Study On Indices And Methods For Identification And Classification Of Expansive Soil

Theselectionofindicesandmethodsforidentificationandclassificationofexpansivesoilshasmuch influence on formulating the engineering measures, therefore, choosing reasonable indicesand methods to identify and classify expansive soils is most important. Setting out from above twoaspects and relying on the subgrade projects of HeFei-LiuAn expressway and ZhouJi-LiuAnexpressway, systematical laboratory tests have been carried on including basic physical tests,physico-chemical and mineral component analysis tests, compaction and mechanics tests etc. Thecharacteristicsofmineralcomponent,strength,basicphysicalproperties,swelling-shrinkagebehaviorofexpansivesoilsinmiddlezoneofAnHuiProvinceareexpoundedindetail.Several commonusedindicesthatcancharacterizeswelling-shrinkagemechanismsuchasfreeswelling ratio, liquid limit, plastic limit, plastic index, standard absorbent water content, colloidparticle content are studied and discussed. Integrating the above informations with statistics theory,the sensitivity of the indices is analyzed and results show that plastic index influences results ofidentificationandclassificationmostly.Studies are conducted on test methods and rationalityof free swelling ratio. The influences ofsoilsamplepreparingon thetestresultarediscussedemphatically,several problemsintestmethodsare pointed out and a suitable method is recommended. Alarge number of free swelling ratio testsbased on the above method are carried out, and to a what extent the index reflecting swelling, therelationship between the index and swelling, the characteristics of free swelling ratio and thecharacteristics of classification for expansive soil in Middle zone of AnHui Province are studied.Compared with montmorillonite content and plastic index, the norm suggested in Standard JTGD30-2004 doesn't fit identification and classification of expansive soil in Middle zone of AnHuiProvince.Asuitablenormissuggestedanditsrationalityisverifiedbasedoncollectedsoilsamples.Regarding the new index suggested in Standard JTG D30-2004—standard absorbent watercontent, its physical significance and test method is expounded briefly, a large scale of standardabsorbent water content tests are carried out and to a what extent the index reflecting swelling, therelationship between the index and swelling,free swellinig ratio characteristics and thecharacteristics of classifying for expansive soils in Middle zone of AnHui Province are studied.Comparision with montmorillonite content and plastic index, the norm suggested in Standard JTGD30-2004 doesn't fit identification and classification of expansive soils in Middle zone of AnHuiProvince. A suitable norm is suggested and the rationality is verified based on collected soilsamples.A new index is introduced—relative free swelling ratio firstly suggested by Indian scientistsPrakash and Sridharan, which is defined as the ratio of the equilibrium sediment volume of 10 goven dried soil in distilled water to that in coal soil(or CCl4). The significance and advantanges ofthe index are described. Relative free swellingratio and physical and mechanics properties tests areconducted systematically. It can be found out that when comparing to free swelling ratio, relativefree swelling ratio shows better correlation with cation exchange capacity, specific surface and...