CN101377079A - Method for measuring foundation bed coefficient indoor - Google Patents

Method for measuring foundation bed coefficient indoor Download PDF

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Publication number
CN101377079A
CN101377079A CNA2008102008977A CN200810200897A CN101377079A CN 101377079 A CN101377079 A CN 101377079A CN A2008102008977 A CNA2008102008977 A CN A2008102008977A CN 200810200897 A CN200810200897 A CN 200810200897A CN 101377079 A CN101377079 A CN 101377079A
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soil
test
sample
coefficient
triaxial
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吴英
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SHANGHAI MUNICIPAL ENGINEERING SURVEY AND DESIGN Co Ltd
Shanghai Municipal Engineering Design Insitute Group Co Ltd
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SHANGHAI MUNICIPAL ENGINEERING SURVEY AND DESIGN Co Ltd
Shanghai Municipal Engineering Design Insitute Group Co Ltd
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Priority to CNA2008102008977A priority Critical patent/CN101377079A/en
Publication of CN101377079A publication Critical patent/CN101377079A/en
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Abstract

The present invention discloses a method for interiorly determining a coefficient of subgrade reaction. The method includes the following steps: (a) soil is first sampled along or vertical to the depositing direction of a soil layer; (b) after being measured by a triaxial instrument, the soil sample is saturated; (c) then, the saturated soil sample is consolidated under a certain confining pressure; (d) after the consolidation is stabilized, a triaxial consolidated drained shear test is conduced along a stress path; (e) data are obtained from the triaxial consolidated drained shear test; (f) a test curve is educed by compiling the test data; (g) according to soil features, a coefficient of subgrade reaction is chosen through the test curve. The method can simulate the natural stressed state of soil in order to ensure that a test can be more reasonable and a test result can be close to an on-spot test result. Consequently, the coefficient of subgrade reaction, which is determined by the method, is highly reliable and accurate.

