Research Of Mechanical Properties And Response To Project Of Xiaowan Hydropower Station Abutment Altered Rock Under The High-pressure Seepage

Weak zone is of great influence on the project stability. Depending on its size,it may be an overall project control or impact on local band stability, as a weak rock, when formed into a size distribution of alteration, Altered rock' influence on project stability is worth studying, especially in the high pressure flow condition. Firstly, the paper describes the geoengineering environment, distribution and properties of xiaowan Hydropower station abutment altered rock. Then, it mainly discusses the triaxial mechanical properties of the altered rock under high pressure seepage and the impact of pressure on the properties, and it models the impacts of excavation, dam construction on altered rock before water filled and seepage after water filled. Through Comparative analysing of variation betweeen before and after water filled, it assess the potential impact of seepage on the stability. Specific contents as following aspects:(1). The axial stress-strain curve is similar on the vary stage in both natural and seepage, it can be devided to for stages. But they have different characters in the same stage. Under high pressure seepage, compation stage is longer than that of natural, the strain increase from 2～3% to 4～5% at the conection point of comparation and linear stages and the slope of the curve linear stage decrease compared with natural condition. There is a turning point from linear to expansion stage.(2).Seepage lower shear strength, in which c decreased 12 percent to 44.2 percent, friction angle decreased 23.2 percent in deeply weathered rock and lower than 10.3 percent in other groups. Altered rock friction angle suffered lightly from seepage, it plays a weak role in the rock strength decreasing compared with effective confining pressure down by water pressure.(3).Altered rock has tow kinds of failure: tensile-shear and shear-tensil failure under high pressure seepage. seepge pressure act on the failure as:â‘ it help to form small fractures in rock surface,â‘¡it reduce friction on the failure surface.â‘¢it increase the angle of failure surface.(4).Simulate the effect of water pressure on the rock, the simulation result is that both the maximum and minimum principal stress change little on the left bank, on the wright bank, the displacement of E₄+E₅,E₁ change little, both the top and bottom displacement is not larger than 2mm, while the placement at the top of E₉ is relative large, it's about 1cm, like othe altered rock on the right bank, its bottom placement is about3～4mm. On the left bank, altered rock suffer little from seepage and displacement variation is less than that of the right bank.(5).Under Equivalent infiltration, the dam displacement is generally increased with the height increasing, the largest displacement is on the top, it'6.25cm. The displacement decrease from vault to the sides of the dam at the same hight. After waterfilled, displacement contour map is not vary mutations. Compared with rock strength reduction, force form water pressure on the upper side of the dam plays more impact on the displacement of the abutment altered rock. The dam influence little on both bank, the displacement it producd is less than 1.8cm.