Review of methods for predicting the hydraulic failure of a rockfill core dam

Introduction. The phenomenon of hydraulic fracture is associated with the failure of some earth-rock dams, in which the integrity of the core made of clay soil has been compromised. It is believed that hydraulic fracture occurs when the pressure of water contained in pores and microcracks overcomes the compressive stresses in the soil. At this point, several methods have been proposed for the computational prediction of hydraulic fracture. They are aimed at determining the conditions under which hydraulic fracture occurs and at determining the critical water pressure that causes fracture growth.Materials and methods. A review of foreign scientific publications was carried out to systematise information on methods and techniques for critical pressure determination.Results. The review gives a classification of methods for predicting hydraulic fracture. Theoretical methods are based on the usage of elasticity theory, plasticity theory or fracture mechanics. The simplest method is based on the analysis of the stress state of the soil mass. This review describes methods based on the analysis of the stress-strain state of soil around a cavity with internal pressure. They consider several mechanisms of crack propagation, including the loss of tensile and shear strength. Empirical formulas based on the results of laboratory experiments are also given. In the framework of the analytical review, a comparison of some methodologies has been carried out. Most of the methodologies agree that the critical pressure primarily depends on the minimum principal stress σ3 in the ground. The comparison showed that the critical pressure calculated by the theoretical triaxial stress analysis technique is noticeably lower than that calculated by the empirical techniques. In the presence of a cavity, the more likely cause of fracturing is the loss of shear strength of the soil rather than tensile strength.Conclusions. Despite the abundance of techniques for predicting hydraulic fracturing, no theoretically verified and accurate methodology has been established at the present time.

dam, hydraulic fracture, cracking, critical pore pressure, stress state