{"id":30411,"date":"2019-03-12T07:44:04","date_gmt":"2019-03-12T07:44:04","guid":{"rendered":"https:\/\/blogs.agu.org\/landslideblog\/?p=30411"},"modified":"2019-03-12T07:58:13","modified_gmt":"2019-03-12T07:58:13","slug":"chengchao-iron-ore-mine-1","status":"publish","type":"post","link":"https:\/\/blogs.agu.org\/landslideblog\/2019\/03\/12\/chengchao-iron-ore-mine-1\/","title":{"rendered":"Chengchao iron ore mine: severe subsidence induced by mining in China"},"content":{"rendered":"

Chengchao Iron Ore Mine: severe subsidence induced by mining in China<\/h4>\n

There is a nice article in a recent edition of the journal Engineering Geology<\/a><\/em> (Xia et al.<\/em> 2019<\/a>) examining subsidence induced by the Chengchao iron ore mine, which is located in Ezhou City, Hubei Province, China.\u00a0 The paper describes the dramatic subsidence structures and explains their formation.\u00a0 The subsidence pits are remarkable – this is a recent Google Earth image that shows the craters that have formed:-<\/p>\n

\"Chengchao

Subsidence features at the Chengchao iron ore mine in China. Image via Google Earth, collected in 2018.<\/p><\/div>\n

.<\/p>\n

The location is 30.319, 114.918 if you want to take a look.\u00a0 Mining started at the Chengchao iron ore mine in 1969, with the mining method focusing on sub-level caving.\u00a0 Subsidence started to be observed in the construction period for the mine (between 1958 and 1969), and it has extended thereafter. \u00a0 The subsidence is manifested on the surface primarily through the formation of large, deep pits, shown in the image below from Xia et al.<\/em> (2019)<\/a>:-<\/p>\n

\"Chengchao

Subsidence pits formed at the Chengchao iron ore mine in China. Figure from Xia et al.<\/em> (2019)<\/a>.<\/p><\/div>\n

.<\/p>\n

Xia et al.<\/em> (2019)<\/a> note that subsidence has occurred over an area measuring 1200 m x 300 m.\u00a0 Whilst the pits are the obvious manifestation of the subsidence, the authors note that the ground between the craters has also subsided substantially.\u00a0 In the centre of the worst of the pits the total vertical movement is up to 60 metres!\u00a0 The largest of the pits have a diameter of about 70 metres, and subsidence is continuing to develop across the area, with smaller, new pits forming in addition to the broad subsidence bowl.<\/p>\n

Interestingly, Xia et al.<\/em> (2019)<\/a> conclude that the processes of subsidence at Changchao iron ore mine are complex.\u00a0 The geology consists of a faulted mixture of granite, marble, diorite and hornstone.\u00a0 Some of the collapses are located within the karst (marble) rocks, primarily as a result of changes in the groundwater conditions during dewatering for the mine.\u00a0 But in many other cases the caving technique has removed support from the overlying rocks, which have collapsed into the void. This process is ongoing – compare the image below, from 2012, with the one at the top of the page (from 2018).\u00a0 Several new pits have developed, and others have enlarged substantially:-<\/p>\n

\"Chengchao

Subsidence features at the Chengchao iron ore mine in China. Image via Google Earth, collected in 2012.<\/p><\/div>\n

.<\/p>\n

The authors note that the subsidence has led to expensive works to relocate mining infrastructure.\u00a0 Fortunately, there are few non-mining assets in this area.<\/p>\n

Reference<\/h4>\n

Kaizong Xia, Congxin Chen, Yun Zheng, Haina Zhang, Xiumin Liu, Yangyang Deng and Kuoyu Yang 2019.\u00a0 Engineering geology and ground collapse mechanism in the Chengchao Iron-ore Mine in China<\/a>. Engineering Geology<\/em>,
\n249<\/strong>, 129-147. https:\/\/doi.org\/10.1016\/j.enggeo.2018.12.028<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"

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