MECHANISM OF HYDRAULIC FRACTURING IN COHESIVE ZONE OF EMBANKMENT DAM CORES - A REVIEW

Hydraulic fracturing can occur in theoretical homogeneous embankment, but the probability of its occurrence is higher if the material is not homogeneous with respect to deformability and permeability (Sherard, 1973). According to BertilLofquist(1992), hydraulic fracturing is an effect that may occur in different connection. He means that when liquid pressure is lower than the counter pressure in the surrounding soil, rocks or materials, it experiences a fracturing effects.In case of embankment dam engineering, due to complexity of problem, it has been questioned whether concentrated leaks traversing a dam or dam core can develop as a result of hydro facture. The difficulty with hydraulic fracturing is that the cracks of fractures are hidden from direct observations as it happens inside the dams. Although the fact is unknown, some great experiments and observations demonstrated by Sherard (1973, 1986) and Penman (1982, 1986, and 1991) support the possibility that the hydraulic fracturing is often an active mechanism in the development of concentrated leakage.The occurrence of loose and wet layers, wet joints, in earth cores provide the evidences but the matter is still a controversial. According to Lofquist 1992, hydraulic fracturing occur in dam with existence of special condition.One condition is that the risk of hydraulic fracturing can only takes place if the reservoir pressure in the dam is higher than the total horizontal or vertical pressure at same level. But there should be another condition for hydraulic fracturing to occur