Summary of the construction technology of the hott

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Summary of static pressure pile construction technology

static pressure method construction is a pile sinking technology that uses the static pile driver to press the prefabricated pile into the soil with the dead weight of the pile driver and the counterweight on the pile frame. As early as the 1950s, this kind of innovation combined the strength of continuously reinforced thermoplastic composites and the design flexibility and reliability of Vickers Victrex peek injection polymer. At the beginning, the static pile pressing method was adopted in coastal areas of China. By the 1980s, with the development of pile pressing machinery and the enhancement of environmental protection awareness, it was further promoted. By the 1990s, the pile driver had achieved serialization, and the pile driver with the maximum pile driving force of 6800kn had come out. It can press both precast square piles and prestressed pipe piles. The applicable buildings are not only multi-storey and medium high-rise buildings, but also high-rise buildings and large structures with 20 floors and above. At present, it is applied in Hubei, Guangdong, Shanghai, Jiangsu, Zhejiang, Fujian and other provinces and cities in China, especially in Shanghai, Nanjing, Guangzhou and the Pearl River Delta

2 pile sinking mechanism of static pressure method

static pressure precast piles are mainly used in soft soil foundation. In the process of pile sinking, the pile tip directly causes punching failure of soil, accompanied by or first occurs direct shear failure of soil along the pile body. The pore water is compressed by this punching and shearing action to form uneven water head, generate excess pore water pressure, disturb the soil structure, reduce the shear strength of a part of the soil around the pile about one time the pile diameter, seriously soften (cohesive soil) or thicken (silt, sandy soil), and appear the phenomenon of soil remodeling, so that the static pressure pile can be easily and continuously sent into the deep foundation soil layer. If there is a pause in the process of pile pressing, part of the pore water pressure will disappear, and the soil around the pile will undergo radial consolidation, so as to ensure their survival and health. The compactness of the soil mass will increase, and the side wall friction around the pile will also increase, especially the strength of the disturbed and remolded pile end soil will be restored, resulting in a large increase in pile end resistance. The longer the pause time is, the more the disturbed soil strength will recover and increase. Therefore, static pressure pile sinking should not stop halfway. When it is necessary to stop by pile extension, shallow pile extension should be considered, and stopping at the depth of good soil layer should be avoided as far as possible. Static pressure pile is a soil compaction pile, and the density of soil around the pile will increase during the pressing process. Its soil compaction effect depends on the geometry of pile section, pile spacing and the performance of soil layer

3 scope of application of static pressure method

static pressure method is usually applicable to high-pressure compressible clay layer or soft clay layer with light sandy nature. When the pile must pass through the sandy soil interlayer with a certain thickness, the storage, printing and final pressure must be completed according to the pile pressing force of the pile machine, as well as the shape, thickness, density, mechanical index of upper and lower soil layers, pile type, and the structure, strength The applicability of pile section specification and pile layout form, the height of groundwater level, and the pressure stabilization time and times before final pressure stabilization are comprehensively considered

pile pressing machine with pile pressing force greater than 4000kn can pass through 5~6m thick medium dense and dense sand layer. The capacity of medium-sized pile pressing machine (pile pressing force ≤ 2400kn) to cross the sand layer is limited, so the feasibility of pile pressing needs to be judged

static pressure piles are also suitable for karst areas with not thick overburden. It is difficult to drill with bored piles in these areas; Punching pile is adopted, which is easy to clamp the hammer; Driven piles are used, which are easy to break. Only static pressure piles can be pressed in slowly and show the pressure resistance. However, static pressure piles should be used with caution in karst areas where karst caves and gullies are fully developed, and in areas where there are many boulders and obstacles in the soil layer

small pile pressing machine (pile pressing force ≤ 600kN) is used to press prefabricated small piles. It is suitable for bearing layers (such as hard plastic silty clay layer, silty soil layer and medium dense silty fine sand layer) within 10m

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