A large scale landslide occured in rainy season of 1981, the volume of the landslide body is about 4.5*106 m3. The landslide body consists of the Permian limestone. This landslide is a typical landslide which slides along the bedding surface of the rock formation. The main reasons of the landslide are as follows:
The bad engineering geology condition. and the unreasonable mining order;
Cutting and excavating off the slope foot of the landslide;
The continual rainfall.
Un grand glissement de terrain, avec un volume de 4.5x106m3, est arrive à la season de pluis en 1981. Ce glissement est constitute de la formation calcaire de Permien,et est suive linterface de formation. Les facteur suivants sonts consideres les origines principales de ce glissement:
Conditions geologiques non favorables ã la statilite et programmes dèxploitation non optimises;
Oreusement de la partie inferieure du front de terrain;
Precipitation continue de longue duree.
In der Regenzeit im Jahr 1981 ereignete sich ein grosser Erdrutsch, dessen grösse et.4.5x106m3 war. Der Erdrutsch, Der aus Kalkstein von Perm bestand, war eine typische Gleitung an dem Gesteinlager entlang. Der Erdrutsch entstand aus folgenden Gruenden:
unguenstige ingenieur geologische Voraussetzung und Förderungsreihenfolge;
Böschungstuss war geschnitt ausgegraben;
dauernder Regen.
In the rainy season of 1981, the large scale landslide happened at Baguanhe Limestone Openpit Mine. The width of the landslide body is about 200m,vertical height about 250m,volume of the landslide body 4.5x106m3 (10.63Mt). The mining and transportation systems of the whole openpit mine were damaged and production of the openpit was stoped. Based on the in-situ geology and engineering geology investigation, the analysis of structure condition of rock mass, and determination of material content and physical-mechanical properties of clay rock on the sliding surface, the reason for development of the landslide is analysed.
The outcropping rocks in the mine area from the old to the new successively are Denyen Dolomite of Sinian System; sandstone, shale, clay rock, limeatone of Permian System, Emeishan basalt; Tertiary Xigeda layer and Quaternary sedimentary. Fig.1 shows the engineering geology shetch of this openpit mine. The geology structure conditions of the mine area are the complex. There are 12 faults, regional faults F¹ and F2 distribute in the north and south of the mine. Fault F¹ strikes NE25; dips NW with dipping angle 30–40°. Fault F2 strikes NE80°,dips SE with dipping angle 45–70°. Most of other faults strike SN or NE with the high dip angle. Diabase vein (β) invaded along faults and fissures with the fractured structure. This mine is a hillside open pit. The rock formation and slope of the open pit have the similar strike and dip, and the similar dipping angle. The striking of the slope and the rock formation are the NE direction, dipping SW with the dip angle of 35–40: The typical geology section is shown in Fig. 2. The results of the differential thermal analysis and X diffraction analysis show that clay rock mainly consists ot montmorillonite(Fig. 3 and Fig.4). The hydrogeologycal condition of the open pit mine is the more simple, underground water permeates through the bedding plane of the rock formation and the fissures in the rock masses. The hydraulic gradient of underground water is more high(about 17%). On the other hand, clay rock on the sliding bed has the lowest permeability, for this reason it can be regarded as the water-resisting. The drainage condition of surface water is the best due to the great slope angle.
