What Is a Water Brake?

Construct low-water head hydraulic structures on rivers and channels using gates to control flow and regulate water levels. Closing the gate can block floods, tide, or raise the upstream water level to meet the needs of irrigation, power generation, shipping, aquaculture, environmental protection, industrial and domestic water, etc .; opening the gate can release floods, floods, abandoned water or wastewater, or Provide water to downstream rivers or channels. In water conservancy projects, sluices are widely used as buildings that block, discharge, or fetch water. ^[1]

Chinese name: sluice
Foreign name: Barragesluice

Application: Water project
Application area: Channels, canals, lakes and coastal areas
Set up time: 598 BC

Sluice introduction

Closing the gate can block floods, tide, and store water to raise the upstream water level to meet the needs of upstream water intake or navigation. By opening the gate, flood discharge, drainage, sand flushing, water fetching, or flow can be adjusted according to the needs of downstream water use. Sluices are widely used in water conservancy projects, and are mostly built in rivers, canals, reservoirs, lakes and coastal areas.

Sluice history

China has a long history of building sluices. From 598 BC to 591 BC, Chu Ling Yin Sun Shuao set up five gates to divert water in Jian'ou Irrigation District in Shou County, Anhui Province. In the future, with the improvement of sluice technology and the emergence of new varieties of building materials, sluice construction has also increased. The construction of large-scale modern sluices after 1949 has generally risen in China and has accumulated rich experience. For example, the second river discharge from the Gezhouba junction on the Yangtze River

sluice Brake, with a maximum discharge of 84000km3 / s, ranking first in China and operating well. The technology of sluice construction in the world is also constantly developing and innovating. For example, the East Schelder tide barrier built in the Netherlands, with a height of 53m and a net length of 3km, is known as the Great Wall at Sea (see color picture). At present, the construction of sluices is developing in the direction of diversified forms, lightweight structures, construction and assembly, operation automation and telecontrol.

Sluice type

Sluices, according to their main tasks, can be divided into: control sluices, water intake sluices, sand sluice sluices, flood diversion sluices, tide sluices, and drainage sluices. According to the structure of the lock chamber, it can be divided into: open type, chest wall type and culvert type (Figure 1). Open sluices pass through the sluice when the sluice is fully open, and are suitable for sluices that have mission requirements such as flood discharge, ice discharge, wood crossing, or floating objects. Control sluices and flood diversion sluices commonly use this form. The chest wall sluice and culvert sluice are suitable for the situation where the water level on the sluice is large or the water level is higher than the design level of the sluice hole, that is, the pore size of the sluice is designed according to the low water level through the design flow. The structure of the chest wall gate is basically the same as the open type. In order to reduce the height of the gate and the working bridge or to control the discharge of a single wide flow, a chest wall is used instead of some gates to block the water. Tide gates, inlet gates, and discharge gates are often used in this form. . For example, the Gezhouba sluice gate in China adopts a 12m × 12m movable flat door chest wall, and a 12m × 12m arc-shaped working door below it to meet the need to release large flows when necessary. Culvert sluices are mostly used for diversion (draining) of water through the embankment. The structure of the sluice chamber is a closed culvert. A gate is set at the entrance or exit. Bridges and drainage gates often use this form.

Sluice composition

The sluice consists of a lock chamber, an upstream connection section and a downstream connection section (Figure 2). The sluice chamber is the main body of the sluice, and is provided with a bottom plate, a gate, a hoist, a pier, a chest wall, a working bridge, a traffic bridge, and the like. The gate is used to block water and control the flow through the gate, and the gate pier is used to separate the gate hole and support gate, chest wall, working bridge, traffic bridge, etc. The bottom plate is the foundation of the gate chamber, which transmits the weight and load of the superstructure of the gate chamber to the foundation, and has both anti-seepage and anti-surge functions. The gate chamber is connected to the upstream and downstream connection sections and the two banks or other buildings. The upstream connection section includes: wings installed on both sides of the strait

sluice Walls and slope protection, anti-slots, bottom protection and covering on the river bed are used to guide the water flow smoothly into the lock chamber, protect the banks and the river bed from being washed away by the water, and form a sufficient length of seepage path with the lock chamber to ensure penetration Impermeability of water flow along banks and sluices. The downstream connection section is composed of a stilling pond, tank guard, sea flood, anti-slot, cross-strait wing wall, slope protection, etc., to guide the outflow of the sluice to the downstream to spread evenly, slow down the flow rate, eliminate the remaining kinetic energy of the sluice flow, and prevent water Erosion of the river bed and the banks.

