Accuracy Verification and Correction of D-InSAR and SBAS-InSAR in Monitoring Mining Surface Subsidence

The accuracy of InSAR in monitoring mining surface subsidence is always a matter of concern for surveyors. Taking a mining area in Shandong Province, China, as the study area, D-InSAR and SBAS-InSAR were used to obtain the cumulative subsidence of a mining area over a multi-period, which was compared with the mining progress of working faces. Then dividing the mining area into regions with different magnitudes of subsidence according to the actual mining situation, the D-InSAR-, SBAS-InSAR- and leveling-monitored results of different subsidence magnitudes were compared and the Pearson correlation coefficients between them were calculated. The results show that InSAR can accurately detect the location, range, spatial change trend, and basin edge information of the mining subsidence. However, InSAR has insufficient capability to detect the subsidence center, having high displacement rates, and its monitored results are quite different from those of leveling. To solve this problem, the distance from each leveling point to the subsidence center was calculated according to the layout of the rock movement observation line. Besides, the InSAR-monitored error at each leveling point was also calculated. Then, according to the internal relationship between these distances and corresponding InSAR-monitored errors, a correction model of InSAR-monitored results was established. Using this relationship to correct the InSAR-monitored results, results consistent with the actual situation were obtained. This method effectively makes up for the deficiency of InSAR in monitoring the subsidence center of a mining area.

Numerical experiment research on failure characteristics of anchored rock with negative Poisson’s ratio bolt

With the continuous increase of mining depth and engineering burying depth, the nonlinear physical and mechanical phenomena exhibited by rock are also more complicated. The load value often exceeds the yield strength of the traditional Poisson's ratio supporting materials, causing the supporting body to fail. Therefore, the bolt still needs to further in-depth research on new materials. In this paper, the rock model with a negative Poisson’s ratio bolt had been established, the material properties of negative Poisson’s ratio and the working principle of RFPA software were introduced, and RFPA software was used to study the reinforcement effect of negative Poisson's ratio bolt on the rock. The numerical experiment results show that, compared with the positive Poisson's ratio bolt, the negative Poisson's ratio bolt can significantly increase the bearing capacity of anchored rock, enhance the friction between the bolt body and the surrounding rock, and limit the rock movement. The anchored rock with negative Poisson’s ratio bolt can absorb more energy. Negative Poisson's ratio material is one of the future development directions of bolt material.

Numerical Experiment Research on Failure Characteristics of Anchored Rock With Negative Poisson’s Ratio Bolt

With the continuous increase of mining depth and engineering burying depth, the nonlinear physical and mechanical phenomena exhibited by rock are also more complicated. The load value often exceeds the yield strength of the traditional Poisson's ratio supporting materials, causing the supporting body to fail. Therefore, the bolt still needs to further in-depth research on new materials. In this paper, the rock model with a negative Poisson’s ratio bolt had been established, the material properties of negative Poisson’s ratio and the working principle of RFPA software were introduced, and RFPA software was used to study the reinforcement effect of negative Poisson's ratio bolt on the rock. The numerical experiment results show that, compared with the positive Poisson's ratio bolt, the negative Poisson's ratio bolt can significantly increase the bearing capacity of anchored rock, enhance the friction between the bolt body and the surrounding rock, and limit the rock movement. The anchored rock with negative Poisson’s ratio bolt can absorb more energy. Negative Poisson's ratio material is one of the future development directions of bolt material.

Rock Movement in Tectonic Zones. Mining Activities and Rock Pressure Management in the Norilsk-Kharaelakh Fault Area

The article describes the rock mass state within the boundaries of the Skalistiy mining allotment. The ore mass within the mine field was found to preserve its rock-bump hazard and show high mobility in the impact zone of the Norilsk-Kharaelakh Fault and the associated high failure potential manifested as roof cavings. Based on the monitoring results along underground profile lines, it was concluded that the displacement process is currently at its initial stage. Moreover, the maximum subsidence in the central part of the profile line is about 3 times higher (up to 35 mm) than in other areas. This is caused by immediate proximity of this zone to the Norilsk-Kharaelakh Fault. Assessment of the bump hazard level of this rock mass with the help of the Prognoz-2 instrument that was performed by the rock-bump forecasting and control teams of the mine and the Norilskshakhtstroy company, showed the 'Not Hazardous' category in all cases. However, the progress of mining operations towards the Norilsk-Kharaelakh Fault may lead to deterioration in the condition of mine workings. This can be manifested through rock exfoliation from the walls of the advance workings of the safety layer in highly and extremely faulted rocks. In addition, permanent workings, which are one of the most critical structures of the production level and which will be used until the development of the deposit area adjacent to the Norilsk-Kharaelakh Fault is completed, will be maintained in increasingly difficult conditions. The article describes recommendations for mining operations in the fault area with account for the current mining and geomechanical situation and the potential for its change.