Description

A kind of method of measuring foundation bed coefficient indoor
Technical field:
The present invention relates to the geotechnical engineering field tests, the method for indoor three (CD) determination of test method coefficient of subgrade reaction of specifically a kind of employing.
Background technology:
Usually foundation soil can produce displacement (vertical and level) under the effect of external force, and promptly foundation soil and works interact, and mainly makes the basis of works or lining cutting produce vertical and lateral deflection, and engineering safety is caused very big harm.At underground base pit engineering, airport and building foundation engineering, in subway engineering, coefficient of subgrade reaction is an important indicator calculating the foundation soil displacement especially.Therefore adopt any method how accurately to measure Foundation Soil Coefficient of Subgrade Reaction and just seem extremely important.On-the-spot at present main static load nuclear test and two kinds of methods of flat chisel test of adopting are measured, indoor common employing consolidometer and two kinds of methods of stress-type triaxial apparatus, on-the-spot load test, flat chisel test, indoor consolidation test, no matter but which kind of method, owing to be subjected to influence of various factors, the condition of its test can not be consistent with the natural stress state of reality, and the value of result of the test lacks strict definition, and the result of test differs too big with on-the-spot and empirical data.
Summary of the invention:
The rational method that the purpose of this invention is to provide a kind of measuring foundation bed coefficient indoor can not be subjected to outdoor influence of various factors, thereby makes the result of test and engineering reality more approaching, can provide data more accurately for the designer.
Technical scheme of the present invention is achieved in that a kind of method of measuring foundation bed coefficient indoor, it is characterized in that: described method may further comprise the steps: a, at first soil sample along soil layer deposition direction or vertical soil layer deposition direction fetch earth sample preparation b, measure at indoor employing triaxial apparatus, soil sample is carried out saturated processing; C is then with fixed under certain confined pressure with this sample after the saturated processing of soil sample; D, treat stabilization by consolidation after, do the triaxial consolidation Drainage Shear test under the stress path; E, draw triaxial consolidation Drainage Shear test for data; F, by the arrangement experimental data obtain trial curve; G, by trial curve, choose coefficient of subgrade reaction according to soil nature.
Unique distinction of the present invention is; Owing to make sample adopt Ko state (each is to the differential stress state) fixed down before the test, make under soil sample stress and the native state similar.Overcome the deficiency that its test conditions of other test method can not be consistent with the natural stress state of reality; Utilize the feature of strain-type triaxial apparatus, by control Δ σ 3Constant, satisfy Δ σ 3/ Δ σ 1=0 one kind of test conditions.And triaxial test has overcome above defective, can simulate the natural stressed state of soil, makes test more reasonable, and result of the test and field experiment result are very approaching.So the coefficient of subgrade reaction that adopts this method to measure has very high reliability and accuracy.
The specific embodiment:
Below the present invention is done comparatively detailed description.
The stress of sample is to measure the key technology of coefficient of subgrade reaction among the present invention, in order to make test more close with native state, technical solution of the present invention is: a kind of method of measuring foundation bed coefficient indoor, it is characterized in that: described method may further comprise the steps: a, at first soil sample along soil layer deposition direction or the vertical soil layer deposition direction sample that fetches earth, this sample is undertaken by " Code for investigation of geotechnical engineering " GB50021-2001 requirement, the test soil sample should reach the one-level soil sample, therefore require field operation to fetch earth, guarantee sample quality with thin-wall sampler or 108; B, measure at indoor employing triaxial apparatus, soil sample is carried out saturated processing, the saturated processing of sample is undertaken by triaxial test method requirement among " Standard for test methods of earthworks " GB/T50123-1999; C, then that the sample after the saturated processing of soil sample is fixed under 50-250kpa confined pressure carries out under the KO state fixedly according to the character of soil and the degree of depth when specifically handling, the general value of KO is 0.3-0.6; D, treat stabilization by consolidation after, be triaxial consolidation Drainage Shear test (the Δ σ under the stress path 3/ Δ σ 1=0,1,2,3 ...), adopt Δ σ when specifically handling 3/ Δ σ 1A kind of test conditions of=0; E, draw triaxial consolidation Drainage Shear test for data; F, by the arrangement experimental data obtain trial curve; G, by trial curve, choose coefficient of subgrade reaction according to soil nature.
During concrete enforcement at first, according to the National Standard Code for investigation of geotechnical engineering " the GB50021-2001 requirement, the quality of soil sample of doing triaxial test will reach the one-level soil sample, simultaneously in order to satisfy the size of sample preparation, the sample minimum diameter of this test employing
Figure A200810200897D00061
Maximum gauge is
Figure A200810200897D00062
The height of sample is preferably 2-2.5 times of diameter, so require the field operation probing to use
Figure A200810200897D00063
Soil sampler fetches earth; Then, the undisturbed soil sample that field operation is fetched is made along soil layer deposition direction or vertical soil layer deposition direction
Figure A200810200897D00064
The cylindrical sample of height 80mm; Again the sample that makes is carried out saturated processing, we adopt head saturated usually, and saturation ratio requires to reach more than 95%; The sample of saturation is installed on the instrument, and it is fixed to select 50-250kpa confined pressure to carry out according to soil nature, similar under soil sample stress and the native state when making test, adopts Ko state (each is to the differential stress state) to descend fixed usually.Promptly determine the soil sample selfweight stress according to ground soil nature matter and buried depth, axial stress is taken from heavy stress intensity σ when fixed 1=γ h, side direction confined pressure σ 3The natural stressed σ that is taken as according to soil 3=Ko σ 1, can make soil sample return to natural stressed state like this.Wherein: σ 1---Axial stress, general span are 100-800kpa, γ--the density of-soil, h-soil sample buried depth height, K 0---The upright coefficient of the static pressure measurement of soil, general span is 0.3-0.6, σ 3-The side direction confined pressure power of soil, general span is 50-250kpa.After treating the soil sample stabilization by consolidation, open draining valve and begin test, do the triaxial consolidation Drainage Shear test under the different stress paths, i.e. Δ σ 3/ Δ σ 1=0,1,2,3 ... because the used instrument of our triaxial test mostly is the strain-type triaxial apparatus at present, can not control axial stress σ 1, σ in process of the test 1Be a variable, so we can only be Δ σ by controlling confined pressure constant 3=0, satisfy Δ σ 3/ Δ σ 1=0 one kind of test conditions.After the off-test, by the arrangement test image data E-Δ ε test relation curve that draws, this test relation curve concerns for coordinate in length and breadth, wherein E represents coefficient of subgrade reaction, Δ ε represents strain capacity, choose rational coefficient of subgrade reaction according to soil nature then, be the coefficient of subgrade reaction under the corresponding stress state of this soil soil sample.

