Suitability evaluation on construction of planned urban areas in Guilin based on AHP method and GIS platform.

The engineering construction of karst city is often affected by karst geological hazards. Guilin City is a typical representative of karst city; therefore, we should consider the influence of karst hazards when analyzing the suitability for engineering construction in planned urban areas of Guilin. In this study, we established a method for evaluating the construction suitability based on the analytic hierarchy process (AHP) on the geographic information system (GIS) platform. Firstly, the landform of planned urban areas in Guilin is mainly composed of peak-cluster depression, peak-forest valley, peak-forest plain, isolated peak plain, karst-ridge valley, karst-hill plain, low mountain with steep hillslope, hill, hill with gentle slope, and undulating hills. The areas intensely developed with karst are mainly located along the banks of the Lijiang River and in the Lingui district. The areas with karst development at a medium level are located in the middle and southwestern parts of Guilin City and on the periphery of the Lijiang River banks. The areas with weak karst development are mainly located at the Yanshan district, Dingjiang town, and southwestern Lingui district. The groundwater types of the study area are mainly composed of carbonate karst water, impure carbonate cave-fissure water, and clastic bedrock fissure water. For the suitability evaluation of engineering construction in planned urban areas of Guilin, the topographic slope, geomorphic unit, bearing capacity of soil foundation, bearing capacity of rock foundation, special soil distribution, soil thickness, soil structure, groundwater depth, surface water system, karst influence, and fault factors are selected as evaluation indexes, all of which have passed the consistency test of judgment matrix. The weight of these eleven evaluation indexes was calculated by AHP. Then, the engineering construction suitability index (P) was computed from multi hierarchy evaluation with AHP. The P values can be classified as P≥5.00, 2.50≤P<5.00, 1.00≤P<2.50, and P<1.00, which may respectively fall into the category of suitable area, relatively suitable area, poorly suitable area, and unsuitable area for engineering construction. The zoning of planned unban areas in Guilin was visualized based on the suitability for engineering construction on the GIS spatial platform. Finally, in terms of the zoning based on suitability for engineering construction, six sites were chosen and were verified that the zoning by AHP method is consistent with that by field engineering drilling surveys. The consistency may indicate the reliability of APH method with GIS platform. Main conclusions can be drawn as follows,(1) The impact indexes of suitability for engineering construction of the study area include topography (slope degree and geomorphic unit), engineering geological conditions (bearing capacity of soil foundation, bearing capacity of rock foundation, special soil distribution, soil thickness and soil structure), hydrological conditions (groundwater depth and surface water system), and unfavorable geological condition (karst influence and fault factors). (2) Planned urban areas in Guilin are generally suitable for engineering construction, because suitable and relatively suitable areas account for 3.1% and 48.3% of the total area respectively, which can meet the land use needs of recent urban development planning and major infrastructure projects. However, the poorly suitable areas account for 11.4%, which are unsuitable for large-scale engineering construction and require necessary engineering treatment in practical construction. Unsuitable areas account for 37.2%, mostly located at medium-sized mountain, peak-cluster, and isolated peak. The site selection of major construction should be avoided in the unsuitable area. (3) If the major construction site is selected in a poorly suitable area, measures should be taken to prevent and control the existing and induced geological disasters and uneven settlement of foundations. The unsuitable area is proposed to be planned as the ecological land, which can serve as the ecological barrier for Guilin. [ABSTRACT FROM AUTHOR]