Abstract—Generally, 2D plane strain numerical simulation is employed for analysis of a NATM1 tunnel construction in practice. Using forepole presuport technique, a soil region at the top of the tunnel has been improved and tunnel section can be advanced safe and with a lower risk condition; However, as forepole elements cannot be modeled by plane strain structural elements, a soil region with high strength parameters is considered on the top of the tunnel which is representative of the soil improved by forepole elements. To calibrate the parameters for the improved soil region on the top of the tunnel, a simple beam supported at the two ends is supposed and subjected to an increasing distributed load by Plaxis and then increase of load capacity and stiffness of the improved beam (beam with forpole elements) in respect to the soil beam are achieved. After calibration of the improved soil, two different analyses of tunnel construction have been performed. Consequently, it is concluded that forepole reduces the displacement; however, it has not sensible effects on reduction of mobilized forces in the initial lining of the tunnel. 
 

Index Terms—shallow tunnel, NATM, numerical modeling, forepole
 

Cite: Seyed Abolhasan Naeini and Bahareh Mohammadi-Haji, "Numerical Modeling of Soil Improvement for Construction of Tunnels Using Forepole Presupport," International Journal of Structural and Civil Engineering Research, Vol. 4, No. 4, pp. 366-370, November 2015. doi: 10.18178/ijscer.4.4.366-370