Tilt­ing tower

The Star Malaysia - Star2 - - LIVING -

BE­NEATH it, gov­ern­ments have veered from Left to Right, but the tower of Big Ben has al­ways seemed res­o­lutely straight – un­til now.

Sur­vey­ors have found that it has de­vel­oped a tilt, which is get­ting worse ev­ery year.

The top of the clock tower at the Palace of West­min­ster in Lon­don is now 43cm off the per­pen­dic­u­lar – so far off that ex­perts say it is vis­i­ble to the naked eye.

If the tower’s move­ment were to con­tinue un­cor­rected, it would one day top­ple over.

But West­min­ster’s politi­cians can breathe easy. At the cur­rent rate it would take some 4,000 years for the tower to reach the an­gle of the Lean­ing Tower of Pisa, and even longer to hit tip­ping point.

Civil en­gi­neers be­lieve that the clock tower – known as Big Ben af­ter the main bell within it – is grad­u­ally “sink­ing” into the land. But the pat­tern is un­even, with sink­ing oc­cur­ring more quickly on the north side than the south.

The prob­lem has been blamed on decades of build­ing work around the foot of the ed­i­fice – 96m, 11 storeys, 393 stairs – since it was com­pleted in 1858.

These have ranged from a sewer built in the 1860s, to the District Line the fol­low­ing decade, and an un­der­ground car park for MPs in the 1970s.

When the Ju­bilee Line was ex­tended through West­min­ster in the late 1990s, spe­cial tech­niques were used to cre­ate a con­crete bar­rier un­der the tower, in an at­tempt to big ben is be­com­ing the lean­ing tower of Lon­don. se­cure it.

Yet a new sur­vey for Lon­don Un­der­ground and the Par­lia­men­tary Es­tates Depart­ment has found that the rate of move­ment – which had been steady for many years – has now ac­cel­er­ated.

The re­search finds that be­tween Novem­ber 2002 and Au­gust 2003, a mys­tery “event” caused the tower to lurch, with the clock face mov­ing up to 3mm away from the ver­ti­cal.

The en­gi­neers con­clude that no sin­gle known fac­tor can fully ex­plain the “event”. Since 2003, the tilt has con­tin­ued to in­crease by 0.9mm a year, around 40% faster than prior to that year.

The tower is now lean­ing to­wards the north-west at an an­gle of 0.26 de­grees, mean­ing the top of the tower is 43cm from ver­ti­cal. The re­port says this is within safe lim­its. The Lean­ing Tower of Pisa, by con­trast, leans by around four de­grees.

Nev­er­the­less, Lon­don’s lean­ing clock tower is al­ready caus­ing cracks in the walls of other parts of the House of Com­mons.

John Bur­land, emer­i­tus pro­fes­sor and se­nior re­search in­ves­ti­ga­tor at Im­pe­rial Col­lege Lon­don, who has worked on both the Big Ben tower and the one in Pisa, says: “The tilt is now just about vis­i­ble. You can see it if you stand on Par­lia­ment Square and look east, to­wards the river. I’ve heard tourists there tak­ing pho­tos say­ing, ‘I don’t think it is quite ver­ti­cal’ – and they are right.

“If it started greater ac­cel­er­a­tion, we would have to look at do­ing some­thing, but I don’t think we need to do any­thing for a few years yet.” – © The Daily Tele­graph UK 2011

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