坎贝尔科学TDR系统监视加利福尼亚海岸悬崖的斜坡运动
加利福尼亚州圣地亚哥县的北部县运输区（NCTD）确定，应监视Del Mar的沿海悬崖上方的三段铁轨，以进行危险的斜坡运动。这导致了沿1000米轨道的连续监测系统的开发。由于要监视的长度，因此使用常规的单点监测系统，例如多个倾斜度或现场倾斜仪（IPI）是不切实际的。沿着赛道的任何地方都可能发生虚张声势，因此使用单点仪器将需要大量的传感器和监视器。取而代之的是，提议沿轨道的高牢固段安装水平的时间域反射量（TDR）同轴电缆传感器。
The TDR monitoring system works similarly to radar. It uses a coaxial cable as a sensor, with any slope movement deforming or shearing the cable at the location of movement. When a voltage pulse from a reflectometer encounters a deformation, or the end of the sensor, the amount of reflected energy is proportional to the extent of the deformation. The reflectometer accurately determines the location of the deformation and the relative extent of movement as noted by the magnitude of the reflection.
Site Description
受监测的区域包括容易发生侵蚀和相对较小的块状故障的沿海悬崖。虚张声势在海滩上方约15米处。沿着虚张声势的铁轨范围从短短6米到距离悬崖边缘的30米不等。
Although the bluffs appeared stable, there had been some erosion problems that required soldier-pile walls, drainage enhancements, and shotcrete reinforcement. In addition, about fifty years earlier one segment of the bluff had failed, causing the wreck of a freight train.
虚张声势由相对较强的砂岩和柔软且可侵蚀的粉砂组成。波浪作用和景观灌溉中大量的地下水有助于减弱和软化粉砂。结果是破坏了砂岩，其次是当地的沿海悬崖衰竭。
Instrumentation Overview
远程数据采集设备包括数据记录器，多路复用器和通信设备。此外，对于与Datalogger进行编程和交互所必需的软件。TDR是一种相对较新的监测斜率运动的方法。该技术最初开发用于定位通信和电源线中的断裂和故障，将同轴电缆用作传感器和时间域反射计进行测量。
使用多路复用器允许将多个传感器连接到单个Datalogger。多路复用器已连接到Datalogger上的一组端口。数据由记录器顺序收集。多路复用器甚至可以彼此多路复用，从而创造了阅读大量乐器的能力。
监视系统设计
监视系统由中央控制和监视单元和三个TDR监视站组成。中央监控单元检查了每个监视站的状态，并控制了系统的警报通知功能。TDR监视站每个人都轮询了两条TDR传感器电缆，以进行电缆变形或断裂。
At each monitoring station were a Campbell Scientific CR10X datalogger, SDMX50 TDR multiplexer, and TDR100 reflectometer. The datalogger polled two horizontal TDR cables every four minutes and compared the reflected waveform to a baseline signature. If the reflected data indicated a deformed or broken cable, an alert signal consisting of 5 Vdc was applied to a wire monitored by the CR23X Micrologger® at the central control and monitoring unit. There, an automated telephone dialer notified railway personnel of possible bluff movement. Personnel could then contact the system by telephone and determine the location of the cable deformation so that a safety inspection of the bluff and track could be made.
The datalogger was capable of distinguishing between a lowlevel alert (deformed cable indicating small movement), and a high-level alert (sheared cable and possible large magnitude slope failure). TDR sensor cables were routed under the tracks and installed parallel to the tracks in a shallow trench. The cables were enclosed in a cement/sand grout to ensure deformation should a slope movement occur. A total of approximately 1000 meters of sensor cable was installed.
电信
Each datalogger was connected to a Campbell Scientific MD9 multidrop interface. RG59 coaxial cable was used to connect these network nodes. At the central monitoring station, an additional MD9 accessed the network dataloggers through the telephone line.
除调制解调器外，三个自动级别还使用了电话线。激活后，拨号器最多拨打了八个电话号码，并发出了适用于所需操作类型的警报消息。
建造
使用拖拉机安装的沟槽安装同轴传感器电缆。将沟渠切成0.7米深，平行于距离轨道和虚张声势之间的轨道中心线约4米的轨道。将50毫米的瘦混凝土放在沟槽的底部，并将传感器电缆放在顶部。将另外0.3米的混凝土放在电缆顶部。混凝土套件后，其余的沟槽用压实的填充物回填。
创新技术应用
据作者的知识，该项目代表了具有运动警报功能的TDR坡度监控迄今为止的最大单个应用程序。警报功能的一个主要好处是每个监视站最多拨打八个不同的电话号码来通知人员可能发生故障状况的能力。三个拨号器中的每一个都专门用于远程监视站之一。例如，远程监控站2上的传感器变形将触发八个人的电话，以提醒他们在站2附近可能的斜坡运动。此外，该区域监控的范围还具有保护铁路和高速公路的巨大潜力他们受到危险的斜坡运动的威胁。
