地基渐进破坏应变控制数值试验及极限承载力研究

Progressive failure and ultimate bearing capacity of foundation based on strain controlling loading numerical test

为对地基的加载过程进行研究,通过快速拉格朗日数值方法和极限分析方法,采用应变控制的数值试验来研究地基加载的渐进破坏过程和极限承载力.应变控制方法避开了荷载增加方法的系统不易控制性以及求解不收敛原因复杂性等问题.通过对均质地基的数值试验,揭示了地基随加载步的剪切带局部化的过程,发现地基的破坏是一个逐渐演化过程,最终的剪切带滑移模式与传统假设滑移面一致.数值试验显示加载过程中地基应力呈复杂的空间变化,荷载板受力呈中间大、两侧小的不均匀特点,且这种不均匀性随着荷载增加而增大.对不同内摩擦角进行数值试验,结果揭示其破坏的滑动体随着内摩擦角的增加,其范围的宽度和深度都相应增加.数值试验获得的破坏模式和极限承载力与传统Prandtl方法结果具有较好的一致性,该方法对于结构和参数更复杂的非均质地基也具有很好的适应性.

Strain controlling numerical test was used to study the progressive failure and ultimate bearing capacity based on both the methods of fast Lagrangian analysis and limit analysis. Strain controlling method can avoid the difficulty of system controling in failure process and the complexity of non convergence in computing. Numerical tests on uniform foundation reveal that the localization of shear zone is a gradually evolved process until it becomes fault, the final shear zone type of numerical test is in accordance with the conventionally assumed sliding surface. It also reveals that stress has complex spatial distribution in foundation, loading plate is acted by uneven force while loading, and the uneven increases with loading step increasing. Tests on different internal friction angles show that the slide scope increases with the internal friction angle increasing. Results show that the numerical test method matches well with the conventional method of Prandtl, which has better adaptation to foundation of complex structure and heterogeneity.