Main Article Content
Face spall in moderate strength coal seam occurs less frequently but can be more severe and takes a longer time to remedy compared to face spall in the weak coal seam. This paper presents a field investigation of face spall in moderate strength coal seam at Face I-8-1, Vang Danh coal mine, Quang Ninh coal field, Vietnam. The leg pressure of shield support and face condition were monitored within two months, and on-site remedial measures to the spall were discussed.
The monitoring results confirmed that the front and rear leg pressure profiles are consistent with world-wide observations. The coal face condition in actual operation was found to be more stable than that in project design. The face spall occurred along face dip direction, but mostly in small extent of less than 0.5 m deep and during transitional time between working shifts. Proper ground control near gate ends by using higher capacity shield supports and supplemental hydraulic props was identified to improve face stability in the area. On-site remedial measures proved their efficiency in small to moderate face spall extent. For main roof rupture-associated face spall, technical measures have been applied but they need further investigation to clarify their effectiveness.
The paper’s results can be consulted to improve longwall face stability control in similar coal
 W. B. Guo, C. Y. Liu, G. W. Dong, W. Y. Lv, Analytical Study to Estimate Rib Spalling Extent and Support Requirements in Thick Seam Mining, Arabian Journal of Geosciences, Vol. 12, 2019,
pp. 276-276, https://doi.org/10.1007/s12517-019-4443-8.
 D. Kong, Y. Liu, S. Zheng, Sensitivity Analysis of Influencing Factors and Control Technology for Coalface Failure, Arabian Journal of Geosciences, Vol. 12, 2019, pp. 550-550, https://doi.org/10.1007/s12517-019-4714-4.
 R. Frith, Structural Engineering Principles in Coal Mine Ground Control-The Common Link between Empirical Models, Numerical Models, and Practical Solutions, Advances in Coal Mine Ground Control, Woodhead Publishing, Duxford, 2017, pp. 67-92.
 D. Pappas, C. Mark, Roof and Rib Fall Incident Trends: A 10-year Profile, SME Transactions Volume 330, Society for Mining, Metallurgy and Exploration, Inc., New York, 2011, pp. 462-478.
 S. Prusek, S. Rajwa, A. Wrana, A. Krzemień, Assessment of Roof Fall Risk in Longwall Coal Mines, International Journal of Mining, Reclamation and Environment, Vol. 31, 2017,
pp 558-574, https://doi.org/10.1080/17480930.2016.1200897.
 S. R. Islavath, D. Deb, H. Kumar, Numerical Analysis of A Longwall Mining Cycle and Development of A Composite Longwall Index, International Journal of Rock Mechanics and Mining Sciences, Vol. 89, 2016, pp. 43-54. https://doi.org/10.1016/j.ijrmms.2016.08.003.
 L. T. Dung, B. M. Tung, P. D. Hung, V. T. Tien,
D. V. Chi, A Modelling Technique for Top Coal Fall Ahead of Face Support in Mechanised Longwall Using Discrete Element Method, Journal of Mining and Earth Sciences, Vol. 59, pp. 2018, pp. 56-65.
 L. T. Dung, V. D. Hieu, N. A. Tuan, Characteristics of Top Coal Fall in front of Face Support in Longwall: A Case Study, Vietnam Journal of Earth Sciences, Vol. 42, 2020, pp. 152-161, https://doi.org/10.15625/0866-7187/42/2/14955.
 J. M. Galvin, Ground Engineering - Principles and Practices for Underground Coal Mining, Springer International Publishing, Cham, 2016.
 R. C. Frith, A. M. Stewart, D. Price, Australian Longwall Geomechanics - A Recent Study, 11th International Conference on Ground Control in Mining, Australasian Institute of Mining and Metallurgy, The University of Wollongong, 1992, pp. 131-139.
 V. T. Tien, D. A. Son, Analysis of Causes of Face Fall and Roof Fall in Fully-Mechanised Longwalls and Preventing Measures, Mining Industry Journal, Vol. 6, 2014, pp. 26-29 (in Vietnamese).
 L. D. Nguyen, D. V. Cuong, L. D. Vinh,
T. M. Tien, L. T. Chung, T. Q. Tuan, Study on Application of Water Injection to Improve Coal Cohesion at Unstable Area and Weak Coal at Khe Cham III Coal Mine, Mining Technology Bulletin, Vol. 8, 2016, pp. 1-6 (in Vietnamese).
 Vinacomin Institute of Mining Science and Technology, Investment and Mining Project for Level 0 -:- -175 Vang Danh Site, Vang Danh Coal Mine, Hanoi, 2016 (in Vietnamese).
 Vang Danh Coal Company, Mining Passport for Face I-8-1, Quang Ninh, 2018 (in Vietnamese).
 Y. Cai, B. Hebblewhite, U. Onder, B. Xu, M. Kelly, B. Wright, I. Kraemer, Application of Longwall Top Coal Caving to Australian operations, CSIRO Exploration and Mining, Queensland, 2004.
 D. Yun, Z. Liu, W. Cheng, Z. Fan, D. Wang,
Y. Zhang, Monitoring Strata Behavior due to Multi-slicing Top Coal Caving Longwall Mining in Steeply Dipping Extra Thick Coal Seam, International Journal of Mining Science and Technology, Vol. 27, 2017, pp. 179-184. https://doi.org/10.1016/j.ijmst.2016.11.002.
 A. K. Verma, D. Deb, Longwall Face Stability Index for Estimation of Chock-Shield Pressure and Face Convergence, Geotechnical and Geological Engineering, Vol. 28, 2010, pp. 431-445. https://doi.org/10.1007/s10706-010-9303-y.
 G. S. P. Singh, U. K. Singh, Prediction of Caving Behavior of Strata and Optimum Rating of Hydraulic Powered Support for Longwall Workings, Int. J. Rock Mech. Min. Sci., Vol. 47, 2010, pp. 1-16, https://doi.org/10.1016/j.ijrmms.2009.09.001.
 Ha Lam Coal Company, Report on Mechanisation of Underground Coal Mining, Quang Ninh, 2018 (in Vietnamese).
 Quang Hanh Coal Company, Report on Mechanisation of Underground Coal Mining, Quang Ninh, 2018 (in Vietnamese).
 R. C. Frith, A Holistic Examination of The Load Rating Design of Longwall Shields After More Than Half A Century of Mechanised Longwall Mining, International Journal of Mining Science and Technology, Vol. 25, 2015, pp. 687-706, https://doi.org/10.1016/j.ijmst.2015.07.001.