Precautions during the construction of nodular graphite pipe fittings

The pipeline foundation shall meet the requirements of allowable settlement and allowable vertical bearing capacity at the same time. If it does not meet the requirements, reinforcement measures shall be taken according to the design requirements. If the geotechnical survey of individual pipeline foundation section is unknown and the design has not taken into account, the construction supervisor shall be informed in time if sludge and loose clay are found after site excavation. The foundation shall be solved by replacing the cushion or driving foundation piles. The pipeline foundation of Jingang Avenue is basically muddy soil, The pipe foundation is stabilized by riprap, mud squeezing, glass fiber geogrid and non-woven geotextile. Glass fiber geogrid is a network structure material made of glass fiber by weaving process. In order to protect the glass fiber and improve the overall performance, it is a geotechnical composite material by coating process. The main components of glass fiber are: silicon oxide, an inorganic material, with stable physical and chemical properties, high strength, high modulus, high and excellent cold resistance, and no long-term creep; Good thermal stability; The mesh structure makes the aggregate locked and restricted; Improve the bearing capacity of asphalt mixture. Due to the modified asphalt coated on the surface, the geogrid has dual composite properties, which greatly improves the shear capacity of the geogrid. Sometimes, it is combined with self-adhesive pressure sensitive adhesive and asphalt impregnation treatment on the surface to make the grid and asphalt pavement closely integrated. Because of the interlocking force between the earth and stone in the geogrid grid, the friction coefficient between them increases significantly (up to 08~10). The uplift resistance of the geogrid embedded in the soil increases significantly due to the strong friction and bite force between the grid and the soil, so it is a good reinforcement material. At the same time, the geogrid is a kind of light weight, flexible plastic plane mesh, which is easy to cut and connect on site, and can also be overlapped. The construction is simple and requires no construction machinery and technicians.

Generally, the vertical bearing capacity of the pipe foundation of the ductile iron pipe fittings meets the design requirements, and no special foundation is required. In order to reduce the pipe stress in some sections, the support surface of the pipe can be excavated into an arc on the construction site to make the pipe body contact with the original foundation as closely as possible.

Sand lime soil foundation can be used, but it should be noted that the sand cushion should be flat and no large local bulges are allowed.

Casing or concrete cushion cap type foundation shall be adopted for road crossing section.