深层结构性土压缩特性试验研究

Experimental Study on Compressibility of a Structured Soil at Greater Depth

选取常泰长江大桥场区深层粉质黏土为研究对象,通过固结试验和无侧限抗压强度试验,着重分析了原状土的压缩曲线特性,揭示了研究区域深部结构性土层的力学强度和变形特征。试验结果表明:研究区域土层压缩曲线为反S型,呈现4阶段特征,具有明显的陡降段;同时具有高孔隙比、高饱和度、高灵敏度等特点;深层结构性土需考虑卸荷作用引起的土样变形;深层结构性土实际结构屈服应力δpc小于由Casagrand图解法求出的pc,建议结合e~lgP和Es~P两种曲线综合确定pc值。

This paper investigates the compressibility properties of the soil samples at a large embedment depth on the site from Chang-Tai Yangtze River bridge site by using the consolidation tests and the unconfined compression tests.The compression curve characteristics of the undisturbed samples are mainly analyzed to reveal the compressive strength and the compression deformation of the deep structured soil.The test results show that the consolidation curves of the undisturbed samples exhibited essentially inverse sigmoid shape,which involve four distinct phrases with a dramatical drop-down segments.The results also indicated that the tested soil samples are of high void ratio,high saturation,and high sensitivity.Such observations suggested that the deformation of the soil sample caused by the unloading should be properly taken into consideration for the deep structural soil in the engineering practice.In addition,the actual structural yield stress of the deep soil is less than pc calculated by the Casagrand graphical method.As such,it is suggested to combine e~lgPand Es~P curves to collaboratively determine the structural yield stress of the deep soil.