"DYNAMIC ANALYSIS OF NAILED OPEN CUTS"

Abstract

Soil Nailing technique is used for stabilizing the tunnel portal and shafts, slopes and to support the excavations and also for remedial uses like repair of unstable old retaining walls, stabilization of failed slopes etc. by increasing the apparent cohesion of the soil. This method is very easy and effective method in earthquake prone areas. At present, only static and Pseudo-static analysis of a nailed open cut has been reported in the literature. Dynamic analysis is most significant for soil nailing projects in earthquake prone regions of India. In the present study dynamic analysis of nailed open cuts is presented in order to obtain the displacements of the cut. It is assumed that nailed soil mass corresponding to a pseudo - static factor of safety equal to unity moves during the earthquake. The soil behind this mass is replaced by series of springs and the nails being replaced by stiffeners. Equation of motion works out to be a two degree differential equation, which on integration and putting proper boundary conditions yield the displacement of the cut. Computer programs have been developed to evaluate the critical failure surface with a Factor of Safety of unity and to evaluate the displacements of the nailed cut in MATLAB. A three — dimensional model has been developed in ANSYS to validate the displacements obtained from the MATLAB code. Also parametric study has been carried out to study the effect of nail characteristics and height of cut and the displacement results are plotted. It has also been observed that the displacement of nailed cut is very much dependent on the height of the cut and length, diameter and spacing of the nai