| Based on subgrade engineering of Qing-Yi highway in XinJiang, the author conducted a systematic study on how to improve and stabilize the silty clay as the material of roadbed, by centrifugal model test, theoretical analysis method and the field observation. The author study the mechanism of different stability improved method and modified effects. This study,fistly, carried out a series of lab tests, explore the use of cement for subgrade stabilization, under the different cement dosage, analyze the changes law of the unconfined compression strength, modulus of resilience and CBR value of the soil, determine the appropriate cement-dose which can be used in the actual project; studied use the local natural gravel to improve the performance of the silty clay, and study the different proportion of sand and gravel mixing, study the changes of the compression modulus and the CBR value, and determine the appropriate blending ratio. Design centrifugal model test, through the improvement of geocell reinforced gravel, cement improvement, three kinds of modified improved scheme of centrifugal model test, analyzed in three improvement scheme of subgrade deformation character. Secondly,we use the finite element analysis software for all kinds of powder clay subgrade scheme improved by numerical simulation, analysis of different roadbed settlement and stable condition improved scheme, further verified the effect of different improvement plan improvements. Through the contrastive analysis of the improved method is different, determine the gravel soil using modified powder as subgrade filling the practical improvement scheme. Thirdly, in the field of silty clay through improved settlement observation, further validation of gravel improvement scheme.
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