By Lei Chuang, Liu Xinhong & Zhang Qishan

Overspending nearly two hundred million yuan, China’s building the world’s first fully-enclosed sound barrier railway

Jiangmen, Guangdong Province. The Shenzhen-Maoming high-speed railway is under construction.

The main construction for a fully enclosed sound barrier designed by the China Railway Siyuan Survey and Design Group (hereinafter referred to as “SIYUAN”) was completed in December of 2017.The sound barrier runs 2.03 kilometers in length and is specially designed for the “Birds’ Paradise” 800 meters away from the rail. It’s the world’s first fully enclosed sound barrier for a high-speed rail.

Overspending 187 million yuan, more than 40,000 sound panels have been constructed to avoid disturbing the birds with the noise from passing trains

On December 15, we went to the construction site in the district of Xinhui in Jiangmen City of Guangdong Province. Peering from afar, an arched corridor about 20 meters tall over the rail sat over the rail—this was the fully enclosed sound barrier.

多花近兩億，建造全球首段高鐵全封閉聲屏障

廣東江門市境內(nèi)，深圳至茂名的高速鐵路。

一段由鐵四院設(shè)計(jì)、全封閉式聲屏障主體工程，2017年12月完工。這一聲屏障全長2.03公里的，專為800米之外的“小鳥天堂”而設(shè)。它是世界首例高鐵全封閉聲屏障。

多花1.87億，鋪4萬多塊隔音板讓鳥兒聽不到噪音

12月15日，筆者來到廣東省江門市新會(huì)區(qū)施工現(xiàn)場，遠(yuǎn)遠(yuǎn)望去，只見一條高20米的拱形“長廊”盤踞在鐵軌上方，它就是全封閉聲屏障。

800米外，就是著名的“小鳥天堂”。那里是座約1萬平方米的小島，周圍湖水環(huán)繞。島上，榕樹密布。那里，棲息著夜鷺、牛背鷺和小白鷺，共96種3萬多只鳥，其中8種國家二級重點(diǎn)保護(hù)鳥類，15種廣東省重點(diǎn)保護(hù)的鳥類，還有54種按照中日候鳥保護(hù)協(xié)定、中澳候鳥保護(hù)協(xié)定覆蓋的鳥兒。

1933年，作家巴金先生來到這里游覽，寫出散文名篇《鳥的天堂》，“小鳥天堂”由此得名，并成為大型的天然賞鳥樂園。

“隔音板上怎么有這么多小孔？”筆者問。

“這是特殊的隔音板，厚度為8厘米，比普通隔音板薄4厘米，但隔音、防風(fēng)的效果更好?！辫F四院環(huán)工處總工程師王忠合介紹，隔音板分為三層，最里層打了很多均勻的小孔，讓聲音穿透到第二層；第二層為吸音層，將噪音最大程度吸收、消解；最外層為防風(fēng)層，可以抵御14級臺風(fēng)。

“鐵路通車后，聲音傳到‘小鳥天堂’核心區(qū)，比過去只增加0.2分貝，對小鳥休憩、覓食完全沒有影響?！蓖踔液险f，這段全封閉聲障屏共使用4萬多塊隔音板，比普通的半封閉式聲障屏造價(jià)高出1.87億元。

耗時(shí)兩年，50多人團(tuán)隊(duì)攻關(guān)破解多種技術(shù)難題

傍晚，筆者跟隨鐵四院設(shè)計(jì)人員乘船探訪。清澈透明的湖水環(huán)繞著小島，鳥兒們“嘰嘰喳喳”的，它們有的站在樹枝上唱歌，有的貼著湖水嬉戲。

2014年8月，鐵四院開始負(fù)責(zé)深茂高鐵的設(shè)計(jì)，設(shè)計(jì)時(shí)速200公里，在江門境內(nèi)經(jīng)過“小鳥天堂”。中國環(huán)保部明確要求：鐵路通過“小鳥天堂”區(qū)段時(shí)，要設(shè)置全封閉聲屏障和遮光板，確保不影響鳥類的棲息與覓食?！案哞F上建全封閉聲屏障，在全世界還沒有先例?！辫F四院橋梁院副總工程師劉振標(biāo)說，該院聯(lián)合國內(nèi)一些知名高校，組成50多人的專家團(tuán)隊(duì)，進(jìn)行兩年多的研究，最終解決了各種技術(shù)難題。

