Abstract Excessive floor deformation in underground coal mines, known as floor heave, can cause production delays and thus financial losses. This paper presents parametric studies using numerical models to understand the mechanisms of floor heave in coal mine roadways. An Australian longwall coal mine that experienced significant floor heave in the roadways, where a strong floor unit overlying weak floor units is present immediately below the coal seam, was chosen for field observations. Although the relevant mechanism appears to be buckling, it is uncertain whether the displacement and the failure of the strong unit were caused by horizontal stresses exerted on the uppermost strong unit. The modelling results indicated that the failure of the underlying weak unit induced the upward movement, and subsequent deformation and failure of the overlying strong unit. The floor displacement decreased as the thickness of the overlying strong unit increased. This was attributed to the confinement generated by the strong unit. In addition, the displacement of rock and failure modes simulated by numerical models were found to be sensitive to the deformation modulus. While this numerical study suggests some degree of uncertainty about the estimation of the floor deformation still exists, the failure modes and occurrence of floor heave from numerical models were generally in agreement with the field observations. This study gives insight into floor buckling mechanisms, with the possible involvement of the underlying floor strata below the strong floor unit.
Last. Serkan Saydam(UNSW: University of New South Wales)H-Index: 14
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Abstract Several underground coal mines have reported floor heave associated with the buckling mechanism. However, studies on the coal mine floor, especially the buckling failure mechanism in the floor and relevant analysis techniques, are still insufficient. This paper introduces a new floor classification system, the Coal Mine Floor Rating, based on the underlying failure mechanisms. The new floor mass rating system quantifies the stability of floor strata by considering two main factors: unia...
#1Onur Vardar(UNSW: University of New South Wales)H-Index: 4
#2Chengguo Zhang(UNSW: University of New South Wales)H-Index: 12
Last. Bruce Hebblewhite(UNSW: University of New South Wales)H-Index: 19
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Abstract Coal burst is a manifestation of rapid energy release, which is considered as one of the most critical operational hazards in underground coal mines. This study numerically investigates the effects of discontinuities on the strength and energy release characteristics of coal mass samples under uniaxial compression. The universal distinct element code (UDEC) was used to model pillar-scale coal mass samples that were represented by an assembly of triangular deformable blocks, and pre-exis...
The rock mass deformation modulus is an important parameter for analysis of the mechanical behaviour rock structures. Due to high cost, time consuming activity and difficulties in interpretation of in-situ measurements, a number of empirical methods have been developed to estimate the deformation modulus on the basis of classification systems. However, due to a large number of empirical equations, the practical rock engineers have encountered the question which empirical relationship provides th...
Last. Serkan Saydam(UNSW: University of New South Wales)H-Index: 14
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Abstract This paper presents an overview of the floor heave management at the Glencore Bulga Underground Operations and investigates the contributing factors to the behaviour of the floor. The mine experienced a number of major floor heave events in gateroads on development. As the longwall face approached the roadways, the magnitude of floor heave frequently increased, while new floor heave also developed. Furthermore, severe floor heave events took place along the longwall face. The most obser...
#2Baotang Shen(CSIRO: Commonwealth Scientific and Industrial Research Organisation)H-Index: 23
Brittle rock can fail in tension even when all principal stresses are compressive. The culprit is Poisson’s ratio, but marked stress anisotropy due to a neighbouring free surface, and due to a raised principal tangential stress is also necessary. Extension strain-induced failure causes fracture initiation in tension. Propagation in unstable shear may occur if the tunnels or mine openings are deep enough, and if they are located in hard, brittle, sparsely jointed rock. Both in laboratory uniaxial...
#1Tien Dung Le(UNSW: University of New South Wales)H-Index: 4
#2Joung Oh(UNSW: University of New South Wales)H-Index: 13
Last. Rudrajit Mitra(University of the Witwatersrand)H-Index: 12
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Abstract This paper presents a discontinuum modelling approach to investigate Longwall Top Coal Caving (LTCC) behaviour including stress distribution, coal and rock failures, top coal caving and roof strata rupture, and to analyse the impact of overburden movement on top coal caving. The current model ia successful in using plastic material in a discontinuum code for intact rocks. The model scale is large enough to capture the critical features of LTCC, including steady-state caving of top coal ...
Abstract The progressive process of brittle failure was studied using the results of laboratory damage-controlled tests on the samples of Lac du Bonnet granite and Indiana limestone under uniaxial and triaxial loading conditions. A similar trend of decreasing crack damage stress, peak stress and cohesion and increasing friction angle with increasing damage was observed for both rocks which confirmed the previous findings from the results of uniaxial tests. While the absolute strength of Lac du B...
