Modelling of desiccation crack depths in clay soils

Desiccation cracking is a major problem in many fields. In addition to introducing speedy pathways for water ingress, cracks can also compromise the structural integrity of the geo structures. In this regard, prediction of the depth of cracking is an important aspect in evaluating system performance. Modelling of desiccation cracks is a major concern for the past few decades. Despite the numerous attempts to model the crack depths, no comprehensive modelling method is available. In this study, an attempt has been made to model the desiccation crack depths using analytical and numerical approaches. The thesis presents a review of the literature identifying the gaps of the knowledge in this field, numerical modelling of desiccation crack depths under various conditions for different soils and laboratory experimentation to support the numerical model. The existing theoretical methods used to analyse desiccation crack depths and new methods have been developed to describe the predictions from the numerical program. Further the cyclic change of climate conditions are considered for developing the numerical model. Finally a new approach is used to predict the crack depths in which moisture content change was used instead of suction. Finally a more rigorous approach of predicting crack depths incorporating cohesive properties at the crack is presented using the computer program UDEC. The results from the numerical approach are presented and discussed in the thesis. The crack depths are compared with either theoretical results or a bench-mark model, highlighting pros and cons of current approaches. More accurate crack depths agreeing with the published field observation data can be predicted when using the moisture content change instead of suction as a model parameter. Furthermore, cohesive properties of the crack should be considered for fracture modelling provided that soils are not subjected to extreme dry conditions. However, it is recommended to conduct comprehensive field experimentation to measure the desiccation crack depths and compare the results with the numerical modelling predictions of the same soil in same field conditions to draw fully validated conclusions.