中文摘要：

临界填土高度是软土路堤沉降和稳定控制的重要指标,首先推导3种真三轴强度准则即广义M-N准则、广义L-D准则和统一强度理论的平面应变统一表达式,进而合理考虑中间主应力影响和土体实际侧压力系数,建立地基临界荷载与路堤临界填土高度的统一解,给出公式适用条件并进行验证,最后探讨路堤临界填土高度的强度理论效应,并得出土体黏聚力和内摩擦角对路堤临界填土高度的影响规律。研究结果表明：提出的统一解具有很好的可比性,且其强度理论效应即中间主应力效应明显;M-C准则的结果过于保守,应优先选用广义M-N准则、广义L-D准则或参数b=1/2时统一强度理论;侧压力系数、黏聚力及内摩擦角对路堤临界填土高度的影响均很显著,应原位测试确定地基土的真实侧压力系数,并充分考虑土体抗剪强度参数的变异性。

英文摘要：

The critical filling height is an important index for the settlement and stability control of embankment on soft soils. A unified formula under the plane strain condition was firstly deduced for three true triaxial strength criteria,i.e.,the generalized M-N criterion,the generalized L-D criterion and the unified strength theory. Then,the unified solutions for both the critical load of foundation and the critical filling height of embankment were presented by considering the intermediate principal stress and the actual lateral pressure coefficient. The unified solutions were validated and their applicable conditions were also provided. Finally,the effect of strength theory was investigated and parametric studies about the influence of cohesion and inner friction angle on the critical filling height of embankment were discussed. It is found that the proposed unified solutions have good comparability. The effect of strength theory（i.e.,the intermediate principal stress effect） on the critical filling height of embankment is remarkable and the result of M-C criterion is too conservative. Moreover,the generalized M-N criterion,the generalized L-D criterion and the unified strength theory with parameter b =1/2 are recommended to be adopted. The influence of lateral pressure coefficient,cohesion and inner friction angle on the critical filling height is significant. A real lateral pressure coefficient should be determined in situ,and the variability of strength parameters of ground soils should be fully considered.