Particle crushing and permeability evolution of saturated broken rock under compaction

In orderto study particle crushing and permeability evolution of saturated broken rock, lateral confined compression tests and seepage tests for saturated crushed rockhave been conducted. Micro-CT system has been used to observe the microstructure of the samples and relative breakage has been introduced to quantitatively study the destructive rules of particle crushing, and then the influence of relative breakage on porosity and permeability has been analyzed.The experimental results have indicated that during compaction, particle crushing is pervasive and continuously changes the particle size distribution of the samples. When the axial stress reaches 2 MPa, small particles (0-2.5 mm) appear in large numbers by 44.6% of total increase; meanwhile, the mass of large particles (12-15 mm) decreases significantly by 45.1% of the total decrease. However, after the axial stress exceeds 12 MPa, the mass of small particles (0-2.5 mm and 2.5-5 mm) changes slightly, and the mass of rock particles in other sizes changes weakly.The variation ranges of relative breakageand permeability are0-0.369 3 and 3.48×10-14-67.16×10-14 m2respectively, and the change process of both can be divided into two stages. When the axial stressis less than 4 MPa, the relative breakage increases rapidlyby 65.6%-74.1% of the total increase, and the permeabilitydecreases rapidlyby 84.4%-91.1% of the total decrease. When the axial stress is greater than 4 MPa, the relative breakage increases slowly and tends to be stable, while the permeability decreases slowly and tends to be stable. The relationship between permeability and relative breakage can be fitted by a quadratic polynomial function, which means that the relative breakage can be used as an effective parameter to evaluate the permeability of saturated crushed rock. The initial gradation has a significant impact on the permeability. Under the same axial stress, the larger Talbot exponent corresponds to a smaller permeability, while the initial gradation has little effect on the relative breakage. © 2020, Editorial Board of Journal of Mining & Safety Engineering. All right reserved.