THE ASSESSMENT OF THE COLLAPSE POTENTIAL OF FILLS AND ITS SIGNIFICANCE FOR BUILDING ON FILL.

Abstract

Fill materials which have been inadequately compacted or placed excessively dry usually undergo a reduction in volume when their moisture content is increased. This phenomenon can occur without any increase in applied stress and is commonly termed collapse compression. The increase in moisture content can be caused either by downward infiltration of surface water or by a rising groundwater level, and the associated ground movements can have a serious effect on structures which have previously been built on the fill. Consequently, where building on a non-engineered fill is contemplated, the assessment of collapse potential should be one of the most important facets of the ground investigation and a primary objective of ground treatment should be largely, if not totally, to eliminate collapse potential. The specification and control of the placement and compaction of engineered fill should also aim to eliminate collapse potential. The identification and measurement of collapse potential are rarely easy as it is not feasible to obtain undisturbed samples of many waste fills and the commonly available in situ testing techniques do not always correlate well with collapse potential. Following an investigation of collapse compression by the Building Research Establishment, a methodology for identifying and measuring collapse potential in fills is proposed which includes a newly developed procedure for a borehole infiltration test. (A)