地震都震不倒比薩斜塔？

The Leaning Tower of Pisa and its 5.5 degree lean has vexed engineers for centuries.Partially constructed on unexpectedly soft soil, the ancient bell tower began to lean before it was even finished, a historical goof that went on to become one of the world's historical oddities - and made the tower a UNESCO World Heritage site.

比薩斜塔在幾百年來一直困擾了許多工程師。由于塔底部分土壤是松軟的，這座塔早在完工之前就出現(xiàn)了傾斜。然后，這座烏龍建筑卻成為了世界奇觀之一，還被列入了世界遺產(chǎn)名錄。

How can something so obviously structurally unsound endure in an earthquake-prone region for hundreds of years?People who assemble an IKEA cabinet and have 18 pieces left over don't expect to pass a wobbly Hemnes down to their great-grandchildren.The tower in northwestern Italy has managed to survive two world wars, millions of tourist visits and at least four strong earthquakes that have hit the region since 1280, according to Phys.org.One of those quakes was greater than 6.0 on the Richter scale.

為什么在這個地震多發(fā)的地區(qū)，烏龍建筑比薩斜塔卻還能夠屹立幾百年而不倒呢?這座位于意大利西北部的鐘樓經(jīng)歷了兩次世界大戰(zhàn)，接待了無數(shù)游客，且自1280年以來，至少受到了4次大地震的打擊，其中一次地震的震級達到了里氏6.0級。

Mylonakis, an engineering professor who studies geotechnics and soil-structure interaction, and more than a dozen researchers came up with an answer that involves that famous soft soil and a jargon-laden term called "dynamic soil-structure interaction."According to Phys.org, the engineers determined that the tower's height and stiffness, "combined with the softness of the foundation soil, causes the vibrational characteristics of the structure to be modified substantially, in such a way that the Tower does not resonate with earthquake ground motion."So during a quake, the tower doesn't shake as much as the earth beneath it, in further defiance of gravity.

工程學(xué)教授Mylonakis等人認為，這種神奇的現(xiàn)象是“動態(tài)土壤結(jié)構(gòu)相互作用”導(dǎo)致的。這就是說，比薩斜塔和高度和硬度與土壤的松軟度結(jié)合在一起之后，很大程度上改變了斜塔的振動特性，即比薩斜塔不會與震動的地面產(chǎn)生共鳴。當?shù)卣鸢l(fā)生的時候，塔身的振動幅度不如地面那么大。這簡直就是在蔑視地球重力嘛!

"Ironically, the very same soil that caused the leaning instability and brought the tower to the verge of collapse can be credited for helping it survive these seismic events," Mylonakis told the website.

Mylonakis教授說道，“那些土壤導(dǎo)致塔身傾斜，讓它搖搖欲墜;但也正是因為這些土壤，比薩斜塔才得以在一次又一次的地震中幸存下來。”

The tower's insulation from earthquakes does not mean it can metaphorically thumb its nose at nearby, earthquake-ravaged buildings.It has continued to settle throughout its history and by the early part of the 20th century, was in real danger of falling.

但這并不表示比薩斜塔有權(quán)嘲笑它周圍的建筑物。比薩斜塔傾斜得越來越厲害，到了20世紀初，它真的快倒下來了。

In 1990, the Italian government closed the tower to visitors and began a decade-long restoration project, according to Smithsonian Magazine. Restorers put 900 tons of lead counterweights on the north side of the tower while they came up with a better plan to slow its descent.

1990年，意大利政府開始禁止游客進入塔內(nèi)，并開始了長達十年的修復(fù)工程。人們將900噸重的鉛平衡物放到了塔的北面(塔是向南傾斜的)。但與此同時，有人想出了更好的計劃。

The plan involves erecting a stationary A-frame structure on the north side and extending cables from it to a sort of sling or harness around the midsection.

"This is to hold the structure in place while crews gradually begin to remove small amounts of soil from the high north side. Presumably, this will cause that side to subside or sink slightly, rotating the tower back toward the north by about one-half of 1 degree.

這個計劃就是在比薩斜塔北邊建一座金字塔形建筑物，然后用吊索套到比薩斜塔中部，再連接到這座建筑物上。施工人員還挖走了塔底北面的部分土壤，這樣塔身就會稍微向北傾斜。

Engineers also installed equipment that allows them to make adjustments to the water pressure beneath the tower, further controlling the tilt.

工程師們還安裝了設(shè)備，使他們能夠調(diào)整塔下的水壓，進一步控制傾斜。

All that construction fixed the tilt a bit - to 3.9 degrees from 5.5 degrees - while still helping the building maintain its namesake lean.

通過這種方式，比薩斜塔的傾斜角度最終從5.5度變成了3.9度。這個角度既能保證不會坍塌，也能讓斜塔不辜負它的名字。But more importantly, it meant the tower wasn't in danger of toppling from the effects of gravity alone.

但更重要的是，這意味著塔樓不會脫離重力的影響。

"It is extremely unlikely that the foundations of the tower will fail," John Burland, one of the leaders of the restoration project, told the magazine.

“這座塔的基礎(chǔ)是不太可能失敗的，”修復(fù)項目的領(lǐng)導(dǎo)人之一John Burland對該雜志說。

If anything causes the tower to collapse "it is much more likely that it would be due to a very large earthquake."

如果還有什么能讓比薩斜塔塌下來，那肯定是一場極其劇烈的地震了。