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In construction jobs that face unique challenges of unstable soil and pervasive ground water, the technique of ground freezing with liquid nitrogen has proven to be the best solution compared to conventional soil treatment methods.
Ground stabilization is essential in construction. Ground-freezing with liquid nitrogen (LIN) is sometimes a better solution than conventional soil-stabilization methods.
Soil-freezing with LIN has become a standard procedure for treating unstable soil and groundwater control.
Ground freezing - Process Description
Installation: Copper freeze pipes with a standard diameter of 2” (54 mm) are installed, at an average distance of 2” (54 mm) On the inside, downpipes with diameters of ½” (10–12) mm are installed.
Freezing: LIN is fed into the pipes through insulated supply lines. The LIN vaporizes, with 1 kg of LIN extracting about 200 kJ of energy from the surrounding soil, cooling and freezing it. The vaporized cold nitrogen (i.e., exhaust gas) extracts another 100 kJ from the ground. After about one week, this process forms a frozen wall with a diameter of about 1 m. This so-called “establishing phase” lasts four to seven days, and about 300 - 500 gal (1,500–2,500 l) of LIN is used to freeze 1 cubic yard (0.75 m³) of soil.
Maintenance: In the subsequent maintenance phase, the LIN supply is reduced. The frozen soil stops expanding and maintains its volume. Maintaining 1 cubic yard of frozen soil requires about 20 gal (70 l)
Ground freezing - Process Benefits
Soil-freezing with LIN offers numerous advantages:
Investments in a LIN freezing plant are only a fraction of those to install a brine freezing unit.
The temperature of the frozen soil is substantially lower (and its stability therefore higher) than with a brine freezing plant.
LIN’s low temperature -320°F (–196°C) allows soil-freezing in four to seven days – substantially quicker than the one month required by the brine freezing process.
The process is environmental friendly, with no hazardous substances, vibrations, or ground water pollution or extraction.
The process is suitable for automation.
The process offers a combination of sealing and static support.
Systems have a high tolerance to soil humidity (5–100%); frozen soil is 100% watertight, and there is no ground water control.
The hardness of frozen soil is comparable to concrete.
The solidification of the soil is only temporary; after shutting down the LIN supply, frozen soil will melt in a few weeks.
Ground freezing - Linde Service and Coverage
Linde does much more than deliver LIN. In line with customer needs, Linde offers static calculations, installation support, support during safety concept layout, and onsite maintenance and assistance.
Our specialized Industrial Services Group allows us to guarantee quality on a global basis. Our current projects in Singapore are running according to schedule, despite very difficult conditions (e.g., 150 ft below the surface, soil temperature of 79 F and tunnel-blasting).