地震都震不倒比萨斜塔？

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.

比萨斜塔在几百年来一直困扰了许多工程师。由于塔底部分土壤是松软的，这座塔早在完工之前就出现了倾斜。然后，这座乌龙建筑却成为了世界奇观之一，还被列入了世界遗产名录。

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.

为什么在这个地震多发的地区，乌龙建筑比萨斜塔却还能够屹立几百年而不倒呢?这座位于意大利西北部的钟楼经历了两次世界大战，接待了无数游客，且自1280年以来，至少受到了4次大地震的打击，其中一次地震的震级达到了里氏6.0级。

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.

工程学教授Mylonakis等人认为，这种神奇的现象是“动态土壤结构相互作用”导致的。这就是说，比萨斜塔和高度和硬度与土壤的松软度结合在一起之后，很大程度上改变了斜塔的振动特性，即比萨斜塔不会与震动的地面产生共鸣。当地震发生的时候，塔身的振动幅度不如地面那么大。这简直就是在蔑视地球重力嘛!

"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教授说道，“那些土壤导致塔身倾斜，让它摇摇欲坠;但也正是因为这些土壤，比萨斜塔才得以在一次又一次的地震中幸存下来。”

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.

但这并不表示比萨斜塔有权嘲笑它周围的建筑物。比萨斜塔倾斜得越来越厉害，到了20世纪初，它真的快倒下来了。

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，意大利政府开始禁止游客进入塔内，并开始了长达十年的修复工程。人们将900吨重的铅平衡物放到了塔的北面(塔是向南倾斜的)。但与此同时，有人想出了更好的计划。

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.

这个计划就是在比萨斜塔北边建一座金字塔形建筑物，然后用吊索套到比萨斜塔中部，再连接到这座建筑物上。施工人员还挖走了塔底北面的部分土壤，这样塔身就会稍微向北倾斜。

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

工程师们还安装了设备，使他们能够调整塔下的水压，进一步控制倾斜。

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.

通过这种方式，比萨斜塔的倾斜角度最终从5.5度变成了3.9度。这个角度既能保证不会坍塌，也能让斜塔不辜负它的名字。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，这意味着塔楼不会脱离重力的影响。

"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.

“这座塔的基础是不太可能失败的，”修复项目的领导人之一John Burland对该杂志说。

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

如果还有什么能让比萨斜塔塌下来，那肯定是一场极其剧烈的地震了。