Abstract:

The selection of cutterhead type is a key issue of EPB shield tunneling in sandy gravel stratum. The mechanism of ground disturbance induced by Lanzhou Metro Line No. 1 bored by EPB(earth pressure balance) shield with two types of cutterhead in sandy gravel stratum is systematically studied by field investigation, laboratory tests, 3D discrete element method (DEM) modeling and field monitoring. The major works of the study are as follows: 1) Firstly, triaxial tests (sample diameter of 30 cm) are carried out to obtain the stressstrain curve of sandy gravel stratum in lab. Then the parameters of DEM simulation are obtained by comparison between numerical experiments and laboratory tests. 2) 3D mechanical models of shields with plate cutterhead and spoke cutterhead are built by software Solidworks. 3) A 3D DEM model is established to simulate the ground disturbance induced by EPB shield tunneling. And the results of 3D DEM modeling and field monitoring reveal the effects of tunneling induced ground disturbance by EPB shield with two types of cutterhead in sandy gravel stratum. The range of the heavily disturbed zone of plate cutterhead shield tunneling is about 0.3D-0.5D (D refers to diameter of the cutterhead), while that of the disturbed zone of spoke cutterhead shield tunneling is less than 1/3 of that of the plate shield.

Key words: Lanzhou Metro, sandy gravel stratum, EPB shield, plate cutterhead, spoke cutterhead, ground disturbance, triaxial compressive tests, 3D DEM simulation, field monitoring