Case histories of rock bursts under complicated geological conditions

We designed and manufactured several types of simulated faults with different-size rectangular zigzag gouges, and sheared them by traditional double-direct shear tests. Simultaneously, the shear force and corresponding acoustic emissions were recorded during shear-slip of rectangular zigzag gouge, and the variations of shear force and acoustic emission energy characteristics related to shear-slip events were analyzed. Especially, the relationship between shear-slip characteristics and zigzag length and width was also revealed. In addition, the significant differences of slip characteristic parameters between shear-slip of an intact zigzag and friction and sliding on rough plane of a sheared zigzag were summarized, and it might be used to judge the different stages of a fault slip with zigzag gouge. In conclusion, this work may reveal the characteristics of shear-slip and friction under conditions of different-size rectangular zigzag gouges of simulated fault and thus provide valuable insights into precursors of earthquake.

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“…Simultaneously, the work may provide some explanations for rockbursts induced by geological structure instability. 29 …”

Section: Discussionmentioning

confidence: 99%

Research on shear-slip characteristics with different-size rectangular zigzag gouge by double-direct tests

Liu

Zhao

2017

International Journal of Distributed Sensor Networks

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“…For 3 = 10m and c4 =2 m, the inflection point location of support pressure curve of coal seam 4 = 8 m can be obtained using (9). Suppose c3 = 11MN/m, with respect to 2 = 7MN/m and c3 =8.6, 8.3, and 8 m 2 = 7MN/m and according to (5), (7), and (10), the support pressure curve 4 ( ) (x is the [8,10] m section) for the hardened zone of coal seam when 4 =8 m and c4 =2 m and the support pressure curve 3 ( ) (x is the [10,18] m section) for the softened zone of coal seam when 3 = 10m and c3 =8.6, 8.3, and 8 m were plotted by Matlab, as shown by curves 1, 2, and 3 in Figure 7.…”

Section: Expressions Of Support Pressures In Softened and Hardenedmentioning

confidence: 99%

“…For a hard roof with advanced fracture, when the working face advances to below the roof fracture line, if the supporting resistance of frame and friction between seams are insufficient, the roof easily subsides in a stepped style, causing collapse accidents under pressure and even rock burst disasters. Many studies have been conducted on the deformation, law of motion, and fracture of a hard roof under the overlying load by field observation, similar material simulation, numerical simulation, and theoretical analysis [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Qian et al [15,16], Miao et al [17], and Li et al [18] analyzed a hard roof by assuming the support pressure relationship between coal seam and immediate roof as an elastic foundation and obtained some basic results such as the deflection solution for a hard roof and the maximum bending moment in the front of a coal wall and for an advanced roof fracture.…”

Section: Introductionmentioning

confidence: 99%

Bending Moment Characteristics of Hard Roof before First Breaking of Roof Beam Considering Coal Seam Hardening

Jiang

Pan

et al. 2018

Shock and Vibration

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The mechanical properties of a coal seam affect the distribution of support pressure. Considering the strain hardening effect of coal seam, the support pressure relationship of three zones-softened, hardened, and elastic-of a coal seam with regard to a hard roof is proposed, and methods to determine an approximate expression for the support pressure of hardened zone of coal seam, the range of hardened zone, and the corresponding peak values of support pressure are provided. The deflection equations of a hard roof under three different support pressure relationships of coal seam before the first breaking were theoretically derived, and all the relevant integration constants were determined. Numerical examples of two cases are provided for calculating the bending moment of a hard roof and the support pressure of a coal seam. The analysis shows that as the working face advances, the maximum support pressure increases, the residual strength of coal seam at coal wall decreases, the overall deflection of roof gradually increases, the maximum bending moment of roof in the front of coal wall increases, and the advanced distance of roof bending moment peak gradually increases. As the depth of softened zone of coal seam increases, the similar conclusion is obtained, and the advanced distance of the roof bending moment peak increases at a relatively fast speed. Because the bending moment peak of hard roof is located near the support pressure peak in the softened zone of coal seam, the depth of softened zone of coal seam significantly affects the advanced distance of the bending moment peak of a roof. The actual advanced fracture distances of hard roof are distributed in a relatively broad range. The results indicate that there is a "large and long" type advanced fracture distance occurring in the actual stope. With the same overlying load and stope parameter conditions, the maximum support pressures of support roof in softened, hardened, and elastic zones considering a hardened coal seam are smaller than those in softened and elastic zones without hardening. However, the plumpness in front of the peak of the former support pressure curve is superior to that of the latter, and both the bending moment peak value and the advanced distance of bending moment peak of the former are higher than those of the latter.

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“…Thus, mechanical models need to be established that can sufficiently reflect the anisotropic characteristics of layered rocks and thoroughly explain their transversely isotropic deformation and failure characteristics . These models should be based on the mechanical properties and field monitoring information of the layered rocks to improve the accuracy of the calculations of the deformation and failure of the deep surrounding layered rocks and ensure the safety and stability of deep underground structures …”

Section: Introductionmentioning

confidence: 99%

Anisotropic modeling of layered rocks incorporating planes of weakness and volumetric stress

Tan

Zhou

et al. 2019

Energy Science & Engineering

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Layered rocks exhibit notable transverse isotropy and have a significant impact on the deformation and failure characteristics of underground structures. To a large extent, the mechanical properties of layered rocks are related to the structure and stress state of their bedding planes. To obtain an in‐depth understanding of the deformation and yield characteristics of layered rocks, a mechanical model for layered rocks incorporating planes of weakness and volumetric stress is proposed by improving the strain‐hardening/softening ubiquitous‐joint model based on continuum mechanics methods. In this mechanical model, elastoplastic equations for the matrix and bedding planes of layered rocks are established. The evolution of the mechanical parameters of the matrix and bedding planes of layered rocks with the internal variable is determined. In addition, the sensitivity of the model parameters is analyzed, and a method for determining the parameters is provided to reduce the complexity in obtaining these parameters. The numerical calculation results for the laboratory tests on layered sandstone specimens under various stress levels agree relatively well with the test results, thereby validating the effectiveness of the improved model. The methods and results of this study provide a significant reference for the analysis of the deformation and failure of other layered rocks.

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Case histories of rock bursts under complicated geological conditions

Cited by 112 publications

References 8 publications

Research on shear-slip characteristics with different-size rectangular zigzag gouge by double-direct tests

Research on shear-slip characteristics with different-size rectangular zigzag gouge by double-direct tests

Bending Moment Characteristics of Hard Roof before First Breaking of Roof Beam Considering Coal Seam Hardening

Anisotropic modeling of layered rocks incorporating planes of weakness and volumetric stress

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