Stability Assessment of Rock Mass System under Multiple Adjacent Structures

Numerical modeling is important for exploring the fundamental processes occurring in rock and for evaluating the real performance of structures built on and in rock mass system, and thus for supporting the design of rock engineering problems. Estimating the stability of rock mass foundation systems entirely based on a theoretical approach is a complicated task if there exists overlapping of their potential collapse modes. This paper applies finite element limit analysis to evaluate the bearing capacity of equally spaced multiple strip footings resting on rock mass obeying the modified non-linear Hoek–Brown failure criterion. Numerical solutions are expressed in terms of the efficiency factor that is dependent on the spacing between footings, as well as the rock mass properties. In addition, the effects of surface surcharge and footing roughness are quantified. The maximum spacing at which the interfering effect of adjacent footings becomes disappeared is evaluated and an algebraic expression for approximating the maximum spacing is proposed. Failure mechanisms for a few cases of rock mass under multiple strip footings are examined.

Effect of size and depth on capacities of strip footings in limiting settlement approach

Structural and geotechnical engineers very often seek different options while deciding foundation sizes for buildings. In this research, the effect of different sizes and depths of strip footings below existing ground are studied based on the load bearing capacity using Geo5 spread footing software. Only vertical loadings were taken into account for this study. Four different strip footing widths (1.0m, 1.5m, 2.0m and 2.5m) were modeled under three different loads, 260kN, 600kN and 1000kN. The ground profile considered in this work was having a 2.0m thick weak layer at 6.0m below the existing ground level. Results showed that as the depth of footing increases, the depth of influence underneath the footing and settlement decreases. Also, it was noticed that as the footing width increases, the influence zone’s depth below the footing that passing the weak layer increases.