SANS 10120-3 LG-1983 Code of practice for use with standardized specifications for civil engineering construction and contract documents Part 3 Guidance for design Section LG Pipe .pdf

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 . 3 Section LG-1383 Pipe jacking PAIW 3 : GUTDANCE FOR DESIGN SECTION LG Clause 1 . 1.1 1.1 1 1.1.2 1.2 l 2.1 1.3 1.3.1 1.3.2 1.3.3 1.3.

4、4 1.3.5 1.3.6 2 . 2.1 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5 2.3 2.3.1 7.3.2 2.3.3 7.3.4 2.4 2.5 2.5.1 2.5.2 2.5.3 2.5.4 3 . 4 . 5 . CONTENTS Page Fiumber PRE-TENDER CONSIDEPATIONS 1 . Investigations 1 . Pipe jacking under public transport routes 1 Information to be provided on soil conditions 1 dministr

5、ation 1 Safety precautions . 1 Documentation . 1 . Conditions of tendcr 1 . Condit.ions of contract 2 Preliminary construction and occupation 2 provision for alternative methods of construction 2 . Combined open trench and pipe jacking construction 2 Tolerances . 2 DESIGN REQUIREMENTS . 2 Pipc Jacki

6、ng Method 2 Ground Conclitions 2 Practicability and cconomics . 2 . Ground stability 2 Watcr intrusion 2 Soil strength 3 l.rictional resis1:oncc 3 . Pipe Sizes 3 Scope of SABS I200 LG 3 Gfncral 3 Concrete pipes . 3 Thrust pit length 3 Alchoring Service Pipe Against Flotation in Sleeve . 3 Tolernnces

7、 3 Economics 3 Generai 4 Tolerances where gradc and direction are important . 4 Cross-country oil pipelines and similar cases 4 APPLICABILITY OF OTHER CODES 4 TEST PROCEDURES . 4 QUALITY CONTROL AND OTIlER CONSIDE:P!TIONS 4 DRAWINGS Pipc Jacking using Concrete Pipcs 5 June 1983 Approved by the COUNC

8、IL OF TIIE SOUTll AFIUCAN RUREAU OF ST.ANDARIX SABS 0120 Part 3 Section LG-1983 Pipe jacking SABS 1200 LG : PIPE JACKING NOTE: The clause nunber(s) given at the beginning or after the heading of a clause is/are, unless otherwise stated, the number(s) of the relevant ciause(s) of SAW 1200 LG. PI?E-TE

9、NDER CONSIDERATIONS TNVESTIGATIONS Pipe Jacking under2ublic Transport Routt?. A pipeline may not be jacked under any national, proiIIcial, or municipal road (street) or under any railway track without prior permission from the authority that controls the relevant. road or track. Ascertain the requir

10、ements of the authority regarding details of precautions to be taken and the times and lengths of occupation periods during which preliminary construction and jacking may take place. (See also 1.3.3 below.) information to be Provided on Soil Conditions_ (Subclauses 8.2.1, 8.2.4, and 8.2.5). Unless f

11、ull information is made available to each tenderer, it is not possible for him to make an accurate assessment of the techniques required and the cost of carrying out the work, and then to submit a reasonable tender. Provide information on the characteristics of the soils likely to be encountered tog

12、ether with details of the water table, such as its rate of inflow and any tidal or seasonal changes. For particular types of soils include information on the following characterist.ics: a) Non-cohesive soils (sards, gravels, ballasts, and silts): l) Grading analysis of particle distribution; 2) perm

13、eability; 3) density; 1) 4) standard penetration test result (N. factor) (see Subclause 7.2 of SADS 1200 B) . b) Cohesive soils (clays, marls containing up to 20 X gravel and having a moisture content less than the value at the plastic limit, and limestone having a saturation moisture content of 20

14、% or greater): l) Tipparent cohesion or unconfined compressive strength; 2) density; 3) standard penetration test result (N. factor). C) Mixed soils (sand and clay, sand and silt., non-saturated clays and silts): 1) As in (a) and (b) above; 21 evidence of artesian or perched watcr tables; 3) pumping

15、 test results. d) ill material (mixed materials of recent deposit such as domestic refuse containing ash, vegetable matter, etc., and materials of varying content and compaction used for embankments for railways, roads, etc.) : As in (C) above with parricular reference to compaction. c) -. Ruck (har

16、d material of geological origin or other comparable hard inert material (concrete, brick, etc.) : 1) Geological type; 2) hardness factor. (See also Subclause 4.2 of Section LG of Part 5 of the code.) ADMINISTRATION Safety Precautions. Ensure that provision is made for comprehensive safety precaution

