How can the Lugou Bridge, with a history of over 800 years, resist floods? This unique structure makes it stand firm in Lugou | Beijing | Construction

Some time ago, affected by typhoon "Dousuri", some parts of Beijing suffered from extremely heavy rainstorm. In this rainstorm, Lugou Bridge, which has a history of more than 800 years, stood still after the flood.

The unique flood control structure of Lugou Bridge, known as the "water diversion point," has always been talked about by people. In fact, during the construction of the Lugou Bridge, there were many highly scientific and ingenious ideas from the piers to the bridge body, which have kept the stone bridge safe to this day and also reflect the wisdom of the ancients.

The ancient ferry is a transportation hub

The Lugou Bridge, located on the Yongding River in the southwest of Beijing, is the oldest existing ancient bridge in Beijing. As the Yongding River was formerly named Lugou River, this ancient bridge is named Lugou Bridge. This ancient bridge, spanning over 800 years, not only has a sturdy body, but its appearance is also very exquisite. In fact, from the beginning of its construction, it was related to the frequent floods in the Yongding River.

Yongding River, also known as Lugou River, has the meaning of black. In the Jin Dynasty, it was called "Heishui River". In the "Beiyuanlu" of the Song Dynasty, it was recorded that "the Lugou River, also known as the Heishui River, has the most turbid color and is as swift as an arrow." This sentence vividly describes the water flow of the Lugou River. In the Ming Dynasty, due to the frequent flooding of the river, it posed a great threat to the lives and property of the people along the coast, and was also known as the "Wuding River". In the 37th year of the Kangxi reign of the Qing Dynasty, the Governor of Zhili, Yu Chenglong, led thousands of migrant workers to dredge the river, which alleviated the flooding of the Lugou River. Emperor Kangxi named the governed Wuding River "Yongding River".

This river has been valued by emperors throughout history for hundreds of years, not only due to frequent floods, but also due to its unique geographical location. In ancient times, ethnic minorities in the north arrived at the Beijing Plain from the the Inner Mongolian Plateau and the Northeast Plain, mostly going south along the platform between the mountains at the eastern foot of the Taihang Mountains and passing the Yongding River. From the small Beijing Plain to the North China Plain and the Central Plains, you must also cross the Yongding River. The Yongding River flows down from Xishan and reaches the area of Lugou Bridge, where the river channel is the narrowest, thus forming a ferry early on. This ancient ferry has always been an important hub for north-south transportation. But when floods occur, this becomes the biggest obstacle.

According to Xu Kangzong, the envoy of the Song Dynasty, the itinerary of the envoy to Xuanhe Yisi recorded: "When crossing the Lugou River, the water is extremely turbulent. The Yan people set up small bridges to cross the river when the water is shallow and deep. In recent years, the Metropolitan Water Administration has often built floating bridges on both sides of the river." This also records the scene of people using floating bridges to travel between the two sides of the Yongding River at that time.

In the fifth year of the Jin Tiande reign, Wanyan Liang established the capital of Jicheng and named it Zhongdu. In order to meet the growing needs of military and economic development, and to change the current situation of temporary construction of floating bridges and boat crossings, Wanyan Liang decided to build a strong bridge on the Lugou River for easy passage. But the final bridge was built during the reign of Emperor Zhangzong of Jin Dynasty.

"In May of the 28th year, an edict was issued to the Lugou River envoy to travel to Jinyao and build a stone bridge. However, before they could proceed, Emperor Shizong collapsed. In June of the 29th year of Emperor Zhangzong's reign, he ordered the construction of a boat and a stone bridge to be built. The edict was completed in March of the third year of Mingchang and named Guangli."

The above meaning is that for the needs of communication between the two banks of the river, Emperor Jin Shizong ordered the construction of a stone bridge. Unexpectedly, before the bridge was built, Emperor Jin passed away. In the second year, Jin Zhangzong ascended to the throne. Due to the turbulent flow of the Lugou River, Emperor Jin Zhangzong ordered the construction of boats and boats to cross the river, and thus decided once again to build a stone bridge. After three years of construction, by March of the third year of Mingchang, a new stone bridge was completed and named Guangli Bridge. This is what later became known as the Lugou Bridge.

Advanced flood control concept of ancient bridges

This stone bridge is 266.5 meters long and 9.3 meters wide. The bridge deck is 213.15 meters long, with a net width of 7.5 meters. The center is slightly higher than the east and west ends, and the slope is gentle. There are 11 circular arches under the bridge to divert water from the north, and the top of the 3 arches in the middle is carved with exquisite water absorbing beasts on both sides.

