胶结性对钙质砂剪切特性影响的试验分析

Experimental analysis of influence of cementing properties on shear characteristics of calcareous sand

为研究未胶结和胶结钙质砂的剪切特性,对其进行颗粒分析试验、直剪试验以及接触摩擦特性试验。结果表明:所用钙质砂样的主要粒径集中在0.075mm至1mm之间,约占试样总质量的91.7%;未胶结钙质砂的剪应力位移曲线具有较明显的应变软化特征,且内摩擦角远高于普通石英砂。而胶结后的钙质砂剪应力位移关系却转变为应变硬化趋势,同时粘聚力升高,内摩擦角降低,抗剪强度仅得到有限的提高。这说明胶结性对钙质砂的抗剪强度起到正反两方面的耦合作用,其固化钙质砂的效果不明显。同时,接触面剪切特性试验说明胶结不仅不能有效提高桩侧摩阻力,反而是导致钙质砂桩侧摩阻力低下的重要原因。

In order to study the shearing characteristics of uncemented and cemented calcareous sand,particle analysis test,direct shear test and contact friction test were carried out.The results show that the main particle size of calcareous sand samples is between 0.075 mm and 1 mm,accounting for 91.7%of the total mass of the samples.The shear stress displacement curve of uncemented calcareous sand has obvious strain softening characteristics and the internal friction angle is higher than ordinary quartz sand.However,the relationship between the shear stress and displacement of cemented calcareous sand changed into strain hardening trend,with the cohesive forceincreasing,theinternal friction angle decreasing and the shear strength went up mildly.That above shows cementating property has positive and negative coupling effect on the shear strength of calcareous sand,and the effect of solidifying calcareous sand is not obvious.At the same time,the shear characteristic test of the contact surface shows that the cementation not only cannot effectively improve the lateral friction of the pile,but renders as an important reason for the low lateral friction of calcareous sand pile.