Section 266 — Anchored Wire Mesh System

Description

266.01This work consists of providing and installing an anchored wire mesh system.

266.02Conform to the following Subsections: Material Anchor nails 722.05 Anchor plates 717.01(h) High tensile stren gth steel wire mesh 710.10(d)(2) Non-shrink grout 701.04(b)(2) Rockfall protection hardware 717.01(f) Rockfall protection nuts and washers 717.01(g) Turf reinforcement mat 713.18 Water for cementitious materials 725.01(a) Wire mesh fastener 710.09(c) Wire rope 709.03 Wire rope anchors 722.07(b)

Construction Requirements

266.03Qualifications. Provide an on- site supervisor with experience installing anchored mesh systems, and drill operators with experience installing ground anchors. A t least 21 days before starting rockfall protection work, submit the following for approval:

(a)On-site supervisor. A résumé describing experience on at least three projects installing anchored mesh systems within the past 3 years. Include project names, locations, and contact information for project owners;

(b)Drill operators. A résumé describing experience installing at least 1000 linear feet of anchor nails for anchored wire mesh systems within the past 3 years. Include project names, locations, and contact information for project owners ;

(c)Rope supported laborers. A r ésumé for rope supported laborers conforming to Subsection 262.02; and

(d)High tensile strength steel wire mesh suppliers. Include the following :

(1)Evidence showing the manufacturer has at least 5 years ’ experience manufacturing the specified products used in similar system applications and capacities. Include details of the manufacturer’s testing procedures and certification of a QA program; and

(2)Include summaries of at least 5 past projects with similar site conditions anchored wire systems were installed using the su pplier’s high tensile strength steel wire mesh. Include owner names and contact information.

266.04Submittals. At least 21 days before starting anchored wire mesh installation work , submit the following according to Subsection 104.06:

(a)Materials. Identify the high tensile strength steel wire mesh suppliers, and submit the following:

(1)An inclusive list with brochures and data sheets for system appurtenances to be used. Include the high tensile strength steel wire mesh, anchor nails, anchor plates, grout, lacing wire rope, wire mesh fastener, wire rope thimbles, ferrules, and other fastening hardware ; and

(2)At least two samples of each available color and texture for the turf reinforcement mat in a range of earth -tone color s representative of the adjacent landscape.

(b)Equipment.

(1)List of equipment to be used for anchored wire mesh installation, including equipment capacities and intended uses; and

(2)Calibration data, including a graph of torque versus tension for each torque wrench to be used. Include certifications showing calibration testing was conducted by an independent laboratory within 90 days of the date submitted.

(c)Work plan.

(1)A description of safety procedures minimizing exposure to hazardous and potentially hazardous conditions to the public, construction personnel, and equipment. Include temporary rockfall mitigation measures, special designs, and installation procedures deemed necessary to safely perform the rockfall protection work ;

(2)A list of materials, devices, and equ ipment used, and the methods that will be incorporated to protect existing facilities (underground, on the ground surface, and above -ground) and minimize impacts to the environment according to Section 107;

(3)A list of equipment and methods for installing the high -tensile strength steel wire mesh system including temporary anchoring;

(4)Methods and equipment for installing and connecting adjacent wire mesh panels and attaching them to temporary supports. Explain how mesh panels w ill be placed on the slope in a top -down method. Detail how panels overlap on the slope to maintain direct contact with the slope to prevent bulges or loose areas in the finished mesh ;

(5)Methods and equipment for drilling, grouting, and attaching anchoring boundary ropes and seam ropes;

(6)Methods and equipment for drilling, grouting, and installing anchor nails. Describe how anchor plates for the mesh system will be installed to obtain direct contact with the ground ;

(7)Methods to ensure borehole stability during excavation and grout placement in holes. If open joints, seams, or loose material is encountered, the methods, equipment, and materials used to control excessive grout injection volumes ; and

(8)Details for installing, stressing, and testing anchor nails.

266.05Installation.

(a)General. Provide an anchored wire mesh system that utilizes rock and soil reinforcement with anchor plates and a homogenous high- tensile -strength steel wire mesh consisting of a single - component wire type installed into direct c ontact with the slope to be stabilized. Perform safety scaling that the Contractor deems necessary according to Section 262. Before installing anchor wire mesh systems, complete work required according to Sections 260, 262, and 267, and other on-slope rock stabilization work as applicable. Repair galvanized finishes according to Section 563. If applicable, treat exposed steel surface according to Section 563. Provide uniform high- tensile strength steel wire mesh to construct the anchored wire mesh syst em installation. Complete the portion of the roadway cut in overburden soils according to Section 204 before placing the anchored wire mesh system. Minimize bridging mesh over exposed gaps and protruding boulders between anchors if present and maximize the wire mesh fabric contact with the ground surface. Remove mesh bulges or loose mesh that is not in contact with the surface by removing and resetting the mesh. Do not twist, pinch, or fold mesh together to tighten loose mesh or bulged mesh. Do not pinch, crush, or damage mesh or turf reinforcement mat under the anchor plate or in the annulus space between the plate and anchor nail. Additional anchor nails may be required to remove areas of loose mesh. If shown i n the plans , place a permanent turf reinforcement mat, type 5.C between the natural slope and the steel wire mesh according to Section 629. Secure the turf reinforcement mat to the slope face according to Su bsection 629.06(a)(1) or 629.06(a)(3) . Provide a permanent turf reinforcement mat with an approved color and texture.

