Urgent repair to ensure safety of Thao Long dam

Thao Long dam to prevent saltwater and keep fresh water located on the lower Huong River (Hue City) was started construction in August 8, completed and put into operation in June 2001, with total investment of 6 billion VND.

The scale of the project includes a salt-preventing sluice designed with an aperture of 480,5m, including 15 compartments, each 31,5m wide and a lock compartment. The traffic bridge is designed with a bridge deck of 10m wide. The lower shaft valve gate is made of CT3 steel, the closing and opening of the valve is done by a hydraulic cylinder system.

Since being put into use, the project has promoted the main task of preventing salinity and keeping fresh for the Perfume and Bo river systems, ensuring sufficient water supply for agricultural, industrial and people's production. in the local area. At the same time, contributing to improving the ecological environment and tourist landscape in the Perfume River and Tam Giang lagoon.

However, there are still some inadequacies, the valves made of CT3 steel, hydraulic equipment, electrical and electronic equipment installed outdoors, are subject to many adverse impacts of saline and humid environments. , lightning should also be easily damaged over time.

According to the Provincial Irrigation Works Management and Exploitation One Member State Company Limited (Irrigation Company) - the management unit of the Thao Long dam to prevent saltwater and keep fresh water, the project is now degraded and damaged, especially, due to lack of water. The valve is designed as a backup valve, so in the event of a failure, the valve cannot be closed or opened, causing great consequences.

The current status of the upstream and downstream sluice gates to prevent saline intrusion has been deposited in a large volume, up to thousands of m3 per year on average, causing congestion and obstruction of the flow. Every year, the Irrigation Company organizes dredging a part of the culvert downstream to handle the jam. The two abutments on the north and south banks of the sluice also subsided, located from +1.2 to +0.8 elevation.

Most of the sluice gates have erosion phenomenon under the bottom girder piles, the flow through is very large, affecting the work of preventing salinity, keeping fresh and in the long run, destabilizing the works. The part adjacent to the road and traffic bridge abutment has subsided, cracked, affecting the traffic process, the roof protecting the abutment protection on the South bank, the North bank has been subsided and damaged, although this has been approved by the Public side. Joint Stock Company Road Management and Construction of the province temporarily overcome but still face many safety risks.

In addition, the valve gate with beam structure and the door face plate is made of CT3 steel, which has now rusted and corroded due to working in a saline environment, the face plate has many points of corrosion 3-4mm, only remaining 6-7mm. The shaft assembly system under the valve gate (12 shaft assemblies / 1 door) has leaked, corroded, damaged leading to the shaft sliding out of position. Annually, through inspection by the Irrigation Company, there are doors that slip up to 3 -4/12 axle assemblies cause unsafety during construction operation.

Currently, the hydraulic system to open and close the valve gates has been degraded, damaged, most of the doors open and close very slowly (the opening or closing time is up to 30 minutes instead of less than 10 minutes as in the early years). into operation). Some doors sometimes fail to close and open to regulate water sources, forcing the company to temporarily handle it by dismantling the hydraulic system of another door to replace it, so it is very unsafe...

Mr. Do Van Dinh, Chairman of the Irrigation Company, said that the scale and tasks of the project are very important, but the local budget is limited. Investing capital for maintenance and repair work in order to prevent deterioration and ensure stable operation to meet tasks is essential today.

Recently, the Ministry of Agriculture and Rural Development has decided to approve the project component No. 8: Urgent repair to ensure safety of Thao Long dam (under the urgent repair project to ensure the safety of reservoirs and dams) and assign the Management Board to Management of investment projects on construction of agricultural and rural projects in the province as an investor with a total investment of more than 348 billion VND.

The urgent repair project to ensure the safety of Thao Long dam will be waterproofing the foundation of the dam with Larsen IV steel piles from compartment 1 to the end of compartment 15, with a length of 495m. Combining construction piles as waterproofing piles with a depth of 13m waterproof pile. Treatment of voids under the valve girders by high-pressure injection of sand-cement mixture. Reinforcement of scour pits and downstream conduits with flint, gabion layer within 24m for 6 north bank compartments and 44m for 9 south bank compartments.

The mechanical part, replacing 6 valve gates and overhauling and repairing 9 valve gates. Replace all bottom and side watertight assemblies at 15 doors. Structure of watertight assembly of Sus304 steel, bearing bolts of stainless steel, watertight by sheet rubber and garlic rubber. The arrangement of watertight assemblies on the side and bottom is convenient for repairing, replacing gaskets and maintaining valve doors.

Lock compartment, replace the upper and lower lock doors with stainless steel; die shaft, bearing bolts are manufactured, replaced by high-strength stainless steel; watertight with sheet rubber and garlic rubber. Replace the closed cylinder system, open the main valve door and the door of the water supply and drain valve in the chamber.

In addition, upgrading and repairing the electrical system controlling the valves at the construction site and the manager. Repair and upgrade the management house, embankment combined with the road to manage the two ends of the Thao Long dam. Decorate traffic bridges, lighting systems, signs. Building a monitoring system for project management and operation.