Ground Settlement of High-Permeability Sand Layer Induced by Shield Tunneling: A Case Study under the Guidance of DBN

Table 7

Parameters of sandy soil layers.

Soil layer number	Soil layer name	Effective particle size (mm)	Intermediate particle size (mm)	The average particle size (mm)	Boundary particle size (mm)	Coefficient of unevenness ()	Curvature coefficient ()	Natural dip (°)
								Overwater	Underwater
2-3	Fine sand	0.052	0.105	0.221	0.232	4.46	0.91	29.63	26
2-4	Coarse sand	0.173	0.418	0.712	1.113	6.43	0.90	29.94	28.33
7-2	Coarse sand	0.292	0.801	2.584	4.656	16.162	0.53	—	—