,

1. Hefei University of Technology Design Institute (Group) Co., Ltd., Hefei 230000, China; 2. Anhui Urban & Rural Planning and Design Institute, Hefei 230000, China

Abstract Based on the GIS data platform, and taking the spatial analysis as the main means, this paper explored the impact of reclamation in coal mining subsidence area on urban spatial expansion of Huaibei City. The analysis took the time evolution of urban space development as the basis, took the sectors, circle rings and sub-district offices as the basic spatial units. From the aspects of urban expansion rate, expansion direction, function and construction intensity, it analyzed the impact of reclamation on the urban spatial expansion. In addition, it analyzed the correlation between the reclamation utilization of the subsidence area and the changes in spatial expansion. Finally, it summarized the characteristics of the impact.

Key words Huaibei City, Coal mining subsidence area, Urban spatial expansion

1 Introduction

Energy is an important material basis for China’s economic development. For a long time, coal has always accounted for more than 60% of China’s energy consumption[1]. With the exploration and exploitation of coal, China has established a number of coal resource-based cities, which provide important energy support for China’s economic construction[2]. Since coal resource-based cities are developed with the mining of coal resources, they took on scattered distribution. After the completion of the mining of coal resources, large areas of land in the subsidence area become useless or cannot be used as construction land, leading to urban spatial expansion to outward[3]. At present, most of the studies on coal resource-based cities concentrate on industrial transformation and ecology, and studies about coal mining subsidence areas focus on the precondition, administration, and ecology, but there are few studies about the impact of reclamation into the construction land, water area, and green land on the urban areas. The subsidence resulted from coal mining greatly damages original land resources. Especially, the subsidence area in urban areas seriously influences regional natural ecological environment, social stability, and economic development[4].

2 Research area

2.1HuaibeiCityHuaibei City, as a typical resource-based city, is developed with coal mining. The urban area is 285 km2, the mineral resources mainly include coal, kaolin, cement limestone, refractory clay, building stone and gypsum. Since the 1950s, the subsidence of Huaibei City has been started and begun to take shape. In the early days of the foundation of Huaibei City, there were only a few dozen residents in the downtown. There was only one road built by the coal system. By 1980, Huaibei City had become an industrial and mining city dominated by the coal industry. With Xiangshan District as the main area, there were towns scattered around the coal resources. In 1991, the development of Xiangshan District broke through the railway limit, and developed towards the east and south according to the stability of the subsidence area. At present, Xiangshan District, Kuangshanji District and Lieshan District take on C shape and surround Zhahe Coal Field subsidence area[5], as shown in Fig.1.

Data source: plotted by the authors.

Fig.1MapforadministrativedivisionofHuaibeiCity

2.2ReclamationofcoalminingsubsidenceareaSubsidence is a kind of damage caused by ground subsidence and formation of collapse pits in limestone areas and mine development areas. Comprehensive management of coal mining subsidence areas is generally recognized as a global issue[6]. Land reclamation in coal mining subsidence area refers to taking the subsidence land due to coal mining as new type of resources and developing and rebuilding according to the geological conditions, to make it return to available and acceptable natural resources[7]. Before 1980, the land reclamation in the subsidence area of Huaibei City was in a sporadic spontaneous stage, and the reclamation land was mainly used for farmland or construction land. Since 1983, the Huaibei Mining Bureau and Mining Survey Institute of Tangshan Branch of China Coal Research Institute jointly undertook the key project of original Ministry of Coal “Study on Comprehensive Control of Reclamation of Subsidence Area to Farmland”. In the 1990s, Huaibei City formulated the land resource reclamation plan, and gradually summarized the control experience of two levels, three types, and six reclamation modes. Since 1995, Huaibei City has been listed as a national land reclamation demonstration zone by the state for 12 consecutive years. Now, the coal mining subsidence area used in urban reclamation control includes Yangzhuang Coal Mine, Zhuzhuang Coal Mine and Hongyang Coal Mine and other mine areas, located in Xiangshan District, Lieshan District and Duji District. Huaibei City mainly reclaims subsidence land to construction land, green land and waters. After the reclamation, it has established Longhu Industrial Project Area, Vancouver-style City, East Lake Wetland Park and Nanhu Wetland.

