同心层状土体柱孔扩张弹塑性解

Elastic-plastic Solutions to Expansion of Cylindrical Cavities in Concentrically Layered Soil

考虑到目前多在均质土中应用圆孔扩张理论,提出同心层状土体中柱形孔扩张的弹塑性解析解。该解答基于统一强度理论和非相关联流动准则,采用应力跌落模型模拟岩土材料的软化特性并引入对数应变考虑土体大变形效应。通过对比不同弹性模量组合、软化程度、土层界面半径以及统一强度理论参数,分析扩张压力和柱形孔扩张引起的应力场的影响规律。结果表明:同心层状土体的弹性模量组合对扩张压力影响显著,对于内层弹性模量较大的组合,极限扩张压力比峰值扩张压力小;相同扩张压力作用下,土体软化程度越高扩张率越大;土层界面半径存在需要考虑两种土体相互作用的临界值;统一强度理论参数对扩张压力有一定影响,极限扩张压力随统一强度理论参数的增大而增大。

An analytical solution of cylindrical cavity expansion in concentrically layered soil was developed based on cavity expansion theory which was mostly used in homogeneous soil. This solution was analyzed with the unified strength theory and non-associated flow rule. Stress dropping model was used to simulate the strain softening behavior of soil and the logarithmic strain was introduced for large deformation. The influences of different combinations of elastic modulus,different softening degrees,radius of the interface of soil layers and the parameters of the unified strength theory on the change rules of stress fields and expansion pressure were analyzed. The results show that that the combinations of elastic modulus of double-deck soil have significant effect on the expansion pressure and the limited expansion pressure is lower than the peak value of expansion pressure with a smaller elastic modulus inside the double- deck soil; with the same expansion radius,the higher softening degree leads to lower expansion pressure; when the interface radius is small or great enough,this problem can be regarded as the same in infinite space; the interface radius has a critical size and greater parameter of the unified strength theory leads to greater expansion pressure.