HomePressurized Vacuum Preloading
Release time：Jul 24,2023
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The vacuum preloading method utilizes the vacuum combined loading method to extract air through a vacuum device, and the sealing film on the surface of the foundation is pumped into a vacuum state. This creates a pressure difference between the inside and outside of the vacuum membrane (i.e. between the sand cushion layer and the vertical drainage pipe and the foundation), forming a negative pressure. Under the action of negative pressure, the water flow in the soft soil layer gradually seeps out, and the water pressure in the pores continuously decreases, thereby accelerating the discharge of pore water, causing the soft soil to gradually consolidate and improving the consolidation degree of the foundation soil.
However, after working for a period of time, based on on-site experience, the filter membrane on the surface of the plastic drainage pipe and filter pipe is greatly reduced in filtration and permeability due to blockage by fine sand particles, resulting in a decrease in water flow rate and affecting the drainage performance of the entire system.
After the surface filter membrane of the plastic drainage board is blocked by fine sand or silt, its water permeability will greatly decrease, leading to a decrease in the drainage board's water flow rate. At the same time, filter pipes and Geotextile soaked in water for a long time are also easy to be blocked by sand and sludge, which affects the drainage performance of the Plumbing. Moreover, although the general vacuum preloading has been sealed in each fixed unit, due to the large area of the site, the construction difficulty increases, the depth of the sealing ditch is not enough, and the vacuum degree of the site is easily insufficient. To address the above issues, a pressurized vacuum preloading method can be used.
The working principle of pressurized vacuum preloading is the same as that of general vacuum preloading, except that a pressurized pipeline is used on a general basis. After the consolidation degree of the soil layer using the general vacuum preloading method reaches 40%, the newly added pressurized pipeline begins to work. This will increase the positive air pressure at the center of the soil layer (increasing to 400kPa), which in turn will increase the pressure difference between the center of the soil layer and the drainage plate, significantly improving the reinforcement effect of vacuum preloading.
Advantages of pressurized vacuum preloading compared to conventional preloading
Because the pressurized vacuum preloading construction facility directly connects the anti clogging drainage pipe with the vacuum pipe, sludge and sand particles cannot enter, and the vacuum state can directly enter the interior of the anti clogging drainage pipe. This will cause a pressure difference between the inside and outside of the drainage pipe filter membrane that is larger than that of conventional vacuum preloading, thereby causing a rapid decrease in water content in the soft soil layer; Because the pressure boosting pipes are evenly arranged in the soil, they will make the soil uniformly stressed, and the water in the soil will flow in a directional manner under the pressure difference, accelerating the consolidation speed of the soft foundation soil layer, thereby improving the quality and degree of consolidation of the foundation. The sealing system in the pressurized vacuum preloading treatment method is sealed through hand joints and steel wire hoses, which greatly improves the sealing performance compared to conventional vacuum preloading and ensures the vacuum degree in the membrane, making the consolidation effect of the soil more significant.
Construction process of pressurized vacuum preloading
In the process of vacuum preloading for soft foundation construction, the control of the vacuum degree under the membrane is crucial. The vacuum degree under the membrane directly affects the consolidation degree of the soil, thereby affecting the quality of the entire project. So it is recommended to use computer technology to establish a mathematical model for vacuum degree control, develop control computer programs, and ensure the vacuum degree range of pre compression treatment. And by using pressurized vacuum preloading, the settlement during the preloading period can be increased and the consolidation time can be shortened; After pressurization treatment, it can effectively reduce the groundwater level in the vacuum preloading area, accelerate the consolidation of soft foundation, and improve the quality of construction projects.
