SMW method in SMW reactor is the abbreviation of soil mixing wall. SMW method is to drill and cut the soil in situ by special multi-axis stirring, and at the same time inject cement slurry into the soil at the end of the drill bit. After fully mixing, the construction unit adopts overlapping construction.
Before the cement-soil mixture hardens, H-beam or other profiles are inserted into the mixing pile to form a continuous and seamless underground continuous wall with certain strength and rigidity.
The most commonly used SMW construction method is a three-axis drilling mixer, in which the drill pipe can be used for cohesive soil, gravel soil and bedrock. In addition, some other models have been developed for the construction of urban viaducts with limited space, or for building walls on the seabed or strengthening soft foundations.
2, the difference between biaxial mixing pile and triaxial mixing pile
(1) The process features are different.
Cement and soil are mixed in situ by two vertical shafts, and the undisturbed soil is not replaced. Because the drill bit has four blades and is cross-shaped, the first mixing pile is uneven, and it needs to be mixed many times (two sprays and four mixes are often used, that is, drilling and lifting sprays, and four sprays are completed at one time). Therefore, the construction speed is slow and the quality of long piles is unstable. At the same time, the frame is top-heavy and the verticality and uniformity are not high.
The three axes rotate in the same direction, mixing the sprayed concrete with the soil, and the middle axis reverse high-pressure spraying is fully mixed with the cement-soil in the hole, and at the same time, a large amount of undisturbed soil is replaced. The three drill bits of triaxial mixing pile are long spiral cross blades, which can be evenly mixed at one time (one spray and one stir are commonly used, that is, concrete is sprayed without lifting). The pile driver is stable, the verticality of piles is good, and the lap quality between piles is high.
(2) Different cement content
The cement content of biaxial mixing pile is 7% ~ 15%, and that of triaxial mixing pile is 15% ~ 25%.
(3) The common water-cement ratio is different
0.45 ~ 0.55 for biaxial mixing piles and 1.5 ~ 2.0 for triaxial mixing piles.
(4) Different scope of application
Double-shaft mixing piles are used for waterproof curtain, cement-soil gravity retaining wall support, foundation reinforcement and inserting H-beam to form SMW construction piles.
Triaxial mixing pile is used for water-stop curtain, SMW construction pile, foundation reinforcement, groove wall reinforcement of underground continuous wall, etc.
Extended data:
Main characteristics of SWM construction piles
1. The construction will not disturb the adjacent soil, and will not cause any harm such as adjacent ground settlement, house inclination, road cracks and displacement of underground facilities.
2. The drill pipe is characterized by alternating spiral propulsion wings and mixing wings. With repeated drilling and stirring, the cement-based reinforcing agent is fully mixed with the soil, and the length of the wall is seamless, which is more reliable than that of the traditional continuous wall, and its permeability coefficient k can reach10-7 cm/s.
3. It can be used for cohesive soil, silt, sandy soil, gravel soil, pebbles with φ 100 and rock stratum with uniaxial compressive strength below 60MPa.
4. The wall thickness can be 550 ~ 1300mm, and the common thickness is 600mm；; The maximum depth of the wall is 65m, which can be further constructed according to the geological conditions.
5. The required construction period is shorter than other construction methods. Under general geological conditions, each machine-team can form a wall of 70 ~ 80 ㎡.
6. The transportation volume of spoil is far less than other construction methods.
7. The insertion depth of section steel is generally less than that of mixing pile, which can be partially recycled.
Baidu encyclopedia -SMW construction pile
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