#1Ted Klemetti(NIOSH: National Institute for Occupational Safety and Health)H-Index: 6
#2Mark Van Dyke(NIOSH: National Institute for Occupational Safety and Health)H-Index: 4
Last. Ihsan Berk Tulu(WVU: West Virginia University)H-Index: 5
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Abstract Several questions have emerged in relation to deep cover bleeder entry performance and support loading: how well do current modeling procedures calculate the rear abutment extent and loading? Does an improved understanding of the rear abutment extent warrant a change in standing support in bleeder entries? To help answer these questions and to determine the current utilization of standing support in bleeder entries, four bleeder entries at varying distances from the startup room were in...
#2Gabriel S. Esterhuizen(NIOSH: National Institute for Occupational Safety and Health)H-Index: 9
Last. Daniel W.H. Su(NIOSH: National Institute for Occupational Safety and Health)H-Index: 4
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Abstract A numerical-model-based approach was recently developed for estimating the changes in both the horizontal and vertical loading conditions induced by an approaching longwall face. In this approach, a systematic procedure is used to estimate the model’s inputs. Shearing along the bedding planes is modeled with ubiquitous joint elements and interface elements. Coal is modeled with a newly developed coal mass model. The response of the gob is calibrated with back analysis of subsidence data...
Anisotropic rock masses, the behavior of which is dominated by closely spaced planes of weakness, present particular difficulties in rock engineering analyses. The orientation of discontinuities relative to an excavation face has a significant influence on the behavioral response. At the present time, discontinuum modeling techniques provide the most rigorous analyses of the deformation and failure processes of anisotropic rock masses. However, due to their computational efficiency continuum ana...
#1Tao Yang(Xi'an University of Science and Technology)
#2Jie Zhang(Xi'an University of Science and Technology)
In order to effectively control the floor heave of water-swelling soft rock roadways, the floor heave mechanism of the roadway was analyzed by taking the Jiaoyun Roadway in the No. 31 Sipan area of Anshan Coal Mine as the research object and taking the loading action and hydraulic action as comprehensive influencing factors. The measure of a pressure-relief slot to prevent floor heave was put forward, the mechanical model of pressure-relief slot was established, and a method to determine the wid...
The safe and efficient mining of deep coal resources is severely restricted by the dynamic disasters caused by high gas and high ground stress. Taking a deep mine in China as the research background, a mechanical model of the front supporting stress with the working face was constructed through theoretical calculations. Based on the limit equilibrium theory, the stress distribution in the plastic zone and the elastic zone of the lateral working face was derived; based on semi-infinite plane mech...
Coal and gas outburst is an important risk faced by coal seam mining in the Huainan region of China. In order to control gas outburst, the gas is predrained by digging a floor gas drainage roadway. To study deformation due to dynamic pressure, the failure characteristics of the floor, and their effect on the stability of the floor gas drainage roadway, a comprehensive monitoring method combining Brillouin optical time-domain reflectometry- (BOTDR-) distributed fiber optics and self-potential exp...
In this paper, a combination of physical model tests and numerical simulations were carried out to explore the overlying strata movement laws, failure mechanism, and cracks evolution of the gob-side entry driven in a thick coal seam. The physical experimental results indicated that the hanging cantilever beam was easily developed above the coal pillar after mining out the 2101 panel, resulting in a larger and stronger stress concentration. The overburden loads acting on the coal pillar can be gr...
#1Jucai Chang(Anhui University of Science and Technology)H-Index: 2
#2Dong Li(Anhui University of Science and Technology)H-Index: 1
Last. Kai He(Anhui University of Science and Technology)H-Index: 1
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With the increase in mining depth, the problem of the floor heave of a roadway is becoming increasingly prominent. Solving this problem for a deep high-stress roadway is the key to ensure safe supply and utilization of coal resources in China. This study investigates the floor heave of a horizontal transportation rock roadway at the depth of 960 m at the Xieyi Mine. A four-way loading simulation test frame similar to the Xieyi Mine was used to reproduce the high-stress environment of a deep road...
Last. Serkan Saydam(UNSW: University of New South Wales)H-Index: 14
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Abstract Several underground coal mines have reported floor heave associated with the buckling mechanism. However, studies on the coal mine floor, especially the buckling failure mechanism in the floor and relevant analysis techniques, are still insufficient. This paper introduces a new floor classification system, the Coal Mine Floor Rating, based on the underlying failure mechanisms. The new floor mass rating system quantifies the stability of floor strata by considering two main factors: unia...