Abstract
Over last 40 years, rockbursts have been responsible for thousands of accidents and fatalities in nearly 140 underground coal mines in China. Therefore, rockbursts have become one of the most significant safety concerns in Chinese coal industry. In recent years, governmental agencies, research institutes, and coal companies have exerted great efforts studying the rockburst phenomena. State Administration of Coal Mine Safety (SACMS) revised coal mine safety regulations, re-formulated relevant coal mine design standards, and put forward more stringent requirements in terms of hazard assessments, rockburst monitoring, regional precautions, local preventions, result evaluation, and safety protection. Professionals from research institutes and universities analyzed rockburst occurring mechanism, and agreed that the rockburst phenomena is an abrupt destruction of coal/rock mass after its strength capacity being exceeded by corresponding state of stress. Several rockburst prevention methods have been developed based on stress control theory, and were applied to Chinese coal mines. Regional stress control methods, such as optimized mine layout, sacrificial protective mining in selected seam, and so on, were utilized to mitigate potential rockburst conditions. In addition, local stress control methods, such as stress relief via deep borehole drilling, roof strata weakening via pre-mining fracturing or blasting, coal seam stress relief via controlled bursting, coal seam softening via water injection, floor strata blasting, hydro-fracturing, and so on, have been utilized to reduce high stress concentrations, which could otherwise induce catastrophic rockbursts.
1. INTRODUCTION
Coal mining is essential to economy development in China. Per recent official statistics, about 2/3 primary energy production and consumption relied on coal in China. In 2013, total Chinese coal production exceeded 3,860 million tons, and it was projected that coal will remain as main energy source in China within next 50 years.
However, shallow coal reserves have almost been depleted after decades of mining. Currently, average mining depth of underground coal mines in China is about 600 m. Furthermore, 47 coal mines, such as Suncun Mine in Shandong province, Zhangji Mine in Jiangsu province, and No. 10 Mine of Pingdingshan Coal Mine Group in Henan province, currently extract coal reserves at a mining depth greater than 1,000 m. As a matter of fact, Suncun Mine has become the deepest coal mine in Asia, with a maximum depth of cover approximately 1,501 m.
