1、Section 7 EARTH RETAINING SYSTEMS 7.1 DESCRIPTION This work shall consist of furnishing and installing earth retaining systems in accordance with the plans, these specifications, and the special provisions. Earth retaining systems include concrete and masonry gravity walls, reinforced concrete retai
2、ning walls, sheet pile and soldier pile walls (with and without ground an- chors or other anchorage systems), crib and cellular walls, and mechanically stabilized earth walls. 7.2 WORKING DRAWINGS Working drawings and design calculations shall be submitted to the Engineer for review and approval at
3、least 4 weeks before work is to begin. Such submittals shall be required (1) for each alternative proprietary or nonpropri- etary earth retaining system proposed as permitted or specified in the contract, (2) when complete details for the system to be constructed are not included in the plans, and (
4、3) when otherwise required by the special provisions or these specifications. Working drawings and design calcu- lations shall include the following: (a) Existing ground elevations that have been verified by the Contractor for each location involving con- struction wholly or partially in original gr
5、ound. (b) Layout of wall that will effectively retain the earth but not less in height or length than that shown for the wall system in the plans. (c) Complete design calculations substantiating that the proposed design satisfies the design parameters in the plans and in the special provisions. (d)
6、Complete details of all elements required for the proper construction of the system, including complete material specifications. (e) Earthwork requirements including specifications for material and compaction of backfill. (f) Details of revisions or additions to drainage sys- tems or other facilitie
7、s required to accommodate the system. (g) Other information required in the plans or special provisions or requested by the Engineer. The Contractor shall not start work on any earth re- taining system for which working drawings are required until such drawings have been approved by the Engineer. Ap
8、proval of the Contractors working drawings shall not relieve the Contractor of any of his responsibility under the contract for the successful completion of the work. 7.3 MATERIALS 7.3.1 Concrete 7.3.1.1 Cast-in-Place Cast-in-place concrete shall conform to the require- ments of Section 8, “Concrete
9、 Structures.” The concrete shall be Class A unless otherwise indicated in the contract documents. 7.3.1.2 Pneumatically Applied Mortar Pneumatically applied mortar shall conform to the requirements of Section 24, “Pneumatically Applied Mortar.” 7.3.1.3 Precast Elements The materials, manufacturing,
10、storage, handling, and erection of precast concrete elements shall conform to the requirements in Article 8.13, “Precast Concrete Members.” Unless otherwise shown on the plans or on the approved working drawings, Portland cement con- crete used in precast elements shall conform to Class A (AE) with
11、a minimum compressive strength at 28 days of 4,000 psi. 7.3.1.4 Segmental Concrete Facing Blocks Masonry concrete blocks used as wall facing elements shall have a minimum compressive strength of 4,000 psi and a water absorption limit of 5%. In areas of repeated freeze-thaw cycles, the facing blocks
12、shall be tested in ac- cordance with ASTM C 1262 to demonstrate durability. The facing blocks shall meet the requirements of ASTM 515 516 HIGHWAY BRIDGES 7.3.1.4 C 1372, except that acceptance regarding durability under this testing method shall be achieved if the weight loss of each of 4 of the 5 s
13、pecimens at the conclusion of 150 cy- cles does not exceed 1% of its initial weight. Blocks shall also meet the additional requirements of ASTM C 140. Facing blocks directly exposed to spray from deiced pave- ments shall be sealed after erection with a water resistant coating or be manufactured with
14、 a coating or additive to increase freeze-thaw resistance. 7.3.2 Reinforcing Steel Reinforcing steel shall conform to the requirements of Section 9, “Reinforcing Steel.” 7.3.3 Structural Steel Structural steel shall conform to AASHTO M 270 (ASTM A 709) Grade 36 unless otherwise specified. 7.3.4 Timb
15、er Timber shall conform to the requirements of Section 16, “Timber Structures” and Article 4.2.2, “Timber Piles.” 7.3.5 Drainage Elements 7.3.5.1 Pipe and Perforated Pipe Pipe and perforated pipe shall conform to subsections 708 and 709 of the AASHTO Guide SpeciJcations for Highway Construction. 7.3
16、.5.2 Geotextile Geotextile shall conform to AASHTO M 288. 7.3.5.3 Permeable Material Permeable material shall conform to subsection 704 of the AASHTO Guide SpeciJcations for Highway Con- struction unless otherwise specified in the contract or the approved working drawings. 7.3.5.4 Geocomposite Drain