3 Methods

3.1ResearchmethodsThrough the survey and interviews in Huaibei Municipal Bureau of Land and Resources, Planning Bureau and Statistics Bureau, and based on the statistical yearbooks for construction of Huaibei City, land reclamation related data and the field survey in Huaibei City, we obtained the basic data and maps of Huaibei City from 1980 to 2016. The urban spatial expansion in each period was based on the current urban overall planning map and correction of the 1∶1 000 scale rainbow remote aerial image. It is a real-time response to urban spatial expansion in each period, and has high credibility and precision. The reclamation construction of the subsidence area in each period was obtained from the land reclamation special plan of the Huaibei Municipal Bureau of Land and Resources, and the 1∶1 000 scale rainbow remote sensing image and department interviews to ensure the reliability of the data.

The analysis took the time evolution of urban space development from 1980 to 2016 as the basis, took the sectors, circle rings and sub-district offices as the basic spatial units. From the aspects of urban expansion rate, expansion direction, function and construction intensity, it analyzed the impact of reclamation on the urban spatial expansion. In addition, it analyzed the correlation between the reclamation utilization of the subsidence area and the changes in spatial expansion. Finally, it summarized the characteristics of the impact.

3.2Analysisofurbanspatialchanges

3.2.1Analysis of urban spatial expansion rate. According to the statistical yearbooks for construction of Anhui Province, we plotted the growth rate curve of the built-up area of Huaibei City from 1986 to 2016. On this basis, according to the relevant data of land reclamation in Huaibei City, we plotted the proportion of land reclamation growth area of Huaibei City in 2002, 2005, 2011 and 2016 to the growth of annual average construction land. Based on the statistics of the urban built-up area and the area of the reclamation region in the built-up area, with the aid of SPSS software, we analyzed the correlation between the two groups of data, to verify the impact of the reclamation area on urban spatial expansion.

3.2.2Analysis of urban spatial expansion direction. With reference to mature equal fan analysis method, using ArcGIS10.2 analysis software, we divided the main urban area of Huaibei City into 16 sector areas through taking the intersection of Huaihai Road and Xiangshan Road as the center. In ArcGIS10.2, we extracted different sector areas, and on this basis, we analyzed the expansion strength of each sector in different periods.

In the analysis, the Urbanization Intensity Index (UII), which is used to compare the intensity and weakness of urban land use expansion in different research periods, essentially applies the land area of each spatial unit to standardize its annual average expansion rate, so as to compare the urban land use expansion rate of different periods[8].

UIIi,t～t+n=[(ULAi,t+n-ULAi,t)/n]×100/TLAi

whereUIIi,t～t+n,ULAi,t+n, andULAi,tdenote the urban expansion intensity index of the spatial unitiin the periodt～t+n, urban built-up area in the yeart+nandt;TLAidenotes the total area of spatial uniti. In the actual calculation, the built-up area is generally expressed and treated with the number of grids.

3.2.3Analysis of urban spatial construction intensity. The development of urban space is a long-term process. At a certain time, the growth of urban construction land reflects the evolution scale and shape of urban land use and spatial structure of a certain period[9]. The evolution of urban land use structure is the accumulation result of construction projects in space. The classification and statistical analysis of urban land use data from 1980 to 2016 reflect the changes in the size and spatial distribution of urban construction land on the time section, showing dynamic characteristics. In this study, we analyzed the current situation data of urban land use in Huaibei City by ArcGIS method. We divided the year 1980-2016 into six periods, divided the urban area into 20 blocks, and analyzed the increase of urban construction land. The formula is △A= (An-A0)/n, where △Adenotes the annual average land use increase of certain block in yearn,Anis the urban built-up area afternyears, andA0is the urban built-up area beforenyears[10].

In order to reveal the spatial distribution characteristics of land use increase, we mainly took the administrative division as the basis. Huaibei City includes Lieshan District, Xiangshan District and Duji District. Xiangshan District includes Xiangshan East Sub-district, Xiangshan West Sub-district, Xiangnan Sub-district, Dongshan Sub-district, Nanli Sub-district, Renmin Road Sub-district, Renwei Sub-district, Sandikou Sub-district, Quyang Sub-district; Duji District includes Gaoyue Sub-district and Kuangshanji Sub-district, while Lieshan District only has one sub-district, namely, Yangzhuang Sub-district. In order to cover the entire urban planning area and ensure the integrity of the construction area, we added eight virtual sub-districts, in total 20 blocks (Table 1).

