1、Section 22 SLOPE PROTECTION 22.1 GENERAL 22.1.1 Description This work shall consist of the construction of bank and slope protection courses in accordance with these Speci- fications and in reasonably close conformity with the lines, grades, and thicknesses shown on the plans or es- tablished by the
2、 Engineer. 22.1.2 Types Types of slope protection are designated as follows: (1) Riprap Hand-Placed Riprap-hand-placed stones on earth Machine-Placed Riprap-machine-placed stones on Wire-Enclosed Riprap (Gabions)-stones placed in Grouted Riprap-hand-placed riprap as described Sacked Concrete Riprap-
3、hand-placed sacked con- or gravel bedding. earth or gravel bedding. wire fabric enclosures. above with voids filled with sand-cement grout. crete. (2) Concrete Slope Paving Cast-in-Place Slope Paving-Portland cement con- crete, pneumatically applied mortar or, when per- mitted, fabric forms filled w
4、ith structural concrete grout. (3) Precast Concrete Slope Paving-Portland cement concrete slabs, blocks, or shapes precast prior to place- ment. 22.2 WORKING DRAWINGS Whenever specified or requested by the Engineer, the Contractor shall provide working drawings with design calculations and supportin
5、g data in sufficient detail to per- mit a structural review of the proposed design of a slope protection system. When concrete is involved, such data shall include the sequence and rate of placement. Suffi- cient copies shall be furnished to meet the needs of the En- gineer and other entities with r
6、eview authority. The work- ing drawings shall be submitted sufficiently in advance of proposed use to allow for their review, revision, if needed, and approval without delay to the work. The Contractor shall not start the construction of any slope protection system for which working drawings are req
7、uired until the drawings have been approved by the En- gineer. Such approval will not relieve the Contractor of re- sponsibility for results obtained by use of these drawings or any other responsibilities under the contract. 22.3 MATERIALS 22.3.1 Aggregate Aggregate for riprap shall conform to the r
8、equirements of Subsection 703.16 of the AASHTO Guide Spec$ca- tions for Highway Construction. Aggregate for underdrains and filter blankets shall conform to Sections 704 and 705, respectively, of the AASHTO Guide Specijications for Highway Construction. 22.3.2 Wire-Enclosed Riprap (Gabions) Gabions
9、shall be constructed of wire mesh. The wire mesh shall be made of galvanized steel wire having a min- imum size of 0.120-inch diameter (U.S. Wire Gage No. 11). The tensile strength of the wire shall be in the range of 60,000 to 85,000 psi, determined in accordance with ASTM A 392. The minimum zinc c
10、oating of the wire shall be 0.80 oz/sq ft of uncoated wire surface as determined in accordance with ASTM A 90. Selvedge, tie, and connection wire shall meet the same strength and coating requirements specified above for wire used in the wire mesh. 22.3.3 Filter Fabric Filter fabric shall meet the re
11、quirements of Subsection 705.03 of the AASHTO Guide Specijications for Highway Construction. 645 646 HIGHWAY BRIDGES 22.3.4 22.3.4 Grout Grout shall consist of one part Portland cement and three parts of sand, thoroughly mixed with water to pro- duce a workable mix. 22.3.5 Sacked Concrete Riprap Con
12、crete for sacked concrete riprap shall consist of a mixture of clean pitrun or washed sand and gravel, cement and water. The mixture shall contain not less than 376 pounds of Portland cement per cubic yard and sufficient water to obtain a slump of 3 to 5 inches. Sacks for sacked concrete riprap shal
13、l be made of 10-ounce burlap or other fabric having equal or greater strength. Sacks shall be approximately 19% inches by 36 inches measured inside the seams when the sack is laid flat, with an approximate capacity of 1.25 cubic feet. Sound, reclaimed sacks may be used. 22.3.6 Portland Cement Concre
14、te Portland cement concrete for cast-in-place slope paving shall conform to the provisions in Section 8, “Con- crete Structures,” for Class B or Class B (AE) concrete using the 1-inch maximum combined grading. Expansion joint filler shall conform to the provisions in Article 8.9.2.1. 22.3.7 Pneumati
15、cally Applied Mortar Materials for pneumatically applied mortar shall con- form to the requirements of Section 24, “Pneumatically Applied Mortar.” 22.3.8 Precast Portland Cement Concrete Blocks and Shapes Precast Portland cement concrete blocks and shapes shall meet the requirements of ASTM C 129, C
16、 139, or C 145, grade as specified. Materials for precast Portland ce- ment concrete slabs shall conform to the requirements in Article 8.13. “Precast Concrete Members.” 22.3.9 Reinforcing Steel Reinforcement shall conform to the provisions in Sec- tion 9, “Reinforcing Steel.” 22.3.10 Geocomposite D
17、rain Geocomposite drain shall consist of a manufactured core with one or both sides covered with a layer of filter fabric. The manufactured core shall be a preformed grid of embossed plastic, a mat of random shapes of plastic fibers, a drainage net consisting of a uniform pattern of poly- meric stra
