ABSTRACT
This paper presents a case study of the ground improvement works on TBM tunneling for Taipei MRT in the east district of Taipei City. The TBM tunnel is mainly drilled in the composite strata which consist of alluvial deposits, colluvium deposits, and rock formation. The upper half of the improvement zone is a soft soil layer and the lower half of the improvement is a hard rock layer (Sandstone or Shale). The soft soil layers outside of the tunnel-shaft interface require jet grouted body to increase their strength and decrease their permeability. Also, in order to tunnel through the composite stratum, it needs to carry out jet grouting in the soft ground to increase the strength of the soil layer to homogenize the excavation section. Since the hard rock cannot be used by jet grouting, permeability grouting is used to decrease its permeability. In this case, the jet grouting and the permeability grouting were used to overcome the strata with different geological conditions to meet the strength (self-supporting) and to reduce the permeability of the ground. The ground improvement results show that for the jet grout zone, the total core recovery is greater than 90%, the in-situ permeability tests and the laboratory uniaxial compression strength meets the specification requirements. For the TAM grouting zone, the permeability coefficient k carried out by in-situ permeability tests was less than 1×10-5 cm/sec. Before breaking the cutter face on the diaphragm wall for the TBM to enter from the shaft, the horizontal leakage tests of the up track and down track at the west side station have been completed. Without supplementary grouting, the permeability coefficient k of all horizontal permeability tests is less than 1×10-5 cm/sec.
