Monitoring Analysis Of The Stability Of Zipingpu Engineering Slope Under Influence Of Wen Chuan Earthquake

Sichuan Zipingpu water conservancy project, located in the upper stream of the Min Jing River, is a large scale water dam, being build for agricultural irrigation and civil water supply, it also have the functions like power generation, flood prevention, etc. Right bank is a thin and weak ridge, which is surrounded by river on three sides, is a structure of Shajinba syncline. All of the hydraulic structures are arranged in the right bank, a lot of high steep rock slopes are formed during excavating time. Because of the existence of weak structural planes, such as faults, interbeded shearing belts, the stability of slopes are quite obvious. The Wenchuan earthquake has broughtⅨdegrees earth intensity on Zipingpu hydraulic project, which is only 17km from the epicenter, the deformation characteristics and the stability of rock slopes under strong earthquake needed to be studied.In this paper, the author selected several slopes of Zipingpu conservancy project to analysis the influence of earthquake, those slopes contain discharging tunnel slope, water in-take and out-take slope, spillway slope, discharging tunnel slope in left-bank. In those slopes, we stalled multi-point extensometer, load cell, borehole inclinometer, etc. monitoring equipment, according to the monitoring results combine with the geostatistical site investigations, can analysis the deformation characteristics of slopes under different rock structure and support measure.Through the geostatistical site investigation, the stability of slopes with support measure are well, there are only several cracks on the surface of concrete spray layer, several point of collapse occur out the range of excavation and unsupport slopes. According to the monitoring results, the values of anchor supported slopes's deformation are quite small, from a few millimeter to tens millimeter; the slopes with bolt, nets spray joint and frame beam supporting has a deformation more than 20mm, discharging tunnel slope's maximum deformation come to 78mm through F3 fault, the deformation mainly occur in the major shock period, it instant stop after earthquake.According to the multi-point extensometer's monitoring results,antidip stratified rock slope and bedding rock slope has a main deformation region, this is interbeded shearing belts and other weak structural planes, it takes most of deformation and other place has a synchronization with those; medium-dip transverse rock slope's surface point has a maximum deformation, the values become smaller with the deep of hole become bigger, there aren't existence the main deformation region; as soft rock slope, because F3 fault's character are weak, it make the deformation quite big; accumulation slope's deformation mainly occur in overburden, the deformation started at the interface between rock and overburden, the value ordinarily decreases with height.Anchor load increased under earthquake, the change of anchor mainly occur during the main shock period, aftershock and after creep of slope make a few deformation. Borehole inclinometer monitoring show, medium-dip transverse rock slope take a creep deformation increased with height, the ground displacement is below 20mm, there has a shear deformation during weak structural planes; accumulation slope's displacement started at the interface of overburden, in overburden has a creep deformation, the displacement increase with height, borehole's deformate to out of slope, it directed to the lower strctches.