The uses of Scanning Electron Microscope (SEM) for the micro-structural observation and the Mercury Intrusion Porosimetry (MIP) for the measurement of pore size distribution are now commonly adopted techniques in many researches on the microstructure of soils. Even though there are a number of results obtained by active researches and many of data have been accumulated so far, however, questions are still under discussion on the generalization of specimen preparation, testing procedures and test parameters used in those micro-structural studies.
　For example, in both use of SEM and MIP for clays, the elimination of water in clays is required maintaining its inherent soil structure. Furthermore, the preparation method of the specimen for SEM observation, like the size of specimen and cutting the specimen to obtain the observation surface, is different according to the researchers. However, the effect of the difference by drying and preparation method on these test results is not well known and the specification on the selection of these methods considering the soil condition has not yet been established.
　For these reasons, this study is to suggest the appropriate test procedures and conditions for SEM and MIP, for the comprehensive and proper use of information and data provided by different researchers and institutes. In the fundamental process to this purpose, this research is involved with the investigation on the effect of drying method and specimen preparation on micro-structural observation results and pore size distribution according to various soil conditions and different testing methods. Soils of different conditions are used for the test such as slurry state of clay with extremely high water content, reconstituted clay samples and undisturbed soils of Ariake and Osaka clays. And three type of drying methods such as air drying, oven drying and freeze drying are adopted. Based on these results, effect of drying process on the consolidation characteristics and the pore size distribution for the Osaka Pleistocene clay under the different loading pressures was clarified by the concept of two different pores such as intra-aggregate and inter-aggregate pores.