Ground freezing by GEOFROST

<body> <P><IMG SRC="images/000-blueline.jpg" ALT="ground freezing artificial by geofrost and anne-lise berggren" width="640" height="20"></P> <P><IMG SRC="images/000-logo_forside.GIF" ALT="artificial ground freezing by anne-lise berggren" width="640" height="150"></P> <P><IMG SRC="images/000-blueline.jpg" ALT="ground freezing artificial by geofrost and anne-lise berggren" width="640" height="20"></P> <H1>Ground freezing by GEOFROST AS</H1> <H3> An engineering and contracting company, specialized in artificial ground freezing.</H3> <p> Anne-Lise Berggren Trond Egeberg grunnfrysing markfrysning groundfreezing and agf</p> <p>GEOFROST AS, Grinidammen 10, N-1359 EIKSMARKA, Norway. Fax:. (+47) 67 14 73 53. E-mail: geofrost@geofrost.no</p> <p> <H1>GROUND FREEZING, an introduction ( agf ) by geofrost engineering</H1> 1 Introduction The usage of this method is based upon the fact that the strength of the ground increases when the ground freezes, and/or that the frozen ground becomes watertight. Ground freezing is mainly used to create a supporting structure or a watertight barrier, - but commonly also as a combination of the two. Figure 1: Principle for the strength's dependency of temperature. When the water in the ground freezes, the binding of the grain structure gets stronger than in unfrozen condition. The strength varies strongly according to the type of soil and the temperature level: Freezing occurs by removing heat flowing towards the cold part after establishing a temperature gradient. This is done by installing freezing-pipes into the ground, usually into drilled holes. The freezing-pipes are coaxial in order to make a refrigerant flow through the inner pipe and back between the inner and outer pipe: Figure 2: Principle for the transport of heat, which leads to freezing. anne-lise berggren Figure 3: Principle for the development of frost cylinders into a frost structure. The frost cylinders expand and add together into a frost construction, which may consist of one or more rows. The frozen volume is defined and can be verified. Frost structures can be made in all geological formations (crushing zones in rock, blocky moraine, deltaic deposits, ocean floor, marsh etc.) trond egeberg does thermal calculations. Because of the large ad freeze strength; one may also make use of different combinations with other construction materials as for instance wood and concrete. Frost structures can create tight attachments to irregularities in rock, around pipes, in concrete frames etc. Streetcar rails, cables and pipes do not need to be cut or redirected even if they happen to cross the path of a frost construction. There is little noise and tremors. One single method covers more functions. Results and costs are predictable. The method is environmentally friendly. 2 Different ground freezing methods Brine freezing: Brine made of calcium chloride, CaCl2, and water is the most common heat transportation medium (coolant) in the coaxial freezing-pipes, hence the name brine freezing. Calcium chloride is commonly used on roads as an antidust medium during summer time, and as an ice-melting medium in wintertime. Salt is a natural non-poisonous medium, if no anti-corrosives are added. Other kinds of brine and glycol can also be used as a coolant refrigeration plant. The coolant circulates in a closed system and parts with heat (being cooled down) by an electrically powered freezing plant. The temperature of the brine uses to be between -20 oC and -40 oC. Figure 4: Brine freezing = indirect freezing. The refrigerant commonly is ammonia, which circulates within a closed circuit inside the freezing plant (refrigerant unit). Ammonia is environmentally friendly. It is a natural matter, which, if by leakage getting out of the closed system, will not advance global heating or weaken the ozone layer. Other refrigerants may also be used, but most of them to some degree are a threat to the environment. The heat from the freezing plant is removed with water and/or air. Ground freezing done by a freezing plant which exchanges heat with a cooling circuit is called indirect freezing. Nitrogen freezing: The most widely used matter for direct freezing is condensed nitrogen (LIN). Nitrogen is extracted from the air, which contains about 78%. After use the nitrogen is released back into the atmosphere through an open pipe system. Nitrogen is non- poisonous, without smell or colour. When very cold, the gas is heavier than air and may displace it. That is why outlets are led out of tunnels and construction pits. liquid nitrogen An open system needs regularly refills from a supply tank, and large amounts of LIN are usually needed. LIN boils in the freezing pipes by the influx of heat from the surroundings. Boiling temperature at 1 atmospheric pressure is -196 oC. Since the coolant also is the refrigerant this is called direct freezing. clay and silt and sand gravel moraine Compared to brine freezing, freezing will be faster due to the low temperature, and the setup is simple. Possible water movements favor nitrogen freezing at the sacrifice of brine freezing. Figure 5: Nitrogen freezing = direct freezing. 