基于细观结构的压实黄土抗剪特性试验研究

Experimental Study on Shear Characteristics of Compacted Loess based on Micro-structure

压实度是填方工程质量验收的主要控制项目之一,较高压实度对改善黄土力学性能效果显著。为全面系统分析压实对黄土抗剪特性的影响规律,更好地揭示较高压实度提高黄土抗剪能力的内在原因,利用室内三轴剪切试验和电镜扫描试验,基于4种不同压实度,对甘肃省临夏市北塬地区压实黄土的抗剪特性和细观结构进行了研究。研究表明:压实黄土应力—应变满足双曲线形式,较高压实度对提高黄土体抗剪强度和剪切模量作用显著;较高压实度通过改变土体颗粒之间的接触形式以改善黄土体抗剪特性,主要表现为压实黄土颗粒之间的接触形式随着压实度的增加由棱边接触、支架镶嵌向面接触逐渐过渡;较高压实度通过改变土体孔隙尺度特征和形态分布以改善土体抗剪特性,主要表现为随着压实度的增加孔隙分布范围内微、小孔隙的含量增加,中、大、特大孔隙含量减小,孔隙形状也相对变得圆滑。

The compaction degree is one of the main control items for quality acceptance of filling engineering,the research shows that higher compaction degree has a significant effect on improving the mechanical properties of loess.In order to comprehensively and systematically analyze the influence of compaction on the shear properties of loess and better reveal the internal reasons for the improvement of the shear strength of loess by high pressure compaction,the shear properties and micro-structures of compacted loess in the Beiyuan area of Linxia City,Gansu Province were studied by means of triaxial shear test and scanning electron microscopy test based on four different compaction degrees.It is found that the stress-strain relation of the compacted loess satisfies hyperbolic form,and higher compaction degree has a significant effect on improving the shear strength and shear modulus of loess;Higher compaction improves the shear resistance of loess by changing the contact form between soil particles,which transforms gradually from edge contact and bracket to surface contact with the increase of compactness;Higher compaction improves the shear resistance by changing the characteristics and morphological distribution of soil pore size,showing a gradual increase of pore scale of micro and small pores with the increase of compaction,while the content of medium,large and extra large pores decreases,and the pore shape becomes relatively smooth.