比萨斜塔为何能经历4次大地震而不倒？

New research has revealed how the iconic Leaning Tower of Pisa has managed to stay standing – and intact – in the face of four strong earthquakes and a precarious lean of five degrees.

意大利的标志性建筑比萨斜塔有5度的倾斜度，而且还历经4次大地震，却依然屹立不倒，完好无损，最新的研究揭开了这个谜底。

The vulnerability of the Unesco World Heritage Site has mystified engineers and scientists for millennia. Moderate seismic activity was expected to significantly damage the 58m tall Tower, or even result in collapse but, incredibly, this has not happened.

比萨斜塔高58米，被评为联合国教科文组织世界遗产。一千年来，比萨斜塔的脆弱性一直令工程师和科学家们困惑不已。按说，中度地震活动应该就能导致它严重受损甚至倒塌，但现实中这样的情形并未发生，令人不可思议。

A research group of 16 engineers at the University of Bristol has now discovered that the considerable height and stiffness of the Tower, combined with the softness of the foundation soil, ensure it doesn’t resonate with earthquake ground motion.

英国布里斯托尔大学一个由16名工程师组成的研究小组如今发现，比萨斜塔如此的高度及其坚硬的建筑材料与松软的地基土壤结合在一起，使它不会与地震发生时的地表活动产生共振。

This phenomenon is known as dynamic soil-structure interaction (DSSI) and the Tower now holds the auspicious title of world record holder in DSSI effects.

这种现象被称为“土壤-建筑结构”动态相互作用（DSSI），幸运的是，比萨斜塔现在是DSSI效应的世界纪录保持者。

“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,” said Professor Mylonakis, head of the Earthquake and Geotechnical Engineering Research Group at the University of Bristol.

布里斯托尔大学地震与岩土工程研究小组负责人米洛纳基教授说：“有意思的是，导致斜塔倾斜不稳、几乎要倒的土壤也是帮助它挺过这些地震活动的功臣。”

The Tower continues to attract visitors keen to marvel at this remarkable architectural feat. Construction on the Tower began in 1173 and continued for about 200 years due to the onset of a series of wars.

比萨斜塔一直吸引着大量游客前来，人们惊叹其卓越的建筑成就。比萨斜塔始建于1173年，由于多次战争来袭，建筑时间持续了大约200年。

Multiple efforts to maintain the historic structure have occurred over the years. In the 1920s, the foundations were injected with cement grouting with the intention of stabilising the Tower, while in 1990, a decision was made to completely close the site to visitors due to fears it was at risk of toppling.

多年以来，人们为维护这一历史建筑做出多次努力。在上世纪20年代，人们在其地基中注入了水泥灌浆，以稳定塔身。在1990年，由于担心会倒塌，相关部门还决定将比萨斜塔完全对游客关闭。

It was the first time the Tower had been closed in 800 years. It reopened again in 2001 and remains one of Italy’s most popular tourist attractions.

这是比萨斜塔近800年来首次对游客关闭。比萨斜塔在2001年重新开放，仍是意大利最著名的旅游景点之一。