Modified pseudo–dynamic bearing capacity of strip footing on rock masses

Abstract

In this paper, the seismic bearing capacity of a strip footing sitting on rock masses has been investigated following the upper bound theorem of limit analysis. The generalized tangential technique is used to obtain the equivalent Mohr–Coulomb parameters of the modified Hoek–Brown criterion. Considering the damping characteristics of the site as well as the dynamic characteristics of the seismic waves, the modified pseudo-dynamic (MPD) method is applied to evaluate the seismic effects. A parametric study is conducted, which shows that the seismic acceleration coefficient, the geological strength index, the material constant of the intact rock, and the normalized frequency all have a significant effect on the seismic bearing capacity. The MPD results are also compared with other methods, including the conventional pseudo-dynamic (CPD) method, spectral pseudo-dynamic method (SPD), and pseudo-static (PS) method. A high degree of agreement can be observed between the MPD results and the CPD results as the normalized frequency increases. When the normalized frequency equals 0.5 + nπ, the values of the bearing capacity factor obtained by using the MPD method and the SPD method will hit their local minima, while the CPD and PS methods will overestimate the bearing capacity factor to a large extent.