Numerical Modelling of Dynamic Soil Liquefaction in Sloping Ground

In sloping ground, before application of dynamic loading, the ground is subjected to a static shear stress due to the weight of the soil and the slope of the ground. Static shear stresses will act as driving forces and cause very large ground deformations even before the onset of soil liquefaction. Therefore reliable prediction of soil response is essential in the assessment of remediation methods to reduce liquefaction induced soil deformation. This paper investigates the application of a stress path model to simulate the soil liquefaction in sloping ground. Pore pressure generation and liquefaction strength of the soil predicted by the numerical model are compared with a series of simple shear tests performed on loose sand with and without an initial static shear stress simulating sloping and level ground conditions, respectively. Numerical predictions are shown to be in good agreement with test data

Numerical simulation of pile group behaviour in liquefying sloping ground

This paper investigates pile group behaviour in liquefying sloping ground. The numerical procedure utilised involves two main steps. First a ground response analysis is carried out using a stress path model to obtain the maximum ground displacements along the pile and the degraded soil modulus over the depth of the soil deposit. Next a dynamic analysis is carried out for a single pile in the group assuming that each pile in the group behaves in the same way during the earthquake loading. The method has been verified using centrifuge data, where soil liquefaction has been observed in laterally spreading sloping ground. It is demonstrated that the new method gives good estimate of pile behaviour, despite its relative simplicity

Undrained bearing capacity of shallow foundations on structured soils

This paper examines the undrained bearing capacity of shallow circular foundations on structured soil deposits. Guidelines are given to identify the importance of structural features of the soil when assesing its bearing resistance. Results obtained using a finite element model have been compared with those from existing bearing capacity formulae based largely on plasticity theory. A new bearing capacity equation has been proposed incorporating critical state soil parameters and additional parameters that quantify the effects of soil structure on its mechanical behaviour

Behaviour of pile groups in liquefying soil

This paper presents a simplified method of analysis for pile groups founded in liquefying soil. The method involves two main steps. First an effective stress based ground response analysis is carried out to obtain the maximum ground displacements along the pile and the degraded soil modulus over the depth of soil deposit. Next a dynamic analysis is carried out for a single pile in the group assuming that each pile in the group behaves in the same way during the earthquake loading. The method has been verified using centrifuge data, where soil liquefaction has been observed in laterally spreading ground. It is demonstrated that the new method gives good estimate of pile behaviour, despite its relative simplicity

Numerical modelling of soft ground improved with cement

This paper examines the undrained bearing capacity of shallow circular foundations on soft ground improved with cement by using a numerical model based on the finite element method. Guidelines are given to identify the importance of the degree of cementation for assessing the bearing capacity of foundations. Using a bearing capacity improvement factor, influence of the extent of the cemented region on bearing capacity has been investigated. Finally the performance of deep mixed cement columns has been investigated using the numerical model. The results indicate that there exists an optimum length to diameter ratio for the deep mixed cement columns and this value depends on the degree of cementation of the soil

Modelling the behaviour of cemented clay

In this paper, a theoretical study of the behaviour of cemented soft clay is made using a simple predictive constitutive model, the Structured Cam Clay (SCC) model. A simple modification of the original SCC model is proposed so that important effects of cementation on soil behaviour can be represented. The revised model is evaluated based on the comparison of simulations and experimental data