Abstract
The article presents methods of securing mining excavations using wooden cribs. For the underground room and pillar method used to excavate zinc and lead ore body in the Olkusz-Pomorzany mine in Poland, model tests for the replacement of rock pillars by wooden cribs are presented. In the first stage of research, the results of laboratory strength tests carried out on models of four-point, six-point and eight-point cribs made of wooden beech beams at a 1:28 scale arranged horizontally were determined. For the first time, a concave round notch connection was used to connect the beams of the wooden cribs. The maximal capacity of cribs consisting only of beams and filled with waste rocks taken from underground mining excavations was determined. In addition, the vertical deformations of the cribs at maximal loading force and their specific deformations are presented. Additionally, on the basis of load-displacement characteristics, the range in variability of the stiffness of empty cribs and those filled with waste rocks was calculated as a function of their compressibility. In the second stage of research, the room and pillar method was designed in the Phase2 numerical program. The aim of the study was to determine the stresses in the inter-room pillars. Based on the results of laboratory and numerical tests, a factor of safety was determined, indicating that it is possible to reduce mining losses while maintaining the safe exploitation conditions of the ore body.
Highlights
IntroductionThe rational management of mineral resources is aimed at combining the efficiency of their extraction, their comprehensive and rational use, and minimizing damage to the human environment
The rational management of mineral resources is aimed at combining the efficiency of their extraction, their comprehensive and rational use, and minimizing damage to the human environment.The use of resources is shaped at all stages of geological and mining activity, from the exploration and documentation of deposits, through the design, exploitation and processing of minerals
9a–d, the range of variability the stiffness of wooden cribs was calculated as a function of their compressibility
Summary
The rational management of mineral resources is aimed at combining the efficiency of their extraction, their comprehensive and rational use, and minimizing damage to the human environment. The use of resources is shaped at all stages of geological and mining activity, from the exploration and documentation of deposits, through the design, exploitation and processing of minerals. The main factors affecting the use of resources are, among others, the classification of resources, and mining losses and dilution of the deposit. In room and pillar methods, attempts are made to strengthen the excavations or replace the inter-room pillars by wooden or concrete constructions. Barczak and Tastillo [1], Korzeniowski and Skrzypkowski [2], and Korzeniowski et al [3] studied wooden cribs with beams of rectangular and square section. Daehnke et al [4], Dison and Smith [5], and Mining Product
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