The Elastoplasticity And Rheological Analysis And Their Application Of Foundation Pit Excavation

At the present, there are mainly two methods of analysis foundation pit excavation, one is the classical analysis method taking the limit equilibrium means as the dominant factor, the other is the numerical analysis method taking the plane finite element means as the dominant factor. Among the two methods, the limit equilibrium means regards the soil mass as the rigid-plastic body, without regard for the concrete property of the soil mass; The numerical analysis method taking plane finite clement means as the dominant factor treats the soil mass with various aspects, referring to the constitutive models of soil mass contain the elastic model, elastoplastic model and rheological model. Relatively speaking, the elastic model and elastoplastic model are used more, while the rheological model is used less, and without systematicness. In actual engineering, he soft clay in the economic developed district along with the sea at southeast China behaves a very strong rheological property, where the foundation pit engineering抯 quantity is great, the success rate of foundation pit is lower than that of the district of better geological condition, Therefore, in the engineering of foundation pit, overall considering the rheological property of soil mass is one researching project of great significance. This paper, starting from the elastoplastic analysis of foundation pit excavation, enters all.sidely rhaological analysis, sets up a whole set of calculation method used in rheological analysis of foundation pit excavation, whose contents include: 1. On the basis of overall elastoplastic analysis on the excavation problem of foundation pit, to counter the shortage of traditional analysis method about some questions, puts forward its original view which contains: A. The critical thickness calculation of cutoff soil horizon with confined water, the method put forth in this paper is clear in mechanic concept, simple in computation, in the calculation for actual engineering problem behaves much more superiority than traditional method; B. As regards the critical height calculation of erect excavation of circular foundation pit, this method throws away the shortcoming that all the critical height problems of erect excavation were regarded as plane ones in traditional method, and puts forward its own calculation formula for the erect excavation height of circular and similar circular foundation pit, which is specially useful to the foundation pit with less diameter; Besides, it has also made the corresponding approach for the problems about the stress distribution in soil and the variation of porousness water pressure in foundation pit excavation. 2. To counter the shortage in research on the rheological property and model theory soil mass in soil mechanics, this paper introduces a new kind of mechanics, this paper introduces a new kind of rheological model theory; The fractional derivation rheological model theory, which has overcome the shortcoming of bad coincidence for the classical model theory with the test result, only adopting quite few components combination can obtain an excellent efficiency, of which the dynamic modulus can coincide well with testing data within quite wide frequency range. Utilizing this model theory can manufacture out various soil mass rheological models of good coincidence with tests, and can describe well the instantaneous elasticity of soil mass, delayed elasticity, viscosity flow, plasticity etc, and introduces a practical method which doesn抰 need any model, but can directly construct the relaxation model module and compliance, and can fit the...