原状与重塑红黏土强度变化机理

Strength Change Mechanism of Undisturbed Red Clay and Remolded Red Clay

为了研究红黏土强度特性及其影响机理,对不同法向应力作用下的原状土样和重塑土样进行了直剪试验。采用扫描电子显微镜测试,对比分析原状土和重塑土颗粒单元间接触、连结状态、孔隙形态及分布等微观结构差异,揭示了土体微观结构对宏观力学性质的影响机理。研究结果表明:当法向应力σ小于临界应力时,原状土的剪应力τ高于重塑土;反之,原状土的τ低于重塑土。临界应力的大小取决于土体孔隙比,孔隙比越大,临界应力越大。原状土黏聚力高于重塑土,内摩擦角低于重塑土。重塑土与原状土力学性质存在明显差异,且差异性的大小取决于原状土微观结构性能的好坏。提出了红黏土闭孔孔隙和开孔孔隙的概念,并将其用于红黏土抗剪强度的机理分析,具有一定的工程指导意义。

In order to study the strength characteristics and influencing mechanism of red clay,direct shear tests were carried out on undisturbed soil samples and remolded soil samples under different normal stresses σ.Scanning electron microscopy( SEM) was used to compare and analyze the differences of microstructure between the undisturbed soil and remolded soil,such as particle unit contact,joint state,pore morphology and distribution. The influence mechanism of soil microstructure on macroscopic mechanical properties was revealed. The results show that when σ is less than the critical stress,the τof the undisturbed soil is higher than that of the remolded soil,otherwise,the undisturbed soil τis lower than the remolded soil.τThe critical value depends on the void ratio of the soil. The larger the void ratio is,the larger the critical value is. The cohesive force of the undisturbed soil is higher than that of the remolded soil,and the internal friction angle is lower than that of the remolded soil. There are significant differences in the mechanical properties between the remodeling soil and the undisturbed soil. The magnitude of the difference depends on the microstructure of the undisturbed soil. The concept of "closed pores and open pores"of red clay is proposed and applied to the mechanism analysis of shear strength of red clay,which has certain engineering guiding significance.