Probabilistic Investigation on Seismic Bearing Capacity of Shallow Foundation on Unsaturated Fly Ash Deposit

Abstract

Fly ash is a by-product of coal-based thermal power plants. Utilization of fly ash in geotechnical projects may provide a sustainable solution for its efficient disposal. In this regard, bearing capacity of fly ash deposits is of paramount importance for satisfactory performance of foundations built on these deposits. Fly ash deposits used for filling up of low-lying areas are often under unsaturated or partially saturated state, and therefore, incorporation of suction stress induced in fly ash due to the presence of matric suction becomes essential while estimating its bearing capacity. In this regard, unsaturated shear strength may be quantified using water retention characteristic curve (WRCC) fitting parameters. However, determination of WRCC parameters often involves various uncertainties arising mostly due to the limited number of test data, inherent limitation of measurement range of suction measuring instruments, etc. Furthermore, very limited studies are available in literature to address the problem of seismic bearing capacity of fly ash deposits under unsaturated framework. In the present study, probabilistic-based approach has been adopted to obtain the seismic bearing capacity of footing placed on fly ash deposit, incorporating the uncertainty of the random input parameters, by adopting a factorial design approach. Sensitivity of random variables, such as infiltration rate ratio (q/ks), WRCC fitting parameters of the fly ash and horizontal seismic acceleration coefficient (kh) on the seismic bearing capacity, is presented. A prediction model has also been developed considering variation of random input parameters.