SECTION 624: WIRE MESH FOR SLOPE STABILIZATION
624.1 Description
This Work consists of Roadway slope stabilization to restrain and channel rockfall.
624.2 Materials
624.2.1 Anchor Cable
The Contractor shall provide anchor cable with a diameter of a t least 1/2 inch. It shall be zinc-coated steel wire strand, common grade, Type 1 coating, in accordance with ASTM A 475. 624.2.2 Resin-Grouted Steel Bolt Systems The Contractor shall provide a resin-grouted steel bolt system with the best standard products of a manufacturer regularly engaged in the production of this type of installation and of the manufacturer’s latest approved design. The Contractor shall use resin-grouted steel bolts and hooked anchors with a minimum diameter of 3/4 inch. The Contractor shall use the headed type with flash forging. The Contractor shall use steel bolts with the following tensile pro perties: 1. Minimum yield strength: 43,000 psi; and 2. Minimum ultimate strength: 70,000 psi. The Contractor shall use steel bolts and hooked anchors manufa ctured from any of the grades of deformed bars specified in ASTM A 615. The Contracto r shall use steel bolts and hooked anchors specifically desi gned for resin grouting with lu gs, vertical ribs, and deformations to provide thorough mixing of the resin and to cen ter the steel bolts in the drilled holes.
624.2.2 1 Resin Cartridges
The Contractor shall provide the type of resin cartridges, as per the manufacturer’s recommendations, designed for a 0.9 inch diameter cartridge in a one (1) inch diameter hole with a 3/4 inch bolt or anchor.
624.2.3 Earth Anchor Systems
The Contractor shall use earth anchor systems with the best st andard products of a manufacturer regularly engaged in the production of this type o f installation and of the manufacturer’s latest approved design. The Contractor shall us e earth anchor systems designed for the conditions encount ered and as approved by the Project Manager.
624.2.4 Bearing Base Plates
The Contractor shall use bearing base plates that are six (6) inches square or six (6) inches diameter round plates in accordance with ASTM F 432.
624.2.5 Certification
The Contractor shall submit to the Project Manager for approva l any manufacturer’s certificates, literature, and s hop drawings at least two (2) we eks before beginning the Work. Section 624: Wire Mesh for Slope Stabilization Page 703 Shop drawings will, at a minimum, include spacing, bolt/anchor length, working load, and minimum required torque.
624.2.6 Slope Stabilization Wire and Wire Mesh
The Contractor shall provide tie wire and wire mesh in accorda nce with Section 602, “Slope and Erosion Protection Structures.”
624.2.6 1 Polyvinyl Chloride Coated Wire Mesh
In addition to Section 602, “Sl ope and Erosion Protection Stru ctures,” the Contractor shall use PVC-coated wire mesh and connec tions in accordance with the following: 1. Extrude the PVC coating onto the wire core before weaving th e coated wire; 2. Overall minimum diameter (ga lvanized wire core plus PVC coat ing) is 0.1338 inch; 3. Edging wire will be a galvanized wire core, with a diameter of at least 0.1338 inch (approximate U.S. gauge 10), coated with PVC, and having a mini mum overall diameter of 0.1638 inch; and 4. Lacing wire will be a galvaniz ed wire core, with a diameter of at least 0.0866 inch (approximate U.S. gauge 13.5), coated with PVC, and having a mi nimum overall diameter of 0.1166 inch.
624.2.6 2 PVC Coating
The Contractor shall provide pr otective PVC coating that resis ts the damaging effects of natural weather exposure or immersion in salt water and that do es not show any Material difference in its initial compound properties in accordance wit h Table 624.2.6.2:1, “PVC Coating Physical Property Requirements.” Table 624.2.6.2:1 PVC Coating Physical Property Requirements Property Required value Test method Initial Property Requirements — — Specific Gravity, kg/Dm3 1.30–1.35 ASTM D 792 Durometer Hardness 50–60 ASTM D 2240 Shore D — ISO 868 Volatile Loss, Maximum — ASTM D 1203 @ 105 °C for 24 h Two percent (2%) ISO 176 @ 105 °C for 240 h Six percent (6%) ASTM D 2287 Tensile Strength, kg/cm2, Minimum 210 ASTM D 412 Elongation, % 200–280 ASTM D 412 Modulus of Elasticity, kg/cm2, Minimum — — 100% of Elongation 190 ASTM D 412 Resistance to Abrasion, gm, Maximum 0.19 ASTM D 1242 – 95a Brittleness Temperature, °C, Maximum –30 BS 2782-104A Cold bend temperature +15 BS 2782-150B Section 624: Wire Mesh for Slope Stabilization Page 704 Table 624.2.6.2:1 PVC Coating Physical Property Requirements Cold flex temperature — — Creeping Corrosion, mm, Maximuma 25 — aPenetration of corrosion of the wire core from a square cut end when the specimen has been immersed for 2,000 h in a 50% solution of h ydrochloric acid 12 Be.
