Assessment of the Strength of Inclined Coal Pillars through Numerical Modelling based on the Ubiquitous Joint Model

Das, Arka Jyoti; Mandal, Prabhat Kumar; Paul, Partha Sarathi; Sinha, Rabindra Kumar; Tewari, Subhashish

doi:10.1007/s00603-019-01826-4

Cited by 52 publications

(21 citation statements)

References 29 publications

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“…Previous work has assessed the use of various constitutive models for layered jointed rock masses (Adhikary and Dyskin, 1998;Sitharam et al, 2001;Sainsbury and Sainsbury, 2017;Zhou et al, 2017) and their strength and deformation performance in the simulation of underground excavations (Jiang et al, 2006;Jia and Tang, 2008;Das et al, 2019;Ding et al, 2019). These studies were mainly focused on rock masses with a set of joints, while little attention has been paid to the mechanical characteristics of CJRM and their excavation responses in underground engineering.…”

Section: Discussionmentioning

confidence: 99%

“…For example, Jaeger (1960) proposed a theory based on the action of a single weak plane to predict the strength properties; Nova (1980) (Nova and Zaninetti, 1990) used the traditional Mohr-Coulomb (M-C) strength criterion to analyze the directional failures and this method has been used in the development of the ubiquitousjoint (U-J) model in Flac 3D (Itasca Consulting Group, 2011). Other researchers (Adhikary and Dyskin, 1998;Sitharam et al, 2001;Wang and Huang, 2009;Sainsbury and Sainsbury, 2017;Zhou et al, 2017;Das et al, 2019) further improved the constitutive equations of U-J model based on equivalent continuum methods.…”

Section: Introductionmentioning

confidence: 99%

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An Enhanced Ubiquitous-Joint Model for a Rock Mass With Conjugate Joints and Its Application on Excavation Simulation of Large Underground Caverns

et al. 2021

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A conjugate jointed rock mass (CJRM) is a rock mass with two sets of intersecting joints formed from intact rock under shear. Its mechanical properties and excavation-induced hazards of large underground caverns are different from those of common rock masses because of the unique geological origin thereof. To demonstrate numerically the excavation responses of CJRM, the ubiquitous-joint model is enhanced by consideration of the specific mechanical behaviors of the rock mass. In the enhanced model, CJRM is considered as the composite of columns of rock and two sets of weak planes of joints. The local coordinates, failure modes, and failure sequences of the rock columns and joints are redefined based on the composite characteristics of CJRM, and the failure criteria and plastic potential functions are accordingly modified. The enhanced model is verified numerically by triaxial compression tests and then employed to simulate the excavation of large underground caverns of a pumped storage power station in China. Results show that the modification of the local coordinate system, failure modes, and failure sequences made in the enhanced model is suited to the simulation of the mechanical behaviors of CJRM. Compared with the original ubiquitous-joint model, the enhanced model allows better predictions of the distribution of plastic zones and magnitudes of deformations in simulating underground excavations in CJRM and helps to assess the excavation-triggered hazards more accurately.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Enhanced Ubiquitous-Joint Model for a Rock Mass With Conjugate Joints and Its Application on Excavation Simulation of Large Underground Caverns

et al. 2021

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“…In general, UCS is the primary reference index employed for pillar strength designs based on experimental tests performed under pure uniaxial compression conditions. However, field applications have indicated that multiple www.nature.com/scientificreports/ pillars exhibit inclination angles and loadings due to combined compression and shear loading 17 . Whereas, the evaluation methods of pillar strength based on traditional UCS test ignore the influence of inclination angle to the pillar stability.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the shear stress component enhanced the pillar instability. Das 17 observed the overestimation of inclined coal pillar strength using the traditional pillar strength formulae as these formulae do not consider the inclined rock strata shearing characteristics into account. In addition, the bedding plane shear failure also reportedly dominated the inclined rock strata.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on granite acoustic emission and micro-fracture behavior with combined compression and shear loading: phenomenon and mechanism

