A hybrid finite element procedure for soil-structure interaction including construction sequences

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Virginia Polytechnic Institute and State University

An alternative to the displacement finite element method, the hybrid stress model, is applied to problems in geomechanics. A two-dimensional finite element procedure based on the hybrid stress model is developed for simulation of construction sequences including underground and surface excavations. In this procedure, an eight-node isoparametric element is employed. In the analysis, the effect of soil-structure interaction is incorporated by using a special interface element for behavior at the contact between two different materials.

In the elastic-plastic analysis, the Drucker-Prager model is used as a constitutive law. In order to verify the computer program and to examine the accuracy of the hybrid stress model, several problems such as a beam, a plate with circular hole, and footings are analyzed, and the results are compared with those from the displacement method and closed-form solutions.

The proposed procedure for simulation of excavation is verified by performing an excavation in linear elastic material. Finally, two field cases of excavation are solved and the results are compared with the displacement method and the field observations. It is believed that the proposed (stress) hybrid method can have significant potential of application for various problems in geomechanics, and it can be particularly appropriate for a situation where computation of stresses is important.