土的统一硬化本构理论及其工程应用

Unified hardening (UH) constitutive theory for soils and its engineering application

塑性力学奠基人Drucker首次构建了可统一考虑土的变形和强度的塑性本构理论框架,在此基础上, Roscoe结合土的基本力学特性,建立了剑桥模型,实现了对正常固结黏土的变形和强度特性的统一定量描述.针对剑桥模型无法合理描述超固结黏土和砂土的应力应变特性的缺陷,主要做出以下贡献:(1)构建统一硬化(unified hardening, UH)方程,建立了UH模型,该模型能够合理描述正常固结黏土、超固结黏土和砂土的应力应变特性,回答了剑桥学者Wroth-Houlsby之问(一),并进一步扩展为能够考虑各种复杂因素影响的特色鲜明的UH本构体系;(2)提出了广义非线性强度准则及变换应力的三维化方法,实现了本构模型和三维强度准则的合理结合,回答了剑桥学者Wroth-Houlsby之问(二);(3) UH本构体系、广义非线性强度准则和三维变换应力方法共同形成了UH本构理论,由于UH本构理论概念清晰、参数较少、实用性强,已服务于多个重大工程,并分别结合机场“锅盖效应”“智能预警”和“智能压实”等三类特殊问题开展应用.

Drucker, the pioneer of plastic mechanics theory, proposed the first plastic constitutive framework for soils which unified bothdeformation and strength behaviors. Based on this framework and the fundamental mechanical characteristics of soils, Roscoe et al.proposed the Cam-Clay model, which is capable of quantitatively describing the deformation and strength behaviors of normallyconsolidated clay. In order to address the defects that Cam-Clay model cannot adequately predict the stress-strain characteristics ofoverconsolidated clays and sands, the following contributions have been achieved: (1) The unified hardening (UH) law is proposed,and the UH constitutive model is subsequently established. The UH model can accurately describe the stress-strain characteristics ofnormally consolidated clays, overconsolidated clays, and sands. This novel work answers one of the two Wroth-Houlsby’s Questions.The UH model is extended to take into account the influences of many complex soil behaviors, forming the UH constitutive system.(2) The generalized nonlinear strength criterion and the transformed stress method are proposed in order to accurately generalize theconstitutive model to the three-dimensional stress space, which answers the second Wroth-Houlsby’s Questions. (3) The UHconstitutive theory consists of the UH constitutive system, the generalized nonlinear strength criterion and the three-dimensionaltransformed stress method. It has been widely applied to the modelling of many geotechnical engineering problems, including threeparticular issues associated with the airport engineering, i.e., “pot cover effect” “intelligent early warning” and “intelligentcompaction”.