在国王十字redevelopment

作者：Lidijašpiranec和Steven Thurgood

国王十字架是英国伦敦最重要的重建项目之一。国王十字架周围的地区有67英亩的未使用土地，该土地于2008年被指定为开发。总体规划包括50栋建筑物，1,900栋新房屋，20个新街道，26个新公园和正方形以及26英亩的开放空间。

该主要铁路枢纽的更新工作始于2010年。该项目的主要限制之一是该地点下面有四个铁路隧道，这是与King Cross站的主要连接的一部分。这些连接每天被数十万通勤者使用。

For the development project to proceed, it was necessary to build adjacent to and over the top of these tunnels. In conjunction with Network Rail, the asset owner, it was agreed this could take place, provided any movement of the tunnels and track was analysed and a real-time monitoring scheme installed. The monitoring scheme was required to confirm predicted movements, and measure any exceedances, so work could be stopped before any damage to the infrastructure occurred, minimising risks to travellers and trains.

由于项目的大小，其价值和影响，监测系统的要求是严格的：

Robust- 持续12年的合同持续时间
可扩展- 适应扩展
Accurate / Precise- to measure and report with confidence
Repeatable- 获得一致的观察
Automated- to run in an environment with no manned access
Continuous- to operate 24/7
无障碍- to all stakeholders

Pell Frischmann, one of the UK’s leading consulting engineering companies with almost 100 years of experience, accepted this monitoring challenge. Having used various Leica Geosystems’ instruments and equipment for over 30 years, the company knew thatLeica Geosystems’ monitoring solutionswere the right way to go, on account of reliability, technical excellence, backup and support. Thus, the firm partnered withSCCS Survey Equipment Ltd, part of Hexagon, the UK leading distributor of Leica Geosystems Surveying Equipment, to deliver the required monitoring system.

“ Leica Geosystems开发新产品的悠久历史，同时完全保持向后兼容性，确保可以在该项目的bob综合app下载延长期间使用最新设备扩展该系统。同时，Leica Geosystems的维护和支持网络意味着在整个项目生命周期内，所有购买的设备（无论其年龄如何）都可以使用备件和维修，” Pell Frischmann的资产管理总监Gary Weekes说。“ SCC在帮助指定合适的设备并协助设置系统方面的支持也是为项目选择Leica GeoSystems设备的关键驱动力。”

There were two independent monitoring systems installed at King’s Cross Station – the primary one was geodetic monitoring with automatic total stations (ATS) and the backup one was geotechnical monitoring, providing redundancy in measurements, delivering additional information and increasing certainty and reliability of results.

Tailored solution for London’s tunnels

The equipment used for the project consisted of following sensors:

徕卡TM30/50监测总站提供bob appleed the ability to narrow the measuring laser beam detector sensitivity, eliminating the risk of interference from adjacent targets in these long linear sites, which is a unique ability of Leica Geosystems’ instrumentation. This enabled the system to be configured with fewer total stations while still maintaining the target frequency required by Network Rail. The monitoring instrumentation automatically measures:

• 3D隧道位移通过测量五个横截面的五个棱镜阵列

• Rail geometry for cant, twist, gauge and alignment by measuring prism pairs attached to each rail of the track

Outside of the tunnels, a permanent network of stable control points was measured to eliminate the movements of the total stations.

The wireless tilt nodes were installed on the tunnel lining adjacent to the crown prism and track bed/sleepers at 3m intervals to mirror rail prisms. The wireless tilt and distance nodes were located on the tunnel lining at each 10-m cross section to measure convergence and ovalisation of the tunnel.

安装了所有内容后，使用扫描仪及其专用软件的轨道几何测量设备用于测量/验证隧道，并确保监视设备清除过往的火车和运动式信封。

Data acquisition and processing of all geodetic and geotechnical measurements were facilitated using Leica GeosystemsGeoMoS Monitor。The software allowed for assigning priorities and control of observations, whereas the frequency of observations was remotely adjustable to match dynamic events. The computed results of prism measurements were further used for computation of virtual observation points for mathematically derived values, enabling complex calculations from a variety of data sources into a single computation model. Deformation movement limits, alarms and actions were defined with bespoke variables depending on activity and instrumentation. Data visualisation and reporting were seamlessly integrated using the cloud-based service from Leica GeosystemsGeoMoS Now!。

Due to the complex environment and long linear nature of the project with only stable areas at each end, the total station data required correction to a homogeneous model rather than each unit working independently. Thus, a fully-integrated and automated least square adjustment of the control network was computed real time during the observation cycles using Star*Net software by MicroSurvey Software Inc., part of Hexagon. The GeoMoS system was then automatically updated with live network adjustment coordinates for the entire network prior to each monitoring array observation.

“The use of GeoMoS Now! enabled us to establish simple, clear dashboards for the project. At any time, there were multiple contractors onsite, who were only interested in individual sections of the monitoring scheme. GeoMoS Monitor allowed specific alert regimes to be established for each contractor, with individual dashboards developed in GeoMoS Now!, which were login specific to that contractor.“, explained Weekes.

克服监控挑战

图像的基本单位有几个复杂的挑战l Frischmann team had to overcome during the monitoring period. In the Thameslink Tunnels, trains were passing at 50 mph every five minutes, causing vibration and air movement, affecting instrument orientation and level. The access to the tunnels was limited to two four-hour shifts every three months, so a permanent solution was found by installing GeoLaser AD-12 self-levelling tribrach to enable remote users to correct the total station back to the horizontal plane without requiring access. This was fully controlled via GeoMoS Monitor.

In the Gasworks Tunnels there was a different challenge to be overcome – an oily soot residue. The brickwork in the tunnels had thick layers of it built up over time from the years of steam and diesel trains operating in the tunnels. This caused constant residue built up throughout the monitoring period. Therefore, the total station optics and prisms needed to be cleaned every couple of months to maintain signal strength, as part of the active maintenance plan.

Over the life of the installation, the monitoring scheme operator with continued support from SCCS found innovative solutions to increase system reliability and reduce operational costs. This also included anti-corrosive fittings and prism covers which made them resistant to constant exposure to previously unknown environmental conditions discovered in the tunnel.

“The equipment delivered accurate and repeatable results 24/7 for extended periods of time without the need for manual intervention between the standard bi-monthly maintenance visits. This was particularly important in the Gasworks tunnels, where diesel residue and water leakage caused a particularly harsh working environment, in which the instrumentation had to operate faultlessly for 12 months between servicing,” said Weekes.

The reliability and accuracy of the equipment ensured that all work on the development near the tunnels could continue without any delays a decade later from 2010. This instilled confidence in the system from Network Rail and there has been no need to stop or slow trains, avoiding any financial penalties delays would have incurred.”

Future-proof monitoring data

一旦国王十字架的再生完成，对隧道的监视将继续。该数据集的重要性在于记录隧道的自然运动和状况。这可能成为工程师确定隧道生命周期延长并计划预防性维护的重要资产。

“The client and all stakeholders were very happy with the system and its performance. They particularly liked the real time unlimited access to the data, which enabled them to check any minor triggers and see trending without the need for any specialist knowledge or training on the system. We plan on sharing our level of satisfaction with this product within this collaborative network of companies, so it can be utilised on a wide range of projects,” concluded Weekes.

“Pell Frischmann provides innovative solutions working closely with Leica Geosystems and wider Hexagon team. They have responded promptly to any issues, including out of hours and have saved the project from the costs of any delays to trains”, added Alastair Mitchell, project director of Kings Cross Partnership.