Civil engineering and extraction of natural resources
Due to space constraints in conurbations of big cities, it is inevitable to use space underground for living and usable spaces, transport systems and, above all, for storage facilities. Furthermore, since industrialisation, most different natural resources are extracted from great depths of the earth which have only made life in today’s form possible for humanity.
During civil engineering works and while machines penetrate great depths of the soil, entering groundwater is often the big problem. The collapse of shaft walls should also be avoided. In some layers of earth, a problem to be solved is also dust formation. The freezing shaft method is used when water-bearing, loose rock strata have to be drilled. For this purpose, freeze holes are drilled around the planned shaft which are then impinged with a cooling agent.
The freeze drilling holes consist of an external pipe made of steel and a downpipe made of plastic. Via the downpipe, the cooling agent gets to the borehole bottom and rises up again in the outer annular pipe. During this process, heat is drawn from the surrounding strata, with a frozen mass coming into being. Under protection of this, the shaft is then sunk like in a stable rock.
Freezing building site means to provide it temporarily with desirable characteristics, that is strength, and to give water tightness to the groundwater. The main advantage over difficulties when injecting is safe frost spreading around the pipe with the coolant, depending on the physical conditions and properties of the soil layers, of the water located therein and the fed cooling energy. That way, there normally does not occur any permanent change of the building site, its chemistry or the groundwater.
Successful application solutions
Multi-stage centrifugal pumps with special cryogenic engineering and anti-freezing function
of the shaft seal. Type NH..X
In central big freezing plants, large quantities of coolants are cooled down to low temperatures of up to -50°C. By means of powerful, multi-stage pumps, these refrigerants are then pumped through the widely branched pipe system installed in the mine shafts. As a result, the surrounding soil is frozen, whereby stable shaft walls occur while being sunk which are then permanently be secured using support walls. Furthermore, it is ensured that no water flows into the emerging shafts.