The developers of the liquid soil method

For the installation of underground structural components, the corresponding soil area has to be excavated first, and then partly or completely backfilled with soil. The upper or uppermost backfilling area can also be used as a subs tructure for traffic routes. Here it is advantageous for the long - term usability of the structural members if the originally excavated soil can be reused for backfilling. From 1998 on, the private research institute for liquid soil "Forschungsinstitut für Flüssigboden GmbH"m (FiFB) (former LOGIC Logistic Consult Ingenieurgesellschaft mbH) developed the liquid soil method for the economic placement of this excavated soil, patented it in various variants and for the first time used the term "liquid soil method " (Flüssigbodenverfahren in German) and coined it in the sense of restoring the original soil situation after excavations. The liquid soil method has been developed in numerous national and international research and development projects that began with the development of a combined manhole system. The conventional, temporarily flowable construction materials, such as insulating material ("Dämmer"), filler, foam concrete, soil mortar, etc. were hydraulically hardening materials and did not sufficiently meet the technical requirements for a suitable backfilling material and the protection of the built - in pipes and conduits. Only a behaviour of the backfill material similar or equal to that of the natural soil ensures the same load - bearing capacities in the subsoil and thus the freedom from settlement of roads, substructure with pipes and conduits and no longer represents a foreign body in the subsoil that damages the installations such as pipes. The need for the development of the liquid soil method had arisen due to technical constraints and environmental requirements (eg the German Waste Management and Product Recycling Act). The development work since 1998 has led to technical and technological solutions that ensure the subsequent accessibility of all super imposed conduits, even without opening trenches and without relocating higher - lying pipes and conduits – a revolution in sewer and pipeline construction. The development of a procedure for the use of all types of soil relevant to construction was also preceded by the desire to overcome known quality problems for sewers, conduits, and roads:

• Settlement as a result of compaction problems or as a result of drainage in the backfill areas
• Settlement as a result of backfill material that does not behave in the same way as the surrounding soil in terms of shape and size
• Pipe breaks as a result of poor compaction of the bedding zone
• Road damage as a result of non - compacted sheeting areas
• Road damage from punching of solid foreign bodies under the road or wash- out and settlements
• Road and pipe damage due to the missing bond between the backfill material and the trench walls
• Consequences of the violation of environmental law requirements of the legislator. 

From: Wikipedia, keyword "Flüssigboden", version of 19 July 2017, 15:36, available at https://de.wikipedia.org/wiki/Fl%C3%BCssigboden