碎石尺寸对碎石土强度影响的大型直剪试验研究

摘要

The influence of stone size on the shear strength of gravel soil was investigated through large direct shear test on three groups of remolded gravel soil specimens of different stone sizes .The gravel soil in the slope of Daqian-shiling Tunnel in the Tianshifu-Huanren railway was taken as research object .On this basis , the characteristics of grain size distribution of the gravel soil specimens were researched by using fractal theory .The fractal dimension of gravel soil with different stone sizes was obtained , and the relationship between shear strength parameters and frac-tal dimension was studied .Results indicate that when stone content is the same , shear strength and internal friction angle increase with stone size increasing;on the contrary , cohesion decreases along with the increase of stone size . With the increase of stone size , fractal dimension increases , and as fractal dimension gets bigger , the particle dis-tribution is more uneven , and vice versa.There is a certain degree of correlation between shear strength parameters and fractal dimension .With the increase of fractal dimension , cohesion decreases whereas internal friction angle in-creases;cohesion and internal friction angle have approximately parabolic function relationship with particle fractal dimension .%以田师府—桓仁铁路大前石岭隧道边坡碎石土为研究对象，配置了3组含碎石尺寸不同的重塑碎石土样并采用大型直剪仪进行了剪切试验研究，探讨了碎石尺寸对碎石土抗剪强度的影响作用规律。在此基础上，利用现代非线性理论－分形理论，采用分形几何方法研究了该碎石土重塑样的粒度分布特征，得出了不同碎石尺寸下碎石土的分形维数，并探讨了碎石土的强度特征与粒度分形维数之间的关系。研究表明：在粗粒含量相同的情况下，碎石土的抗剪强度随着碎石尺寸的相对增大而增大；内摩擦角随着碎石尺寸的相对增大而增大；而黏聚力呈现相反的趋势，随着碎石尺寸的相对增大而降低；随着碎石尺寸的相对增大，分形维数增大，分形维数越大，其颗粒粒度分布越不均匀，反之分形维数越小，其颗粒粒度分布越均匀。碎石土抗剪强度和粒度分形维数有一定的相关性，黏聚力随着分形维数的增大而减小，而内摩擦角呈现相反的趋势，随着分形维数的增大而增大，黏聚力和内摩擦角均与粒度分形维数近似呈现抛物线函数关系。