Physical stability checklist

Emma Niemeläinen, Markku Juvankoski, Tommi Kaartinen, Jutta Laine-Ylijoki, Elina Merta, Ulla-Maija Mroueh, Jarno Mäkinen, Henna Punkkinen & Margareta Wahlström, VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, FI-02044 VTT, FINLAND.

Systematic geotechnical monitoring is required at the closed mine site to ensure that the structural integrity of the remaining eaerthworks at the site is maintained and the potential risk factors are identified in time to allow proactive response. Post-closure monitoring typically follows the same monitoring processes initiated during mining activities. Monitoring programme is designed site-specifically for each mine site. (Heikkinen et al. 2008)

The most common methods for monitoring of the physical stability of waste rock deposits, tailings impoundments, heaps and abutment structures at the mine closure are:

  1. Soil drilling, test pits and sampling for laboratory tests
  2. Geophysical monitoring
  3. Geodetic surveys
  4. Visual inspections​ ​
  5. Optical methods
  6. Groundwater and leakage monitoring
  7. Movement measurements

Several physical parameters can be measured and monitored either in situ or/and in the laboratory. These parameters are presented in Table 1. Also links to the methods for measuring each parameter can be found from the table.

Table 1. Physical parameters to be monitored.

Parameter Sub parameter Measured in the field Measured in the laboratory Measured online Links to the method used
Surface transformation Surface erosion​ x     3, 4
Lateral movements​ x   x 3, 4, 7
Settlements, holes in the ground x     3, 4, 5, 7
Slope geometry​ x   x 3, 4, 7
Soil mechanical properties Shear strength x x   1
Strain​ x   x 5
Density, consolidation x x x 1
Soil pressure​ x   x 5
Soil stratigraphy x x   1, 2
Grain size distribution​   x   1
Hydrology and seepage​ Groundwater and phreatic water level x   x 5, 6
Porewater pressure, liquefaction x   x 6
Moisture, wetted areas x     2, 4
Seepage flow amount x     5, 6
Seepage velocity​ x     5, 6
Seepage direction x     5, 6
Piping and internal erosion x   x 2, 5, 6
Changes in the water chemistry​ x x   (1), 6
Temperature​ Temperature x   x 2, 5
Foundation and abutment stability​ Movements, settlements x     7
Seismicity​ x   x 7, strong motion accelerator
Impoundment properties ​ Water level in the pond​ x   x 3, 4, level scale
Width of the beach​ x   x 3, 4
Material weathering​ Weathering x x   1, 4

References

Heikkinen, P.M. (ed.), Noras, P. (ed.), Salminen, R. (ed.), Mroueh, U.-M., Vahanne, P., Wahlström, M., Kaartinen, T., Juvankoski, M., Vestola, E., Mäkelä, E., Leino, T., Kosonen, M., Hatakka, T., Jarva, J., Kauppila, T., Leveinen, J., Lintinen, P., Suomela, P., Pöyry, H., Vallius, P., Nevalainen, J., Tolla, P. & Komppa, V. 2008. Mine closure handbook. Espoo: GTK; VTT; Outokumpu Oyj; Finnish Road Enterprise; Soil and Water Ltd. 169 p. http://en.gtk.fi/informationservices/publications/publications/latest/publication/EJ74.html