Subsurface erosion and seepage in Banks Peninsula [New Zealand] loess
1990
Yetton, M.D.
Subsurface erosion in the loessial soils of the Banks Peninsula, New Zealand, is essentially a result of the grain size. Other factors controlling erodibility include clay content, density and the potential for slaking and dispersion. The role of dispersion may have been over emphasized in earlier work because of the terminology adopted in the standard classification of results from the Pinhole Erosion Test. A revised classification which has proved practical for local loess soils is outlined. Field investigation of subsurface erosion involves the application of several standard techniques such as geomorphic mapping, auguring and excavation. More specialized dye and smoke tracing methods are also very useful. Remedial options for sites of subsurface erosion can be divided into two groups. Various water control measures are outlined which can prevent continued erosion. However if the existing cavities are large, damaging subsidence may still continue. In situations where subsidence and collapse is causing damage ground support measures may be adopted. These include piling, excavation and backfilling, and in some cases the use of lime based slurries for grouting
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