科研之友
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摘要
In recent years, the Texas Department of Transportation has observed the heaving of gypsum- or sulfate-bearing subgrade soil when it has been chemically stabilized with calcium-based additives. The occurrence of sulfate or gypsum deposits in these soils is unpredictable and often localized in small areas. Current testing procedures, in which samples are collected at specified intervals for sulfate measurements, often miss these localized concentrations. A method that provides rapid and continuous mapping of sulfate content in subgrades to a depth of at least 1 m is needed. Researchers in precision agriculture have used several devices that rapidly and continuously measure the bulk electrical conductivity of the soil at high spatial resolutions (<10 ft) and depths (>= 2 ft). For the research described in this paper, the Veris 3150 was used to measure spatial variability in bulk electrical conductivity across three sulfate-bearing subgrades in Texas. The data were used to construct high-resolution maps of the subgrade conductivity and were compared with soil properties to identify potentially high-risk areas for sulfate heaving. The bulk electrical conductivity, the sulfate content, and the soil plasticity varied in tandem throughout the subgrades. This research identified areas with an electrical conductivity of >100 mS/m as having the greatest potential for sulfate problems of the subgrades tested. It also identified a technique that could be used to rapidly and effectively screen large projects for potential sulfate problems and to map the distribution of high- and low-clay subgrade soils.
- 出版日期2012
