Numerical Study of the Effect of Ground Improvement on Basal Heave Stability for Deep Excavations in Normally Consolidated Clays

Abstract

The ground-improvement technique is commonly used to restrain the wall displacement induced by excavation and resist the basal heave for deep excavations in soft clays. In this paper, a three-dimensional finite-element stability analysis was conducted to evaluate the effect of different ground-improvement properties and patterns on enhancing the factor of safety against basal heave in deep excavations. The results showed that a large downward movement of soil behind the wall could induce a large upward movement below the excavation, which is mainly resisted by the weight of the interior soil mass and the frictional resistance acting on the contact surface area between the wall and the soil inside the excavation. When the ground improvement was not contacted with the wall, the failure initially occurred on the wall interface, causing the soil inside the excavation to move upward along with the ground improvement, which resulted in an insignificant increase in the factor of safety. Hence, the ground improvement should be contacted to the wall to establish a higher basal heave resistance, where the increase of the safety factor was governed by the amount of the ground improvement that contacted the wall. Furthermore, a simplified method was proposed to calculate the factor of safety with and without ground improvement, which was validated by the results from the finite-element method.