(b)Wire mesh installation. Install wire mesh panels at the locations shown in the plans. Construct the anchored wire mesh system from the top down following the manufacturer’s installation guide. Extend the anchor nails and wire mesh at least three rows of mesh openings above the cr est of the slope. The wire mesh should be temporarily secured at the top of the slope to facilitate the installation procedure. Construct required temporary anchoring according to the approved submittal plan. No equipment operation is allowed on slope are as after wire mesh has been placed. Overlap adjacent wire mesh panels at least 3 inches to provide at least one mesh opening of overlap between panels. Increase the wire mesh overlap as necessary to fully cover the required slope area shown in the plans. L ace mesh panel side seams to an adjacent panel using a ¼ -inch diameter lacing wire rope or connect panels with wire mesh fasteners meeting the mesh manufacturer’s recommendations. If the overlap between panels is too great to fully secure panel edges with a single lacing wire rope, use additional lacing wire ropes to secure panel edges or multiple rows of wire mesh fasteners. Secure both ends of lacing wire rope installations by looping the end of the rope back onto itself and fastening it with wire rope clips according to the manufacturer’s specifications. Anchor wire mesh installations so they conform to the slope surface as much as practical. Place a ½ -inch diameter boundary rope along edges of the anchored wire mesh. Anchor the boundary rope at the end of each boundary rope with additional anchor nails as needed and connect the ends of boundary rope to the anchor nails according to the manufacturer’s recommendations. More than 4 boundary ropes may be required depending on the final shape of the anchored m esh area and arrangement of the anchor nails. Attach boundary ropes to the wire mesh and anchor plates according to the manufacturer’s recommendations. Diagonal cutting of the high tensile strength mesh is not allowed. Remove required temporary anchoring according to the approved submittal plan.

(c)Anchor nail installation. Anchor nail installations are required for the mesh system. The areas that will receive anchor nails are shown in the plans along with the general pattern for the anchors. The pattern shown in the plans indicates the estimated number of anchors for the anchored wire mesh system. The actual pattern constructed will be adjusted to fit the slope shape and stabilization requirements as directed. Schedule a test installation to demonstrate procedure for anchor nail installation and testing. Requirements for the anchor nail installation are as follows:

(1)For each anchor nail, drill a minimum 3- inch diameter hole perpendicular to the slope surface. Over -drill each hole at least 6 inches beyond the required anchor length. Refer to plans for the minimum depth of anchor nails.

(2)Install anchor nails and grout according to the manufacturer’s recommendations. Use positive displacement grout pumps according to Subsection 256.07(b)(1) . Control grout pressures to avoid ground heaving or fracturing, and fill grout tube with grout if it remains in the hole. Flush surplus water and diluted grout from lines before injection and replace leaky fittings before continuing grouting operations. Clean excess grout off rock surfaces, anchor nails, and bearing plates. Perform QC of the grout by performing minimum compressive strength. Record the quantity of injected grout and the grout pressure for each installation. Notify the CO of grout quantity overruns including the reason for the overrun and proposed actions to minimize future overruns. Obtain approval for alternative grouting methods.

(3)Excavate as shown in the plans around each nail head to ensure optimal load transfer from the anchor nail to the anchor plate to the wire mesh fabric. Install anchor plates, washers, nuts, and associated hardware according to the manufacturer’s recommendations and the plans.

(4)Tension each anchor nail no more than one week after completing grouting. Tension in th e anchor nail with a calibrated torque wrench to loads shown in the plans. If the tension load cannot be achieved, replace the anchor nail with an additional nail installed in a separate hole. Additional anchors may be needed to supplement the anchor nail spacing patterns shown in the plans to accommodate slope geometry. Obtain approval for all anchor locations.

(5)Lock off each anchor to the specified design load capacity as shown in the plans.

266.06Acceptance. See Table 266-1 for sampling, testing, and acceptance requirements. Material for the anchored wire mesh system installations will be evaluated under Subsections 106.02 and 106.03. Construction and erection of anchored wire mesh installations will be evaluated under Subsections 106.02 and 106.04. Submit a production certification for wire ropes and anchor nails. Drain holes in rock will be evaluated under Section 267. Rock bolts and dowels will be evaluated under Section 260. Safety scaling will be evaluated under Section 262. Treating exposed steel surfaces, treating galvanized steel field cuts, and repairing damaged galvanizing will be evaluated under Section 563.

Measurement

266.07Measure the Section 266 pay items listed in the bid schedule according to Subsection 109.02 and the following as applicable: When measuring anchored wire mesh system pay items by the square yard, measure the completed in place work performed on the ground surface, excluding overlaps and areas trimmed off. Do not measure anchor nails required for the anchored wire mesh. Measure additional anchors as described under Subsection 266.05(a) per each additional anchor installed.

Payment

266.08The accepted quantities will be paid at the contract price per unit of measurement for the Section 266 pay items listed in the bid schedule. Payment will be full compe nsation for the work described in this Section. See Subsection 109.05. Table 266-1 Sampling, Testing, and Acceptance Requirements

Material or

Product

(Subsection) Type of

Acceptance

(Subsection) Characteristic Category Test Methods

Specifications Sampling

Frequency Point of

Sampling Split

Sample Reporting

Time Remarks

Production

Non-shrink

grout (701.04(b)(2) ) Measured & tested for conformance (106.04 ) Flow – ASTM C939 1 per mix design

Source of

Material Yes, if

requested Within 24 hours after completion of test –

Compressive

strength (3 -day & 7-day) – ASTM C109 1 set from each batch of grout Source of

Material Yes, if

requested Within 24 hours after completion of test –

Proof test for

anchor nails Measured & tested for conformance (106.04) Deformation – Subsection

266.05(c)(4) Each nail Installation No Within 24 hours after completion of test –