Municipal Engineering Practice 1: Summary of Water Supply Engineering Design in Daofu County
[ Summary]
The project is located in the high-cold, earthquake, and ethnic minority areas. It has been tested by earthquakes and low temperatures, and the water intake conditions have changed. The design and operation of the project are summarized.
[ text ]
Daofu County is located in the eastern margin of the Qinghai-Tibet Plateau. It belongs to the Ganzi Tibetan Autonomous Prefecture of Sichuan Province. The National Highway 317 passes through the county. The geographic coordinates of the county are 30°59′ north latitude and 101°07′ east longitude. The altitude is 2 957m, and the annual temperature is 7.8°C. 31 ° C, the lowest -21.9 ° C; the average precipitation is 567.2 mm, the average humidity is 61%, the maximum snow depth is 9 cm, the freezing depth is 50 cm, and the number of sunshine is 2 318.5 h. The county seat is located in the Xianshuihe fault zone and is a region with many earthquakes. The seismic intensity is 8 degrees. ?
1 Engineering design
The county is a county-level ethnic minority settlement, with a focus on agriculture and animal husbandry. With the development of agriculture, animal husbandry and forestry, and the improvement of people's living standards, urban water supply has become an urgent need. The Southwest Design and Research Institute of China Municipal Engineering was commissioned to send a design team to the site for engineering design in October 1977.
?? The design scale of the project? Q? = 1000m3 / d, the effluent water quality requirements meet the national drinking water standards. Water source selection: Daofugou on the left side of the county, the flow rate is 0.2~0.4m3/s. Urban residents and livestock drink this water for many years. Due to the development of agriculture and animal husbandry, most of them are farmland irrigation. When the flash floods occur, there are many muds and sands; The water river flows through the county town, and its water volume is abundant. The maximum flow rate is 882m3/s, the minimum flow rate is 22.8m3/s, and the maximum sand content is 2.48kg/m3. The river has many river forks in the county section, and the floodplain is wide and wide. The project is complicated and the processing cost is too high; the county water transport department, the forestry bureau and other units are digging wells and water at Xianshuihe Beach. The project cost is not much, and the water quality is still good, especially the well water in the water transport station, and the water output and water quality are good. After many investigations and studies, the program was selected to determine the construction of large wells on the Xianshuihe Beach. The wells were located near the water transportation station. The process flow is: Dakoujing→First-class pumping station→High-level pool→Urban pipe network.
?? The engineering design uses a large-scale well-built well to build a high-level pool on the hillside behind the county. The large well has a diameter of 6.0m and a depth of 7.5m. The reinforced concrete structure is considered to be frozen and covered with soil of 300mm. The first-stage pumping station adopts semi-underground type, diameter 6.0m, underground 4.8m, reinforced concrete structure, ground height 3.8m, mixed structure, installation of 2 sets of 4BA? 6 type pumps, 1 used 1 preparation, ?Q=65～135m3/h ,?H?=98~72.5m. The first floor of the first floor of the complex has a construction area of 216 m2, a mixed structure, a large intervening disinfection room at the bottom, a bleaching powder, and the rest of the room for laboratory and office use. There are reserved development areas for water treatment tanks and secondary pump rooms in the waterworks. High level pool? V?=200m3, reinforced concrete structure, covering soil 700mm. The water distribution network of the county town adopts the general pressure cast iron pipe, which is arranged in a dendritic shape, DN=100～150,?L=2.78km, the pipeline buried depth is 1.0m, the asphalt oil is drenched and the exposed pipe is used for antifreeze treatment. The design requires pumping test and water quality analysis during the construction of the large well to determine the water output and whether it is further processed. The building design is fortified at a seismic intensity of 8 degrees. Project budget: 246,800 yuan. ?
2 Project operation?
? 2.1 In the early stage of construction, it is running normally.
The project was completed in September 1978 and was successfully watered. The Dakou well was constructed according to the design of the well location. It was constructed by the sinking method. After excavation, the underground aquifer was found to be sand cobblestone. The diameter of the cobble was not more than 30cm, and the water permeability was good. After the completion, the water output reached the design scale, the water level dropped within 2m, and the water quality was good, which fully met the design requirements. ?
