Modern building procedures and requirements demand that the selection and stabilisation of soils for the purposes of rammed earth construction be better quantified. This study examines the relationships between soil properties, stabiliser treatments, and stabilised strength and density for 111 soil samples taken from sites in New South Wales (Australia), and develops new quantitative criteria for soil assessment, selection, and stabilisation. Laboratory measurements of soil particle size distribution, plasticity, and shrinkage were made for each soil. Various quantities from 0-6 % of lime, cement, and asphalt were added to the soil samples, and the resulting 230 specimens were compacted, and cured for 28 days. Determinations were made of the optimum moisture content, maximum dry density, and compressive strength of the stabilised material. The samples showed stabilised strengths ranging from 1.0-5.4 MPa, with a mean of 2.62 MPa, and densities from 1.44-2.21 t/m3, with a mean of 1.86 t/m3. The results show that over 90 % of the variation in stabilised strength and density of the samples is due to variation in soil properties, with differences in stabiliser type or stabiliser quantity being relatively minor. The most important soil properties explaining stabilised strength are linear shrinkage and plasticity index. These properties have been used to categorise the soils into three groups on the basis of their suitability for stabilisation as measured against a compressive strength criterion of 2 MPa. Favourable soils have shrinkages of < 7.1 % and plasticities of < 16 %, and 90 % of these samples passed the 2 MPa criterion. Satisfactory soils have shrinkages of 7.1-13.0 % and plasticities of 16-30 %, and 65 % of these samples had strengths in excess of 2 MPa. Unfavourable soils have shrinkages of > 13 % and plasticities of > 30 %, and only 10 % of these samples exceeded the 2 MPa value. Soils in the favourable and satisfactory categories can be further discriminated using textural information. On that basis, all soils classified as favourable, and those classified as satisfactory and which also have sand contents < 60 %, are recommended as being suitable for stabilisation. Soils not fulfilling these criteria are unlikely to be successfully stabilised and should be rejected. These results stress the importance of selecting a soil favourably predisposed to stabilisation. Field techniques to search for such soils could be refined on the basis of the new soil criteria presented. Use of the criteria should also minimise unnecessary laboratory testing of the density and strength of soils that subsequently prove unsuitable for stabilisation. A flow chart is presented to guide practitioners through the different stages of soil testing, assessment, and rammed earth stabilisation.
| Identifer | oai:union.ndltd.org:ADTP/187768 |
| Date | January 2001 |
| Creators | Burroughs, Van Stephan, School of the Built Environment, UNSW |
| Publisher | Awarded by:University of New South Wales. School of the Built Environment |
| Source Sets | Australiasian Digital Theses Program |
| Language | English |
| Detected Language | English |
| Rights | Copyright Van Stephan Burroughs, http://unsworks.unsw.edu.au/copyright |
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