The mining pressure in mixed workface using a gangue backfilling and caving method

Self Cite

Aiming at serious deformation and failure of large‐section coal roadway under mined zones in ultra‐thick coal seam, its deformation and failure characteristics are analyzed based on the field measurement. This paper reveals the mechanism of roadway roof separation, roof leakage, and right rib extrusion. Based on the mechanism, two kinds of secondary support schemes are proposed, that is, “grouting + I‐steel support + bolt” (scheme I) and “grouting + U steel support + anchor + anchor cable” (scheme II). The industrial experiment is carried out at 1070 auxiliary transportation roadway in Tashan Coal Mine. The measured results show that the roadway roof separations of the secondary support scheme I and II are only 1/11 and 1/46 of the original support scheme, respectively, while the lateral displacements of the roadway are only 1/7 and 1/44 of the original support scheme. It could be seen that the deformation and failure of the roadway surrounding rock have been well controlled.

\frac{E_{m}}{E_{r}} = 10^{0.0186 RQD - 1.91}

…”

Section: The Deformation and Failure Mechanismmentioning

confidence: 99%

\frac{σ_{cm}}{σ_{c}} = {()(, \frac{E_{m}}{E_{r}})}^{q}

where q is an empirical parameter, and 0.7 is taken in this paper …”

Section: The Deformation and Failure Mechanismmentioning

confidence: 99%

See 1 more Smart Citation

Failure mechanism of the large‐section roadway under mined zones in the ultra‐thick coal seam and its control technology

Tai

Xia

Meng

et al. 2019

Self Cite

“…Based on the theory of an elastic foundation beam, a method for calculating abutment stress in overlying strata with double load zones was proposed . Generally, the influence range of front abutment stress caused by mining disturbance is 30‐150 m, the stress concentration coefficient is 1.5‐3, and the peak stress position is approximately 5‐40 m ahead of the coal wall …”

Section: Introductionmentioning

confidence: 99%

“…29 Generally, the influence range of front abutment stress caused by mining disturbance is 30-150 m, the stress concentration coefficient is 1.5-3, and the peak stress position is approximately 5-40 m ahead of the coal wall. 30,31 Previous studies reflect the influence of mining disturbance on the distribution and evolution of abutment stress to a certain extent but do not consider the interaction of overlying strata and the transmission effect of by the overburden key strata on front abutment stress. Hence, in this paper, a mechanical model of the elastic foundation of overlying strata is established based on the mechanical properties of actual strata and elastic foundation beam theory.…”

Section: Introductionmentioning

confidence: 99%

A new theoretical method for calculating front abutment stress during coal mining

Liu

Wang

Liu

et al. 2019

The calculation of abutment stress has always been the most important topic in safe underground mining and design. In this paper, based on the formation mechanism of abutment stress, combined with the mechanical properties of actual strata and the theory of elastic foundation beams, a structure model of overlying strata with an elastic foundation is established, and a new theoretical calculation method of abutment stress is proposed. The new calculation method takes into account the interaction of the overlying key strata and the effect on the transmission of the front abutment stress and then analyzes the stress patterns of multilayered key strata under the combined action of the bending moment, shear force, and nonuniform load and its transmission to the underlying strata. In addition, based on field observations of panel 10 305 in the Xinglongzhuang coalmine, the influence range, peak position, and variation trend of the front abutment stress before and after breaking of the overlying key strata are studied and verified. The results show that the influence range of the abutment stress remains unchanged after KS1 breaks (eg, from 0 to 180 m), and its peak position shifts forward from 8 to 19 m, while the influence range (0‐180 m) and its peak position (6‐8 m in front of coal wall) remain unchanged after KS2 breaks; the abutment stress decreases, and the maximum decrease is 3.9 MPa in the range of 0‐22 m ahead of the coal wall after KS1 breaks, while the maximum decrease in the abutment stress is 2.1 MPa in the range of 0‐71 m ahead of the coal wall after KS2 breaks. The results of the new calculation method are basically consistent with the field observations and the existing theoretical results, showing that the method has good adaptability and reliability and can provide a new theoretical basis for on‐site design and construction practices.

An innovative technology of fracturing hard strata from the ground for precontrol of rock burst in a coal mine

Tai

Kuang

et al. 2022

Self Cite

Rock bursts are one of the most common dynamic disasters in coal mines and seriously affect safety production. At present, there are three common types of rock bursts: fault‐structure, fold‐structure, and thick/hard‐roof rock bursts. First, the paper proposed an innovative technology for mine ground fracturing to control those rock bursts. Then, for the new method, its fracturing devices, process, and monitoring technique for cracks were introduced. Next, we analyzed the detailed control procedures for those types of rock bursts and control principles of absorbing energy, blocking stress transmission, and reducing overall rock strength. To illustrate the control effect of ground fracturing for the rock bursts, we proposed a Voronoi block division method (VBDM) and multistrength criteria (MSC) consisting of Mohr–Coulomb Joint, Hoek–Brown Joint, and strain–stress equivalent method. Then, two numerical models using the VBDM and MSC were established. One is fault‐structure rock burst with ground fracturing and another is that without. From the numerical simulation, it was concluded that: (1) The ground fracturing will increase τ/σn, a ratio of shear stress to the normal stress of the fault, from 0.25 to 0.50, especially within 100 m of a working face to a fault. This situation indicates that ground fracturing will induce fault slip in advance, thus releasing energy in advance. (2) Fractured zones with low stress were formed by ground fracturing, which can reduce both upward extrusion pressure and normal stress, thereby triggering the fault slippage in advance. The energy released from the fault can be absorbed by the fractured zone, thereby controlling the advanced stress of the working face, and lowering the danger of rock burst.