Analysis of Face Stability during Excavation of Double-O-Tube Shield Tunnel

Table 1

Critical collapse pressures of given soil parameters.

	Soft clay (𝑐=5 kPa, 𝜑=15^∘)	Stiff clay (𝑐=12,𝜑=30^∘)
𝑁𝛾	0.442	0.155
𝑁𝑐	3.732	1.732
𝑁𝑠	0	0
𝜎𝑐	60.878 kPa	7.175 kPa