Development and application of cavity expansion theory based on bounding surface and kinematic hardening plasticity

In this thesis, the undrained and drained spherical cavity expansions in clays are analysed according to a new viewpoint, in which this boundary problem is treated as the integration of stress-strain following cavity expansion load paths. The widely adopted substepping scheme numerical integration technique is used in developing the undrained and drained solution of cavity expansion problems based on the modified UH model and the original and modified two-surface bubble models. This bounding surface plasticity series model has been proved to have inherent advantages in capturing the overall soil behaviour for clays with different consolidation histories than the other critical state models under the classical plasticity framework, especially for predicting nonlinear soil response at the early stage of cavity expansion for a soil stress state initially located beneath the yield surface for previous consolidation. Since the embedded hardening law of the modified UH model and the original and modified two-surface bubble model are related to the degree of overconsolidation, the influence of consolidation history (OCR) on the expansion responses for spherical cavities in clays under both undrained and drained conditions can be fully demonstrated. In addition, the solution developed in this study will then be used to predict soil behaviour in the compaction grouting test and the pressuremeter test. The advantage of using this method over the conventional interpretation method for the results of the compaction grouting test and pressuremeter test is also outlined. Therefore, the newly developed solution can serve as a useful tool in many geotechnical engineering problems, such as interpreting the results of cone penetration tests, as well as predicting the excess pore-pressure generated during pile installation. Additionally, the solution system developed in this study can be used as a platform to develop the cavity expansion solution, based on another more sophisticated constitutive model, to consider effects such as creep and local consolidation.