Study On Karst Collapse Mechanism In The Nishan Reservoir Area

Karst collapse is one of the main geoenvironmental problems of karst reservoir. Reservoir karst collapse can be defined as that collapse phenomenon related to karst taking place newly after water accumulation of reservoir, and generalized definition is that all geological phenomenon of karst collapse, new or old, related to hydraulic structure in both reservoir area and irrigated area. Most projects that have collapse accompany leakage. Reservoir collapse can result in serious leakage, even make reservoir dried up. Karst collapse near the dam foundation or building threaten directly building stability and safety, even result in building accident.Nishan reservoir that we study is a large-scale reservoir. Reservoir leakage is serious after reservoir is built up. Natural bedding in front of dam produce fissures that jeopardize dam safety because of karst collapse. All of these result in reservoir under control use for many years, that result in great water resource waste. Nishan reservoir concerns directly Qufu that is history and culture ancient city in the downstream; Yan - Shi, Jin -Pu railway; 11 shafts of Yanzhou Mine; farmland of more than 200000 mus of 6 countries, such as Nanxin, Fangshan, Xiqu, Xiaoxue, Lingcheng, Shizhuang, people of more than 200000 of two sides.Aimed at serious karst collapse state that reservoir exists, a large number of geologic examinations are done in region of interest. General geology is found out in field work, and boundary conditions that natural bedding in front of reservoir dam produce karst collapse are found out especially. Based on field geology work,failure mechanism of karst collapse is analysed, development trend is predicted, influence upon dam body stability of karst collapse is demonstrated, and then treatment measure is proposed, that offer some scientific references to solve main problems that reservoirexists.The paper is divided into four parts. In the first part, stratum lithologic character, geological structure, karst development feature and hydrogeologic feature of the area...