Method for determining shear strength of calcareous sands under high stress

A technology of shear strength and determination method, which is applied in the direction of applying stable shear force to test material strength, strength characteristics, measuring devices, etc. Shear strength and other issues, to achieve the effect of saving manpower, novel ideas, and easy operation

Active Publication Date: 2020-04-28
TIANJIN UNIV
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Problems solved by technology

[0006] However, due to the brittleness of calcareous sand particles, under the action of high vertical stress, the shear process will lead to a considerable number of particle breakage
Previous studies have shown that particle breakage can affect the shear strength of soils
However, there is currently no clear statement about this relationship

Method used

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  • Method for determining shear strength of calcareous sands under high stress
  • Method for determining shear strength of calcareous sands under high stress
  • Method for determining shear strength of calcareous sands under high stress

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Embodiment

[0056] The present invention determines the shear strength method of calcareous sand under high stress, comprises the following steps:

[0057] 1) Conduct constant stress single shear tests at 1500KPa, 3000KPa, and 5000KPa on quartz sands with different relative densities. Among them, the layered filling method is adopted for sample loading, which is divided into 3 layers, and each layer has the same height and quality;

[0058] 2) When the shear force tends to a stable value during the test, it is considered that the tested quartz sand sample has been destroyed. If the above situation does not occur, the test is stopped when the shear displacement reaches 20%;

[0059] 3) According to the shear stress-shear strain relationship curve during the test, such as figure 1 As shown, the maximum internal friction angle of the above-mentioned quartz sand under the corresponding relative compactness and constant stress is calculated by Coulomb's formula

[0060] 4) Then according t...

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Abstract

The invention discloses a method for determining the shear strength of calcareous sands under high stress. The method comprises the following steps: taking calcareous sands and quartz sands with the same grain composition, and preparing samples with different relative densities; respectively carrying out 1500KPa, 3000KPa and 000KPa constant-stress single shear tests by adopting layered filling; under the condition that the shearing force tends to a stable value, determining the soil sample to be sheared, otherwise, stopping the test when the shearing displacement reaches 20%; drawing a stress-strain relation curve, and calculating a maximum internal friction angle of the sandy soil through a coulomb formula; calculating a shear expansion angle to obtain maximum shear expansion angles of different sandy soil with different densities; calculating a critical internal friction angle; acquiring a breakage rate BrH or BrM of the sample by using a Hardin method or a Marsal method; fitting unbroken quartz sands to obtain a shear strength formula; and introducing a crushing component into a calcareous sand strength formula, calculating a crushing component according to a coefficient determined by the quartz sand, and fitting the crushing component with the crushing rate to obtain a calcareous sand shear strength formula.

Description

technical field [0001] The invention relates to a method for determining the shear strength, more specifically, a method for determining the shear strength of calcareous sand under high stress. Background technique [0002] As a special marine soil with high void ratio and fragility, calcareous sand has a certain influence on its strength. There are a large amount of calcareous sand distributed in the South my country Sea. With the exploration and exploitation of offshore oil and natural gas resources and the development of island and reef tourism in the past ten years, the number of island reefs and offshore modernization projects is increasing, and the scale will also become larger. Therefore, it is very important to study the shear strength characteristics of calcareous sand used as the foundation, and the analysis of the relationship between the shear strength and dilatancy of calcareous sand is the most important. [0003] The currently commonly used expression for the ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N3/24
CPCG01N3/24G01N2203/0003G01N2203/0025G01N2203/0284G01N2203/0682
Inventor 李飒卢川尹蒋松刘小龙陈文玮
Owner TIANJIN UNIV
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