Equivalent Research On Engineering Characteristics Of Cataclastic Rockmass And Its Engineering Application

The cataclastic rock mass is composed of several small rock blocks, and it doesn't contain or only contain little mud. Because the connectivity between rock blocks is bad, once the rock blocks are uncovered or exposed, they will rebound and relax with the release of confining stress, on such a case, only the mechanical parameters under relaxing conditions can be obtained, while the mechanical parameters can represent the in situ properties are difficult to obtain. Even though the laboratory test is conducted, it also difficult to obtain the undisturbed samples that can represent the actual characteristics. Therefore, conducting the mechanical test and obtaining the mechanical parameters that can represent the in situ situation of cataclastic rock mass have became a new direction worth exploring and making a breakthrough on in current research on the engineering characteristics of rock mass.By taking part in many research projects on the engineering geological problems of dam foundation and foundation planes selection for a number of large or super-large hydropower stations, the author has conducted various researches on the engineering characteristics of rock mass with cataclastic texture. This paper analyzes the genetic type, formation and occurring environmental conditions (mainly indicate the stress environment) in late stage of the cataclastic texture, and demonstrates the theoretical foundation of equivalent experimental study by researching and analyzing the instance of Gongboxia power station. Besides, by developing a new technique for obtaining the undisturbed samples of cataclastic rock mass and measuring the density can represent the one under in situ conditions in the laboratory, and based on the basic principle that the deformations of rock mass or soil under pressure mainly are the compressive deformations of interspaces of rock mass or pores of soil, a new pressure test apparatus is manufactured by using the measured density above as the reference value and the obtained bulk samples of cataclastic rock mass above, moreover, the equivalent test research on the mechanical parameters of rock masses with cataclastic texture has been successfully achieved using MTS rock tester. The test preliminarily reveals the relations between stress condition, physical properties and deformation modulus of rock masses with cataclastic texture and obtains or predicts the deformation modulus of rock masses with cataclastic texture under in situ conditions, and the results are basically in accordance with that under actual circumstances by field inspection.The research results of this paper are as follows:(1) Analyzing the type and genesis of cataclastic rock mass, concluding and summarizing previous research results, and specifically analyzing the phenomenon that there are many fracture zones composed of cataclasitc rock masses in the basalts with complete texture at Xiluodu power station, while there are few in breccia lavas.(2) Studying the occurring conditions of cataclastic rocks and taking the Western Sichuan Province and Northwestern Yunnan Plateau as the research areas, besides, carrying out an exploratory research on the stress conditions for cataclastic rock formation using finite element calculation, meanwhile, demonstrating that the maximum principal stress value of tectonic movement can range from 50 to 100MPa or above.(3) Concluding and summarizing the development characteristics and statistical method of structural planes of rock masses with different cataclastic textures, besides, taking the Jinanqiao, Xiangjiaba and Xiluodu power stations as instances and introducing several lumpiness analysis methods for different cataclastic rock masses in detail.(4) Taking the Jinanqiao, Xiangjiaba and Xiluodu power stations as the main research sites and obtaining the undisturbed samples without relaxing by using the newly developed double-layer in situ sampling technique, moreover, conducting test and research on these samples and obtaining the physical and mechanical parameters under natural conditions.(5) Studying a number of previous foreign research results on the self-weight consolidation of sediments and establishing the curve of stress against dry density, moreover it is found that when the pressure on sediments is about 50-60MPa, the dry density of sediments will ranges from 2.3 to 2.4g/cm~3, which is generally in accordance with the density of cataclastic rock masses obtained by field sampling.(6) Analyzing the physical properties and stress environment of ancient completely weathered granitites and conglomeratic sandstones at Gongboxia power station, and it is concluded that the ancient completely weathered granitites undergo the same geological environment with the conglomeratic sandstones of Linxia Formation, together with the concordance on size and component between them, although they are different in their rock name, they have the same physical properties. Through the analysis on the physical consolidation diagenesis under natural conditions, a natural instance is provided for the equivalent research on the engineering characteristics of rock mass.(7) Demonstrating the basic foundation or theoretical basis of the equivalent research on the engineering characteristics of cataclastic rock mass, moreover, by analyzing the results of equivalent pressure test on six test samples, it is demonstrated that the results of laboratory consolidation test are equivalent to the consolidation in geological history and the research results of strata consolidation in foreign countries. Meanwhile, the modulus of compression under pressures of the same magnitude shows a property of equivalence, which provides a new research approach for analyzing the deformation modulus of cataclastic rock mass using the laboratory consolidation test.