Micropile diameter is generally 150mm ~ 300mm, pile length of not more than 30 meters, arranged in various forms of the vertical pile and network structure of the pile. 30 years by the Italian F.lizzi initiative, the United States in the 1940s began using micropile, the development is very rapid. China started in 1981, 1985 in Shanghai for the first time.
Compared with other methods of foundation reinforcement or foundation underpinning has the following advantages:
- the required construction site is small, the general plane size of 0.6m × 1.8m, clearance height of 2.1 ~ 2.7m to construction;
- the construction of noise and vibration, construction is also more convenient;
- the pressure grouting so that the micropile and soil close combination of soil, pile and wall connected into one;
- the construction of the pile hole diameter is small, so the foundation and foundation soil almost no additional stress, the construction of the original foundation of a small impact; does not interfere with the normal use of the building;
- can penetrate a variety of obstacles, apply to a variety of soil conditions;
- pile and pile between the soil through the mat to form composite foundation.
As the micropile has the above advantages, in recent years with the rise of China’s reinforcement of the transformation, the application of more and more. At present, the micropile is mainly used in the following aspects:
- building layer and transformation;
- foundation uneven settlement of the foundation underpinning;
- shore (foundation pit) and underground cavern earthwork The foundation of the building underpinning.