Urban karst collapse hazard assessment based on analytic hierarchy process: An example of southern Wuhan City

Under the background of the increasingly tense of current urban construction land, the karst collapse hazard assessment of the study area is of great significance to the prevention and treatment of karst collapse. The study area is located in the south of Wuhan City. The mainly geological hazard of the study area is karst collapse, and there have occurred 4 karst collapses. By tectonism, concealed karst of the study area shows a nearly east-west banded distribution. Karst types are covered type and buried type, coverage type is Quaternary deposits which directly cover carbonate rocks, and the characteristics of the burial type is red sandstones of Cretaceous Paleogene Gonganzhai Group between carbonate rocks and Quaternary loose accumulation. The study area is in the stage of rapid economic development, and human engineering activities are more active. Based on the formation mechanism and influencing factors of karst collapse in Wuhan City, this paper selects 6 evaluation factors, development degree of karst, soil thickness, layer structure, karst water level fluctuation, well impact and construction intensity. And it uses analytic hierarchy process (AHP) to construct the hazard assessment model of karst collapse in the study area, and divides 183 hazard assessment units of karst collapse. For each unit of karst collapse, hazard comprehensive indexes are calculated, and karst collapse hazard zoning, and the karst collapse hazard grade partition are plotted. The results show that there are 3 high hazard units , 92 medium hazard units , and 88 low hazard units.In this paper, combining the actual situation, using AHP the weight of each factor is determined. Through a number of tests, the judgment matrix is established to prove the consistency. The weights of factors have a higher credibility. And in recent years, 4 karst collapses occurred in high hazard areas, so the result is objective and reasonable, consistent with the historical events. High hazard areas are mainly located in the northwest of the study area. The high hazard area and the medium hazard area accounted for more than half of the total karst area, accounted for about 1/4 of the study area. These issues should receive much attention in the process of urban construction.