EVT - Disposal and Back Fill Technology

When extraction mining comes to an end...

...in most cases work continues for a good period of time with follow up tasks. On the one hand former surface mining areas  including dumps need reclaiming and shafts have to be closed securely; on the other hand underground cavities must be secured to avoid the danger of slow or sudden vertical movements of the ground surface. For this reason these cavities are filled with back fill material, which can originate from within the same mine or it can be delivered from an external source. The disposal and back fill technology department supports operators of mines that are to be back filled or of succeeding owners with former active mines as well as operators of active mines that are obliged to back fill, or do back fill to be more resourcefully efficient. Support consists in providing services concerning the development of mixture recipes, testing of residual materials on their suitability for the use in mines and the development of processes for the implementation of back fill materials.

Special problems need individual solutions.

This is especially true for mining in saliniferous formations. Usual building materials like the ones based on cement or plaster fail in such environments because of no or limited stability under various saliniferous conditions. On top of this the used building materials have to be compatible with the adjacent mineral salts and must not damage them during placement or in their set state. The division “building materials” within the department for disposal and back fill technology develops and delivers special building materials for excavation mining and solution mining – the special needs of every deposit is considered to find the right solution for dam constructions, flow barriers, shaft seals, injection works, temporary or permanent closure of bore holes and for any other building steps and safety measures.

Services provided by Disposal and Back Fill Technology

Suitability tests of industrial waste for back fill and disposal

Evaluation services

  • Evaluation of the suitability of industrial waste as back fill in mining
  • Evaluation and assessment of wastes to be deposited in an underground waste disposal site
  • Preparation of the necessary documentation for the application to achieve the general permission for back fill materials according to §4 GesBergV

Consulting and services

  • Consultation of back fill mines and underground waste disposal sites for the safe utilisation and disposal of waste
  • Long term safety verification for the disposal of chemo-toxical wastes in salt rock
  • Evaluation of the waste type
  • Preparation of safety data sheets and operation manuals
  • Classification of wastes according to hazardous materials regulation and waste index regulation
  • Assessment of environmental effects

Development of mixtures for mortars used in mining, as well as for back fill and mining dam materials, other building materials

  • Mixture recipes for back fill materials used in hydraulic and mechanic processes (slurry back fill, paste back fill, dump stowing and big bag stowing)
  • Recipes for granulation, pelletizing and briquetting
  • Setting up of processing parameters
  • Proof of the structural-physical suitability of wastes and back fill materials
  • Proof of the compatibility with the host rock
  • Examination and assessment of the degassing behaviour
  • Mortar systems on the basis of various salt solutions and binders
  • Particle free supersaturated salt solutions and salt hydrate melts for injection media
  • Dam building materials with and without expansion capacity
  • Building materials with storage character for front elements on dam building sites
  • Development of recipes for the production of mineral foams

Process development and plant layout

  • Utilisation of waste from mining or waste from other industries in mines and cavities (slurry back fill and paste back fill) as well as waste through dump stowing and big bag stowing
  • Fabrication of back fill products and granulated and compacted back fill materials
  • Fabrication of mineral foams
  • Recycling of industrial wastes containing salt
  • Basic engineering
  • Preparation of application documents for licensing procedures concerning environmental legislation
  • Accompanying of the licensing procedures concerning environmental legislation
  • Technological assistance during start up of back fill facilities
  • Concepts for the placement of jointing constructions in saliniferous formations
  • Planning, supervision and monitoring of dam constructions

Testing laboratory for back fill and construction materials


  • Grain size distribution measurements through screening, laser particle analyser and photo-optical analysis
  • Solid density, overall density, bulk density, tamped density and density of fluids
  • Proctor density
  • Tests on compression and tension strength
  • Measurement of Young's modulus
  • Compaction behaviour under pressurised conditions (short and long term tests)
  • Uniaxial compression test of soils, setting characteristics, expansion and shrinking behaviour
  • Rheological examinations (viscosity, flow characteristics)
  • Measurements in a pump testing station (pipe viscometer)
  • Determination of gas emissions (quality, quantity)
  • Thermal analysis (DTG, DSC)
  • Climatic measurements
  • Abrasion tests on granulated material
  • Static single particle strength