Research On Nondestructive Testing Of Subgrade Filling Quality And Settlement Deformation Monitoring In Expressway Reconstruction And Expansion

At present,China’s regional and urban trunk line network has been basically formed,and the demand for new expressway construction has become flat.With the rapid development of economy and the increase of the number of vehicles,the situation of traffic saturation and insufficient transportation capacity appears.In order to solve this problem,the proportion of highway reconstruction and expansion in highway construction is gradually increasing.In the reconstruction and expansion of expressways,the differential settlement of new and old subgrade has always been a difficult engineering problem.In order to ensure the normal operation and service life of expressway,it is necessary to carry out filling quality detection and long-term settlement monitoring for the widening area of new and old subgrade.Therefore,it has important theoretical and practical application value to systematically carry out the research on nondestructive testing and settlement deformation monitoring of subgrade filling quality in expressway reconstruction and expansion.Based on the innovation project of Shandong Provincial Economic and Information Commission,this paper studies the dynamic compaction and differential settlement control technology in the widening area of new and old expressway subgrade.Combined with the reconstruction and extension project of Beijing Taiwan expressway,this paper analyzes the common diseases and the mechanism of the diseases in the reconstruction and extension project of expressway,and makes a comparative study on the treatment technology of the subgrade widening area commonly used in China.According to the general situation of reconstruction and expansion project,based on the basic principle of transient Rayleigh wave method,Rayleigh wave is used to carry out non-destructive rapid detection of subgrade filling quality,to determine the fitting formula and reliability of the formula of subgrade wave velocity and compactness in the widening area under different depths,and to verify the accuracy of Rayleigh wave method in inverse calculation of compactness by combining with the compactness measured by field sand filling method,so as to obtain the actual effect of Subgrade Compaction in the widening area Finally,the evaluation of subgrade filling uniformity was carried out.Based on the traditional settlement observation and analysis of precision level,the whole section settlement of subgrade surface in three test areas is scanned by 3D laser scanner.The difference between traditional observation method and 3D laser scanning method is analyzed.The applicability of 3D laser scanning technology in subgrade settlement monitoring is evaluated.Through traditional precision level and new type three-dimensional three-dimensional leveling instrument Two monitoring methods of dimension laser scanning are used to realize the point,line and surface integration in subgrade settlement observation.The numerical analysis model is established.Considering the influence of different design parameters(the number of geogrid layers,slope and width of the joint)on the subgrade,the maximum location change of settlement value,the settlement change of the contact surface of the new and old subgrade,the settlement change of the horizontal surface of the new and old subgrade toe are analyzed,and the law of subgrade settlement before and after the variable change is revealed.The main conclusions are as follows:(1)After the field test according to the test scheme,the subgrade filling uniformity of new subgrade,old subgrade and widened Subgrade along the driving direction and perpendicular to the driving direction is analyzed.The filling conditions of new subgrade,old subgrade and widened subgrade have little difference,the wave speed range is consistent,and the overall filling of subgrade is uniform.(2)Through the dry density and Rayleigh wave velocity values of 13 measuring points at the subgrade depth of 0.4m,1.5m,2M and 2.5m,the fitting formula of Rayleigh wave velocity and dry density at different depths is established,and the compactness at different subgrade depths is calculated by using Rayleigh wave velocity,and the compactness meets the standard.Rayleigh wave method is fast and less workload,which can be applied to large-scale soil compaction detection.(3)In this experiment,the change of leveling monitoring points is very small.The data processing and analysis of point cloud scanned by 3D laser scanner in this experiment show that the results are basically consistent with the results obtained by traditional leveling monitoring methods.The settlement of point cloud superposition and leveling monitoring is less than the specified value The application of point,line and surface integration in subgrade settlement observation is realized by two monitoring methods of 3D laser scanning,which are interdisciplinary.(4)In this paper,the finite element software is used to establish the model,and seven kinds of working conditions are simulated by controlling three variables of geogrid layers,slope and width.The influence and law of different design parameters on subgrade settlement are analyzed.The research results of this paper can provide some reference for solving the problems of nondestructive testing and deformation monitoring of subgrade filling quality in expressway reconstruction and expansion.