BS 1377-6-1990 Methods of test for soils for civil engineering purposes - Consolidation and permeability tests in hydraulic cells and with pore pressure measurement《土木工程用土壤试验方法 第6部.pdf

1、BRITISH STANDARD BS 1377-6: 1990 Incorporating Amendement No. 1 Methods of test for Soils for civil engineering purposes Part 6: Consolidation and permeability tests in hydraulic cells and with pore pressure measurementBS1377-6:1990 This British Standard, having been prepared under the direction of

2、the Road Engineering Standards Policy Committee, was published under the authority of Board of the BSI and comes intoeffect on 30 November 1990 BSI 01-1999 The following BSI references relate to the work on this standard: Committee reference RDB/38 Draft for comment 89/11040 DC ISBN 0 580 18588 5 Co

3、mmittees responsible for this British Standard The preparation of this British Standard was entrusted by the Road Engineering Standards Policy Committee (RDB/-) to Technical Committee RDB/38, upon which the following bodies were represented: Association of Consulting Engineers British Civil Engineer

4、ing Test Equipment Manufacturers Association County Surveyors Society Department of the Environment (Property Services Agency) Department of the Environment (Building Research Establishment) Department of Transport Department of Transport (Transport and Road Research Laboratory) Coopted members Amen

5、dments issued since publication Amd. No. Date Comments 8261 November1994 Indicated by a sideline in the marginBS1377-6:1990 BSI 01-1999 i Contents Page Committees responsible Inside front cover Foreword ii 1 Scope 1 2 Definitions 1 3 Determination of consolidation properties using a hydraulic cell 2

6、 3.1 General 2 3.2 Apparatus 2 3.3 Preparation of specimens 9 3.4 Cell assembly 13 3.5 Procedure for consolidation test with one-way vertical drainage 15 3.6 Procedure for consolidation test with two-way vertical drainage 23 3.7 Procedure for consolidation test with drainage radially outwards 25 3.8

7、 Procedure for consolidation test with drainage radially inwards 27 4 Determination of permeability in a hydraulic consolidation cell 28 4.1 General 28 4.2 Apparatus for preparation of specimens 29 4.3 Apparatus for permeability test 29 4.4 Calibration of apparatus 29 4.5 Preparation and checking of

8、 apparatus 30 4.6 Preparation of test specimen 30 4.7 Assembly of cell 30 4.8 Test procedures 30 4.9 Calculations 31 4.10 Reporting results 32 5 Determination of isotropic consolidation properties using a triaxial cell 32 5.1 General 32 5.2 Apparatus 33 5.3 Preparation and setting up of specimen 37

9、5.4 Saturation 38 5.5 Procedure for triaxial consolidation with vertical drainage 40 5.6 Calculations, plotting and analysis 41 5.7 Test report 42 6 Determination of permeability in a triaxial cell 43 6.1 General 43 6.2 Apparatus for preparation of specimens 43 6.3 Apparatus for permeability test 43

10、 6.4 Preparation and checking of apparatus 45 6.5 Preparation and setting up of specimen 45 6.6 Saturation 45 6.7 Consolidation 45 6.8 Procedure for measurement of permeability 45 6.9 Calculations 46 6.10 Reporting results 46 Appendix A Typical test data and calculation forms 48 Figure 1 Drainage an

11、d loading conditions for consolidation tests in hydraulic cells 3 Figure 2 Arrangement of hydraulic cell for vertical drainage consolidationtesttype (a) 4BS1377-6:1990 ii BSI 01-1999 Page Figure 3 Arrangement for load calibration of diaphragm 11 Figure 4 Connections to hydraulic consolidation cell f

12、or consolidationtestwithradial drainage to periphery test type (f) 16 Figure 5 Derivation of t 50from log time curves 21 Figure 6 Derivation of t 50and t 90from power function curves 23 Figure 7 Temperature correction curve 24 Figure 8 Arrangement of cell and equipment for triaxial consolidation tes

13、t 35 Figure 9 Derivation of t 50from plot of pore pressure dissipation againstlogtime 44 Figure 10 Arrangement of cell and equipment for triaxial permeability test 47 Publication referred to Inside back coverBS1377-6:1990 BSI 01-1999 iii Foreword This Part of BS 1377 has been prepared under the dire

14、ction of the Road Engineering Standards Policy Committee. It is a part revision of clause 5 of BS1377:1975 which is superseded by amendment. BS1377:1975 which has now been withdrawn is replaced by the following Parts of BS1377:1990: Part 1: General requirements and sample preparation; Part 2: Classi

