An Experimental Study on Engineering Characteristics of Improved Weathered Granite Soil for a High-Speed Railway Subgrade in South China

Samples of weathered granite soil from job sites of a high-speed railway project in south China were tested in the laboratory. The results suggested that the soil could not meet the subgrade requirement of the high-speed railway in China. To address this issue, chemical treatment approach was examined in this study. The weathered granite was treated with two types of agents, lime and cement. A series of scenarios with varying dosages were investigated. The engineering characteristics of the treated soil including strength, deformation, moisture stability, and others were evaluated comprehensively through in-depth laboratory testing. As a result, it was revealed that the 5 % cement treatment scenario was most preferred. Furthermore, to verify the effectiveness of the treatment, settlement was monitored on a test road. The cumulative settlement curves indicated that the settlement in the treated subgrade reached a stable state since approximately 250 days from the completion of construction. This was sufficiently earlier than the installation of railway tracks. It was also found the settlement could sufficiently meet the Chinese Specification requirement. In summary, the proposed approach based on rigorous engineering testing and evaluation successfully improved the weathered granite for it to serve as a high-speed railway subgrade material in China.