| ABSTRACT:Because of the specific engineering characteristics of coarse soils, so it is widely used in traffic engineering. Especially in the construction of the Qinghai-Tibet Railway, coarse granular materials can reduce the holding water capacity of soils, and then mitigate the effects of freezing effect on the line. Because the large size is the main feature of coarse-grained soils, particles can be crushed under loads and weathering. Crushing will change the strength and it is dangerous to engineering. Based on these factors, the paper carries on experiments on coarse-grained soils to study the shear strength characteristics of coarse grained soils, the granular crushing characteristics and the relationship between them.Despite there are some shortcomings about direct shear test, it is widely used in civil engineering. Because the direct shear test has some special advantages, such as simple operation, especially experimental data can meet the engineering requirements. The paper uses the large-scale direct shear test apparatus to study the shear strength characteristics of coarse-grained soils and the screen test to study the granular crushing characteristics.The paper selects three different sizes samples to carry on strength test and screen test to get the most basic conclusion on strength and crushing. Subsequently, do test on the influence factors about granular crushing. Lastly, draw following conclusions:(1) Under the constant normal stress, the shear strength and the crushing degree increase as the granular size increases.(2)As to the same size samples, the shear strength and the crushing degree increase as normal stress increases.(3) As to poor gradation samples, granular crushing leads to better gradation curve as cutting. At the same time, particles mainly form ones of the secondary sizes because of granular crushing. |
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