云母对花岗岩残积土力学性能影响的机理

Micro-mechanisms of mica effects on engineering properties of granite residual soil

本文对云母质残积土开展了微观结构测试与物理力学试验,分析了云母的结构特征及含量对花岗岩残积土物理力学特性的影响,并提出其微观作用机理。结果表明:云母的加入导致残积土的级配组成更粗,界限含水率和渗透性增加,但可塑性减小;高云母含量的残积土具有较差的力学性能,表现为较高压缩性和回弹性、以及较低的抗压强度。云母对花岗岩残积土力学性能的不利影响源于云母本身的固有性质和云母与矿物聚集体的接触形式,这是因为云母以片状层叠的形式存在于残积土中,形成具有高压缩性和回弹性的海绵状结构,层间孔隙使土壤具有高吸水性;同时颗粒排列形成的桥接和有序效应产生大量孔隙,增加了土壤的渗透性;云母板插入黏土基质后,土的强度和破坏类型也发生改变。

This paper investigates characteristics of mica and the effect of mica content on engineering properties of granite residual soils through microstructural observation and experimental study.The micro-mechanism associated with mica was interpreted.The results show that adding mica leads to a coarser gradation of the residual soil,increases of the limit water content and permeability,but a decrease of plasticity.Residual soil with high mica content has poor mechanical properties in terms of higher compressibility and hysteresis,and lower compressive strength.The detrimental effect of mica stems from the inherent nature of mica itself and the form of contact between mica and mineral aggregates.Mica presents in the form of laminate stacking and spongy structure with high compressibility and hysteresis.The bridging and fabric of the mica result in vast interlayer pores and consequently leads to high water absorption and permeability of the soil.When clay matrix sandwiched with mica flakes,the residual soil behaves differently in terms of strength and failure mechanism.