EVALUATION OF ENGINEERING GEOLOGICAL CONDITION OF DAYA BAY FOR SITTING THE LABORATORY OF NEUTRINO UNDERGROUND EXPERIMENT

Neutrino Underground Laboratory is a special underground rock engineering project.Its site selection and operation put very rigorous on engineering geological conditions and engineering environment.A key question of the experiment is to find out the neutrino mixing angle(13) for particle physics,nuclear physics,celestial bodies physics and cosmography in the world.Nowadays,Reactor Neutrino Measurement of 13 is a question under discussion worldwide.The site is adjacent to Daya bay reactor with high powers of Daya Bay Nuclear Power plant.The laboratories are planed at the south foot of the Paiya Mountain with highly altitude and the enough overburden for decreasing the background.This environment is benefit to the precision of Neutrino Measurement of 13.This paper presents the analysis and assessment of engineering geological conditions.The works are based on data got from topographic survey,geologic investigation,geophysical exploration,drilling,borehole tests including geostress measurement,and lab tests etc.As a result,it is known that the rocks and tectonic conditions are simple,massive granite is with high strength,relative low geostress,groundwater is mainly limited in fissures with a low permeability coefficient.The four experiment caverns are located in rocks of Ⅰ~Ⅱ class,and the connection tunnel is sit in rocks with 81% of Ⅲ or above Ⅲ classes.After evaluation of engineering geological conditions,it is indicated that the Daya Bay neutrino underground lab will become a optimum location for measure 13 in the world because of the low investment and the high measurement precision.