352 ALASKA 2020 SECTION 630 GEOTEXTILE FOR EMBAN KMENT AND ROADWAY SEPAR ATION, STABILIZATIO N AND REINFORCEMENT
630-1.01 DES CRIPTION. Prepare ground surface, and furnish and place geotextil es for
separation, stabilizat ion, and/or reinforcement as shown on the Plans.
630-2.01 MATERIALS. Use materials that conform to the following:
Geotextiles and Sewn Seam Strength Subs ection 729-2.01 Sewing Thread. Use high strength polypropylene, or polyester. Do not use nylon thread. Use thread of contrasting color to that of the geotextile itself.
630-3.01 Constructi On Requirements.
1.Surface Preparation. Prepare ground surface by removing stumps, brush, boulders, and sharp objects. Fill holes and ruts over 3 inches deep, with material shown on the Plans or as approved by the Engineer.
2.Geotextile Place ment. Unroll geotextile directly onto the prepared surface. Stre tch geotextile to remove any creases, folds or wrinkles. Do not drag the geotextile through mud or over sharp objects that could damage the geotextile. Do not expo se geotextiles to sunlight for longer than 14 days after removal of pr otective cover ing. Do not allow geotextiles to get wet prior to installation.
a.Separation and Stabilization. Lay geotextile for emba nkment sep aration and stabilization parallel to road way c enterline. O n hor izontal curves, place in segm ent lengths not exceedi ng those listed in Table 630-1, with butt en ds cut to match an d sewn or overlapped. On t angent s, stra ighten the geotextile an d sew or ov erlap butt end s. Shingle overlaps in the same direction as fill placement. Prevent overlapped edges from lifting during construction.
b.Reinforcement . Lay the machine direction of the geotextile for emba nkment reinforcement perpen dicular to the roadway cent erline or as shown on the Plans. J oin segments by sew ing or an app roved bondi ng or at tachment process. Shingle overlaps in the same direction as fill placement i f seams are not sewn. Prevent overlapped edges from lifting during construction. TABLE 630-1 GEOTEXTILE PLACEM ENT ON CURVES
3.Joining. Join adjacent geotextiles for separation or stabilization by overlapping or sewing. Join adjacent geotextiles for reinforcement by sewing or as shown on the Plans.
a.Sew seam s with a Butterfly or J-Seam using a double- thread chain stitch (lock stitch). Bring adjacent sections of geotextile together and fold so that the stitching penetrates Degree of Curve Maxi mum Segment Le ngth (ft.) 1 125 2 90 3 75 4 65 5 55 6 50 353 ALASKA 2020 four layers of geotextile for the full seam length. Make the stitch ing line 1-1/4 inches (±1/4 inch) from the folded edge of the seam and at least 1/2 inch from the free edge of the geotextile. Sew seams so that they face upward and can be easily inspected by the Engineer. Illustrati ons showing correct stitch formation and s eam configurations are provide d in Figure 1-2 (page 1- 28) of the FHWA publ ication, Geosynthetic Design & Construction Guidel ines, FHWA -NHI-07-092, August 2008 .
b.Overla p geotextile sectio ns by a minimum of 3 feet at all longitudinal and transverse joints. Place the beginning of each new roll beneath the end of the previous roll to prevent the advancing fill from lifting the geotextile. Shi ngle in the direction of construction.
4.Material Placing and Spreading. During placing and sprea ding of material, maintain a minimum depth of 12 inches of cover material; or a minimum depth equal to the separation distance between multiple layers of geotext ile as shown on the Plans when this separation distance is less than 12 inches; at all times between the geotextile and the wheels or tracks of the con struction equip ment. Limit the size and weight of construction equipment to reduce rutting in the initia l lift above the geotextile to not greater than 3 inches deep to prevent overstressing the geotextile. Spre ad the material in the direction of the upper overlapped geotextile. Maintai n proper overlap and geotextile conti nuity. If sewn or bonded seams are used, place the cover material and spread in only one directi on for the entire length of the geotextile. On weak subgrades limit height of dumped cover material to prevent localized subgrade and/or geotextile failure. Do not drop stones or frozen material larger than 1 foot in diameter directly onto the geotextile from a height of more than 1 foot. Com pact using a smooth drum roller. Do not allow construction equip ment to make sudden stops, star ts, or tur ns on t he cover material. Do not allow turning of v ehicles on the initial lift of cover material above the geotextile. Fill any ruts over 3 inches deep occurring during construction with material shown on the Plans; do not grade adjacent material into rut; and compact to the specified density.