17、age Systems Geocomposite drainage systems shall conform to the requirements specified in the special provisions or the ap- proved working drawings. 7.3.6 Structure Backfill Material 7.3.6.1 General All structure backfill material shall consist of material free from organic material or other unsuitab
18、le material as determined by the Engineer. Gradation will be determined by AASHTO T 27. Grading shall be as follows unless oth- erwise specified. Sieve Size Percent Passing 3 in. 1 O0 No. 4 35-100 No. 30 20-100 No. 200 0-15 7.3.6.2 Crib and Cellular Walls Structure backfill material for crib and cel
19、lular walls shall be of such character that it will not sift or flow through openings in the wall. For wail heights over 20 feet (6 meters), the following grading shall be required: Sieve Size Percent Passing 3 in. 1 O0 No. 4 25-70 No. 30 5-20 No. 200 0-5 7.3.6.3 Mechanically Stabilized Earth Walls
20、Structure backfill material for MSE walls shall consist of material free from organic material or other unsuitable material as determined by the Engineer. Gradation shall be determined by AASHTO T 27. Grading shall be as fol- lows unless otherwise specified: Sieve Size Percent Passing 4 in.+ 1 O0 No
21、. 40 0-60 No. 200 0-15” +For the soil to be considered to be nonaggressive, the maximum soil particle size for geosynthetic reinforce- ment shall be 0.75 inches unless full scale installa- tion damage tests are conducted in accordance with ASTM D 5818, or if epoxy coatings are used for steel reinfor
22、cements. *Plasticity index (PI), as determined by AASHTO T 90, shall not exceed 6. The material shall exhibit an angle of internal friction of not less than 34”, as determined by the standard Di- 7.3.6.3 DIVISION II-CONSTRUCTION 5 17 rect Shear Test, AASHTO T 236, on the portion finer than the No. 1
23、0 sieve, utilizing a sample of the material compacted to 95% of AASHTO T 99, Methods C or D (with oversized correction as outlined in Note 7) at optimum moisture content. No testing is required for backfills where 80% of the sizes are greater than 0.75 inches. The materials shall be substantially fr
24、ee of shale or other soft, poor durability particles. The material shall have a magnesium sulfate soundness loss of less than 30% after four cycles or a sodium sulfate soundness loss of less than 15% after five cycles determined in accordance with AASHTO T 104. The soil shall also have an organic co
25、n- tent of less than or equal to 1% measured in accordance with AASHTO T 267 for material finer than the No. 10 sieve. The soil backfill electrochemical requirements for steel soil reinforcement are as follows: pH of 5 to 10 Resistivity of not less than 3,000 ohm-cm Chlorides not greater than 100 pp
26、m Sulfates not greater than 200 ppm If the resistivity is greater than or equal to 5,000 ohm-cm, the chlorides and sulfates requirements may be waived. The soil backfill electrochemical requirements for per- manent geosynthetic reinforcement are as follows: pH of 4.5 to 9 for permanent structures 3
27、to 10 for temporary structures Recommended test methods for soil chemical property determination include AASHTO T 289 for pH, AASHTO T 288 for resistivity, AASHTO T 291 for chlorides, and AASHTO T 290 for sulfates. 7.4 EARTHWORK 7.4.1 Structure Excavation Structure excavation for earth retaining sys
28、tems shall conform to the requirements of Section 1, ?Structure Ex- cavation and Backfill,? and as provided below. 7.4.2 Foundation Treatment Foundation treatment shall conform to the require- ments of Article 1.4.2, ?Foundation Preparation and Con- trol of Wate? unless otherwise specified or includ
29、ed in the approved working drawings. If subexcavation of foundation material is indicated, the Contractor shall perform the excavation to the limits shown. Materials excavated shall be replaced with structure backfill mate- rial meeting the requirements for the particular earth re- taining system to
30、 be constructed unless a different mate- rial is specified in the special provisions. The material shall be compacted to a density not less than 95% of the maximum density as determined by AASHTO T 99, Methods C or D (with oversize correction as outlined in Note 7). 7.4.3 Structure Backfill Placemen
31、t of structure backfill material shall con- form to the requirements of Articles 1.4.3 and 7.6. Material used shall conform to the requirements of Arti- cle 7.3.6. 7.5 DRAINAGE Drainage facilities shall be constructed in accor- dance with the details shown on the plans or approved working drawings,
32、the special provisions, and these Spec- ifications. 7.5.1 Concrete Gutters Concrete gutters shall be constructed to the profile in- dicated on the plans or the approved working drawings. Pneumatically applied mortar shall conform to the re- quirements of Section 24, ?Pneumatically Applied Mor- tar.?