專家們發(fā)現(xiàn)鳥類休息、覓食，主要集中在東、西、南三個(gè)方向，因此將線路走向定在“小鳥天堂”北面，避免對其生活產(chǎn)生干擾；橋梁與橋墩的銜接部分使用橡膠，減少火車經(jīng)過時(shí)產(chǎn)生的震動(dòng)；反復(fù)設(shè)計(jì)屏障內(nèi)外風(fēng)力，最終敲定拱形聲屏障抗風(fēng)效果最好。

為了不影響鳥類的正常生活，噪聲必須低于50分貝，全封閉聲障屏安裝后，高鐵通過時(shí)傳到“小鳥天堂”的噪音，降至49.3分貝，符合環(huán)保部要求。

這段全球首例高鐵全封閉聲屏障，填補(bǔ)世界空白，對推動(dòng)中國高鐵建設(shè)及走出國門具有重要意義。

800 meters away from here is the famous “Birds’Paradise.” It is a small island covering an area of 10,000 square meters and surrounded by a lake.The island is densely covered with banyan trees and is home to more than 30,000 birds of 96 species,including night herons, cattle egrets, and little egrets. Of all these birds, 8 species belong to the state’s Class II specially protected species, while 15 are specially protected birds in Guangdong, and the other 54 are included in the species covered by China-Japan Migrant Bird Protection Agreement and China-Australia Migrant Bird Protection Agreement.

In 1933, the famous Chinese writer Ba Jin (1904-2005), author of Family, came to this site for a visit and wrote a well-known article: “The Paradise of Birds,” which is where the island got its name “The Birds’ Paradise” and became a large natural park for watching birds.

“Why are there so many small holes on the sound panels?” I asked.

“This is a type of special sound panel. With a thickness of only 8 centimeters, just half of the thickness of an ordinary one, however, its effects of sound insulation and wind protection are better,”said Chief Engineer Wang Zhonghe from SIYUAN Environmental Engineering Design and Research Department. According to Mr. Wang, the sound panel is a type of three-layered board, with the inner layer filled with many holes of equal size to allow the sound to penetrate into the second layer. The second layer, being the sound absorbing layer, will absorb and dispel the noise to the maximum degree. The outermost layer is the wind-proof layer, which is able to withstand even a strong typhoon.

“When trains are running, the sound of the rail reaching the core area of the Birds’ Paradise will only be slightly raised by 0.2 decibels, compared to the past. It won’t affect the birds’ rest and foraging in the least,” said Wang Zhonghe, “In total, it took over 40,000 sound panels for this fully-enclosed sound barrier, costing 187 million yuan more than an ordinary semi-enclosed sound barrier.”

A team of over 50 experts conducted research work for two years to ultimately tackle various technical problems

On the evening of the same day, we visited the Birds’ Paradise with the designers from SIYUAN by ship. With crystal water surrounding the island, the birds were chirping happily, some were singing on the branches, while others were playing on the lake.

In August of 2014, SIYUAN embarked on the design of the Shenzhen-Maoming high-speed railway, which would pass by the Birds’ Paradise when passing through Jiangmen. Its designed speed reaches 200 kilometers per hour. So, the Ministry of Environmental Protection required explicitly that a fully enclosed sound barrier and sun visor should be installed in the zone of the Birds’ Paradise to ensure that the birds’ resting and foraging would not be disturbed.

“It’s unprecedented to build a fully enclosed sound barrier on the high-speed rail,” said Mr. Liu Zhenbiao, deputy chief engineer of SIYUAN Bridge Design and Research Department. To tackle the problem, the department allied with some famous universities in China and formed a team of over 50 experts. After more than two years of research, they finally overcame various technical problems.

The experts found that the birds resting and foraging sites were mainly concentrated in three parts of the island—that is, the east,the west, and the south. So they decided to set the railway route to the north of the Birds’ Paradise to avoid disturbing the birds’life; rubber would be used for the joints between the bridge and the pier to relieve the shake from a running train. After repeated measurements of the wind force both inside and outside the sound barrier, they decided on the arched sound barrier in the end.

In order not to affect the birds’ normal life, the noise levels must be lower than 50 decibels. With the fully enclosed sound barrier installed, when the high-speed train passes, the noise reaching the Birds’ Paradise is reduced to 49.3 decibels, meeting the requirements of the Ministry of Environmental Protection.

The world’s first fully enclosed sound barrier on a high-speed railway fills a void in the industry and will surely be put to use in other ways around the world. It is of great significance for promoting China’s high-speed rail construction and its overseas market. (Translation: Liu Jie)