Study On Construction Risk Assessment Of Newly-built Railway Under Bridges With Existing High-speed Railways

In recent years,new breakthroughs and achievements in the field of railway construction has made in China.By the end of 2017,the total operating mileage of railways nationwide has reached 127,000 km,including 25,000 km of high-speed railways,ranking first in the world,and improving the traffic network gradually.With the continuous increase in the density of railway networks,there are more and more cross-passages between the same modes of transportation.Such projects are more complex and special than ordinary railway construction projects.The construction of a new railway below the existing high-speed railway bridge must ensure both the stable operation of the existing high-speed railway and the quality and safety of the construction.Therefore,it is of great theoretical value and practical to carry out the construction risk evaluation of the new railway under the existing high speed railway bridge.On the basis of researching relevant literature,combined with on-site investigation and expert consultation,this paper applies fuzzy mathematics to quantify the risk of construction of new railways passing through existing high-speed railway bridges,establishes a risk assessment model,and provides risk assessment for similar projects.And relying on the Shanghai-Nantong Railway under the Beijing-Shanghai high-speed rail and Shanghai-Nanjing intercity railway as its basis,the appraisal and application of the risk of underpassing the existing highway bridge construction,The main research content is as follows:1.Combined with the existing research results,through the analysis of the information provided by the expert consultation,the main risk factors for the construction of the new railway under the existing high-speed railway bridges were identified.In accordance with the principle of establishment of a risk assessment index system,a construction risk assessment index system for a newly constructed railway underneath an existing high speed railway bridge will be constructed.2.Combining with relevant risk assessment and management specifications for railway construction,the general process of construction risk assessment for newly built railways under bridges with existing high-speed railways is proposed,and the evaluation criteria for each index in the construction risk assessment system for newly built railways that pass through existing high-speed railway bridges A preliminary division is made and the risk rating standard adopted for the construction risk evaluation of new railways passing through existing high-speed railway bridges is given.3.By referring to a large number of domestic and foreign literatures on risk assessment methods,combined with the construction characteristics of the new railway underneath the existing high-speed railway bridge construction,a fuzzy comprehensive assessment method was adopted to establish a risk assessment model for the underpass bridge subgrade engineering of existing high-speed railways.Taking the Shanghai-Nantong Railway project as an example,the risk assessment model for underpassing existing high-speed railway bridges is applied.4.From the three aspects of safety,quality and environmental protection,the risk control measures for the construction of bridges under the existing high-speed railways are given.Taking into account the impact of underpass bridge construction of existing high-speed railways on existing railway bridges,taking Shanghai-Nantong Railway as an example,real-time monitoring of the settlement of existing bridge piers was conducted,and monitoring plans and specific measures were given.