Stability Charts for Limiting Horizontal Normal Pressure on Cohesive-frictional Backfill for Deep Contiguous Piled Walls

Background

This study presents a numerical solution for determining the limiting uniform normal pressure acting horizontally behind cohesive-frictional backfill material in a deep contiguous piled wall. At this limiting pressure, the soil tends to flow out in gaps between a series of vertical piles placed at a certain uniform horizontal spacing.

Methods

The lower and upper bound plane strain finite element limit analysis (FELA) has been carried out for this purpose. The Mohr-Coulomb failure criterion, using an associated flow rule, was employed to impose the yield condition in the soil mass.

Results

A parametric study was carried out to obtain the magnitude of the non-dimensional limiting lateral resistance (F/cD) as a function of normalized pile spacing (S/D), the friction angle of soils (ϕ), and the adhesion factor (δ) at the soil-pile interface; here, Frefers to the lateral normal resistance (force) per unit length offered by the pile, Sforms the clear spacing between piles, Dis the diameter of the pile and cis soil cohesion. The impact of the different parameters on the failure mechanisms has been examined comprehensively.

Conclusion

The lateral resistance (F/cD) offered by the piles increases generally with a decrease in the spacing between the piles. The magnitude of F/cDincreases further with an increase in the values of ϕand δ.

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