人工胶结粉质粘土的强度、变形特性试验研究

Experimental Study on the Strength and Deformation Characteristics of Artificially Cemented Silty Clay

人工胶结结构性土(改良土)被广泛应用于天然地基土的物理力学特性改良。然而,这种土在具有较高的强度与刚度的同时,往往表现出较强的非线性力学行为。以水泥胶结粉质粘土为例,通过三轴试验系统地研究了具有不同胶结结构性程度试样的强度特性及变形特性。研究发现胶结结构性土往往呈现出显著的应变软化特征(脆性破坏),其峰值强度为一种受围压及胶结结构性影响显著的状态相关参数,而残余强度为一种受围压及胶结结构性影响较小的状态无关参数。胶结结构性土的压缩刚度明显高于重塑胶结土(无胶结结构性),其等向压缩曲线(ICL)会伴随胶结损伤逐渐屈服并趋近于重塑胶结土的正常固结曲线(NCL),这为间接确定胶结结构性土的NCL提供了思路。不同于超固结粘土或密实砂土的“剪胀软化”,胶结损伤会诱发胶结结构性土的“剪缩软化”现象。此外,胶结结构性土中的应变局部化会影响试样的整体体变趋势,使得其临界状态线(CSL)与相应的重塑胶结土CSL之间存在着差异。

The artificially cemented soil is widely used to improve the physical and mechanical properties of the natural ground.However,this type of the cemented soil often exhibits a strong nonlinear mechanical behavior while having the high strength and stiffness.This paper takes cement-bonded silty clay as an example to systematically analyze the strength and deformation characteristics of samples with different degrees of the cemented structure.The results show that the artificially cemented soil often exhibits significant strain softening characteristics(brittle failure),and its peak strength presents as a state-dependent parameter that is significantly affected by the confining pressure and the structure degree,while the residual strength presents as a state-independent parameter that is less affected by the confining pressure and the structure degree.The compressive stiffness of the cemented soil is significantly higher than that of the remodeled one,and the degradation of cemented structure under the high pressure will cause the isotropic compression line(ICL)to yield and gradually converge to the normal consolidation line(NCL)of the remodeled cemented soil,which provides a way to determine the NCL of the cemented soil.Different from the“shear dilatancy softening”of the over-consolidated clay or the dense sand,the“shear shrinkage softening”phenomenon of the cemented soil often occur due to the degradation of the cemented structure.In addition,the strain localization phenomenon in the cemented soil will affect the overall volumetric change of the sample,resulting in some difference in the critical state lines of artificially cemented soil and corresponding remodeled one.