?2.2 subject to earthquake test
On January 24, 1981, a strong earthquake occurred 2.5 km from the county seat. The magnitude was 6.9 and the intensity was 8 degrees. The earthquake caused heavy losses to the county. According to the survey, there were 423 deaths and injuries in the county, including 123 deaths. The building destroyed 205 buildings, 38 buildings were seriously damaged, 36 buildings were light, and 23 buildings were basically intact. The old houses in the county are basically collapsed or destroyed, and new houses with seismic fortifications have been taken, which are basically intact or slightly damaged. The water supply project designed by our institute has also withstood the test. According to the return visit, the large wells, high water pools, water pumping houses and comprehensive buildings in the project were not damaged; there were 4 breaks in the 2.78km long water distribution network, including 1 DN?150 pipeline, DN At the pipeline 2 of =100, the original water pipe of DN=200 occurs in the section where the ground is scattered and cracked due to the earthquake, and the valve well and the fire hydrant well are not damaged. Due to the fracture of the original water pipe, the depth of the buried water is deeper, and it takes more time to dig up and repair. After repairing the earthquake, the factory will use the self-provided diesel engine to generate electricity to restore the water supply one week later. One month later, the power station will resume power transmission, and the water plant will supply water completely, satisfying the possession. The needs of the people of the Han nationality and the need for earthquake relief. ?
?2.3 The levee is built upstream of the water intake point, and the water output of the large well is reduced.
?? The river bank of Xianshuihe County is broadly developed. In the mid-1980s, in order to make use of the river bank for land reclamation, the county built a large embankment at about 2000 m? upstream of the water intake of the Dakou Well. The river embankment moved southward, causing the mainstream of the Xianshui River to be offset to the opposite side by about 1500 m. With the displacement of the mainstream, the dike is built in the embankment. The large well that was originally located on the river bank is now surrounded by newly built land. The water intake conditions of the large well have changed, and the water output has gradually decreased, so that the pump can only work for 3 hours. The water level has dropped to the bottom of the well, it is unable to work continuously, and the water quality has dropped. According to the people, the increase in boiling water scale indicates that the hardness of the water is increasing. At present, the county has opened up a new source of water, and large wells take water as a backup source. ?
3 points of experience
?? The project design uses shallow groundwater to build a large well in Xianshuihe Beach, and through the high-position pool gravity water distribution, the operation practice shows that it is successful. In areas where the economy and culture are relatively backward, it is advisable to adopt a safe and reliable process with simple management and adapt to local conditions.
The county is located in an alpine region with a large temperature difference. The engineering design covers the soil insulation of the structure. The buried depth of the pipeline is 0.5m below the freezing line. The exposed pipelines such as bridge tubes and pool risers are taken to take necessary antifreeze measures. No cracking, freezing or the like occurred. In the construction of high-cold areas, we should pay attention to the local freezing situation investigation and take corresponding engineering anti-freezing measures to ensure the safety of water supply.
China is a country with many earthquakes. There are three fault zones in the west of Sichuan Province: Anning River, Xianshui River and Longmen Mountain. Earthquakes often occur. In only 18 counties of Ganzi Tibetan Autonomous Prefecture, there are 7 counties with earthquake intensity above 8 degrees. There are 8 counties in 7 degrees. In the engineering design, the damage caused by the earthquake should be fully taken into account, and the seismic fortification must be carried out according to the national seismic intensity map. The project also shows that as long as the engineering measures are right, the county's water supply project is subjected to a strong earthquake with an intensity of 8 degrees, and the damage is minimal, and the unprotected houses in the same city are almost completely destroyed, and there is no fortification. In addition, engineering practice has also shown that earthquakes are less destructive to underground structures.
After the project was operated for several years, the county repaired the embankment in the upper reaches and made the embankment to make the water intake conditions change, which caused the large well to fail to operate normally. It was almost scrapped. It was caused by lack of experience in the local area. The lesson is worth summarizing. The construction of hydraulic structures in the rivers near the water intake must be prudent.
?? This project is not large, but it is located in ethnic minorities and high-cold areas. It is subject to changes in earthquake and water intake conditions. Therefore, it summarizes the design and operation of the project, so that you should be criticized and correct.
This article was supported by the senior engineer of Professor Qi Qizao, the Southwestern Design and Research Institute of China Municipal Engineering, and the support of Director Zeng Guangfu of the Daofu County Construction Land Bureau of Ganzi Prefecture. I would like to thank you.
