LAUSR

(China National Coal Association, 2018), making it the largest coal producer in the world, accounting for almost half of total world coal production. Coal production and distribution play a vital role in the energy industry of China. However, entire overlying strata, from coal seam to surface, are disturbed as a result of long-term, high-intensity and large-scale mining, causing surface subsidence. This results in groundwater loss, surface desertification, vegetation loss, and mud-rock flows. These issues have become topics of common concern throughout society. According to related research results (Liu 2008), the area of surface subsidence caused by coal mining in China has reached about 600 000 ha, some 0.2 ha (and up to 0.42 ha) of surface subsidence for every 10 000 t of coal produced. Surface subsidence disasters not only damage buildings, water conservancy, transportation infrastructure, and farmland, but also cause adverse effects on individual and community lifestyles, environmental hygiene, and economic development. Deterioration of the ecological environment in mining areas has a long history and is very harmful (Lu, 2015). Surface subsidence is an extremely important control index for underground excavations. Many experts and scholars have devoted resources to the research and remediation of damage caused by coal mining from the surveying, numerical simulation, mathematical, mechanical, geological, and mining engineering points of view. These studies have revealed general laws of mining subsidence (Hu, 2012). The most prominent characteristic of these is that surface subsidence has an obvious time-dependency, and may continue for several months, or even years, from the start to the end of surface movements. Since the 1970s, with the wide application of computer methods, numerical simulation has been increasingly applied in the calculation of mining subsidence and the analysis of subsidence mechanisms, and many experts and scholars have undertaken research in this field, such as Dahl and Choi (1981). The West German scholar Kratzsch (1974) summarized methods of predicting coal mining subsidence in his book ’Mining Damage and Protection’. Ma and Yang (2001) researched the spatial and temporal effects of rock movement using the discrete element method. Cui and Deng (2017) carried out a real-time displacement analysis of surface movement and deformation for the main section of a coal mine, and studied mining subsidence utilizing a rheological model. Surface subsidence continually changes during the exploitation of a mining face; Changes in subsidence-field surface movement in shallow-seam coal mining