BOTDR Distributed Fibre Optic Strain Sensing for the Monitoring of an Existing Cast Iron Tunnel

Constructing tunnels in highly congested urban cities is a challenge, as the construction will inevitably take place in close proximity to existing structures both above and below ground. As more tunnels are being constructed, it is inevitable that some tunnels will be constructed in close proximity to existing tunnels and monitoring of the existing tunnels in this case is paramount for the design and construction works. The discrete nature of conventional monitoring instrumentation requires significant interpolation and judgement in order to understand the overall behaviour of the tunnel itself. Subsequently, conservative design approaches will have to be adopted to cater for the gaps in knowledge, which could lead to unnecessary delays and high costs. Distributed fibre optic strain sensing systems based on Brillouin Optical Time Domain Reflectometry (BOTDR) could offer an alternative; in this paper a case study is presented where fibre optic cables were deployed to monitor the response of the cast iron Royal Mail tunnel in the vicinity of London Liverpool Street Station during the construction of Crossrail’s new platform tunnel directly below it. Single mode single core tight-buffered cables were attached directly to the intrados of the cast iron tunnel lining of the Royal Mail tunnel to understand its response during the construction works. This paper focuses on the challenges and considerations in deploying the fibre optic system in the tunnel and presents some of the data, which demonstrates the potential benefit of using such a system in real, complex tunnelling scenarios

BOTDR Distributed Fibre Optic Strain Sensing for the Monitoring of an Existing Cast Iron Tunnel

Constructing tunnels in highly congested urban cities is a challenge, as the construction will inevitably take place in close proximity to existing structures both above and below ground. As more tunnels are being constructed, it is inevitable that some tunnels will be constructed in close proximity to existing tunnels and monitoring of the existing tunnels in this case is paramount for the design and construction works. The discrete nature of conventional monitoring instrumentation requires significant interpolation and judgement in order to understand the overall behaviour of the tunnel itself. Subsequently, conservative design approaches will have to be adopted to cater for the gaps in knowledge, which could lead to unnecessary delays and high costs. Distributed fibre optic strain sensing systems based on Brillouin Optical Time Domain Reflectometry (BOTDR) could offer an alternative; in this paper a case study is presented where fibre optic cables were deployed to monitor the response of the cast iron Royal Mail tunnel in the vicinity of London Liverpool Street Station during the construction of Crossrail’s new platform tunnel directly below it. Single mode single core tight-buffered cables were attached directly to the intrados of the cast iron tunnel lining of the Royal Mail tunnel to understand its response during the construction works. This paper focuses on the challenges and considerations in deploying the fibre optic system in the tunnel and presents some of the data, which demonstrates the potential benefit of using such a system in real, complex tunnelling scenarios

Distributed fiber optic sensing of axially loaded bored piles

Instrumented pile tests are vital to establish the performance of a pile and validate the assumptions made during initial design. Conventional instrumentation includes vibrating wire strain gauges and extensometers to measure the change in strain or displacements within a pile. Although these strain and displacement gauges are very accurate, they only provide strain/displacement readings at discrete locations at which they are installed. It is therefore common to interpolate between two consecutive points to obtain values corresponding to the data gaps between points; in practice, these discrete instrumented points could be tens of meters apart, at depths corresponding to different soil layers, and hence simple interpolation between the measurement points remains questionable. The Brillouin optical time-domain reflectometry fiber optic strain sensing system is able to provide distributed strain sensing along the entire length of the cable, enabling the full strain profile to be measured during a maintained pile load test. The strain data can also be integrated to obtain the displacement profile. This paper presents three case studies which investigate the performance of three concrete bored piles in London using both conventional vibrating wire strain gauges and distributed fiber optic strain sensing during maintained pile load tests, which enable comparisons made between the two instrumentation systems. In addition, finite-element analyses show that the ability to measure the full strain profiles for each pile is highly advantageous in understanding the performance of the pile and in detecting any abnormalities in the pile behavior

