A generic approach to soil–structure interaction considering the effects of soil heterogeneity

Abstract

The longitudinal variation of soil properties has a major influence for many types of structure, including pavements, buried pipes, raft foundations and railways, as it induces stresses and/or displacements that cannot be predicted when assuming soil homogeneity. A set of simple numerical models has been developed to describe how soil–structure interaction can be influenced by soil variability. These models include: (a) a description of the soil spatial variability, within the frame of geostatistics, where the correlation length of soil properties is the main parameter; and (b) a mechanical description of the soil–structure interaction, which depends on the structure resting on the ground. There are some differences between a (more or less) rigid raft on piles, a set of buried pipes with (more or less) flexible connections and a hyperstatic beam, but the basic principles of mechanics are similar in all these cases. Several very general conclusion are drawn. (a) Soil heterogeneity induces effects (differential settlements, bending moments, stresses and possible cracking) that cannot be predicted if homogeneity is assumed. (b) The magnitude of the induced stresses depends on three factors: the magnitude of the soil variability (i.e. its coefficient of variation); a soil–structure stiffness ratio (in some cases, where the mechanics are more complex, one can consider two stiffness ratios, as in buried pipes for example, when one has to account for the flexibility both of the pipes and of the connections); a soil–structure length ratio, which combines the soil fluctuation scale and a structural characteristic length (distance between supports, buried pipe length, etc). In all cases, a worst value, corresponding to the value leading (from a statistical point of view) to the (statistically) largest effects in the structure, can be found. The principal benefit of such an approach is to provide some new approaches for better considering phenomena such as the geometrical irregularities in the longitudinal profile of pavements or during the control of soil compaction of sewer trench filling. This kind of approach can also give experts new tools for better calibration of safety in soil–structure interaction problems, when the soil variability is an influential parameter. Some practical conclusions are drawn in this direction.

Rainfall-induced differential settlements of foundations on heterogeneous unsaturated soils

“…This is consistent with the tendency observed in previous stochastic studies of foundations on randomly heterogeneous saturated soils (e.g. Fenton & Griffiths, 2002Breysse et al, 2005). The fact that the P 50 attains its maximum value at an intermediate rather than an extreme value of Ł(˜p à 0 ) is also intuitive, as ä s should approach zero when Ł(˜p à 0 ) approaches either zero or infinity.…”

Probability Distribution for Mobilized Shear Strengths of Saturated Undrained Clays Modeled by 2-D Stationary Gaussian Random Field - A 1-D Stochastic Process View

“…The behaviors of the observed sample means and variances are fairly complicated. The phenomenon of the critical SOF reported in Fenton and Griffiths [3], Breysse et al [4], and Soubra et al [5] is observed for scenarios CI-SExp, SI-SExp, and CA-SExp  the sample means are minimal at   10m. This critical  is roughly equal to the width of the soil specimen, which is also roughly equal to the length of the slip curve.…”

“…Figure 9(a) shows the results for the four SExp scenarios, and Fig. 9 [4], and Soubra et al [5], where it is shown that more complex mechanisms can appear when the SOF is comparable to some multiple of the characteristic length of the structure (e.g., height of slope, diameter of tunnel, depth of excavation). Hence, spatial variability affects geotechnical analysis in a manner that is more fundamental than variance reduction.…”

“…It will be made clear that the developed probability distribution model is able to effectively capture the complicated behaviors of  f m . The model can also capture the phenomenon of the critical scale of fluctuation, which is observed in Fenton and Griffiths [3], Breysse et al [4], and Soubra et al [5].…”

Effect of soil–structure interaction on the reliability of reinforced concrete bridges

“…Elachachi et al [3,4] considered the effect of soil-structure interaction on embedded pipe networks. Studies on soil-structure interaction considering the effects of soil heterogeneity have been presented by Breysse et al [5]. The results showed the effect of soil variability on the induced forces in linear mechanical systems.…”