摘要
黄土地层中采用暗挖法施工地铁车站难度大、风险高.以西安某暗挖地铁车站为对象,介绍洞桩法地铁车站导洞设计、下导洞加固及洞桩法设计方案,并基于数值模拟方法对比分析不同导洞开挖顺序和下导洞加固方案下地表沉降规律.研究表明:暗挖法施工横向影响范围为车站中心向外1.5 倍车站跨度;导洞开挖及洞内施工引起的地表沉降量约占总沉降的3/4;两种导洞开挖顺序中,先上后下顺序地表沉降稍小于先下后上顺序;下导洞底部加固对车站上方地表沉降影响较小,但对底部隆起控制有利.
Abstract
Construction of subway station with underground excavation method in loess strata is difficult and risky.Based on one subway station constructed by underground excavation method in Xi'an,this article introduces the design of subway station pilot tunnels using PBA approach,the reinforcement of lower guide tunnels,and the design scheme of PBA approach.And based on numerical simulation methods,the article compares and analyzes the surface settlement laws under different excavation sequences of pilot tunnels and lower pilot tunnels'reinforcement schemes.Some conclusions have been drawn.Firstly,the horizontal influence range is 1.5 times of the station span from the station center.Secondly,the surface settlement caused by pilot tunnels excavation and structure construction inside the pilot tunnels accounts for about 3/4 of the total settlement.Thirdly,for two pilot tunnels excavation sequences,the surface subsidence of top to bottom sequence is slightly smaller than that of bottom to top sequence.Finally,the reinforcement of the bottom of lower pilot tunnel has a small impact on the surface subsidence,but it is beneficial for controlling the bottom uplift.
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