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 is to analyze parameters of a new method to fasten roof bolts with the help of nonadhesive mixtures extending while hardening along with the development of high expansion pressures.Methods. The research, concerning forces applied while fastening roof bolts by means of self-extending mixtures, has been carried out under full-scale laboratory conditions using pressing-in method. Rock mass was simulated by means of concrete in plastic and metal forms, and steel pipes. The latter simulated ultimate rigidness conditions. Roof bolts were simulated by means of reinforcement steel fragments. In the context of the research, bolt diameters varied from 8 to 32 mm, and borehole diameters varied from 26 to 43 mm. Hydraulic 50-ton press was used for the tests. The testing results were applied to obtain regressive dependences of bolt fastening efforts in terms of different ratios between roof bolt diameter, borehole diameter, and incapsulation depth. Mine experiments concerning efforts to fasten Rockbolt System AG roof bolts of J64-27 type to strengthen chamber 1 of level 3 in Velychka mine were performed using a method of static bolt extraction. Hydraulic extraction device was equipped by ZEPWN CL 18T sensor and CL 162z-DW recorder.Findings. It has been proved experimentally that operation mechanism of the roof bolts, fastened by means of selfextending mixtures during hydration hardening, is close to the modern energy absorbing bolts. Bolt diameterborehole diameter ratio range, when ultimate effort of bolt fastening by means of extending mixtures is achieved, has been determined. Functional connection between the efforts to fasten roof bolts, using extending mixtures, and diameters of borehole and the roof bolt has been identified as well as linear connection between incapsulation depth and bearing capacity of the roof bolt. Originality.A new concept to fasten roof bolts with the help of nonadhesive technique owing to their quazistatic compression between borehole walls, taking place as a result of hydration self-extension of mixtures which can achieve 30 -50 MPa pressures under the conditions of zero deformations, has been developed. Regularities in the variation of efforts to fasten bolts, using the technique, depending upon roof bolt -fastening mixture -rock mass system geometry have been determined. Practical implications.The results can be used to calculate parameters of roof bolting with high bearing capacity under the conditions of large deformations. The proposed fastening method may be implemented in mine workings.
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