The project is located in the high-cold, earthquake, and ethnic minority areas. It has been tested by earthquakes and low temperatures, and the water intake conditions have changed. The design and operation of the project are summarized.
[ text ]
Daofu County is located in the eastern margin of the Qinghai-Tibet Plateau. It belongs to the Ganzi Tibetan Autonomous Prefecture of Sichuan Province. The National Highway 317 passes through the county. The geographic coordinates of the county are 30°59′ north latitude and 101°07′ east longitude. The altitude is 2 957m, and the annual temperature is 7.8°C. 31 ° C, the lowest -21.9 ° C; the average precipitation is 567.2 mm, the average humidity is 61%, the maximum snow depth is 9 cm, the freezing depth is 50 cm, and the number of sunshine is 2 318.5 h. The county seat is located in the Xianshuihe fault zone and is a region with many earthquakes. The seismic intensity is 8 degrees. ?
1 Engineering design
The county is a county-level ethnic minority settlement, with a focus on agriculture and animal husbandry. With the development of agriculture, animal husbandry and forestry, and the improvement of people's living standards, urban water supply has become an urgent need. The Southwest Design and Research Institute of China Municipal Engineering was commissioned to send a design team to the site for engineering design in October 1977.
?? The design scale of the project? Q? = 1000m3 / d, the effluent water quality requirements meet the national drinking water standards. Water source selection: Daofugou on the left side of the county, the flow rate is 0.2~0.4m3/s. Urban residents and livestock drink this water for many years. Due to the development of agriculture and animal husbandry, most of them are farmland irrigation. When the flash floods occur, there are many muds and sands; The water river flows through the county town, and its water volume is abundant. The maximum flow rate is 882m3/s, the minimum flow rate is 22.8m3/s, and the maximum sand content is 2.48kg/m3. The river has many river forks in the county section, and the floodplain is wide and wide. The project is complicated and the processing cost is too high; the county water transport department, the forestry bureau and other units are digging wells and water at Xianshuihe Beach. The project cost is not much, and the water quality is still good, especially the well water in the water transport station, and the water output and water quality are good. After many investigations and studies, the program was selected to determine the construction of large wells on the Xianshuihe Beach. The wells were located near the water transportation station. The process flow is: Dakoujing→First-class pumping station→High-level pool→Urban pipe network.
?? The engineering design uses a large-scale well-built well to build a high-level pool on the hillside behind the county. The large well has a diameter of 6.0m and a depth of 7.5m. The reinforced concrete structure is considered to be frozen and covered with soil of 300mm. The first-stage pumping station adopts semi-underground type, diameter 6.0m, underground 4.8m, reinforced concrete structure, ground height 3.8m, mixed structure, installation of 2 sets of 4BA? 6 type pumps, 1 used 1 preparation, ?Q=65～135m3/h ,?H?=98~72.5m. The first floor of the first floor of the complex has a construction area of 216 m2, a mixed structure, a large intervening disinfection room at the bottom, a bleaching powder, and the rest of the room for laboratory and office use. There are reserved development areas for water treatment tanks and secondary pump rooms in the waterworks. High level pool? V?=200m3, reinforced concrete structure, covering soil 700mm. The water distribution network of the county town adopts the general pressure cast iron pipe, which is arranged in a dendritic shape, DN=100～150,?L=2.78km, the pipeline buried depth is 1.0m, the asphalt oil is drenched and the exposed pipe is used for antifreeze treatment. The design requires pumping test and water quality analysis during the construction of the large well to determine the water output and whether it is further processed. The building design is fortified at a seismic intensity of 8 degrees. Project budget: 246,800 yuan. ?
2 Project operation?
? 2.1 In the early stage of construction, it is running normally.
The project was completed in September 1978 and was successfully watered. The Dakou well was constructed according to the design of the well location. It was constructed by the sinking method. After excavation, the underground aquifer was found to be sand cobblestone. The diameter of the cobble was not more than 30cm, and the water permeability was good. After the completion, the water output reached the design scale, the water level dropped within 2m, and the water quality was good, which fully met the design requirements. ?