624.3 Construction Requirements
The Contractor shall prepare top and bottom of slopes by trenc hing. The Contractor shall scale slope faces in accordance with Sect ion 626, “Scaling of Rock Slopes,” before installing steel bolts/anchors and draping and anchoring the wire mesh.
624.3.1 Anchor Hole Preparation
The Contractor shall drill bore holes for steel bolts/anchors approximately perpendicular to the rock face, except in areas approved by the Project Manag er, incline the boreholes to a maximum of 30° off the perpendicular in order to intercept and seat the steel bolts/anchors in solid rock. Upon completion of drilling, the Contractor shall blow the dri lled holes clean with compressed air with an operating air pressure of at least 50 ps i introduced at the back of the hole. The Contractor shall use the manufacturer’s recommended hole d iameter for the steel bolts/anchors. The Contractor shall ensure that the clearance between the ste el bolt/anchor and borehole wall is from 1/8 inch to 3/16 inch.
624.3.2 Anchor Installation
The Contractor shall carefully follow the manufacturer’s recom mended installation procedures for steel bolts/anchors. During construction, the Contract or may reduce the center-to-c enter spacing in order to maximize anchorage by selective bolting/anchoring in sound rock or to eliminate large voids between the wire mesh and the slope face. The Contractor shall use steel bolts/hooked anchors that are a t least six (6) feet long. The Contractor shall ensure that the steel bolts extend at leas t one (1) foot into sound rock. As construction progresses, t he rock conditions encountered ma y require the lengths of the steel bolts/hooked anchors to be greater than the minimum l ength, so the Project Manager may direct varied lengths. If using varied lengths, the Depart ment will allow the Contractor to use steel couplings or other methods recommended by the manufac turer.
624.3.2 1 Tensioning and Testing of Steel Bolts and Earth Ancho rs
The Contractor shall tension steel bolts and earth anchors in accordance with the manufacturer's recommendations. The Contractor shall use a min imum torque of 200 lbf•ft, unless otherwise specified. Section 624: Wire Mesh for Slope Stabilization Page 705 After installation, test a randomly selected set of ten percen t (10%) of the bolts or anchors to confirm the specified working load. If more than on e third of these fail, the Contractor shall test all bolts/anchors. After replacing the failed bol ts and anchors, the Contractor s hall test another randomly selected set of ten percent (10%) of bolts and anchors, not inc luding those previously tested and Accepted. The Contractor shall repeat the procedure until obtaining the satisfactory results. The Contractor shall replace unacceptable bolts and anchors at no additional cost to the Department.
624.3.3 Installation of Wire Mesh If the Contract specifies, the Contractor shall use PVC-coated wire mesh.
The Contractor shall lap the wire mesh at least six (6) inches and securely bind the perimeter edges of wire mesh so that the joints formed by tying the selvedges have a minimum strength equal to that of the body of the mesh. The Contractor shall space ties, connectors, locking clips, or hog rings used for fastening edges four (4) inches apart or less. The Contractor may lace p erimeter edges with binding wire by tightly looping it through every mesh opening. The Contractor shall extend wire mesh down the face of the slo pe and anchor it to the face of the slope by resin-grout ed steel bolts or anchors, as r equired. The Contractor shall hold wire mesh in place by the bearing ba se plates to stretch it to the maximum and contour it to the existing surface. The Contractor shall anchor the wire mesh at the bottom to con tain loose debris and allow periodic maintenance and debris removal.
624.3.3 1 Alternate Anchoring Method
If specified in the Contract, the Contractor shall anchor wire mesh using anchor cable and hooked resin-grouted steel or earth anchors.
624.3.4 Site Maintenance
The Contractor shall maintain the Project area and keep it cle ar of falling rock and debris during construction and at Project completion. The Contractor shall dispose of waste and debris at locations approv ed by the Project Manager.
624.4 METHOD OF MEASUREMENT—Reserved
624.5 Basis of Payment
Pay Item Pay Unit Slope Protection Wire Mesh Square Yard Slope Protection Wire Mesh PVC-Coated Square Yard Resin-Grouted Steel Bolts Linear Foot Resin-Grouted Steel Anchors Linear Foot Section 624: Wire Mesh for Slope Stabilization Page 706 Earth Anchors Linear Foot Anchor Cable Linear Foot
624.5.1 Work Included in Payment
The following Work and items will be considered as included in the payment for the main items and will not be measured or paid for separately: 1. Trenching at the top and bottom of the slope; 2. Hauling and disposal of rocks and debris; and 3. Ties, lacing wire, clips , hog rings, plates, and other appur tenances. Section 626: Scaling of Rock Slopes Page 707