Study on drainage design of subway station.

In recent years, with the acceleration of urbanization and the sharp increase of urban population, the ground transportation in major cities in China is facing tremendous pressure. Urban rail transit has become an important means to effectively alleviate the flow of people on the ground and alleviate traffic congestion. At present, it has been built and put into operation in many cities in China, and most of them are mainly subways. Below, Zhong Da Consulting briefly introduces the types and methods of subway station drainage, focusing on the layout of drainage floor drain, as well as the design and control methods of subway station wastewater pumping station and sewage pumping station, for designers' reference.

The drainage design of subway station is one of the main contents of station water supply and drainage and disaster prevention design. It is of great significance to discharge the accumulated water in the station in time for the normal operation of vehicles and the protection of various electrical equipment. The drainage system of subway station adopts split-flow system, which is mainly composed of wastewater system, sewage system and rainwater system, in which the wastewater system includes station washing water, fire fighting wastewater and structural leakage. Sewage is mainly domestic sewage; Rainwater mainly comes from open entrances and exits and wind pavilions.

2 subway station sewage system design

The process of wastewater collection and discharge in the station is: all kinds of wastewater → drainage floor drain → track drain → main wastewater pumping station → pressure inspection well → municipal sewage system.

2. 1 Design and calculation standards for various wastewater quantities

The flushing water discharge of the station is 4Lm/2 times, and the calculated area is the public area of the platform floor of the station hall, once a day, and each time is calculated as 1h; The usual design standard of structural leakage is 1Lm/2 days, and the calculated area is the surface area in the station; Fire fighting wastewater is calculated as 100% of primary fire fighting water.

2.2 Layout of Drainage Floor Drain

All kinds of wastewater in the station are collected by floor drains located in the platform floor, the station hall floor and the rooms with water points, and discharged into the open drains on both sides of the track through drainage risers. The floor drain of the station hall floor is located in the shallow drainage ditch inside the main body of the station, with an interval of about 40 m. In addition, the station entrance and exit should be equipped with intercepting ditch and drainage floor drain. Floor drains should also be installed in rooms with water supply points such as environmental control room, clean room, sewage pump room, wastewater pump room and tea room. The floor drain on the platform floor mainly discharges washing wastewater in public areas, which is more than 2.5m away from the edge of the platform. The Code for Design of Subway has no clear stipulation on the floor drain setting of various air ducts entering the main station. In the author's opinion, in order to avoid the mutual interference caused by the connection of different types of air ducts with shallow drains, a drainage floor drain should be set at the entrance of each air duct, and different air ducts cannot use the drainage floor drain.

2.3 Design of Main Wastewater Pumping Station

The main wastewater pumping station mainly discharges structural leakage, condensed water, production, flushing and fire fighting wastewater. , should be located at the lowest point of the station or line. The key of its design is to determine the volume of waste water pool and the parameters of waste water pump. There should be two main waste water pumps in the station, which are standby for each other at ordinary times and work at the same time during fire fighting or when necessary. The flow rate of the drainage pump is determined according to the sum of the displacement during fire fighting and the water seepage of the structure. The effective volume of the main wastewater pool is determined according to the water output of the main wastewater pump for 20min, and it is not less than 30m3.

For the case that some subway stations are jointly built with underground commercial buildings, the author thinks that in order to avoid the influence of commercial building fire on subway stations, water retaining and intercepting measures should be set between them, and an independent local sewage pumping station should be set up inside the commercial part.

3. Design of station sewage pumping station

The sewage in the subway station mainly comes from the daily water used by the station staff. Generally, there is a bathroom in the equipment area of the station hall floor for staff to use. Domestic water consumption is calculated according to 50L shifts/person, and the displacement is considered as 95% of domestic water consumption.

The sewage pumping station should be located in the platform floor equipment area below the toilet. The effective volume of sewage collection tank is generally determined according to the sewage volume of 6h, but the effective volume should not be less than 2m3. The flow rate of sewage pump is selected according to the designed flow rate of toilet drainage. In actual design, the plane of the sewage tank should not be too large to avoid the sewage staying in the sewage tank for too long. At the same time, the sewage pool should be provided with an exhaust pipe, which is directly connected with the exhaust pipe in the station. See Figure 3 for the layout profile of sewage pumping station.

Design of 4-station rainwater pumping station

The rainwater pumping station is mainly set in the outdoor wind pavilion of the station and under the escalator of the outdoor entrance and exit, and the rainwater discharge is calculated according to the collection time of the design rainstorm return period of 50 years 10min. The flow rate of rain water pump at the entrance and exit is selected according to the sum of fire water volume and rain water volume at the entrance and exit, and the flow rate of rain water pump at Fengting is selected according to the calculated rain water volume. The effective volume of each water collecting basin is determined according to the output of the rain water pump of 10min. For drainage pumping stations with closed entrances and exits, they can be classified as local sewage pumping stations, and the design flow of pumps only considers fire-fighting displacement. There is no need to set up a rainwater pumping station for the wind pavilion with a top cover, and the leakage water of the wind pavilion structure can be discharged into the station along the air duct, collected by the floor drain and discharged into the main wastewater pool.

5 control the water level setting and pump control mode of each pumping station.

The station control room monitors the working state, manual automatic state, fault state and water level state of the drainage pump; Automatically monitor the dangerous water levels in the waste water pool, water collection pool and sewage pool, and give an alarm for the ultra-high; Set automatic operation timing for all drainage pumps, automatically switch between main pump and standby pump according to the set operation time, and provide maintenance report according to the maintenance setting plan. The drainage pump realizes automatic control and manual control of water level through the control box of the pump house. The control box adopts one-control-two mode, in which the water level control mode adopts float switch, and the float switch is set in one-to-one correspondence with the control water level.

The two submersible sewage pumps in the waste water pump house are usually operated in turn, one for use and one for standby. When extinguishing the fire, two pumps work at the same time, and the wastewater pool is equipped with ultra-low water level, pump stop water level and start water level control water level of 65438 # pump +0 and 2 # pump ***4.

Two submersible sewage pumps in the sewage pump house run in turn, and there are three control water levels: pump stop level, pump start level and ultra-high alarm level.

There are two submersible sewage pumps at the bottom of the escalator at the entrance and exit of the station and in the sump at the entrance of the cave, one for use and one for standby at ordinary times. When necessary, run two pumps and set three control water levels, namely 1 and the stop water level and start water level of the second pump.

6 drainage pipe materials and other important protective measures

Generally speaking, plastic-coated or plastic-lined steel pipes can be used for pressure drainage pipes in the station, and flame-retardant UPVC pipes can be used for gravity drainage pipes. Fire rings should be set when the drainage pipe passes through different fire zones; The metal drainage pipes leading to the outside of the subway should be insulated before being led out, and insulating flanges or insulating short pipes can be installed. In addition, the UPVC drainage pipeline cannot directly pass through the windward air duct of the track, and the inner part of the air duct should be protected by steel casing to avoid the damage caused by high smoke during fire fighting.

The above summarizes the key contents of subway drainage design. Because the drainage design of subway stations is different from that of basements of other civil buildings, the reliability and timeliness of drainage are required. By solving the problems encountered in design and construction, designers constantly summarize and improve the design technology of subway drainage to achieve the goal of safety, rationality and economy.

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