the soil mechanics report for direct shear test

土力学直接剪力实验

Year 2 Soil Mechanics Direct Shear Test

Li Cheng 200838895

Introduction

Shear strength is one of the most important mechanical properties of soil, and it always causes the effect to actual engineering factors, such as lateral earth pressure to retaining wall and stability of slops. It is known that one of the most typical and effective methods is the direct shear test of soil, and it can apply the visual behavior of the shear strength of the sample. This report will describe a direct shear test and explore shear strength of Erith sand.

Theory

It has been known that shear strength of soil is directly proportional to normal stress on the shear surface. The innate character of Shear strength of soil is sliding friction between soil particles and cohesion of soil particles, and the value of shear strength depends on roughness of the surface of soil particle, size of soil particle and compactness of the sample.

Apparatus

In this test, the most equipment is the automatic shear device and the shear box. Apart from this, some assistant equipment, such as 10kg and 20kg loads, dial gauges and an electronic weighing. In addition, the test sample is Erith sand.

Procedure

All experimenters were divided into 2 groups, and the loose specimen and the dense specimen were operated by these 2 groups respectively.

For the loose specimen test, the sample (Erith sand) was filled into the shear box to approximately 10mm from the top, and a little thin steel plate was used to provide a level surface carefully, then the surplus sand was strike off. Besides this, the top plate should be added on the shear box carefully and it must be sure that the sample cannot be compressed at all in order to reduce the error as much as possible.

For the dense specimen test, the shear box also must be filled with Erith sand, but it was placed in 3 layers and each layer was tamped thoroughly with the block. It is necessary to keep each

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