A study on the characteristics of deep overburden in Qizong segment of Jinsha River and its engineering effects

Overburden of 60-120m deep is developed in the Qizong segment of Jinsha River.The deep overburden can be divided into three layers upward.Pebble and gravel intercalated with minor fine sand or silty clay with the thickness of 11.1-33m at the bottom of the riverbed;a layer of fine sand,silty clay,pebble and gravel which with the thickness of 10.04-35m in the middle of the riverbed;coarse lenses of the drift(blocks),pebble(broken) and gravel layer with the thickness of 9.5-59m in the upper part.Sa...