The entire bridge is constructed of white stone, with 10 piers in the north and 10 piers in the south. The bridge deck is carved with stone railings, engraved with pillars of hope, and the top is exquisitely carved with a son and mother stone lion. There is a pair of stone beasts on each wing of the bridge, with stone elephants to the west and stone lions to the east. The stone bridge has two pairs of ornamental column, standing at both ends of the bridge.

When constructing this stone bridge, the Jin people perfectly and scientifically applied the principles of hydraulic engineering, making the bridge very sturdy. This is reflected in many aspects.

Firstly, there are bridge piers. In order to make the bridge piers sturdy and durable, craftsmen drove several thick iron pillars into the pebble layer at the bottom of the river, and then inserted giant stones on top, connecting the two into a whole and building the bridge piers. This design, due to the significant weight of the bridge deck and railing stones, makes the bridge piers very stable. This is also an important reason why the stone bridge has been unaffected by multiple floods for over 800 years. Nowadays, after on-site measurements by experts, the 10 piers of Lugou Bridge have almost no settlement.

Next is the distance between bridge piers. The spacing between bridge piers gradually increases from both ends to the center. The distance between the piers on both sides of the central hole is 21.35 meters, while the distance between the piers on the east and west sides is 16.49 meters and 16.64 meters, which is conducive to maintaining the strength of the bridge body. Correspondingly, the span between the 11 bridge openings of Lugou Bridge gradually increases from both sides towards the center of the bridge. The span of the bridge opening continues to increase, and this design is also rare in the history of arch stone bridge construction in China.

In order to enhance the stability of the bridge body, the entire bridge adopts a longitudinal arch construction method, which connects the 11 arches of the bridge into one unit; The connection between the bridge pier and the arch was reinforced with waist iron and iron components; The interior of each bridge pier is connected by iron work up and down... A series of meticulous designs make this ancient stone bridge exceptionally sturdy in terms of architectural structure.

Again, in addition to the overall design of the stone bridge, there are also many clever designs in the details of each pier. For example, each pier has a ship shaped plane, and the facing side is built into a wedge-shaped "water diversion point". The water splitting point can reach a height of 4.5 to 5.2 meters. A triangular iron pillar with a side length of 26 centimeters is installed in front of each "water dividing point", which uses sharp angles to face floods and ice, playing a role in protecting the bridge piers and body. People give it a resounding name: "Dragon Slaying Sword".

In order to make the "water diversion point" more stable, six layers of laminated stone were built on top of the "water diversion point" during construction. These six layers of laminated stones, the bottom one and two layers are picked out, and the top four layers gradually inward, with a total thickness of 1.83 meters. The top layer of laminated stones is slightly raised, forming a piano shaped surface. These six layers of laminated stones play a crucial role in balancing the pressure on the entire bridge pier.

Since its construction, Lugou Bridge has stood tall and upright for over 800 years, with a sharp water dividing point and intact piers. It is the wisdom of ancient craftsmen and contains advanced concepts of scientific water management.

In addition, the downstream side of the bridge pier is built into a streamlined shape, resembling the stern of a ship, which quickly disperses the flood as soon as it exits the bridge opening, greatly reducing the pressure of the flood on the bridge opening.

This stone bridge has been safe and sound for hundreds of years since its construction by Emperor Zhangzong of Jin Dynasty. During the Qing Dynasty, Lugou Bridge underwent renovation, but the original design of the bridge remained unchanged, and the bridge foundation and structure were still from the Jin Dynasty. It is interesting that the lions on the Lugou Bridge have been repaired throughout history and have increased in the process of repair. Therefore, the number of lions varies in different periods, which has formed a folk saying: "The lions on the Lugou Bridge - Countless.".

After generations of repairs, four stone tablets still stand on the banks of the Lugou Bridge. Among them, there is a roofless stele pavilion built by four coiled dragon stone columns on the northeast side of the bridge. The stele in the pavilion is inscribed with the four characters "Lugou Xiaoyue" by Emperor Qianlong of the Qing Dynasty. It was also known as one of the "Eight Scenic Spots of Yanjing".

Due to its solid foundation, in January 1975, a 429 ton oversized flatbed truck safely passed through this ancient stone bridge. In August 1985, 1000 tons of oversized large items passed through the ancient bridge smoothly again in four rounds. This not only tests the bearing capacity of Lugou Bridge, but also demonstrates the superb skills of ancient craftsmen in bridge construction.

