The concept of precompression stress is used for estimating soil strength of relevance to fieldtraffic. It represents the maximum stress experienced by the soil. The most recently developed fitting method to estimate precompression stress (Gompertz) is based on the assumption of an S-shape stress-strain curve, which is not always fulfilled. A new simple numerical method was developed to estimate precompression stress from stress-strain curves, based solely on the sharp bend on the stress-strain curve partitioning the curve into an elastic
and a plastic section. Our study had three objectives: (i) Assessing the utility of the numerical method by comparison with the Gompertz method; (ii) Comparing the estimated precompression stress to the maximum preload of test samples; (iii) Determining the influence that soil type, bulk density and soil water potential have on the estimated precompression stress. Stress-strain curves were obtained by performing uniaxial, confined compression tests on undisturbed soil cores for three soil types at three soil water potentials. The new method performed better than the Gompertz fitting method in estimating
precompression stress. The values of precompression stress obtained from the new method were linearly related to the maximum stress experienced by the soil samples prior to the uniaxial, confined compression test at each soil condition with a slope close to 1. Precompression stress determined with the new method was not related to soil type or dry bulk density. This might be due to a too small range for both parameters, but it may also emphasize the complex effect of soil structure on soil mechanical strength.