Evaluation of Empirical Methods for Estimating Tunneling-Induced Ground Movements—Los Angeles Metro K Line Crenshaw/LAX Transit Project
Evaluation of Empirical Methods for Estimating Tunneling-Induced Ground Movements—Los Angeles Metro K Line Crenshaw/LAX Transit Project
复制标题
估算隧道引起的地面运动的经验方法评估——洛杉矶地铁 K 线克伦肖/洛杉矶国际机场交通项目
DOI：
10.1061/9780784484708.047
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Lemnitzer, Anne
中科院分区：
文献类型：
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作者：
Zhao, Wendi;Hashash, Youssef M.;Jasiak, Maksymilian;Lawrence, Jack;Hutter, Abby;Bernard, Timothy;Josephina Szewczyk, Alicia;Beaino, Charbel;Pearce, Michael;Lemnitzer, Anne
隧道开挖引起的地表移动的经验估算方法在隧道工程中被广泛采用。地表横向沉降曲线可用高斯曲线或修正的高斯曲线来描述，其最大沉降值和沉降槽宽度与体积损失有关。体积损失又与土壤类型、隧道几何形状和施工技术有关。基于高斯曲线和以下假设，已经开发了几个经验公式：（1）槽宽度依赖于隧道深度和地面条件;（2）体积损失依赖于地面类型和施工技术。对于土压平衡机（EPBM）隧道，过去曾假设粒状土的体积损失为0.5%，软粘土的体积损失为1%-2%，作为初步估计。然而，随着盾构（过切）间隙和衬砌周围灌浆尾部间隙的完全填充和加压，当前洛杉矶地铁隧道项目中冲积颗粒土和粘土的体积损失低于0.1%至0.2%。洛杉矶地铁K线Crenshaw/LAX公交项目于2016年至2018年进行隧道施工，为获取和组织兼容数据管理系统的数据提供了机会，并评估了针对旧冲积层中主要颗粒土的地面条件的广泛现场监测数据。这些数据允许目前的经验方法和预测EPBM隧道引起的地表沉降的相关性的改进。大约1英里（1.6公里）长，20.6英尺（6.5米）直径的双隧道是由EPBM在淤泥/粘土层覆盖的致密砂层中挖掘的。覆盖率与直径之比始终约为2。沉降和体积损失被观察到在很大程度上取决于工作面/屏蔽压力。一般来说，保持持续的压力可以显著减少沉降。提出了基于实测EPBM屏蔽压力估算体积损失的公式。该方程可与现有的经验方法一起用于估算隧道纵轴横向的地表沉降剖面。
Empirical methods for estimating tunneling-induced ground movements have been widely adopted in the tunneling industry. The transverse surface settlement profile can be described by a Gaussian curve or a modified Gaussian curve whose maximum value and trough width are related to volume loss. Volume loss in turn is related to soil type, tunnel geometry, and construction techniques. Several empirical equations have been developed based on the Gaussian curve and the assumptions of (1) trough width dependency on tunnel depth and ground condition; and (2) volume loss dependency on the ground type and construction techniques. For Earth Pressure Balance Machine (EPBM) tunneling, a volume loss of 0.5% in granular soils and 1%–2% the soft clay has been assumed in the past as an initial estimate. However, with complete filling and pressurization of both the shield (overcut) gap and the grouted tail gap around the lining, volume losses below 0.1% to 0.2% are being achieved in the alluvial granular and clay soils on current Los Angeles Metro tunneling projects. The LA Metro K Line Crenshaw/LAX transit project, tunneled from 2016 to 2018, has provided an opportunity to acquire and organize data on compatible data management systems, and evaluate the extensive field monitoring data for ground conditions specific to predominately granular soils in Old Alluvium. These data allow for the improvement of current empirical methods and correlations for predicting surface settlement induced by EPBM tunnels. The approximately 1-mi (1.6-km)-long, 20.6-ft (6.5-m)-diameter twin tunnels were excavated by an EPBM in a dense sand layer overlain by a silt/clay layer. The cover-to-diameter ratio was consistently about 2. The settlements and volume losses are observed to be heavily dependent on the face/shield pressures. In general, maintaining continuous pressures can significantly reduce settlements. An equation for estimating the volume loss based on the measured EPBM shield pressures is proposed. This equation can be used with the existing empirical methods to estimate the surface settlement profile transverse to the longitudinal axis of the tunnel.