17、s to be applied - both underground whcre the pipeline is being jacked and on the surfacc where traffic may be flowing. Conditions of Ie. Include in the corditions of tender such of the following clauses as are applicable to the project (see also 1.3.4 below) : a) Installation of struct.ures under ro

18、ads, railway lines, and the like by jacking may be undertaken only by a contractor with experience of such operations. h) The Tenderers prices must make provision for the cost of checking the design of the structure to be jacked and, if necessary, its modification by the Contractor to suit the loads

19、 that will be imposed by his equipment during installation. C) The Tenderer must include (or state on the Detail. Sheets, if any) proposals for the method of installation, temporary track support, and required modifications to the structure to be jacked, and give drawings, specifications, and calcul

20、ations in sufficient detail to enable the merits of the proposals to be assessed. d) The Tenderer may submit alternative designs provided that he also submits prices for the scheme(s) detailed on thc drawings listed in the schedule of drawings or otherwise referred to in the tender docurneuts. C) Wh

21、ere an alternative design is offered, or where the project specification indicates that part of the design is to he prepared by the Contractor, the Tfnderer must submit with the tender, drawings alid calculations for the structure to be jacked that are in sufficient detail for the said design or par

22、t of tllc design to be assessed. f) The following information must bc submitted with the tender (or stilted on the Detail Sheets, if any): 1) Yull cletoils of all pipes; 2) the maximum jacking forces to be applied; 3) details (including drawings and calculations) of the proposed method of load trans

23、fer from the pipe to the thrust pit walls; 4) the proposed method of worki-rrg, i.e. location and number of t.hrust pits, whether intermediate jacking pipes will be used, and whether and where intermediate thrust pits will be required; l) Site irwestigations (In course of preparation). SRUS 0120 : P

24、art 3 Section K-l903 Pipe jacking 5) full details of the intsrmediilte jacking pipes, sleeve, rnd joint scalcr. Where an inspecticin pit has been excavated, a clause such ab the followink may also be incljdcd: An inspection pit has been opened at the east end to the depth of the invert of the pr:pos

25、ed sleeve. Should the Tenderer desire to make any other subsurface investigations, arrangements slould be made by the Tenderer with the Employer. No payment will be made by the Xmployer for any su-h investigations. Conditions of Contract (Subclause 5.4.2). Where the GCC do not form part of the contr

26、act ensure that -.-W the applicable conditions of contract protect the employer from claims arising from any accident or incident in or adjacent to the access pits. PI-elimir,ary Construction and Occup!. Frame a PSI,G clause to set out the requirements ascertained in terms of 1.1.1 above. Provision

27、for A1.rnative Methods of Construce. Wherever possil,le, provide scope for thz contractoi- to adopt “cut and cover“ construction instead of pipe jackiny. Combined Open Trench and Pipe *Tacking Construction. Where parts of a pipt?line lie beyond tie road, railway, service, or structure under which th

28、e pipeline is to pass, it may be possible to 1.ny those parts txonomically j.n open trench excavati.ons. In such a case exrcnd the specification to includ.2 ardinary trcnch excavation and backfilling, shoring of the trench, 1ayii:g or pi.pes in trenches, etc. , as necessary. ioicrances. (Sec 2.5.2 -

29、 2.5.4 below.) PIII.: JACKING MCTIIOI. Pipe jacking was introduced to facilitate constructitin of underground pipeJines in circumstances where disruption to traffic, services, and local environment should be mi:;imized. Although Lhe metliods of pipe jacking are similar and have been provcd to be suc

30、ce:;sful, conxactors and construction organizations have developed their own individual 1:echniques to achieve accuracy during jacking, to lengthen tile distance jacked, and to deal with poor yround conditions., The methods allow tolerances normally acceptable for sewer construction to be achi.eved

31、but, in certain conclitions such as unstable soils, it may not be possible to cnsurc that: the work will conform to these tolerances. Should it: be necessary to ensure a particular degree of accuracy, an in-situ invert may be cast after the main construction has been completed. As the fol-cos used t

32、o jack pipes through the ground are substantial, the design of the conc:ete pipes is critical. Give special attention to both the design and the manufdcture uf the pj.pes. llse centrifugally spun pipes that incorporate concentric reinforcement cages, and that can be designed to meet specific require

33、ments of loading both from the jacking forces and from superinposed loa?s occurring during and after constructon. Ensure that flexible joints are incorporated in all concrete jacking pipes, and design joints to resist the large forces inposed during installati.on. P1:acticability and Economics. To a