Monitoring the effects of tunnelling under an existing tunnel-fibre optics

Underground tunnel networks are at the heart of United Kingdom's infrastructure, carrying more than 1,100 million passengers each year along its 249 miles long network via 11 underground lines, serving 270 stations.With a complex existing underground rail network already in place; it is inevitable that new tunnels will be constructed within close proximity to existing tunnels. At London Liverpool Street Station, the new eastbound Crossrail platformtunnel was constructed underneath the existing Royal MailTunnel at a parallel alignment over a length of over 100m with a clear distance of less than 2m separating the two. Fibre optic strain sensing system based on Brillouin Optical Time Domain Reflectometry (BOTDR) was installed to measure continuous strain profiles of the cast iron linings of Royal Mail Tunnel. This has provided valuable insights to the deformation mechanisms both during the pilot and final tunnel enlargement. © 2014 Korean Geotechnical Society

Prevalence of cancer-related fatigue based on severity: a systematic review and meta-analysis

Abstract Cancer-related fatigue (CRF) affects therapeutic compliance and clinical outcomes including recurrence and mortality. This study aimed to comprehensively and comparatively assess the severity-based prevalence of CRF. From two public databases (PubMed and Cochrane Library), we extracted data containing information on both prevalence and severity of fatigue in cancer patients through December 2021. We conducted a meta-analysis to produce point estimates using random effects models. Subgroup analyses were used to assess the prevalence and severity by the organ/system tumor development, treatment phase, therapeutic type, sex and assessment method. A total of 151 data (57 studies, 34,310 participants, 11,805 males and 22,505 females) were selected, which indicated 43.0% (95% CI 39.2–47.2) of fatigue prevalence. The total CRF prevalence including ‘mild’ level of fatigue was 70.7% (95% CI 60.6–83.3 from 37 data). The prevalence of ‘severe’ fatigue significantly varied by organ/system types of cancer origin (highest in brain tumors 39.7% vs. lowest in gynecologic tumors 3.9%) and treatment phase likely 15.9% (95% CI 8.1–31.3) before treatment, 33.8% (95% CI 27.7–41.2) ongoing treatment, and 24.1% (95% CI 18.6–31.2) after treatment. Chemotherapy (33.1%) induced approximately 1.5-fold higher prevalence for ‘severe’ CRF than surgery (22.0%) and radiotherapy (24.2%). The self-reported data for ‘severe’ CRF was 20-fold higher than those assessed by physicians (23.6% vs. 1.6%). Female patients exhibited a 1.4-fold higher prevalence of ‘severe’ fatigue compared to males. The present data showed quantitative feature of the prevalence and severity of CRF based on the cancer- or treatment-related factors, sex, and perspective of patient versus physician. In the context of the medical impact of CRF, our results provide a comparative reference to oncologists or health care providers making patient-specific decision

A Tale of Two Tunnels-Understanding the Performance of Existing and New Tunnels during Construction Works

In many cases, new tunnels in highly populated urban cities like London will need to be constructed underneath a dense network of existing tunnels to avoid them. The construction of new tunnels, however, inevitably results in ground deformations, which are transmitted to adjacent existing structures. The response of existing cast iron tunnels to tunnelling-induced deformation is not well understood and practicing engineers are faced with significant uncertainties about their response. The first part of this paper presents a case study in which distributed fibre optic strain sensing (DFOSS) have been deployed in a section at an existing cast iron tunnel in London underneath which a new, much larger tunnel was being constructed. The DFOSS deployment in this case study provided a detailed response for the cast iron tunnel in a holistic manner that is not encountered in practice. In the second part of the paper, one of the latest case studies being conducted at the Cambridge Centre for Smart Infrastructure and Construction (CSIC), associated with the instrumentation and monitoring of cross-passages in sprayed concrete tunnel linings (SCL) is presented and discussed. The DOFSS provided new data and hence new insights into SCL behaviour that was not available before.This is a metadata record for an article that can't be shared due to publisher copyright