STUDIES OF NEW NONADHESIVE ANCHORING

Abstract

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 anchorglue 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 hasalso been grounded experimentally that maximum effort to fasten anchor bolts by means ofself-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.