Studying the Characteristics of Vibrations Induced by Hard Rock TBM Construction in Urban Environments Based on a Field Test.

Vibrations induced by hard rock tunnel boring machine (TBM) construction have become an important concern affecting the environmental quality, particularly in urban environments. Herein, the vibration mechanism of TBM construction is studied by synchronously evaluating the three-dimensional vibration acceleration at different positions (such as the TBM cutterhead, rock stratum, and ground surface) based on the TBM construction subway tunnel project in Qingdao, China. At the TBM cutterhead, the acceleration value in the X direction considerably exceeds those in the Y and Z directions. The effective acceleration values in the X, Y, and Z directions are 0.007, 0.005, and 0.004 m/s2, respectively. Because of the presence of structural cracks in rock mass, the vibration influence of strongly weathered rock strata exceeds that of slightly weathered rock strata. On the ground, the acceleration values in the X and Y directions are amplified at 8.5 m away from the tunnel axis and the vibration signals of different frequencies will rebound at different distances from the tunnel axis. Although the vibration induced by TBM construction does not exceed the national specification requirements, the noise exceeds the set limit, thus necessitating noise control measures. [ABSTRACT FROM AUTHOR]