不同垂直荷载与剪切速率条件下水泥稳定风化砂直剪试验研究

以湖北宜昌三峡库区风化砂为研究对象,在风化砂中掺入不同量的水泥,然后改变剪切速率、改变上覆垂直荷载,进行室内直接剪切试验,研究了剪切速率、垂直荷载对不同掺量水泥稳定风化砂抗剪强度指标的影响。试验结果表明:剪切速率、垂直荷载对水泥稳定风化砂抗剪强度指标有明显影响。在相同的剪切速率和垂直荷载下,水泥稳定风化砂的黏聚力会随着水泥掺量的增加显著提高,但内摩擦角会先增大再减小;在相同的水泥掺量下,增大剪切速率和垂直荷载均会显著增大水泥稳定风化砂的黏聚力而减小其内摩擦角。剪切速率较大时,试样在剪切破坏过程中不仅要克服颗粒间的滑移,还要克服颗粒的旋转、滚动与换位阻力,使黏聚力增大。较大的垂直荷载会使试样产生较大的压缩固结,粒间的孔隙减少,孔隙间的水应力和垂向附加应力增大,砂颗粒间的相互作用力加强,抗剪强度提高。

Direct shear test analysis of cement-stabilized weathered sand under different vertical loads and shear rates

Taking the weathered sand situated in the Three Gorges reservoir area as the research object, mixing different amounts of cement with the weathered sand, and then changing the shear rates, changing the overlying vertical load, indoor direct shear tests have been carried out. This study has analyzed the impacts of the shear rates, the vertical load on the shear strength index of the cement-stabilized weathered sand having different cement contents. Experimental analysis results show that the shear rate and the vertical load have a significant effect upon the shear strength index of the cement-stabilized weathered sand. By the same action of the shear rates and the vertical load, the cohesive force of the cement-stabilized weathered sand will significantly increase with increase in the cement content, but the internal friction angle will first become great and then small; when the cement content is the same, increasing the shear rates and the vertical load will significantly increase the cohesive force of the cement-stabilized weathered sand and reduce its internal friction angle. When the shear rates are large, the sample in the process of shear failure not only overcomes the slip among the particles, but also overcomes the rotation of the particles and the transposition rolling resistance to increase the cohesive force. Larger vertical load will make the specimen have greater compression consolidation, reduce intergranular porosity, increase the water stress and the vertical additional stress within pores, and finally enhance the intergranular interaction force as well as the shear strength of the weathered sand.