18、nds forming two sets of continuous flow chan- nels, a system of plastic pillars and interconnections form- ing a semi-rigid mat, or other system approved by the Engineer, which will conduct the flow of water designated on the plans or in the special provisions. Filter fabric shall conform to the req
19、uirements of Arti- cle 22.3.3 and shall be integrally bonded to the core ma- terial. The Contractor shall furnish to the Engineer a signed certification from the manufacturer stating that the geocomposite drain proposed for use is capable of withstanding design loadings at all planned locations with
20、out appreciably decreasing the carrying capacity of the designed drainage voids for the entire height or length of the drain. 22.4 CONSTRUCTION 22.4.1 Preparation of Slopes Slopes shall be shaped to allow the full thickness of the specified slope protection and any bedding or filter gravel, where re
21、quired. Slopes shall not be steeper than the natural angle of repose of the slope specified in the contract. Where the slopes cannot be excavated to undisturbed material, the underlying material shall be compacted to 95% standard density per AASHTO T 99. 22.4.2 Bedding When called for on the plans,
22、a layer of filter gravel or filter fabric shall be placed on the slope immediately prior to placement of the riprap or slope paving. The layer of fil- ter gravel shall be shaped to provide the minimum thick- ness specified. 22.4.3 Filter Fabric When specified in the contract, filter fabric shall be
23、spread uniformly over the prepared slope or surface. The fabric shall be unrolled directly on the surface to the lines and dimensions shown. The filter fabric shall be lapped a minimum of 12 inches in each direction and shall be an- chored in position with approved anchoring devices. The Contractor
24、shall place the riprap in a manner that will not tear, puncture, or shift the fabric. Tracked or wheeled equipment will not be permitted on the fabric covered slopes. 22.4.4 DIVISION II-CONSTRUCTION 647 22.4.4 Geocomposite Drain Geocomposite drains shall be installed at locations shown on the plans,
25、 described in the special provisions, and where directed by the Engineer. Collection and dis- charge systems shall be installed as shown on the plans or as directed by the Engineer. Core material manufactured from impermeable plastic sheeting having connecting corrugations shall be placed with the c
26、orrugations approximately perpendicular to the drainage collection system. When only one side of the geocomposite drain is cov- ered with filter fabric, the drain shall be installed with the filter fabric side facing the embankment. The fabric fat- ing the embankment side shall overlap a minimum of
27、3 inches at all joints and wrap around the exterior edges a minimum of 3 inches beyond the exterior edge. If addi- tional fabric is needed to provide overlap at joints and wrap-around at edges, the added fabric shall overlap the fabric on the geocomposite drain at least 6 inches and be attached ther
28、eto. Should the fabric on the geocomposite drain be tom or punctured, the damaged section shall be replaced com- pletely or repaired by placing a piece of fabric that is large enough to cover the damaged area and provide a 6-inch overlap all around the damaged area. 22.4.5 Hand Placing Stones Where
29、hand placing of stones is specified, the larger stones shall be placed first with close joints. The larger stones shall be placed in the footing trench. Stones shall be placed with their longitudinal axis normal to the em- bankment face and arranged so that each stone above the foundation course has
30、 a three-point bearing on the under- lying stones. The foundation course is the course placed on the slope in contact with the ground surface. Bearing on smaller stones that may be used for chinking voids will not be acceptable. Placing of stones by dumping will not be permitted. Interstices shall b
31、e filled with smaller stones and spalls. 22.4.6 Machine-Placed Stones 22.4.6.1 Dry Placement Machine-placed stones shall be so placed so as to pro- vide a minimum of voids, and the larger stones shall be placed in the toe course and on the outside surface of the slope protection. The stone may be pl
32、aced by dumping and may be spread in layers by bulldozers or other suit- able equipment. At the completion of slope protection work, the footing trench shall be filled with excavated ma- terial, and compaction will not be required. 22.4.6.2 Underwater Placement When placed under water, free dumping
33、will not be permitted without written permission of the Engineer. Placement shall be by controlled methods using bottom dump buckets or wire rope baskets lowered through the water to the point of placement. 22.4.7 Wire-Enclosed Riprap (Gabions) 22.4.7.1 Fabrication The wire mesh shall be twisted to
