ABSTRACT
While a cross passage of shield tunnels was excavated near the Nakdong River in South Korea, the tunnels were suddenly destroyed by inappropriate grouting reinforcement due to high gas content unexpectedly existing in the alluvial soil deposit. To restore the collapsed tunnels, broad and deep excavation was performed along with diaphragm walls to replace the damaged tunnels with box structures. In addition, ground freezing was applied to connect the box structures inside the diaphragm walls to the intact tunnel sections. The excavation and two stages of ground freezing were conducted simultaneously, according to the construction plan. In this study, temperature changes in the ground and the horizontal displacements of the diaphragm wall were monitored and analyzed. Soil type, water content, and distance from the freezing pipes influenced the ground temperature distribution. The deformation of the diaphragm walls was induced by the combined effect of the deep excavation and frost expansion of the frozen soil.
