360 ALASKA 2020 SECTION 634 GEO GRID FOR EMBANKMENT A ND ROADWAY STABILIZATION AND RE INFORCEM ENT
634-1.01 DESCRIPTION . Furnish and install ge ogrid material as show n on the Pla ns.
634-2.01 MATERIALS. Use materials that conform to the following:
Geog rid Subs ection 729-2.04
634-3.01 C Onstructio N Requirements.
1.Surface Preparation.
a.Soft Ground (C BR ≤3). Prep are surf ace by removal of 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.
b.Firm Ground (C BR >3). Compa ct and finish s ubgrade or subb ase pri or to placement of the geog rid.
2.Geogrid Placement. Unroll geo grid di rectly onto t he prep ared ground surface in the direction of advancing construction, parallel to the centerline of the roadway or according to the Plans. Do not drag the geogrid across the subgrade. Install the geogrid in the longest continuous practical length, free from folds, creases or wrinkles. Hold the geogrid in place with pins, staples, sandbags or piles of granular material. Do not expose geogrids to sunlight for longer than 14 days after removal of protective covering.
a.Soft Groun d (CBR ≤3). Overlap geogrid panels a minimum of 24 inches at all joints with the upper geogrid in the dir ection that fill will be placed. Tie panel s togethe r securely with cable ti es or ho g rin gs at 20 foot intervals, or according to the manufacturer's recommendations.
b.Firm Ground (CBR >3). Overl ap geogrid pan els a minimum of 12 inches at all joints in the direction that fill will be pl aced. Tie panels toget her securely with cable t ies or hog rings at 20 foot intervals and hand- tension geogr id and stake to the groun d at the edge s, overlap s, and in the center of each roll, at 30 foot interval s or as shown on the Plans . Place the beginning of each new roll beneath the end of the previous roll to prevent the advancing fill from lifting the geogrid. Stagger end overlaps at least 10 feet from other end overlaps in adjacent rolls.
3.Placement of Cover Material. Do not operate equi pment directly on the unprotect ed geogrid. Spre ad fill material in the dir ection of the fabric overlap. Com pact using a smooth drum roll er. Do not allow construction eq uipment to make sud den stops, star ts, or tur ns on the cov er material.
a.Very Soft Ground (CBR < 1). End-dump material onto previously placed material and spread over the geogrid with a low gr ound pressure do zer to the dept h permitted. Maintain a minimum depth of 12 inches of cover material at all times between the geogrid and the wheels or tracks of the construction equipment unless otherwise shown on the Plans. Do not dump material directly onto the geogrid. To prevent a mud wave, end-dump fill along the edges of the geogrid to form toe berms or access roads that extend one to two panel widths ahead of the remainder of the embankment fill placement. After constructing the two berms, spread fill in the area between the toe berms by placing material parallel to the alignment and symmetrical from the toe berms inward toward the center to maintain a U -shaped leading edge (i.e., concave outward) to conta in the mud wave. Limit height of dumped piles above the geogrid to avoid local bearing failure. Traffic on the first lift should be parallel to the embankment alignment. Do not allow 361 ALASKA 2020 construction equipment to turn on the first lift. Compact first lift by tracking in place with dozers or end- loaders. Compact with specified compaction equipment once embankment is at least 2 feet above the geogrid.
b.Soft Ground (1 ≤ CBR ≤ 3). End-dump material onto previously placed material and spread over the geogrid with a low gr ound pressure do zer to the dep th permitted. Maintain a minimum depth of 6 inches of cover material at all times between the geogrid and the wheels or tracks of the construction equipment unless otherwise shown on the Plans. Place the end- dumped material along the roadway centerline and spread it outward to the roadway edges to prevent the development of wrinkles or movement of the geogrid during construction. Fill in any ruts that form during construction with material shown on the Plans. Do no t cut down the fill adjacent to the ruts.
c.Firm Ground (CBR > 3). Maintain a minimum depth of 6 inches of cover material at all times between the geogrid and the wheel s or tracks of the con struction equipm ent.
4.Geogrid Repair. Should the geogrid be torn, punctured, or the overlaps disturbed – as evidenced by visible geogrid damage – remove the backfill around the damaged area and repair or replace the damaged area at no additional expense to the State. Make repairs to the damaged area with a patch of the sam e type of geogrid originally placed. Overlay torn area with geogrid with a minimum 3 foot overlap around the edges of the torn area and secure as recommended by the geogrid manufacturer.
634-4.01 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 overlap, whet her at joi nts or patche s.
634-5.01 BASIS OF PA YMENT. Payment will be made at the contr act unit price p er square yard.
Material used to fill ruts and hol es will be paid for at the unit pr ice for the type of material u sed. Payment will be made under: PAY ITEM Item Number Item Description Unit 634.0001.____ Geogrid, Stabilization, Class ___ SY 634.0002.____ Geogrid, Reinforcement, Class ___ SY 362 ALASKA 2020 SECTION 635 INSULATION BOARD
635-1.01 DESCRIPTION. Furnish and install polystyrene insulation board where shown on the
Plans.
635-2.01 MATERIALS. Use materials that conform to the following:
1.Insulation Board. AASHTO M 2 30, Type VI, except that extrusion is not required, and the maximum water absorption is 0.3 percent by volume, as determined by ASTM C272. Insulation board must meet or exceed the minimum thickness called out in the plans, and have a 20- year warranted ther mal resistance (R -Value) @ 75°F of 4.5 per inch of thickness as determined by ASTM C177 or ASTM C518. The required thickness is shown on the Plans and is actual thickness, not nominal thickness.
2.Sand Blanket . Subsection 703- 2.12, except meet the followi ng gradation as tested by ATM 304. TABLE 635 -1 SAND BLANKET MATERIA L GRADATION
635-3.01 CONSTRUCTIO N REQUIREMENTS. Prior to placing the insulation board, blade,
shape, and compact the area per Section 203. Place a sand blanket leveling course at least four inches thick. Finish the leveling course surface so it does not vary more than 0.10 foot when tested using a ten foot straightedge. Set each board accurately to the line and grade established and anchor firmly in place by driving a minimum of 2 wood dowels per panel. Place insulation to the required thickness, using a minimum of two layers. Stagger all joints between layers. Cover the insulation board with twelve inches of sand blanket material prior to placing subsequent lifts. Use approved spreading and compacting equipment.
635-4.01 METHOD OF M EASUREMENT . See Section 109.
Sand blanket material will be paid for under 203.0006._____ Borrow.
635-5.01 BASIS OF PA YMENT . Payment will b e made under:
PAY ITEM Item Number Item Description Unit 635.0001.____ Insulation Board MBM 635.0002.____ Insulation Board SF SIEVE PERCENT PASSING BY WEIGHT 2 in. 100 No. 4 15-65 No. 200 0-6
Source: Alaska Standard Specifications for Highway Construction, 2020 Edition. Pages 388–389 of 584.