Mechanism and advantages of vacuum preloading

Mechanism and Advantages of  Vacuum Preloading

vacuum preloading

1. Reinforcement mechanism

 Taking the atmospheric pressure as the preloading load, a layer of permeable sand cushion is laid on the soft soil to be reinforced as a lateral drainage channel, then a vertical drainage channel is set, and a water seepage pipe is buried in the sand cushion layer, and then on it. Cover one layer of geotextile and two to three layers of non-breathable plastic film, seal nearby and block the atmosphere, and then connect the water seepage pipe with the vacuum pump to pump air, so that the water permeability data adheres to a higher vacuum and the negative water in the pore water of the soil The pore water pressure, a soft land reinforcement method that gradually sucks out the pore water and air in the soil to consolidate the soil.

 Before pumping, the film is exposed to atmospheric pressure. The gas in the pores of the soil and the groundwater surface are at atmospheric pressure. After pumping, the gas in the sand cushion in the film is first extracted, and the pressure is gradually lowered. A pressure difference is formed in the film surface, so that the film is closely attached to the sand cushion. This pressure difference is called "vacuum degree". 

The vacuum formed in the sand cushion is gradually transmitted downward along the depth through the vertical drainage body, and the vacuum degree is extended by the vertical drainage channel to the nearby soil, which causes the pore water pressure in the soil to decrease, forming a negative ultra-permanent pore water. pressure. The so-called negative means that the pore water pressure is smaller than the pore water pressure in the original atmospheric condition, and the increment is a negative value. 

Under the premise of no external load, the vacuum preloading reduces the pore water pressure in the longitudinal drainage body, so that it is smaller than the porous pressure in the Tuhuaxia, forming a hydraulic gradient, so that the water in the soil empty space may be from the soil to the soil. The vertical drainage channel seeps and finally is pumped out by the vertical drainage channel to the surface sand cushion to consolidate the soft soil.

 2, The advantages of the vacuum preloading method

 Compared to the preloading method or the forced handling on soft soil improvement, the vacuum preloading has the following significant advantages:

1), Save preload data and reduce the cost of the project.

2), Fast consolidation and short construction period. When the vacuum preloading operation is carried out, the deformation of the clamp will not occur, and as long as the deformation is tightened, the ground will not be unstable. Therefore, it is not necessary to control the loading rate during construction, and the load can be applied at a rapid rate, and the speed of reinforcement is fast and the construction period is short.

 3), construction is simple. Vacuum preloading does not require the use of a lot of construction machinery during loading, and the construction disturbance is small, and it is not easy to cause construction problems. The construction tools and equipment are simple, the construction is convenient, and the work efficiency is high, which is suitable for large-scale ground reinforcement. The effect of reinforcement is also quite good.

 4), reinforcement depth is deep. Soft soils also use well point precipitation to enhance concrete construction. The effect of vacuum preloading on deep consolidation is more significant than the use of well point precipitation to enhance enthalpy.

Tips：
For more technique articles and resources regarding vacuum preloading method, you can visit the official site at www.sunzo99.com