The crystallization and salt expansion characteristics of a silty clay

摘要

To investigate the mechanisms and principle for salt expansion, theoretical analysis, micro-fabric observation and salt expansion tests are conducted to a silty clay containing sodium sulfate. The equations for calculating the crystalized sodium sulfate in soil are derived through theoretical analysis. In the microstructure test, long strip crystal bridges and bulky crystals are found in saline soil. When these crystals grow upon cooling, soil is supposed to expand. In salt expansion tests, the effects of compaction effort, water content, and salt content of soil are studied. The salt expansion data demonstrate that the volumetric content of crystal seems to have a linear relation with the volumetric strain of saline soil. Such relation seems to be unique and is applicable to the salt expansion prediction of sulfate soil with any water content, salt content and dry density. As the migration of salt in this study is negligible, the salt expansion tests can be regarded as element tests and the relation obtained can be used to build constitute models for salt expansion.