Concrete Revetment Mats Art. 285.02 The Contractor may assemble, partially fill, and tie together mattress units on the subgrade, provided they can be placed on the slope without abrading the zinc or vinyl coating on the wire mattress or permanently distorting the shape of the mattress in transporting and installing the units on the slope. All prefabrication procedures shall be subject to the approval of the Engineer. The Contractor shall maintain the gabions or slope mattress until final acceptance and any material displaced by any cause shall be replaced.
284.06 Disposal of Surplus Material. Surplus or waste material resulting
from the gabion or slope mattress operations shall be disposed of according to
Article 202 — 03.
284.07 Method of Measurement. Gabions will be measured for payment in
place and the volume computed to the nearest cubic yard (cubic meter), based on the actual lengths, widths, and depths. Slope mattress will be measured for payment in place and the area computed in square yards (square meters) based on the actual lengths and widths over which placement is made. Filter fabric will be measured for payment according to Article 282.08.
284.08 Basis of Payment. This work will be paid for at the contract unit price
per cubic yard (cubic meter) for GABIONS or at the contract unit price per square yard (square meter) for SLOPE MATTRESS, of the thickness specified. Filter Fabric will be paid for according to Article 282.09. SECTION 285. CONCRETE REVETMENT MATS
285.01 Description. This work shall consist of constructing fabric formed
concrete revetment mat; or furnishing and placing precast block revetment mat, and articulated block revetment mat.
285.02 Materials. Materials shall be according to the following.
a.Fabric Formed Concrete Revetment Mat. Item Article/Section
1.Grout .......................................................................................... 1024.01
2.Fabric Formed Concrete Revetment Mats .................................. 1080.04
b.Precast and Articulated Block Revetment Mats. Item Article/Section
1.Precast Concrete Block (Note 1) ...................................................... 1042
2.Cable, Anchors and Fittings (Note 2)
3.Portland Cement Concrete (Note 3) ................................................. 1020 Note 1. The block size, block weight (mass), block configuration (interlocking or non-interlocking), and mat configuration (open-cell or closed-cell) shall be as specified on the plans. Art. 285.03 Concrete Revetment Mats Note 2. Cable, anchors, and fittings, such as sleeves, clamps, and stops, shall be according to the manufacturer’s specifications and shall be corrosion resistant. Note 3. Class SI concrete shall be used.
285.03 Equipment. Equipment shall be according to the following.
a.Fabric Formed Concrete Revetment Mat. Mixing and pumping equipment used in preparation and handling of the grout shall be approved by the Engineer. All oil or other rust inhibitors shall be removed from the mixing drums, stirring mechanisms, and other portions of the equipment in contact with the grout before the mixers are used. The pumping equipment shall have a variable flow rate to provide enough pressure for pumping without breaking the fabric.
b.Precast and Articulated Block Revetment Mats. Equipment used to lift and place the blocks/mats shall be approved by the Engineer. CONSTRUCTION REQUIREMENTS
285.04 General. The surface to be protected shall be graded as shown on
the plans and prepared such that it is stable in the absence of erosive forces. Any fill material required to restore the surface to its original condition shall be approved by the Engineer.
285.05 Fabric Formed Concrete Revetment Mat. The grout shall consist of
a mixture of portland cement, fine aggregate, and water so proportioned and mixed as to provide a pumpable slurry. Fly ash and concrete admixtures may be used at the option of the Contractor. The grout shall have an air content of not less than 6.0 percent nor more than 9.0 percent of the volume of the grout. The mix shall obtain a compressive strength of 2500 psi (17,000 kPa) at 28 days according to
Article 1020 — 09.
All materials shall be accurately measured by volume or weight (mass) as they are fed into the mixer. Time of mixing shall be not less than one minute. If agitated continuously, the grout may be held in the mixer or agitator for a period not exceeding two and one-half hours in temperatures below 70 °F (21 °C), and for a period not exceeding two hours at higher temperatures. If there is a lapse in a pumping operation, the grout shall be recirculated through the pump or through the mixer drum (or agitator) and pump. Prior to grout injection, the fabric shall be positioned at its design location. Each panel shall be a continuous or monolithic unit for its full width, including the trench portion. Each panel shall consist of two or more mill-widths of open selvage construction; the two upper layers shall be joined together by sewing, and the two bottom layers shall be sewn together at the edges. Where adjacent panels cannot be joined in this manner, they shall be lapped a minimum of 24 in. (600 mm). In no case will simple Concrete Revetment Mats Art. 285.07 butt-joints, either sewn or unsewn, be permitted. The ends and upper limits of the fabric shall be placed in a trench of suitable width as shown on the plans. Filling of the fabric shall begin at the lower elevations and proceed up the slope. The grout shall be injected between the layers of fabric through small cuts. The point of injection shall be a maximum of 30 ft (9 m) from the end of the panel. The grout shall be pumped without exerting excessive pressure on the fabric envelope. After grouting has been completed, the void between the trench wall and filled fabric shall be backfilled. Injection holes left in the fabric shall be closed by temporarily inserting a piece of burlap or similar material. The burlap shall be removed when the grout is no longer fluid and the surface is firm to hand pressure. Foot traffic on the filled revetment mats shall be kept to an absolute minimum for one hour after pumping.
