5.4　Detailed Investigation

5.4.1　The detailed investigation shall basically identify the selected site's engineering gedogical and hydrogedogical conditions.

5.4.2　The detailed investigation report shall include the following contents:

1　1∶2000 integrated engineering gedogical map of the site；

2　Stability analysis of side and front slopes at the entrance of the access tunnel；

3　Lithology（strata），structures，and stratum occurrences in the site as well as the locations，occurrences，scales and combination relations of the main faults，fracture zones，and joint/fissure-intensive zones therein.

4　Hydrological parameters such as ground water table elevation，permeability coefficient，and water chemical composition，ground water monitoring results，predicted possibility of sudden water inflow during tunneling，and estimated maximum water inflow rate；

5　Describe distributions and combinations of main weak structural planes，evaluate the rock mass stability of cavern tops，side walls，and cavern intersections according to rock mass stress data，and put forward a disposal suggestion；

6　Rock mass structures，joint properties，rock mass features，and rock/soil physical and mechanical indexes of shafts；

7　Give a rock mass quality classification and create a gedogical model；

8　Determine the scope of the rock mass used for building the storage according to the rock mass quality classification results and put forward recommendations on cavern axis direction，span，spacing，and tunnel entrance location；

9　Determine the elevation of the stable ground water table and propose a cavern tank depth；

10　Identify the storage site's rock mass quality segmentation，classification，and scope，and give a cavern stability evaluation；

11　Unsolved problems and suggestions.