Purpose is to analyze nature of rock deformation and to estimate experimentally state of mine workings being supported under the conditions of areas disturbed by coal mining.Methods. The studies involved field instrumental observations within measuring points equipped with contour benchmarks. Express method was applied to determine height and width of the mine working; typical supported areas were designed; and photographs were taken. The research was conducted in a belt roadway and ventilation raise of western longwall 11 (c 18 seam of MM "Pivdennodonbaske No. 1"), and in their connections with the longwall.Findings. It has been determined that the longwall effect in the mine working, being supported repeatedly, is 80 -60 m in front of a stope; vertical convergence within the area is more than 1 m; floor rise share is almost 76%; and share rate is more than 3 mm/day. It has been specified that local destruction of anchor fitting as well as almost 70% of deformation of frame support is observed within the zone of the longwall affect. It has been identified that potential inrush area from the belt roadway is between supports 3 and 9 of a face zone support; i.e. distance from the seam edge is more than 2.4 m. It has been proved that the use of rigid protective structures is not efficient in the context of soft floor rocks since the protective structures function like dies. Condition of the belt roadway, being constructed and supported behind the longwall, is satisfactory; boundary deformations are within the range of the support flexibility.Originality. Regularities concerning deformation of boundaries of mine workings under the conditions of unstable wall rocks of c 18 seam (MM "Pivdennodonbaske No. 1"), when the mine workings are being constructed and supported behind a stope to be used repeatedly for following longwall, have been determined. Regularities of the process when rocks are forced out into a mine working cavity remained after protective structure, being constructed along a mine working at the boundary of the worked-out area, have been identified as well as regularities of vertical convergence rocks within terminal sites of the longwall.Practical implications. The findings can be used to develop measures and means for the stability of development mine workings under the conditions of unstable wall rocks and measures to prevent their fall within the tail longwall sites.
A floor heave controlling method has been substantiated, based on the creation of locally reinforced zones of a special shape in roadway floor, which allows saving stability even with a low rocks friction ratio. The method is based on a mechanical model of the formation of an increasing strength spacer system in roadway floor. The numerical analysis of rock massif stress-strain state carried out by the finite element method, has made it possible to determine the mechanism of floor heave during rock reinforcing. The performed analysis of the simulation results has made it possible to determine the influence of the quality of rock reinforcing and the rock friction ratio value on the amount of heave in the mining-affected roadway. The effectiveness of the proposed method has been proven as a result of a comparative analysis.
Purpose is to develop anchoring with nonadhesive high-strength roof bolting in terms of large pre-destructive deformations and its testing under laboratory conditions.Methods. Laboratory studies of hydration hardening of self-extending mixtures, carried out with the use of digital microscope Bresser LCD 40-1600x, have determined the features of hydration of the modified mixtures. The developed mixture, testing by means of unevenly-component three-axial pressure (UCTAP), has determined its strength within post-hydration period, elasticity module, and deformation module. Bench tests concerning anchor fastening by means of self-expending mixtures as well as anchor glue Cement KL have helped perform comparative analysis of adhesive technique to hold anchors fixed and nonadhesive one. Underground on-site research to fasten anchors while Franciszek Karol chamber strengthening in the context of Wieliczka mine made it possible to determine dynamics of anchor loading.Findings. It has been grounded experimentally that adding of Sika BV 3M ingredient to self-extending mixture results in up to 30% intensification of its strength limit on uniaxial compression. It has also been grounded experimentally that maximum effort to fasten anchor bolts by means of self-extending mixtures, excesses efforts for those bolts fastened with the help of resins more than twice. Analysis of operation mode of such anchors means that the action of anchor -fastener -rock system is close to that by modern energy absorbing bolts. Originality.A new concept of anchor fixation at the expense of their fastening by means of self-extending mixtures throughout the hole length has been formulated. During the hardening process, 30 -50 MPa pressure is developed making it possible to intensify maximum fastening effort being more than two times higher to compare with adhesive technique. Moreover, constant resistance is provided in the process of the anchor bolts displacement within a hole; the resistance is similar to that provided by adhesive technique. Practical implications.The obtained results, having sufficient practical accuracy, can be used for the development of new anchoring in the context of large deformations of a stope boundary. If the parameters are substantiated theoretically and bench testing is passed, the proposed anchoring technique can be implemented in the stopes of coal mines, ore mines as well as nonmetallic ones. That favours the increase in load bearing capacity of the anchorage and rock support in terms of their elastic deformation.
Purpose. Development a modified model of geomaterials for numerical simulation of the behavior of rocks in a true triaxial stress field. Methodology. The research was conducted on specimens of coal grade "С". Input parameters of materials for basic models in the modeling by the finite element method were taken from the physical experiment. The experiment was conducted on the installation of true triaxial compression. The results of comparative studies on the behavior of rocks in the true triaxial stress field using the experimental method and numerical mathematical modeling are presented. Modeling is conducted by the finite element method in Ansys Inc software. The results of tests on the strength of coal specimens in generalized compression conditions are taken as in-situ properties. findings. It is established that use of classical deformation models-the elastic model and Drucker-Prager model-with numerical mathematical modeling of geomechanical processes is in error when describing the behavior of geomaterials in a volumetric field of stress of 30-15 % relative to the experiment. In this case, modeling with the use of an elastic model does not only cause a significant quantitative error, but also fails to reflect the quality of the dependence of the Young module and the volume compression module on average stresses at all stages of the strain. To adequately imitate the model of geomaterials, one must take into account the anisotropy of the elastic modulus, the shear modulus and the coefficient of transverse deformation, as well as the functional dependence of the dilation from the plastic deformation and the coefficient of rigidity. Originality. The Drucker-Prager model was modified by taking into account the anisotropy of coal properties. Depending on the "average stress-average deformation", the calculation error for the elastic model is 33 %, for the Drucker-Prager model it is 15 %, while for the modified Drucker-Prager model it is 0.14 %. Practical value. Using the results of the study can improve the accuracy of the prediction the stress-strain state of geomechanical objects.
Purpose. Justification of feasibility of non-explosive destruction of hard rock during in-seam workings based on the obtained dependences related to changes of physical and mechanical properties of non-explosive destructive mixtures (NDM) in the process of hydration in borehole charges causing crack growth in the near-hole area.Methods. Mine in-situ observations at gauge stations were used to determine dynamics of footing bulging. Photofixation method allowed to record discrete state of rocks in the footing during the repair works. The optimal layout for reinforcing the footing was developed in laboratory conditions on structural models by the analysis of longitudinal and transverse system deformations, and by studying the volume of rocks squeezed into the cavity simulating the working.Findings. It has been experimentally proved that the footing rocks have a block discrete structure at a distance of at least half the width of inelastic deformations zone. The empirical dependences are obtained, describing footing bulging and horizontal compaction of rocks under the influence of loading, as a result of the disturbance of the rocks equilibrium state by mining operations for consolidated and non-consolidated rocks.Originality. Formation of a consolidated zone in the form of a straight prism with the vertex of its base triangle facing footing allows to reduce compaction of rocks under the mine by 20%, the footing bulging by 41.8%, and to decrease the volumes of rocks deformed in the working cavity by 41.5%. Practical implications.The obtained results, with accuracy sufficient for practical application, can be used to develop new ways of ensuring stability of footing in cases when rocks have a high degree of destruction. The proposed scheme of local reinforcing, provided its parameters are theoretically justified, can be realized in mine workings with bulging to more than 500 mm. This will help slow the rate of footing deformations and improve the state of workings in difficult mining and geological conditions.
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