Development of an empirical criterion for predicting the hydraulic fracturing in the core of earth dams

In this research, based on the laboratory studies, a new empirical criterion was developed to predict the hydraulic fracturing pressure in the core of earth dams. To simulate the core condition in the laboratory, a special cell was designed and assembled based on advanced consolidation cell (Rowe cell). The hydraulic fracturing tests were performed in unconsolidated and unsaturated conditions on the materials of an under-construction dam and the results were used according to critical conditions in which the hydraulic fracturing is initiated in the embankment dams. It can be concluded that for fine-grained soils and also coarse-grained soils containing considerable percent of fine particle, the hydraulic fracturing initiation pressure is dependent on the minor principal stress of the soil and increase linearly with the increase in mentioned stress. In addition, an empirical equation is introduced to estimate the hydraulic fracturing initiation pressure based on shear-strength properties of the soil, and also the effect of compaction energy on the pressure is discussed. Afterward, the numerical analysis has been carried out on the Madani Earth dam considering three types of soil for the core of the dam. Furthermore, by using several empirical criteria, the districts of the core which are susceptible to hydraulic fracturing were identified for each soil. Results of numerical study show that among three selected soils for the core of the dam, the CL which is susceptible to hydraulic fracturing is identified as critical soil and the GM-GC as the recommended one.