SANS 10120-5 D-1982 Code of practice for use with standardized specifications for civil engineering construction and contract documents Part 5 Contract administration Section D Ear.pdf

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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 D-1982 Earthworks PART 5 : CONTRACT ADMINISTRATION SECTION D CONTENTS Clause 1 . 1 .l 2 . 2.1 2.2 3 . 3.1 3.1 . 1 3.1.2 3.1.3

4、3.1.4 3.1.5 3.2 3.2.1 3.2.2 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8 3.2.9 4 . Page Number START OF CONSTRUCTION 1 General 1 . IMMEDIATELY AFTER THE HANDING OVER OF THE SITE 1 General . 1 Existing Services 1 DURING CONSTRUCTION 1 Methods of Construction . 1 Clearing and stripping of site and conservation

5、 of topsoil . 1 Classification . 1 Safeguarding . 1 Explosives 1 Dealing with material that has become slushy or has acquired a low shear vane reading . 2 Administration . 2 Backfilling . 2 Safeguarding . 2 Explosives 2 Advice on blasting . 2 Dealing with water . 4 Disposal of surplus material . 4 D

6、etermination of field densities . 4 Computation of quantities 4 Temporary stockpiling 5 QUALITY CONTROL AND OTHER CONSIDERATIONS . 5 First Revision March 1982 This section of the code supersedes SABS 0120 : Part 5 : Section 0-1979 Approved by the COUNCIL OF THE SOUTH AFRICAN BUREAU OF STANDARDS ISBN

7、 0-626-06169-5 SABS 0120 : Part 5 Sect ion D-1982 Earthworks SECTION 1200 D : EARTHWORKS 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 D. 1. START OF CONSTRUCTION 1 .l GENERAL.

8、For the purposes of this part of the code contract administration 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 GENERAL. The engineer should give immediate attention to the matters set out in 2.2 b

9、elow to ensure that the start of the contractors program is not adversely affected by lack of information. EXISTING SERVICES (Subclause 5.1.2). The engineer should order, and the contractor should carry out, further investigations to detect and expose service lines in those areas where the design en

10、gineer has not been able to provide specific infor- mation. (See also Subclause 2.6 of Section A.) DURING CONSTRUCTION METHODS OF CONSTRUCTION Clearing and Stripping of Site and Conservation of Topsoil. See Subclause 1.3.9.2 of Section D of Part 3 of the code. Classification (Subclause 3.1.1) Change

11、s in classification. The contractor should immediately inform the engineer as and when the nature of the material being excavated changes to the extent that a new classification for further excavation is warranted. Failure on the part of the contractor to advise the engineer timeously should not pre

12、vent the engineer from classifying, in accordance with the correct classification procedure and to the best of his ability, the various materials occurring in the excavation. Classes of excavation (Subclause 3.1.2) a) Soft excavation. Material capable of sustaining plant life and removed to a depth

13、of 150 mm or as otherwise ordered, for use as topsoil, is classified as soft excavation. b) Hard rock excavation. Unweathered or undecomposed rock in thick ledges, bedded deposits, or conglomerate deposits so firmly cemented together as to present all the characteristics of solid rock that cannot be

14、 efficiently loosened, dislodged, or excavated without the use of explosives is generally classified as hard rock excavation. Boulder excavation Class A (Subclause 3.1.2(d). The inclusion in the definition of boulder excavation Class A of the phrase “40 % by volume of boulders“ is an impor- tant cri

15、terion which has the effect of changing the classification of a particular material from “boulder Class A“ to “hard rock“ as the plan dimensions of the exca- vation change from those of a large open area such as a road cutting or a foun- dation for a major structure to those of a confined area or tr

16、ench-like shape such as the individual footings for a structure or a pipe trench. Safeguardin (Subclause 5.1.1.2) The enginee? may order additional lateral support if he considers this to be necessary. As the senior professional engineer on site he may be found negligent in the event of an accident

17、resulting from his failure to order such support BUT he should not exercise this right in an unreasonable manner, and he should not cause the contractor extra costs unnecessarily. The contractor should avoid the dangers of loading the surface adjacent to an exca- vation with excavated material or ma

18、chinery, particularly where bedding planes or seepage may affect the stability of the excavation. (See Drawing DB-5.1 in Section DB for an example of the safe placement of excavated material and pipes.) Explosives (Subclause 5.1.1.3) Stray currents may arise in the vicinity of electrified railway li

