Guarding the Golden Waterway: Sisters of Dredging Ships in the Yangtze River Estuary Dredging 183 million cubic meters of dredgers in Ten Years | Yangtze River Estuary

On July 10, 2023, at the mouth of the Yangtze River, which has entered the flood season, two engineering ships deployed their huge mechanical arms on both sides of the ship's hull, suction rakes straight into the bottom of the river, and extracted sediment into mud tanks for separation and treatment.

This is the maintenance and construction work of the specialized drag suction dredgers "Changjiang Estuary 01" and "Changjiang Estuary 02" in the Yangtze River Estuary waterway. These sister ships are stationed at Changjiangkou, bearing the heavy responsibility of clearing the sand barrier and guarding the water depth line, ensuring the smooth and unobstructed flow of the "Golden Waterway" of the Yangtze River.

The governance of the Yangtze River Estuary is known as a world-class challenge, where the water situation is complex and the maintenance and dredging of waterways have their own unique characteristics. "The water depth line is the lifeline, and the management of the Yangtze River Estuary deep-water waterway not only needs to be dug out, but also needs to be preserved!" Ren Jianhua, the director of the Yangtze River Estuary Waterway Management Bureau, said that when the Yangtze River Estuary intersects with the sea, the sediment is often sandwiched up and down, and the sediment in the waterway is often just dug out, and new sediment immediately rushes in, repeating the cycle.

Based on this, the Yangtze River Estuary Waterway Management Bureau successively built and put into use two specialized rake suction vessels, "Yangtze River Estuary 01 and 02", in 2012 and 2013.

During the operation of the main waterway at the mouth of the Yangtze River, the two ships, "Changjiang Estuary 01" and "Changjiang Estuary 02", occasionally passed by. They have the characteristics of high efficiency, fast avoidance, shallow draft, large cabin capacity, large size, small excavation depth, and flexible operation.

The dredger enters the trench for online operation and lowers the rake for dredging. The dredging process utilizes the high-pressure flushing and loosening of the rake head and the cutting of the rake teeth to excavate the soil layer, form mud, and discharge it into the mud tank through a centrifugal mud pump.

Diagram of the operation of the 12000 square meter suction dredger at the mouth of the Yangtze River during dredging.

Under the collaboration of top Dutch ship design companies, the "Yangtze River Estuary" type 12000 square meter suction dredger with the characteristics of "one specialty, two highs, and two lows" has emerged——

It has a large bulbous bow and a double tail fin structure at the stern, which suppresses waves, has a short body, and good turning ability. When a heavy-duty ship is at full speed, the turning diameter is about twice that of the captain; The design of twin pods at the stern of the ship optimizes the propeller water flow and static stern tilt, avoiding excessive draft at the bow during high-speed navigation. Two efficient and fast operating fish stern rudders can further improve airworthiness and operational performance;

A matching design has been carried out for the mud pump, rake head, suction conveying pipeline system, and energy dissipation device, which has low flow rate and high concentration suction capacity. The effective loading time is only 55 minutes. Due to the high concentration of suction mud, the loading efficiency has been greatly improved, thereby improving production capacity and efficiency;

The two main engines of the ship adopt a "one to three" design, which simultaneously drives the propeller, generator, and mud pump, and has three major functions of navigation, power generation, and construction, allowing the two ships to freely switch between dredging operations, avoiding ships, and fighting against wind and waves, significantly improving ship mobility and reducing ship energy consumption.

The extracted mud is separated and treated in the mud tank, and when the tank is full, the rake is collected and returned to the dumping point. After unloading the mud, the high-pressure water gun washes the mud tank clean to increase its capacity, and the patrol operation is repeated.

The crew confirms the position of the incoming line and the dredging route based on electronic nautical charts and navigational aids, and actively notifies the incoming and outgoing ships that "my ship needs to lower the rake for dredging" to ensure safety. The construction process is achieved through computer remote control and touch screen operation.

The dredger threw mud into the land reclamation area of Hengsha Island, promoting its continuous expansion.

According to statistics, since its ten-year operation, the two ships "Yangtze River Estuary 01 and 02" have safely and stably operated for over 110000 hours, with a cumulative dredging volume of over 183 million cubic meters, accounting for 30% of the total dredging volume for the maintenance of the Yangtze River Estuary deep-water channel during the same period. The cleared sediment is used to build land using the Hengsha Island cofferdam, and the Hengsha Island continues to grow.

Over the past decade, there have been over 600000 ships passing through the 12.5 meter deep-water channel at the mouth of the Yangtze River, with a cargo throughput of over 13 billion tons. It is estimated that the annual economic benefits generated by shipping exceed 12 billion yuan. The increase in freight volume has driven GDP growth of over 130 billion yuan per year, driven fiscal revenue growth of over 20 billion yuan per year, and driven employment of over 100000 people per year.