SPATIAL VARIATIONS OF GRAIN SIZE OF LOOSE SEDIMENTS IN DAOCHENG HAIZI MOUNTAIN

Haizi Mountain in the center of Daocheng's Quaternary ice cap is widely distributed with glacial moraine of different grain magnitudes. The site, covered with various loosed sediments underlying by granite as medium coarse grained biotite granodiorite,is to be used according to the planning and construction of China's Large High Altitude Air Shower Observatory(LHAASO). This paper describes and analyses five locations with granite gravels of moraine ridge and two locations with alluvial proluvial materials of terrace at the site. The statistical results of 106 huge gravels show that the moraine gravels of major percentages are 0.5~2.5 m in diameter,and have 2.5~7.5 m² in area and 5 m³ in volume to a certain extent. Two gravel samples of gravelly soil and fine debris soil of alluvial proluvium have the median particle size D₅₀=2 mm and 0.7mm,the non-uniform coefficient C_u=5.40 and 2.42,the curvature coefficient C_c=0.60 and 0.95, respectively. Both are poorly graded soil,i.e. homogeneous soil. These moraines and alluvial proluvial deposits with different genetic structures and magnitudes have different important values for site planning and utilization,and have certain influence on the stability of excavation pit wall. Afterwards,the results in this paper were adopted for planning and designing of LHAASO.