Upper-Bound Finite Element Adaptive Analysis of Plane Strain Heading in Soil with a Soft Upper Layer and Hard Lower Layer

Table 1

Critical surcharge loading σ_s for soft 1.

Position of soil interface	σs (kPa)
	C/D = 1	C/D = 2	C/D = 3	C/D = 4
Case 1	135.49	151.11	120.18	66.21
Case 2	135.15	152.11	124.15	69.59
Case 3	225.42	283.92	300.18	283.15
Case 4	353.79	482.96	561.85	607.08
Case 5	528.54	781.29	951.22	1068.87
Case 6	962.68	1508.01	1842.28	2206.58
Case 7	14504.95	91493.11	212042.83	503089.38