Prestressed concrete pipe pile is an important branch of prestressed pipe pile. Prestressed pipe piles are divided into prestressed concrete pipe piles (PC pile), prestressed high-strength concrete pipe piles (PHC pile) and thin-wall pipe piles (PTC pile) according to concrete strength grade and wall thickness.
The concrete strength of PC pile shall not be lower than C50, the strength grade of PTC pile shall not be lower than C60 and the concrete strength grade of PHC pile shall not be lower than C80. Prestressed pipe pile can be divided into post-tensioned prestressed pipe pile and pre-tensioned prestressed pipe pile. Prestressing pipe pile is a kind of hollow cylinder slender concrete precast component made by prestressing technique and centrifugal molding method. It is mainly composed of cylindrical pile body, end plate and steel hoop. According to the outer diameter, the prestressed pipe pile is divided into 300mm, 350mm, 400mm, 450mm, 500mm, 550mm, 600mm, 800mm and 1000mm specifications. Pipe pile is all factory production, commonly used section length 8~12m. Pipe piles can be divided into type A, AB and B according to the bending moment of cracking resistance. The effective prestress is 3.5~4.2MPa for type A, 5.0MPa for type AB and 5.5~6.0MPa for type B. Generally, the pipe pile has an effective prestress of 4~5MPa, and the concrete of the pile body can effectively resist the tensile stress of pile driving. Therefore, for general construction projects, the pipe pile of type A or AB specified by China can meet the requirements. Each pipe pile has factory mark, marked on the surface of the pipe pile about 1.0m away from the end of the place.
2. Scope of Application
The prestressed concrete pipe pile foundation should be used in the site where the pile end bearing layer is thick hard and cohesive soil layer of strongly weathered or fully weathered rock, as well as dense gravel, pebble layer, sand soil and silt soil, and it is more suitable for the fish pond and beach where the water depth is not particularly large. Should not be used in the following venues:
1) The soil layer contains more lonely stones or obstacles that are difficult to remove;
2) The soil layer contains a hard interlayer which is not suitable for the bearing layer and it is difficult for the pipe pile to penetrate;
3) There is no limestone strata suitable for pile end bearing layer on bedrock;
4) “upper soft and lower hard, soft and hard abrupt change” strata.
1) High bearing capacity of single pile. Due to the high concrete strength of PHC pipe pile, it can be driven into the dense sand layer and strongly weathered rock layer. Due to the extrusion effect, the pile end bearing capacity is increased by 70%-80% and the pile side friction resistance is increased by 20%-40% compared with the original soil. Therefore, the design value of bearing capacity of PHC pipe pile is higher than that of immersed pipe cast-in-place pile, bored cast-in-place pile and manual digging pile with the same diameter.
2) Wide application range. PHC pipe pile is the lateral resistance and end resistance jointly bear the upper load, can choose strong weathering rock layer, fully weathered rock layer, hard clay layer or dense sand layer (or pebble layer) and other soil as the bearing layer, and the bearing layer fluctuation changes of geological conditions are strong adaptability, so it can adapt to a wide range of areas, building types. Widely used in a variety of high-rise buildings below 60 floors and industrial and civil buildings low cap pile foundation, railway, highway and bridge, port, wharf, water conservancy, municipal, structures, and large equipment engineering foundation. For photovoltaic projects, fish-light complementarity and farm-light complementarity are more widely used.
3) The quality of driving pile is reliable. PHC pipe pile is factory, professional, standardized production, pile quality is reliable; Convenient transportation and hoisting, fast pile; High degree of mechanized construction, simple operation, easy control; It is easy to guarantee the bearing capacity, bending resistance and pulling resistance.
4) Prestressed concrete foundation needs to add prestressed equipment, production technology requirements are high, construction period is long.
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