Study On Differential Settlement Regularity And Reinforcement Technology In Expressway Expansion

With the rapid development of China's economy,the transportation industry has ushered in opportunities and challenges.Although the state has continuously increased its efforts to build high-grade highways and urban roads,it is undeniable that the lower-grade roads in the road network are in traffic.With the increasing traffic volume today,it is no longer able to meet the current traffic demand.Renovation of the existing low-grade roads is the best solution to solve the highway congestion problem.As a systematic project developed in recent years,the highway renovation and expansion project has some engineering difficulties in every respect.It is still a difficult problem to control the differential settlement of the old and new roadbeds.This article relies on the Gaoqing-Guanrao Expressway section.The road section widening project has carried out in-depth research on differential settlement of old and new roadbeds.Starting from the subgrade settlement calculation theory,the factors affecting the subgrade settlement are discussed based on the characteristics of the soil pore media,and on the basis of the classic layered summation settlement method,the lateral deformation of the subgrade is introduced as a calculation variable,and the relevant lateral deformation literature is consulted.The effect of the roadbed slope on the lateral deformation of the roadbed is specifically the calculation model of the lateral deformation of the roadbed influenced by the passive earth pressure.The traditional calculation public is revised and compared through field tests.The calculated curve is consistent with the on-site monitoring settlement curve,verifying The rationality of this correction method.The lateral deformation of subgrade has a great influence on subgrade settlement.If the lateral deformation can be limited,the settlement deformation of subgrade will be greatly reduced,and the differential subsidence of new and old subgrade will be reduced.Through the new and old roadbed model tests,the reinforcement effects of geogrids,gravel piles and CFG piles,and a set of comparative tests without reinforcement were studied.The test results show that in the conventional new and old roadbed model,the differential settlement occurs on the new roadbed and the new and old roadbed overlaps are quite different.Under the ultimate load,the roadbed instability mode is the slippage of the new roadbed slope,and the new roadbed section Slippage occurs;geogrids can effectively control the lateral deformation of the new filling foundation,reducing the road surface settlement to a certain extent,and the geogrid tensile resistance also improves the stability of the new filling foundation.Under the same load conditions,the roadbed The instability is not obvious;because the gravel pile has a hole expanding phenomenon under the load,although some of the load can be transmitted to the deep part of the roadbed,but the lateral deformation of the new filling foundation is increased,the effect of controlling the road surface subsidence is not achieved,and the subgrade reinforcement The effect is poor;the CFG pile can not only transmit the pavement load to the deep part of the roadbed,but also can produce the geotechnical effect to limit the lateral deformation of the new filling foundation,which has the best effect on the reinforcement of the subgrade and the control of differential settlement.By analyzing the vertical settlement and lateral deformation of the subgrade in the model test,the influence of lateral deformation on the subgrade settlement in the theoretical analysis is verified,and the rationality of the revised calculation method is determined.The model test is limited by the test conditions and monitoring points.It is impossible to carry out further research on each working condition.In order to further study the reinforcement effects of different structures,numerical simulations of different reinforcement methods are performed.The simulation results show that the geogrid has the best reinforcement effect on the slope of the roadbed slope,and the reinforcement effect at the slope foot and the top of the slope is relatively weak.The CFG reinforcement model simulates the working conditions of the two pile lengths.The results show that the long pile can be The instability of the new filling foundation was effectively controlled and its stability was improved.The mechanism of the CFG pile was analyzed by analyzing the deformation of the pile.Numerical simulations have extracted more deformation data of different locations of the subgrade model,and have more intuitive and concrete understanding of the stress and strain laws of the subgrade model.Through numerical calculations,model tests and numerical simulations,the study investigated the differential settlements of new and old embankments in the reconstruction and expansion projects of highways,reinforced the reinforcement mechanisms and reinforcement effects of different reinforcement technologies,and supplemented and improved relevant researches in the broadening of old roadbeds.Can provide a certain reference for future highway renovation and expansion projects.