Numerical Simulation For The Whole Process And Study On Influencing Factors Of Hydraulic Fracturing In Clay

Hydraulic fracturing in earth core rockfill dam is a key problem which is unsolved and is given an universal attention in engineering field. Because of the complication of hydraulic fracturing, the whole process is quit unclear until now and there aren't any relevant reports that concern the complete simulation of hydraulic fracturing process. Based on the review of former researchers, hydraulic fracturing test and test of axial compressive fracturing are carried out. According to the criteria suggested by Seed and Duncan, generation and development processes of hydraulic fracturing in clay are simulated and analyzed using modified RFPA program. Meanwhile, influencing factors of hydraulic fracturing are investigated. The conclusions obtained in the paper are listed as follows:Firstly, results of hydraulic fracturing test indicate that hydrofracture face is controlled by the minor principal stress. As minor principal stress increases, hydrofracture pressure turns great. Hydraulic fracturing failure probably occurs when the size of the hole diameter adds.Secondly, the test using axial compressive fracturing method disclosures that the relation between tensile strength and water content of clay is quite close. When dry density keeps constant, tensile strength arrives peak value with increasing of the water content. Moreover, tensile strength gradually reduces because of the further increasing of water content. When water content keeps constant, tensile strength of clay gets great as dry density raises.Thirdly, the hydraulic fracturing process of open pore sample contains stages of stress accumulation and instant failure. The numerical results indicate that hydraulic failure is a short-term process and it's difficult to be catch by current means. Hydraulic fracturing theories based on RFPA are the preliminary exploration for the failure process studies. And the comparison between numerical simulation results and test of open pore samples illustrates that the theories are feasible.Fourthly, the hydraulic fracturing process of open crack sample includes threes stages, that is stress accumulation stage and crack expansion stage as well as instant failure stage. Simulation results of open crack sample further illustrate that hydraulic failure is an instant process. Asymmetry pore water pressure field influences the crack...