Risk Control Research Of Metro Station Constructed By PBA Method Closely Beneath Existing Station

With the large-scale construction of subway engineering and the complete of the urban rail transit network, new subway engineerings crossing the reserve range of existing subway arise increasingly. PBA method is developed by traditional shallow tunneling method and cover-excavation method, which is the organic combination of pilot tunnel excavation, hole digging pile construction, arch construction. The construction of subway station closely crossing the existed station by PBA method will generate multi-tunnel effect and disturb surrounding rocks, which will result in the deformation of subway structure and track irregularities. In order to ensure the safety of the subway structure and operation safety in the process of crossing construction, it is necessary to analyze the settlement of existing metro structure regularity and dynamic performance index to sdudy the corresponding risk control measures.Paper study the multi-cavity effect and influence law of existing structures and vehicle dynamic performance index and technical measures of risk control, through numerical simulation and vehicle-track coupling dynamic analysis technique based on a PBA method subway station closely crossing the existing station in Beijing. The main work and research results are:1. Through reviewing literature and collecting some related design information, the characteristics of PBA method is summarized and the main factors affecting the safety of the subway structure is analyzed in the crossing construction.2. The multi-cavity effect is studyed through numerical simulation. After separately analyzing the multi-cavity effect of single and double hole,the"lower-upper,edge-central" is recommended by introducting the AHP.3. By studying the whole crossing process of new constructed station, the influence law of existed structures crossed by new constructed station is concluded, which the construction of cross aisle and lower and upper pilot tunnel affects mostly to existed station. It is concluded that the excavation of channel and pilot accounted for 70% of the total settlement and excavation remainder of station accounts for 30% of the total settlement.4. The safety and stability index of the vehicle is analyzed based on multi-body dynamics theory. After the comparison and analysis, results show that although these indicators meet the specification requirements, the stability evaluation index level declines larger than security evaluation level, which indicates that more comfort impact than security impact.5. The risk grade of this tunnelling engineering is classified as "special grade" and risk control measures such as pre-grouting reinforcement and monitoring and rail protective measures and control by stages is studied.