The installation of slope drainage is often an economic means of ensuring the stability of a road cutting. Drainage may be installed either when the cutting is first made, or at a later date as a remedial measure. This report describes a study of the effect of slope drainage in a newly-made cutting in London clay. Two adjacent sites were studied, a Western site of unweathered grey clay, and an Eastern site of weathered brown clay. At each site, pore pressure measurements were made in experimental lengths with and without drainage over a period of nearly a decade. At one of the two sites, the Western site, pore pressures were high. The slope drains did not function properly, and even after repair had little effect on pore pressures. At the Eastern site, pore pressures were initially low but increased over a period of years, and the slope drains did eventually bring about some reduction in pore pressure. These observations are compared with those for an older cutting in London clays. In these cases at least, slope drainage was found to be more effective as a remedial measure than in new construction. (A)
Abstract