| Compaction is one of the most important links in the construction of highway filling subgrade,and the quality of compaction directly determines whether the road has sufficient strength,stability and bearing capacity,and the clear dynamic response characteristics in the compaction process is an important basis for judging the nature of road filler and compaction effect.The soil formation process determines its natural spatial variability,in addition,in the process of transportation,paving,landfill,etc.will cause spatial differences in the nature of the fill,while the construction process will also be affected by the natural climate,these comprehensive factors will lead to spatial differences in the compaction condition of the subgrade and thus cause spatial variability of material parameters.Therefore,it is necessary and reasonable to consider the spatial variability of soil properties in the dynamic response analysis,but few existing compaction dynamic response studies have considered this point,and further research and exploration are needed.Based on this,this thesis is based on the Nanning-Bobai-Nabu section of expressway project,and based on the preliminary research,the section of K119+980-K120+000 high-fill subgrade is selected as the research object,and the spatial variation characteristics of soil properties are quantified by introducing the random field theory,and the dynamic response characteristics of granite residual soil roadbed during vibration compaction are studied by using a combination of indoor test and numerical simulation.The main research contents are as follows:(1)Through field research and design data,the engineering profile and engineering geological conditions of K119+880-K120+080 high-fill subgrade section were summarized.The water content,liquid-plastic limit and compaction tests were carried out on granite residual soil samples to obtain the basic physical and mechanical indexes;triaxial consolidation without drainage tests were carried out at four different compaction levels to obtain the shear strength parameters and stress-strain characteristics of granite residual soil at different compaction levels.(2)The basic theory and discrete method of random field are described.The secondary development of ABAQUS and FLAC3 D using Python language was carried out,and the bulk stochastic finite element and stochastic finite difference analysis were implemented in the two software respectively.The analysis of two-dimensional subgrade slope stability was carried out by two practice paths,and the operation process and computational efficiency of the two methods were compared to provide a preferred solution for the subsequent dynamic response analysis.(3)The roller load is simplified to a semi-elliptical load,and the DLOAD subroutine is used to realize the application of semi-elliptical moving vibration load.Based on the indoor test results,the spatial variability of cohesion,internal friction angle and elastic modulus is considered,and the lognormal random field is constructed by Python,and the granite with the spatial variability characteristics of parameters considered under the semi-elliptical vibration load is analyzed by ABAQUS.The dynamic response of the cross section and longitudinal section of the residual soil subgrade under the semi-elliptical vibration load was analyzed by ABAQUS.The results show that: the dynamic response characteristics of the subgrades solved under the same random field statistical parameters have large differences,and the spatial distribution characteristics of the materials significantly affect the dynamic response characteristics within the subgrades;the mean values of vertical dynamic displacement and plastic deformation solved by considering the spatial variation characteristics of the materials are larger than those solved by deterministic analysis;the evaluation of the compaction effect of the subgrades using the results solved by deterministic analysis may cause The spatial variability of the parameters is necessary and reasonable to be considered in the dynamic response analysis of the subgrade.(4)Parameter sensitivity analysis was performed on the statistical parameters of the random field to study the effect of random field parameters on the compaction effect of the subgrade.The results show that:the vertical correlation distance of cohesion and internal friction angle,the vertical correlation distance of elastic modulus,the correlation coefficient of cohesion and internal friction angle,the coefficient of variation of cohesion,internal friction angle and elastic modulus all affect the compaction effect of subgrade,the plastic deformation increases with the increase of vertical correlation distance of cohesion and internal friction angle,decreases and then increases with the increase of vertical correlation distance of elastic modulus,increases with the increase of cohesion and internal friction angle,and decreases and then increases with the increase of coefficient of variation of cohesion and internal friction angle.The coefficient of variation of cohesion and modulus of elasticity decreases and then increases with the increase of cohesion and internal friction angle,and increases with the increase of variation of internal friction angle.(5)Sensitivity analysis of the roller load was carried out to study the influence of load parameters on the compaction effect and to design an orthogonal test to select the compaction scheme.The results show that: the vibration frequency has the most significant effect on the compaction effect of the subgrade,the amplitude of the excitation force is more significant,and the vibration wheel weight has the least effect on the compaction effect.Under the conditions of the given range of roller parameters,grid division,material parameters,and load form,the best compaction effect of granite residual soil subgrade is achieved when the vibration frequency is 35 Hz,the amplitude of the excitation force is 400 k N,and the vibrating wheel weight is 90 k N. |
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