Constitutive model of disturbed soil-structure interface within mining subsidence areas

The characteristics of a disturbed soil-structure interface were studied based on the variation regularities of the disturbed soil within its mining subsidence area using direct shear tests.The effects of the initial moisture content on the shear strength parameters of the soil-structure interfaces were analyzed.The results indicate that the cohesion of the interface initially increased and then decreased as the initial moisture content increased.In addition,the friction angle of the interface decreased as the initial moisture content increased.A constitutive model of the disturbed soil-structure interface,a rigid-plastic model based on the initial void ratio and saturability(VSRP) model,was established based on the results.In order to validate this model,a finite element analysis of DRS-1 direct shear tests was conducted.The finite element model calculations coincided with the results of the DRS-1 direct shear tests.The proposed model also reflected the nonlinear features of the soil-structure interface.

A plasticity model for sand-structure interfaces

The predictive capacity of numerical analyses in geotechnical engineering depends strongly on the efficiency of constitutive models used for modeling of interfaces behavior.Interfaces are considered as thin layers of the soil adjacent to structures boundary whose major role is transferring loads from structures to soil masses.An interface model within the bounding surface plasticity framework and the critical state soil mechanics is presented.To this aim,general formulation of the interface model according to the bounding surface plasticity theory is described first.Similar to granular soils,it has been shown that the mechanical behavior of sand-structure interfaces is highly affected by the interface state that is the combined influences of density and applied normal stress.Therefore,several ingredients of the model are directly related to the interface state.As a result of this feature,the model is enabled to distinguish interfaces in dense state from those in loose state and to provide realistic predictions over wide ranges of density and normal stress values.In evaluation of the model,a reasonable correspondence between the model predictions and the experimental data of various research teams is found.

A constitutive model incorporating particle breakage for gravelly soil-structure interface under cyclic loading

Under cyclic loading,particle breakage occurs at gravelly soil-structure interface,resulting in the decrease of interface strength and the increase of normal displacement.Based on the theory of critical state soil mechanics,the modified Cam-Clay model(MCC)was extended to the plane strain condition of the interface,the state parameter was introduced and the influence of particle breakage on the critical state line was considered,and the cyclic constitutive model for gravelly soil-structure interface considering particle breakage was established by using the non-associated flow rule.Then,the established cyclic constitutive model was used to simulate large-scale cycle direct shear tests of Zipingpu rockfill-steel interface and Zipingpu rockfill-concrete interface under constant normal load(CNL)and constant normal stiffness(CNS),respectively.The simulation results show that under the CNL cyclic loading path,there is little difference between the cyclic shear stress considering particle breakage and that without particle breakage,but the normal displacement considering particle breakage is larger than that without particle breakage,and the difference increases with the increasing number of cycles and normal stress;Under the CNS cyclic loading path,with the increase of the number of cycles,the cyclic shear stress and cyclic normal stress considering particle breakage is significantly smaller than that without particle breakage,and the shear contraction of normal displacement becomes more obvious.In general,the simulation results are closer to the experimental results when particle breakage is considered.

A flexible various-scale approach for soil-structure interaction and its application in seismic damage analysis of the underground structure of nuclear power plants

In simulations of geotechnical engineering, interface elements are versatile tools and are widely used in the modeling of the relative displacements between soils and structures. To consider the case of a local failure adjacent to a soil-structure interaction region, a partial mesh refinement should be performed. In this study, a three-dimensional(3 D) interface element with an arbitrary number of nodes is developed as a new technique to reduce the complexity and difficulty of managing the various scales between soil and structure. An asymmetric number of nodes is permissible on the two sliding surfaces. In this manner, soil and structure can be discretized independently, and the various-scale model is established conveniently and rapidly. The accuracy of the proposed method is demonstrated through numerical examples. The various-scale approach is employed in an elasto-plastic seismic damage analysis of a buried concrete drainage culvert of a nuclear power plant. The results indicate that by applying the proposed method, the number of elements decreased by 72.5%, and the computational efficiency improved by 59% with little influence on accuracy. The proposed method is powerful for local damage evolution analyses of both soil and structure and possesses great practical significance and the potential for further application, especially for nonlinear analysis of large-scale geotechnical engineering.