不同拉压模量的非饱和土体自承载能力分析

Analysis on Self-bearing Capacity of Unsaturated Soil with Different Tension-compression Modulus

为了研究沉桩施工中对非饱和土体自身承载能力的评价,借鉴抗力系数的概念,基于非饱和土统一强度理论,综合考虑材料的不同拉压模量、基质吸力及强度非线性、中间主应力效应、剪胀特性等因素,推导了理想弹-塑性非饱和土体自承载系数,并对各参数影响特性进行了分析。研究结果表明:非饱和土体自承载系数受多种因素共同影响,孔壁压力、拉压模量系数、中间主应力、剪胀特性和强度非线性均对其有显著影响;随拉压模量系数α增加,非饱和土体自承载系数与孔壁压力关系曲线经历由弹性变形和塑性流动2个阶段变为弹性变形、塑性挤压和塑性流动3个阶段;非饱和土体自承载系数均随拉压模量系数α和中间主应力参数b增加呈非线性增大,随剪胀特性参数β增加呈微弯增大;处理非饱和土强度非线性有2种方法,m值较小时,建议采用方法2,m值较大时,建议采用方法1,偏于保守。应充分考虑各个参数,合理利用非饱和土体自承载能力。

In order to study the evaluation of the bearing capacity of unsaturated soil in pile driving construction,based on the unified strength theory of unsaturated soil,the self-bearing coefficient of ideal elastic-plastic unsaturated soil was derived by using the concept of resistance coefficient for reference and considering different tension-compression modulus,matrix suction and strength nonlinearity,intermediate principal stress effect,dilatancy characteristics and other factors,and the influence characteristics of various parameters were analyzed.The results show that the self-bearing coefficient of unsaturated soil is affected by many factors,including wall pressure,tension-compression modulus coefficient,intermediate principal stress,dilatancy and strength nonlinearity;with the increase of tension-compression modulus coefficient α,the curve of the relationship between self-bearing coefficient and wall pressure of unsaturated soil has changed from two stages of elastic deformation and plastic flow to three stages of elastic deformation,plastic extrusion and plastic flow;the self-bearing coefficient of unsaturated soil increases nonlinearly with the increase of tension-compression modulus coefficient α and the parameter of intermediate principal stress b,and increases slightly with the increase of the dilatancy parameters β;there are two methods to deal with the strength nonlinearity of unsaturated soil:when the parameter m is small,the method 2 is suggested;other wise the method 1 is suggested but conservative.Various parameters should be fully considered and the self-bearing capacity of unsaturated soil should be reasonably utilized.