1、 Collection of SANS standards in electronic format (PDF) 1. Copyright This standard is available to staff members of companies that have subscribed to the complete collection of SANS standards in accordance with a formal copyright agreement. This document may reside on a CENTRAL FILE SERVER or INTRA
2、NET SYSTEM only. Unless specific permission has been granted, this document MAY NOT be sent or given to staff members from other companies or organizations. Doing so would constitute a VIOLATION of SABS copyright rules. 2. Indemnity The South African Bureau of Standards accepts no liability for any
3、damage whatsoever than may result from the use of this material or the information contain therein, irrespective of the cause and quantum thereof. SABS 0120 : Part 5 Section LB-1983 Bedding (pipes) PART 5 : CONTRACT ADMINISTRATION SECTION LB CONTENTS C3 ause Page Number START OF COWTRUCTION 1 Genera
4、l 1 . IMMEDIATELY AFTER THE HANDING OVER OF THE SITE 1 Program and Method of Working 1 Compactibility Factor of Selected Granular Material 1 . Reinforced Bedding 1 DURING CONSTRUCTION 1 Methods of Construction 1 Selection of bedding . 1 Placing of materials in bedding 1 Compaction of bedding 1 . Pla
5、cing concrete for Class A bedding 1 Blanket 1 Bedding cradle for flexible pipes l Compacting equipment 1 Filling at pipe joints and testing 2 Administration . 2 Relating class of pipe to class of bedding . 2 Selective methods of excavation ordered 2 Measurement and payment for provision of bedding m
6、aterial 2 QUALITY CONTROL AND OTHER CONSIDERATIONS . 2 Notes on Construction Failures 2 First Revision March 1983 This section of the code supersedes SABS 0120 : Part 5 : Section LB-1980 Approved by the COUNCIL OF THE SOUTH AFRICAN BUREAU OF STANDARDS SABS 0120 : Part 5 Section LE-1983 edding (pipes
7、) SABS 1200 LB : BEDDING (PIPES) NOTE: The clause number(s) given at the beginning or after the heading of a clause is/are unless otherwise stated, the number(s) of the relevant clause(s) of SABS 1200 LB. START OF CONSTRUCTION GENERAL. For the purposes of this part of the code, contract administrati
8、on starts with instructions to the contractor to commence work as set out in subclause 4.1 of Section 0. IMMEDIATELY AFTER THE HANDING OVER OF THE SITE PROGRAM AND METHOD OF WORKING. The contractor and the engineer should discuss and agree upon the program and method of working to ensure that sample
9、s of all bedding materials are available for testing early enough to avoid delaying the works. COMPACTIBILITY FACTOR OF SELECTED GRANULAR MATERIAL (Clauses 6 and 7). The contractor should lodge samples of granular material with the engineer for his approval before bedding and pipelaying are started.
10、 He should ensure that stockpiles of granular material do not become contaminated during the construction period. REINFORCED BEDDING. (See Subclause 3.2.3 of Section LB of Part 2 of the Code.) Where a concrete bedding is to be reinforced, the engineer should ensure that a reinforcement schedule is h
11、anded to the contractor early enough to eliminate the risk of delaying construction due to late delivery of steel. DURTNG CONSTRUCTION METHODS OF CONSTRUCTION Selection of Bedding (Subclause 3.4). The contractor should not wastefully dispose of excavated material that complies with the requirements
12、of Subclauses 3.1 and 3.2 of SABS l200 LB and that may be used for bedding cradles or selected fill blankets. Placing of Materials in Bedding (Subclause 5.1.3). In placing bedding, special care should be taken to ensure that no stones of maximum dimension exceeding 30 mm are placed within 150 nm of
13、the barrel, that all voids under the overhang of the pipes are filled, and that compaction is carried out at OMC uniformly on each side of the pipe so as not to cause any lateral or vertical displacement of the pipe. Compaction of Bedding (Subclause 5.1.4). To achieve the compaction of 90 % of modif
14、ied AASHTO maximum density required for bedding in terms of Clause 5.1.4 of SABS 1200 LB, the following procedure should be adopted: a) Ensure that the pipe is firmly supported underneath and at the sides, and that the prisms of material adjacent to the pipe can prevent lateral movement of the pipe
15、and can transmit vertical loads without undue settlement. Light compaction only should be applied to the material directly over the pipe. b) Machine compaction should not be used directly above the pipe until sufficient cover has been placed to ensure that machine compaction loads transmitted to the
16、 top of the pipe are no greater than would be imposed by normal road traffic over a pipeline with l m cover. C) If sand is used as bedding material, compaction may be obtained by saturation with water provided that a poker vibrator is used to compact the sand. Pipes should be secured against displac
17、ement by flotation. Placing Concrete for Class A Bedding (Subclause 5.2.l(a). The pipes should be supported and fixed to line and level by means of saddles or wedges placed between the supports and the pipe. Concrete should then be worked in one continuous operation under the pipe with vibrators and