Three-Dimensional Physical Similarity Simulation of the Deformation and Failure of a Gas Extraction Surface Well in a Mining Area

Surface well deformation and failure in a mining area are a key issue challenging the surface well gas extraction technique. To provide information for the design of gas extraction surface wells in mining areas, the deformation and failure of surface wells with different materials under the influence of mining-induced rock movement were analyzed based on a three-dimensional physical similarity simulation and key strata theory. The research findings reveal that the fractures in the overlying strata had an elliptic-parabolic shape. The stope center was the highest point in the fracture zone. Horizontal shear deformation was most likely to occur in the thick strata (horizontal shear deformation could be larger if they were key strata) with large strength and stiffness near the intersection between the fracture surface of the overlying strata and the surface well. Due to the shear force and bending moment of the key strata, the surface well deformed into an S-shape. In addition, the surface well was vulnerable to shear deformation in the key strata. The surface well deformation did not weaken from bottom to top due to rock movement. Instead, it was subject to the influence of the rupture strength of the key strata. The surface well above the key strata was prone to tensile strain-compressive strain transition. In contrast, an abrupt change in the compressive strain occurred in the surface well below the key strata where tensile failure may occur. Moreover, a mechanical model of the surface well during the movement of the key strata was established according to the characteristics of the surface well deformation. The test results provide important information on the design optimization of surface wells and high-risk area protection in mining areas.

VUOIŊŊALAŠVUOHTA—Sámi Spirituality, Yoik and Its Relations

The subject of identity is important in today’s political landscape. This article explores the way in which indigenous identity in particular is a contested subject, taking into account the way indigeneity in itself was, and still is, created within colonial contexts. The “validity” of indigenous peoples and their political aims, as well as their right to live according to their own cultural paths, will often be determined according to racist ideas connected to authenticity and its stereotypical demands. Such concepts can furthermore turn inward, disconnecting indigenous peoples from their own heritage. How ideas of authenticity affect indigenous individuals and their processes of identification serves as a central question within this text. Central to the Standing Rock movement was the focus on spirituality and religion grounded in Lakota traditions and other indigenous cultures. The text accounts for how these practices affected Marielle Beaska Gaup, Sámi artist, activist, and mother, especially through her experiences as a juoigi, a traditional Sámi yoiker. The ever-present singing and drumming at camp, chiefly during the summer, tied the mundane and ritualistic together, a characteristic mirroring traditional Lakota and Sámi ways of life, in which the spiritual at times seem to be an integral part of daily life. Building upon Marielle’s observations, the text looks at the way indigenous people’s relationships with spiritual traditions can affect processes of identification, and how indigenous identity can be intimately link to its spiritual heritage. This article employs indigenous methodologies, centering research on Sámi and indigenous perspectives, values and agendas. Marielle’s reflections contribute to the exploration of the connections between spirituality and Sámi identities; furthermore, they enable us to connect ideas about moving beyond the authoritarian ideals of “authentic identities”, through re-centering on indigenous experiences and processes of identification My main source is Marielle’s interview and articles based on interviews with people from Standing Rock The analysis centers on Marielle’s thoughts together with my own, with support from indigenous researchers bringing their own knowledge about identity and spirituality forward.

Top coal caving parameters of the thick lower seam in ultra-close multiple seams with combined mining

In the combined mining of ultra-close multiple seams with thin upper seam and thick lower seam, the mining of thin upper seam may lead to damages of the interburden and collapse of overburden. As a result, the roof of the thick lower seam in the fully mechanized caving process is turned into layers consisting of parts with different medium characteristics, in terms of damage severity and rock size, and the caving and recovery of top coal is significantly affected. Therefore, we propose a study of top coal caving and roof rock movement law under different fracture conditions based on two dimensional discrete element numerical simulation software program. The results revealed that roof rock channeling into the top coal was observed in the coal caving process in the presence of a huge difference between the lump sizes of roof rock and top coal of the lower seam, resulting in low recovery ratio. And the one cut/one caving upward caving pattern was the optimized top coal caving parameter. This study serves as a reference for future studies of top coal recovery in the combined mining of contiguous coal seams with thin upper seam and thick lower coal seam.