Abstract

The leakage problems in dam abutment of Tuokou Hydropower Station are first revealed by geological analysis. The complexity of the special geological conditions of the dam abutment is mainly due to the widely distributed large fractures and karst caves. It's hard to conduct grouting work in such type of geological condition. A new grouting method, upstage with paste slurry packer and pulsating pressure, was presented. Moreover, a series of new grouting materials (pasty clay-cement slurry and stable slurry) were developed to resist the high-speed water rushing in karst aquifers. The leakage problem was finally solved, and the effectiveness of the solution further verified by both monitoring analysis.

1. Introduction

Tuokou hydropower station is located in Hongjiang (Hunan Province, China), and its hydraulic engineering grade is Type (1), Grade 1. The distance from Tuokou to Huaihua is 74 km. The normal storage water level of the reservoir is 250 m. The normal reservoir storage is 1.25×109 m3. The powerhouse with a width of 31.5 m, a length of 171.4 m, and a height of 58.8 m includes four units with an installed production capacity of 830 MW. Its main hydraulic structures include Dongyoushi main dam, Wangmaxi auxiliary dam and Hewan mountain [1]. The layout of the dam and its main hydraulic structures are shown in Figure 1. Hewan mountain has a peculiar geological conditions and serious geological defects. It is covered with deep cretaceous red strata whose thickness is 80m on average. The stratum has strong mechanical and chemical weathering. Mechanical weathering generally that precedes chemical weathering renders the rock mass more permeable and facilitates access for groundwater to large surface areas of rock substance [2]. Furthermore, a large proportion of adglutinates are eroded or there grows dense tiny fracture. Because of active groundwater, rock and soil masses, which are at the bottom of cretaceous red strata, around the boundary of soluble and non-soluble rocks and in the place groundwater changes, are incompact and have a large porosity. What's more, the most major problem is widely distributed corrosion phenomena. The karst caves and fractures also distribute widely so that there are large-scale leakage passages. The above mentioned phenomena will reduce the benefits of hydropower station and be a serious threat to the safety of the dam [3]. Therefore, to guarantee the normal operation of hydropower station, it is necessary to take urgent measures to minimize the leakage in Huwan mountain.

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