Table1Divisionofsub-districtsofHuaibeiCity

District No.Sub-district nameDistrict No.Sub-district nameXiangshan District1Xiangshan West Sub-districtXiangshan District13Quyang Sub-district2Xiangshan Eest Sub-district14Daizhuang Virtual Sub-district3Xiangnan Sub-districtDuji Sub-district 8Gaoyue Sub-district4Dongshan Sub-district 9Kuangshanji Sub-district5Nanli Sub-district 15Longhu Industrial Virtual Sub-district6Renmin Road Sub-district 19Duji Industrial Virtual Sub-district7Renwei Sub-district Lieshan District 16Yangzhuang Sub-district10Fenghuangshan Virtual Sub-district 17Xincai Virtual Sub-district11Qugou Virtual Sub-district 18Longjishan Virtual Sub-district12Sandikou Sub-district 20Economic Development Virtual Sub-district

Data source: prepared with reference to theMapofHuaibeiCity1∶120 000.

3.4ComparisonoftheimpactofurbanareaexpansionontheurbanareabeforeandafterreclamationAt present, there are few studies about urban spatial expansion from the perspective of re-use of subsidence areas, especially the impact by the spatial quantification method. In this study, in the urban spatial expansion rate, with the aid of SPSS tool, we compared the urban built-up area and the annual growth rate of the reclamation area of the subsidence area, and made a correlation analysis. As to the study of the difference of urban expansion space, through the divided 16 sector areas, we carried out the study from horizontal and vertical dimensions. In the horizontal direction, we compared the difference or urban spatial expansion in different directions; in the vertical direction, we compared the difference in spatial expansion in different periods. As to the urban land use increase, taking the 20 administrative districts, we mainly studied the green land and water area of subsidence area, and analyzed the impact of attraction of green land and water area on the urban expansion based on actual situations of Huaibei City. Finally, on the basis of these three impact analyses, we made a comprehensive judgment of the positive or negative effects of reclamation of subsidence area on the urban spatial expansion.

4 Results

4.1Impactsofreclamationofsubsidenceareaontheurbanspatialexpansionrate

4.1.1Analysis of urban spatial expansion rate. According to Fig.2, we divided the urban built-up area of Huaibei City into four stages: (i) expansion rate decline stage (1985-1991): the expansion rate was declining to 9.29% in 1991; (ii) rapid expansion stage (1992-2004): the expansion rate rapidly rose to 36.42%; (iii) decline stage (2005-2010): the expansion rate dropped to -2.75%; (iv) growth with fluctuation (2011-2016): in 2011 and 2014, the expansion rate rose to 25.25% and 10.94% respectively, and in other years, the expansion rate rose slightly or became stagnant.

4.1.2Proportion of reclamation of subsidence area to the urban space. From the proportion of annual growth of urban built-up area, in 2002-2005, 11.5% land growth came from the reclamation of subsidence area, mainly concentrated in Longhu Industrial Park, which is an industrial park built in the subsidence area. By 2005-2011, the proportion had reached 53.0%. More than half of the newly increased land in urban areas came from the reclamation of subsidence area. During this period, Longhu Industrial Park continued to expand, and Huaibei City also expanded to the south to establish new areas, including the Vancouver-style City, Emerald Island, Times Park and Kouzi International Hotel. In 2011-2016, 26.1% of the land use growth came from the reclamation of the subsidence area, which was mainly along the south of Xiangshan Road, connecting the middle area of Lieshan clusters and Xiangshan clusters (Fig.3).

Data source: the statistical yearbooks for construction of Anhui Province.

Fig.2CurveforexpansionrateofurbanconstructionareainHuaibeiCityin1985-2016

Data source: plotted by the authors.

Fig.3Proportionofincreaseofreclamationofconstructionareatototalconstructionareaincreasein2002-2016

4.1.3Correlation between reclamation of subsidence area and urban built-up area expansion. Based on the statistics of the urban built-up area and the area of the reclamation region in the built-up area, with the aid of SPSS software, we analyzed the correlation between the two groups of data, and obtained following results: in 2002-2016, the correlation coefficient of construction area and reclamation of construction area was 0.994, showing extremely high correlation. The results indicated that there was a high correlation between the number of urban spatial expansion and number of reclamation of construction area. In other words, the reclamation greatly promoted the urban spatial expansion, as shown in Table 2.

