What Are the Most Common Drainage Issues?

Drainage system (sewerage system) refers to the collection of drainage collection, transportation, water quality treatment and drainage facilities in a certain way. The general name of drainage ditch (pipe) at all levels and buildings used for waterlogging, stain prevention and salt prevention. It is mainly composed of field drainage regulation network, drainage ditch at all levels, waterlogged lakes, drainage sluices, pumping stations and drainage drainage areas (see photo). The excess water in the drainage area is first collected into the field drainage regulation network, and then drained to the drainage area through drainage sluices or drainage stations after being drained by drainage ditch at all levels or after being detained by the lake.

Drainage system (sewerage system) refers to the collection, transportation, treatment and discharge of water quality in a certain way

The layout of the drainage system should be comprehensively planned to try to:

The drainage channel should be at the lowest point of the control area, in order to drain as much as possible.

According to the terrain, the drainage area should be divided into high, medium and low slices, so as to achieve high water and high drainage, low water and low drainage, self-discharge mainly, and drainage as supplement.

There are many types of drainage methods for urban viaduct bridge decks at home and abroad. By summarizing and summarizing the drainage systems of different viaduct bridge decks, the drainage systems of viaduct bridge decks can be divided into the following three categories based on the different interception methods of the drainage system inlets: The method of draining the water directly into the drain pipe, the method of draining the water into the drain pipe and the downpipe along the bridge pier, the way of drainage of the anti-collision railing and the drainage groove.

Directly draining the water inlet to the drain pipe

This drainage method is a relatively simple drainage method for the viaduct bridge deck, which is suitable for the case where no vehicle is passing under the bridge. The rainwater on the bridge deck is collected to the rainwater outlet through the horizontal and vertical slope of the bridge deck. The rainwater outlet is connected to the horizontal drainage pipe (in the case of a hollow slab) or the vertical drainage pipe (in the case of a continuous beam) to directly shower the rainwater under the bridge. At present, in domestic and foreign viaduct drainage design codes, there is no clear stipulation on the vertical height of the direct drainage of the bridge deck. The runoff of the bridge deck may contain corrosive contaminants, and direct showering on the bridge members will make it Corrosion or formation of dirt will adversely affect the structure of the viaduct.

Inlet connection of drainage pipe and downspout along the pier

This drainage method is based on the direct drainage of the water inlet and the drain pipe, and a certain number of drainage pipes and downspouts are added. The rainwater on the bridge deck is drained into the drainage ditch or drain under the bridge through the drainage pipe. It is suitable for vehicles passing under the bridge. Case. Some developed countries have clear regulations for the discharge of bridge deck runoff, requiring drainage pipes and drainage pipes to be used to direct the bridge deck water flow to the drainage outlet under the bridge.
In this type of drainage system, the size and spacing of the water inlet will affect the drainage capacity of the drainage system. If the size of the water inlet is small, the gap between the rainwater outlets must be reduced (the minimum distance for the design of the bridge drainage in our country is 5m) to meet the requirements of the bridge drainage. When the distance between the rainwater inlets is small, the rainwater intercepted across the middle rainwater outlet needs A considerable length of vertical drainage pipe can reach the downpipe at the bridge pier. When the vertical drainage pipe is too long and the laying slope is small, the water flow in the pipe cannot reach the self-cleaning flow rate, and the impurities in the water flow are easy to settle in the drainage pipe, causing the pipeline to be blocked Poor drainage. If there are rainwater outlets only at the bridge pier, the distance between the rainwater outlets on the bridge deck becomes larger, the length of the longitudinal drainage pipe is shorter and the laying slope is larger, and the water flow velocity in the pipe is larger, which meets the requirements of self-purification of the water flow. The size must also increase at the same time, the width is generally taken to be about 40cm.

Drainage method of anti-collision railing plus drainage groove

In the case of vehicles passing under the bridge, in order to ensure the maintenance of the drainage system and the convenience of clearing, a drainage groove is often cast outside the crash wall of the viaduct. The rainwater outlet on the bridge is connected to the lateral drainage pipe to drain the water from the bridge to the drainage trough. The water flows through the drainage trough through the lateral drainage pipe and the downfall pipe, and is discharged along the pier to the drainage ditch or drainage outlet under the viaduct. The advantage of this method is that even if a blocking phenomenon occurs, it can be found and maintained in time, but the anti-collision railing and the drainage groove have a certain impact on the appearance of the bridge.

In the design of the rainwater drainage system of the viaduct bridge deck, the value of the transverse and longitudinal slopes of the bridge deck is an important factor affecting the drainage flow velocity and flow of the bridge deck. China's highway drainage design code '"stipulates that the viaduct bridge deck should have no more than 2% The drainage slope is less than 0.5%. In the actual design of the drainage system of the viaduct, the small slope of the bridge deck will result in a small water velocity on the bridge deck and a small catchment flow per unit time, which will seriously affect the drainage efficiency of the bridge deck drainage system and cause the bridge area. Water; the design of the slope of the bridge deck is too large, the catchment flow of the bridge deck is larger in a unit time, and the bridge deck's catchment flow exceeds the discharge of the rainwater outlet will also cause bridge area water, and the excessively large slope of the deck is not conducive to driving safety Therefore, the value of the slope of the viaduct bridge deck should take into consideration the problems of the discharge flow and the bridge area water, and provide the maximum discharge service for the drainage system on the premise of meeting the requirements of traffic safety and specifications.
In addition to the value of the slope of the bridge deck, the design of the gully outlet parameters is also a factor that affects the drainage flow of the bridge deck. The design parameters of the gully outlet mainly include the size, location and spacing of the gully outlet. According to the design specifications of highway drainage design, the bridge deck drainage generally adopts a rectangular rainwater outlet with a width of 200-300mm and a length of 300 ~ 400mm, with a grille cover at the top; the location of the rainwater outlet should be located at the edge of the bridge deck driveway, the largest The drainage interval should not exceed 20m. In the design of the gully outlet, the requirements of the bridge deck discharge flow should be met to avoid waste or shortage of the gully outlet. The traditional viaduct drainage system is equipped with rainwater castor on the top of the rainwater outlet. Although it can intercept large volumes of debris, some debris will enter the drainage system through the rainwater castor, deposit in the drainage crosspipe, block the drainage pipe, and reduce drainage. effectiveness. Therefore, in the design of the viaduct drainage system, the anti-blocking problem of the drainage system should be fully considered. In addition to the use of rainwater castors, other facilities for preventing debris in the rainwater outlet should be added.
Poor drainage of the viaduct bridge deck In addition to the bridge deck slope and the installation of the gully, there are also problems such as aeration caused by swirling flow in the gully, clogging of the gully, and sedimentation of the drainage pipe. To improve the external factors of the drainage of the traditional viaduct, to fundamentally solve the problem of water accumulation on the viaduct bridge under the condition of heavy rainfall, the gravity drainage method of the traditional drainage system must be changed in principle. The research status of roof siphon drainage system shows that under the condition of a certain height difference, the introduction of a rainwater bucket device in the drainage system can effectively reduce the amount of aeration in the water flow in the pipe, so that the water flow in the pipe reaches the full flow, thereby generating a siphon effect. Urban viaducts have certain advantages in terms of their own height, which can meet the required height difference for siphon effect. To make the drainage system have siphon effect, the key is to remove the air in the water flow to achieve full flow. Therefore, when designing the drainage system of the viaduct, a certain rainwater bucket device should be installed at the rainwater outlet to separate the water and gas in the water flow to achieve the purpose of anti-swirl. This is the key to the siphon effect of the viaduct drainage system. ^[1]