The shield tunnel construction of TIAA MRT Zhongli Extension Line is conducted along Zhongfeng Road starting from Laojie River Station (A22) to the surroundings of Zhongshan Road and then to the Zhongcheng Road crossover with a turn to the east. As the road width is not sufficient, the crossover must underpass the residential houses. The shield tunnel must meet the criteria of 20 meters underground. Therefore, maintaining the safety and stability of residential houses is the most important issue in the construction process.
According to the BOHSR high risk management procedures, the control and inspection management should be activated timely and inspection and evaluation during construction should be implemented during the underpassing construction work. In addition, risk management meetings should be held on a regular basis to review the countermeasures of related issues so as to ensure that construction operations will be carried out in accordance with the plan and the safety of residential houses will be maintained.
According to the construction plan, the shield-tunneling machine that will pass under the houses will adopt on-machine grouting or secondary grouting to greatly reduce surface subsidence in order to protect the structure of the foundation. Moreover, automatic monitoring equipment is set up at the area to provide instant signals for status assessment and disposal management so as to safeguard the safety of buildings above the tunnel.