Building water reduction dams to discharge floods

A while ago, the author discovered that the Dawang Temple on the west side of Lugou Bridge, along with its mountain gate and theater, has been renovated. This Great King Temple was built in the 21st year of the Guangxu reign of the late Qing Dynasty and was an important project to resist the flood of the Yongding River in 1893. This temple has also become a historical witness to the governance of the Yongding River.

Many years ago, the author came to the Dawang Temple and coincidentally met Grandpa Yan Lianxiang, who lived here. The old man told me that in 1957, he moved from the overpass in the city to this temple with the Beijing Lead Wire Products Factory, and has been living here ever since, experiencing the process of transforming the temple into a factory and then into a residential courtyard. Grandpa Yan said that there were two tall stone tablets on both sides of the east and west in front of the main hall, which were knocked down in the 1960s and 1970s. At that time, in a state of urgency, Grandpa Yan and his son dragged one of the remaining stones into their own coal shed, while the other stone was buried under a neighbor's kitchen.

The author was able to see this remaining monument, about two meters long and 0.8 meters wide, in the coal shed of Grandpa Yan's house. It stands against the wall and is engraved with words such as "When the water on Lugou Bridge converges and wants to kill it, it is appropriate to divide its flow. Only a water reducing stone dam should be built here", "A Taixi steel bridge should be built on top of the water reducing dam", and "On the east bank of the water reducing dam, the Dawang Temple without beams should be built to commemorate the auspicious occasion of the Tongji deity." The inscription on the monument is "On the 21st year of the Guangxu reign, in the eighth month of the eighth lunar month, the auspicious day stands".

The author consulted the "Continuation of the Water Golden Mirror - Yongding River Compilation" and further explained the content engraved on this monument in the book. In June and July of the 19th year of the Guangxu reign, heavy rain poured down for several days, causing the water of the Yongding River to surge rapidly, and the waves of the water were even more than ten meters higher than the top of the Lugou Bridge. Dozens of stones on the bridge were also washed away; The stone embankment on the west bank of the bridge was washed down more than 40 zhang, and the water from the broken embankment flowed everywhere, causing areas such as Daxing, Liangxiang, and Zhuozhou to collapse into a state of Ze and displaced the disaster victims.

In early 1894, river officials surveyed the upstream and downstream of the Yongding River and studied the treatment plan. They decided to build a water reduction dam on the Xiaoqing River west of the Lugou Bridge to divert the flood of the Yongding River and allow the water to flow into the Xiaoqing River. This project was reported to the imperial court and 300000 taels of silver were allocated. Chinese and French engineering technicians jointly surveyed and designed it. It was agreed that the width of the dam mouth would be reduced by 50 zhang, and the keel, diamond wall, and two stone embankments would be built with large stone materials. The construction period would be completed before the arrival of the flood season.

The project started in February of the 20th year of the Guangxu reign and was completed on May 15th. After passing the acceptance inspection by Chinese and French engineering technicians, the warranty period is three years.

After the construction of the Xiaoqing River's water reduction dam and diamond wall, officials inspecting the river found that "the area is like a passage, with the Fuqiu water reduction dam releasing water, which hinders the travel of literature and newspapers. A steel bridge of fifty zhang in length and sixteen zhang in width will be proposed, which can pass a large vehicle weighing three thousand pounds."

In the autumn of 1894, the steel beam and wooden board bridge spanning the Xiaoqing River was completed. When the flood comes, the newly built water reduction dam releases water very smoothly, and the flood passing through the Lugou Bridge flows smoothly downstream.

After the completion of the project, a grand temple was built on the vacant land east of the steel beam and wooden board bridge and north of the Lugou bridge to celebrate. The Dawang Temple was completed in August of the 21st year of the Guangxu reign. Monuments and trees were carved inside the temple, and the theater was elevated to sing opera. Officials at all levels of river management prayed to the people of dozens of provinces and counties to avoid the harm of floods. The description of "Continuation of the Water Golden Mirror - Yongding River Compilation" coincides with the content engraved on the remaining monument.

In the late Qing Dynasty, a water reduction dam was built on the Xiaoqing River to divert the flood from the main channel of the Yongding River during the flood season, greatly reducing the impact of the flood on the Lugou Bridge and downstream. Therefore, the construction of a water reduction dam, followed by the construction of a diamond wall, the construction of a stone pier, steel beam, and wooden slab bridge, and finally the construction of the Dawang Temple are closely related. It is the crystallization of the wisdom and sweat of the Chinese nation in water governance.

The current Lugou Bridge, like a beautiful rainbow, spans the Yongding River. It has outstanding achievements and status in the history of ancient bridge construction in China, fully demonstrating the intelligence and talent of the ancient laboring people.