Abstract
To study the influence of slenderness ratio effect on the mechanical behavior, acoustic emission properties, and energy evolution of sandstone, the uniaxial compression tests coupled with acoustic emission technology are carried out at different slenderness ratios D (0.5, 1.0, 1.5, 2.0, 3.0). The results show that a logarithmic function relationship is observed between the peak strength, the peak strain, and the elastic modulus with slenderness ratio. The failure patterns of the tested sandstone varied significantly with the increasing slenderness ratio. When the slenderness ratio, D, is lower than 1.5, complex failures and multiple shear planes are formed, while simple failures and single shear planes are generated at D larger than 1.5. Besides, the AE ringing counts are more obvious with a higher slenderness ratio, D, at the initial compression stage due to the greater body volume and more defects in the sandstone. The energy evolution curves and energy ratio distribution curves can be divided into four stages, corresponding to the stress‐strain curves.
Highlights
Most underground engineering, such as underground deposit mining, geothermal exploitation, nuclear waste storage, oil boreholes, and tunnel excavation, is highly dependent on proper knowledge of the strength and deformability parameters of rocks [1,2,3,4]. e design and stability evolution of such structures requires a deep insight into the strength and deformation behaviors of these rock materials
Sandstone sampled from Zigong, Sichuan province of China, was used. e mercury intrusion porosimetry test showed that porosity is 5.8%. e P- and S-wave velocities of the sandstone are 2950 m/s and 2072 m/s, respectively, which indicated the sandstone significant anisotropy inducing the different mechanical characteristics. e X-ray diffraction analysis implied that the mineral components mainly consist of quartz (58%), feldspar (15), and clay (11%), and the content of brittle minerals is more than half. e microscopic structure of the tested sandstone based on scanning electron microscopic (SEM) is shown in Figure 1, showing that the grains are randomly distributed; micropores and microcracks are observed among the grains, which may lead to less strength under the uniaxial compression tests
In the initial compression stage, the stress-strain curve presents initially concave up, which is possibly due to the closure of the pore-fracture system such as pores, preexisting microcracks, and defects in the specimens
Summary
Most underground engineering, such as underground deposit mining, geothermal exploitation, nuclear waste storage, oil boreholes, and tunnel excavation, is highly dependent on proper knowledge of the strength and deformability parameters of rocks [1,2,3,4]. e design and stability evolution of such structures requires a deep insight into the strength and deformation behaviors of these rock materials. Other researchers find that the specimen geometry on soft rock is generally not significant, and the correlation of uniaxial compression strength values in different diameters with estimations of specimen size effect models was weak [19]. A series of uniaxial compression tests coupled with acoustic emission technology have been designed and performed at different slenderness ratios D (D 0.5, 1.0, 1.5, 2.0, 3.0 with the constant diameter of about 50 mm) to explore the mechanical behavior and energy evolution of sandstone considering slenderness ratio effect. Is study provided new insights into the mechanical behavior and energy evolution of sandstone with different slenderness ratios, and it has the potential to obtain reliable rock parameters for the underground engineering design and construction E changes and the relationship between peak strength, the peak stain, the elastic modulus, and the slenderness ratio were documented and analyzed. e failure patterns and the energy characteristics were investigated in detail. is study provided new insights into the mechanical behavior and energy evolution of sandstone with different slenderness ratios, and it has the potential to obtain reliable rock parameters for the underground engineering design and construction
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