Safety risk assessment of adjacent bridges induced by shield construction
To address the problems such as imperfect and distorted safety risk assessment results of adjacent bridges induced by subway shield construction,a safety risk assessment method for adjacent bridges induced by shield tunneling based on variable weight extension cloud model was proposed.First of all,based on literature review and practical experience,a safety accident mechanism model of adjacent bridges induced by shield construction was established.Then,three level 1 indicators are defined including maternity environment,risk causing factor and risk bearing body were adopted.The safety risk evaluation indicator system of adjacent bridges induced by shield construction was established based on 7 second-level indicators,including geotechnical physical performance parameters,tunnel engineering conditions,shield construction conditions,shield construction parameters,construction management risks,bridge status and bridge conditions,and 27 third-level indicators,including internal friction angle and elastic modulus.Secondly,the evaluation index weight was obtained by the improved objective weighting method of CRITIC.The variable weight extension cloud model was used to construct the safety risk assessment model of adjacent bridges induced by shield construction.The variable weight theory was introduced to obtain a more scientific and reasonable change weight for the evaluation results.Finally,an example analysis was conducted on the bridges along the phase Ⅱ section of the first phase of the rail transit Line 1 in a city,the results show that the safety risk levels of the bridges near the four shield construction were Ⅲ,Ⅱ,Ⅱ,Ⅰ.Among them,the construction site such as soil index,tunnel overburden ratio,tunnel buried depth,tunnel diameter and the relative position of bridge pile and tunnel were main risk factors.That is,it was necessary to focus on monitoring the bridge itself and the construction site environment and strictly implement technical measures such as surrounding soil reinforcement during the shield construction of this section of tunnel.The research results can provide scientific and effective reference for prevention and control of safety risk in adjacent bridges induced by shield construction.
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