Table2Correlationbetweenthetotalconstructionareaandtheareaofreclamationofconstructionarea

Total construction areaArea of reclamation of construction areaArea of construction region Pearson correlation 10.994**Significance (two-sided)-0.006N44Area of reclamation regionPearson correlation 0.994**1Significance (two-sided)0.006-N44

Note:**denotes significant correlation at 0.01 level (two-sided).

4.2Impactsofreclamationofsubsidenceareaontheurbanspatialexpansiondirection

4.2.1Direction characteristics of urban expansion. According to Fig.4 and Table 3, during the period of 1980-1984, the rapid urban expansion was concentrated in NE direction and SW direction of non-subsidence area. The data were discrete, and the coefficient of variation was 0.80. The relative fluctuation range of the data was not large, indicating that the urban expansion index in all directions was relatively low and there was certain difference. During the period 1984-1995, from the perspective of the expansion type, the rapid urban expansion was concentrated in the E direction of the subsidence area. The mean value of this time period was 0.05, the standard deviation was 0.06, the data were slightly discrete and the urban expansion was slowly growing. During the period of 1995-2002, the rapid urban expansion was concentrated in the non-subsidence area, steady expansion only occurred in SSW direction of non-subsidence area and the E direction of subsidence area. In this period, the average value of all directions was 0.07, and the standard deviation was 0.13, the data were more discrete, the coefficient of variation was 1.86, and the direction of urban expansion was obvious. During the period of 2002-2005, the rapid urban expansion was concentrated in the S direction of the subsidence area. Urban expansion in other directions was restricted by the subsidence area. Compared with the previous period, the data were much more discrete, and the coefficient of variation was 1.71, and the range of data fluctuation was large, and the difference in the intensity of each direction was significant. During the period of 2005-2011, the rapid urban expansion was concentrated in the E direction of the subsidence area, and the direction of urban expansion was obvious, and the range of data fluctuation was still relatively large. During the period of 2011-2016, the rapid urban expansion was concentrated in the SSE direction in the subsidence area. Due to the limitation of the subsidence area in the center, the filling between the groups was still zero, the anisotropy of urban expansion was obvious, the coefficient of variation was 1.84, and the relative fluctuation range of the data was very large.

Data source: plotted by the authors.

Fig.4Radarmapoflandexpansionintensityindifferentdirectionsatvariousstagesin1980-2016

Table3Statisticsoflandexpansionintensityindifferentdirectionsin1980-2016

YearExtreme difference Max.Min. Mean valueStandard deviationCoefficient of variation1980-19840.440.440.000.160.130.801984-19950.180.17-0.010.050.061.161995-20020.520.45-0.070.070.131.862002-20051.441.440.000.260.441.712005-20111.251.20-0.050.270.341.252011-20161.391.33-0.060.200.331.84

4.2.2Impact of reclamation of subsidence area on the urban expansion direction. According to Table 4 and Fig.5, it can be seen that the urban construction land used in the subsidence area of Huaibei City was mainly concentrated in Xiangshan District and Duji District. Since the area where the reclamation was used for construction did not involve the Lieshan District, its distribution quadrant was only NEE, E, SEE, SE, SSE and S. From this point, its impact on the overall direction of the urban expansion was restricted. We analyzed the correlation between the changes in urban construction area and reclamation construction area in these six directions, and obtained the following results: in 2002-2005, the correlation coefficient between the changes in urban construction area and reclamation construction area was -0.330; in 2005-2011, the correlation coefficient was 0.768; in 2011-2016, the correlation coefficient was -0.817. Results indicated that the subsidence area was influenced by geological factors and other factors, and restricted by the location of subsidence area, especially Huaibei City was not centralized cluster distribution, its three clusters developed separately, the development direction was different, thus the impact on outward expansion was small.

Table4Classificationoflandexpansiontypesin1080-2016

YearSubsidence areaRapid expansionSteady expansionLagging expansionNon-subsidence areaRapid expansionSteady expansionLagging expansion1980-1984-SNEEESEESE SSENESWSSWWNWWNWNNWNNNESWW1984-1995ENEESEESSESSE-SWSSWSWWWNWWNWNNWNNNENE1995-2002-ENEESEESESSESWSSWSWSWWNWWNWNNWNNNENW2002-2005SSSESESEEENEE--WNWWNWNNWNNNENESSWSW2005-2011ESESSENEESEES--SSWSWSWWWNWWNWNNWNNNENE2011-2016SSENEEESEESES--SSWSWSWWWNWWNWNNWNNNENE

