小净距重叠盾构隧道施工工序研究

Study on Construction Process for Small Clear Distance Overlapping Shield Tunnel

以昆明地铁2号线环城南路站-昆明火车站区间(简称环昆区间)施工为例,采用数值分析方法研究“先下后上”和“先上后下”施工顺序对控制地表沉降的差异。结果表明:“先下后上”施工,下洞施工引起的地表沉降量值占总沉降量的82.6%,上洞施工引起的附加沉降量约占总沉降量的17.3%;“先上后下”施工,上洞施工引起的地表沉降量值占总沉降量的18.8%,下洞施工引起的附加沉降量约占总沉降量的81.1%;“先下后上”施工,上洞施工对下洞施工的影响为沉降槽曲线被“压扁拉长”;“先上后下”施工,下洞施工后,地表最大沉降急速增大,沉降槽呈深“V”形。开挖面支护压力主要影响最终沉降量值,盾尾注浆压力则影响沉降曲线的形态及最终量值;从计算结果看,开挖面支护压力比对沉降控制的敏感性更高。根据相关规范控制要求,本工程重叠隧道施工时开挖面支护压力比及注浆压力比范围在0.8~1.2区间较为合理。

Taking the construction of the section between Huanchengnan Road Station to Kunming Railway Station on Kunming Metro Line 2 as an example,the numerical calculation method is used to study the difference between the construction sequence of′first down and then up′and′first up and then down′on the control of surface settlement.The results show that during the′first down and then up′construction,the surface settlement caused by the construction of the lower tunnel accounts for 82.6%of the total settlement,while the additional settlement caused by the construction of the upper tunnel accounts for about 17.3%of the total settlement;during the′first up and then down′construction,the surface settlement caused by the construction of the upper tunnel accounts for 18.8%of the total settlement,while the additional settlement caused by the construction of the lower tunnel accounts for approximately 81.1%of the total settlement.During the′first down and then up′construction,the construction of the upper tunnel has an impact on the construction of the lower tunnel,as the settlement trough curve is flattened and elongated;during the′first up and then down′construction,after the construction of the lower tunnel,the maximum surface settlement rapidly increases,and the settlement trough forms a deep“V”shape.The excavation face support pressure ratio mainly affects the final settlement value,while the shield tail grouting pressure affects the shape of the settlement curve and the final settlement value.From the calculation results,it can be seen that the sensitivity of excavation support pressure to settlement control is higher.According to relevant regulatory control requirements,the recommended range for excavation face support pressure ratio and grouting pressure ratio during construction in this project is 0.8~1.2.