Advanced Numerical Modelling of Deep Excavation Supporting System Using Contiguous Pile Wall-Paper

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The study compares the Mohr–Coulomb (MC) and Hardening Soil (HS) constitutive models for simulating a 26 m deep excavation supported by a contiguous pile wall. This system uses spaced piles, relying on soil arching between them, and is most suitable for cohesive ground with groundwater below excavation level.<br /><br />A three-dimensional PLAXIS model represents the Santiago, Chile, case study. The 0.8 m diameter piles, separated by 0.5 m gaps, are supported by three anchor levels. Excavation and anchor installation are simulated in 13 stages, and soil response is compared at points between adjacent piles.<br /><br />The MC model treats soil as linear elastic up to yielding, with constant stiffness. In contrast, the HS model captures nonlinear, inelastic soil behaviour, stress-dependent stiffness, plastic hardening, and unloading–reloading effects. The simulations show that excavation reduces lateral stress, and the HS model reflects the associated changes in soil stiffness; MC does not. MC also predicts unrealistic strain reversals and greater excavation-side heave. Its predictions are notably sensitive to Poisson’s ratio: changing the value from 0.2 to 0.4 doubles the calculated wall deflection.<br /><br />The authors conclude that the HS model better represents realistic soil behaviour and provides more reliable deformation estimates for contiguous pile-supported excavations than the commonly used MC model.

Keywords

Mohr-Coulomb model

Hardening Soil model

contiguous pile wall

deep excavation

PLAXIS 3D

soil arching

anchor levels

lateral wall deflection

stiffness degradation

ground deformation