?2.2 subject to earthquake test
On January 24, 1981, a strong earthquake occurred 2.5 km from the county seat. The magnitude was 6.9 and the intensity was 8 degrees. The earthquake caused heavy losses to the county. According to the survey, there were 423 deaths and injuries in the county, including 123 deaths. The building destroyed 205 buildings, 38 buildings were seriously damaged, 36 buildings were light, and 23 buildings were basically intact. The old houses in the county are basically collapsed or destroyed, and new houses with seismic fortifications have been taken, which are basically intact or slightly damaged. The water supply project designed by our institute has also withstood the test. According to the return visit, the large wells, high water pools, water pumping houses and comprehensive buildings in the project were not damaged; there were 4 breaks in the 2.78km long water distribution network, including 1 DN?150 pipeline, DN At the pipeline 2 of =100, the original water pipe of DN=200 occurs in the section where the ground is scattered and cracked due to the earthquake, and the valve well and the fire hydrant well are not damaged. Due to the fracture of the original water pipe, the depth of the buried water is deeper, and it takes more time to dig up and repair. After repairing the earthquake, the factory will use the self-provided diesel engine to generate electricity to restore the water supply one week later. One month later, the power station will resume power transmission, and the water plant will supply water completely, satisfying the possession. The needs of the people of the Han nationality and the need for earthquake relief. ?
?2.3 The levee is built upstream of the water intake point, and the water output of the large well is reduced.
?? The river bank of Xianshuihe County is broadly developed. In the mid-1980s, in order to make use of the river bank for land reclamation, the county built a large embankment at about 2000 m? upstream of the water intake of the Dakou Well. The river embankment moved southward, causing the mainstream of the Xianshui River to be offset to the opposite side by about 1500 m. With the displacement of the mainstream, the dike is built in the embankment. The large well that was originally located on the river bank is now surrounded by newly built land. The water intake conditions of the large well have changed, and the water output has gradually decreased, so that the pump can only work for 3 hours. The water level has dropped to the bottom of the well, it is unable to work continuously, and the water quality has dropped. According to the people, the increase in boiling water scale indicates that the hardness of the water is increasing. At present, the county has opened up a new source of water, and large wells take water as a backup source. ?
3 points of experience
?? The project design uses shallow groundwater to build a large well in Xianshuihe Beach, and through the high-position pool gravity water distribution, the operation practice shows that it is successful. In areas where the economy and culture are relatively backward, it is advisable to adopt a safe and reliable process with simple management and adapt to local conditions.
The county is located in an alpine region with a large temperature difference. The engineering design covers the soil insulation of the structure. The buried depth of the pipeline is 0.5m below the freezing line. The exposed pipelines such as bridge tubes and pool risers are taken to take necessary antifreeze measures. No cracking, freezing or the like occurred. In the construction of high-cold areas, we should pay attention to the local freezing situation investigation and take corresponding engineering anti-freezing measures to ensure the safety of water supply.
China is a country with many earthquakes. There are three fault zones in the west of Sichuan Province: Anning River, Xianshui River and Longmen Mountain. Earthquakes often occur. In only 18 counties of Ganzi Tibetan Autonomous Prefecture, there are 7 counties with earthquake intensity above 8 degrees. There are 8 counties in 7 degrees. In the engineering design, the damage caused by the earthquake should be fully taken into account, and the seismic fortification must be carried out according to the national seismic intensity map. The project also shows that as long as the engineering measures are right, the county's water supply project is subjected to a strong earthquake with an intensity of 8 degrees, and the damage is minimal, and the unprotected houses in the same city are almost completely destroyed, and there is no fortification. In addition, engineering practice has also shown that earthquakes are less destructive to underground structures.
After the project was operated for several years, the county repaired the embankment in the upper reaches and made the embankment to make the water intake conditions change, which caused the large well to fail to operate normally. It was almost scrapped. It was caused by lack of experience in the local area. The lesson is worth summarizing. The construction of hydraulic structures in the rivers near the water intake must be prudent.
?? This project is not large, but it is located in ethnic minorities and high-cold areas. It is subject to changes in earthquake and water intake conditions. Therefore, it summarizes the design and operation of the project, so that you should be criticized and correct.
This article was supported by the senior engineer of Professor Qi Qizao, the Southwestern Design and Research Institute of China Municipal Engineering, and the support of Director Zeng Guangfu of the Daofu County Construction Land Bureau of Ganzi Prefecture. I would like to thank you.
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