棚盖暗作法PBA地铁车站沉降规律探讨

超浅埋暗挖地铁车站施工易引起地表的过大沉降,对周边环境造成不良影响,为控制施工引起的沉降和保证市政设施的安全,引入棚盖暗作法的思路并应用于PBA车站,利用顶进钢管形成棚护体系,在其支护作用进行土方开挖。以北京地铁19号线一期平安里站为工程背景,简述棚盖暗作法PBA地铁车站的特点及施工步骤,对不同施工阶段产生的沉降进行统计分析并对地表沉降槽进行拟合,由此探讨施工引起的地表沉降规律。研究表明:沉降主要发生在管幕施工及导洞开挖阶段,约占总沉降的70%。针对棚盖暗作法PBA车站的特点,对产生沉降的原因进行梳理,提出加强空洞探测及处理、缩短开挖面封闭时间、加强超前支护的棚护效果、减小管幕顶进扰动土体、合理控制群洞开挖步序等沉降控制措施。

Discussion on the Settlement Law of PBA Metro Station Based on Tubular Roof Method

The construction of ultra-shallow buried underground metro stations is likely to cause excessive settlement of the surface, which has adverse effects on the surrounding environment. In order to control the settlement caused by construction and ensure the safety of municipal facilities, the concept of tubular roof method is applied to PBA station. Roofing steel pipe is used to form a shed protection system, and the earthwork excavation is carried out under the supporting function. This paper takes the Ping'anli Station of Phase I of Beijing Metro Line No. 19 as the background of the project, briefly describes the characteristics and construction steps of the PBA metro station under roof method, analyzes the settlements generated in different construction stages, and matches the surface settlement trough. Therefore, by discussing the law of surface subsidence caused by construction, it is concluded that the settlement mainly occurs in the construction of pipe curtain and guiding tunnel, covering almost 70% of the surface subsidence. According to the characteristics of PBA station under tubular roof method, settlement control measures are proposed such as sorting out the causes of settlement, shortening the closure time of excavation, strengthening the effect of shed protection, reducing disturbance of soil in pipe curtain construction and controlling excavation sequence of group tunnels.