34、ssess the practicability and economics of jacking a pipe through the roils listed in 1.1.2 above, consider the following conditions: 2) Ground stability, both at the working face and above the Ilne of tlic pipe; Ir) the presence of watcr and the level of the permanent water table; C) the sol1 streng

35、th; d) fxjction between the sol1 and the concrete pzpe. Ground Stability. Ground stability is a critical item for considoration when pipe jacking r.s -pp contemplated. Jixamine non-cohesi.ve soils carefully and, if necessclry, undertake a detailed gcotechnical survey to ascertain compaction and grad

36、ing analysis. Sonic cohcsivc soils can become unstab:.e when the presence of excess water renders them plastic (see 2.2.3 bclciwi. Examine mixed soils and other material to be uacd for filling (embankments, etc.) and, if possible, excavate trial pits to assess the practicability of pipe jacking. Whc

37、re stability is in doubt, consider yeotechnical stabilization techniques. such n.s groutincl with cement, resin, or other suitable clietnical products. Water Intrusion. Soils that are stable in the ordinary way can bc rcndcred unstable in the presence of water. The instability is caused by water mov

38、ement through the soil which, in turn, is cauried by the differential head crcated by jacking a pipe below the watcr table. In some cases, for example in compact lxilJ.ast, water movement may not create difficulties at the shield, as there may be ample voi.ds to allow wotcr flow without soil flow. f

39、lowever, soil movement may occur above the jacked pipe owing to removal of iiner; which, i.n turn, causes redistribution of the granular psrtielcs with resulting settlement. Where thc presence of excessive watcr is known, specify that tlrc water table is to be 1owerc.d by the use c?f well-pointing,

40、a deep sump, or deep well pumping. 2; Generill conditions of contract for use in connection with works of civil engineering constructior, prepared under the auspices of the SAICE, SAACE, and SAFCEC and recornmended lry these bodies for general use, and also endorsed for general use by the civil Engi

41、neering Advisory Council. SABS 0120 Part 3 Section LG-1983 Pipe jacking Soil Strength. Most soils can be removed at the shield by means of shovels or pneumatically driven clay spades or points. Hock can be broken up by means of explosives or various splitting devices. Removal of rock can affect prog

42、ress depending on its position at the shield and the size of the face available for excavation. It is not possible to general.ize on conditions and any combination of soils must be assessed on the basis of information provided in terms of 3.1.2 above. It is important that such information provide th

43、e cohesion value, degree of compaction, and the bearing or compressive strength of the soil. Frictional Resistance. During the pipe jacking operation, frictional Eorces build up around the pipeline - as the line of pipes is advanced behind the shield. The frictional forces depend on the type of soil

44、, the depth of overburden, the length and diameter of the pipe being jacked, and the time taken by the operation. It is difficult to assess these forces accurately but, after years of experience, pipe jacking contractors have derived empirical values. As an approximate guide, frictional forces can b

45、e said to fall between 5 kN and 25 kN (0,5 t force and 2,5 t force) per square metre of external surface area, depending upon site conditions. (See also Subclause 3.1.12 of Section LT, of Part 5 of the code.) Iri the initial stages of jacking, impervious soils such as clay frequently offer low resis

46、tance because of the lubricating effect of trapped moisture. In later stages, however, reduction of this lubricating effect and heaving of the clay can cause increased resistance. Where jacking is to be carried out in soil conditions such as occur in embankments, in mi.xed faces, or at shallow depth

47、s with high surcharges, seek the advice of specialists. To reduce frictional resistance, specify a suit.able lubricant such as bentonite under pressure. If high frictiorlo!. resistance is expected, design for intermediate jacking stations to be placed at regular intervals in the pipeline. IIIE SIZES

48、 Scope oF SARS 12002 (Subclause 1.1:. Although the scope of Subclause 1.1 of SABS 1200 LG limits the P- applicability of that standardized peclflcaion to pipelines of dlarneter 3 000 nun , most of its clauses are also applicable to larger pipelines. General. With the exception that, where pipes of s

49、mall diameter (say, up to 300 mm) are to be jacked shc:rt distances (up to 25 m) through homogeneous material, they may be of steel or of concrete, pipes to be jacked are usually of concrete. Consult Jacking concrete pipes3) for diagram (see Drawing LG-3.1) and guidance on the design, specifica- tion, and construction by jacking of underground pipelines of diameters 900 rrm - 2 550 mm. Concrete Pipes. Consider the following factors when sc!ecting the diameter of the pipe: aj The smallest size for conventional hand cxcavatiori is about 900 mm; b) ?or long j