609.01 Description.
Required Overlaps Soil Strength (CBR) Unsewn Overlap (inches {mm}) Sewn Overlap (inches {mm}) < 1 - - 9 {225} 1 - 2 38 {950} 8 {200} 2 - 3 30 {750} 3 {75} > 3 24 {600} - - Unless shown otherwise on the plans, the required overlap shall be as shown for a CBR value of 1 - 2. The geotextile may be held in place prior to subbase placement by pins, staples, or piles of fill or rock. Geotextiles may be folded or cut to conform to any curvature of the area. A fold or overlap shall be in the direction of construction and held in place a s prescribed above.
608.05 Seams.
Both factory and field sewn or sealed seams shall conform to the strength requirements of Table 1 as outlined in AASHTO M 288 for Separation Applications. All seams shall be subject to the approval of the Engineer.
608.06 Subbase Placement.
The subbase shall be placed by end dumping onto the geotextile from the edge of the geotextile, or over previously placed subbase aggregate. On subgrades having a CBR of 1, the subbase aggregate shall be spread simultaneously with dumping to minimize the potential of a localized subgrade failure. Direct traffic on the geotextile, along with any sudden stops, starts, or turns on the subbase material by construction equipment, shall be avoided where possible. Using whatever means, the subbase material shall be spread from the back dumped pile. Except in the case of low volume roads (ADT < 200), a minimum thickness of 6 inches {150 mm} shall be maintained. In the case of low volume roads, this thickness shall be 4 inches {100 mm}. A smooth drum roller shall be used to achieve the specified density. Any ruts occurring during construction shall be filled with additional subbase material and compacted to the specified density. The use of vibratory compaction will not be allowed a s it may cause damage to the geotextile.
608.07 Damage Repair.
Damaged geotextiles, as identified by the Engineer, shall be repaired immediately. The damaged area, plus an additional 3 feet {1 m} around the area, shall be cleared of all fill material. This area shall be covered with a geotextile patch extending 3 feet {1 m} beyond the perimeter of the damage. The removed subbase material shall be replaced and compacted to the specified density.
608.08 Method of Measurement.
The geotextile will be measured by the square yard {square meter} from the payment lines shown on the plans, or from the payment lines established in writing by the Engineer. This excludes seam overlaps. Excavation, backfill, bedding, and cover material are separate pay items.
608.09 Basi s of Payment.
a.General . The accepted quantities of geotextiles will be paid for at the contract unit price per square yard {square meter} in place.
b.Payment will be made under Item No .: 608-A Separation Geotextile - per square yard {square meter} AGGREGATE SLOPE PROTECTION
609.01 Description.
This Section shall cover the work of furnishing and constructing a slope protection layer of graded aggregat e on slopes as shown on the plans or directed in accordance with these Specifications. This
609.02 Materials.
Section shall also cover the work, if shown on the plans, of furnishing and installing a geotextile filter blanket on slopes which are to receive the aforementioned aggregate protection layer.
609.02 Materials.
Materials furnished for use shall conform to the appropriate requirements of Division 800, Materials, and the following:
a.Geotextile Filter .
1.General . The geotextile shall meet the requirements of AASHTO M 288 for Permanent Erosion Control Geotextile, Class 2, and Section 810 of these specifications. In addition, the fabric shall have a minimum coefficient of friction of the wet fabric on wet aggregate of 0.4 as determined by the Department's Central Lab. The geotextile shall be selected from List II -3, of the Department's manual titled "Materials, Sources, and Devices With Special Acceptance Requirements". Information concerning this list is given in Subarticle 106.01(f) and ALDOT -355.
2.Securing Pins . Securing pins for anchoring the filter shall be 3/16 of an inch {5 mm} steel bars, pointed at one end and fabricated with a head to retain a steel washer having an outside diameter of not less than 1.5 inches {38 mm}. The length of the pin shall not be less than 18 inches {450 mm}.
b.Aggregate . The aggregate shall be crushed stone meeting the requirements given in Section 801. The aggregate gradation shall be: AGGREGATE GRADATION FOR AGGREGATE SLOPE PROTECTION Percent Passing by Weight {Mass} Sieve Size Minimum Maximum 7" {175 mm} 100 - 6" {150 mm} 90 100 4" {100 mm} 20 55 3" {75 mm} 0 15 2" {50 mm} 0 5
609.03 Construction Requirements.
a.Preparation of Surface . The slope to be treated shall be prepared by removing vegetation, topsoil, and dressing the slope to reasonable line and grade. The surface shall then be compacted, if necessary, by the use of mechanical tampers to the satisfaction of the Engineer before placement of the geotextile filter and aggregate blanket. The dress ing and preparation of the slope shall be considered incidental to the placement of the Aggregate Protection Blanket and no direct payment for such will be made. Where grading has been completed under another contract and regrading is necessary to obtain the desired uniform slope, such regrading shall be considered incidental to the placement of the aggregate protection blanket and no direct payment for such will be made.
