Soil stabilisation for reduced cost slurry storage
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Industrial partners: ADAS
Sponsors: BPEX, EBLEX, DairyCo
Duration: January 2009 – May 2009
This project investigated the potential of soil stabilisation techniques to increase the range of soils which could be suitable for construction of slurry storage lagoons.
Current nitrate pollution regulations require pig farmers to install sufficient storage to hold a minimum of 26 weeks slurry production before 2012 if they are in a Nitrate Vulnerable Zone (NVZ). Many farms do not have this amount of storage and will be investing in new structures in the near future. Earth bank lagoons, where suitable sub-soils are available, often represent the most cost effective storage option, both in terms of capital expended and life expectancy.
Not all soil types are suitable for lagoon construction because they cannot be compacted sufficiently due to a lack of cohesive strength. If a suitable treatment could be found to make soil ‘impermeable’ and retain stability under wetting and drying conditions, then more farmers would be able to adopt this form of storage.
Soil stabilisation techniques involve mixing materials, normally lime, cement powder or pulverised fly ash, with naturally occurring soils and consolidating them. This technique is widely used to prepare land for development where the soil strength needs to be increased, such as building and car park bases and landfill cells.
For this project, two different sub-soil types (sand and chalk) were mixed with different:
- Amounts of added cement powder
- Moisture contents
- Degrees of compaction
Compaction followed the British Standard method used for laboratory testing of soils to determine permeability and strength. After a period of curing the samples were subjected to permeability tests to establish the hydraulic gradient. Undisturbed core samples were also collected from two sites where the soil had already been subjected to a soil stabilisation treatment by a commercial contractor. These samples also underwent permeability tests.
To be deemed impermeable, a soil must have a permeability of 1x10-9ms-1 or less. None of the soils tested managed to meet the required criteria. There was no correlation between the treatments and soil type with degree of impermeabilty attained.
A consequent review of the work has suggested that lime may have been a better add-mixture. Further enquiries with soil stabilisation specialists have confirmed that the technique is being used successfully for the construction of landfill sites and sealing contaminated soils. This indicates that the technique does have potential, although the limited trial undertaken was not successful in its objectives.
Page last updated on 08 June 2010