19、nes, cathode pro- tected pipelines, transformers, overhead power lines, and other similar situations. Special detonators are available and should be used for blasting in such high risk areas to avoid accidents. Attention is drawn to the monitoring services available from manufacturers of explosives

20、whereby the effects of blasting in the vicinity of vulnerable points may be assessed. (See also Subclause 3.2.3 of Section D of Part 2 of the code.) SABS 0120 : Part 5 Section D-1982 Earthworks Dealing with Material that has Become Slushy or has Acquired a Low Shear Vane Readin . Where a foundation

21、has been over-excavated and low areas have been back- illed with sand and subsequently well compacted from the surface and the sand is + relatively thin, the engineer should carry out tests to determine whether the sand density is satisfactory. Where the backfilled sand layer is relatively thick and

22、 a substantial delay has occurred between the placing and the compacting of the sand, the upper 200 mm to 250 mm of sand may be of adequate density but the lower zone will not have attained an adequate density because of its high moisture content. As the sand is not free draining, it will not be pos

23、sible to compact the lower zone adequately. The sand should therefore be excavated together with any softened underlying clay, replaced with sand of suitable moisture content, and immediately compacted in layers to about 100 % of modified AASHTD maximum density. (See also 3.2.1 below.) ADMINISTRATIO

24、N Backfillin (Subclauses 3.3.2 and 8.3.3). The cost of the temporary stockpiling of material ezcavated from foundations and its subsequent removal and placing as back- fill behind the completed structure is regarded as part of the cost of excavation. The contractor will be paid for “double handling“

25、 only where such an operation is scheduled or ordered in writing by the engineer for a particular reason. Safeguardin (Subclause 5.1.1.2) dent of the excavator and of the competent person is required in terms of the Factories, Machinery and Building Work Act, 1941 (Act 22 of 1941), to be in writing.

26、 The engineer should ensure that he receives from the contractor a copy of each such appointment. In terms of Subclause 5.1.1.2(d) of SABS 1200 D, the engineer may order the contractor to provide additional shoring. If the engineer considers it necessary to give such an order, he should do so in wri

27、ting. In the event of an accident causing injury or death the courts will hold the employer and the contractor jointly responsible unless the contract clearly lays the responsibility on one of the par- ties. Subclause 5.1.1.2(d) of SABS 1200 D makes it clear that in ordering addi- tional lateral sup

28、port the engineer does not in any way relieve the contractor of his responsibility. (See Appeal Court ruling as set out in Subclause 4.1.1 of Sec- tion DB.) Ex losives (Subclause 5.1.1.3) -e-7- The Exp osives Act, 1956 (Act 26 of 1956), does not require that the engineer should examine the records k

29、ept by the contractor in respect of blasting oerations and the engineers acceptance of such records does not s.ignify approval: e is, however, the senior professional engineer responsible for the works and may be found negligent if he has permitted a contractor or workman who has no certificate to b

30、last. Prior to blasting near any structure close to the works, the engineer and the contractor together should inspect the structure, note its state of repair, and take photographs of any parts showing signs of structural deterioration. Advice on Blastin 1) Inclined versus vzrtical holes a) Where in

31、clined drilling is practised, the angle from the vertical is usuallv of the order of 20 ; the advantages of this technique are as follows: 1) Working conditions are safer, whether the operations are at the crest of the quarry or on the quarry floor. 2) A stable face (of particular importance when ne

32、ar the boundary of an excavation) is created. 3) Backbreak in the collar area of the hole is reduced. 4) Fewer boulders are derived from the stemmed portion of the hole. 5) Easier breaking conditions are obtained in the toe area of the hole because of the increased breaking angle relative to the qua

33、rry floor and, because of the ver- tical or “lifting“ component associated with the throw from an inclined hole, this factor can be used to sood effect to assist in the overcoming of the “choke“ effect inherent in the blasting of numerous rows of holes. 6) Usually less over-drill is required resulti

34、ng in wall, and in consequence it is easier to collar the is drilled. 1) The contents of Subclause 3.2.4 have been provided by A.F. Chief Explosives Engineer of AECI Limited. less shattering of the foot- holes when the next lower bench Goetzsche, A.C.S.M., M.I.M.M., SABS 0120 : Part 5 Section D-1982

