Inversion method of stress fields in the discontinuous zone of deep coal seam
[Objective]As the depth of coal mining increases,the activation of discontinuous structures,such as faults,poses a significant risk to the safe and efficient mining of coal seams.Therefore,acquiring precise knowledge of the distribution of in-situ stress is paramount for the design,construction,and disaster prevention of mining engineering.[Methods]This study proposes an inversion method for in-situ fields applicable to discontinuous zones of deep coal seams.(1)Given the discontinuity characteristics of the deep in-situ stress field,stability discriminants for normal faults and stability discriminant equations for positive faults,reverse faults,and strike-slip fault zones are derived based on the lateral pressure coefficients of in-situ stress.(2)A long short-term memory neural network algorithm is adopted to optimize the learning of the in-situ stress field data formed in different periods sequentially to effectively solve the nonlinearity,discreteness,and multi-noise problems of the measured deep in-situ stress data and to ensure that the excellent in-situ stress data information is remembered for a long time and that the inferior in-situ stress data information is forgotten in time.[Results]This study considers the main and auxiliary well areas of Yingjun's second mining area in Shanghai Miao as the research background and establishes an algorithm model for long short-term memory neural networks.Given the distribution characteristics of the in-situ stress field in fault areas at different scales,an inversion calculation of the in-situ stress field in discontinuous areas of deep coal seams was conducted.[Conclusions]The correlation coefficient between inverted and measured stress fields was 0.945,with an average error of 12.897％.The standard deviation of the stress difference is 2.000.The amount and direction of the regional stress field of the fault will also change.Compared with the regional stress field,the in-situ stress field in the DF15 and SF15 large-scale fault zones is approximately 5 MPa lower,and the counterclockwise direction is deflected.The in situ stress in the surrounding rock area at the top and bottom of the coal seams adjacent to DF15 and SF15 large-scale fault zones is relatively small,and no stress concentration area is detected.The eighth overlying coal seam was tilted toward horizontal in-situ stress by extrusion during deposition,and a concentration of in-situ stress was detected on the top rock.Therefore,for deep coal seam mining in the well field,the protective-layer mining method can be adopted,i.e.,the lower 15 coals can be mined first to provide protection and pressure relief for the mining of the upper 8 coals to ensure the safety and reliability of deep-mining in the well field.Folds mainly control the distribution of the horizontal in-situ stress field,and the in-situ stress of the rock mass in the axial part of the backslope and the inner arc increases,while the in-situ stress of the outer arc of the obliquity is relatively small.Therefore,the inversion method proposed in this study can offer a new perspective for reconstructing the stress fields in deep discontinuous areas.
deep coal seamsdiscontinuousin-situ stress fieldinversion method
万方数据
维普
