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A nonlinear multi-field coupled model for soils

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Science China(Technological Sciences) 2011年第5期54卷 1300-1314页

作者： CAI GuoQing ZHAO ChengGang LIU Yan LI Jian department of geotechnique School of Civil Engineering and Architecture Beijing Jiaotong University Beijing 100044 China

A nonlinear multi-field coupled model for multi-constituent three-phase soils is derived by using the hybrid mixture theory. The balance equations with three levels (constituents, phases and the whole mixture soil) are set up under the assumption that soil is composed of multi-constituent elastic-plastic solid skeleton (which is different from the linearization method) and viscous liquid and ideal gas. With reasonable constitutive assumptions in such restrictive conditions as the principles of determinism, equipresence, material frame-indifference and the compatible principle in continuum mechanics, a theoretical framework of constitutive relations modeling three-phase soil in both non-equilibrium and equilibrium states is established, thus the closed field equations are formed. In the theoretical framework, the concept of effective generalized thermodynamic forces is introduced, and the nonlinear coupling constitutive relations between generalized dissipation forces and generalized flows within the system at nonequilibrium state are also presented. On such a basis, four special coupling relations, i.e., solid thermal elastic-plastic constitutive relation, liquid visco-elastic-plastic constitutive relation, the generalized Fourier’s law, and the generalized Darcy’s law are put forward. The generalized or nonlinear results mentioned above can degenerate into the linear coupling results given by Bennethum and Singh. Based on a specific dissipation function, the concrete form of generalized Darcy’s law is deduced, which may degenerate into the traditional form of Darcy’s law by neglecting the influence of skeleton deformation and temperature. Without considering temperature and other coupling effects, the nonlinear coupled model in this paper can degenerate into a soil elastic-plastic constitutive model.

关键词：非线性耦合耦合模型土壤弹塑性本构关系非平衡态系统混合物理论弹塑性本构模型动本构关系

Structural bonding-breakage constitutive model for natural unsaturated clayey soils

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Acta Mechanica Sinica 2010年第6期26卷 931-939页

作者： Guo-Qing Cai Cheng-Gang Zhao Xiao-Ming Qin department of geotechnique.School of Civil Engineering and Architecture Beijing Jiaotong University Beijing 100044China Hydro China Zhongnan Engineering Corporation Changsha 410014China

The natural clayey soils are usually structural and unsaturated,which makes their mechanical properties quite different from the remolded saturated soils.A structural constitutive model is proposed to simulate the bonding-breakage *** this model,the unsaturated soil element is divided into a cementation element and a friction element according to the binary medium theory,and the stress-strain coordination for these two elements is obtained. The cementation element is regarded as elastic,whereas the friction element is regarded as elastoplastic which can be described with the Gallipoli＇s *** theoretical formulation is verified with the comparative experiments of isotropic compressions on the saturated and unsaturated structural *** analyses of the effects of damage variables on the model predictions are further carried out,which show that breakage deformation of natural clayey soils increases with the rising amount of initial defects.

关键词： Unsaturated clayey soils Structure Micro-mechanism of bonding-breakage Constitutive model

REGION-WISE VARIATIONAL PRINCIPLES AND GENERALIZED VARIATIONAL PRINCIPLES ON LARGE STRAIN FOR CONSOLIDATION THEORY

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Applied Mathematics and Mechanics(English Edition) 2005年第7期26卷 944-952页

作者：罗晓辉李永乐罗昕 School of Civil Engineering Huazhong University of Science & Technology Wuhan 430074 P.R.China department of geotechnique Huabei Hydraulic and Hydroelectric Engineering Institute Zhengzhou 450008 P.R.China

The difference of constitutive character and large deformation as to soil mass are basic questions to analyze deformational feature. According to the description method of limited deformation, the large deformation consolidation equations of soil mass were created and its variational principles were rigorously testified. The regionwise variational principles of consolidation theory were deduced using sub-structure continuous condition of region-wise. Quoting the method of Lagrangian multiplier operator, generalized variational principles of region-wise of large deformation consolidation in the nonconstrained condition were created and approved.

关键词： large strain consolidation variational principle region-wise variation generalized variational principle

Stress Relaxation of Grouted Entirely Large Diameter B-GFRP Soil Nail

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China Ocean Engineering 2013年第4期27卷 495-508页

作者：李国维倪春裴华富葛万明吴宏伟 Key Laboratory of Ministry of Education for geotechnique and Embankment Engineering Hohai University Highway and Railway Engineering Institute Hohai University department of Civil and Environmental Engineering The Hong Kong Polytechnic University department of Civil and Environmental Engineering The Hong Kong University of Science and Technology

One of the potential solutions to steel-corrosion-related problems is the usage of fiber reinforced polymer （FRP） as a replacement of steel bars. In the past few decades, researchers have conducted a large number of experimental and theoretical studies on the behavior of small size glass fiber reinforce polymer （GFRP） bars （diameter smaller than 20 ram）. However, the behavior of large size GFRP bar is still not well understood. Particularly, few studies were conducted on the stress relaxation of grouted entirely large diameter GFRP soil nail. This paper investigates the effect of stress levels on the relaxation behavior of GFRP soil nail under sustained deformation ranging from 30% to 60% of its ultimate strain. In order to study the behavior of stress relaxation, two B-GFRP soil nail element specimens were developed and instrumented with fiber Bragg grating （FBG） strain sensors which were used to measure strains along the B-GFRP bars. The test results reveal that the behavior of stress relaxation of B-GFRP soil nail element subjected to pre-stress is significantly related to the elapsed time and the initial stress of relaxation procedure. The newly proposed model for evaluating stress relaxation ratio can substantially reflect the influences of the nature of B-GFRP bar and the property of grip body. The strain on the nail body can be redistributed automatically. Modulus reduction is not the single reason for the stress degradation.

关键词： stress relaxation B-GFRP bar soil nail element seamless pipe fiber Bragg grating