3 What affects the costs? What affects the costs? The costs for ground freezing may be divided into three parts: rigging, establishment and operation. The cost of rigging is dependent upon the location (access, transport and distance), the size and character of the project (mobilization, necessary investments and other special circumstances). The costs to establish a frost structure are generally proportional to the volume being frozen. The expenses are also dependent upon how extensive and complicated it is to install the freezing pipes, and which criteria should be met by the ground freezing (temperature, geometry, etc.). Another factor that influences the cost is the amount of time available to finish the project. freezing plant rentalcan be nitrogen freezing or by refrigeration plant, The costs of operation are dependent upon the extent and type of project, but will mainly be proportional with the duration of the freezing, i.e. how long the protection by the frost structure is needed. 4 Areas of application TC " 3 Areas of application" \l 2 Ground freezing or groundfreezing ( agf )is first and foremost a method for temporary use, and is used while the final construction is being performed. When the need for the frozen structure comes to an end, the installations are removed and the ground thaws. Ground freezing may be used as a permanent structure, - then preferably as part of a heat pump. Under especially difficult circumstances below the ground water table, frost structures will create stable and dry conditions during tunneling. This simplifies the execution of the final construction. The development within horizontal directional drilling makes it possible to create a watertight frost structure before starting the tunnelling.  <p><a href="5_Projects/5001_The_Fjellinjen_Road_Tunnel.htm">Ground freezing by GEOFROST, The Fjellinjen Road Tunnel through Oslo</a></p> <p><a href="5_Projects/5005_The_Norwegian_Parliament_Garage.htm">Ground freezing by GEOFROST, The Norwegian Parliament Garage</a></p> <p><a href="5_Projects/5018_The_Western_Oslofjord_Sewarage_SchemeFjernvarme_Sandvika.htm">Ground freezing by GEOFROST, The Western Oslofjord Sewerage Scheme</a></p> <p><a href="5_Projects/5043_The_BI_Garage-Hamang.htm">Ground freezing by GEOFROST, The Bedriftsøkonomisk Institutt Garage</a></p> <p><a href="5_Projects/5067_The_Obbola_Bridge-Umeaa.htm">Ground freezing by GEOFROST, The Obbola Bridge</a></p> <p><a href="5_Projects/5071_The_Joint_Concern_Project_Kirkeristen.htm">Ground freezing by GEOFROST, The Joint Concern Project Kirkeristen</a></p> <p><a href="5_Projects/5079_Stortingsgt_2.htm">Ground freezing by GEOFROST, Stortingsgaten 2</a></p> <p><a href="5_Projects/5086_U2.htm">Ground freezing by GEOFROST, The U2 construction site in Oslo</a></p> <p><a href="5_Projects/5112_Gas_Storage_Karlshamn.htm">Ground freezing by GEOFROST, Gas storage in rock cavern</a></p> <p><a href="5_Projects/5114_E18_Eidangerhalvoya.htm">Ground freezing by GEOFROST, The E18 highway at Eidangerhalvøya</a></p> <p><a href="5_Projects/5127_Construction_site_in_Karlstad.htm">Ground freezing by GEOFROST, construction site in Karlstad</a></p> <p> </p> <p> </p> <p> Both in rock and soil, it will be easier to apply a watertight concrete lining when water is eliminated. In connection with tunnel portals a frost structure can avoid one or more of the following: expropriation of ground, piling of nearby houses, excavation of huge amounts of deposits and difficult securing of high unstable walls. In vertical shaft sinking through soil into rock, a frozen pressure ring may both take care of the stability of the soil and the often occurring problem with water leakages in the transition sone between soil and rock. In connection with construction sites in cities, a frost structure may often solve more tasks (stabilization and water tightening) where otherwise it might have been necessary to use several methods to secure the nearby structures and installations. Structures at the edge of a construction site may get a temporary support of frozen ground, until filling the crater restores the balance. As long as the water flow can be controlled, most soils are adequately stable. The control may be undertaken by a frost structure, operating as a watertight seal. Frost may also be used as pollution prevention, either by freezing a barrier against the polluted ground or by freezing it all. The last may as well be useful for removing and transporting polluted material to a suitable place of deposit or to destruction. Water tightening may also be useful during rehabilitation processes of waterways to waterpower installations. An ice plug may be created in a water-filled tunnel in order to empty otherwise inaccessible places without draining the whole water basin. On especially soft ground and marshland, a buoyant working platform made of ice, may serve the necessary purpose. The method is very environmentally friendly to the surface terrain. When thawed, the pipes are easily removed. GROUND FREEZING GEOFROST AS, Grinidammen 10, N-1359 EIKSMARKA, Norway. Tel.: (+47) 67 14 73 50, Fax.: (+47) 67 14 73 53, E-mail: geofrost@geofrost.no Homepage: http://www.geofrost.no</p> </body>