ITEM 715 – GEOTEXTILES

715.1 Description

This Item covers geotextile fabrics for use in subsurface drainage, hydraulic filter, erosion control, sediment control, pavement structures as a waterproofing and stress relieving membrane, and as a permeable separator to prevent mixing of dissimilar materials such as foundations and select fill materials.

715.2 Physical and Chemical Requirements

Fibers used in the manufacture of geotextiles, and the threads used in joining geotextiles by sewing, shall consist of long-chain synthetic polymers, composed of at least 85 percent by mass polyolefins, polyesters, or polyamids. They shall be formed into a network such that the filaments or yarns retain dimensional stability relative to each other, including selvedges. These materials shall conform to the physical requirements of Table 1 for the indicated application. Guidelines for the survivability levels referred to under “Separation” in Table 1 are included in Table 2.

715.3 Sampling and Testing

The product shall be subject to sampling and testing. Sampling shall be done in accordance with ASTM D 4354 and testing procedures shall be in accordance with the methods given in Table 1.

715.4 Certification

715.4.1 Manufacturer’s Certificate

The manufacturer shall file with the purchaser a certificate stating the name of the manufacturer, the chemical composition of the filaments or yarns, and other pertinent information so as to fully describe the geotextile. The manufacturer shall include in the certificate a guarantee stating that the geotextile that is furnished meets the requirements of the specification. The certificate shall be attested to by a person having legal authority to bind the company. Either mismarking or misrepresentation by the manufacturer shall be reason to discontinue acceptance under these specifications. Notice sent to the manufacturer by the purchaser regarding the discontinuance of acceptance will be considered to be notice to all wholesalers, jobbers, distributors, agents and other intermediaries handling the manufacturer’s product.

715.5 Quality Control

The geotextile manufacturer is responsible for establishing and maintaining a quality control program so as to assure compliance with the requirements of this specification.

715.6 Shipment and Storage

 

715.6.1 During periods of shipment and storage, the fabric shall be protected from direct sunlight, ultra-violet rays, temperatures greater than 60⁰C, mud, dust, and debris. To the extent possible, the fabric shall be maintained wrapped in a heavy-duty protective covering. Each shipping document shall include a notation certifying that the geotextile is in accordance with the manufacturer’s certificate and guarantee previously filed with the purchaser.

715.6.2 Product Marking

Label the fabric and its container with the manufacturer’s name fabric type or trade name, lot number and quantity.

715.7 Installation

715.7.1 Separation Geotextile

The geotextile shall be unrolled as smoothly as possible on the prepared subgrade in the direction of construction traffic. Adjacent geotextile rolls shall be overlapped in the direction of subbase placement using the guidelines in Table 3. Sewing is recommended where subgrade soils have a CBR value less than 1. The geotextile maybe held in place prior to subbase placement by pins, staples, or piles of fill or rock. On curves, the geotextile maybe folded or cut to conform to the curve. The fold or overlap shall be in the direction of construction and held in place as prescribed above.

715.7.2 Drainage Geotextile

In trenches, after placing the backfill material, the geotextile shall be folded over the top of the filter material to produce a minimum overlap of 300 mm for trenches greater than 300 mm wide. In trenches less than 300 mm in width, the overlap shall be equal to the width of the trench. The geotextile shall then be covered with the subsequent course. Successive sheets of geotextile shall be overlapped a minimum of 300 mm in the direction of flow.

715.7.3 Erosion Control Geotextile

The geotextile shall be placed and anchored on a smooth graded surface approved by the Engineer. The geotextile shall be placed in such a manner that placement of the overlying materials will not excessively stretch or tear the fabric. Anchoring of the terminal ends of the geotextile shall be accomplished through the use of key trenches or aprons at the crest and toe of slope. In certain applications to expedite construction, 450 mm long anchoring pins placed on 60 to 180 cm centers depending on the slope of the covered area have been used successfully.