4.3Impactsofreclamationofsubsidenceareaonthespatialconstructionintensity

4.3.1Analysis of the spatial construction intensity. According to Fig.6, it can be seen that during the period of 1980-1984, urban land use growth was mainly concentrated in the core area and the southwestern region. Due to the small size of Huaibei City at that time, the construction volume did not extend to the periphery. During the period of 1984-1995, the growth of urban land use was relatively slow, with increase in only two small blocks of the inner city. During this period, only Xiangnan Sub-district grew at an average annual rate of 10-20 ha, and the large-scale built-up area of the urban area increased at the annual rate below 10 ha. During the period of 1995-2002, the growth of the built-up area was extended from the points concentrated in the inner city to the outside. The growth rate changed from small increase to large increase, mainly concentrated in the southwest corner and the northeast corner, extending to the east and west sides. In the central axis, it was zero or negative growth. Sub-districts with sharp growth include Xiangnan Sub-district and Sub-district. During the period of 2002-2005, the growth of each block suddenly increased, and the growth axis shifted from east-west direction to north-south direction, and the inner city showed a sharp growth. Sub-districts with sharp increase include Nanli Sub-district, Renmin Raod Sub-district, Gaoyue Sub-district, Yangzhuang Sub-district, and Duji Industrial Virtual Sub-district. Sub-districts with rapid increase include Renwei Sub-district and Longhu Industrial Virtual Sub-district. During the period of 2005-2011, urban growth gradually shifted from the core area to the inner city area. The core area increased sharply and grew slightly, gradually shifting to zero or negative growth, while the inner city showed a small increase. In the period of 2011-2016, the urban construction increase had spread to the edge of the city, but it was still dominated by point blocks. Sub-districts with sharp increase include Kuangshanji Sub-district, Fenghuangshan Virtual Sub-district, and Economic Development Sub-district, and sub-district with rapid increase was Duji Industrial Virtual Sub-district.

Data source: plotted by the authors.

Fig.5Radarmapoftheexpansionintensityofthereclamationconstructionlandin2002-2016

4.3.2Impacts of reclamation on urban spatial construction increase. According to Fig.7 and Table 5, before 2002, due to the technical and cognitive limitations of the reuse of subsided land at that time, urban planning did not consider the subsided land into the entire urban land use system, and the urban expansion deliberately avoided the subsidence area. In the period when the land use in the urban core area reached the bottleneck, Huaibei City had only two large-scale growth sub-districts, Xiangnan Sub-district and Nanli Sub-district. During the period of 2002-2005, the number of urban sharp growth blocks increased by five, of which the sub-districts of the subsidence area occupied three. The construction area of Yangzhuang Sub-district had the fastest growth, with an average annual growth rate of 149.23 ha. During this period, the subsidence area was included into the urban area. First, Lieshan Sub-district took advantage of large water area, high water quality, and deep water of the subsidence area, and established Lieshan Park and South Park with beautiful environment, complete facilities and complete functions in Yangzhuang Sub-district, created excellent living environment, which improved the grade and modernization level of old downtown, accumulated popularity, and promoted sharp growth of the construction of Yangzhaung Sub-district. During the period of 2005-2011, four sub-districts realized sharp growth. The fastest growing blocks changed from the southwest corner to the northeast corner. Although Yangzhuang Sub-district still maintained an average annual increase of 48 ha, Longhu Industrial Virtual Sub-district had the highest increase. Although the sub-district of newly built East Lake Park and Huantan Park had no bigger appeal than Lieshan Park and South Lake Park,

Data source: plotted by the authors.

Fig.6Distributionofconstructionintensityincreaseofsub-districtsinHuaibeiCityin1980-2016

Data source: plotted by the authors.

Fig.7Mapfordistributionofsub-districtswithreclaimedlakesandgreenlandinHuaibeiCityin2002-2016

Renwei Sub-district situated between these two parks realized annual growth of 52.4 ha, so East Lake Park and Huantan Park still had certain agglomeration ability. During the period of 2011-2016, the number of sub-districts with sharp growth reduced to three, namely, Kuangshanji Sub-district, Fenghuangshan Sub-district, and Economic Development Virtual Sub-district. Especially, Kuangshanji Sub-district showed strong increase (by 68.43 ha). During this period, with the gradual improvement of the infrastructure of East Lake Park, Kuangshanji Sub-district became the key development sub-district, and the demand for commercial and residential buildings was large. The actual transaction blocks for commercial and real estate development were concentrated here. The development of East Lake Wetland Park in the east promoted the development of the entire city. From the above analysis, the large changes in the land use increase in Huaibei City are greatly associated with the parks, lakes and public green space, mainly in the parks and lakes, and the lake attracted the core area, which drives the development of Huaibei City to the south. The size of lake water directly influences the growth rate of urban construction.

