1、BRITISH STANDARD BS 1377-7: 1990 Incorporating Amendment No. 1 Methods of test for Soils for civil engineering purposes Part 7: Shear strength tests (total stress) UDC 624.131.3:620.176BS1377-7:1990 This British Standard, having been prepared under the direction of the Road Engineering Standards Pol
2、icy Committee, was published under the authority of the Board of BSI and comes intoeffect on 29 June 1990 BSI 01-1999 The following BSI references relate to the work on this standard: Committee reference RDB/38 Draft for comment 89/11041 DC ISBN 0 580 18264 9 Committees responsible for this British
3、Standard The preparation of this British Standard was entrusted by the Road Engineering Standard Policy Committee (RDB/-) to Technical Committee RDB/38, upon which the following bodies were represented: Association of Consulting Engineers British Civil Engineering Test Equipment Manufacturers Associ
4、ation County Surveyors Society Department of the Environment (Building Research Establishment) Department of the Environment (Property Services Agency) Department of Transport Department of Transport (Transport and Road Research Laboratory) Coopted members Amendments issued since publication Amd. No
5、. Date of issue Comments 8262 November 1994 Indicated by a sideline in the marginBS1377-7:1990 BSI 01-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Determination of shear strength by the laboratory vane method 1 3.1 General 1 3.2 Apparatus 1 3
6、.3 Procedure 2 3.4 Calculations 3 3.5 Test report 3 4 Determination of shear strength by direct shear (small shearbox apparatus) 3 4.1 General 3 4.2 Apparatus 4 4.3 Checking and preparation of apparatus 5 4.4 Preparation of specimen 5 4.5 Test procedure 7 4.6 Calculations and plotting 9 4.7 Test rep
7、ort 11 5 Determination of shear strength by direct shear (large shearbox apparatus) 11 5.1 General 11 5.2 Apparatus 12 5.3 Measurement of apparatus 13 5.4 Preparation of large shearbox specimen 13 5.5 Test procedure 15 5.6 Calculations and plotting 16 5.7 Test report 17 6 Determination of residual s
8、trength using the small ring shear apparatus 17 6.1 General 17 6.2 Apparatus 17 6.3 Preparation of test specimen 18 6.4 Test procedure 18 6.5 Calculations 19 6.6 Test report 19 7 Determination of the unconfined compressive strength 20 7.1 General 20 7.2 Load frame method 20 7.3 Autographic method 22
9、 8 Determination of the undrained shear strength in triaxial compression without measurement of pore pressure (definitive method) 23 8.1 General 23 8.2 Apparatus 24 8.3 Preparations of specimens 24 8.4 Test procedure 25 8.5 Plotting and calculations 26BS1377-7:1990 ii BSI 01-1999 Page 8.6 Test repor
10、t 27 9 Determination of the undrained shear strength in triaxial compression with multistage loading and without measurement of pore pressure 27 9.1 General 27 9.2 Apparatus 28 9.3 Preparation of specimens 28 9.4 Test procedure 28 9.5 Plotting and calculations 28 9.6 Test report 29 Appendix A Typica
11、l test data and calculation forms 40 Figure 1 Laboratory vane apparatus 30 Figure 2 Details of shearbox 31 Figure 3 Typical general arrangement of shearbox apparatus 32 Figure 4 Typical arrangement of ring shear apparatus 33 Figure 5 Typical load frame for unconfined compression test 34 Figure 6 Bar
12、relling correction grid sheet 35 Figure 7 Typical autographic unconfined compression test apparatus 36 Figure 8 Test chart for unconfined compression test 37 Figure 9 Overlay mask for unconfined compression test chart 38 Figure 10 Typical details of triaxial cell 39 Figure 11 Membrane correction gra
13、ph 39 Publications referred to Inside back coverBS1377-7:1990 BSI 01-1999 iii Foreword This Part of BS 1377 has been prepared under the direction of the Road Engineering Standard Policy Committee. It is a part revision of clause 5 of BS1377:1975 which is superseded by amendment. BS 1377 was first pu
14、blished in1948 and first appeared in metric form in 1975. BS 1377:1975 which has now been withdrawn is replaced by the following Parts of BS1377:1990: Part 1: General requirements and sample preparation; Part 2: Classification tests; Part 3: Chemical and electro-chemical tests; Part 4: Compaction-re
15、lated tests; Part 5: Compressibility, permeability and durability tests; Part 6: Consolidation and permeability tests in hydraulic cells and with pore pressure measurement; Part 7: Shear strength tests (total stress); Part 8: Shear strength tests (effective stress); Part 9: In-situ tests. Reference
16、should be made to Part 1 for further information about each of the Parts. It has been assumed in the drafting of this British Standard that the execution of its provisions is entrusted to appropriately qualified and experienced personnel. A British Standard does not purport to include all necessary
17、provisions of a contract. Users of British Standard are responsible for their correct application. Compliance with a British Standard does not itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages1to 48, an