 

715.7.4 Paving Fabric

The fabric shall be placed into the asphalt sealant with minimum wrinkling prior to the time the asphalt has cooled and lost tackiness. As directed by the Engineer, wrinklers or folds in excess of 25 mm shall be slit and laid flat. Brooming and/or pneumatic rolling will be required to maximize fabric contact with the pavement surface. Overlap of fabric joints shall be sufficient to ensure full closure of the joint, but should not exceed 150 mm. Transverse joints shall be lapped in the direction of paving to prevent edge pickup by the paver. A second application of asphalt sealant to fabric overlaps will be required if in the judgment of the Engineer additional asphalt sealant is needed to ensure proper bonding of the double fabric layer.

715.7.5 Geotextile Silt Fence

Fence construction shall be adequate to handle stress from sediment loading. Geotextile at the bottom of the fence shall be buried a minimum of 150 mm in a trench so that no flow can pass under the barrier. The trench shall be backfilled and the soil compacted over the geotextile. Fence height shall be as specified by the Engineer but in no case shall exceed 900 mm above ground surface. The geotextile shall be spliced together only at a support post with a minimum 150 mm overlap.

715.7.6 Hydraulic Filter

The geotextile shall be laid lengthwise down slopes and appropriately anchored along the top edge. Installation horizontally along slopes will not be accepted. Overlaps shall be sufficient to prevent parting of laps during the initial construction or fill stage. On soft soil subgrades the overlap shall not be less than 400 mm. Alternatively the geotextile shall be sawn using a double-stitch portable sewing machine and appropriate thread.

715.8 Method of Measurement

715.8.1           The geotextile shall be measured by the number of square meters from the pavement lines shown on the plans, or from the pavement lines established in writing by the Engineer.

715.8.2           Temporary silt fence will be measured in linear meter.

715.8.3           Removed sediment will be measured by the cubic meter.

715.8.4           Excavation, backfill, bedding, and cover material are separate pay items.

  

Table 2 Construction Survivability Levels

Site Soil CBR Installation	<1		1-2		>2
Equipment Ground Contract Pressure (KPa)	>345	<345	>345	<345	>345	>345
Cover Thickness (mm) (Compacted) 1022,3 152 305 457	NR NR NR H	NR NR H M	H H M M	H M M M	M M M M	M M M M
H = High M = Medium NR = Not Recommended

¹              Maximum aggregate size not to exceed one-half the compacted cover thickness

²           For low volume unpaved road (ADT<200 vehicles)

³           The 102 mm minimum cover is limited to existing road bases intended for use in new construction

Table 3 Recommended Overlaps

Soil Strength (CBR)	Unsewn Overlap (mm)	Overlap (mm)
Less than 1 1-2 2-3 3 and above	- 965 762 610	229 203 76 -

 715.9 Basis of Payment

            The quantities determined as provided above shall be paid for at the contract price per unit of measurement, respectively, for each pay item listed below.

            Payment shall be made under:

Pay Item	Pay Unit
Separation Geotextile Drainage Geotextile Paving Fabric Hydraulic Filter Slit Fence Remaining Sediment	Square Meter Square Meter Square Meter Square Meter Linear Meter Cubic Meter

