Abstract
In the deep coal mines of OKD, Inc., both bolts and long bolts of different designs are used for the rock massif and steel arch support reinforcement. Continuous measurement of forces in 6 strand bolts and 1 cable bolt (long bolts, generally) was carried out during the trial operation of the modified Room and pillar mining method at Mining operation 2, site North, OKD, Inc. Hydraulic dynamometers were installed on these long bolts and a monitoring of forces took place throughout the life-time period of the mining panel No. V. From this measurement, a knowledge of their different load behavior with respect to the input stress parameters was obtained. The input intensity of the force applied to the bolting elements is burdened by losses of various kinds. The subject of the article is a description and analysis of the intensity of the initial stressing force applied to individual long bolts (with a threaded clamping bush or wedge barrel) and quantization of short-term stress losses with a description and analysis of these.
Highlights
For the excavation of coal seams in the OstravaKarviná district, the exclusively used mining method is the longwall mining [4]
In the protective shaft pillar of Mining operation 2, site North, OKD, Inc. from May 2014 until October 2017, the trial operation of the modified mining method Room and Pillar was carried out. The principle of this mining method is to leave stable coal pillars, which will be the permanent support of the overburden
In order to avoid a massive stratification of the overburden, a system of reinforcement of mining works was designed using a rock bolt reinforcement and various types of long bolts
Summary
For the excavation of coal seams in the OstravaKarviná district, the exclusively used mining method is the longwall mining [4]. This method [13] is characterized by forming retained stable coal pillars where galleries are exclusively driven in rockbolt support. The primary objective and function of the installed bolting elements (rock bolts, long bolts) is the transfer of shear and tensile loads acting in the massif, and the ability to bring a certain degree of stress into the massif and thereby positively affect it (closing microcracks, increasing the shear strength) It remains a question of how large forces, in combination with the torque of a drilling machine or device, act on the bolting element, what will be the intensity of these forces during the process and what factors affect this development of internal forces in the elements
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