Test And Theoretical Analysis About The Process Of Settlement Of Highway Subgrade

Highway subgrade is soil body structure including natural earth foundation and artificial fill embankment. The weight of fill embankment causes the settlement of natural earth foundation and artificial fill embankment. The natural earth foundation may be saturated soil and unsaturated soil, but the fill embankment generally is unsaturated soil. Under certain load the settlement of saturated soil or unsaturated soil is a time-developing process. During the construction of highway embankment the soil layer is rolled at random, so that the load which causes the settlement of highway subgrade is a time-developing process. The settlement of highway subgrade includes settlement during construction period, settlement after construction and final settlement. The sum of settlement during construction period andsettlement after construction is the final settlement. The settlement during and after construction can be adjusted through varying the time of precompression consolidation, and appropriate adjustment can reduce the diseases of highway after construction and yield good economic returns. So that calculating process of settlement of subgrade becomes the key to these problems. However at the present time it is the calculating of the final settlement that is practical, and there has not been a feasible method of calculating about the settlement during construction period.It can be said that the analysis and calculating of soil body deformation and process of deformation is one of the most classical topics in soil mechanics at all times. Much research has been carried out and abundant experiences are available.However because of the incrementally loading of the subgrade construction and its long process, the variation of density relevant modulus of compressibility and coefficient of permeability of road embankment and foundation along with the changing of the load on top, the complexity and polytropism of the soil types along the highway, the relatively less funds that can be used for measuring and calculating settlement on per square meter, the absence of practical experience of calculating and analysis, the high criteria at the present time for the planeness of high class highway, the answer to this problem seems to be very important in highway industry.This paper puts importance on in situ tests and laboratory soil test, and attempts to find genuine law of deformation development. With one dimensional compression and consolidation which is similar to the working condition of roadbed and easy to be analyzed, the paper puts emphasis on inundation collapsible loess foundation widespread in the west of China, on common soft soil foundation which is intense to the settlement, on compacted loess embankment and has profound research. The calculating of moistening process and collapse settlement stand out in the research of loess's collapse deformation, the variation of load and soil parameters along with time in the consolidation of saturated soft soil, the Theologicalcharacteristic and simple and practical calculating method of unsaturated soil in the settlement of embankment.Combined with actual project, a great deal of observations and tests are carried out about the process of settlement of saturated soft soil foundation and loess fill embankment, disclosing many laws about the settlement and deformation of highway embankment, and many laboratory soil tests of the soil sample have been done. Combined with theoretical analysis, the paper puts forward new calculating method about the process of settlement of saturated soft soil foundation with the variation of load and soil parameters, calculating method about the process of settlement of compacted loess embankment, calculating method about loess moistening process and collapse settlement of loess foundation. All these calculating methods are compared to the data of prototype measurement. It is testified that the methods have determinate reliability and important practicability. At the same time, the paper develops K0-K10 percolation consolidation equipment and measuring a...