Chapter 519: A common task, building a simple pontoon
As most of the Wei army led by Cheng Xi crossed the river, they were closer to the battle. For them, fighting has become a common occurrence...
Although the pontoon bridge was built as wide as possible, it was still a bit narrow for 10,000 people. It took Cheng Xi's entire army of 10,000 people to cross the pontoon bridge for a full two-quarters of an hour. Only then did all 10,000 people cross the bridge.
liaohe,
What should the ancients do when they could not or had difficulty building piers and beams in deep water, but needed to cross a wide and fast river?
The first method is, of course, to take a boat; the second, more long-term method is to place a number of boats or floating bodies on the water surface and connect them into a channel. This is a pontoon bridge.
The pontoon bridge is the earliest long bridge that the ancients could build, and it was an engineering pioneering work by the ancients to overcome the dangers of rivers.
Even though there were bridges such as stone bridges later, which were most used in wars, the most convenient ones were floating bridges.
The earliest bridge recorded in historical records around the world is the floating bridge.
"The Book of Songs? Daya? Ming Dynasty" says: "King Wen Jiazhi, a great state has a son. A great state has a son, the sister of Qian Tian. Wen Dingjue is auspicious, and he personally welcomes Wei. He builds boats as beams, but does not show his glory.
"
It is said that King Wen of Zhou personally went to the Wei River to marry a beautiful Yin Shang girl.
For their wedding, a pontoon was built on the water. Looking around, there was a scene of boats connecting with each other, which was grand and solemn.
Gu Jiegang believes: "The history of floating bridges in our country is estimated to be at least three to four thousand years ago."
However, Joseph Needham believed that it was "appropriate enough" that the pontoon bridge originated from the 8th to 7th centuries BC.
In 257 BC, King Zhaoxiang of Qin was the first to build a "river bridge" (i.e. floating bridge) at Pujin Ferry on the Yellow River (near the ancient Puzhou City in Yongji City, Shanxi today).
The first bridge built by the ancients on the Yangtze River was also a floating bridge.
"Book of the Later Han·Cen Peng Biography" records that in the 11th year of Jianwu in the Eastern Han Dynasty (AD 35), Gongsun Shu, a separatist force in Sichuan, in order to prevent the Han army from entering Shu, "floating bridges, towers, and pillars were erected across the river near today's Yichang"
Cut off the waterway and build a camp on the mountain to resist the Han soldiers." It was later destroyed by Liu Xiu's subordinate Cen Peng with a fire attack.
In the Han Dynasty, pontoon bridge construction technology had matured and was widely used.
However, because pontoons are made of perishable wooden planks, it is rare for them to last for decades, and even more rare for them to last for hundreds of years (requiring frequent repairs and updates).
Ancient floating bridges had different styles. In "Erya·Shishui", it is said that "the emperor built boats, princes maintained boats, officials' boats, scholars' boats, and common people rode".
"Building a boat" refers to placing the hulls of the boats along the river closely together and "laying the planks on them";
"Weizhou" refers to the use of three or four boats to form a floating unit;
"Ark" is two boats made into one, that is, the catamaran that appeared in ancient times is used as a floating body;
"Tezhou" refers to using a boat as a floating body; "Cheng" refers to using (wooden, bamboo) rafts connected together, which is the simplest pontoon.
From an engineering point of view, such division mainly depends on the number and type of boats used to build pontoons.
As for which type of pontoon should be used by which class of people, it is probably an attachment of later generations of Confucian scholars to maintain the etiquette system, and it may be difficult to implement.
Ancient floating bridges also had different structures, mainly including "curved floating bridge" and "straight floating bridge".
Curved floating bridges are usually suitable for rivers with deep water and unstable river beds.
Each hull of the curved pontoon does not need to be anchored to the bottom of the river individually with anchors or anchors. Instead, large cables are used to maintain each ship, and the large cables are tied to the piles on both sides.
Under the impact of water flow, the pontoon naturally bends downstream to form a curved pontoon. In the early days, rattan, bamboo, brown, etc. were used as materials for large cables, and later iron chains were used.
In order to control the plane displacement of the pontoon bridge from being too large to facilitate passage, in some rivers with shallow water, slow flow speed and stable river bed, each hull of the pontoon bridge can be anchored individually to the bottom of the river to form a straight pontoon bridge.
Even so, it is usually necessary to use cables to cross-connect the bows and sterns of each ship, or to tie the hull at the end of the pontoon diagonally to the shore for stability.
In addition, in order to connect the pontoon bridge to both banks and adapt to the fluctuation of water levels, springboards and trestles need to be installed on both banks.
In order not to hinder navigation, this can be achieved by removing boards from the pontoon, moving ships or setting up tall boats.
According to the length of use, pontoons can be divided into permanent pontoons (the service life is determined according to the bridge design specifications, usually 50-100 years), semi-permanent pontoons (which need to be dismantled under special circumstances or special seasons, and can be maintained for a long time after repair and renewal)
time) and temporary pontoons (installed and dismantled at any time, used temporarily without long-term plans).
Compared with fixed bridges, floating bridges have their advantages and disadvantages.
The advantages of floating bridges are threefold:
The first is its simple structure. A pontoon bridge usually consists of four parts - a floating body, a beam plate, a cable and an anchoring device on the shore or in the water.
The second is that it is easy to assemble and disassemble (except for permanent pontoons). After the erection preparations are completed, the erection can be completed in a few days, a few hours or even shorter; similarly, it is also convenient to dismantle.
The third is cost-effectiveness. Floating bridges do not need to set up underwater foundations and piers, and the construction period is short. Although future maintenance costs may be expensive, the construction cost is usually much lower than that of fixed bridges.
The shortcomings of the floating bridge are mainly poor environmental adaptability, which is reflected in these two points:
The first is that it is susceptible to adverse effects caused by changes in the natural environment (related to hydrology and weather), resulting in a reduction in the safety or traffic capacity of the floating bridge;
The second is the installation of a floating bridge with an open structure, which has a certain impact on both water and bridge traffic, but these two shortcomings are not enough to affect the large-scale use of temporary floating bridges in wars.
Permanent or semi-permanent floating bridges have a long service life and are highly likely to encounter drastic changes in the environment. Therefore, from design and construction to operation and maintenance, more attention needs to be paid to environmental adaptability issues.
In Shoushan, which is ten miles away, the Wu troops led by Qin Dan and Du De have already laid an ambush in the dense woods on both sides of the valley in Shoushan, waiting for the Wei army to enter the valley...
Two quarters of an hour later, both sides of the valley in Shoushan were quiet, except for the chirping of birds in the forest above the mountainside, which was not disturbed by the Wu army below the mountainside. This was deliberately arranged by Qin Dan and Du De.
As early as a few days ago when the Wu army arrived here, Qin Dan and Du De issued a military order that the large group of troops could only move below the mountainside and could not go up the mountainside. Even if they were making rolling logs and looking for stones, they could only move around.
Do it on the other side of the mountain. Do not leave any traces in the valley. This will violate military law!
Qin Dan and Du De's move was not to protect their benefactor's secluded place, but to better capture all the Wei troops who were coming to support them.
The Wei army's forward cavalry had arrived at the mouth of the valley. The Wei army's cavalry reined in their horses and stopped at the mouth of the valley. Cheng Xi also pulled the reins and said, "Hey!" Cheng Xi and the horses under the forward cavalry stopped running, and the horses kept spraying from their nostrils.