With the acceleration of urbanization and the i n-depth implementation of the "the Belt and Road" initiative,urban land is in short supply,an d building site selection is gradually expanding around the city.The strategy of "cutting mountains and filling ditches" came into being.The contradiction betwee n the large demand for construction land and the shortage of land resources is becoming incre asingly prominent.This will inevitably be accompan ied by a large number of loess high fill projects,involving high fill technology,loess collapsible settlement and post construction settlement control,high fill slope stability,ecological environment protection,and many other issues.Among them,the m ost concerned is the deformation and stability of high fill foundation settlement.The northwest region is mainly composed of thick loess,so it is particularly important to conduct deformation research on the settlement of high fill foundations in thick l oess areas.This article takes the high fill foundation of thick loess as the research object,starting from four aspects: indoor experiments,theoretical analysis,experimental verification,and finite element numerical simulation,to study the basic mech anical characteristics of thick loess and the settlement deformation law of high fill foundation in loess areas.The main work and conclusions are as follows:(1)The deformation characteristics of remold ed loess under the variation of self-weight stress and water content are summarized by the indoor confined compression humidification test,permeability test and compaction test,the relationship among collapsibility coefficient,permeability coefficient a nd compaction coefficient of compacted loess.It is found that the permeability coefficient of loess decreases rapidly at the initial stage of pressure,and then tends to be stable with the increase of stress.Under the same degree of compaction,the influ ence of water content of compacted loess on permeabi lity coefficient shows the variation law of high,middle and low on both sides,but there is no obvious relationship between water content and collapsibility coefficient,the porosity ratio of compacted l oess has a positive correlation with collapsibility coefficient.(2)Based on the idea of layered summation method,th e Gunary(stress-strain)model and secant modulus method are introduced to propose a calculation method for settlement deformation of high fill foundation in thick loess areas.The calculation method is then verified through practical engineering.The resu lts show that Gunary model can describe the nonlinear stress-strain relationship of compacted loess better than hyperbola model and power function model.The main source of settlement in loess high fill is settlement caused by construction loads.As the he ight of the fill increases,the proportion of settlement caused by changes in water content in th e total settlement gradually increases.Under the optimal moisture conte nt conditions,when the compaction degree reaches over 95% during the construction peri od,the exhaust consolidation of the soil can be completed,and the later stage of construction i s the drainage consolidation of the soil.(3)Through FLAC 3D finite element numerical simulation,the variation law of settlement during and after construction of high fill in thick loess was explored.The numerical calculation results showed that as the f illing height increased,the stress at the original ground surface also increased accordingly,and the closer it was to the bottom of the foundation,the greater the stress;The center of the foundation surface is the place with the largest settlement duri ng the construction period of high fill,with small on both sides and large in the middle,and symmetrically distributed on both sides;By reducing water content,increasing compaction,and reducing filling height,the post construction settlement of loess high fill foundation can be reduced.(4)Based on the related literature,the settlement trea tment methods of high fill foundation are summarized from Preg met hod,cushion method,dynamic compaction method and vibration rolling method.According to the treatment method,the paper summarizes the control of the original foundation settlement by usin g the dynamic compaction method and the vibration rolling method,the settlement control measures are put forward from the aspects of water content of packing compactness,rainfall influence,earthquake action and construction technology. |