Permeability Characteristic and Failure Behavior of Filled Cracked Rock in the Triaxial Seepage Experiment

Abstract

Filling is commonly found in natural cracked rock mass. As the weakest part of the rock, the filling properties directly affect the rock deformation and strength, permeability, and so on and affect the safety and stability of the rock mass engineering. In this study, a single slit has been preset in sandstones and filled with different physical properties materials. Based on the laboratory triaxial seepage test, the permeability and strength characteristics of filled cracked sandstones are analyzed, and the failure modes are obtained. The main findings of this study are as follows: (1) The permeability coefficient peak value of the filled cracked rock appears before the stress peak. (2) At the same confining pressure growth rate, the peak stress growth rate of the filled cracked rock is generally higher than that of the intact rock and the strength growth rate of the cracked rock increases with the length of the fracture. The strength characteristics of the filling in the uniaxial compression tests and triaxial seepage tests are significantly affected by the hydraulic properties. (3) The strength and permeability coefficients of cracked rock filled with cement mortar are more sensitive to the change of confining pressure, while under the same condition, the ones of cracked rock filled with gypsum mortar are stable. (4) According to the failure mechanism, under the seepage stress, the secondary cracks can be divided into 3 types and the failure modes can be divided into 2 types.

Experimental Study on Seepage Anisotropy of a Hexagonal Columnar Jointed Rock Mass

“…erefore, it is feasible and effective to conduct indoor seepage-stress coupling tests on rock samples to explore the seepage characteristics under stress. Liu et al investigated the nonlinear flow characteristics of a fluid at the fracture intersection using an indoor permeability test; they established a fracture network model to simulate the fluid flow state and analyze the influence of the equivalent hydraulic gap width and hydraulic gradient on the nonlinear seepage characteristics [20]; Liu and Li analyzed the relationship between water permeability and sand particle size using a self-designed seepage circuit [21]; Xia et al studied the nonlinear seepage characteristics of a single joint surface with different roughness values using an indoor shear seepage test [22,23]; Liu et al performed conventional indoor triaxial seepage tests on fractured sandstone and analyzed its permeability characteristics [24]; Chao carried out a conventional triaxial cyclic loading and unloading seepage test on a similar material model of a columnar jointed rock mass with inert gas as the measuring medium to determine the relationship between permeability and confining pressure [25]. Few reports were published on the seepage characteristics of multijointed rock masses, especially columnar jointed rock masses.…”

Permeability of Sand-Based Cemented Backfill under Different Stress Conditions: Effects of Confining and Axial Pressures

“…Many studies have been conducted worldwide regarding SBCB permeability. Thus, Liu et al [26] performed indoor triaxial seepage tests and analyzed the cracked backfill's permeability and strength features. They obtained the failure mode of the cracked sandstone backfill.…”

Seepage Flow Properties of a Columnar Jointed Rock Mass in a True Triaxial Experiment

“…The results showed that the Forchheimer coefficient was affected by the roughness to a certain extent, and a semiempirical Forchheimer equation considering the fracture aperture and roughness was derived. Liu et al [34] performed conventional indoor triaxial seepage tests on fractured sandstone and analyzed its permeability characteristics. Liu et al [35] conducted a seepage experiment on Jurassic weakly cemented sandstone and analyzed its permeability during seepage.…”