Table5Comparisonofsub-districtswithsharpincreaseandreclamationofwaterareaandgreenland

YearSub-districts withsharp increaseSub-districts with reclamationof water area and green land2002-20055, 6, 8, 16, 198, 9, 6, 162005-20117, 15, 16, 178, 9, 6, 16, 152011-20169, 10, 208, 9, 6, 16, 15, 14

5 Conclusions and discussions

5.1ConclusionsThe reuse of subsidence area as construction land promotes the increase of urban development and makes spatial expansion of Huaibei City show significant leaping characteristics, but the impacts on outward urban expansion are small. Besides, the reclamation of subsidence area into parks, lakes, and green land influences the distribution of urban landscape center, and accordingly influences the increase of surrounding construction. Therefore, it is recommended to make rational use of the reclaimed land in the subsidence area. To reclaim the subsidence area to construction land, it is recommended to make effective consolidation, make unified planning, cultivate the cluster center, and open the main road and expressway between the clusters. For the redevelopment of the subsidence area of the cluster center, it is recommended to take the economic growth as the goal, the development sequence should be strictly controlled at the edge of the cluster. To reclaim the subsidence area to the green land and lakes, it is recommended to form excellent urban landscape and ecological environment. According to water body, it is feasible to divide water body into different recreation functions, and the development should strictly control the green land boundary and regulate the development and construction.

5.2DiscussionsIn this study, we analyzed the direction of urban expansion and the direction of reclamation for the construction land during the period of 2002-2016. From the impact of the reclamation area on the direction of urban expansion, the impact of the three stages is small, and the impact on urban expansion only remains in the direction. Generally, from the direction of urban expansion, the subsidence area is mainly negative. Despite the reclamation practice, the reclamation is restricted by geological conditions, and the reclamation land for construction can not keep up with the speed of urban development. At present, the construction space in Huaibei City has grown rapidly, and the local development demand has broken through the scope of urban planning areas, especially the development of peripheral regions along the roads has formed enclave outside the planning scope. This indicates that the reclamation of subsidence are to construction land can not change the pattern of urban spatial development of Huaibei City.

From the comparison between sub-districts with rapid increase of construction and sub-districts with reclamation of subsidence area to parks and lakes, and public green land, the large changes in the land use increase in Huaibei City are greatly associated with the parks, lakes and public green space, mainly in the parks and lakes, and the lake attracted the core area. Relying on the congenital advantages of subsidence area, it is expected to form lakes and wetland, and form excellent urban landscape and ecological environment. Ecological water surface can form the attraction center, increase the construction volume of surrounding land, and accordingly promote construction space of Huaibei City to move to the east and south. In comparison, the promotion capability of Lieshan Park and South Lake Park is significantly greater than that of East Lake Park and Huantan Park. Thus, it can be seen that the size of lake water directly influences the growth rate of urban construction.

In the process of reclamation and reuse of subsidence area, Huaibei City should make effective consolidation and make unified planning combining the scattered land of Xiangshan, Duji, and Lieshan cluster. From the perspective of traffic, the traffic system is not complete because the subsidence area is still not taken as a part of the urban traffic system. According to the present road network pattern, except Xiangshan cluster that has basically established the road network, Lieshan and Duji clusters lack main roads connecting with other clusters. Therefore, in the reclamation and reuse of the subsidence area, it is firstly recommended to improve the engineering reclamation technology of road, to realize connection of main roads and expressways, especially those between clusters.

For the subsidence area of different locations, the reuse should take different measures. For the subsidence area in the center of cluster, it is recommended to take the economic growth as the goal, and impose taxation on coal mining enterprises to conduct land consolidation and reclamation in strict accordance with state laws and regulations. Besides, it is recommended to expand the channels, improve the investment return mode, to attract other social funds. The subsidence area redevelopment at the edge of cluster should strictly control the development sequence and strictly prohibit the sporadic construction[11].