Modification of Peck Formula to Predict Ground Surface Settlement of Twin Tunnels in Low Permeability Soil

Table 1

Geotechnical properties of soil layers.

Soil type		e	(MPa)		(kPa)	(deg)	(cm/s)	(cm/s)
Miscellaneous fill	17.5	0.783	2.6	0.33	0	10.0	4 × 10^−3	5 × 10^−3
Plain fill	18.4	0.875	3.5	0.35	10	12.0	6.5 × 10^−4	8 × 10^−4
Mucky silty clay	17.6	1.245	2.5	0.45	11	9.5	4 × 10^−7	5 × 10^−7
Silty clay	19.4	0.721	6.0	0.41	35	16.0	2 × 10^−7	3 × 10^−7
Silty clay mixed gravel	19.8	0.601	10.0	0.38	45	17.0	6 × 10^−6	8 × 10^−6

Note. = unit weight, e = void ratio,  = modulus of compressibility,  = Poisson’s ratio,  = cohesion,  = internal friction angle,  = vertical permeability coefficient, and  = horizontal permeability coefficient.