盾构隧道拓建地铁车站施工力学特性分析

An Analysis of the Mechanical Characteristics of the Construction of Expanding a Metro Station with a Shield-Drilled Tunnel

随着城市轨道交通的快速发展及城市环境的制约,普通暗挖法在地铁车站施工中所受的局限越来越大,结合国内外工程案例,提出双洞盾构区间隧道拓建地铁车站的方案,可为以后利用盾构隧道扩挖车站或在盾构区间内增设车站提供借鉴。采用数值模拟对既有盾构隧道拓建地铁车站的方案进行分析,重点研究拓建施工过程中既有盾构隧道的位移和应力变化规律:盾构最大主应力沿整个隧道纵向呈"W"型分布,且土体开挖对纵向一定范围内的最大主应力影响较大,而对范围外的最大主应力影响较小,该影响范围的纵向长度是固定的,为19.5 m。前3次土体开挖对盾构隧道的最大、最小主应力影响较大,而剩余部分土体开挖对盾构隧道的最大、最小主应力影响较小。研究结果表明:利用盾构区间隧道拓建地铁车站的方案是可行的,且由于国内盾构6 m直径较为普遍,施工经验也较丰富,因此有较大推广价值。

With the rapid development of urban rail transit and the constraints of the urban environment,the application of the commonly used undercutting method gets more and more restricted to the construction of metro stations.Upon the basis of analyzing quite a few practical engineering cases both at home and abroad,put forward in the present paper is a new scheme of expanding a metro station in a double-tunnel shield-drilled section,which may serve as a useful reference for expanding a metro station with a shield-drilled tunnel or adding a metro station to a shield-drilled section.The numerical simulation is applied to analyzing the existing scheme of expanding a metro station with a shield-drilled tunnel,with stress placed on the study of the laws of the change in both displacement and stress of the existing shield-drilled tunnel during the expanding construction.The maximum main stress of the shield is longitudinally distributed along the whole tunnel in the shape of W,and the excavation of the soil body has a comparatively great effect on the maximum main stress longitudinally within a certain range,but has relatively little effect on the maximum main stress beyond a certain range.Besides,the longitudinal length of the affected range is fixed,namely,19.5 m.The first three excavations of the soil body have a greater influence on the maximum and minimum principal stresses of the shield-drilled tunnel while the excavation of the remaining soil bodies has relatively little influence of the maximum and minimum principal stresses.The results of our studies show that the scheme of expanding a metro station with a shield-drilled tunnel is feasible.Besides,the diameter of the shields commonly used in our country is generally 6 m,and we are rich in construction experience,the scheme dealt with here is of much value in popularization.