Reasearch On The Influence And Evaluation Of Metro Construction On Municipal Bridge Pile Foundation In Beijing

The construction of Beijing subway is currently during the peak period,the total mileage of Beijing subway will be over 700 km of 2015.To alleviate downtown traffic congestion,miles of the subway were needed within the city.Most of the high-rise buildings and bridges were supported with pile foundation in the urban city.Due to the busyness of underground space,sometimes subway lines inevitably pass through the bottom of the piles and the sideways of the piles.Starting from the view of the degree of nearness,the Beijing Metro Line 4 was studied,the study include the soil movement induced by the construction of the subway station and tunnel,and the pile horizontal displacement and moment due to this soil movement.The impacts of the construction of subway foundation pit and tunnel on the nearby piles were studied,and the characteristics of how did many factors impact the nearby piles were studied.Basing on the study of the impact of the pile horizontal displacement and pile moment to the structure of the bridge,the modified evaluation system of the bridge was established.According to the study,the conclusions are as follows:(1)The discriminant of subway project's proximity to the abutment Put forward the concept of proximity,the use of the basic idea of fuzzy comprehensive evaluation to determine the location,distance,depth and structural importance as a research subway construction on adjacent pile foundation of the main factors.Proposed adjacent partition indexing criteria for the study of subway construction on adjacent bridge pile foundation analysis to determine the impact analysis proposed evaluation criteria.(2)Field study of metro construction impacts on neighboring bridge foundation Shield Zone in Beijing subway across the adjacent existing bridge foundation works as the basis for a nearby bridge piles and surface subsidence monitoring tests,the proposed settlement control indicators to monitor the object,the bridge piers to focus on monitoring data analysis.Established through the adjacent bridge piles Shield numerical model,and for the settlement of the pile,the pile lateral displacement and surrounding soil subsidence three indicators,the numerical results with the actual monitoring data for mutual authentication.(3)The parameter analysis of the subway foundation pit on the nearby pile foundation of bridge.FLAC3D numerical model considering the soil-pile interaction were established to study the impact of the construction of foundation pit on the nearby pile foundation of bridge.The parameters of the depth of the foundation pit,the distance from the pile to the foundation pit,the length of pile outside the foundation pit,the restriction of the pile top,the soil parameters and the interface parameter were analyzed in the numerical models.(4)The parameter analysis of the subway tunnel on the nearby pile foundation of bridge.The impact of subway tunnel construction on the adjacent bridge piles was study using numerical analysis.The parameters analyzed in the numerical analysis include soil thickNess above the tunnel,the tunnel and the pile spacing,pile length;the release of stress ratio of the excavation of tunnel,the force reacted on top of the pile,soil parameters,soil parameters and the interface parameter.(5)Starting from the normal method of the degree of nearness evaluation of the piles to the subway construction,the case of the Beijing subway 6 going through under the jingguang bridge was selected,and the method established in this paper was used to evaluate the degree of nearness of the piles to the subway construction,and finally the modified evaluation system was established of the degree of nearness of the piles foundation to the subway construction.