无胶结粗粒土初始结构强度研究

无论是原状土还是重塑土均存在初始结构性，土体初始结构所抵抗的剪应力为土体结构强度。为了研究无胶结粗粒土初始结构强度，定义了粗粒土剪切过程中初始结构变化点特征，并根据大于20 mm粗颗粒含量将粗粒土划分为4种结构类型，采用可视化直剪仪对不同结构特征的粗粒土进行直剪试验，通过剪切过程中粗粒土平面孔隙比、配位数、概率熵等3种初始结构指标的数值大小及变化趋势，来确定不同初始结构的粗粒土结构临界强度。结果表明:不同初始结构类型粗粒土在相同正应力、相同颗粒种类的情况下，其抗剪强度大小与结构强度占比大小的排序一致，表明了颗粒结构强度在抵抗剪应力的整个过程中起到了重要作用。4种初始结构类型粗粒土平均结构强度占比为36.27%，即结构强度占峰值抗剪强度的36.27%，其中排列接触结构的结构强度占比最高，为36.62%，其次为镶嵌结构36.61%，悬浮密实结构35.99%，叠置结构的结构强度占比最低，为35.87%。

Research on the critical strength of the initial structure of the uncemented coarse-grained soil

Both the undisturbed soil and remolded soil have initial structural properties, and the shear stress resisted by the initial structure of the soil is the structural strength of the soil. In order to study the initial structural strength of the uncemented coarse-grained soil, this paper defines the characteristics of the initial structural change points of the coarse-grained soil during the shearing process, and divides the coarse-grained soil into four structural types according to the content of the coarse-grained soils greater than 20 mm. Visual direct shear instrument direct shear tests are carried out on the coarse-grained soils with different structural characteristics, and the critical strength of the coarse-grained soils with different initial structures is determined through the numerical value and the change trend of the initial structure indexes of the coarse-grained soils during the shearing process. The results show that the shear strength of the coarse-grained soils with different initial structure types under the same normal stress and the same particle type are in the same order as the proportion of the structural strength, indicating that the particle structure strength plays a role in the whole process of the resisting shear stress. The average structural strength of the four initial structure types of the coarse-grained soils accountes for 36.27%, that is, the structural strength accountes for 36.27% of the peak shear strength. The arranged contact structure has the highest structural strength at 36.62%, followed by the mosaic structure 36.61%. The suspended dense structure is 35.99%, and the superimposed structure has the lowest proportion of the structural strength, which is 35.87%.