1. Preparation stage of freezing construction: including installation of freezing station, connection of freezing pipeline and debugging of freezing system.
2. Freezing stage: Freezing begins to form artificial frozen soil curtain, which is generally divided into positive freezing and negative freezing.
3. Melting and grouting stage: When the shaft reaches the intersection of frozen walls and tends to be basically stable, single liquid cement slurry can be used to stop the water on the outer wall of the shaft, and artificial grouting can be carried out after the freezing stops, so as to achieve the purpose of blocking the water seepage point.
4. Shaft excavation and maintenance stage: after freezing, shaft excavation is carried out to maintain and monitor the enclosure structure.
Freezing method is a special construction technology that uses artificial refrigeration technology to freeze the water in the stratum, make natural rock and soil become frozen soil, increase its strength and stability, isolate the connection between groundwater and underground engineering, and carry out excavation construction of shaft or underground engineering under the protection of freezing wall.
The patented technology was first used in Russian gold mining, and later used by German engineers in coal mine construction. The technology tends to be mature and has been widely used in subway, deep foundation pit, mine construction and other projects. The origin, basic principle, refrigeration system, reinforcement mechanism and construction method are introduced in detail.
fundamental principle
Freezing technology is a special construction technology that uses artificial refrigeration technology to freeze the water in the stratum, make natural rock and soil become frozen soil, increase its strength and stability, and isolate the connection between groundwater and underground engineering, so as to carry out underground engineering excavation and construction under the protection of freezing wall. Its essence is to use artificial refrigeration to temporarily change the properties of rock and soil to strengthen the stratum.
Freezing wall is a temporary supporting structure. After the permanent support is formed, the freezing stops and the frozen wall melts. The freezing refrigeration technology of geotechnical engineering is usually completed by using the endothermic phenomenon that substances change from liquid to gas, that is, the vaporization process.