Effects of water content on fracture and mechanical behavior of sandstone with a low clay mineral content

Zhou, Zilong; Cai, Xun; Ma, Dan; Cao, Wenzhuo; Chen, Lu; Zhou, Jing

doi:10.1016/j.engfracmech.2018.02.028

Cited by 199 publications

(80 citation statements)

References 60 publications

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“…Curves 1, 2, and 3 in Figure 16 show the support pressure curves of the softened, hardened, and elastic zones when the depth of the softened zone of coal seam is ( − 3 ) = 7.5, 8, 8.5 m, based on the c3 values of (87) and (5), (7), (14), and (15). Figure 16 shows that as the depth of the softened zone ( − 3 ) (the range denoted by green lines) increases, the peak values c3 of the curves increase, while the residual strengths of coal 3 ( ) at the coal wall gradually decrease, among which the residual strength of curve 3 is 3 ( ) → 0.…”

Section: Numerical Examples Of Bending Moment Of Roof As Depth Of Sofmentioning

confidence: 99%

“…The minus symbols ahead of 4 , 3 , and in (26c), (26d), and (26e) By satisfying (26a), (26b), (26c), (26d), (26e), (26f), and (26g) for boundary and continuity conditions, 14 integral constants in (14), (15), (20), (21), (24), and (25) can be determined. Owing to the introduction of the hardened zone of coal seam, one more equation was added to the deflection equations of rock beam compared with literature [20], i.e., in (20), two more integral constants, 1 and 2 , were added, and the continuity condition (26c) was added in (26a), (26b), (26c), (26d), (26e), (26f), and (26g).…”

Section: Boundary and Continuity Conditions For Deflection Of Rock Bementioning

confidence: 99%

“…Then, using (34) and (33), 2 and 4 can be determined. All these finally determine the deflection (14) and (15) …”

Section: Determination Of Integral Constants In Deflection Equationsmentioning

confidence: 99%

“…Curves 1, 2, and 3 in Figure 10 show the support pressure curves of softened, hardened, and elastic zones of coal seam when the working face advances or the hanging roof distance of goaf increases. They were plotted according to c3 values in (84) and (5), (7), (14), and (15). To compare with the support pressures in Figures 1 and 2, the positive direction of support pressure of coal seam is shown upward in the chart.…”

Section: Support Pressure Of Coal Seam As Hanging Roof Distancementioning

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%

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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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Section: Numerical Examples Of Bending Moment Of Roof As Depth Of Sofmentioning

confidence: 99%

Section: Boundary and Continuity Conditions For Deflection Of Rock Bementioning

confidence: 99%

“…Then, using (34) and (33), 2 and 4 can be determined. All these finally determine the deflection (14) and (15) …”

Section: Determination Of Integral Constants In Deflection Equationsmentioning

confidence: 99%

Section: Support Pressure Of Coal Seam As Hanging Roof Distancementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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Surficial fractures in the Navajo sandstone, south‐western USA: the roles of thermal cycles, rainstorms, granular disintegration, and iterative cracking

Loope

Burberry

et al. 2020

Earth Surf Processes Landf

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Deep (> 5 m) sheeting fractures in the Navajo sandstone are evident at numerous sites in southern Utah and derive from tectonic stresses. Strong diurnal thermal cycles are, however, the likely triggers for shallow (< 0.3 m) sheeting fractures. Data from subsurface thermal sensors reveal that large temperature differences between sensors at 2 and 15 cm depth on clear summer afternoons are as great as those that trigger sheeting fractures in exposed California granite. Extensive polygonal patterns in the Navajo sandstone are composed of surface-perpendicular fractures and were produced by contractile stresses. Numerous studies have shown that porewater diminishes the tensile strength of sandstone. Based on our thermal records, we propose that cooling during monsoonal rainstorms triggers polygonal fracturing of temporarily weakened rock. On steep outcrops, polygonal patterns are rectilinear and orthogonal, with T-vertices. Lower-angle slopes host hexagonal patterns (defined by the dominance of Y-vertices). Intermediate patterns with rectangles and hexagons of similar scale are common. We posit that outcropping fractures are 1 digitalcommons.unl.edu

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Water–Rock Interactions in Rock Fractures

Zhao

2023

Coupled Thermo-Hydro-Mechanical-Chemical Processes in Fractured Rocks

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Effects of water content on fracture and mechanical behavior of sandstone with a low clay mineral content

Cited by 199 publications

References 60 publications

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

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

Surficial fractures in the Navajo sandstone, south‐western USA: the roles of thermal cycles, rainstorms, granular disintegration, and iterative cracking

Water–Rock Interactions in Rock Fractures

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