考虑孔隙特性的压实黄土抗剪强度试验研究

Experimental study on the shear strength of compacted loess considering pore characteristics

以甘肃省临夏某机场场址黄土为研究对象,基于室内三轴剪切试验,研究了初始含水率和压实度对重塑黄土抗剪强度指标、应力路径、破坏强度的影响规律;结合室内电镜扫描试验得到的重塑黄土细观结构图像,定量分析了不同压实度下重塑黄土孔隙特性,并建立了孔隙特性与破坏强度之间的关系。研究结果表明:(1)不同初始含水率和压实度条件下重塑黄土应力-应变关系曲线形式为软化型、弱硬化型和强硬化型:7%含水率以下、90%压实度以上条件下为软化型,7%含水率、85%压实度以下及9%含水率、90%压实度以上条件下为弱硬化型,其余条件下则为强硬化型;(2)重塑压实黄土应力路径曲线呈斜直线形式,曲线形式基本不受压实度和含水率影响;(3)重塑压实黄土抗剪强度指标、破坏强度随初始含水率的增加而减小,随压实度的增加而增大;(4)重塑压实黄土破坏强度与微、小孔隙含量成正比例关系,与中、大、特大孔隙含量及孔隙平均周长和面积成反比例关系。

On the basis of indoor triaxial shear test,the effects of initial moisture content and compactness on the shear strength index,stress path,and failure strength of the remolded loess from an airport site in Linxia,Gansu Province were studied.Pore characteristics of the remolded loess under different compaction degree were quantitatively analyzed by using microstructural images from the indoor scanning electron microscope test.The relationship between pore characteristics and the failure strength was also established.The results show the following:(1)The stress-strain curves of remodeled loess under different initial water content and compaction degree are divided into three forms:softening type(below 7%water content and above 90%compaction degree),weak hardening type(below 7%water content and 85%compaction degree or above 9%water content and 90%compaction degree),and hardening type(other condition);(2)The stress path curve of the compacted loess takes the form of oblique straight line,which is not affected by the compaction degree and moisture content;(3)The shear strength index and failure strength of the compacted loess decrease with the increase in the initial moisture content,and increase with the increase in the compaction degree;(4)The failure strength of the compacted loess is positively proportional to the content of micro and small pores;while it is inversely proportional to the content of medium,large,and extra large pores and the average perimeter and area of pores.