Inherent soil variability, measurement error, statistical uncertainty, and transformation uncertainty constitute the four main sources of geotechnical uncertainties. This paper presents a systematic probabilistic analysis framework, through a case study, to assess the influence of geotechnical uncertainty on the existing shield tunnel settlement due to new tunneling underneath. Within this framework, various sources of geotechnical uncertainties are quantified using available Cone Penetration Test data (cone tip resistance) in the studied area, and three scenarios (i.e., pessimistic, neutral, and optimistic scenarios) are considered to incorporate different magnitudes of measurement errors. Through a random field-based 3D numerical simulation, the existing tunnel settlement by construction of a new tunnel is evaluated under the three scenarios. The errors in the settlement prediction are quantified using the monitored settlement data in a probabilistic manner with the assistance of Monte Carlo simulations. Two types of errors in predicting the existing tunnel settlement are identified (positive error, which occurs when the predicted settlements exceed the monitored settlement; and negative error, which occurs when the predicted settlements are smaller than the monitored settlement), and a conditional random field-based numerical simulation is performed. The results indicate that the conditional random field-based numerical simulation significantly reduces the positive error at the junction of the two tunnels, with the largest accuracy improvement of 48% for the pessimistic scenario.

中文翻译：

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评估岩土工程不确定性对地下新隧道造成的现有隧道沉降的影响


固有的土壤变异性、测量误差、统计不确定性和转变不确定性构成了岩土工程不确定性的四个主要来源。本文通过案例研究提出了一个系统的概率分析框架，以评估由于下方新隧道开挖而引起的岩土工程不确定性对现有盾构隧道沉降的影响。在此框架内，使用研究区域中可用的锥体触探测试数据（锥尖阻力）量化岩土工程不确定性的各种来源，并考虑三种情景（即悲观、中性和乐观情景）来包含不同幅度的测量误差。通过基于随机场的 3D 数值模拟，评估了三种情景下新隧道建设对现有隧道沉降的影响。在 Monte Carlo 模拟的帮助下，使用监测的沉降数据以概率方式量化沉降预测中的误差。确定了预测现有隧道沉降的两种错误（正误差，当预测的沉降超过监测的沉降时发生;和负误差，当预测的沉降小于监测的沉降时发生），并进行了基于条件随机场的数值模拟。结果表明，基于条件随机场的数值模拟显著降低了两条隧道交界处的正误差，悲观情景下的精度最大提高48%。