发表机构
ETH Zurich; AMOLF; Los Alamos National Laboratory（苏黎世联邦理工学院; 阿莫夫研究所; 洛斯阿拉莫斯国家实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究针对地球与月球上非掩埋型DAS信号质量差的问题，建立解析与数值模型，揭示弯曲应力释放机制，提出无量纲参数Theta，为优化缆线设计与部署提供定量准则。
AI 中文摘要
分布式声学传感（DAS）可沿光纤缆线测量动态应变，是传统地震传感器的可靠、高密度采样替代方案。为确保良好的地面至缆线耦合，缆线通常被埋在浅沟中。非掩埋型地表部署适用于快速响应的陆地应用及地外任务（如月球任务，此处掩埋不可行），但这类部署常因地面至缆线的应变传递差导致信号质量严重下降，其物理机制尚不明确。本研究确定弯曲应力释放为该损耗的解释机制：悬空缆线段通过弯曲而非拉伸或压缩来容纳地面应变，降低了到达光纤的可测量轴向应变。我们开发了首个非掩埋型DAS耦合的解析与数值模型，将悬垂缆线表示为离散地面接触点间的一系列悬空段，以解释并量化弯曲应力释放机制。分析揭示了无量纲参数Theta，由缆线初始重力诱导垂度与其半径的比值决定，该参数控制应变传递效率。当某段的垂度超过缆线半径的四分之一时，地面位移开始被弯曲吸收，而非作为可测量轴向应变传递。该框架预测了力学特性、缆线尺寸、预张力及重力对应变传递效率的影响，为优化地球与月球上的缆线设计和部署策略提供了定量准则。
英文摘要
Distributed acoustic sensing (DAS) cables are typically buried to ensure good coupling and reduce unwanted atmospheric noise. Unburied deployments are attractive for rapid response applications and for missions to the Moon, where burial is impractical. Unburied DAS, however, suffers from degraded signal quality due to poor strain transfer. Here we quantify bending stress relief as a mechanism behind this loss: cable segments suspended between ground contact points accommodate ground strain by bending, so less axial strain reaches the fiber. We derive the strain transfer of such a segment analytically, compare it to numerical models, and validate it on 56 laboratory configurations of different cable types and lengths. The efficiency is governed by a single dimensionless parameter $Θ$, set by the ratio of the segment's sag to the cable radius. Keeping the loss below 3% requires a sag below about a quarter of the cable radius. The prediction is quasi-static, holding below the fundamental resonance of the segments. The sag is dominated by the curvature the cable retains from spooling and handling rather than by gravitational sagging, so $Θ$ has to be measured and not computed from cable specifications. Because the gravitational contribution is small, the criterion applies equally to deployment on the Moon. Lunar gravity does reduce the friction available to resist slip at the contact points, but a force balance indicates that slip remains unlikely for natural moonquakes.
Comments39 pages, 14 figures. Submitted to Earth and Space Science. Revised version with validation laboratory data and added co-author. Includes Supporting Information
