Comparative research on lower bound depth of collapse loess

Abstract

The lower bound depth of the self-weight collapse of loess is used to determine the type and grade of a collapsible loess foundation. It is important to select a reasonable foundation treatment depth and to determine negative skin friction neutral points of the pile. This study comprehensively analyses the differences between laboratory and full-scale field testing in determining the lower bound depth of the self-weight collapse of loess. Although this lower bound depth tends to be a unique value, obvious differences were obtained in the test results obtained by the two methods. Generally, the laboratory test results were 1·25–2·90 times greater than those of the field test, mainly owing to differences in saturation, test pressure, the sample stress state and soil non-uniformity. Evaluation of the lower bound depth of the self-weight collapse of loess should therefore be based on field testing and the results from laboratory tests need to be modified. This paper puts forward a new theoretical modification method for this purpose, which could reduce the differences between laboratory and field test results.