Response of shallow foundation in rocks subjected to underground blast loading using flac3d.

Abstract

Blast loadings caused by terrorist activities, mining, quarrying, construction activities and all other operations which involve the use of explosives for rock breaking etc. can create severe problems to adjacent shallow foundations. A better understanding is required to protect shallow foundations to prevent failure of supported superstructure subjected to underground blast loadings under different rock conditions. Peak particle velocity (PPV) is important parameter in evaluating underground blast loading. PPV should be within permissible limit to avoid damage to the foundation. There are various methods available to evaluate PPV. The aim of the paper is to investigate the applicability of two methods namely Drake and Little7 and IS 692210. Typical square shaped shallow footing is modeled in three types of rocks namely, basalt, limestone and shale under saturated conditions. Finite difference based FLAC3D software is used to simulate the underground blast loads for foundations in rocks. Peak stress is calculated by using aforementioned two methods. Responses below footing have been obtained. Results in terms of time history records for pore pressure ratio, stresses, displacements, velocities and accelerations are presented. Free field peak stresses for various rocks calculated from Drake and Little7 method are greater than those calculated from IS 692210. PPV below foundations has been measured by these methods and compared with threshold limit for damage. This study shows that FLAC3D results provide useful information on behavior of shallow foundations in rocks subjected to underground blasts and can be used for practical design of such foundations.