Research On Key Technology Of Subgrade Deformation Control For New Line Connecting To Existing High-speed Railway

China has basically formed the backbone network of ’ eight vertical and eight horizontal ’ high-speed railway.At present,the inter-city and regional railway network which is rapidly integrated with the backbone network is developing.It is inevitable to encounter a large number of new high-speed railways to introduce existing high-speed railways.The width of existing subgrade is a common form of adjacent engineering,such as improper foundation treatment and excessive filling and stacking will lead to horizontal displacement and settlement deformation of existing high-speed railway subgrade.Controlling the squeezing effect of foundation treatment process,reducing additional load and real-time monitoring of construction process are effective means to control the deformation of existing high-speed railway subgrade.Based on the new Lunan high-speed railway near the existing Beijing-Shanghai high-speed railway project,through simulation analysis,field test,engineering monitoring and other methods,this paper reveals the influence of pile group compaction effect and adjacent surcharge filling on the deformation of existing high-speed railway subgrade,puts forward the foundation treatment and load reduction filling scheme to meet the deformation control requirements of existing high-speed railway,develops a large temperature difference adaptive real-time high precision deformation monitoring system,constructs the deformation monitoring technology of existing high-speed railway subgrade,and ensures the safe operation of high-speed railway.The research results can provide technical support for the design and construction control of similar proximity projects.The main results are as follows :(1)The engineering geological conditions of Qufu east station foundation of Beijing-Shanghai high-speed railway are analyzed.The engineering characteristics of the newly-built Lunan high-speed railway near the existing Beijing-Shanghai high-speed railway are analyzed from the aspects of geological characteristics,foundation treatment disturbance,subgrade filling and surcharge,and construction safety control.It is proposed that controlling the soil compaction effect of foundation treatment process,reducing the additional load of subgrade filling and real-time and accurate monitoring of the construction process are the technical problems faced by the near project.(2)The simulation model of single pile and group pile squeezing effect is established,and the deformation distribution characteristics of soil around the pile are analyzed.The influence of group pile squeezing effect on the deformation of the existing Beijing-Shanghai high-speed railway subgrade is revealed.The effectiveness of different isolation pile schemes to control the deformation of the existing Beijing-Shanghai high-speed railway subgrade is clarified.The foundation treatment scheme of the combination of squeezing pile and isolation pile is proposed to meet the deformation control requirements of the high-speed railway subgrade.(3)The influence law of different lightweight soil subgrade load reduction schemes on the deformation of existing Beijing-Shanghai high-speed railway subgrade is revealed under the two typical foundation reinforcement methods of pile-net structure and pile-slab structure of high-speed railway contact line.The joint optimization scheme of foundation treatment and load reduction filling is proposed to meet the deformation control requirements of high-speed railway subgrade.(4)Based on the operation and maintenance requirements of high-speed railway and the construction control requirements of adjacent projects,a high-precision real-time monitoring system for subgrade settlement deformation and horizontal displacement is developed.The accuracy of settlement deformation monitoring system is ±0.2mm,and the accuracy of horizontal displacement monitoring system is ±1.0mm/30 m,which meets the requirements of subgrade deformation monitoring of high-speed railway.The monitoring technology system of subgrade deformation of Beijing-Shanghai high-speed railway is constructed,and the development and distribution law of subgrade deformation of existing Beijing-Shanghai high-speed railway in the construction process is revealed.The alarm standard of subgrade deformation of existing high-speed railway in the near project is proposed,and the influence of foundation treatment and subgrade filling and loading process on the subgrade of existing Beijing-Shanghai high-speed railway is dynamically evaluated.At the same time,the safe operation of existing Beijing-Shanghai high-speed railway and the smooth construction of South Shandong high-speed railway are ensured.