18、inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on theinside front cover.iv blankBS1377-7:1990 BSI 01-1999 1 1 Scope This part of BS 1377 describes methods of test for dete
19、rmining shear strength parameters of soils in terms of total stresses, or (in the case of drained direct shear tests) in terms of effective stresses which are equal to total stresses. None of these procedures therefore requires measurement of pore water pressure, which is covered in Part 8 of BS1377
20、. Shear strength is determined either by measuring the shearing force causing failure (direct shear tests), or by derivation from the measured compressive strength (unconfined or triaxial compression tests). Reference is made to Part 1 of BS 1377 for general requirements that are relevant to all Par
21、ts of this standard, and to Parts 1 and 4 for methods of preparation of soil and of test specimens. Direct shear tests (clauses 3 to 6) comprise: a) laboratory vane test procedure, for soft to firm cohesive soils; b) small shearbox procedures for determining the angle of shear resistance of cohesion
22、less soils, and the drained peak and residual shear strength parameters of cohesive soils; c) large shearbox procedures for determining similar properties of gravelly soils, or on large block samples; d) small ring shear procedure for drained residual shear strength parameters of remoulded clays. Co
23、mpression tests (clauses 7 to 9) comprise: e) unconfined compression test procedure, in the laboratory and in a portable apparatus for use on site; f) triaxial compression test procedure from which the undrained shear strength is derived; g) triaxial compression test procedure in several stages on o
24、ne specimen, for deriving undrained shear strength. The unconfined compression test procedure using portable apparatus, and the single-stage triaxial compression test, are similar in principle to those given in the 1975 Standard. All the other procedures are new additions. NOTEThe titles of the publ
25、ications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this Part of BS 1377 the definitions given in 2.1 of BS 1377-1:1990 apply, together with the following. 2.1 unconfined compression strength (q u ) the compressive strength at failure of a spe
26、cimen subjected to uniaxial (unconfined) compression. For a saturated clay, q u= 2c u where c uis the undrained shear 2.2 sensitivity the ratio of the undrained shear strength of an undisturbed clay specimen to that of the same specimen after remoulding at the same moisture content 2.3 vane shear st
27、rength (t v ) the shear strength of a soil as determined by applying a torque in the vane shear test 2.4 undrained shear strength (c u ) the shear strength of a soil under undrained conditions, before drainage of water due to application of stress can take place 2.5 residual strength the shear stren
28、gth which a soil can maintain when subjected to large shear displacement after the peak strength has been mobilized 3 Determination of shear strength by the laboratory vane method 3.1 General This method covers the measurement of the shear strength of a sample of soft to firm cohesive soil without h
29、aving to remove it from its container or sampling tube. The sample therefore does not suffer disturbance due to preparation of a test specimen. The method may be used for soils that are too soft or too sensitive to enable a satisfactory compression test specimen to be prepared. The shear strength of
30、 the remoulded soil, and hence the sensitivity, can also be determined. The requirements of Part 1 of this standard, where appropriate, shall apply to this test method. 3.2 Apparatus 3.2.1 Laboratory vane apparatus, consisting essentially of the following. (A schematic arrangement is shown in Figure
31、 1.)BS1377-7:1990 2 BSI 01-1999 a) A four-bladed cruciform vane mounted on a rod, the assembly being of stainless steel or plated steel and hard soldered. Typical blade dimensions are 12.7 mm wide and 12.7 mm long, but larger vanes may be used for measuring very low shear strengths. The design shall
32、 be such that it causes as little remoulding and disturbance as possible when inserted into a soil sample. The blades shall be as thin as possible, consistent with strength requirements. The area ratio of the vane, as expressed below, shall be as low as possible and shall not exceed 15%. where b) A
33、device for applying torque to the vane, such as a hand-operated or motorized worm and pinion drive with a suitable scale graduated in 1 intervals to indicate torque and fitted with a maximum reading indicator. c) At least four calibrated open-coil torsion springs of different stiffnesses, capable of
34、 measuring applied torque up to 350 Nmm. Each spring shall be calibrated at least once per year to an accuracy of within 2% of its indicated torque within its working range. d) A scale graduated in 1 intervals for measuring the angular rotation of the vane relative to the soil in which it is placed.