33、 Outlet works shall be provided at sags in the profile, at the low ends of the gutter, and at other indicated loca- tions. 7.5.2 Weep Holes Weep holes, if specified, shall be constructed at the locations shown on the plans or the approved working drawings. A minimum of 2 cubic feet of permeable mate
34、- rial encapsulated with geotextile shall be placed at each weep hole. Joints between precast concrete retaining wall face panels which function as weep holes shall be covered with geotextile. The geotextile shall be bonded to the face pan- els with adhesive conforming to Federal Specification MMM-A
35、-121. The face panels which are to receive the geotextile shall be dry and thoroughly cleaned of dust and loose materials. 518 HIGHWAY BRIDGES 7.5.3 7.5.3 Drainage Blankets 7.6 CONSTRUCTION Drainage blankets consisting of permeable mate- rial encapsulated in geotextile, collector pipes, outlet pipes
36、 and clean out pipes shall be constructed as shown on the plans or the approved working drawings. The subgrade to receive the geotextile shall con- form to the compaction and elevation tolerance specified and shall be free of loose or extraneous material and sharp objects that may damage the geotext
37、ile during installation. The geotextile shall be stretched, aligned, and placed in a wrinkle-free manner. Adjacent borders of the geotextile shall be overlapped from 12 to 18 inches. Should the geotextile be damaged, the torn or punctured section shall be repaired by placing a piece of geotextile th
38、at is large enough to cover the damaged area and to meet the overlap requirement. The permeable material shall be placed in horizontal layers and thoroughly consolidated along with and by the same methods specified for structure backfill. Ponding and jetting of permeable material or structure backfi
39、ll material adjacent to permeable material will not be per- mitted. During spreading and compaction of the perme- able material and structure backfill or embankment ma- terial, a minimum of 6 inches of such material shall be maintained between the geotextile and the Contractors equipment. The perfor
40、ated collector pipe shall be placed within the permeable material to the flow line elevations shown. Outlet pipes shall be placed at sags in the flow line, at the low end of the collector pipe, and at other locations shown or specified. Rock slope protection, when required at the end of outlet pipes
41、, shall conform to the details on the plans or approved working drawings and the require- ments in Section 22, “Slope Protection.” Cleanout pipes shall be placed at the high ends of col- lector pipes and at other locations as specified. 7.5.4 Geocomposite Drainage Systems Geocomposite drainage syste
42、ms shall be installed at the locations shown on the plans or the approved working drawings. The geocomposite drainage material shall be placed and secured tightly against the excavated face, lag- ging or back of wall as specified. When concrete is to be placed against geocomposite drainage materials
43、, the drainage material shall be protected against physical dam- age and grout leakage. The construction of earth retaining systems shall conform to the lines and grades indicated on the plans or working drawings or as directed by the Engineer. 7.6.1 Concrete and Masonry Gravity Walls, Reinforced Co
44、ncrete Retaining Walls Stone masonry construction shall conform to ,the re- quirements of Section 14, “Stone Masonry.” Concrete construction shall conform to the requirements of Section 8, “Concrete Structures.” Reinforced concrete block ma- sonry shall conform to the requirements of Section 15, “Co
45、ncrete Block and Brick Masonry.” Vertical precast concrete wall elements with cast-in- place concrete footing support shall be adequately sup- ported and braced to prevent settlement or lateral dis- placement until the footing concrete has been placed and has achieved sufficient strength to support
46、the wall ele- ments. The exposed face of concrete walls shall receive a Class 1 finish as specified in Section 8, “Concrete Struc- tures, unless a special architectural treatment is specified on the plans, the special provisions, or the approved work- ing drawings. 7.6.2 Sheet Pile and Soldier Pile
47、Walls This work shall consist of constructing continuous walls of timber, steel or concrete sheet piles, and the con- structing of soldier pile walls with horizontal facing ele- ments of timber. steel or concrete. 7.6.2.1 Sheet Pile Walls Steel sheet piles shall be of the type and weight indi- cated
48、 on the plans or designated in the special provisions. Steel sheet piles shall conform to the requirements of AASHTO M 202 (ASTM A 328), AASHTO M 270 (ASTM A 709) Grade 50, or to the specifications for “Pil- ing for use in Marine Environments” in ASTM A 690. Painting of steel sheet piles, when requi
49、red, shall conform to Article 13.2. Timber sheet piles, unless otherwise specified or per- mitted, shall be treated in accordance with Section 17, “Preservative Treatment of Wood.” The piles shall be of the dimensions, species, and grade of timber shown on the plans. The piles may be either cut from solid material or made by building up with three planks securely fastened 7.6.2.1 DIVISION II-CONSTRUCTION 519 together. The piles shall be drift sharpened at their lower ends so as to wedge adjacent piles tightly together during driving. Concrete sheet piles shall conform to the details shown
