Abstract
Slope stability is a prominent problem for the efficient application and promotion of highwall mining technology, especially when mining residual coal under high and steep end-slope conditions. This study proposes the concept of target time pillar strength based on the required coal pillar service time. Creep tests were performed to measure the time-varying properties of coal shear strength parameters under different loads, and a time-varying function was established by regression. The highwall mining length is divided into three categories based on discontinuous structural plane theory, including goaf, yielding, and elastic zones, all of which are considered to have resistances against shear stress. The basal coal seam is prone to weakening owing to the weight of overlying strata, which may shift the slope failure mode from circular to sliding along the weak layer. Numerical modeling was used to study the influence of the bearing stress and target time strength on the development of the yielding zone at the coal pillar ribs. The coefficients of the three zones were determined, and the temporal and spatial evolution patterns of the shear strength parameters of the weak layer were acquired. A slope stability calculation method is proposed based on rigid body-limit equilibrium theory that can quantify the influence of highwall mining operations on slope stability, which is significant for popularizing highwall mining technology.
Highlights
Slope stability is a prominent problem for the efficient application and promotion of highwall mining technology, especially when mining residual coal under high and steep end-slope conditions
Wang et al.[10] revealed the failure mechanism and process of coal pillars under highwall mining based on the stress distribution at the pillar rib, as derived from the I-II mixed mode crack model from fracture mechanics and failure criteria
Chandar et al.[18] performed numerical simulations to study the influence of mining length, pillar width, and highwall channel number on slope stability, and categorized slope stability scenarios using multi-linear regression, logistic regression, and naive Bayes classification methods
Summary
Slope stability is a prominent problem for the efficient application and promotion of highwall mining technology, especially when mining residual coal under high and steep end-slope conditions. A slope stability calculation method is required to determine the appropriate coal pillar parameters. A series of time-dependent laboratory studies on coal pillars is undertaken to investigate the potential failure mechanism of slopes under highwall mining operations based on discontinuous structural plane theory[21].
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