The determination of the shear strength of coarse-grained soils in standard shear devices is a challenging task due to the presence of large grains. Three approaches could be used to reduce the grain size of the tested specimen. This study aimed to determine whether the shear strength of a coarse-grained soil with fines (particles smaller than 0.08 mm) can be estimated by the parallel gradation approach. Direct shear tests were conducted on parallel graded specimens of two soil types with different low plastic fines content. Two criteria can be used to select the dry density of the reconstituted specimen: the same dry density or the same relative density as the initial soil. The results showed that when the specimens had a low fines content, both criteria resulted in a similar dry density of the reconstituted soil, and the shear strength of the initial soil was correctly estimated. However, for the specimens with a high fines content, the friction angle of the initial soil was correctly estimated, and its cohesion was overestimated when the reconstituted soil was tested at the same dry density as the initial soil. A cohesion-fines content relationship was proposed to predict the initial soil cohesion.

由于存在大颗粒，因此在标准剪切装置中确定粗粒土的剪切强度是一项艰巨的任务。可以使用三种方法来减小测试样品的晶粒尺寸。这项研究的目的是确定是否可以通过平行渐变方法估算出具有细粒（颗粒小于0.08 mm）的粗粒土壤的剪切强度。直接剪切试验是在两种具有不同低塑料细粉含量的土壤的平行分级标本上进行的。可以使用两个标准来选择重构样本的干密度：与初始土壤相同的干密度或相对密度。结果表明，当标本的细粉含量较低时，两个标准都导致再生土壤的干密度相似，正确估算了初始土壤的抗剪强度。但是，对于高细粉含量的试样，正确估算了初始土壤的摩擦角，而当以与初始土壤相同的干密度测试再生土壤时，其黏聚力被高估了。提出了内含物含量关系来预测初始土壤内聚力。