Research On Settlement Characteristics Of Loess High Fill Foundation

With the development of China's economy,a large number of high fill projects have appeared in the loess area.These projects can expand urban construction land and speed up infrastructure construction.However,large-scale mountain-cutting and earth-shaping bring many high fill engineering problems.The settlement and deformation of fill make some hazards very obvious,such as the post-construction settlement of the super-large fillings,uneven settlement,and even instability of the super-large fillings formed by filling.The potential hidden dangers of many completed fill engineering have gradually emerged in recent years.In order to explore the settlement law of loess high fill foundation,this paper has carried out a relatively comprehensive related research through laboratory tests and numerical simulation,and has provided some reference basis for such engineering problems.Through one-dimensional consolidation test,the creep law of compacted loess under different moisture content,different compactness and different loads is studied;time required for compacted loess to reach settlement stability is analyzed;different models are adopted to fit the strain-time relationship of compacted loess.Then,through indoor model tests,laws of settlement and the variation of earth pressure of fill under two working conditions of one-time loading and graded loading are studied;and microscopic indexes such as pore change in settlement process of are quantified and analyzed by using image J software.The parameters obtained from the above tests are used to simulate the settlement of loess during construction and the settlement after construction;the variation law of settlement after construction with water content,compactness,and fill height is analyzed.Finally,the influencing factors of high fill settlement are analyzed and corresponding control measures are put forward.The result shows that the one-dimensional consolidation curve of compacted loess roughly presents three stages of initial deformation,deformation mitigation and steady deformation.When the initial state is identical,with the increase of load,the time required for the deformation of compacted loess soil to reach stability will correspondingly increase.Burgers can well reflect the relationship between the one-dimensional consolidation deformation of soil under various loads and time,and it is suitable for being used as a creep deformation model of compacted loess soil.The settlement of the fill soil shows the same “three-stage” rule under the two working conditions of one-time loading and graded loading.The settlement of the fill soil under one-time loading is larger than that under graded loading.However,the stabilization time under graded loading is longer.With the increase of age,the arrangement of soil particles gradually tends to be close.The pores of soil sample are mainly embedded pores,and the structure of soil is closer.During the construction period of high fill,the settlement at the center is large,while the settlement at both sides is small,and it is evenly distributed symmetrically in the middle axis.In a certain range,reducing the water content,increasing the compaction degree and reducing the fill height can reduce the post-construction settlement of loess high fill foundation.