Experimental Test Of Seepage And Fracture Propagation In Sandstone And Its Numerical Analysis

Fluid in the pore space sand cracks of rocks is closely related to the accelerated accumulation of slow slip and strain energy in earthquake rupture progress. Hence it is necessary to do research into nonlinear fluid-structure interaction mechanism in the progresses of earthquake and fault activity.Theoretical model is verified by conducting triaxial compression test with the sandstone in Sichuan Basin, The results can provide theoretical basis for identifying earthquake precursor information of pore pressure which has physical significance about centrum.Triaxial compression test is conducted using sandstone taken from Sichuan Basin. The state of stress and strain and influence of pore pressure and saturation on rock strength with the compression progress is studied by drying, injecting, increasing pore pressure and compression in axial.The results indicate that pore pressure and saturation will weaken the rock strength, making the breaking time shorter. The acoustic emission events are monitored using acoustic emission technology in laboratory to show the response of velocity and amplitude of P wave to compression.The rupture state with spatial and temporal distribution characteristic of acoustic emission events is described.A numerical simulation is carried out by using FLAC3D software. Explicit and implicit difference scheme are first derived using finite deference method with given governing equations. Time and spatial interval are the main influence on computational stability. Triaxial compression test on fully saturated sandstone are modeled using the data in the test above. The progress of axial compression is simulated. The results are compared with that of test on dry sandstone. Also the results indicate that pore pressure and saturation will both weaken rock strength. The rock kept being compressed until it is broken.An updated high-order accuracy CE/SE (space-time conservation element and solution element) method has been applied to numerically simulate the unsteady flows past a square cylinder using porous media. By comparing flows at different Darcy’s numbers and Reynolds numbers, the results indicate that the variation of parameters of flows past a square cylinder using porous media similar to the flow past an impermeable square cylinder; the range of pressure and lift coefficient decreased and vortex frequency increased while Reynolds number increased; the porosity and Darcy’s number were influence factors on vorticity contours. It was shown that the simulation results accorded with the realistic physic laws. The CE/SE method will be widely applied to the simulation of unsteady viscous flows in porous media in engineering.