Tensile properties of cement-stabilised clays and their contribution to seawall design

Deep cement mixing is a typical ground improvement technique, and has recently been introduced in some large-scale reclamation projects in Hong Kong. There is a lack of internationally recognised testing standard for determining the tensile strength of cement-stabilised soil. In this study, tensile properties of cement-stabilised clays have been investigated using direct tension test and Brazilian test. The interpretation of tensile strength in Brazilian test is not straightforward due to the formation of multiple cracks during loading. As such, focus is placed on the validation of the fundamental assumption on crack initiation mechanism. A consolidated database of tensile strengths of cement-stabilised soils is compiled. A constitutive model in the finite-element program Plaxis, namely concrete model, has been studied. This model, originally aiming to simulate the behaviour of concrete and shotcrete, duly considers the cracking and the strain-softening characteristics, and is able to reasonably simulate the fundamental tensile behaviour of cement-stabilised soil. Numerical simulations have been carried out using the concrete model to assess the stability of seawall founded on cement-stabilised clay. Tensile properties are found to have an important bearing in maintaining the stability of the seawall when column-pattern stabilisation is adopted.