35、 e) A means of lowering the vane vertically into the soil sample in a continuous smooth movement to the desired depth, such as a hand-operated lead-screw mounted on a rigid frame. f) A baseplate attached to the frame on which the soil sample in its container can be mounted. NOTEThe arrangement shoul
36、d allow for mounting a 100 mm diameter sampling tube, to enable a test to be carried out on the soil in the tube. 3.2.2 Calibration curve for each torsion spring. 3.2.3 Means of attaching the sample container or tube to the base of the vane instrument. 3.2.4 Soil trimming tools. 3.2.5 Steel rule, re
37、adable to 0.5 mm. 3.2.6 Equipment for the determination of moisture content, as given in 3.2 of BS 1377-2:1990. 3.2.7 Stopclock, readable to 1 s. 3.3 Procedure 3.3.1 Attach the sample container securely to the base of the vane apparatus, with the sample axis vertical and located centrally under the
38、axis of the vane. 3.3.2 Trim the upper surface of the sample flat and perpendicular to the axis. 3.3.3 Select a torsion spring that is most appropriate for the estimated strength of the soil and assemble it into the vane apparatus. 3.3.4 Set the pointer and the graduated scale on the torsion head to
39、 their zero readings, and ensure that there is no backlash in the mechanism for applying torque. 3.3.5 Lower the vane assembly until the end of the vane just touches the surface of the sample. This provides the datum from which the depth of penetration of the vane can be measured. 3.3.6 Lower the va
40、ne assembly further to push the vane steadily into the sample to the required depth. The top of the vane should be at a distance not less than four times the blade width below the surface. Record the depth of penetration. 3.3.7 Apply torque to the vane by rotating the torsion head at a rate of 6/min
41、 to 12/min, until the soil has sheared. NOTEThis is indicated by a decrease in torque and an uncontrolled rotation of the vane. 3.3.8 Record the maximum angular deflection of the torsion spring and the angle of rotation of the vane at the instant of failure. 3.3.9 Rotate the vane rapidly through two
42、 revolutions so as to remould the soil in the sheared zone. 3.3.10 Immediately set the scales to zero as in 3.3.4, and repeat 3.3.7 and 3.3.8 for the soil in the remoulded condition. 3.3.11 Raise the vane steadily. As it emerges from the sample prevent excessive disturbance due to tearing of the sur
43、face. Wipe the blades clean. 3.3.12 Repeat 3.3.4 to 3.3.11 with the vane positioned at two or more additional locations at the same level in the sample. NOTE 1In a 100 mm diameter sampling tube, four additional tests equally spaced at a radius of 30 mm from the centre can be performed using a 12.7 m
44、m vane. NOTE 2The centre to centre distance between the points of measurement should be not less than 2.3 times the blade width. 3.3.13 Extrude the sample from its container and take specimens from the level at which the tests were carried out for determining the soil moisture content, using the pro
45、cedure given in 3.2 of BS 1377-2:1990. 3.3.14 Record a visual description of the soil at the same level. D is the overall blade width measured to 0.1mm (in mm); T is the thickness of the blades measured to0.01mm (in mm); d is the diameter of the vane rod, including anyenlargement due to soldering me
46、asured to0.1mm (in mm);Area ratio 8TDd ();d 2 + ;D 2 -100 =BS1377-7:1990 BSI 01-1999 3 3.4 Calculations 3.4.1 For each determination calculate the torque applied to shear the soil, M(in Nmm), by multiplying the maximum angular rotation of the torsion spring (in degrees) by the calibration factor (in
47、 Nmm per degree). 3.4.2 Calculate the vane shear strength of the soil, t vin kPa) from the equation: where NOTE 1The value of K (in mm 3 ) is given by the following equation, which assumes that the distribution of shear stress is uniform around the perimeter and across the ends of the cylinder of so
48、il at failure. where The value of K for the vane 12.7 mm wide and12.7mm long referred to in 3.2.1 a) is4290mm 3 . NOTE 2The vane dimensions should be checked periodically to ensure that the vane is not distorted or worn. 3.4.3 Calculate the average value of the vane shear strength of the undisturbed
49、 soil, t v(in kPa). 3.4.4 Calculate the average value of the vane shear strength of the remoulded soil, t vr(in kPa). 3.4.5 Calculate the moisture content of the soil at the test horizon. 3.5 Test report The test report shall state that the test was carried out in accordance with clause 3 of BS 1377-7:1990. It shall contain the following, in addition to the information listed in clause 9 of BS 1377-1:1990. a) statement of the method used, i.e.determination of shear strength by the
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