Numerical assessment and substantiation of rational geometry for postless hinged support of development mine workings

Abstract

Purpose. To determine a rational range of inclination angles for the elements of postless hinged support used in development underground mine workings based on a quantitative assessment of their influence on the stress-strain state of the structure. Methods. Comparative finite-element modelling was performed in ANSYS for a straight horizontal top member (α = 0°) and two-element hinged configurations with inclination angles α = 20, 25, 30, and 35°. The calculations were carried out under static linear-elastic conditions using identical mechanical properties of the material and a control vertical load of 20 kN. For each configuration, the distributions of displacement and stress intensity were analysed. Comparative assessment was performed using maximum stress intensity, maximum displacement, and normalized and relative indicators of their variation. Findings. For the straight configuration, the maximum stress intensity was 417.23 MPa, with a maximum displacement of 115.8 mm. The transition to hinged geometry substantially reduced the maximum stress intensity to 184.17 MPa at 20°, 176.77 MPa at 25°, 192.91 MPa at 30°, and 236.10 MPa at 35°. The minimum value was obtained at α = 25°, corresponding to a reduction of 57.6% relative to the straight configuration. At the same time, among the hinged configurations, the maximum displacement increased progressively from 168.6 mm at 20° to 293.2 mm at 35°. Thus, the minimum stress and displacement values are achieved at different inclination angles. Originality. A non-monotonic dependence of maximum stress intensity on the inclination angle of the hinged top-member elements was established, while displacement increased with increasing angle. It was shown that the most favourable geometry according to the stress criterion does not coincide with that according to the deformation criterion, which substantiates the joint use of both indicators when selecting the geometric parameters of the support. Practical implications. For the adopted loading conditions and numerical formulation, the range α = 20-25° was identified as rational: at 20°, the minimum displacement among the investigated hinged configurations is achieved, whereas at 25°, the minimum maximum stress intensity is obtained. The results can be used as a preliminary basis for selecting support geometry prior to comprehensive modelling of the interaction within the “rock mass-support” system and subsequent experimental or field validation.