Why doesn’t the Leaning Tower of Pisa fall over? - Alex Gendler

譯者: Pei-Chen Benson Liu 審譯者: Harper Chang

In 1990, the Italian government enlisted top engineers

在1990年，義大利政府 徵募頂尖工程師

to stabilize Pisa’s famous Leaning Tower.

加固著名的比薩鐵塔

There’d been many attempts to right the tower during its 800 year history,

在比薩鐵塔的 800 年歷史中 人們很多次想要這樣做

but this team’s computer models revealed the urgency of their situation.

但透過團隊的電腦模型 大家才知道刻不容緩

They projected the tower would topple if it reached an angle of 5.44 degrees—

他們推斷一旦傾斜超過 5.44 度 這座高塔便會倒塌

and it was currently leaning at 5.5.

而目前已經傾斜 5.5 度了

No one knew how the tower was still standing, but the crisis was clear:

沒人瞭解為何斜塔依然矗立 但問題已經不可忽略

they had to solve a problem that stumped centuries of engineers,

必須解決這個 糾纏古今無數工程師的問題

and they needed to do it fast.

而且刻不容緩

To understand their situation,

想弄清情況

it’s helpful to understand why the tower tilted in the first place.

需要瞭解這座高塔 一開始傾斜的原因

In the 12th century, the wealthy maritime republic of Pisa

12 世紀時，比薩共和國 是個靠海的富裕國度

set about turning its cathedral square into a magnificent landmark.

當時他們正要把教堂廣場 改造成壯觀的地標

Workers embellished and enlarged the existing church,

工人們為擴建、美化教堂

and added a massive domed baptistry to the plaza.

還建造了一座寬闊的穹頂洗禮池

In 1173, construction began on a free-standing campanile, or bell tower.

1173 年，一座獨立式鐘樓開工

The engineers and architects of the time were masters of their craft.

那時參與的工程師和建築師 都是其領域的菁英

But for all their engineering knowledge,

但他們的工程知識

they knew far less about the ground they stood on.

不足以認識當時的地質

Pisa’s name comes from a Greek word for “marshy land,"

比薩這個名字 源自希臘語裡的「沼澤地」

which perfectly describes the clay, mud, and wet sand below the city’s surface.

貼切描述了這片由黏土、泥巴 和潮濕的沙子組成的土地

Ancient Romans counteracted similar conditions with massive stone pillars

古羅馬人曾用大型石柱 應付類似狀況

called piles which rest on Earth’s stable bedrock.

這整批石柱稱為石堆 矗立在地球穩固的岩床上

However, the tower’s architects believed a three-meter foundation would suffice

然而，斜塔的建築師認為三尺的地基 對這樣不怎麼高的建築來說

for their relatively short structure.

已經足夠了

Unfortunately for them, less than five years later,

還不到五年，不幸的事發生了

the tower’s southern side was already underground.

這座高塔的南邊一角已經陷入地底

Such a shifting foundation would normally have been a fatal flaw.

一般來說，如此不穩固的地基 總會帶來致命一擊

If workers added more weight,

若是往塔上增加更多重量

the pressure from upper stories would sink the structure

建築上層的重力 會使整座建築向下沉

and fatally increase the lean.

傾斜情況便無法挽救

But construction halted at the fourth story for nearly a century

但是建築到四樓時中斷了近百年

as Pisa descended into prolonged warfare.

當時比薩進入長時間的戰爭時期

This long pause allowed the soil to settle,

長時間停工使土壤有機會更加堅固

and when construction began again in 1272,

當建設工程 1272 年重啟時

the foundation was on slightly more stable footing.

高塔地基下的土壤變得稍微穩固了些

Under the direction of architect Giovanni di Simone,

在建築師喬瓦尼·迪·西蒙尼的帶領下

workers compensated for the tower’s minor tilt

為了調整回高塔傾斜前的樣子

by making the next few floors taller on the southern side.

接下來建造的幾樓 南邊都會高出一點

But the weight of the extra masonry made that side sink even deeper.

但額外的石造結構 卻讓南邊陷得更深

By the time they completed the seventh floor and bell chamber,

七樓和鐘堂的建設工作完成時

the angle of the tilt was 1.6 degrees.

高塔傾斜 1.6 度

For centuries, engineers tried numerous strategies to address the lean.

數幾世紀來，工程師 試過無數種解決方案

In 1838, they dug a walkway around the base to examine the sunken foundation.

1838 年，他們在高塔基底周圍 挖掘了走道以方便觀察下沉情況

But removing the supporting sand only worsened the tilt.

但移除沙子後，傾斜卻更嚴重

In 1935, the Italian Corps of Engineers injected mortar to strengthen the base.

1935 年，義大利工程隊在基底注入泥漿， 希望能讓地基更加穩固

However, the mortar wasn’t evenly distributed throughout the foundation,

但是泥漿並沒有 均勻分散在地基每個部分

resulting in another sudden drop.

造成高塔又一次下沉

All these failed attempts, along with the ever-sinking foundation,

屢次失敗的嘗試 再加上持續下沉的基底

moved the tower closer to its tipping point.

讓這座高塔面臨存亡關鍵

And without definitive knowledge of the soil composition,

由於不瞭解土壤組成

engineers couldn’t pinpoint the tower’s fatal angle

工程師無法查明臨界倒塌的傾斜度

or devise a way to stop its fall.

或是任何讓高塔停止下沉的辦法

In the years following WWII,

第二次世界大戰結束不久

researchers developed tests to identify those missing variables.

研究人員設計了方法 用來找出先前無法發現的因素

And in the 1970’s, engineers calculated the curved tower’s center of gravity.

1970 年代，工程師計算出 這座斜塔的重心

With this data and new computing technology,

這些資料和電腦新科技

engineers could model how stiff the soil was, the tower’s trajectory,

讓工程師得以模擬 土壤的軟硬和高塔的軌線

and the exact amount of excavation needed for the tower to remain standing.

也找出應該要挖除的份量 來確保高塔不至於傾倒

In 1992, the team drilled diagonal tunnels

1992 年，這個團隊 挖鑽出了斜線狀的坑道

to remove 38 cubic meters of soil from under the tower’s north end.

在高塔北端移除了 38 立方公尺的土壤

Then, they temporarily counterbalanced the structure with 600 tons of lead ingots

接著，在用鋼索繫住底座前

before anchoring the base with steel cables.

他們先用 600 頓的鉛塊 暫時平衡整個結構

More than six centuries after its construction,

距離高塔建成，已超過六個世紀

the tower was finally straightened… to a tilt of about four degrees.

高塔終於稍微重回到 大約 4 度的傾斜角度

No one wanted the tower to fall,

大家都希望這座高塔能屹立不搖

but they also didn’t want to lose the landmark’s most famous feature.

卻也不想高塔失去最著名的特色

Today the tower stands at 55– or 56– meters tall,

現在，高塔約 55、56 公尺高

and it should remain stable for at least 300 years

接下來的 300 年 高塔都將穩固佇立於此

as a monument to the beauty of imperfection.

縱有不甚完美之處 仍舊值得世人品味