Sluice features

When the sluice closes the door to block water, the sluice chamber will bear the horizontal thrust generated by the water level difference between the upstream and downstream, which may cause the sluice chamber to slide downstream. The design of the lock chamber must ensure sufficient anti-sliding stability. At the same time, due to the difference in upstream and downstream water levels, water will infiltrate from the upstream along the sluice and bypass the connecting buildings to the downstream, creating osmotic pressure, which is detrimental to the stability of the sluice and the connecting buildings on both sides, especially for soil Due to the poor impermeability of the soil, the sluice on the foundation may cause infiltration deformation and endanger the safety of the project. Therefore, factors such as the geological conditions of the sluice site, the difference between the upstream and downstream water levels, the layout of the sluice chamber and the buildings on both sides of the strait, etc. A complete anti-seepage and drainage system is installed upstream and downstream of the sluice chamber to ensure the impermeability of the sluice foundation and the banks. When opening the door to discharge water, the total net width of the gate chamber must ensure that it can pass the design flow. The aperture of the gate should be selected according to the use requirements, the form of the gate and the consideration of project investment. Due to the complicated shape of the water flow across the sluice, the flow velocity is large, and both sides of the river and the river bed are easily washed away by the water flow, and effective energy dissipation and anti-rush measures need to be taken. The arrangement of buildings on both sides of the strait needs to have good contraction and diffusion conditions for water flow in and out of the gate. The foundations of sluices built in the plain area are mostly soft soil foundations, with small bearing capacity and large compressibility. They will be produced under the sluice's own weight and external load.

sluice Subsidence or uneven subsidence can cause the gate chamber or wing wall to sink, tilt, or even cause the structure to break and fail to work properly. Therefore, the design of the structural form, layout and foundation size of the gate chamber and the wing wall should be adapted to the conditions of the foundation, try to make the foundation load uniform, and control the bearing capacity of the foundation within the allowable range. Handle properly. For the strength and stiffness of the structure, the influence of uneven settlement of the foundation must be considered, and the uneven settlement of adjacent buildings should be minimized. In addition, the design of the sluice also requires a simple structure, economical and reasonable, beautiful shape, easy construction, management, and environmental protection.

Sluice design

The main contents of the sluice design are as follows.

The selection of sluice site and sill threshold height is based on the tasks and application requirements of the sluice, and takes into consideration terrain, geology, current, sediment, construction, management, and other factors, and is selected through technical and economic comparison. The sluice site is generally located in a river section where the water flow is smooth, the river bed and bank slope are stable, the foundation is hard and dense, the anti-seepage stability is good, and the site is open. The selection of the elevation of the sill sill should be adapted to the wide flow of the gate. In a water conservancy hub, the reasonable layout of the sluice and other buildings in the hub should be considered in accordance with the nature of the hub project and the comprehensive utilization requirements, and the sluice site and sill threshold elevation should be determined.

Sluice hydraulic

Hydraulic design calculates the flow capacity according to the hydraulic formula according to the operation mode of the sluice and the flow pattern of the sluice, and determines the total net width of the sluice hole. Based on the water level under the sluice and the geological conditions of the river bed, the energy dissipation method is selected. The sluices dissipate energy with water jumps, and determine the size and arrangement of energy dissipation and anti-scouring facilities through hydraulic calculation. It is estimated that after the sluice is put into use, the river bed in the upper and lower reaches of the sluice may undergo changes in erosion and silt, which will cause the water level in the upper and lower reaches to fluctuate, which will adversely affect the water flow capacity and energy dissipation and anti-scouring facilities. The hydraulic design of large sluices should be verified by hydraulic model tests.

Sluice impervious drainage

The anti-seepage drainage design is based on the maximum water level difference between the upper and lower reaches of the sluice and the foundation conditions, and with reference to the practical experience of the project, the underground contour line (that is, the upper impervious boundary of the seepage area composed of the impervious facilities and the impervious floor) is determined. The average slope of the seepage flow and the slope of the outflow of the underground contour line are within the allowable range, and the calculation of infiltration water pressure and impermeability stability is performed. An anti-filtration layer and drainage trench (or decompression well) should be laid on the seepage and escape surface to drain the seepage water downstream as soon as possible. The anti-seepage drainage design on both sides is basically the same as that of the sluice foundation.

Sluice structure

Structural design According to the application requirements and geological conditions, the gate chamber structure and gate form are selected, and the superstructure of the gate chamber is properly arranged. Analyze the load acting on the sluice and its combination, and calculate the anti-sliding stability of the sluice chamber and the wing wall, the foundation stress and subsidence calculation. If necessary, the foundation treatment scheme should be determined by considering the geological conditions and structural characteristics. For each building (including the gate) that composes the sluice, the structural calculation is performed according to its working characteristics.