15、fication tests; Part 3: Chemical and electro-chemical tests; Part 4: Compaction-related 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);

16、Part 8: Shear strength tests (effective stress); Part 9: In-situ tests. Reference 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 ex

17、perienced personnel. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages Thi

18、s document comprises a front cover, an inside front cover, pages i to iv, pages1to 64, an 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 blankB

19、S1377-6:1990 BSI 01-1999 1 1 Scope This Part of BS 1377 specifies methods of test for determination of consolidation and permeability characteristics of saturated soils using apparatus which is more complex than that used for the tests described in Part 5. Two types of equipment are used: a) hydraul

20、ically loaded one-dimensional consolidation cell; b) a triaxial consolidation cell. The most significant capabilities of both types of apparatus are: 1) measurement of pore water pressure; 2) control of drainage; 3) application of back pressure to the specimen. Consolidation or triaxial cells of lar

21、ge diameter enable large specimens to be tested so that some account can be taken of the effects of the soil fabric. These procedures appear for the first time in this standard. Reference should be made to BS 1377-1 for general requirements that are relevant to all Parts of this standard, and for me

22、thods of preparation of soil and specimens for testing. 2 Definitions For the purposes of this Part of BS 1377 the definitions given in BS1377-1 apply, together with the following. 2.1 diaphragm pressure of a hydraulic consolidation cell the pressure applied to the fluid above the flexible loading d

23、iaphragm 2.2 applied total stress the mean pressure actually transmitted to the surface of the specimen 2.3 free strain loading application of a uniformly distributed pressure to the surface of the specimen from the flexible diaphragm 2.4 equal strain loading application of pressure to the surface o

24、f the specimen through a rigid disc so that the surface always remains plane 2.5 pore pressure ratio the ratio of the incremental change in pore pressure to the applied increment of vertical stress when drainage is not allowed 2.6 cell pressure (s 3 ) the pressure of the cell fluid which applies iso

25、tropic stress to the specimen in a triaxial cell 2.7 back pressure (u b ) pressure applied directly to the pore fluid in the specimen voids 2.8 effective cell pressure the difference between the cell pressure and pore water pressure 2.9 effective consolidation pressure (s9 3 ) the difference between

26、 the cell pressure and the back pressure against which the pore fluid drains during the consolidation stage, calculated as: s9 3= s 3 u b 2.10 pore pressure coefficients A and B changes in total stresses applied to a specimen when no drainage is permitted produces changes in the pore pressure in acc

27、ordance with the equation Du = BDs 3 + A(Ds 1 Ds 3 ) where NOTEIn a saturated soil (except very stiff soils) the value of B is theoretically equal to 1. Du is the change in pore pressure; Ds 1 is the change in total major principal stress; Ds 3 is the change in total minor principal stress; (Ds 1 Ds

28、 3 ) is the change in deviator stress; A and B are the pore pressure coefficients.BS1377-6:1990 2 BSI 01-1999 3 Determination of consolidation properties using a hydraulic cell 3.1 General 3.1.1 Introduction. These procedures cover the determination of the magnitudes and rates of consolidation of so

29、il specimens of relatively low permeability using hydraulically loaded apparatus. They provide a convenient means of testing large specimens, and enable drainage in either the horizontal or vertical directions to be investigated. The specimen is in the form of a cylinder confined laterally, subjecte

30、d to vertical axial pressure applied hydraulically. The apparatus and procedures described here are based on the extendable-bellows type of hydraulic cell. Specimen diameters typically range from75mm to 254mm. Other types of hydraulically loaded cell, incorporating for instance a rolling-seal diaphr

31、agm, are also available. The test method is not restricted to a particular design of cell provided that the essential requirements are fulfilled. 3.1.2 Types of test. In this type of cell, pressure may be applied to the surface of the specimen either directly from the flexible diaphragm (giving a un

32、iform stress distribution, the “free strain” condition), or through a rigid loading plate which ensures that the top surface remains plane (the “equal strain” condition). With either type of loading the following drainage conditions are possible. The various configurations are indicated diagrammatic

33、ally in Figure 1, as follows: a) vertical drainage to the top surface only, with measurement of pore pressure at the centre of the base Figure 1(a) and Figure 1(b); b) vertical drainage to both top and bottom surfaces Figure 1(c) and Figure 1(d); c) radial drainage outwards to the periphery only, wi

