Chapter 49 Section 3 Preliminary Development of Seawalls in Song and Yuan Dynasties

From the Five Dynasties, the Song Dynasty to the Yuan Dynasty, the seawalls in Jiangsu, Shanghai and Zhejiang had a preliminary development. In the third year of Tianbao (910 A.D.), Qian Liu, the king of Wuyue, built seawalls outside Houchao Gate and Tongjiang Gate in Hangzhou with the "stone pile method".In this method, bamboo is woven into a cage, and stones are placed in the bamboo cage, stacked on the seashore, and piled up to form a sea pond. Then thick wooden stakes are placed in front of and behind the pond for reinforcement, and large stones are laid on it.This kind of new pond, unlike the earthen pond, cannot withstand the erosion of tidal water, and is relatively strong and has better anti-tide performance.However, the bamboo and wood in Shituntang are prone to decay and must be repaired frequently; at the same time, the bulk stones lack overall performance and cannot withstand high tides.People tried to improve it, so a formal stone pond was built.

It was Yu Xianqing, the magistrate of Hangzhou Prefecture, who built the official stone pond earlier.In the third year of Jingyou in the Northern Song Dynasty (AD 1036), he built a stone pond dozens of miles away on the bank of the Hangzhou River.The establishment of the official stone pond is a major progress in the technology of pond construction.Yutang is a wall-standing stone pond, which is built with strips of stone facing the sea. It has a better integrity and is far stronger than earthen ponds and stone ponds.However, because it stands on a wall facing the sea and goes straight up and down, it cannot disperse the tidal force when it is impacted by the tide, so it is still easy to be washed away.

A few years later, in the fourth year of Qingli in the Northern Song Dynasty (AD 1044), Tian Yu, the transfer envoy, and Yang Kai, the governor of Hangzhou Prefecture, made major reforms on the basis of Yutang. Xinshitang.It is built with strips of stone, each four feet high and wide, and the stone masonry on the tidal side is retracted layer by layer, forming a pond shape with a wide bottom and a narrow top.The foot of the pond is protected by bamboo cages filled with stones to prevent the tide from damaging the foundation of the pond.An earth embankment is built on the back of the sea to reinforce the stone pond and prevent seepage of salty tide.It can be said that its structure has been quite advanced.

Not long after Yu Xianqing, Tian Yu and others built stone ponds near Hangzhou, Wang Anshi, the county magistrate of Yin County (where the government is located in today's Ningbo City), also built stone ponds in some areas on the south bank of the Qiantang River.His stone pond is called Potuotang, which is built with crushed stones and slopes towards the sea, and then covered with oblique long stones.Although this kind of stone pond has the effect of reducing water potential, it cannot withstand the impact of high tide because of its lax structure. During the Northern Song Dynasty, the famous "Fan Gong Dike" was built along the coast of northern Jiangsu.At that time, the old Tongzhou-Yancheng embankment of Tang Li Chengxiu had collapsed.In the first year of Tiansheng (1023 A.D.), Fan Zhongyan was appointed as a salt official in Xixi, Taizhou. He proposed to repair and expand the Tang embankment, and was supported by Zhang Lun, deputy envoy of transshipment.Under the presidency of Fan and Zhang, the project was successfully completed, known as "Fan Gongdi".It starts from Tongzhou in the south, passes through Dongtai and Yancheng in the middle, and ends in Dafeng County in the north, with a total length of 180 miles.Later, during the Zhihe period of the Northern Song Dynasty (1054-1056 A.D.), the county magistrate of Haimen sank and extended the Fangong dike 70 miles southward, known as "Shengong dike".The two dikes played an important role in defending the farmland and salt stoves in northern Jiangsu, and were valued by successive dynasties.

The Southern Song and Yuan Dynasties also made many achievements in the construction of seawalls.In the 15th year of Jiading in the Southern Song Dynasty (1222 A.D.), Liu Hou [hou Hou] was promoted in western Zhejiang and established Tubeitang and Beitang River in the local area.It is not far from the inner side of the stone pond, and another river channel is dug, which is called Beitang River; with the excavated soil, another earthen pond is built on the inner side of the river, called Tubeitang.The function of Beitang River and Tubeitang can usually separate the farmland from the salty tide and prevent land salinization; once the stone pond outside is washed away by the tide, the Beitang River can absorb the tidal water and discharge it back into the sea. The Tubei pond becomes the second line of defense against the tide, which can intercept the tide that is at the end of its battle.

On both sides of Hangzhou Bay, the Yuan Dynasty carried out large-scale construction of stone ponds.On the north bank, a 150-mile-long stone pond was built, starting from Haiyan in the south and ending in Songjiang in the north.In Yuyao and Shangyu areas on the south bank, local officials Ye Heng, Wang Yong and others also built stone ponds of more than 4,000 feet.When they built these stone ponds, they still had many innovations in technology.One is to deal with the foundation of the pond. Wooden piles with a diameter of one foot and a length of eight feet are driven into the soil to make the foundation of the pond stronger and less likely to be swept away by the tide.Second, when building the body of the pond with strips of stone, the method of criss-crossing and criss-crossing is adopted, and the stone pond is built layer by layer to make the overall structure of the stone pond better.The third is to build a layer of crushed stone and a layer of soil on the back of the stone pond to strengthen the moisture resistance of the stone pond.This kind of stone pond structure is relatively complete, and it is the predecessor of the stone pond in the Ming and Qing Dynasties.

The Yuan Dynasty also repaired and expanded the "Fan Gong Dike" and "Shen Gong Dike" in northern Jiangsu, extending the length of the two dikes to more than 300 miles.