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Technical Note |
Dept. of Civil Engineering, New Materials Group, The University of Leeds
The study of soil structure has made great progress in recent years, because of the development of the Scanning Electron Microscope and the realization that it may be possible to relate soil structure to soil properties in the classical manner of materials science (e.g. Barden 1972). One of the persistent problems that harass soil structure investigators is that of preparing an undisturbed sample, and being reasonably certain that it stays undisturbed at all stages of the investigation. This had led to the development of various methods of setting the soil sample, usually by introducing some material into the pores which provides a firm matrix for the soil particles (Tovey 1973). It appears that there are instances where this has been done by nature, and primary mineral soil structures have been effectively preserved by the secondary deposition of minerals from groundwater; this is particularly true in the case of loess soils.
The structure of loess is of particular interest from the geotechnical point of view because of the collapse phenomenon which is observed in loess soils. It was suggested long ago by Terzaghi (1950) that as mineral particles become smaller the proportion of platelet shapes increases; thus loess could be composed essentially of quartz plates in a very meta-stable structure. This was in fact proposed by Krinsley & Smalley (1973) as a consequence of their hypothesis on the operation of a cleavage mechanism in quartz particles below a certain critical size. Thus, if concretions in loess preserve the soil structure they
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