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

Table 8

Results of direct shear test of fine sand.

Soil sample	Foam volume blending ratio (%)	Vertical pressure (kPa)	Micrometer reading (0.01 mm)	Shear strength (kPa)	Cohesion (kPa)	Internal friction angle (°)
Fine sand	0	50	17	28.76	3.5	26.8
		100	31.5	54.01
		200	60.5	104.53
		300	94	162
	30	50	15	26.13	4.7	23.9
		100	27.5	47.56
		200	52.5	90.42
		300	77.5	133.28
	40	50	13.5	23	2.9	21.9
		100	25	43.1
		200	48.5	83.3
		300	75	125.5