Nonlinear soil stiffness for analyzing ground movements in engineering practice

Soil stiffness is one of the most important parameters governing ground movements and the performance of many earth structures under working conditions such as retaining walls, pavements and railway embankments. In most construction activities in Hong Kong, ground movements should be controlled to a stringent limit to avoid damaging adjacent utilities and building structures. A proper understanding and calculation of soil stiffness are thus crucial in engineering practice. Furthermore, soil stiffness is affected by many factors (e.g. stress state and stress path) and reduces substantially with an increase in strain in a nonlinear manner. It is challenging to measure and model soil stiffness with good accuracy. In this presentation, the key characteristics of soil stiffness and deformation will be introduced. Then, some advanced experimental investigations on Hong Kong soils like completely decomposed tuff will be presented. Some simplified equations for calculating soil stiffness will also be introduced. Finally, engineering applications will be discussed using several examples including deep excavations and pavements.