This paper synthesizes recent developments in construction that utilizes pindan sand-clay as a structural layer. It covers identification of suitable material, construction protocols, including compaction moisture control and compaction methods, techniques for layering during construction, modified construction quality control techniques, and curing/drying back. The latest results from pavement performance measurements, including Falling Weight Defelectometer (FWD) results, are given to support the proposed techniques. Pindan sand-clay is a collapsible soil that occurs extensively in the Kimberley region of Western Australia. It is typically a low-density material, which may densify under loads with high moisture contents and can result in differential movement within the pavement structure, leading to general unevenness or even failure. Pindan sand-clay materials display a self-cementation property with substantial strength gain over time in dry moisture conditions. Typically soaked CBR tests on disturbed materials yield results in the range CBR 3-7. Yet under dry field conditions, the insitu uncompacted material (with low density and high void ratio) can yield unsoaked results of CBR 17-32. This opens up the possibility of using such material as a structural layer in pavements. Under a sealed surface, where low equilibrium moisture content has been designed in, compacted pindan sand-clay materials may exhibit field CBRs in the range 20-80. This paper reports on laboratory testing to characterize and model the behavior of pindan sand-clay materials. Scanning electron microscopy, X-ray diffraction testing, and caution exchange capacity were used, as well as routine soil classification testing and ICP-AES chemical analysis. Suction testing gave a relationship between matrix suction and shear strength. From this testing, a model is developed to explain the behavior of these materials under various loading and moisture conditions. Using this model, the design principles for the use of pindan sand-clay and the control of risk through control of pavement moisture levels are discussed. Conventional construction is inappropriate for the use of pindan as a structural layer, and has tended instead to focus on its treatment as a deleterious material.


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  • Accession Number: 00964377
  • Record Type: Publication
  • ISBN: 087659229X
  • Files: TRIS, ATRI
  • Created Date: Oct 15 2003 12:00AM