基于坐标平移法的正常固结非饱和土三剪弹塑性本构模型

采用单应力变量法和双应力变量法建立了非饱和土的三剪统一强度准则，在此基础上用坐标平移法分别推导了相应的破坏应力比.将所得破坏应力比与非饱和土修正Cambridge模型进行结合，分别建立了单应力变量及双应力变量下的正常固结非饱和土三剪弹塑性本构模型，并对其做了ABAQUS二次开发.以南昌非饱和重塑红土为研究对象，分别对其做了非饱和土三轴固结排水试验验证、真三轴固结排水试验模拟，并研究了中间主应力影响系数b和基质吸力s对重力式挡土墙计算模型的影响.计算结果表明:所提的2种本构模型在三轴固结排水试验中均能很好地描述正常固结非饱和土的变形特性，且双应力变量下采用坐标平移法的模拟结果相对更为接近真实试验结果；在真三轴固结排水试验模拟中，采用双应力变量法相对单应力变量法所得偏应力和体应变偏大，随着中间主应力影响系数b增大，2种本构模型的偏应力和体应变也会随之增大；双应力变量下的重力式挡土墙计算模型更为稳定，随着中间主应力影响系数b或基质吸力s的增大，挡土墙模型土体位移相应减小，而墙后土体强度及稳定性相应增大.

Triple-Shear Elastoplastic Constitutive Models for Normally Consolidated Unsaturated Soils Based on the Coordinate Translation Method

The unified triple-shear strength criterion for unsaturated soils was established with the single-stress variable method and the double-stress variable method, and the corresponding triple-shear failure stress ratios were derived with the coordinate translation method. Then the triple-shear failure stress ratios were combined with the modified Cambridge model for unsaturated soils, the triple-shear elastoplastic constitutive models for normally consolidated unsaturated soils under the single-stress variable and double-stress variable were built, and the secondary development of ABAQUS was carried out. With the Nanchang unsaturated remolded clay as the research object, the consolidation and drainage (CD) test verification and true triaxial CD test simulation of unsaturated soils were done, and the effects of intermediate principal stress influence coefficient b and matrix suction s on the calculation model for the gravity retaining wall were studied. The results show that, the proposed 2 constitutive models can well describe the deformation characteristics of normally consolidated unsaturated soils in CD tests, and the simulation results of the coordinate translation method under double-stress variables are more close to the real test data. In the simulation of true triaxial CD tests, the shear stress and the volume strain obtained with the double-stress variable method are more close to the results of the single-stress variable method. With the increase of intermediate principal stress influence coefficient b, the shear stress and the volume strain of the 2 constitutive models will also increase. The gravity retaining wall calculation model with the double-stress variable method is more stable. With the increase of intermediate principal stress influence coefficient b or matrix suction s, the soil displacement of the retaining wall model will decrease, while the strength and stability of the soils behind the wall will increase.