b.Placement of Geotextile Filter . The geotextile filter, if required, shall be placed in the manner and at the locations shown on the plans or as directed by the Engineer. Exposure of the geotextile to the elements between lay down and cover shall be a maximum of 14 days to minimize damage potential. At the time of installation, filter shall be rejected if it has defects, rips, holes, flaws, deterioration, or damage incurred during manufacture, transportation, or storage. The filter shall be placed with the long dimension horizontal with the natural ground line, unless otherwise directed by the Engineer, and shall be laid smooth and free of tension, stress, folds, wrinkles or creases. The strips shall be placed to provide a minimum width of 3 feet {1 m} of overlap for each joint. Overlap joints and seams shall be measured as a single layer of cloth. Securing pins with washers shall be inserted through both strips of overlapped cloth at not greater than the following intervals along a line through the midpoint of the overlap. Pin Spacing Slope 2 feet {0.6 m} Steeper than 1:3 3 feet {1.0 m} 1:3 to 1:4 5 feet {1.6 m} Flatter than 1:4 The filter shall be turned down and buried approximately 12 inches {300 mm} at all exterior limits.
610.02 Materials.
Additional pins, regardless of location, shall be installed as necessary to prevent any slippage of the geo textile filter. Each securing pin shall be pushed through the filter until the washer bears against the filter and secures it firmly to the foundation. The filter shall be protected at all times during construction from contamination by surface runoff and any filter so contaminated shall be removed and replaced with uncontaminated filter. Any damage to the filter during its installation or during placement of riprap shall be replaced by the Contractor. The work shall be scheduled so that 30 days does not ex pire between placement of the filter and the covering of the filter with the graded aggregate. Aggregate shall not be dropped on the filter from a height greater than 1 foot {300 mm}. Greater drop heights will be permitted if the Contractor provides a cush ioning layer of sand on top of the filter before dumping of stone. The combination of drop height for stone and sand cushion layer thickness to be approved shall be demonstrated to not puncture or damage the filter. No measurement or separate payment shall be made for a sand cushion layer placed for the purpose of allowing an increased drop height of stones. Any damage to the geotextile filter during placement of aggregate shall be corrected prior to proceeding with the work.
c.Placement of Aggregate . The method of placement of the aggregate shall be at the option of the Contractor provided it produces uniform coverage and depth without damaging the geotextile filter, if present. Any damage to the filter shall be cause for ordering the aggregate cleaned from the damaged area and the repair of the filter by an additional layer of filter covering the damaged area overlapping at least 3 feet {1 m} onto undamaged filter and securing the patch with adequate securing pins. If uniformity of coverage is not obtaine d by the method of placement, such shall be corrected in a manner satisfactory to the Engineer. No compaction of the aggregate blanket is required.
609.04 Method of Measurement.
Accepted aggregate slope protection and geotextile filter for aggregate slope protection, if applicable, will each be measured in square yards {square meters}, complete in place, computed from actual measurements taken along the top surface of the treated area to the nearest 0.1 square yard {0.1 m²}.
609.05 Basis of Payment.
a.Unit Price Coverage . The accepted Aggregate Slope Protection and geotextile filter for aggregate slope protection, measured as noted above, will each be paid for at the contract unit price bid per square yard {square meter}. Said unit price bi d shall be full compensation for the item complete in place and includes the furnishing of all materials, the preparation of the slope (excavation, backfill, compacting slope, disposal of surplus material), placement of materials and for all equipment, too ls, labor, and incidentals necessary to complete the work.
b.Payment will be made under Item No .: 609-A Aggregate Slope Protection - per square yard {square meter} 609-B Geotextile Filter for Aggregate Slope Protection - per square yard {square meter} SECTION 610 RIPRAP
610.01 Description.
This Section shall cover the work of furnishing and constructing the several classes or types of r iprap, each of which shall consist of a protective course of stone or other approved materials on embankment slopes, in channels and ditches, wave protection for causeways and shoreline roadway embankments, bridge piers and abutments, or other work as shown on the plans or directed, with or without a geotextile filter, all in accordance with these specifications and in conformity with the lines, and grades note d in the plan details.
610.02 Materials.
If a geotextile filter is required, it shall meet the requirements of AASHTO M 288 for Permanent Erosion Control Geotextile, Class 1, and Section 810 of these specifications. All other materials shall
Source: Alabama Standard Specifications for Highway Construction, 2022 Edition. Pages 486–487 of 934.