基于动力触探确定钙质粗粒料抗剪强度指标方法研究

Study on determining the strength parameters of carbonate coarse-grained soils based on dynamic cone penetration tests

钙质粗粒料广泛分布于我国南海地区,由于粗粒料很难获得良好原状试样,利用现场试验评价其力学指标对于工程建设具有重要的意义。通过对取自南海某处的钙质粗粒料进行大型直接剪切试验,得到钙质砾石和碎石的强度指标,试验结果显示,基于莫尔-库仑强度理论,钙质粗粒料具有较高的表观黏聚力和较大的内摩擦角,级配不良会导致内摩擦角的降低和表观黏聚力的提高;利用同样的土体,进行轻型动力触探室内模型试验,探讨相对密实度、平均粒径和不均匀系数对轻型动力触探贯入指标Pindex的影响;提出利用初始贯入深度表征粗粒料的表观黏聚力,尝试建立不同贯入指标和抗剪强度指标之间的关系。

Carbonate coarse-grained soils are widely distributed in South China Sea. Since it is difficult to obtain undisturbed samples of coarse-grained soils,the field tests are often used to evaluate the physical and mechanical properties of coarse-grained soils. Large-scale direct shear tests on the carbonate coarse-grained soil from South China Sea were performed,and the strength parameters of carbonate gravel were obtained. The results show that based onMohr-Coulomb failure criterion,both the internal friction angle and the apparent cohesion of the carbonate coarse-grained soil are high,and that poor grade will lead to the decrement of the internal friction angle and the increment of the apparent cohesion. Indoor light dynamic cone penetration tests on the same soil were carried out,and the influences of the relative density,the average particle size and the uniform coefficient on the penetration index(Pindex) were discussed. An index named initial penetration depth,for characterizing the apparent cohesion,was proposed to establish the relationships of the penetration index with the apparent cohesion and the internal friction angle of carbonate coarse-grained soils.