比薩斜塔爲何能經歷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.

意大利的標誌性建築比薩斜塔有5度的傾斜度，而且還歷經4次大地震，卻依然屹立不倒，完好無損，最新的研究揭開了這個謎底。

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.

比薩斜塔高58米，被評爲聯合國教科文組織世界遺產。一千年來，比薩斜塔的脆弱性一直令工程師和科學家們困惑不已。按說，中度地震活動應該就能導致它嚴重受損甚至倒塌，但現實中這樣的情形並未發生，令人不可思議。

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.

英國布裏斯托爾大學一個由16名工程師組成的研究小組如今發現，比薩斜塔如此的高度及其堅硬的建築材料與鬆軟的地基土壤結合在一起，使它不會與地震發生時的地表活動產生共振。

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.

這種現象被稱爲“土壤-建築結構”動態相互作用（DSSI），幸運的是，比薩斜塔現在是DSSI效應的世界紀錄保持者。

“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.

布裏斯托爾大學地震與岩土工程研究小組負責人米洛納基教授說：“有意思的是，導致斜塔傾斜不穩、幾乎要倒的土壤也是幫助它挺過這些地震活動的功臣。”

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.

比薩斜塔一直吸引着大量遊客前來，人們驚歎其卓越的建築成就。比薩斜塔始建於1173年，由於多次戰爭來襲，建築時間持續了大約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.

多年以來，人們爲維護這一歷史建築做出多次努力。在上世紀20年代，人們在其地基中注入了水泥灌漿，以穩定塔身。在1990年，由於擔心會倒塌，相關部門還決定將比薩斜塔完全對遊客關閉。

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.

這是比薩斜塔近800年來首次對遊客關閉。比薩斜塔在2001年重新開放，仍是意大利最著名的旅遊景點之一。