Study On Soil-structure Interface Model Based On Potential Energy Dissipating Principle And Its Application

Soil-concrete interface determines the behavior of many geotechnical structures, and it is the micro-representive of soil-structure interaction. Therefore, proper understanding of the interface shearing mechanisms and establishing its good constitutive model are essential in both theory aspect and practical aspect. In this paper, soil-concrete interface behavior is comprehensively studied including laboratory tests, interface element and interface constitutive law, and a new constitutive model considering previous shear ratio is proposed based on laboratory tests and some potential energy dissipating theory postulates. The mew-built 3-parameter model is generalized to some geotechnical subjects. Finally, pure mathematic analysis on relationship between the new model and traditional models are conducted. The main contents can be summarized as follows:(1) According to direct shear tests on four kinds of interface types, analysis on interface behavior changed with soil water content and contacted structure is conducted, and conclusion that interface behavior depends closely on structure hydrophilic nature is made.(2) Improved simple shear tests on soil-concrete interface, considering four soil water contents and four previous shear ratios, are accomplished, and interface behaviors under different soil water contents and previous shear ratios are analyzed in details. Shear failure position of the interface is recorded, too.(3) Combined with tests results and potential energy dissipating theory postulates, control differential equation for interface stress-strain relationship is developed, and a new 3-paramenter model for it is established. Appraisal factor for the 3-paramenter model is presented and fitting accuracy of the new model is proved by many laboratory tests results. Form potential energy dissipating theory and control differential equation angles, the relationships between the 3-paramenter model and corresponding traditional models are discussed, and mathematics "half value index" is used to point out deficiency of traditional models in both mathematics and mechanical theory.(4) A new interface constitutive model neglecting previous shear ratio is presented on the basis of above established 3-parameter stress-strain model.(5) Based on improved simple shear tests on soil-concrete interface, the concept "critical previous shear ratio" is put forward, then a new interface constitutive model based on potential energy dissipating theory considering previous shear ratio is proposed.(6) Form potential energy dissipating principle and control differential equation angles, the developed 3-parameter model is generalized to constitutive model of soil itselfand to one kind time effect geotechnical subject, including expansive deformation of expansive soil, time-dependent ultimate bearing capacity of pile, post-settlement of municipal refuse landfill and post-settlement of soft foundation. Finally, the nature of this kind subject is indicated that they have same control differential equation, and deficiency of their traditional models in both mathematics and mechanical theory is analyzed, too.(7) According pure mathematic proof, conclusion that 2-parameter hyperbolic model and exponential model are both simplified types of the new 3-parameter model is made. Two mathematic methods are presented to prove that 2-parameter hyperbolic model and exponential model are the superior limit and lower limit of the corresponding new 3-parameter model respectively. Three mathematic methods are put forward to confirm that the value of exponential model is larger than that of corresponding 2-parameter hyperbolic model.