285.06 Precast Block Revetment Mat. Filter fabric shall be installed
according to Section 282 prior to placement of the precast block revetment mat, or it may be secured to the bottom of the mat according to the manufacturer’s specifications and installed concurrently. The precast blocks may be placed individually or as pre-assembled mats. Normally, placement shall begin at the downstream end and proceed upstream. At side slopes, placement shall begin at the toe and proceed up. All edges of the precast block revetment mat shall be flush with the existing ground. Orientation of the blocks with respect to water flow shall be as specified by the manufacturer. After placement, the voids in and around the blocks shall be filled with soil meeting the approval of the Engineer.
285.07 Articulated Block Revetment Mat. Filter fabric shall be installed
according to Section 282 prior to placing the articulated block revetment mat, or it may be secured to the bottom of the mat according to the manufacturer’s specifications and installed concurrently. Normally, placement of the mats shall begin at the downstream end and proceed upstream. At side slopes, placement shall begin at the toe and proceed up. The upstream and outside edges of the mat shall be trenched at least one block deep and backfilled. The downstream edge shall be flush with the existing ground. As mats are placed, they shall be anchored at the frequency and depth shown on the plans. If required by the manufacturer, adjacent mats shall be clamped or crimped together as well. After placement of the mats, the voids in and around the blocks shall be filled with soil meeting the approval of the Engineer. Excessive openings between mats shall be filled, as directed by the Engineer, with concrete. Art. 285.08 Concrete Revetment Mats
285.08 Disposal of Surplus Material. Surplus or waste material shall be
disposed of according to Article 202.03. Excess excavated material shall not remain in the flood plain, nor shall it be placed within the banks of the waterway.
285.09 Method of Measurement. This work will be measured for payment in
place and the area computed in square yards (square meters). The area for measurement will include the upper, sloped surface of the mat. The portion of the mat in trenches will not be measured for payment. No allowance will be made for overlaps. Filter fabric will be measured for payment according to Article 282.08.
285.10 Basis of Payment. This work will be paid for at the contract unit price
per square yard (square meter) for FABRIC FORMED CONCRETE REVETMENT MAT, PRECAST BLOCK REVETMENT MAT, or ARTICULATED BLOCK REVETMENT MAT. Filter fabric will be paid for according to Article 282.09. Subgrade Preparation Art. 301.04
Division 300 — Subgrades, Subbases, and Base Courses
SUBGRADE SECTION 301. SUBGRADE PREPARATION
301.01 Description. This work shall consist of preparing the completed or
existing earthwork as an unimproved subgrade prior to constructing the pavement structure, shoulders, or appurtenances.
301.02 Equipment. Equipment shall be according to the following.
Item Article/Section
a.Steel Wheel Roller .............................................................................. 1101.01
b.Tamping Roller ................................................................................... 1101.01
c.Pneumatic-Tired Roller ....................................................................... 1101.01
d.Subgrade Planer ................................................................................. 1103.08
e.Subgrade Machine.............................................................................. 1103.09 CONSTRUCTION REQUIREMENTS
301.03 General. When the contract includes rough grading and surfacing, the
rough grading shall be completed as far in advance of the construction of the surfacing as feasible. When the rough grading has been included in a previous contract, all vegetation shall be removed prior to preparing the subgrade. The subgrade shall be prepared such that after compaction, it will be smooth and conform to the alignment, grades, and cross sections shown on the plans. Surplus excavated material resulting from grading and shaping the subgrade shall be disposed of according to Article 202.03. When additional material is required, it shall be obtained from within the right-of-way when possible and approved by the Engineer. Placement shall be according to Articles 205.04 and 205.05.
301.04 Subgrade Compaction and Stability. The subgrade shall be
compacted to not less than 95 percent of the standard laboratory dry density and shall have a minimum immediate bearing value (IBV) of 8.0. Densities will be determined according to Article 205.06. The IBV will be determined according to Illinois Test Procedure (ITP) 501 or 502. In cut sections, the Contractor shall take the following steps to obtain the required density and IBV values.
a.Step 1. Cut plan ditches, which drain the area, at least to grade. This shall be done at least two weeks prior to Step 2.
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Source: Illinois Standard Specifications for Road and Bridge Construction, 2022 Edition. Pages 156–160 of 1,217. View official source ↗