Study On Reef Rock Mass Quality Classification System

Based on Zhoushan mainland link project, The Ministry of Transport started a national technology project titled "Study on Structure Characteristics and Technical Standards of Long Span Suspension and Steel Box Girder Sea-Crossing Bridge", this thesis takes the opportunity of the sub research project of "Study on the Guide of Rock mass Quality Classification System of Sea Reefs as Bridge Foundation", depends on the engineering practice of Xihoumen Bridge, takes the north tower foundation of Laohu island as research object, guided by the development tendency and comparative analysis of classification methods, based on the engineering geological characteristics of reef rock mass and according to the select principle of classification control factors, to carry out the research of reef rock mass classification system.In the thesis, the development tendency of classification methods is summarized firstly, followed by a sortation and comparative analysis among different kinds of classification methods both in and abroad, and chooses the classification method of multi-factors and multi-indexes with a complex index for reef rock mass classidfication. Subsequently, from the engineering geological characteristics of the Laohu island, the engineering geological characteristics of the reef rock mass are concluded systematically. Abide by the select principle of classification control factors, use5classification control factors of rock mechanical property, rock mass structure type, characteristics of discontinuities, weathering conditions and groundwater conditions as the basic elements of reef rock mass quality classification system, and use uniaxial saturated compressive strength Rb, rock quality designation index RQD (or rock block index RBI), rock mass integrality coefficient Kv, weathering degree coefficient Ky to quantify and compartmentalize the classification factors mentioned above. Then, according to factor multiplication method the functional relation between these indexes of Z(Rb,RQD,Kv,Ky) or Z(Rb,RBI,Kv,Ky) is built up, and a modifier T which depends on groundwater conditions is used to modify the basic scoring value Z, and finally take the modified scoring value [Z] as the complex index which indicates the quality level of the rock mass. After that, the dependability of reef rock mass classification system is validated by several rock mass classification methods commonly used both in and abroad.Based on the reef rock mass classification system, the study on rock mass quality classification and engineering geological rating of discontinuities of the Laohu island are carried out, combined with the value-taking of mechanical parameters of the rock mass, the comprehensive rock mass (including discontinuities) classification of the Laohu island and corresponding value-taking system of deformation and strength parameters are built up. Finally, the guideline and principles for the establishment of the classification guide are presented, and the main contents and Structure are determined too, which lay the foundation for the establishment of Guide on Rock mass Quality Classification System of Sea Reefs.