Search

To prevent severe damage to the surrounding rock of the roadway under the high ground pressure within deep mining, the stress evolution of the surrounding rock was studied, and the surrounding rock control technology in the II1057 roadway of Zhuxianzhuang Coal Mine before and after passing fault was conducted through theoretical analysis, numerical simulation and engineering practice. The results show that when the roadway is advanced to 20 m away from the fault, the surrounding rock is broken, cracks are generated at 2.56 m above the roof, and the advance abutment pressure of the roadway is 17–20 MPa. Through the borehole detection technology, the development of the internal cracks in the surrounding rock was observed, and the surrounding rock control technology scheme (the advanced grouting in front of the roadway and the active support of rock bolt + anchor cable + M steel belt + steel beam + metal mesh) was proposed. The engineering practice shows that the roof separation, roof-to-floor convergence and sidewall convergence are greatly reduced, and the mechanical properties of the surrounding rock of the roadway are greatly improved, leading to the effective control of the deformation of the roadway surrounding rock.

The objective phenomenon of seepage reduction and self-healing is easy to occur in the mining fractured rock mass after long-term evolution process of coal seam after mining. In survey of this phenomenon, taking the No. 12401 work face of Bulianta Coal Mine and the No. 52306 work face of Daliuta Coal Mine in Shendong as typical test areas, the engineering exploration and theoretical research on the self-healing law in different areas of overburden were carried out. The evolution law of long-term self-healing process of overburden after mining was revealed. The results show that the fractured overburden of the two coal mines had achieved good self-healing effects 15 years and 7.3 years after mining, respectively. The areas with water conduction within the original water-conducting fractured zone have been significantly reduced. Although the caved zone still conducts water, the height has also been reduced. By taking the ratio of the vertical length of the self-healing section in overburden from the original water diversion to the water isolation to the height of the water-conducting fractured zone as the self-healing recovery rate for statistics, it is obtained that the self-healing recovery rate of No. 12401 work face in the overburden near the mining boundary and in the middle of the dip has reached 59.5% and 53.5% respectively, and the self-healing recovery rate of 52306 work face in the corresponding area is 25.8% and 47.5% respectively. Due to that No. 12401 work face has mined for a longer time and has a larger coal seam burial depth, its self-healing effect of fractured overburden is obviously better. Affected by the occurrence difference of different strata in the vertical direction of the overburden and the initial damasge degree in different areas in the horizontal direction, the distribution of the self-healing area is often discrete and discontinuous, in which the interval of the unrepaired area generally corresponds to the position of the key stratum or thick and hard rock layer, and the shorter the post mining life and the closer to the mining boundary, the more significant the dispersion. The self-healing effect of mining fractured rock mass is actually a process of permeability reduction and evolution under the comprehensive influence of multiple factors. For the mining conditions in Shendong coalfield, the residual settlement caused by stress compaction plays a leading role in the initial process within 1.5 to 2 years after coal mining, which is relatively significant in the overburden in the middle of the mining area. Then, the self-healing process has been dominated by the water-rock or water-gas-rock interactions in goaf. That is, the filling and sealing effect of the derivatives produced in the relevant process on the fractures and the roughness reduction of the fracture surface induced by hydraulic erosion directly affect the self-healing results. Therefore, whether there is long-term water seepage in the overburden after mining determines the difficulty of self-healing of fractured rock mass. Water conducting fractures in the overburden of most mines in Shendong are generally directly connected to the Quaternary loose layer or surface, and in recent years, there is abundant rainfall, which provides superior conditions for the generation of water-rock or water-gas-rock interactions and the promotion of self-healing effect.

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to provide a theoretical determination method for the fracture position of the main roof of the gob-side coal-rock roadway in a gently inclined coal seam (GCRGICS), a mechanical model of the overlying strata structure and a mechanical model of the coal rock body in the limit equilibrium zone were established based on the elastic–plastic limit equilibrium theory. The theoretical calculation formula of the fracture position of the main roof of the GCRGICS was derived. The fracture position of the main roof theory calculation and field test verification were carried out on 1511, 1509, and 151608 return airflow roadways with similar geological conditions in the Panjiang mining area of Guizhou Province. Combined with the similar simulation experimental results of the 1511 return airflow roadway, the differences between the similar simulation, field test and theoretical calculation results were all less than 1, which verified the practicality and reliability of the method. This method can be used to guide the reasonable width of coal pillar retention and the control of the surrounding rock in this type of roadway. [ABSTRACT FROM AUTHOR]

