Effect of Long-Term Soaking on the Distribution of Moisture and Total Soluble Salts in Compacted Gypsiferous Soils

Sabah Razouki

Presented in this paper is a study of the effect of long-term soaking on the distribution of moisture hence on the dissolution of total soluble salts (T.S.S.) and its distribution along compacted CBR samples of gypsiferous soil.

The soil tested is a fat clay of CH grouping according to ASTM specification and A-7-6 (42) according to AASHTO soil classification system, with about 34.5 % T.S.S. and about 33 % gypsum content.

For this purpose, sixteen CBR samples were prepared at 95 % relative modified AASHTO compaction and 17 % optimum moisture content. For each soaking period of 0,4,7,15,30,60,120 & 180 days, two samples were prepared and loaded by 40 lb (178N) surcharge load.

The paper reveals that the moisture content along the CBR soil samples increased with increasing soaking period. This increase is more pronounced at the top of CBR soil samples than that at the bottom, while little increase in moisture content took place at the mid-depth of CBR samples even after 180 days soaking period. This phenomenon is in good agreement with the distribution of T.S.S. and gypsum content along the CBR soil samples for different soaking periods.

An empirical equation is introduced in this paper that enables the determination of T.S.S. at the top of CBR samples after different soaking periods from the initial T.S.S. content.

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