Failure analysis based optimum hole spacing of underexcavation for leaning building rectification

Abstract

The underexcavation technique is one of the most commonly used ones for the rectification of leaning buildings. It usually involves hole digging, and soil removing in the base. The potential failure of the soil between the digging holes determines the hole spacing, which is of critical importance in the safety and efficiency of the entire rectification procedure. The determination of the hole spacing is primarily related to the soil parameters, the upper load induced by the structure, and the holes diameter. In context with this problem, an experimental study, and related computational simulations were conducted with three different hole spacing values. The failure mode of the soil between the holes, and the settlement were studied. It was found that for smaller hole spacing, the failure and the settlement of the soil was more pronounced. Thus, an optimal hole spacing was sought, which was related to the starting point of the leaning building straightening back. In this context, the finite element limit method was employed to determine the optimal hole spacing, with the soil ultimate strain treated as the failure criterion. Further, a parametric study on typical clay and silty soils was undertaken, and the optimal hole spacing values for different upper loads were determined for three typical cases of soil parameters. Finally, three actual rectification projects were considered to assess the reliability of the developed procedure. Hopefully, this method can be a facilitating tool for apriori studies, and initial planning of rectification related engineering projects.