Study On Post-construction Settlement Control Of Loess High Fill In Mountainous Area

Loess high fill projects in mountainous area are increasing in recent years,and construction scale is getting larger and larger.The post-construction settlement,which is an engineering problem that requires timely research,has received extensive attention.In order to effectively control the settlement,this paper studies the settlement problem in four aspects: a summary of settlement laws,influence factors analysis,settlement calculation and construction control.The research methods are: data analysis,finite element simulation,formula derivation and case analysis.Research results are as follows:(1)The settlement laws of loess high fill project in mountain area can be described as: The rate of ground surface settlement is faster in early period after completion and becomes more stable with time.The relation curve between ground surface settlement and time varies approximately in the form of logarithmic function.The cumulative settlement of the project increases with the construction process of the fill,and the settlement rate is larger in the construction period.The settlement ratio of the ground base and the filling body is basically stable at later stage and completion stage of construction.The characteristics of the ground base and the fill height are the main factors that affect the development of the settlement.The greater the fill height is,the weaker the ground base is and the greater the settlement will be.(2)Analysis of influence factors of settlement was carried out by finite element analysis software ABAQUS.Analysis results show that increasing deformation modulus and permeability coefficient of ground base and initial compaction degree of filling soil,as well as decreasing differences in soil layers of ground base,initial water content of filling soil and filling speed both help to reduce settlement.The greater the slope inclination of the mountain is,the smaller the settlement is,but the greater the uneven settlement is.(3)A method for calculating the compression of the filling body of the high fill project is proposed.A compacted loess compression model was created by considering the deformation characteristics of compacted loess.A simplified formula for the calculation method was derived by the compression model.The feasibility of the proposed method is verified by the comparison between the monitoring data and the calculation results of actual projects.Moreover,the prediction methods of post-construction settlement and time-dependent deformation were put forward.The settlement of a certain section of the actual project was calculated by different methods.The calculation results are available for engineering reference.(4)Taking a loess high fill project in Northern Shaanxi Province as the background,the key construction processes control were studied based on settlement control.First,the construction methods were analyzed.The field tests results show that both the dynamic replacement method and the deep underwater tamping method can be used for silt dam treatment.Second,a systematic control scheme,which includes control targets,control indicators,evaluation indicators,and control technologies for foundation treatment and filling construction,was established.Then,the construction parameters of different construction methods in filling construction were studied by case summary,and the reference parameters for the case in this paper were provided.Finally,some suggestions were given as: the dynamic compaction method is proposed for the construction of the top of the filling body;the cut area should be developed firstly,and the new fill foundation should be developed after the settlement is stable.