Q2. (a) An Earth Pressure Balance (EPB) tunnel project for Mass Rapid Transit in Singapore has been reported to have the surface settlement as depicted in FIGURE Q2. Given that the tunnel diameter, D is 6.6 m, the depth of the tunnel, z0 is 28 m from the ground surface, and bedrock was laid at 25 m from the invert of the tunnel. As an engineer, you would like to measure how much ground was affected due to the surface settlement.

i. Obtain the volume loss that had occurred in this tunnel construction at the maximum settlement trough.

ii. Obtain the longitudinal settlement that might occur by using the rule of thumb.

iii. If the EPB wants to be replaced by other tunneling methods, discuss with your own point of view, what are the choices that the consultant has and why?

(b) There are various methods by which both surface and subsurface structures can be protected from the effects of ground movements generated by tunneling and deep excavations. Describe the proposed protective measures that can be considered in a tunneling project.

CenteLine y, Distance from the tunnel center line 10 Point of Max Curvature, y = 1.73i 20 Clayey soil y = 19. kN/m3 Su = 20 kPa y = i Settlement Trough (mm) Zo Point of Inflection = Point of Maximum Horizontal Movement 30 40 50 Tensile Strain (Hogging Zone) Compressive Strain (Sagging Zone) Tensile Strain (Hogging Zone) FIGURE Q2: Tunneling induced ground surface settlement trough EQUATIONS i = KZ Vs = V21 i Smax MD2 V =V- 4 SLmax 0.5Smax Smax 0.31V,D2 KZO CenteLine y, Distance from the tunnel center line 10 Point of Max Curvature, y = 1.73i 20 Clayey soil y = 19. kN/m3 Su = 20 kPa y = i Settlement Trough (mm) Zo Point of Inflection = Point of Maximum Horizontal Movement 30 40 50 Tensile Strain (Hogging Zone) Compressive Strain (Sagging Zone) Tensile Strain (Hogging Zone) FIGURE Q2: Tunneling induced ground surface settlement trough EQUATIONS i = KZ Vs = V21 i Smax MD2 V =V- 4 SLmax 0.5Smax Smax 0.31V,D2 KZO