不排水剪切条件下天然沉积黏土结构性演化规律

Structural evolution laws of natural sedimentary clay under undrained shear

针对不排水剪切过程中天然沉积黏土的结构特性,对原状土与重塑土进行不排水三轴试验,结合多种结构性定量分析方法和原状土宏微观分析,揭示土体在不排水剪切过程中的结构性演化规律及机制,主要结论为:结构性提高了原状土的抗剪强度,并使土体表现出应变软化特性。剪切前的固结阶段会削弱原状土的结构性。围压越大土体初始结构破损越严重,结构性影响越小。不排水剪切过程中土体结构屈服破坏,结构性对强度的影响快速下降,表现出一定的脆性性质。天然沉积黏土结构性提供的额外强度主要由胶结连接和土体骨架贡献。在土体结构屈服破坏后胶结连接和土体骨架破坏,并形成新的结构形式,改变了土体的力学性状。

To research the structural characteristics of natural sedimentary clays under undrained shear,undrained triaxial tests were conducted on undisturbed and remolded soil.Based on a variety of structural quantitative analysis methods and macro-micro analysis of undisturbed soil,the structural evolution law and mechanism of soil during undrained shear were revealed.The main conclusions show that the shear strength of undisturbed soil was structurally enhanced and the soil showed strain softening.In the undrained triaxial test,the structure of undisturbed soil will be weakened in the consolidation stage before shearing.Higher confining pressure will lead to more serious damage to the initial structure of soil but smaller structural effect on soil.When soil structure yields to fail during undrained shear,the structural influence of soil on its strength decreases rapidly and the soil shows certain brttleness.The additional strength provided by the structure of natural sedimentary clay is mainly contributed by cementation and soil skeleton.After the soil structure yields and fails,the cementation and soil skeleton are broken,and a new soil structure is formed,which changes the mechanical properties of the soil.