考虑弹塑性卸荷的柱孔和球孔反向扩张解  

Cylindrical and spherical cavity reverse expansion considering elastoplastic unloading

作　　者：张家奇 赵春风[1,2] 赵程[1,2] 吴悦 龚昕 ZHANG Jia-qi;ZHAO Chun-feng;ZHAO Cheng;WU Yue;GONG Xin(Key Laboratory of Geotechnical and Underground Engineering,Ministry of Education,Tongji University,Shanghai 200092,China;Department of Geotechnical Engineering,Tongji University,Shanghai 200092,China;School of Civil Engineering,Chongqing Jiaotong University,Chongqing 400074,China;College of Building Engineering,Jinggangshan University,Ji’an,Jiangxi 343009,China)

机构地区：[1]同济大学岩土及地下工程教育部重点实验室,上海200092 [2]同济大学地下建筑与工程系,上海200092 [3]重庆交通大学土木工程学院,重庆400074 [4]井冈山大学建筑工程学院,江西吉安343009

出　　处：《岩土力学》2023年第11期3224-3234,共11页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.U1965108,No.42142019,No.41672265);重庆市自然科学基金博士后基金项目(No.CSTB2023NSCQ-BHX0149);中国博士后科学基金面上项目(No.2023MD734112)。

摘　　要：为研究卸荷对灌注桩、隧道等复杂受力岩土结构的影响,建立了考虑弹塑性卸荷的圆孔反向扩张简化解模型。该模型在应力计算中采用了叠加法的思想,在反向塑性区采用了非关联的Mohr-Coulomb准则、塑性区大应变假设和忽略塑性区弹性应变的假设。研究表明,圆孔反向扩张过程可划分为弹性阶段和两个弹塑性阶段。当孔压重新加至初始值时,不论柱孔还是球孔其半径均未能恢复到初始值,且在孔周存在一定范围的应力薄弱区。与经典原位扩张解相比,当圆孔压力增至一定值后圆孔反向扩张的屈服面发展、圆孔应力变化及孔周应力场将与之趋于一致。忽略塑性区的弹性应变假设会使简化解的土体位移偏小,极限扩张压力偏大,但对应力相关量的计算没有影响。与Tresca解相比,所提模型考虑了内摩擦角的影响,更接近于土体实际。通过数值模拟建立了圆孔反向扩张的平面应变模型,其应力分析结果与理论模型基本一致。To study the influence of unloading on complicated geotechnical structures such as cast-in-place piles,tunnels,etc,a simplified solution model of cavity reverse expansion considering elastoplastic unloading in drained soil is established.In this model,the superposition method is adopted in the derivation of stresses.In the reverse plastic zone,the non-correlated Mohr-Coulomb criterion,the assumption of large strain and ignoring the elastic strain are adopted.This study shows that the reverse expansion process can be divided into an elastic and two elastoplastic stages.When the cavity pressure is restored to the initial value,the radius of both cylindrical and spherical cavities cannot revert to the initial value,and there is still a certain range of stress weak zone around the cavity.Compared with the classical in-situ expansion solution,the yield surface development,stress variation and stress field around the cavity tend to be the same when cavity pressure increases to a certain value.The assumption of ignoring the elastic strain in the plastic zone will lead to a smaller displacement and a larger ultimate expansion pressure of the simplified solution,but it has no effect on the stress-related quantities.Compared with the Tresca solution,the proposed model takes into account the effect of internal friction angle and is closer to the actual soil mass.A plane strain model of cavity reverse expansion is established by numerical simulation,and the stress analysis results are basically consistent with that of theoretical model.

关 键 词：弹塑性卸荷 圆孔反向扩张 圆孔半径 大应变假设 孔周应力场 

分 类 号：TU441[建筑科学—岩土工程]