Practice of gravel foundation construction;

This paper presents a method of tamping for improving unconsolidated sand and gravel foundation backfilled on the flood land,and introduces the principles of soil improvement with some engineering cases.

For the construction of the running tunnels of Chengdu Metro in sandy cobble ground,the shield machine is required to have the capability of performing long-distance boring in sandy cobble ground,crushing the large boulders and cobbles and prevention and control of mud bursting.

The first stage project of line 1 of Chengdu Metro mostly passes through water-rich sandy cobble ground,which contains a small amount of large boulders.