抄録
This paper reports the field monitored surface settlements due to the construction of 161 kV power-cable shield tunnels in Hsinchu. The soils encountered during tunneling were mostly cobble and gravelly soils. Four earth-pressure-balance shield machines with outside diameters 6.24 and 6.70 m were used for tunnel excavation. When driven through gravelly soils, significant cutter head wearing was observed. Base on field observation data, the following conclusions were made. The maximum surface settlement was reached at approximately 30 days after the passage of the face. The maximum surface settlement achieved was only 5 to 6 mm. The field monitored settlement-time data were in fairly good agreement with the curves estimated with the hyperbolic model. The maximum surface settlements induced in cobble and gravelly soils were significantly less than those induced in clayey and sandy soils. This is most probably due to the high stiffness and shear strength of the gravelly soil, which reduced the ground deformation due to subsurface excavation. The induced settlement trough was wider than those induced in stiff clay, soft to hard clay, and sand above ground water table.