Table 1 – Physical Requirement^1,.1A

APPLICATION
Property	Unit	Test Method	Subsurface Drainage2		Sediment Control		Erosion Control2		Hydraulic Filter		Paving2,11	Separation
			Class A3	Class B4	Wire Fence Supported	Self- Supported	Class A9	Class B10	Unpro-tected	Pro-tected		High Surviva-bility Level	Medium Surviva-bility Level
Grab Tensile Length	N	ASTM D 4632 ASTM D 1682	800	355	4002	4002	890	400	- 785	- 353	355	1200/800	800/510
Elongation	Percent	ASTM D 4632 ASTM D 1682	-	-	-	50% Max. @ 200 N	15	15	- -	- -	50% @ Break	<50% >50 percent12	<50% >50 percent12
Seam Strength5	N	ASTM D 4632	710	310	-	-	800	355	-	-	-	1067/710	710/465
Puncture Strength	N	ASTM D 4833 ASTM D 751-79	355	110	-	-	355	175	353	108	- -	445/335	310/175
Burst Strength	KPa	ASTM D 3786 ASTM D 751-79	2000	900	-	-	2220	965	2000	900	- -	-	-
Trapezoid Tear	N	ASTM D 4533 ASTM D 1117	220	110	-	-	220	130	216	108	- -	445/335	310/175
Permeability6 (K)	cm/sec	ASTM D 4491	K Fabric >  K Soil	K Fabric >  K Soil	-	-	K Fabric >  K Soil	K Fabric >  K Soil	-	-	-	K Fabric >  K Soil	K Fabric >  K Soil
Apparent Opening Size (AOS)	(US Std.)	ASTM D 4751	Notes 7 & 7A	Notes 7 & 7A	0.848 Max	0.848 Max	Notes 7 & 7A	Notes 7 & 7A	-	-	-	Notes 7 & 7A	Notes 7 & 7A
Permitivity	Sec.-1	ASTM D 4491	-	-	.012,8	.012,8	-	-	-	-	-	-	-
Ultraviolet Degradation	(Percent Retained Strength	ASTM D 4355	70 @150h	70 @150h	70 @150H	70 @150H	70 @150h	70 @150h	-	-	-	70 @150h	70 @150H
Asphalt Retention	L/m2	Appendix XI	-	-	-	-	-	-	-	-	0.9	-	-
Melting Point	oC	ASTM D 276	-	-	-	-	-	-	-	-	150	-	-

 Legend:

¹           Acceptance of geotextile material is to be used on ASTM D 4759, Standard Practice for determining the Specific Conformance Geotextiles

^1A         Contracting Agency may require a letter from the supplier certifying that its geotextile meets specification requirements.

²           Minimum- Use value in weaker principal direction. All numerical values represent minimum average roll value (i.e. test results from any sampled roll in a lot shall meet or exceed the minimum values in the table.) Stated values are for non-critical non-severe conditions. Lot sampled according to ASTM D 4354.

³           Class A Drainage applications for fabrics are where installation stresses are more severe than Class B applications, i.e. very coarse, sharp, angular aggregate is used, heavy degree of compaction (greater than 95 percent AASHTO T 99) is specified, or depth of trench is greater than 3 meters.

⁴           Class B Drainage applications are those where fabric is used with smooth graded surfaces having no sharp angular projections, no sharp angular aggregate is used, compaction requirements are light (less than 95 percent AASHTO T 99) and trenches are less than 3 meters in depth.

⁵           Values apply to both field and manufactured seams. See Table 3 for Recommended overlaps.

⁶           A nominal coefficient of permeability maybe determined by multiplying permitivity value by nominal thickness. The K value of the fabric should be greater than the K value of the soil.

⁷           Soil with 50 percent or less particles by mass passing 0.075 mm (No. 200) sieve, AOS less than 0.6 mm (greater than 0.600 mm (No. 30) sieve.

^7A         Soil with more than 50 percent by mass passing 0.075 mm (No. 200) sieve. AOS less than 0.297 mm (greater than 0.300 mm (No. 50) sieve.

⁸           Permitivity & Apparent Opening Size (AOS) do not relate directly to filtration performance of silt fence fabrics. Value presented reflect minimum criteria of products currently used. Performance tests such as VTM-51 (from Virginia Highway Research Council) may be used to evaluate silt fence performance if deemed necessary by the Engineer.

⁹           Class A Erosion Control applications are those where fabrics are used under conditions where installation stresses are more severe than Class B, i.e. stone placement height should be less than 0.9 m and stone mass should not exceed 113.5 kg.

¹⁰            Class B Erosion Control applications are those where fabric is used in structure or under conditions where the fabric is protected by a sand cushion or by “zero drop height" placement of stone.

¹¹         This specification is applicable to fabric membranes used for full coverage of the payment, or as strips over transverse and longitudinal pavement joints. It is not intended to describe membrane systems specifically designed for pavement joints and localized (spot) repairs.

¹²         Values of geotextile elongation do not imply the allowable consolidation properties of the sub grade soil - they must be determined by a separate investigation, but are intended to show that for fabrics with percent elongation less than 50 percent, a higher strength is required.