考虑模量变化与三维应力影响的地基沉降分析方法

鉴于三维应力作用下土变形模量变化的根本原因在于体积变化,首先视地基土是由孔隙与土颗粒骨架组成的两相介质,将地基土单元抽象为空心球壳单元,利用Walsh公式及体积应力作用下的球壳位移计算公式,导出了地基土变形模量、土颗粒骨架变形模量与地基土孔隙率之间的关系模型,在此基础上,考虑地基土变形模量变化的非线性特征,引进分级加载思想,建立了增量体积应力作用的地基土变形模量变化的递推关系模型,然后,考虑三维应力影响,联合引进分层总和与分级加载的思想,利用前述地基土增量体积应力作用的地基土变形模量变化的递推关系模型,建立了新的地基沉降分析方法.该方法不仅能反映三维应力及变形模量变化对地基沉降分析的影响,还能有效避免地基土压缩试验曲线或地基静载试验曲线的使用.通过工程实例计算,并与现有同类分析方法进行比较分析,表明了本文模型与方法的合理性与优越性.

An Analytical Method of Ground Foundation Settlement Influenced by Modulus Change and Three-dimensional Stress

Since the primary cause of the variation of soil deformation modulus lies in the change of soil volume under three-dimensional stress, firstly, a ground foundation soil was regarded as a two-phase medium composed of hole and soil grain skeleton. A unit of ground foundation soil was abstracted into a unit of hollow spherical shell. An analytical model on the relationship among deformation modulus of ground foundation soils and soil grain skeleton as well as soil porosity was deduced by the Walsh formula and the displacement formula of spherical shell under volume stress. On this basis, the nonlinear characteristics of deformation modulus change of ground foundation soils was considered and the thought of step-loading was introduced, and then an iteration relation model of deformation modulus of ground foundation soils under incremental volume stress was developed. Afterwards, the effect of three-dimensional stress was taken into account, and another thought of layer-wise summation combined with step-loading was adopted. A new ground foundation settlement analysis method was then proposed by using the above-mentioned iteration relationship model for deformation modulus variation of ground foundation soils. It can not only reflect the influences of three-dimensional stress and deformation modulus variation of ground foundation soils on the analysis of ground foundation settlement, but also avoid the use of the compression curve of ground foundation soils or the static load test curves of ground foundation. Finally, the computation and analysis of practical engineering examples as well as the comparisons between the measured and calculated settlement results by the other existing methods show that the model and method proposed are more reasonable and feasible.