| Urban construction development has restricted by topography and space in the loessial hill and gully area.In order to solve the shortage of land resources in city development,most cities have carried out scientifically and unutilized orderly land resources such as low hills and gentle slopes,barren mountains and ravines,etc.,to increase the land for urban and infrastructure construction.To form construction land is by cutting mountain head,filling gully,balancing the elevation difference,building artificial small plain and filling gully.Large and thick artificial filled soil layer by filling gully and cutting ridge could lead to some geological problems such as settlement deformation and stability of the slope with high fill.In this paper,compaction characteristics,strength characteristics,deformation characteristics and wetting characteristics of the compacted loess are systematically studied based on the high fill project in the hill and gully loessial region of Lanzhou city.Aiming at settlement deformation and stability of high slope of compacted high fill loess construction site,centrifugal model test and numerical simulation were used to study the settlement deformation of the high fill loess construction site and stability of the high fill slope.The main work and conclusions are as follows:1.Taking Loess Q3 filled in the study area as the research object and considering the coupling effect of water content and compaction energy,compaction test was adopted to study the characteristics of total compaction of Loess Q3,the compaction curve model under different compaction conditions was constructed to determine the characteristic parameters of the total compaction curve.By direct shear test,triaxial test,consolidation compression test and permeation test,strength characteristics,compression deformation characteristics,consolidation characteristics,secondary consolidation characteristics and permeation and wetting characteristics of compacted loess under different water content and dry density were studied.The nonlinear characteristics of strain softening and hardening of compacted loess under different confining pressures were analyzed,the nonlinear stress-strain relationship mathematical model was constructed,the stress-strain curve of compacted loess was analyzed by normalized method,and the normalized equation of stress-strain curve was obtained.The deformation and aging characteristics of the compacted loess were analyzed by one-dimensional high-pressure lateral compression test,the mathematical models of the relation between compressive strain and vertical stress and time were constructed respectively,and the calculation method of secondary consolidation settlement of the compacted soil layer was given.2.On the basis of studying the similarity of centrifugal model test,similarity ratio between consolidation compression process and seepage process was determined.In Loess Q3in Lanzhou for filling materials,centrifugal model test of settlement of high embankment design,considering the moisture content,dry density and filling height of high fill settlement,the influence of the different moisture content and dry density,different filling height of filling body under the condition of the super gravity settlement deformation and stability time were analyzed,and the compacted loess high embankment settlement deformation and the relationship between the filling height of filling body curve,and the foundation settlement deformation and the relation curve of the time.It provided a basis for the prediction of settlement deformation and stabilization time of loess high fill.3.The calculation method of settlement deformation and long-term settlement of the in-situ foundation and the filling body of high fill were discussed.The influencing factors of settlement deformation of high fill were analyzed.Plaxis finite element software was used to simulate the settlement deformation of the free site and gully site with high fill in the compacted loess in the process of formation.The settlement and deformation of the site were calculated considering the different treatment methods of the original foundation.Considering stress correlation and nonlinear characteristics of soil modulus,soil hardening model was used to calculate the deformation of the filling site,and the results were compared with those of the ideal elastic-plastic model.Considering the influence of trench bottom width and side slope degree,the settlement deformation of high fill gully site was simulated numerically,and the influence of gully effect on settlement deformation was analyzed.4.The stability of loess high fill slope was studied by finite element strength reduction method,and the influence of factors such as fill type,fill height,slope ratio and slope foundation on the stability of high fill slope was discussed,and deformation characteristics of slope body and characteristics of potential slip surface were analyzed.Considering groundwater seepage and pre-slope storage,the influence of water on the deformation and stability of slope at the side of high fill was analyzed.5.The quality control measures for the treatment of the original foundation,the design and construction of the fill body and the design of the fill side slope in the high fill project of the compacted loess were put forward by taking the comprehensive development projects of the unused land such as gully and gully of low hill in Lanzhou as examples. |
