Abstract
Roadway excavation changes the original equilibrium stress state of the rock mass, resulting in the loading and unloading of the surrounding rock near the free surface. After the excavation, the tangential stress increases and the radial stress decreases, which mainly cause deformation and collapse of the roadway. In order to study the strength characteristics of the surrounding rock after the excavation, one effective way is to carry out triaxial compression tests on small surrounding rock samples. Therefore, this paper focuses on the triaxial compression mechanical propertiesof thick‐walled cylinder granites with an electrohydraulic, servo‐controlled rock mechanics testing system (MTS‐815). It studies how different pore sizes and confining pressures affect the triaxial compressive strength (TCS), deformation, and failure modes of granite samples. The results are as follows: (1) Under triaxial compression, the stress‐strain curves have no obvious yield stage, and the peak TCS increases with the confining pressure (σ3). When σ3 is low, there is little difference in the TCS between the complete specimen and the thick‐walled cylinders. When σ3 reaches 30 MPa∼40 MPa, the TCS of samples with apertures of 15 mm and 20 mm are obviously lower. The σ3 has an obvious influence on the elastic modulus of thick‐walled cylinder granites. (2) Shearing and splitting are the main failure modes under triaxial compression. When σ3 is low, shear failure appears. As σ3 reaches 30 MPa∼40 MPa, split failure occurs. The area of the fracture surface increases with σ3. (3) As σ3 grows, the influence parameter (m) of the three‐dimensional Hoek‐Brown criterion increases. Under the same σ3, the value of m presents a decreasing trend from the outer wall to the inner wall, which means the bearing capacity keeps getting lower and lower. As a result, the inner wall is most likely to be damaged. The theoretical analysis results agree well with the tests.
Highlights
With a scale-up in the sustainable development of the economy and the infrastructure, underground projects, such as tunnel, mine, water conservancy, and hydropower, advance much deeper [1, 2]. e rocks surrounding the deep excavation are vulnerable to violent rock bursts, continuous deformation, large volume collapse, and other disasters, which lead to various accidents and casualties [3,4,5,6,7,8]
Wang et al [40] carried out triaxial compression tests on thick-walled cylinder granite specimens with an electrohydraulic, servo-controlled rock mechanics testing system (MTS-815). rough the tests, they determined the strength characteristics under the coupling action of internal and external stresses. en, they made a physical simulation on the actual rock mass around the circular pole and analyzed the test results in detail
Stress Analysis on ick-Walled Cylinder. e stress states of thick-walled cylinder granite specimens under triaxial compression are changed by their pores
Summary
With a scale-up in the sustainable development of the economy and the infrastructure, underground projects, such as tunnel, mine, water conservancy, and hydropower, advance much deeper [1, 2]. e rocks surrounding the deep excavation are vulnerable to violent rock bursts, continuous deformation, large volume collapse, and other disasters, which lead to various accidents and casualties [3,4,5,6,7,8]. By carrying out triaxial compression tests on standard cylinder specimens under three different stress paths, Zhang et al [25] discussed how the unloading and loading influenced the strength, deformation, and acoustic emission characteristics of rocks. E triaxial compression tests on thick-walled cylinders are widely used in complex stress distribution scenarios to study the deformation, strength, and fractured characteristics of rocks. With conventional triaxial compression tests, Yang [32] studied the deformation, strength, and damage of thick-walled cylinder sandstones under different confining pressures. En, they made a physical simulation on the actual rock mass around the circular pole and analyzed the test results in detail To be specific, they studied how the radial stress gradient, the peripheral stress, and the lengthdiameter ratio can affect the compressive strength and failure modes. Based on the three-dimensional Hoek-Brown criterion [49], it studies the relationship between the parameter and the failure degree. is work can provide both theoretical and experimental bases of the destabilization on the rocks surrounding the deep roadway
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