34、th measurement of pore pressure at the centre of the base Figure 1(e) and Figure 1(f); d) radial drainage inwards to a central drain with measurement of pore pressure at one or more points off centre Figure 1(g) and Figure 1(h). Each method requires its own curve-fitting procedure and multiplying fa

35、ctors for deriving the relevant coefficient of consolidation. The factors also depend on whether data are derived from pore pressure measurements at a single point, or from “average” measurements (volume change orsettlement) for the specimen as a whole. 3.1.3 Test conditions. The following test cond

36、itions shall be specified before starting a test: a) size of test specimen; b) drainage conditions; c) loading conditions; d) location of pore pressure measurement point (when required); e) whether void ratios are to be calculated and plotted; f) sequence of effective pressure increments and decreme

37、nts; g) criterion for terminating each primary consolidation and swelling stage; h) whether secondary compression characteristics are required. The requirements of Part 1 of this standard, where appropriate, shall apply to the test methods described in this clause. 3.1.4 Environmental requirements a

38、nd safety 3.1.4.1 Temperature. These tests shall be carried out in a laboratory in which the temperature is maintained constant to within 2 C, in accordance with 6.1 of BS 1377-1:1990. All apparatus shall be protected from direct sunlight, from local sources of heat and from draughts. 3.1.4.2 Hazard

39、 warning NOTEUsers of this equipment should be conversant with regulations for pressure vessels. Consolidation cells and ancillary equipment shall not be used at pressures above their safe working pressures. 3.2 Apparatus 3.2.1 Hydraulic consolidation cell and accessories 3.2.1.1 General requirement

40、s for the cell 3.2.1.1.1 All metal body components shall be impervious and corrosion resistant. The cell body, top and base shall all be of the same material to minimize the possible effects of electrolytic corrosion. 3.2.1.1.2 The cell when assembled shall be capable of withstanding sustained inter

41、nal water pressures of up to1000kPa without significant leakage or distortion. NOTEThe main features of the extending-bellows type of a250mm diameter cell are shown diagramatically in Figure 2. 3.2.1.2 Components of the cell 3.2.1.2.1 Cell body, the inside face of which shall be smooth and free from

42、 pitting. NOTEThe internal surface of the body and base may be lined with a thin smooth impervious layer of plastics material bonded on, to reduce wall and base friction and inhibit corrosion.BS1377-6:1990 BSI 01-1999 3 Figure 1 Drainage and loading conditions for consolidation tests in hydraulic ce

43、llsBS 1377-6:1990 4 BSI 01-1999 Figure 2 Arrangement of hydraulic cell for vertical drainage consolidation test type (a)BS1377-6:1990 BSI 01-1999 5 3.2.1.2.2 Top cover, fitted with an air bleed plug and a bushing or seal for a hollow rod (the drainage stem) which is attached to an impermeable flexib

44、le diaphragm, e.g. of butyl rubber. Since the drainage stem permits drainage to take place from the top face of the specimen, provision shall be made for measurement of the vertical movement of that face. 3.2.1.2.3 The diaphragm, selected from a range of diaphragms of various stiffnesses so that it

45、is appropriate to the soil type and the type of test. NOTEIn cells using a bellows type of diaphragm the folds pressing against the cell wall can impede the removal of excess water for some considerable time. It is advantageous to fit a strip or collar of porous plastics material between the diaphra

46、gm and the rim drainage aperture to provide a free drainage path which enables this water to be removed quickly. 3.2.1.2.4 Cell base, incorporating a central recess for a porous insert (the pore pressure measurement point) connected to a valve on the periphery. NOTEPore pressure is usually measured

47、at the centre of the base of the specimen in tests with vertical drainage. Some cell bases of large diameter are fitted with additional off-centre pore pressure points, one (or more) of which is used for some tests in which radial drainage takes place. 3.2.1.2.5 Connection ports incorporated into th

48、e top cover and cell base as shown in Figure 2. Each port shall be fitted with either a valve, or a blanking plug if it is not required for the test. The ports shall be connected as follows (the corresponding valve designations are indicated in brackets): a) from the pore pressure measurement point

49、in the cell base to the pore pressure measuring device (the pore pressure valve); b) from the pore pressure measuring device mounting block to the flushing system (the flushing system valve); c) from the diaphragm pressurizing chamber to the diaphragm pressure system (the diaphragm pressure valve); d) from the top of the specimen via the drainage stem to the back pressure system (the back pressure valve); e) from the rim drain (when required) to the back pressure system (the rim drain valve). 3.2.1.2.6 Porous