In-Situ Monitoring Of The Post Construction Settlement And Soil Behavior Of Embankment Constructed By Expansive Soil In High-Speed Railway

This dissertation is based on the project of key technology research of expansive soil embankment construction of Nanning Inspection and Repair Depot for Motor Cars. An expansive soil embankment test section is constructed in Nanning, Guangxi., and in-situ monitoring test is carried out in it to research the post construction settlement of railway embankment and the change of expansive soil behavior.According to the construction method of expansive soil embankment of Nanning Inspection and Repair Depot for Motor Cars, a expansive soil embankment test section is constructed, which is designed in accordance with the speed of 350km/h high-speed railway embankment. The embankment consists of two parts:one was filled with cement-treated expansive soil; another part filled only with expansive soil. Some monitoring equipment is installed in it, and then the in-situ monitoring test is made for more than 7 months.The settlement plates and section subsidences pipe are buried to monitor the the post construction settlement of basal layer, the results show that the largest settlement of the embankment constructed by cement-treated expansive soil is about 1mm; the single-point settlement gauges are buried to monitor the settlement of the embankment body, the results show that the largest settlement of the embankment constructed by cement-treated expansive soil is about 1.5mm; the settlement observation piles are buried to monitor the the post construction settlement of embankment surface, the results show that the largest settlement of the embankment constructed by cement-treated expansive soil is about 2.7mm. By comparison, the settlement of the embankment filled only with expansive soil is larger, and more time is needed to settle. Furthermore, the inclinometer tubes and side piles are buried to monitor the lateral deformation, the results show that the lateral displacement both two part of the embankment test section is very minute, and even can be ignored.The humidity sensors, temperature sensors, moisture potential sensors and earth pressure cells are buried to the change of monitor soil humidity temperature, soil suction and earth pressure in expansive soil embankment, the results show that in the shallow surface layer, hygrothermal exchange strongly wih outside, so these parameters change greatly. As the depth increases, the change reduced. By analyzing the relationship between humidity and temperature, the results show that the soil temperature is mainly influenced by seasonal variations. Under the shallow surface layer, the mutual influence becomes apparent. The humidity infiltration would help temperature to transfer. But conversely, the influence of emperature transfer to humidity infiltration is relatively weak. By analyzing the soil-water characteristic curves, the results show that the strength of expansive soil would decay continuously with wet-dry cyling.In the last, we research the depth of climate influence, the results show that it is mainly about 0.5m; the maximum can reach 3m.