The effects of the rotational speed of voussoir beam structures formed by key strata on the ground pressure of stopes

In Fucun Coal Mine, the average spacing between the 3upper coal seam (UCS) and 3lower coal seam (LCS) is only 6 m. In the process of mining upper coal, the lower roadway (LR), which is 60 m away from upper pillar, becomes unstable. In order to control the surrounding rock of lower roadway, a physical model experiment and a 3D numerical calculation were performed in this study. The results of physical similarity simulation experiment show that mining of longwall face in UCS will lead to fracturing of key layers at a high elevation (KLHE) far away from the coal seam. The expanded goaf area caused large‐scale fracturing and rotation of the KLHE, which resulted in significant strata pressure behavior in LR. The numerical calculation results show that the LR should be within 19 m of the coal pillar. Finally, a plan which includes a proper location and a supporting system was proposed. The feasibility of the proposed plan is verified by an industrial application.

Section: Ucs Main Roofmentioning

confidence: 99%

Study on the movement characteristics of the overlying stratum and surrounding rock control in ultraclose coal seams: A case study

Zhu¹,

Yao²,

Xia³

et al. 2020

“…For their unique features of high strength, great thickness, and good integrity, thick and hard roof formations suspended over a large space can bear the weight of the overlying weak rock formations and present a block structure after fracture. 53 In China, Qian et al 54 raised a voussoir beam structure based on field measurements and showed that the hard rock was broken and formed an arrangement of articulated rock blocks under the horizontal thrust force, as shown in Figure 1(a); it can be seen that the voussoir beam model forms a large structure. [50][51][52] Recently, the voussoir beam has been widely applied.…”

Section: Voussoir Beam Structurementioning

confidence: 99%

“…53 According to the solution of Qian et al, 54 the lateral thrust is a necessary condition for the formation of a complete voussoir beam; the vertical shear force and horizontal thrust acting on block A under uniform load are given by. 53 According to the solution of Qian et al, 54 the lateral thrust is a necessary condition for the formation of a complete voussoir beam; the vertical shear force and horizontal thrust acting on block A under uniform load are given by.…”

Section: Voussoir Beam Structurementioning

confidence: 99%

“…[50][51][52] Recently, the voussoir beam has been widely applied. 53 In China, Qian et al 54 raised a voussoir beam structure based on field measurements and showed that the hard rock was broken and formed an arrangement of articulated rock blocks under the horizontal thrust force, as shown in Figure 1(a); it can be seen that the voussoir beam model forms a large structure. The thick hard roof breaking and movement evolution are from A to C, and the balance of the key blocks A, B, and C near the coal wall in the separation zone has a direct effect on the control of the overlying stratum, as shown in Figure 1…”

Section: Voussoir Beam Structurementioning

confidence: 99%

“…On this basis, Qian subsequently proposed the restriction conditions for sliding failure and crushing failure. 53 According to the solution of Qian et al, 54 the lateral thrust is a necessary condition for the formation of a complete voussoir beam; the vertical shear force and horizontal thrust acting on block A under uniform load are given by.…”

Section: Voussoir Beam Structurementioning

confidence: 99%

See 2 more Smart Citations

Failure mechanism and fracture aperture characteristics of hard thick main roof based on voussoir beam structure in longwall coal mining

Zhang

Jin

Song

et al. 2019

Self Cite

The mechanism and fracture aperture of thick hard roof failure were theoretically analyzed from the perspective of elastoplastic mechanics. A uniform load cantilever beam was established by considering the voussoir beam structure and stress condition. According to the stress inverse principle in solving the plane strain problem, the internal stress component analytic solution was deduced. Considering the lateral thrust and shear force and by applying the Mohr-Coulomb failure criterion, the plastic zone boundary equation was obtained. Further analysis of the equivalent stress, equivalent strain, elastic energy density, distortion energy density, and strain energy density was studied with blocks of four different lengths, combined with the rotation angles after failure, to analyze the fissure aperture between straight and curved fracture traces. The theoretical analysis reveals that the deviatoric effect plays the lead role in rupture initiation and propagation; the cracks will deflect during failure, and the fracture trace presents a curved shape. The variation of fracture aperture exhibits a tendency to increase first, then decrease, and then increase along the fracture trace.The analytical approach presented in this paper provides a theoretical basis for determining the main seepage channel flow in underground mining. K E Y W O R D Sfailure mechanism, fracture aperture, theoretical analysis, thick hard roof, underground mining, voussoir beam structure

Breaking law of overlying strata in shallow coal seam fire area under thermal–mechanical coupling effect

Zhu

Gao

et al. 2023

The cracks formed by the breaking and collapse of the overlying strata are the oxygen supply channels for the continuous combustion of coal fires. The development of cracks is of great significance for determining the scope of the fire area and controlling the fire efficiently and accurately. To study the development law of cracks, a breaking model of the overlying strata in the shallow coal seam fire area is established on the basis of beam theory considering the coupling effect of gravity load and temperature field. The physical model of the coal fire is established based on the similarity principle.The temperature data from rock strata in the model are monitored by the infrared thermal imager. The dynamic distribution function of the roof temperature field is obtained by fitting. According to the breaking model theory, the position of the maximum tensile stress on the roof of the shallow fire area is the middle of the lower surface. The theoretical calculation value of the first breaking distance of the roof is 0.575 m, which is consistent with the experimental results of the physical model. The maximum tensile stress of the roof under the thermal-mechanical coupling is slightly less than that under the load only. For shallow coal seams, the thermal stress generated by the coal fire increases the first breaking distance of the roof.