平面应变条件下基于Lade-Duncan强度准则中主应力条件的土压力及其适用性

Earth pressure attibutes and applicability under plane strain condition based on principal stress condition in Lade-Duncan strength criterion

针对实际工程中大量存在的挡土墙、基坑开挖等平面应变问题,考虑中主应力对强度的影响,将平面应变条件下Lade-Duncan强度准则的中主应力关系代入SMP、Lade-Duncan、AC-SMP和广义Mises强度准则中得到新的平面应变强度准则。据此建立基于各强度准则的主、被动土压力计算公式,进而推广至黏性土,并将主、被动土压力理论计算值与实测值进行对比分析。结果表明,Mohr-Coulomb强度准则因其未考虑中主应力的影响,致使计算结果相比实测情况偏保守;SMP强度准则、Lade-Duncan强度准则考虑到中主应力对土压力大小的影响,计算结果相比Mohr-Coulomb强度准则更接近实测情况;AC-SMP强度准则、广义Mises强度准则在一定内摩擦角范围内可以描述挡土墙的土压力大小,但超出适用范围时,二者均不再适用于描述挡土墙的土压力大小;广义Mises强度准则在适用范围内的计算结果相比SMP强度准则、Lade-Duncan强度准则更接近实测数据。

In the engineering practice,the retaining wall and foundation pit could be regarded as a plane strain condition.Considering the influence of intermediate principal stess on the strength,we obtained the new plane strain strength criterions by substituting the intermediate principal stress relationship of Lade-Duncan strength criterion into SMP and Lade-Duncan,AC-SMP and the generalized Mises strength criterion.Based on these modified strength criterions,active and passive earth pressure models were established,and then extended to cohesive soil.The theoretical and measured values were compared and analyzed.The results show that the effect of intermediate principal stress on earth pressure is significant.The Mohr-Coulomb strength criterion fails to consider the influence of intermediate principal stress,and therefore the calculation results are more conservative than measurement.Considering the influence of the principal stress,the results of SMP and Lade-Duncan strength criterion are much closer to measurement than MC.The AC-SMP and generalized Mises strength criterion can describe the earth pressure of the retaining wall only within a certain range of friction angle,but when it exceeds the applicable range,both are no longer suitable.The calculations of the generalized Mises strength criterion,within the applicable range,are closer to actual data compared with the SMP and Lade-Duncan strength criterion.