A wide variety of instrumentation was deployed during construction of the sprayed concrete lined tunnels at Heathrow Express Terminal 4 station in the mid-1990s, some of which is still functioning and is accessible for the taking of readings today. This paper presents a nearly 20-year history of stress in the primary lining of the concourse tunnel measured using radial and tangential pressure cells on and in the sprayed concrete. Data from tangential pressure cells require careful interpretation and the new and complete methodology for achieving reliable results described in previous work by the authors was used to provide the stress history from construction into the long term. This is a unique case study in terms of both the detail and interpretation of the measurements and the time period over which measurements have been taken. The results show that pressure cells are very sensitive and respond to changes in stress due to nearby construction activities and also that, after construction has ceased, stresses stabilise at a value well below the full overburden pressure (the vertical total stress at tunnel axis level).

中文翻译：

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希思罗机场 4 号航站楼喷射混凝土隧道衬砌的应力

20 世纪 90 年代中期，希思罗机场快线 4 号航站楼车站的喷射混凝土衬砌隧道施工过程中部署了多种仪器，其中一些仪器至今仍在运行，可供读取读数。本文介绍了使用喷射混凝土上和内部的径向和切向压力传感器测量的大厅隧道主衬砌应力近 20 年的历史。来自切向压力单元的数据需要仔细解释，并且作者使用了作者之前的工作中描述的新的、完整的方法来获得可靠的结果，以提供从施工到长期的应力历史记录。就测量的细节和解释以及测量的时间段而言，这是一个独特的案例研究。结果表明，压力传感器非常敏感，可以对附近施工活动引起的应力变化做出反应，而且施工停止后，应力稳定在远低于全覆盖压力（隧道轴线水平处的垂直总应力）的值。