Quickness of sensitive clays

Sensitive clays are often presented as materials that become semi-liquid when subjected to remoulding. Consequently, such clays are considered to constitute a major threat to nearby infrastructures due to their susceptibility to flow slides. However, the term ‘sensitive clay’ encompasses a wide range of clays depicting significant variations in engineering behaviours such as the remoulded shear strength (c_ur). Therefore, a key question is whether all sensitive clays have the same potential to create flow slide and the significance of c_ur for occurrence of flow slide. The authors believe that one of the major challenges related to understanding the c_ur of sensitive clays is physical understanding of the parameter itself. This paper presents a laboratory procedure, referred to as a quickness test, which provides a quantitative description of remoulded behaviour of sensitive clays in terms of a numerical value called quickness (Q). The quickness test was used to demonstrate why sensitive clays with c_ur > 1·0 kPa are not susceptible to flow slides after an initial slide. Based on this preliminary study, it is possible to state that a Q < 15% or c_ur > 1·0 kPa seems to be the threshold limit where the extent of slide is limited to the initial slide.