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Soft soil indoor multilevel direct shear test method

A test method and soft soil technology, applied in soil material testing, using stable shear force to test material strength, material inspection products, etc., can solve the problems of waste of soil sample resources, inability to obtain multiple sets of shear strength parameters, etc. , to achieve the effects of avoiding dispersion, saving test sample resources, and concentrating and accurate test results

Inactive Publication Date: 2009-04-08
GUANGZHOU DESIGN INST
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  • Abstract
  • Description
  • Claims
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Problems solved by technology

[0004] The purpose of the present invention is to provide an indoor multi-stage direct shear test method for soft soil in view of problems such as the inability to obtain multiple sets of shear strength parameters for the same group of soil samples in the existing direct shear test, resulting in waste of soil sample resources.

Method used

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  • Soft soil indoor multilevel direct shear test method

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specific Embodiment 1

[0021] Such as figure 1 As shown, the test device of the present invention is composed of a plurality of soft soil chambers and corresponding operating parts, and the sample is placed in the soft soil chamber for shearing test. In this specific embodiment, four silt samples are placed successively on the electric direct shear instrument, and the first-order normal load (such as 50kPa) is applied to the four silt samples simultaneously and sheared to make it reach the peak shear stress; then unload Normal load and return quickly, and then apply the second to fourth normal loads (such as 50, 100, 150 and 200kPa)) and repeat the above steps. In this way, each sample in the group of soil samples can obtain a shear strength parameter, and the group of soil samples can obtain four shear strength parameters, and the average value can be taken as the shear strength parameter of the soil sample. Specific steps are as follows:

[0022] 1) Make a set of (four) samples from a silt soil...

specific Embodiment 2

[0030] In this embodiment, the soil sample adopts soft plastic cohesive soil, the number of samples is three, and the applied normal loads are five levels in total. The specific steps are as follows:

[0031] 1) Make a set of (three) samples from a soft plastic cohesive soil sample obtained according to the specifications, and place them in the shear box of the soft soil chamber;

[0032] 2) Simultaneously apply the first level of normal load σ to the three samples 1 ; Under the first level of normal load, shear the three specimens simultaneously, and record the respective peak shear stress τ 1-1 , τ 1-2 , τ 1-3 ; Simultaneously remove all normal loads and return quickly;

[0033] 3) Simultaneously apply the second normal load σ to the three samples 2 ; Under the second level of normal load, shear the three samples simultaneously, and record the respective peak shear stress τ 2-1 , τ 2-2 , τ 2-3 ; Simultaneously remove all normal loads and return quickly;

[0034] 4), ...

specific Embodiment 3

[0040] In this embodiment, the soil sample adopts flow-plastic cohesive soil, the number of samples is five, and the applied normal loads are three levels in total. The specific steps are as follows:

[0041] 1) Make a set of (five) specimens according to the specifications of a fluid plastic cohesive soil sample that has been obtained, and place them in the shear box of the soft soil chamber;

[0042] 2) Simultaneously apply the first level normal load σ to the five samples 1 ;Under the first level of normal load, shear five specimens at the same time, and record the respective peak shear stress τ 1-1 , τ 1-2 , τ 1-3 , τ 1-4 , τ 1-5 ; Simultaneously remove all normal loads and return quickly;

[0043] 3) Simultaneously apply the second normal load σ to the five samples 2 ; Under the second normal load, shear the five specimens simultaneously, and record the respective peak shear stress τ 2-1 , τ 2-2 , τ 2-3 , τ 2-4 , τ 2-5 ; Simultaneously remove all normal loads a...

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Abstract

The invention discloses a multi-step vertical shearing testing method in a soft soil chamber, which is characterized in that 1) N samples of a same soil sample are arranged in the shearing box of the soft soil chamber; 2) first-step normal load Sigma1 is acted on the N samples simultaneously; under the normal load, a shearing force vertical to the normal load Sigma is acted on the sample; furthermore, respective shearing stress peak values, Tau<1-1>, Tau<1-2>, Tau<1-3>, ellipsis, Tau<1-N>, are respectively recorded; subsequently, all normal loads are unloaded and quickly retrieved; 3) the step 2) is repeated; the second-step normal load Sigma2, the third-step normal load Sigma3,..., the M-step normal load Sigma<M> are acted on the N samples simultaneously, thus obtaining M groups of shearing stress peak values, Tau<M-1>, Tau<M-2>, ellipsis, Tau<M-N>; 4) to the M groups of normal load Sigma<M> and the shearing stress peak values Tau<M-1>, Tau<M-2>, Tau<M-3>, and Tau<M-N> of each sample, according to a formula that Tau<M-N> is equal to c<N>+Sigma<M>tanPhi<N>, the anti-shearing strength parameters, c<N> and Phi<N> of the sample are obtained; and 5) the average value of the anti-shearing strength parameters of the N samples are used as the anti-shearing strength parameter value of the group of soil samples. The method has the effects of saving testing sample resource and has concentrative and exact testing results.

Description

technical field [0001] The invention relates to a soil sample test method, in particular to a soft soil indoor multi-stage direct shear test method. It belongs to the technical field of geological engineering. Background technique [0002] How to correctly and reasonably evaluate the mechanical parameters such as the shear strength of soft soil has always been one of the very important basic research topics in engineering geology and soil mechanics. In order to evaluate the shear strength parameters of soft soil, people are exploring and developing indoor or in-situ geotechnical test methods. In the prior art, indoor conventional test methods include direct shear test, unconfined compressive strength test and triaxial compression test. Among them, the direct shear test has a history of more than 100 years. Because the instrument used in this method is simple in structure and easy to operate, it is widely used in engineering practice in our country. [0003] The convention...

Claims

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Application Information

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IPC IPC(8): G01N33/24G01N3/24
Inventor 张晓伦何港林伟民
Owner GUANGZHOU DESIGN INST
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