导致直接剪切实验强度偏高的原因及改进办法
Reason for Resulting in High Direct Shearing Strength and Improvement of Loading Uni
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摘要: 对次生红粘土、粉质粘土和全风化泥岩进行了直接快剪实验和三轴不排水剪切实验,并对实验结果进行 了分析.实验结果显示,直接快剪实验获得的岩土体的抗剪强度指标———粘聚力和内摩擦角明显高于三轴实验 结果.分析其原因,在于直剪实验中法向力与剪切力(剪切面)不垂直,使试样的应力状态改变,从而导致直剪实 验获得的岩土体抗剪强度指标偏高.最后,根据力的平衡原理,提出了直剪仪加载装置的改进办法———改一端加 载为两端加载.Abstract: Direct and triaxial shearing tests were carried out for deuterogenic adamic earth, silty clay and completelyweathered mudstone, and the experimental results were analyzed. The result shows that shear strength of rock or soil, cohesive force and internal friction angle, obtained through a direct shearing test is markedly higher than that through a triaxial shearing test. The reason for this phenomenon is that normal force in directshearingtests is notusuallyvertical tothe shearforce (shearsurface) to lead tothe change in stress state in samples, as a result, higher shearing strength than triaxial shearing strength is obtained. Finally, an improved measure for the loading unitwas proposed based on the principle of force equilibrium, i.e.loading at its two ends instead of one end.
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Key words:
- direct shear test /
- normal force /
- direct shear apparatus /
- improvement of loading unit
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