SECTION 212 — GEOTEXTILES


212.1 DESCRIPTION — This work is the furnishing and installing of geotextiles, for the class specified.


212.2 MATERIAL — Use geotextiles meeting the requirements of Section 735 for the specified class and type.
For bedding use any open-graded stone meeting the requirements of Type C or better aggregate, as specified in Section 703.2, except that No. 2A or No. 10 coarse aggregate will not be permitted.
Use steel securing pins, 18 inches long x 3/16-inch in diameter, pointed at one end, and with a 1 1/2-inch washer head at the other end. If permitted, alternate securing devices may be used. Certify as specified in Section 106.03(b)3.
Use cover material, as specified or indicated.


212.3 CONSTRUCTION — As shown on the Standard Drawings, and as follows:

(a) General. Remove and replace fabric areas damaged during construction. Lap or sew replaced fabric, as specified for the class of fabric used. No traffic or construction equipment will be permitted on the fabric.

(b) Class 1 — Subsurface Drainage. Provide smooth side and bottom trench surfaces so the fabric does not bridge depressions in the soil and is not damaged by rock projections. Use fabric of a width to permit a minimum trench-width overlap across the backfill at the trench top. Lay the fabric flat in the prepared trench without stretching. Lay the top of the fabric back on the sides to allow for the placement of the aggregate backfill and pipe. Overlap ends of rolls an amount equal to the trench width prior to fabric placement. Where pockets or cavities occur in the trench bottom or sides, fill them with acceptable granular material to prevent distortion or damage to the fabric.
Backfill aggregate and install pipe in a manner to prevent damage to the fabric. Compact aggregate backfill and overlap the fabric across the trench top. Do not allow the fabric to be exposed for more than 2 weeks without covering with backfill.

(c) Class 2 — Erosion Control. Use Type A or Type B fabric, as indicated or specified. Remove vegetation, large stones, and other debris from the area to be protected and grade the surface to a relatively smooth condition. Undercut areas of soft material and replace with acceptable compacted material, as directed.
Place the fabric on the prepared area in a loose and unstretched condition to minimize shifting, puncturing, or tearing the fabric. Join adjacent edges and ends with a folded seam and sew using a single lock-type stitch seam or a double chain type stitch seam equivalent in strength to the fabric tensile strength. Sewing may be done on-site or by the manufacturer. Overlap only if permitted and then as directed. Provide a minimum overlap of 1 foot. For underwater placement, overlap a minimum of 3 feet. Offset adjacent roll ends a minimum of 5 feet when lapped.
Lay and overlap the fabric in the direction shown in Table A for the indicated use.
If permitted, anchor the fabric in place by securing pins or other acceptable methods, along sewn seams or overlaps, at the spacing shown in Table B. Also place securing pins on a maximum 6 foot grid on the unsewn or unlapped portions of the fabric.
Where slopes are flatter than 6:1, if permitted, securing pins may be eliminated, provided that aggregate, rock or other acceptable means are used to secure the fabric.


TABLE A
Fabric Placement
Operation
Slope Stabilization
Runoff Protection and
Internal Seepage Piping
Stream Slope
Protection
Wave Protection
Direction of fabric layingUp and down (parallel with slope direction)Parallel to stream flows from upstream to downstreamUp and down (parallel with slope
direction
Overlap directionUpslope over downslopeUpstream over downstream and upslope over downslopeUpslope over downslope
TABLE B
Securing Pin Spacing *
Slope
Steeper than
3:1
4:1
Flatter than
4:1
Pin Spacing along sewn seams or overlaps
2 feet
3 feet
5 feet

* Place additional pins to secure unlapped portions, as specified.

Cover the fabric with the covering material as soon as possible, so the fabric is not exposed for more than 4 weeks for Type A and 2 weeks for Type B. Prevent slippage of the cover material on the fabric.
Do not drop rocks, 2 feet or larger in dimension, directly on the fabric from a height greater than 1 foot. Do not allow the rock placement procedure to puncture or damage the fabric. A minimum 6-inch layer of bedding stone and a greater drop-height combination may be used if the combination produces the placement, thickness, gradation and fabric integrity requirements, and if permitted.

(d) Class 3 — Sedimentation Control. Use Type A or B fabric, as indicated or specified. Install in accordance with Section 865.3.

(e) Class 4 — Layer Separation. Use for the separation of subgrade and other layers. Place the fabric on a normally prepared subgrade area attending the full width of the sub-base layer being protected. Place fabric in a loose and unstretched condition to minimize shifting, puncture, and/or tearing. Overlap fabric roll-ends and edges a minimum of 12 inches with adjacent material. Place subbase material within 2 weeks after placement of fabric to minimize exposure. Place sub-base material in a manner to minimize slippage of the fabric. If excessive slippage occurs, use steel securing pins as specified in Section 212.2 at a maximum spacing of 6 feet.


212.4 MEASUREMENT AND PAYMENT —

(a) Geotextiles, Class 1. Linear Foot
Measured by the linear foot of trench.

(b) Geotextiles, Class 2. Square Yard
For the type indicated or specified.

(c) Geotextiles, Class 3. Linear Foot
For the type indicated or specified. Measured by the linear foot of sedimentation device.

(d) Geotextiles, Class 4. Square Yard

No Supplement

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