In the past ten years of application process in China, there are many engineering quality problems, in order to ensure the quality of the project when using FRP sand pipe, should be safe, reliable and reasonable, economic engineering structure design on the basis of pipe paving design, production, to ensure the quality of the pipe. At the same time, according to the engineering structure design requirements and construction regulations, the installation and construction are organized to meet the control requirements, which can ensure the success of the FRP sand pipe project.
1 Main problems
FRP sand pipe projects need to carry out strict engineering structural design, in the early stage of domestic use, because there is no domestic structural design specifications, and according to foreign specifications and the lack of long-term performance data of the pipe, therefore, some projects have not passed the engineering structural design, in addition, for economic considerations, The safety factor of the initial circumferential tensile strength of the pipe is low (executed by 4 times), and due to the influence of raw materials and production technology for the production of FRP sand pipe, the long-term performance test results completed by some domestic enterprises are slightly lower than the test results of foreign products. In addition, excessive vertical deformation often occurs in construction. It causes the pipeline to be damaged by excessive external pressure load in the working stage, resulting in engineering quality problems. Therefore, there are two major problems in the design of engineering structure, that is, safe and reasonable initial circumferential tensile safety factor and reasonable backfill material and vertical deformation control requirements.
In terms of pipes, there are mainly raw material selection problems, glass fiber dosage problems and production technology problems. Some production enterprises use low performance of cheap resin, high alkali glass fiber to produce FRP sand pipe, and the production process can not guarantee the density of the resin mortar layer, such FRP sand pipe performance far from the product standard requirements, but in a number of projects found such pipes.
In terms of construction, often because the construction unit is very accustomed to the construction of concrete pipe, usually do not pay attention to the backfilling degree, which will cause excessive vertical deformation of the pipe and cause pipe damage.
2 Strategies
2.1 Engineering structure design
FRP sand sandwich pipe has been applied in China for more than 10 years, and on the basis of many years of application in China, the "water supply and drainage engineering buried glass fiber reinforced plastic sand pipe pipe structure design Regulations" (CECS190: 2005) is the code that should be followed in the structural design of FRP sand pipe engineering in China. Considering the safe, reliable and reasonable and economical use of FRP sand pipe, it is recommended that the long-term vertical deformation of FRP sand pipe should not exceed 3% during design.
2.2 Pipe Quality
In order to ensure the quality of the pipe, the following aspects should be paid attention to:
1. Raw materials
According to the requirements of product standards, the technical indicators of raw and auxiliary materials used in production should be made corresponding provisions: alkali-free glass fiber should be used; Structure layer resin: tensile strength: 60MPa; Tensile elastic modulus: 3.0GPa; Elongation at break: 2.5%; Thermal deformation temperature: 70℃. Raw material manufacturers should test all raw materials and be qualified before they can be put into use, and important raw materials such as glass fiber and resin should be inspected by a third party before they can be used.
2. Production monitoring
For the production process of pipes, it is appropriate to ask a professional unit to supervise the production to ensure that the main raw materials are used in sufficient quantities.
3. Product acceptance
Products have to pass strict inspection before they go out. In addition to the non-damage inspection of each pipe, each batch of pipes (generally 100 pipes for a batch) should be randomly selected for destructive inspection to ensure the quality of the pipe.
In fact, when determining the pipe production enterprises, enterprises with larger production scale, more application performance, strong technical force and good capital situation should be selected to undertake the pipe production business.
2.3 Construction
In the construction of FRP sand pipe, suitable backfill materials should be selected according to the design requirements, and the backfill compactness should be strictly controlled. As long as the requirements of compactness are met, the vertical deformation of the pipeline can be controlled, and the tensile stress level of the pipe wall can be controlled, so that the tensile stress level of the pipe wall after the action of internal water pressure will not be too high, and the safe operation can be achieved. In addition, the selection of sealing rubber ring materials, interface connection design, and building connection to prevent uneven settlement should also be carefully handled.
2.4 Project management
In fact, to succeed in any project, the organization and management of the project construction unit is the fundamental guarantee. The design of the engineering structure should be reliable and reasonable, and if the selected design unit lacks experience in FRP sand pipe engineering, the relevant professional units should be consulted. The production process of the pipe should also be strengthened to ensure that the raw materials used and the production process meet the requirements, and professional units can be hired to supervise the production. The construction stage can first carry out the test section or the advance section construction, and meet the requirements of the design and construction regulations, and make the relevant personnel have a corresponding understanding of the characteristics of the FRP sand pipe, and then carry out large-scale construction. In each implementation stage, once the problem may affect the quality of the project, the construction management unit should be corrected with a clear attitude, only in this way can the quality of the project be guaranteed.