Dissertation > Transportation > Rail transport > Railway Line Project > Line constructed > Subgrade > Subgrade reinforcement and protection

Study on Bearing and Settlement Characteristics of Loess Foundation Reinforcement Treatment with Cement Pile Composite Foundation

Author LuoYongChun
Tutor YangYouHai
School Lanzhou Jiaotong University
Course Road and Railway Engineering
Keywords Loess Roadbed Composite Foundation Cement Soil Pile Settlement characteristics Pile Soil Stress Ratio
CLC U213.15
Type Master's thesis
Year 2013
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At present in the loess area existing railway, due to technological and economic factors,design standard is not high, especially the roadbed settlement after construction is controlledslackly. Vast majority of roadbeds are directly filled with loess, without any improvement.The pre-existing method about collapsible loess foundation treatment, determination of designparameters and the research achievements are mostly for industrial and civil engineering.Loess foundation of subgrade engineering is mostly untreated or reinforced. Once the climaticconditions and drainage conditions change, causing the engineering geology andhydrogeological conditions of loess foundation engineering to change, the engineeringproperties of loess will be changed and larger differential settlement will be produced,resulting with adverse affects to the roadbed structures. In recent years, as the generalimprovement of the standard of the new line of railway technology being built or constructedin the future in China’s railway transport, the handling problems of loess foundation withcollapsible foundation will be surely involved under construction. Therefore, in order toeliminate the collapsibility of loess, increase the subgrade bearing capacity, and ensure thatthe settlement meets the requirement after construction, further development study of bearingand settlement characteristics of the cement pile composite foundation reinforcement of loessfoundation has the important practical significance.This paper combines with the Zhengzhou-Xi’an Passenger Dedicated Line design andconstruction of major projects in the western region, to carry out the loess improved tests andthe research of loaded bearing of loess foundation and settlement deformation characteristicsof cement pile composite foundation reinforcement treatment project. According to theproperties of faced project, loess geological conditions, environmental conditions, buildingcharacteristics, superstructure and foundation design, seek indeed feasible foundationtreatment measures. And to study loaded bearing and settlement characteristics of cement pilecomposite foundation by numerical simulation. The main contents are as follows:(1) By reading the relevant literature on the characteristics of loess subgrade settlement,describe settlement characteristics of loess subgrade, analyze cement pile compositefoundation deformation and summary its bearing capacity characteristics settlement theory thecement pile composite foundation bearing capacity and theoretical calculation of settlement.(2) Through basic indoor soil test, the experimental study of the basic physicalcharacteristics of the loess is conducted. And on this basis, research characteristics test of twoimprove strength loess, wet and dry cycle test and freeze-thaw cycle test, analyze twoimproved strength characteristics of loess under different experimental conditions, andidentify the change law to provide a reference for the on-site construction. (3) With use of geotechnical mechanics numerical analysis software FLAC3D, establishthree–dimensional Moer-Coulomb constitutive model and carry out the numerical analysisof cement pile composite foundation reinforcement loess foundation.(4) The results of calculation and analysis: in the case of soil parameters unchanged,consider the influence of the size of the load, cushion modulus, cushion thickness, pile length,pile stiffness composite foundation area replacement ratio to cement pile compositefoundation bearing and settlement characteristics and propose reasonable designrecommendation.

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