颗粒粒径对粗粒土抗剪强度影响的试验研究

Experimental Study on Influence of Particle Size on Shear Strength of Coarse-Grained Soil

抗剪强度是粗粒土的一种重要力学指标,西藏区域内广泛分布着粗粒土,研究粗粒土的抗剪性能有重要的学术与工程价值。为探索粗粒土颗粒粒径对抗剪强度的影响,采用DHJ50-2型叠环式剪切试验机,对尼洋河谷7种单一粒径组粗粒土进行直剪试验。通过分析试验结果,发现同样干密度情况下:粗粒土的粘聚力(咬合力)不仅受颗粒粒径的影响,还受土体密实程度的影响;随土颗粒粒径增大,土的内摩擦角增大;各粒径组粗粒土随剪切位移增加,剪应力都经历了迅速升高、峰值、下降、平稳四个阶段;高竖向荷载作用下的峰值剪应力对应的剪切位移大于低竖向荷载作用时的剪切位移。

Shear strength is an important mechanical property of coarse-grained soils that are widely distributed in Tibet. It is of great academic and engineering value to study the shear behavior of coarse-grained soils. In order to explore the influence of coarse-grained soil particle size on shear strength, direct shear tests were carried out on 7 kinds of coarse-grained soil with different particle sizes in Niyang Valley by using DHJ50-2 cascade shear testing machine. Through the analysis of shear test data for the same dry density coarse-grained soil, it is found that the cohesive force (biting force) of coarse-grained soils is not only affected by the particle size, but also by the degree of soil compaction. The internal friction angle increases with the increase of particle size. What's more, with the increase of shear displacement, the coarse-grained soil of each particle size group experiences four stages: rapid increase of shear stress, peak value, decline and stability. The shear displacement corresponding to peak shear stress under high vertical load is larger than that under low vertical load.