In view of the current technical difficulties in the detection of unfavorable geological bodies in karst areas, this paper starts with the fine detection of a borehole wall, near-field of the borehole wall rock and far-field of the borehole wall rock, deeply excavates the correlation characteristics between multi-source borehole data, and proposes detection technology for unfavorable geological bodies in karst development areas based on multi-source borehole data. This is used to establish a multi-source data depth mining model. The correlation characteristics between multi-source data are clarified. The borehole multi-source heterogeneous detection technology is proposed to realize the organic fusion between the detection data of different scales, and effectively estimate the extension range of structural planes and cavities. The joint interpretation method of multi-source drilling data can effectively realize the three-dimensional visualization of unfavorable geological bodies in karst development areas. Through a case analysis, it is shown that this technology is a new and effective exploration method in the engineering geological exploration of karst development areas, and can provide more abundant and reliable exploration data for the fine exploration of geological bodies in the exploration area. [ABSTRACT FROM AUTHOR]

At present, many studies have come to the conclusion that the coal seam contains primary CO gas, but the possibility of CO being adsorbed by coal after CO generated in drilling construction is not considered. In order to explore whether there is primary CO in spontaneous combustion coal seam in Northwest China, the original coal seam in-situ drilling detection method is used to detect primary CO. Three test boreholes are arranged in a row along the roadway side in the solid coal area not affected by mining. After the boreholes are sealed, high-purity N2 is used to replace the gas in the closed gas chamber, and the gas in the boreholes is extracted by a special air pump, so as to eliminate the impact of CO generated by coal oxidation on the test results during the construction of in-situ detection boreholes. On the basis of analyzing the source possibility of primary CO in coal seam and its emission theory, the variation characteristics of gas concentration in closed borehole with time are discussed. The results show that volume fraction of O2 and CO in the sealed borehole decrease rapidly with the extension of sealing time, and the volume fraction of O2 is stable below 2% after 12 days. After 12 days, the CO volume fraction is lower than 10−12, and no CO gas is detected by gas chromatograp. The gas in the borehole is mainly N2. It is concluded that there is no primary CO gas in the tested coal seam. The results of coal breaking test in N2 environment and coal sample oxidation test at normal temperature and constant temperature show that CO gas detected at the initial stage of borehole sealing comes from coal breaking operation in drilling construction.

The failure of surrounding rock in deep hard rock roadway is closely related to mining disturbance. In this study, the 13# stope ramp of −767 m level (at a buried depth of 1,197 m) at Hongtoushan copper mine was taken as the engineering background, a comprehensive analysis method of numerical analysis and borehole detection was put forward, and the evolution law of fracture depth of the ramp surrounding rock under the mining influence was obtained. The results show that the maximum tangential stress and fracture depth of the ramp surrounding rock on both sidewalls increase slowly at the initial mining stage. When the ore body above the ramp is mined, the maximum tangential stress and fracture depth of the ramp surrounding rock on both sidewalls increase rapidly, and the two parameters are positively correlated. Based on this, the ratio of the maximum tangential stress of the surrounding rock to the uniaxial compressive strength of intact rock (σθmax/σc) and the equivalent radius (a) of the roadway were used as parameters, and an equation for the fracture depth of the roadway surrounding rock was proposed. Through the case analysis, the results show that the proposed equation of fracture depth of the roadway surrounding rock has good prediction accuracy. This study enriches the research on the stability and failure mechanism of the roadway surrounding rock under the mining disturbance, and provides new basis for the support design of mining roadways.

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In view of the current technical difficulties in the detection of unfavorable geological bodies in karst areas, this paper starts with the fine detection of a borehole wall, near-field of the borehole wall rock and far-field of the borehole wall rock, deeply excavates the correlation characteristics between multi-source borehole data, and proposes detection technology for unfavorable geological bodies in karst development areas based on multi-source borehole data. This is used to establish a multi-source data depth mining model. The correlation characteristics between multi-source data are clarified. The borehole multi-source heterogeneous detection technology is proposed to realize the organic fusion between the detection data of different scales, and effectively estimate the extension range of structural planes and cavities. The joint interpretation method of multi-source drilling data can effectively realize the three-dimensional visualization of unfavorable geological bodies in karst development areas. Through a case analysis, it is shown that this technology is a new and effective exploration method in the engineering geological exploration of karst development areas, and can provide more abundant and reliable exploration data for the fine exploration of geological bodies in the exploration area.

Copyright of Advanced Engineering Science / Gongcheng Kexue Yu Jishu is the property of Advanced Engineering Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)