基于特征线法网格划分的主动土压力有限元计算

Characteristic line mesh division for active earth pressure calculation in finite-element method

针对有限元法网格划分存在人为因素且不能保证精度的不足,提出特征线法划分网格的新方法。假定通过墙踵的滑移线为滑裂面,采用Duncan-Zhang(E-υ)模型,将其运用于主动土压力的有限元分析计算。研究结果表明:本构模型参数对边界节点应力影响不大,但实验常数K和破坏比Rf对其位移有影响;当墙土摩擦角δ>0°时,最大主应力σ1对边界的土体稳定性影响最大,宜将其作为主动土压力pa进行计算;当δ=0°时,取最小主应力σ1=pa,此时为Rankine理论的表现形式;绘制节点pa分布图,求得主动土压力合力Ea;以底部计算点为矩心,用合力矩定理求得Ea作用点的位置y。经过与Coulomb解的对比和已有实验结论的验证,表明计算结果可靠,方法可行。

In order to overcome the disadvantages of human factors and less precision in mesh division,a new approach of characteristic curve mesh generation was established.Using the hypothesis of glide lines crossing at the wall-heel as a slip crack surface,the Duncan？Chang（E？υ） nonlinear elastic model was used for calculation of active earth pressure in finite-element method.The results show that constitutive model parameters play a minor role in boundary node stresses but experimental constant K and break ratio Rf have a larger impact on displacement.The maximum principal stress σ1 plays the biggest influence in stability of earth mass boundary when the internal friction angle of earth mass δ is more than 0° and it is appropriate to take σ1 as active earth pressure pa.The minimum principal stress σ3 equals pa and has an expression of Rankine＇s in case of δ=0°.From the distribution of pa on nodes,the total active earth pressure Ea can be decided and the corresponding position y of application point of Ea can be determined by resultant moment theorem at the bottom of earth mass.The results are compared with those from Coulomb＇s earth pressure theory and verified by the existing ones from experiments,indicating that the calculated precision is realizable and the new method is feasible.