Introduction

Soil behaviour is a function of its composition, structure and fabric and the properties of the pore fluid. The behaviour can change with time, changes to the environment and changes in external loads. Problematic soils do not conform to the ideal soil used in classical soil mechanics theories, which means that methods of design developed from classical soil mechanics theory are supplemented by further studies that are often not described in design codes and guidelines. Problematic soils can be dealt with through good practice by appreciating their formation and how they behave; undertaking sufficient and appropriate investigations to produce data to assemble the geological, engineering geological and geotechnical models; using appropriate constitutive models in the analysis of geotechnical structures that can consider soils that potentially can collapse suddenly, are highly compressible, can expand or shrink excessively or fail catastrophically; using a risk-based approach to assess susceptibility of the proposed structures to geological and geotechnical hazards and using design codes and guidelines as a framework to produce design solutions and ensure that the solutions address the hazards identified in the investigations.