35、 Earthworks 7) Whilst serious backbreak problems associated with vertical holes often make it dangerous or even impossible to place drilling equipment close enough to the face to avoid the drilling of excessive burden (vertical holes may also cause fragmen- tation and toe problems), an inclined benc

36、h tends to exibit greater stability. Also, as the “horizontal“ burden is greater than the true burden by a factor of 1,064 for a hole inclination of 20 “, holes are collared slightly further back, making it necessary to deviate only rarely from the required line of drilling. b) The following are som

37、e of the more serious disadvantages of inclined drilling: 1) By far the most important disadvantage is the difficulty of achieving drilling accuracy (setting-up is simple with vertical holes but errors increase with the angle of inclination and deviation tends to be greater for inclined holes). 2) T

38、he most serious occurences of flyrock can probably be attributed to inclined holes that have been drilled too flat, resulting in gross underburdening of the face in the vicinity of the toe. c) The following are disadvantages of inclined drilling with particular reference to the operating costs and t

39、echnical problems associated with large rotary drills, the use of which is gaining favour particularly in large opencast operations: 1) The available pull-down force decreases with increase in hole inclination, which results in a corresponding reduction in penetration rate. 2) The life of the bit an

40、d the life of the stabilizer are reduced with inclined drilling. 3) Drilling time per metre drilled is longer. 4) Much closer, time-consuming supervision is required to ensure accurate alignment of inclined holes. 3.2.4.2 Extent of overdrillin . Holes should be overdrilled to ensure their breaking o

41、ut cleanly to floor levef. Vertical holes should be overdrilled to the extent of at least one-third of their burden but with inclined holes it is usually possible to reduce the amount of overdrilling necessary. Due allowance should always be made for sludge and drill cuttings in the bottom of a hole

42、. 3.2.4.3 Controlled blasting techniques a) Presplitting 1) General. Presplitting is the technique most often used for surface blasting and is particularly suited to forming the sidewalls of cuttings. It is not successful for relatively confined excavations such as foundation pits where the presplit

43、 tends to be ineffective at the corners of the excavation. Presplitting involves the drilling of holes along the boundary line of the final face, the light charging of these holes, and the firing of them before the main blast (i.e. the blasting is not to a free face), thus leaving a clean, smooth fa

44、ce after the main blast. The main advantages to be gained from employing this tech- nique are as follows: i) Maximum safety is afforded when work is carried out below the face. ii) A minimum amount of concrete is required if the excavation is to be concrete-lined. iii) A minimum amount of rock is re

45、quired to be removed if a minimum thickness of concrete is specified. 2) Presplitting theory. The theory behind presplitting is, briefly, as follows: When charges in adjacent holes are fired simultaneously the two sets of compressive shock waves collide and create a tension zone between the holes, a

46、long which the rock tends to shear. 3) Drilling of presplit holes. Accurate drilling is of the utmost importance in presplitting. This tends to limit the height of face over which the technique can be used effectively. Deviation should be limited, if possible, to 0,15 m but must not in any event exc

47、eed 0,3 m. The spacing of holes is usually as follows: Hole diameter, Hole spacing, mm m 35 0745 50 096 75 0,75 100 1,20 4) Type of explosive. To obtain a split it is necessary to fire a line of vertical holes instantaneously. This is best done by means of detonating fuse which detona- tes at the ra

48、te of 6 000 m/s. The explosive charge may be of any type or grade as long as it is suited to the conditions in the holes (e.g. gelignite or dynagel in wet holes). To facilitate stemming, normal practice is to use cartridged explosive having a diameter of approximately half that of the hole. 5) Preca

49、utions to be taken in presplitting. Two factors must be kept in mind when presplitting is carried out: SABS 0120 : Part 5 Sect ion D-1982 Earthworks i) Firstly, in certain situations lateral displacement may occur. An example of such a situation is the widening of a cutting in which a smooth finish to the side- wall is specified. The presplit may well be correctly charged with, say, 25 mm X 200 mm cartridges spaced at 0,4 m centres in holes drilled 0,6 m apart. With such a charge, the charge per metre of borehole length is 0,325 kg. If, for instance, the cutting has to be widened by 6 m