34、form hexagonal openings of uniform size. The maximum linear dimension of the mesh opening shall not exceed 4% inches and the area of the mesh opening shall not exceed 8 square inches. The mesh shall be fabricated in such a manner as to be nonravelling. Nonravelling is defined as the ability to re- s
35、ist pulling apart at any of the twists or connections form- ing the mesh when a single wire strand in a section is cut. Gabions shall be fabricated so the sides, ends, lid, and diaphragms can be assembled at the construction site into rectangular baskets of the specified size. Gabions shall be of si
36、ngle unit construction-base, lid, ends, and sides shall be either woven into a single unit or one edge of these members connected to the base section of the gabion in a manner that strength and flexibility at the point of connection is at least equal to that of the mesh. Where the length of the gabi
37、on exceeds its horizontal width, the gabion shall be equally divided by diaphragms of the same mesh and gauge as the body of the gabions, into cells the length of which does not exceed the hori- zontal width. The gabion shall be furnished with the nec- essary diaphragms secured in proper position on
38、 the base in a manner that no additional tying at this junction will be necessary. All perimeter edges of the mesh forming the gabion shall be securely clip bound or selvedged so that the joints formed by tying the selvedges have at least the same strength as the body of the mesh. Selvedge wire used
39、 through all the edges (perimeter wire) shall not be less than 0.148-inch diameter (U.S. Wire Gage No. 9) and shall meet the same strength and coating specifications as the wire mesh. Tie and connection wire shall be supplied in sufficient quantity to securely fasten all edges of the gabion and di-
40、aphragms and to provide for at least four cross connecting wires in each cell whose height is equal to the width and at least two cross-connecting wires in each cell whose height is one-half the width of the gabion. Cross-connect- 648 HIGHWAY BRIDGES 22.4.7.1 ing wires will not be required when the
41、height of the cell is one-third the width of the gabion. Tie and connection wire shall meet the same strength and coating specifica- tions as the wire used in the mesh, except that it may be as much as two gages smaller. In lieu of tie wire, two gauge galvanized hog rings may be used to connect adja
42、cent baskets and to secure basket lids. Spacing of the hog rings shall not exceed 6 inches. Vertical joints in the completed work shall be staggered at approximately Y3 or YZ the length of the full baskets. 22.4.7.2 Installation The gabions shall be placed on a smooth foundation. Final line and grad
43、e shall be approved by the Engineer. Each gabion unit shall be assembled by binding to- gether all vertical edges with wire ties on approximately 6-inch spacing or by a continuous piece of connecting wire stitched around the vertical edges with a coil about every 4 inches. Empty gabion units shall b
44、e set to line and grade as shown on the plans or as directed by the Engi- neer. Wire ties, hog rings, or connecting wire shall be used to join the units together in the same manner as de- scribed above for assembling. Internal tie wires shall be uniformly spaced and securely fastened in each cell of
45、 the structure. A standard fence stretcher, chain fall, or iron rod may be used to stretch the wire baskets and hold alignment. The gabions shall be filled with stone carefully placed by hand or machine to assure alignment and avoid bulges with a minimum of voids. Alternate placing of rock and conne
46、ction wires shall be performed until the gabion is filled. After a gabion has been filled, the lid shall be bent over until it meets the sides and edges. The lid shall then be secured to the sides, ends and diaphragms with the wire ties or connecting wire in the manner described above for assembling
47、. 22.4.8 Grouted Riprap Stones shall be placed on the slope as specified in Ar- ticle 22.4.5 and shall be thoroughly moistened with water after placement. Grout shall be applied while the stone is moist and shall be worked into the interstices to com- pletely fill the voids. Where the depth is in ex
48、cess of 12 inches, the stone shall be placed in 12-inch lifts and each lift grouted prior to placement of the next lift. Succeeding lifts shall be constructed and grouted before grout in the previous lift has set. Grout shall be placed only when the weather is suitable and shall be protected from fr
49、eezing for at least 4 days. The surface shall be cured by covering with moist earth, wet rugs or curing blankets for at least 3 days after grout placement. Weep holes shall be provided through the riprap as shown on the plans or as directed by the Engineer. 22.4.9 Sacked Concrete Riprap Sacks shall
50、be filled with approximately 1 cubic foot of concrete, leaving room at the top to fold the sacks and re- tain the concrete during placement. Immediately after being filled, the sacks shall be placed and lightly trampled to conform with the earth face and with adjacent sacks. The first two courses sh
