Abstract
Energy conversion and release occur through the entire deformation and failure process in jointed rock masses, and the accumulation and dissipation of rock mass energy in engineering can reveal the entire process of deformation and instability. This study uses PFC2D to carry out numerical simulation tests on single‐joint sandstone under uniaxial compression and biaxial compression, respectively, and analyse the influence of joint inclination, length, and confining pressure on the meso‐energy conversion process and phase evolution of jointed sandstone. Through analysis, it is found that the input meso total strain energy is transformed into meso dissipated energy and meso‐elastic strain energy. Macroscopic and microscopic joint sandstone law is consistent with the overall energy evolution; and the difference is reflected in two aspects: (1) the microlevel energy evolution has no initial compaction energy consumption section and (2) the linear energy storage section before the macroenergy evolution peak can be subdivided into two sections in the meso‐level energy evolution. Under uniaxial compression, the energy values at the characteristic points of the meso‐level energy evolution phases first asymmetrically decrease and then increase with the increase of the joint inclination. The initiation point of jointed sandstone is significantly affected by the length of the joint, and the degradation effect of the meso‐energy at the damage point and peak point weakens with the increase of the joint length. Comparing the data obtained from the PFC numerical simulation with the experimental data, it is found that the error is small, which shows the feasibility of the numerical model in this paper. Under biaxial compression, the accumulation rate of meso‐elastic strain at the peak point of the jointed sandstone first decreases and then increases with the joint inclination angle. After the peak of jointed sandstone, the rate of sudden change of meso‐energy change decreases with the increase of joint length. The conditions of high confining pressure will promote the meso‐accumulated damage degree of the jointed sandstone before the peak, while inhibiting the meso‐energy and the mutation degree of the damage after the peak. The higher the confining pressure, the more obvious the joint length and inclination effect characteristics of the elastic strain energy at the peak point of the jointed sandstone.
Highlights
Energy conversion and release occur through the entire deformation and failure process in jointed rock masses, and the accumulation and dissipation of rock mass energy in engineering can reveal the entire process of deformation and instability. is study uses PFC2D to carry out numerical simulation tests on single-joint sandstone under uniaxial compression and biaxial compression, respectively, and analyse the influence of joint inclination, length, and confining pressure on the meso-energy conversion process and phase evolution of jointed sandstone. rough analysis, it is found that the input meso total strain energy is transformed into meso dissipated energy and meso-elastic strain energy
The energy values at the characteristic points of the meso-level energy evolution phases first asymmetrically decrease and increase with the increase of the joint inclination. e initiation point of jointed sandstone is significantly affected by the length of the joint, and the degradation effect of the meso-energy at the damage point and peak point weakens with the increase of the joint length
With the gradual deepening of the rock energy evolution process, it has been found that numerical simulations can provide significant advantages, such as repeatability, real-time results, economic benefits, and operability. rough the damage caused by the contact between particles, the morphological evolution and crack propagation evolution of the specimen can be accurately captured throughout the entire process, and the fracture mechanism of the medium can be deeply revealed. erefore, the particle flow method has gradually been applied to the study of basic mechanical properties and fracture characteristics of rock materials [21,22,23,24,25]
Summary
A rock sample was obtained from a fresh and complete sandstone block located on a rocky slope on the bank of the ree Gorges Reservoir. e selected sandstone is hard and grey in texture, and it has a fine-grained sand-like structure and massive structure. When producing samples with different joint dip angles, the joint length, 2a, is 1 cm. E processed jointed sandstone samples with different joint dip angles are shown in Figure 1(a); when samples with different joint lengths are produced, the dip, α, is 45°. In the formula, P is the failure load, D is the diameter of the sample, t is the thickness of the sample, and σt is the tensile strength of the rock. According to the results of the Brazilian split test (the ultimate load is 9.343 kN), the tensile strength of the rock sample can be calculated using the formula to be 4.761 MPa (Figure 3)
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