Experimental study on hydraulic fracture of gravelly soil core

The hydraulic fracture tests on two kinds of graded gravelly soils are carried out by using the improved triaxial apparatus. For the hydraulic fracture pressures on the gravelly soils, the soil properties and confining pressure are the key influence factors. The hydraulic failure mode of gravelly soils is always shown as breakdown. The flow capacity in the tests decreases with the increase of the confining pressure, consolidation ratio and injection pressure rate. The hydraulic fracture pressure increases with the fine particle content of the gravelly soils because of the self-cohesiveness. However, the effect on the fracture pressure with the increasing confining pressure is similar for different graded gravelly soils. The consolidation ratio or axial stress has the slight effect on the fracture pressures, and so does the hydraulic pressure rate.