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为分析城市浅部地层中椭圆形空洞的稳定性,采用复变函数理论求得了自重应力及竖向均布荷载作用下含隐伏椭圆形空洞地层应力场的精确解答。以莫尔–库仑剪切屈服准则及土体抗拉强度等于零为判别依据,求得洞周初始塑性区范围,分析了空洞形状及外部荷载对塑性区位态的影响。结果表明:1在自重应力场下,地层中近圆形或瘦长状椭圆空洞自身稳定性相对扁平状空洞较好;扁平状空洞以受拉破坏为主。2外部荷载作用下地层空洞破坏模式为拉–剪综合破坏,随着外部荷载的增大,剪切塑性区与受拉区贯通,并向地层深部转移,加速地层空洞的失稳破坏。3在大量分析计算的基础上给出了空洞地层的5种分区模式。空洞地层灾变事故控制的核心是空洞结构自身的稳定性,空洞地层初始破坏的分析是确定其破坏模式以及破坏区域的关键。研究结果对城市空洞地层灾变事故的预测、评估及其处理具有重要意义。
In order to analyze the stability of oval cavity in urban shallow stratum, the exact solution to the stress field of concealed oval cavity under self-weight stress and vertical uniform load was obtained by using complex variable theory. Based on the criteria of Mohr-Coulomb shear yielding criterion and soil tensile strength equal to zero, the range of initial plastic zone was obtained and the influence of void shape and external load on the plastic zone state was analyzed. The results show that: 1 Under the self-weight stress field, the stability of oval hollow or oval hollows in the formation is relatively flat and voids; the flat voids are mainly subjected to tensile failure. Under the action of external load, the formation failure mode of the stratum is a combination of pull-shear failure. As the external load increases, the shear plastic zone and the tension zone penetrate and move deeper into the formation, accelerating the instability of formation cavities. Based on a large number of analysis and calculation, five kinds of zoning patterns of hollow stratum are given. The core of the control of catastrophic accidents in the hollow formation is the stability of the hollow structure itself. The analysis of the initial destruction of the empty formations is the key to determine the failure mode and the damaged area. The research results are of great significance to the prediction, assessment and treatment of catastrophic accidents in urban hollow formations.