ABSTRACT
The Tamil Nadu Public Works Department (PWD) proposed to construct a new office building (G+3) over a demolished building site at the TNPWD Building site located at Chennai, India. There are several office buildings located along the boundary of the TNPWD building site, of which the PWD Main Building, behind which the proposed new building is to be constructed, is a 150-year-old heritage structure. Almost all the adjacent structures are of 2 or 3 storied of-fice buildings. Build in the 19th century, the PWD Main Building facing Marina beach has walls and footings constructed using brick and lime mortar. Considering the historical im-portance of the PWD main building, there is an apprehension that the pile boring and other construction activities on the proposed structure may damage the PWD main building due to the ground movement/vibrations. Detailed geotechnical and geophysical investigation were carried out at the site. The groundwater table was observed at about 3.5 m below the ground level. Vibration monitoring studies were carried out during the test pile boring operations. The piles adopted are bored cast-in-situ circular types of 450 mm diameter. The time history of acceleration during piling operations was continuously recorded. The maximum peak acceleration of the vibrations recorded was found to be about 0.01 g. It was also noticed that the maximum peak particle velocity (PPV) is 1.5 mm/s in the vertical direction and 0.65 mm/s in the horizontal direction at ground level of the PWD main building, which is acceptable. The maximum vibration levels were observed during piling operations in the SDR layer at the depth of 23 m from EGL.