18、 brought up uniformly on both sides of the pipeline to the required finished height (see Drawing LB-3(a) of SABS 1200 LB). Soft clay, putty, or mastic should be packed into the recesses of flexible joints to prevent the entry of mortar from the concrete. Vertical construction joints need not have a
19、gap but if preferred by the contractor to facilitate construction, a gap not exceeding 15 mm may be provided and should be fomed with a soft material that can be crushed easily if not renoved. (see also 2.3 above.) Blanket (Subclause 5.2.l(b) and 5.2.lCc). The period of 24 h and the time necessary f
20、or a strength of 15 MPa to be achieved, are provided to allow the bed to harden sufficiently to bear the loads that will be imposed on it during and immediately after the placing of the blanket, respectively. Bedding Cradle for Flexible Pipes (Subclause 5.3(a). Attention is drawn to the need in the
21、case of flexible pipes to carry the granular material over the top of the pipe as shown on Drawing m-2 of SABS 1200 LB. Compacting Equipment (Subclause 4.1). The contractor should provide suitable tools for tamping and ramming bedding and selected fill material round pipes of diameter up to 300 wa.
22、For pipes of larger diameter he should provide vibrating equipment for compacting such materials alongside the pipes. (See also Subclause 5.1.4 of SABS 1200 LB.) The contractor should provide the equipment required for carrying out on site the tests given in Clause 4 of Section LB of Part 3 of the c
23、ode. SABS 0120 : Part 5 Section LB-1983 edding (pipes) Filling at Pipe Joints and Testing (Subclause 5.1.3). Where pressure tests are specified, the contractor may prefer to backfill at the pipe joints and fittings after the pipeline has been subjected to a preliminary test and permission for such b
24、ackfilling has been given by the engineer. However, such a procedure is not recommended because a) it is likely to disrupt his program for the work; and b) any permission to backfill given by the engineer does not relieve the contractor of responsibility for rectifying leaks disclosed during the fin
25、al or “take-over“ tests. ADMINISTRATION Relating Class of Pipe to Class of Bedding. The contractor should notify the engineer as soon as possible whenever conditions at the bottom of the trench are found to be significantly different from those on which the choice of pipe and bedding classes was bas
26、ed. On being so notified, the engineer should, without delay, give new bedding instructions (such as ordering a change in the class of bedding, if irecessary). See also Subclause 2.1.3 of Section LB of Part 3 of the code.) Selective Methods of Excavation Ordered. Where the terms of PSLB 1.2 given in
27、 Subclause 3.2.1.2 of Section LB of Part 2 of the code are applicable to a contract, the contractor must provide and use excavating equipment and methods such that he obtains materials that are suitable for one or both types of bedding material. Measurement and Payment for Provision of Bedding Mater
28、ial (Subclause 8.2). Except that the project specification clause (PSLB 1.3) set out in Subclause 3.2.1.3 of Section LB of Part 2 of the code stipulates a 5 km freehaul instead of a no limit freehaul, the clause is significant in that it provides for a single rate for each of selected granular mater
29、ial and selected fill material. It anticipates that the rate for selected granular material may well be considerably higher than that for selected fill material, because selected fill material will invariably be available from the trench itself whereas at ledst some of the material complying with th
30、e requirements for selected granular material may have to be imported from greater distances. However, as he has tendered on the assumption that some material may be imported, the contractor is encouraged to use the material from alongside the trench in the most economical manner possible. Competiti
31、ve tendering should keep the rate for each as low as practicable on the basis of the information made available by the engineer and ascertainable by the contractor at the time of tendering. It is then in the contractors interest to select his material from alongside the trench carefully with a view
32、to using it (instead of importing) with a resultant total cost less than that assumed when tendering. QUALITY CONTROL AND OTHER CONSIDERATIONS NOTES ON CONSTRUCTION FAILURES. More reported pipeline failures are due to bad bedding than to inadequate pipe strength. Attention is drawn to the following
33、reported failure in order to alert both the engineer and the contractor to typical danger areas in which omissions can be very expensive: AC pipeline of nominal diameter 1 000 mm; 1 to 2 m cover; bedding nominally Class C; excavated material was sand and clay (PI 6 to 20) which was supersaturated during some portions of the construction period and very dry and cloddy at other times; material was thrown into trench and was neither worked around pipeline nor tamped. Pipes failed by flattening (some lost ovality when backfill load was removed). sabs pta
