Design of Geotechnical Infrastructure Using the Mechanics of Unsaturated Soils

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Significant economic benefits can be achieved for Canada by designing geotechnical infrastructure based on the mechanics of unsaturated soils, taking account of the influence of suction. However, such design approaches are limited in conventional practice. This is because of the inherent complexity of mechanics of unsaturated soils theory, as well as the time-consuming experimental studies that need elaborate testing equipment and trained personnel. For these reasons, it is important to propose design approaches extending the mechanics of unsaturated soils that are simple for implementing in practice. To address this urgent need, the applicant, through this proposal, will focus on three research themes of significant interest. (i) Research Theme I: Design of pavements for highways and railways; Pavement design methods as per Mechanistic-Empirical Pavement Design Guide are categorized as Level 1, 2 or 3 to meet the various design standards required for pavements. Level 1 methods are expensive and cumbersome, and need elaborate testing facilities, while Level 3 methods are empirical in nature and have limitations. A two-step approach will be proposed as a Level 2 method for meeting the pavements design standards of Canada. This approach can also be applied for railways, taking into consideration the relevant load and design factors. (ii) Research Theme II: Estimation of the variation of heave and swelling pressure of expansive soil with respect to suction; Swelling pressure associated with expansive soils is influenced by soil suction reduction induced by wetting. Ground heave in both lateral and vertical directions has significant effect on the performance of geotechnical infrastructure due to the influence of swelling pressure. A simple technique will be proposed based on the conventional soil properties for estimation of swelling pressure and 1-D heave. Such a technique will be of interest because it can be used for reliable design of both shallow and deep foundations constructed with or within expansive soils. (iii) Research Theme III: The effect of swelling on the stability of slopes in expansive soils; The proposed research will develop a framework of numerical modeling tools to reliably design slopes in expansive soils, which is one of the most challenging geotechnical problems. This framework can also be extended with some modifications for other problematic soils, such as the sensitive clays of eastern Canada. The applicant’s long-term vision through this proposal is to contribute to the design of sustainable geotechnical infrastructure in unsaturated soils and other problematic soils such as expansive and sensitive soils of Canada. The goal is to provide simple, yet reliable, solutions that can be used to implement the mechanics of unsaturated soils in practice with a greater degree of confidence, and simultaneously contribute to the Canadian economy.