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首页> 外文会议>Rock Mechanics in the National Interest >Evaluation, monitoring and design concepts for pre-cast concrete segmental primary support under high hydrostatic pressures
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Evaluation, monitoring and design concepts for pre-cast concrete segmental primary support under high hydrostatic pressures

机译：高静水压力下预制混凝土分段主要支护的评估，监测和设计概念

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Reduction of water inflows into the City Creek Segment of Inland Feeder Arrowhead East Tunnel by grouting resulted in the buildup of hydrostatic pressures behind an existing pre-cast concrete primary support system designed only for ground loads. The maximum pre-construction groundwater head along the approximately 2,440 meter long TBM driven tunnel exceeds 335 meters. The pre-cast concrete segmental primary support system was designed as an unsealed (non-gasketed, non-bolted) system. The segments were expanded against the excavated tunnel surface to provide immediate ground support behind the TBM. Reducing water inflows into the tunnel required sealing of the pre-cast concrete segmental primary support to the extent possible through various and extensive grouting techniques. The resulting buildup of hydrostatic pressures behind the concrete segments initiated the evaluation of the design of the installed primary support to carry additional hydrostatic loads. Design changes of the pre-cast concrete primary support system to carry the added hydrostatic heads and allow continuation of the tunnel drive were also considered. The design changes are applicable for the segments to carry a maximum hydrostatic head of 244 meters with excess water head to be relieved as needed. The design changes for the segments had to be compatible with the Contractors existing TBM segment erection system. Additionally, a ground water monitoring program was developed to assure the buildup of hydrostatic pressures did not exceed the load carrying capacity of the already installed primary support system and compromise the safety of the tunnel. The monitoring program included installing piezometers to monitor buildup of hydrostatic head behind the primary support, and a water relief system to limit the hydrostatic head buildup. The program also used formation grouting behind the installed segments to reduce the permeability of the rock immediately behind the segments and for a given distance beyond the excavation limits within the rock mass. The formation grouting effort in turn limited the hydrostatic head buildup behind the segments and reduced the water inflows through the pressure relief valves. This paper discusses the evaluation of the Contractor designed primary support system, the ground-water-monitoring program and suggested design concepts for pre-cast concrete segments under high hydrostatic pressures.
机译：通过灌浆减少流入内陆支线箭头东隧道城市小溪部分的水流入量，导致现有的仅用于地面荷载的预制混凝土主要支撑系统的静水压力增大。沿约2,440米长的TBM掘进隧道的最大施工前地下水头超过335米。预制混凝土分段主要支撑系统设计为非密封（非垫片，非螺栓连接）系统。这些部分靠着开挖的隧道表面扩展，以便在TBM后立即提供地面支撑。为减少流入隧道的水量，需要通过各种灌浆技术将预制混凝土分段主要支座进行密封。由此产生的混凝土段后面静水压力的积累开始了对已安装的主要支撑物的设计评估，以承载额外的静水载荷。还考虑了预制混凝土主要支撑系统的设计变更，以承载增加的静水压头并允许继续进行隧道驱动。设计变更适用于最大承载244米的静水压头的节段，并根据需要减轻多余的水压头。路段的设计变更必须与承包商现有的TBM路段安装系统兼容。此外，制定了地下水监测计划，以确保静水压力的累积不超过已经安装的主要支撑系统的承载能力，并损害隧道的安全性。监控程序包括安装压力计以监控静压头在主要支撑物后面的堆积，以及一个泄水系统以限制静压头的堆积。该程序还使用了在已安装段后面的地层注浆，以降低紧接在段后面的岩石的渗透性，并降低给定距离，超出岩体内部的挖掘极限。地层注浆工作反过来限制了静水压头在节段后面的堆积，并减少了通过泄压阀的水流入量。本文讨论了承包商设计的主要支撑系统的评估，地下水监测计划以及在高静水压力下预制混凝土段的建议设计概念。

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