Research On The Structural Design And Model Experiment Of The U-Shaped Aqueduct Body Made By Ultra-High Performance Concrete

According to the national agricultural water saving program(2012-2020),the annual water shortage in China has reached more than 50 billion cubic meters,and more than half of the cities have different degrees of water shortage.At the same time,China’s water diversion project is insufficient,and the scale of water diversion project across the first level water resources area is less than 1/3 of the available water,which has caused great trouble to the urban domestic water and food production safety.In 2021,No.1 central document pointed out that the development and reconstruction of large and medium-sized irrigation districts should be implemented in the development of water conservancy projects in China.It can be seen that the construction of water diversion and irrigation project in China is urgent.Aqueduct is an overhead water conveyance structure across rivers,roads,valleys and other terrain.It is the most widely used cross structure in the irrigation area.It is widely used in water diversion and irrigation projects and plays an important role in optimizing the allocation of water resources.The U-shaped aqueduct is widely used.But at present,the ordinary concrete U-shaped aqueduct body has the following problems:(1)The low strength of concrete and the self weight of prefabricated aqueduct body lead to the difficulty of transportation and hoisting installation.(2)The durability of aqueduct body is poor and the service life of aqueduct is short.Ultra-high performance concrete(UHPC),as a new type of concrete material,has excellent mechanical properties and durability.It is suitable for the preparation of lightweight and high durability components.It has been applied in many engineering fields such as bridges.However,there is no report on the preparation of aqueduct body with UHPC at home and abroad.Based on the existing research results of UHPC and ordinary concrete U-shaped aqueduct,the structural design and model test of UHPC-U-shaped aqueduct are carried out in this paper:(1)Through the preliminary analysis of the working conditions of aqueduct body,the strength grade of UHPC is RPC100.Furthermore,the effects of different aggregate types,sand binder ratio,fiber types and content on UHPC performance were studied.The optimal aggregate type was zone III air dried river sand with particle size less than 2.36 mm,sand binder ratio was 1.2,and volume content of copper plated steel fiber was 1.5%.(2)Based on the design method of ordinary concrete U-shaped aqueduct,the structural design concept of UHPC-U-shaped aqueduct body is proposed.The size and reinforcement of U-shaped aqueduct body are determined by calculating the bearing capacity limit state and checking the serviceability limit state of the transverse structure and longitudinal structure of the aqueduct body.Thanks to the high compressive strength and tensile strength of UHPC,the wall thickness and reinforcement amount of UHPC-U-shaped aqueduct body can be greatly reduced,and the self weight of aqueduct body can be reduced.Through the case study of Ushaped aqueduct project in Hongling Irrigation District of Hainan Province,the self weight of UHPC-U-shaped aqueduct is only 36.4% of that of ordinary concrete U-shaped aqueduct.(3)Based on the above design method,a U-shaped aqueduct body model with span of 4.2m,width of 560 mm,wall thickness of 40 mm,inner radius of 190 mm and span width ratio of 7.5 was designed and prepared.The bearing capacity and deformation of the aqueduct body were studied by water,wet sand and barite sand loading tests.The test results show that the full load of UHPC-U-shaped aqueduct body is within the range of bearing capacity,the peak tensile stress is less than the ultimate tensile strength of UHPC,the vertical displacement and transverse displacement are smaller,and the deflection is far less than the limit value of code and the deflection calculation value,which meets the design and use requirements.(4)Taking the U-shaped Aqueduct project in Hongling irrigation area of Hainan Province as an example,the economic,environmental and social benefits of UHPC-U-shaped aqueduct are analyzed.The results show that,compared with ordinary concrete U-shaped aqueduct,the new construction cost of UHPC-Ushaped aqueduct is 36.3% higher,but the life cycle cost is reduced by 35.0%;the carbon emission of new construction of the UHPC-U-shaped aqueduct can be reduced by 36.1%,and the carbon emission of life cycle of the UHPC-U-shaped aqueduct can be reduced by 68.1%.Due to the long service life of UHPC-U-shaped aqueduct,it can ensure the water safety of urban life,industrial production and agricultural irrigation,and effectively reduce the waste concrete due to the demolition and replacement of aqueduct.UHPC-U-shaped aqueduct body has good economic,environmental and social benefits,which is the upgrading product of ordinary concrete aqueduct body.