5.Geotextile Repair. Repair and replace damaged geotextile (torn, punctured, or disturbed at the overlaps or sewn joints). For damage evidenced by visible geotextile damage, subgrade pumping, intrusion, or embankment distortion, remove the backfill around and under the damaged or displaced area, and repair with material matching the damaged material. Make patches overlap or sew patches to the existing geotextile..
a.Separation and Stabilization. Overlay torn area with geotextile with a minimum 3 foot overlap arou nd the ed ges of the torn or damaged ar ea or sew and bond according to Subsection 630- 3.01.3.a. Ensure the patch remai ns in pla ce when cover material is placed over the affected area.
b.Reinforcement . Sew according to Subs ection 630-3.01.3.a unless joining by overlap is shown on the Plans. E nsure the patch remai ns in place when cover material is placed over the affected area.
630-4.01 METHOD OF M EASUREMENT. By multiplying plan neat line width by the measured
length in final position parallel to installation centerline along the ground surface. No allowance will be made for over lap, whether at joint s or pat ches.
630-5.01 BASIS OF PA YMENT. Payment will be made at the contract unit price per square yard.
Material used to fill ruts and holes will be paid for under separate materials pay items. 354 ALASKA 2020 Payment will be made under: PAY ITEM Item Number Item Description Unit 630.0001. ____ Geotextile, Separation, Class 3 SY 630.0002. ____ Geotextile, Stabilization, Class 1 SY 630.0003.____ Geotextile, Reinforcement - Type ____ SY 355 ALASKA 2020 SECTION 631 GEOTEXTILE FOR SUBSU RFACE DRAINAGE AND E ROSION CONTROL
631-1.01 DESCRIPTION . Prep are ground surfac e, and furnish and place geotextiles for
subsurface drai nage and erosion control, as sho wn on the Plans.
631-2.01 MATERIALS. Use materials that conform to the following for the class specified in the
bid sche dule: Geotextiles and Sewn Seam Strength Subs ection 729-2.01 Sewing Thread. Use high strength polypropylene, or polyester. Do not use nylon thread. Use thread of contrasting color to that of the geotextile itself.
631-3.01 Constructi On Requirements.
1.Surface Pr eparati on. Prepare ground s urface by removi ng stu mps, brush, boulders, and sharp objects. Fill holes and ruts over 3 inches deep, with material shown on the Plans or as approved by the Engineer. Construct smooth and stable trench walls.
2.Geotextile Place ment. Unroll geotextile directly onto the prepared surface. Stretch geotextile to remove any creases, folds or wrinkles. Place geotextile in a manner which will ensure intimate contact between the trench wall and the geotextile (i.e., no voids, folds, or wrinkles). The geotextile may be held in place with securing pins at 3- foot spacing along all edges (but not closer than 2 inches from the edge) to prevent movement during construction. Do not expo se geotextiles to sunlight for longer than 14 days after removal of protective cover ing. Do not allow geotextile rolls to get wet prior to installation.
a.Subs urface Drai nage. In trenche s, after placing the geotextile and material shown on the Plans , fold the geotextile over the top of the material shown on the Plans to produce a minimum overlap of 12 inches, for trenche s great er than 12 inches wide. In trenches less than 12 inches wide, make the overl ap equal to the width of the trench. Then cover the ge otextile with the s ubsequ ent cou rse of material.
b.Erosion Control. Place and anchor geotextile on the approved surface so it will not be torn or excessively stretc hed by placem ent of the overlying mater ials. Secure the geotextile to the s lope but secure it loosely enough so that the geotextile will not tear when riprap or other cover material is placed on the geotextile. The geotextile shall not be keyed at the top of the slope until the riprap or other cover material is in place at the top of the slope. Anch or the terminal end s of the geotextile using key trenches or aprons with a minimum of 24 inches depth into the soil substrate at the crest and toe of slope, or as shown on the Plans. Place geotextile with the machine direction parall el to the direction of water flow (normally parallel to the slope for erosion control runoff and wave action, and parallel to the stream or channel).
3.Joining. Join geotextile by sewing or overla pping.
a.Sew seam s with a Butterfly or J-Seam using a double thread chain stitch (lock stitch). Bring adjacent sections of geotextile togeth er and fold so that the stitching penetrates four layers of geotextile for the full seam length. Make the stitching line 1-1/4 inches (±1/ 4 inc h) from the folded edge of the seam and at least 1/2 inch from the free edge of the geotextile. Sew seams so that they can be easily inspected by the Engineer or representative. Illustrati ons showing correct stitch formation and seam configurations are provid ed in Figure 1-2 (page 1- 28) of the FHWA publ ication, Geosynthetic Design & Co nstruction Guidel ines, FHWA -NHI-07-092, August 2008.
Source: Alaska Standard Specifications for Highway Construction, 2020 Edition. Pages 380–382 of 584.