RESEARCH ON ROCK MASS QUALITY CLASSIFICATION SYSTEM OF SEA REEFS AS BRIDGE FOUNDATION

Due to the restriction of landform,bridge foundation can only be placed on thin and weak sea reefs,the type and embedded depth of the bridge foundation are controlled by the quality of the sea reefs. Associated with the Laohu Mountain of the practice of Xihoumen bridge in Zhoushan mainland link project,in allusion to its geological conditions of large span and high tower bridge foundation,based on an overall consideration of different parts(that is above,below the water and the intertidal zone),propose using rock mechanical property,rock mass structure type,characteristics of discontinuities(especially controlled by weak discontinuities),weathering conditions and groundwater conditions(affected by tidal action)as controlling factors,and use uniaxial saturated compressive strength Rs,rock quality designation index RQD,rock mass integrality coefficient Kv,weathering degree coefficient KY and groundwater correction coefficient U to quantify the classification factors mentioned above,and build up a composite index Z=RsRQDKvKY+U to reflect the quality of sea reefs,and establish the classification system of different grades of rock mass．