Moisture Migration Of Expansive Soil And Lime-treated Expansive Clay In The Xinqiao Airport Area Of Hefei

In semiarid area, expansive clay behaves features of sensitiveness to climateand moisture, and usually leads to unpredicted engineering hazards such as crack,differential settlement, and even causes disasters and huge economic losses forengineering. At present, incorporation lime in expansive clay is widely used to dealwith the above problems in engineering practice. However, in company withscale-up of construction, a growing list of engineering problems occurs due tomoisture migration for lime-treated expansive clay. This is a big threat to safeoperation of critical engineering projects in expansive clay area and deserves muchattention from engineers. Therefore, it is of great significance to conduct researchon moisture migration mechanism of untreated and lime-treated expansive clay,which will provide a basis for reveal evolution mechanism of engineering behaviorsof expansive clay and unsaturated expansive clays.Basic physical properties and shrinkage-swelling characters of expansive soilsand improved soils with lime in Xinqiao international airport project area wereanalyzed, meanwhile, SEM tests were applied to discuss microstructure foruntreated and lime-treated expansive clay. Moreover, test models for mixed waterand vaporous water migration were designed to conduct series migration tests ofdifferent initial water content,0%,6%,12%, and24%, respectively. Some mainconclusions are reached as follow:(1) Fissure and micro hole are widely distributed in aggregation forundisturbed expansive clay in engineering area, and the fabric is of big expansionand sensitive to moisture migration from SEM tests. Besides, microstructure ofimproved expansive clay is mainly granule structure, various pore types with smalldiameter, and particles are full of soil skeleton.(2) The presented test models are feasible to meet conditions such as goodsealing, distinguishing mixed water and vaporous water during migration, and areof good sealing, low cost and easy to make.(3) The tests rersults indicate moisture content gradient, soil texture conditionand water content are main influence factors on moisture migration.The moisture migration amount for expansive clay with0%~24%moisture content gradient is1.46times that for treated expansive clay with6%~24%moisture content gradient.After90days migration, expansive clay water migration is2.71times the amountof the treated expansive clay.(4) The moisture migration amount increased with migration time, andcorresponding migration rate tended to be flat in later stage. The transition ofmoisture content due to moisture migration corresponded to different initial watercontent for mixed water and vaporous water. Moreover, water content variationshows nonlinear characteristic as the initial water content increases.(5) The mixed water migration rate is significantly faster than vaporous waterfor untreated and lime-treated expansive clay. Initial water content, moisturecontent gradient and migration time affect the vaporous water ratio in lime-treatedexpansive clay mixed water migration model.The results will provide a basis for large-scale lime-treated expansive clayproject in Xinqiao international airport.