Claims (5)

1, a kind of method of measuring foundation bed coefficient indoor is characterized in that: described method may further comprise the steps: a, at first soil sample along soil layer deposition direction or the vertical soil layer deposition direction sample that fetches earth; B, measure, soil sample is carried out saturated processing at indoor employing triaxial apparatus; C is fixed under 50-250kpa with the sample after the saturated processing of soil sample in confined pressure then; D, treat stabilization by consolidation after, do the triaxial consolidation Drainage Shear test under the stress path; E, draw triaxial consolidation Drainage Shear test for data; F, by the arrangement experimental data obtain trial curve; G, by trial curve, choose rational coefficient of subgrade reaction according to soil nature.
2, the method for a kind of measuring foundation bed coefficient indoor according to claim 1 is characterized in that: outdoor will using 108 soil samplers fetch earth, the diameter 39.1mm of soil sample, height 80mm.
3, the method for a kind of measuring foundation bed coefficient indoor according to claim 1 is characterized in that: get axial stress σ 1=γ h, the side direction confined pressure is σ 3=K 0σ 1, make sample then at K 0Fixed under the state; σ wherein 1---Axial stress, γ--the density of-soil, h-soil sample buried depth height, K 0---The upright coefficient of the static pressure measurement of soil, σ 3-The lateral pressure of soil.
4, according to the method for claim 1 or 3 described a kind of measuring foundation bed coefficient indoors, it is characterized in that: described triaxial apparatus is the strain-type triaxial apparatus, according to the performance of strain-type triaxial apparatus, by control Δ σ 3Constant, satisfy Δ σ 3/ Δ σ 1=0 one kind of test conditions; Determine side direction confined pressure σ 3=Koσ 1The time, K 0Value is 0.3-0.6.
5, according to the method for claim 1 or 3 described a kind of measuring foundation bed coefficient indoors, it is characterized in that: shear rate is abideed by " Standard for test methods of earthworks " GB/T50123-1999 triaxial consolidation Drainage Shear test shear rate per minute strain 0.003%-0.012%.
CNA2008102008977A 2008-10-08 2008-10-08 Method for measuring foundation bed coefficient indoor Pending CN101377079A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011022932A1 (en) * 2009-08-26 2011-03-03 中冶集团武汉勘查研究院有限公司 Testing method and device for foundation bed coefficient test
CN102776875A (en) * 2012-08-19 2012-11-14 张望喜 Method for field measurement for foundation bed coefficient of double-parameter foundation by virtue of static load test for rigid plates
CN103344747A (en) * 2013-07-03 2013-10-09 兰州大学 Technical method for shortening saturation time of silty clay
CN103669317A (en) * 2012-09-11 2014-03-26 张望喜 Method for measuring dynamic subgrade reaction coefficient of two-parameter foundation through rigid plate dynamic test
CN104089817A (en) * 2014-04-01 2014-10-08 中冶集团武汉勘察研究院有限公司 Reference bedding coefficient tester and indoor general testing method thereof
CN104594323A (en) * 2015-02-11 2015-05-06 浙江省工程勘察院 Test device for coefficients of horizontal-reference foundation bed and test method using device

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011022932A1 (en) * 2009-08-26 2011-03-03 中冶集团武汉勘查研究院有限公司 Testing method and device for foundation bed coefficient test
GB2488053A (en) * 2009-08-26 2012-08-15 Wuhan Surveying Geotechnical Res Inst Co Ltd Of Mcc Testing method and device for coefficient of subgrade reaction test
GB2488053B (en) * 2009-08-26 2013-07-31 Wuhan Surveying Geotechnical Res Inst Co Ltd Of Mcc Testing device for coefficient of subgrade reaction test
CN102776875A (en) * 2012-08-19 2012-11-14 张望喜 Method for field measurement for foundation bed coefficient of double-parameter foundation by virtue of static load test for rigid plates
CN103669317A (en) * 2012-09-11 2014-03-26 张望喜 Method for measuring dynamic subgrade reaction coefficient of two-parameter foundation through rigid plate dynamic test
CN103669317B (en) * 2012-09-11 2015-07-08 张望喜 Method for measuring dynamic subgrade reaction coefficient of two-parameter foundation through rigid plate dynamic test
CN103344747A (en) * 2013-07-03 2013-10-09 兰州大学 Technical method for shortening saturation time of silty clay
CN103344747B (en) * 2013-07-03 2015-07-15 兰州大学 Technical method for shortening saturation time of silty clay
CN104089817A (en) * 2014-04-01 2014-10-08 中冶集团武汉勘察研究院有限公司 Reference bedding coefficient tester and indoor general testing method thereof
CN104089817B (en) * 2014-04-01 2017-03-15 中冶集团武汉勘察研究院有限公司 Benchmark bedding value tester and its indoor universal method of testing
CN104594323A (en) * 2015-02-11 2015-05-06 浙江省工程勘察院 Test device for coefficients of horizontal-reference foundation bed and test method using device

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Application publication date: 20090304