An empirical statistical constitutive relationship for rock joint shearing considering scale effect

Advances in Civil Engineering

Zhu

Yang

et al. 2020

Self Cite

Bolts are widely used in rock mass engineering, wherein the bolt support improves the safety and stability of the rock mass. To reveal the mechanical behavior of the bolt and failure mechanism of the bolted joint in the shearing process, a direct shear test was conducted by changing the state of grouting, number of bolt, and inclination angle of the bolt. The change in the axial force of the anchor in the shearing process was evaluated by conducting a strain gauge test, and the mechanical behavior of the bolt under the external force was studied. The results showed that under the same normal stress, the yield displacement of the bolt decreased and the stiffness of the joint gradually increased with increased number of bolts. At the same number of bolts, their yield displacement increased with increased normal stress. Analysis further revealed that grouting on the joint improved the force condition of the bolt, increased the yield displacement of the bolt, and coordinated the deformation of the grouting body and bolt, thereby improving the shear strength of the joint. Lastly, when the anchor angles differed, the axial pulling resistance of the anchor changed, and the yield displacement of the anchor with 45° inclination was <90°. The yield displacement of the bolt showed that the supporting effect of the bolt with a 45° inclination was better than that of the bolt with a 90° inclination.

Section: Failure Mode Of Jointmentioning

confidence: 99%

Anchor Stress and Deformation of the Bolted Joint under Shearing

Advances in Civil Engineering

Zhu

Yang

et al. 2020

Self Cite

“…Figure 6 indicates that for the rocks with plastic-elastic deformation characteristics, under the condition of low shear stress, the deformation modulus of rocks in creep behavior increased with time, which is contrary to the deterioration of the mechanical properties of most rocks with time [50,51]. is result is due to the existence of many microcracks in plastic-elastic rocks [52,53]. Low shear stress cannot easily compact the microcracks inside the rock completely in a short time, and the microcracks that are not compacted continue to be compacted in the following creep behavior, thus showing a hardening effect.…”

Section: Mechanical Properties With Timementioning

confidence: 93%

Improved Nonlinear Nishihara Shear Creep Model with Variable Parameters for Rock‐Like Materials

Advances in Civil Engineering

Zhang

Wang

et al. 2020

Self Cite

Creep property is an important mechanical property of rocks. Given the complexity of rock masses, mechanical parameters change with time in the creep process. In this work, a nonlinear function for describing the time-dependent change of parameters was introduced and an improved variable-parameter nonlinear Nishihara shear creep model of rocks was established. By creating rock-like materials, the mechanical properties of rocks under the shear creep test condition were studied, and the deformation characteristics and long-term shear strength of rocks during creep were analyzed. The material parameters of the model were identified using the creep test results. Comparison of the model’s calculated values and experimental data indicated that the model can describe the creep characteristics of rocks well, thus proving the correctness and rationality of the improved model. During shear creep, the mechanical properties of rocks have an aging effect and show hardening characteristics under low shear stress. Furthermore, according to the fact that Gk of the nonlinear model can characterize the creep deformation resistance, a method to determine the long-term shear strength is proposed.

“…Particle size is mainly determined by minimum particle size (R min ) and particle size ratio (R max /R min ). It is necessary to consider the effect of particle size distribution (Ding et al, 2014;Lin et al, 2019b). On the premise of reasonably reflecting the sizes in granites and in order to improve the efficiency of the numerical calculation, a total of 46940 particles with particle sizes ranging from 1.5 to 2.49 mm were generated in the specimen.…”

Section: Numerical Modelmentioning

confidence: 99%

Analysis of Internal Stress Distribution and Mechanics Characteristics of Pre-existing Cavity in Brittle Rock Under Triaxial Cyclic Loading

Zhou

2020

Front. Earth Sci.

Self Cite

In order to reveal the internal stress distribution and failure characteristics of a preexisting cylindrical cavity in granite under triaxial cyclic loading, bonded particle models containing a cavity were established to investigate the variation in crack propagation, stress distribution, number of micro-cracks, elastic modulus, and Poisson's ratio with an increase in cavity diameter. The results show that the cavity diameter has a significant effect on the tensile cracks, compression-shear failure zone, and compressive stress distribution. The peak strength decreases as the diameter of the cavity increases. However, the number of cracks increases and the plastic deformation increases more obviously. With the increase of the cyclic axial stress, the decrease rate of the elastic modulus shows the rule of "first slow, fast later," and the Poisson's ratio increases. The distribution of local stress of σ 1 ,σ 2 , andσ 3 explains the behavior of the cracks around the cylindrical cavity well.