Studies On The Characteristics Of Collapse Mound Erosion And Monitoring Data Management System In Southeast Hubei

Collapse mound erosion is a serious erosion phenomenon that the weathering crust of hillside soil mass or rock mass decomposes, collapses and accumulates under waterpower and gravity, and is a common and special soil erosion in the granite area of South China. As a means of accelerated soil and water loss, the capability of collapse mound erosion is strong, and its forms of damage are various and very destructive. With the economic development of all provinces (autonomous regions) in the collapse mound area, the losses and damage caused by collapse mound erosion are more and more serious, and bring about serious obstacles and constraints to the sustrainable development of the local social economy. Therefore, carrying out collapse mound erosion monitoring is necessary. For this reason to study and explore the development regularity and erosion process of collapse mound erosion, it’s of great theoretical and practical significance for richening the theory, prediction and management of collapse mound erosion.This paper focused on the typically collapse mounds of Wuli and Chengfeng in Tongcheng County, southeast Hubei, combination with the methods of experimental analyses in laboratory and field observation, GPS RTK monitoring to study the characteristics of the collapse mound erosion in southeast Hubei, meanwhile developing the collapse mound monitoring data management system to manage and count the data. The main conclusions are as follows:(1) Through the study of collapse mound soil physicochemical properties, a preliminary analysis showed that:the cement such as cray, organic matter, free iron oxide contained in eluvial horizon and illuvial horizon is more, soil bulk density is bigger, the stability of soil structure is stronger, but the permeability is low. With bigger soil cohesion, the layers have strong shearing strength and soil erosion resistance. On the contrary, the cement contained in the underlying transition horizon and parent material horizon is less, the soil structure is loose, and permeability is good. The layers with less soil cohesion are easily eroded by water. Once eluvial horizon and illuvial horizon are damaged or eroded, transition horizon and parent material horizon are eroded by the waterfall. So that the collapsed wall becomes exposed slope pattern, then occurs gravitational collapse. It is known that transition horizon and parent material horizon have weak mechanical properties. Because of the characteristics of weathered granite, it determines that collapse mounds are generally developed in the granite area.(2) In the test regions, the fallback observation with the layout of stick belt on the collapsed wall indicated:in2010, the yearly maximum fallback of Wuli collapsed wall was66cm, total collapsing volume was3.96m’5, and the amount was4.95t, but Chengfeng collapsed wall didn’t collapse. In2011, the yearly maximum fallback of Wuli collapse mound was172cm, total collapsing volume was46.38mJ, and the amount was57.98t, Chengfeng was141cm,144.04m3and180.05t, especially during the process of291mm violent rainstorm on June10, the maximum fallback of Wuli collapsed wall was142cm, Chengfeng was141cm. The individual rainfall had a great influence on collapse mound erosion, and the collapsed wall occurred serious collapsing. The existence of collapsed wall headward erosion demonstrates the collapse mound is still in active development stage, and erosion till continues. Based on this, the collapsed wall is the most active component and provides material foundation for collapse mound erosion. Therefore, collapsed wall headward erosion is the main characterization of the collapse mound erosion.(3) The runoff and sediment contribution rate of the catchment and collapse mound zone during collapse mound erosion processes determined the significance to collapse mound erosion, and had a very important significance for collapse mound treatment. The results showed:among the runoff flowing pass the collapse mound exit, there was73%to75%of runoff amount from catchment plot, and among the sediment, more than99%was from collapse mound zone. The contribution rate of Wuli catchment to the runoff amount of collapse mound exit was73%, the collapse mound zone sediment contribution rate99.96%; the contribution rate of Chengfeng catchment to the runoff amount of collapse mound exit was75%, the collapse mound zone sediment contribution rate99.80%.(4) In November,2010and October,2011, we monitored collapse mounds in the test regions by GPS RTK method, which could more quantitativly show the dynamic change conditions of collapse mound erosion. Through ARCGIS to make spatial analysis, the erosion modulus calculation of Wuli and Chengfeng collapse mound computed from this was67.5thousand t/km-2·a and163.8thousand t/km2·a respectively. It could be seen erosion amount was quite amazing. From the two periods of monitoring data of Wuli and Chengfeng collapse mound, the spacial analysis showed that the collapse zone had the erosion and accumulation zone. Wherein, the erosion area was larger than the accumulation area, and the erosion volume bigger than accumulation. So the erosion amount was greater than the amount of accumulation, and the overall performance of collapse zone was the state of erosion.(5) The paper developed collapse mound monitoring data management system, which is C/S edition and has managing and counting function. Firstly, arrang the data obtained from collapse mound monitoring and analyse the relationships among them. After that, design the corresponding data sheet structure, and store the monitoring data in the database. Meantime, design the function module of the system. Using SQL Server database system, Visual Studio.NET development environment and C#language, develop collapse mound monitoring data management system. Hereby, the system would meet the requirements of the users to systematically manage the monitoring data.