During the tunnel drive, a tilt of 4 mm to the north was observed. The metro tunnel construction was undertaken in March 1995 with limited compensation grouting. The first activity to cause the tilt of the Clock Tower was the westbound running London’s underground new jubilee line tunnel drive. Tilt of the Clock Tower and Remedial Measures The water pressure in the Thanet-Beds and chalk at the Clock Tower site is substantially reduced because of the continuous pumping from the nearby aquifer.Ģ.Pore-water pressures are close to hydrostatic equilibrium with the overlying aquifer throughout the London clay.The groundwater level in the nearby aquifer is about 9 m below ground level with a little tidal variation.The Thanet-Beds are about 8 m thick on the top of the chalk and located at 73 m below the ground level.The lowermost 5 m includes a thin layer of the pebble bed over sand.It is predominantly clayey soil comprising 8 m of upper mottled clay dissected by a thin layer of laminated beds over lower mottled clay about 5 m thick. Thanet-Beds (geological formation made of grey sand and mostly found in London) lies below the Lambeth-Group and resting above the chalk rock. The Lambeth-Group lies below the London clay. Further, the London clay is located till 35 m depth.The upper ground depth between 5 m and 8 m consists of an alluvium gravel.The following points describe the geology of the Clock Tower: Post Construction Behavior of the Clock Tower Settlement of the Clock Tower during Construction of Underground Metro Tunnel Likely so, most of the tourists are often seen debating the verticality of the Clock Tower. Thus, the inclination is about 1/250, an amount which is often quoted as being just discernible to the tourists. The clock face is 55 m above the ground level and is out of plumb towards the north-west by 220 mm. The weight of the Clock Tower is about 8400 tons imposing an average foundation bearing pressure of approximately 400 kPa. The Clock Tower was founded on a 3 m thick concrete raft, covering a total area of 15 m 2 within terrace gravels overlying London clay. The tower was constructed from load-bearing brickwork and stone cladding of 11 m 2 area installed up to a height of 61 m. The Big Ben, situated in London, is famous for its precision and accuracy and is known as the most accurate four-faced chiming clock in the world. Upon its construction in the year 1858, it was the tallest and the largest clock tower in the world. The Big Ben Clock Tower is the British cultural icon and was renamed "Elizabeth Tower" in 2012 to celebrate the diamond jubilee of Queen Elizabeth II.
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