论文部分内容阅读
地基极限承载力的确定对于下伏空洞地区基础设计和施工具有重要意义。采用上限有限元法对地基破坏时的极限状态进行数值模拟。首先,简要介绍上限有限元法的基本原理与计算过程;进而提出合理的计算假定,建立可考虑多种影响因素的计算模型;其次,利用上限有限元法计算出多种工况下的地基极限承载力上限解,按Tergaghi建议的地基承载力公式,得到承载力系数N_c、N_q、N_g,并对其影响因素进行分析;最后,根据大量的能量耗散图及速度场图提出3类典型的破坏模式,并对其影响因素进行分析。研究表明:随着内摩擦角j的增大,N_c和N_q均增大,而当j较大时,N_g才出现正数,且随着j增大而增大;随着空洞顶板厚度与基础宽度之比H/B的增大,N_c和N_q均增大。而当j较小时,N_g随着H/B的增大而减少;当j较大时,N_g随着H/B的增加而增加。N_c、N_q和N_g均随着D/B的增大而减少。下伏空洞地基存在3种典型的破坏模式:冲切破坏模式、冲切剪压破坏模式和Prandtl破坏模式。
The determination of the ultimate bearing capacity of foundation is of great significance to the foundation design and construction of underlying empty areas. The finite element method of upper bound was used to simulate the ultimate state of foundation under failure. First of all, the basic principle and calculation process of upper limit finite element method are briefly introduced. Then, reasonable calculation assumption is put forward and a calculation model considering various influencing factors is established. Secondly, the upper limit finite element method is used to calculate the limit of foundation under various working conditions According to the formula of bearing capacity of foundation proposed by Tergaghi, the bearing capacity coefficients N_c, N_q, N_g are obtained and the influencing factors are analyzed. Finally, according to a large number of energy dissipation maps and velocity field maps, three types of typical Destruction mode, and analyze its influencing factors. The results show that N_c and N_q increase with the increase of the internal friction angle j, whereas when j increases, the positive value of N_g appears and increases with the increase of j. Width ratio H / B increases, N_c and N_q are increased. When j is small, N_g decreases with the increase of H / B. When j is larger, N_g increases with the increase of H / B. N_c, N_q and N_g decrease with the increase of D / B. Three kinds of typical failure modes exist in the underground cavity below: punching failure mode, punching shear failure mode and Prandtl failure mode.