construction
4.1 Soil Nail Wall Construction Plan . Submit a soil nail wall construction plan at least 30 days before beginning
construction. Begin soil nail wall construction once the construction plan submittal is accepted. Provide detailed project -specific information in the soil nail wall construction plan that includes the following: project start date, an overall description, and sequence of soil nail wall construction; list and sizes of excavation equipment, drill rigs (must have an articulating head in a vertical plane), cutting head ( e.g., auger and rock bit), tools, tremies, and grouting equipment; procedures for the sequence for the following items of work: excavations; drilling and grouting; soil nail and wall drainage system installation; and, if appropriate, facing construction; details of pneumatically placed concrete equipment and application , including mix process, shooting methods, and means for determining the thickness of the concrete applied; a nozzleman who is certified as an ACI Shotcrete Nozzleman; plan and methods for nail testing, both the verification tests and proof tests, with calibration certificates dated within 5 mo. of the submittal date; and other information shown on the plans or requested by the Engineer.
4.2 Drilling . Drill the hole so that its diameter is not smaller than the diameter shown on the plans or established
by test soil nail anchors. Control hole alignment so that it varies no more than 5° from the line specified on the plans. Furnish suitable drilling equipment and use methods suitable for the ground conditions. The use of drilling mud or other fluids to remove cuttings will not be allowed.
4.3 Grouting. Place the soil nail anchor with centralizers that are spaced no more than 8 ft. apart in the hole. Set
the centralizers to position the soil nail reinforcing bar within 1 in. of the center of the hole. To grout, advance the grouting pipe to the bottom of the hole, and leave it there until the hole is filled with grout and enough unsegregated grout is expelled at the top of the hole. Withdraw the pipe slowly while grouting continues, filling the void left by the grout pipe. Grout each nail within 8 hr. of the completion of drilling. Holes open longer than 8 hr. will be rejected and backfilled with grout. Grouting before insertion of the epoxy -coated bar into the hole is allowed only with approval. If approved, advance the grout pipe to the bottom of the hole and leave it there until the hole is filled with grout and enough unsegregated grout is expelled at the top of the hole. Withdraw the pipe slowly while grouting continues, filling the void left by the grout pipe. Insert the epoxy -coated bar with the centralizers attached and fill any void that is left from the insertion of the bar. Fill the hole completely to face of the cut. If caving or sloughing of the hole occurs that prevents open- hole grouting, furnish either hollow -stem auger equipment, placing the nail reinforcing bar and grout through the auger, or casing to support the sides of the excavation. Use grouting methods that result in complete filling of the hole at the ground surface. Methods may include placement of grout in multiple stages or other approved methods. Completely remove any device used to dam the front of the hole immediately after the grout takes an initial set. Record the following information pertinent to the grouting. Type of mixer Water-cement ratio Types of additives Type of cement Volume of grout 494 4.4. Soil Nail Anchor Test .
4.4.1 Verification Tests. Construct and test the soil nail anchors as shown on the plans. Test the soil nail anchors
before installing any production soil nail anchors. Do not use verification test nails as production soil nail anchors. Provide an adequate reaction pad large enough to resist the required load without sinking into the soil or shifting laterally during the test. Do not use a reaction pad that sinks into the soil more than 2 in. or that allows the free end of the soil nail reinforcing bar to move laterally more than 2 in. Failure to provide an adequate reaction pad will void the soil nail anchor test. Provide additional test soil nail anchors until an adequate reaction system is achieved. Furnish additional test soil nail anchors, required due to inadequate reaction pads, at no expense to the Department. Provide a reaction pad with a center opening larger than the hole diameter to ensure that no bridging or interaction occurs between the grout column and the reaction pad. Similarly, remove all pneumatically placed concrete, excess grout, or other foreign material to expose the full face of the grout column. Ensure the reaction system does not contact or interfere with the soil nail anchor reinforcing bar during the test. Conduct the following testing method. Apply test loads to soil nail anchors in increments of approximately 10% of the required test load shown on the plans. Hold each load increment long enough to obtain the gauge readings and to ensure that the readings have stabilized. Hold the final maximum test load for 10 min. Perform initial tensioning to take the slack out of the testing apparatus at 5% of the required test load , unless otherwise directed. Provide gauges that extend and retract freely and move smoothly throughout their range. Provide a rigid and secure system to s upport the gauge independently of the jack or reaction system. Meet the following v erification test nail acceptance criteria , unless otherwise shown on the plans . • The total creep movement is less than 0.04 in. during the final 10- min. reading increment. If movement exceeds this value, the Engineer may require an additional hold period of up to 60 min. with a maximum 0.08- in. total creep movement , including the movement from the original 10- min. hold. • The total measured movement at the maximum test load exceeds 80% of the theoretical elastic elongation of the unbonded length of the test nail . • A pullout limit state does not occur for the verification load shown on the plans. Pullout limit state is defined as a load level at which the test load cannot be further increased while there is continued movement of the test nail. Modify construction methods or procedures if the test soil nail anchors fail to provide the minimum pullout capacity shown on the plans. Install and test additional soil nail test anchors until adequate pullout capacity is achieved. Test soil nail anchors, in addition to the number shown on the plans, will be subsidiary to this Item. Install additional soil nail test anchors following the modified construction procedures , and test additional soil nail test anchors if the Contractor chooses to modify construction procedures after test soil nail anchors are completed and approved. This additional testing will be subsidia ry to this Item.
4.4.2 Proof Tests . Conduct p roof testing of production nails when shown on the plans. The number, length, and
target load of nails to be proof loaded must be satisfied and tested in accordance with the following criteria . The Engineer will deter mine the locations of each proof test nail. Completely grout the proof test nails. Proof testing may occur before the placement of pneumatically placed concrete for the temporary face. Leave a voided region around the nail head enough to allow free nail movement if proof testing is to occur after the placement of pneumatically placed concrete for the temporary facing. Provide at least a 2-in. clear zone around the grouted nail. Use a reaction system in accordance with Section 410.4.4.1., “Verification Tests .” 495 Follow proof nail loading sequence in accordance with Section 410.4.4.1., “Verification Tests” except use the required proof load shown on the plans. Meet the following proof test n ail acceptance criteria , unless otherwise shown on the plans . • The total creep movement is less than 0.04 in. during the final 10- min. reading increment. If movement exceeds this value, the Engineer may require an additional hold period of up to 60 min. with a maximum 0.08- in. total creep movement , including the movement from the original 10-min. hold. • The total measured movement at the maximum test load exceeds 80% of the theoretical elastic elongation of the unbonded length of the test nail. • A pullout limit state does not occur for the proof load shown on the plans. Pullout l imit state is defined as a load level at which the test load cannot be further increased while there is continued movement of the test nail. If the proof test nails fail, the Contractor’s engineer is responsible for redesigning the wall with supplemental soil nail anchors.
Article 5 — Measurement
5.1 Soil Nail Anchors. Soil nail anchors will be measured by the foot of acceptable soil nail anchor installed.
The soil nail anchor length measured is the length of the drilled and grouted hole as shown on the plans or modified by the Engineer.
5.2 Verification Tests. Verification tests will be measured by each complete load test satisfactorily performed,
reported, and accepted.
Article 6 — Payment
The work performed and materials furnished in accordance with this Item and measured as provided under “Measurement” will be paid for at the unit price bid in accordance with Section 410.5.1., “Soil Nail Anchors ,” and Section 410.5.2., “Verification Tests.” This price is full compensation for materials, equipment, testing, labor, tools, and i ncidentals.