Analysis And Engineering Application Of Differential Settlement Between Old And New Roadbed Widening Projects

Due to the increasing demand for traffic flow,many road carrying capacity can no longer meet the requirements.Therefore,it is an effective solution to widening and renovating the original roadbed.Due to the differences caused by the bearing history and construction of new and old roadbeds,it is easy to form large differences in the operation process.Therefore,the treatment of the overlapping sections of new and old roadbeds has become a key issue in the success of construction projects.This paper combines the example of the highway reconstruction project of LianZhu in Hunan Province.The characteristics and mechanism of the deformation of the roadbed with widened roads are analyzed by numerical simulation.The factors affecting the deformation characteristics of the old and new roadbeds are discussed.Then,the effect and mechanism of the treatment method of the new and old roadbed overlap geospatial compartments are analyzed,and the results of the specific optimization parameters are given.Finally,based on the research results of the previous chapter,the disposal plan of the geocell is given.The main contents and conclusions are as follows:(1)Summarize the research status of widening subgrade differential settlement at home and abroad.Combining relevant knowledge of soil mechanics and elastic mechanics,we attempted to use theoretical deduction to analyze the differential settlement of old and new embankments.The results show that the traditional calculation methods have certain limitations.The differential settlement obtained by the calculation results is smaller than the actual ones.It is necessary to use the finite element software to simulate the embedding of roadbed splicing methods,and proposes the differences used in this paper.Settlement control standards.(2)Using FEM software to establish the broadening model of roadbed,studying the overall deformation characteristics of roadbed and foundation after the widening of old roads,analyzing the deformation of new and old roadbeds and foundations in layered filling of new roadbed,and exploring the construction of new roadbeds.The settlement curve and horizontal displacement curve of the old roadbed and foundation in the process.The results show that the new embankment will cause attachment deformation of the old embankment,resulting in differential settlement of the foundation under the old and new embankments.With the widening of subgradefilling of subgrade,the differential settlement between the two gradually increased,and the lateral displacement deformation also increased.As the filling height increases,the maximum settlement point of the foundation gradually moves from the inner side of the right foot of the new subgrade to the foot of the old subgrade.The turning points of the displacement direction of the foundation gradually move to the inside as the filling height increases.The displacement of the direction also increases.(3)Numerical analysis method is used to analyze the influencing factors of the deformation of new and old roadbeds by factors such as widening method,widening height,widening width and subgrade modulus.The results show that under the premise of the same widening width,the deformation of the subgrade surface is smaller than that of the single side widening method.With the increase of roadbed height,the maximum settlement value and the maximum horizontal displacement of the subgrade surface gradually increase,and the differential subsidence and horizontal displacement of the subgrade surface will gradually increase.With the increase of widening width,the differential settlement of the old and new roadbeds will gradually increase,and the location of the maximum settlement on the subgrade will also change.The increase of subgrade compressive modulus will lead to the reduction of subgrade deformation,but the relationship between the two is not proportional.When the subgrade modulus reaches a certain level,the effect of improving subgrade modulus on subgrade deformation weakens.(4)Set up a geotexture chamber to treat the old and new roadbed models,and compare the roadbed displacement field and stress field of the old road widening project with geocells and without geocells,and discuss in depth the differences in the control of old and new roadbeds.The mechanism of action of sedimentation.The calculation results show that the vertical displacement and lateral displacement of the roadbed top surface can be effectively reduced by laying geocells at the splicing sites of the old and new roadbeds,and most of the stress differences are eliminated to reduce the average stress of the old and new roadbed top surfaces.The ability of new and old roadbeds to resist uneven settlement was enhanced,with vertical settlement decreasing by about 12%,lateral displacement decreasing by about 23%,and maximum stress difference being reduced by about 25%.Finally,the key parameters of the differential settlement of the new and old roadbeds in the geocell treatment room,such as the number of layers in the grid,the width of the reinforcement,the modulus of the reinforcement,etc.,were compared and analyzed,and then the reasonable design parameters were put forward.In the case,a three-tiered geocellroom is proposed,with a lap width of 1/2 to widen the width and a modulus of 20 GPa,which provides a reference for future similar project design.(5)Based on the results of the previous research,a treatment plan for the joint treatment of the old and new subgrade of the geocell was proposed: excavation of the slope clean soil step,laying of geocells with relevant parameters,hydraulic boring machine and heavy roller stepping surface enhancement And new roadbed.The settlement curve of subsidence monitoring confirms the feasibility of the numerical analysis model and the quality of the mosaic.The results show that the treatment plan of the geocell can effectively reduce the differential settlement of the old and new subgrade.