Basalts with chloritized joints were distributed in dam foundation and two banks of low altitude in Jin'anqiao hydroelectric power station, and these special basalts were named basalts with joints chloritization. In studying area, basalts were cutting severely by dense chloritized joints. In the light of existing Code for Water Resources and Hydropower Engineering Geological Investigation(GB50287–99,China), types of rock mass structure should be inlaid cataclastic structure or cataclastic structure, and types of rock mass quality should be grade IV or grade III2, but in situ condition, basalts closely locked. Through field investigation and analysis, found out these were new special structure rock masses named inlaid cataclastic structure in situ. These cataclastic structure rock masses were discreted in situ, and differentiated with fracture zone by tectonic process or displacement. The inlaid cataclastic structure rock mass in situ had some characteristics: with quasi–integrality; low permeability, high rock mass wave velocity, high deformation modulus. Based on these characteristics, put forward the rock mass structure classification scheme of these new inlaid cataclastic rock mass in situ..
Jin'anqiao hydropower station located in the middle of the Jinsha River in Yunnan Province. The height of this concrete gravity dam was 160m, capacity of 742,000,000 m3, the total installed capacity of 2500MW (Cui 2005). The main stratums of dam area were the Permian basalts. Among the basalts distributed in the dam foundation and two low- altitude banks, joints and a lot of subtle cracks were concentrated with chlorite minerals. Basalts with joints in generally contained chlorite minerals were called basalts with joints chloritization. According to the existing Code for Water Resources and Hydropower Engineering Geological Investigation (GB50287- 99, China), types of the rock mass with a low discontinuities space structure should be inlaid cataclastic structure or cataclastic structure, and types of rock mass quality should be grade IV or grade III2, but in situ condition, basalts closely locked. Could these special rock masses been used as foundation of high concrete gravity dam? The study of basalts with chloritized joints had theoretical and engineering significance.
From the existing Code of Water Resources and Hydropower Engineering Geological Investigation(GB50287–99,China) (Table 1, Table 2), the main evaluation index of rock mass integrity was discontinuity spacing to evaluate the structure types of the rock masses. The existing code(GB50287–99) also provided the table of using integrity coefficient to evaluate the rock mass integrity. In the code (GB50287- 99) discontinuity spacing and integrity coefficient had a good correlation in evaluating the rock mass integrity.
(Table in full paper)
For many years, China havd built Longyangxia Hydropower Station, the Ertan Hydropower Station, the Three Gorges water conservancy project, Xiluodu Hydropower Station, and soon, and the classification research of rock structures had made great progress. Main evaluation indexes were discontinuity spacing, RQD, volumetric joint count(Jv), integrity coefficient(K v) and so on, and these indexes had good correlation. A lot of tests proved that division scheme of rock structures in code(GB50287–99) was reasonable and safe.