Cao

Chen

et al. 2020

Sci Rep

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One element that is essential to consider in underground mining engineering applications is the possibility of pillar failure, which can result in deadly geological disasters, including earthquakes and surface subsidence. Pillars are commonly present under an inclined state and are significantly dependent upon combined compression and shear loading. However, many scholars regard the pure uniaxial compression strength (UCS) of rock as the main evaluation index of pillar strength, which is inconsistent with the field practice. Hence, the present study developed a novel combined compression and shear test (C-CAST) system, which was applied in the investigative acoustic emission (AE) experiments to characterize the failure mechanism and micro-fracture behavior of granite specimens at different inclination angles. The experimental results presented the exponential decrease of UCS of inclined specimens with increase in the shear stress component. Changes in the inclination angle with a range of 0°–10° produced a splitting-shear failure fracture mode from the initial splitting failure. In comparison, an increase in the inclination angle from 10° to 20° produced a single shear failure fracture mode from the initial combined splitting-shear failure. The specimens exhibited nonlinearly reduced microcrack initiation (CI) and damage (CD) thresholds following an increase in the inclination angle, suggesting the dependence of the microcrack initiation and propagation on the shear stress component. The ratio of CI and CD thresholds to inclined UCS varies within a certain range, indicating that the ratio may be an inherent property of granite specimens and is not affected by external load conditions. Additionally, the rock fracture behavior was largely dependent upon the mechanism of shear stress component, as validated by the microcrack initiation and growth. Finally, a modified empirical formula for pillar strength is proposed to investigate the actual strength of inclined pillar. Results of a case study show that the modified formula can be better used to evaluate the stability of inclined pillars.

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“…Compared with the flat coal pillars, the stress environment of the inclined coal pillars is more complex because of the asymmetric stress distribution. Das et al [16,17] analyzed the failure stress states within the coal pillars having different dip angles and elucidated the procedures to estimate the strength of the inclined coal pillars by the numerical modeling technique. Zhao et al [18] analyzed the mechanical characteristics of narrow coal pillars' gob-side entry in inclined coal seams and obtained the damage form of coal pillars with different widths during excavation.…”

Section: Introductionmentioning

confidence: 99%

Field and Numerical Investigation on the Coal Pillar Instability of Gob‐Side Entry in Gently Inclined Coal Seam

Wan

Zhang

et al. 2021

Advances in Civil Engineering

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In order to study the coal pillar stability of gob-side entry in gently inclined coal seam, a comprehensive method including theoretical analysis, numerical modeling, and field monitoring was applied to study its fracturing and instability mechanism. The results show that the uneven horizontal stress was the internal cause of entry asymmetric deformation and failure in inclined coal seam. In gently inclined coal seam, the rotation movement of the main roof and stress distribution were closely related to inclination of the coal seam. Based on the asymmetric deformation characteristics and mechanisms of entry, a collaborative control technology of roof cutting for pressure relief and support strengthening has been put forward. The research results have practical signiﬁcance for revealing the mechanism of entry damage in gently inclined coal seam mining and proposing engineering measures to prevent coal pillar damage and disaster occurrence.

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Assessment of the Strength of Inclined Coal Pillars through Numerical Modelling based on the Ubiquitous Joint Model

Cited by 52 publications

References 29 publications

An Enhanced Ubiquitous-Joint Model for a Rock Mass With Conjugate Joints and Its Application on Excavation Simulation of Large Underground Caverns

An Enhanced Ubiquitous-Joint Model for a Rock Mass With Conjugate Joints and Its Application on Excavation Simulation of Large Underground Caverns

Experimental study on granite acoustic emission and micro-fracture behavior with combined compression and shear loading: phenomenon and mechanism

Field and Numerical Investigation on the Coal Pillar Instability of Gob‐Side Entry in Gently Inclined Coal Seam

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