Monitoring buried infrastructure deformation using acoustic emissions

Deformation of soil bodies and buried infrastructure elements (i.e. soil-structure systems) generates acoustic emission (AE). Detecting this AE by coupling sensors to buried structural elements can provide information on asset condition and early warning of accelerating deformation behaviour. A novel approach for deformation monitoring of buried steel infrastructure (e.g. pipes and pile foundations) using AE is described in the paper. The monitoring concept employs pre-existing, or newly built, buried steel infrastructure assets as waveguides. The propagation of AE through example pipes acting as waveguides has been modelled computationally using the program Disperse. A parametric study has been used to investigate the influence of key variables such as burial depth, surrounding soil type, internal environment, pipe diameter, wall thickness, frequency and mode type upon AE propagation and attenuation. Understanding the propagation and attenuation of AE is of fundamental importance for development of a monitoring strategy and specifically to determine the spacing of sensors deployed along infrastructure elements. The generation of AE due to soil-structure interaction mechanisms has been investigated using a programme of large direct shear tests of soil against steel plates under a range of conditions (e.g. soil type, plate surface conditions, stress level, strain rate). New, fundamental understanding of AE generation and propagation in buried infrastructure is enabling a framework to be developed for interpreting asset condition from AE measurements. The paper will introduce the approach developed, describe the parametric study of AE propagation and attenuation presenting example results, and show typical AE behaviour for soil-structure interaction obtained in the large shear tests. The implications for design of a monitoring framework will be discussed

Acoustic emission monitoring in geotechnical element tests

Acoustic emission (AE) is high-frequency noise (>10kHz) generated by deforming materials. AE is widely used in many industries for non-destructive testing and evaluation; however, it is seldom used in geotechnical engineering, despite evidence of the benefits, because AE generated by particulate materials is highly complex and difficult to measure and interpret. This paper demonstrates that innovative AE instrumentation and measurement can enhance insights into geotechnical element tests. Results from a programme of triaxial compression and shear, large direct-shear and large permeameter experiments show that AE can be used to characterise mechanical and hydromechanical behaviour of soils and soil-structure interaction, including: dilative shear behaviour; transitions from pre- to post-peak shear strength; changes in strain rates; isotropic compression; unload-reload cycles of compression and shear; and seepage-induced internal instability phenomena

An acoustic emission landslide early warning system for communities in low-income and middle-income countries

Early warning systems for slope instability are needed to alert users of accelerating slope deformation behaviour, enable evacuation of vulnerable people, and conduct timely repair and maintenance of critical infrastructure. Communities exposed to landslide risk in low- and middle-income countries seldom currently instrument and monitor slopes to provide a warning of instability because existing techniques are complex and prohibitively expensive. Research and field trials have demonstrated conclusively that acoustic emission (AE) monitoring can be an effective approach to detect accelerating slope movements and to subsequently communicate warnings to users. The objective of this study was to develop and assess a simple, robust, low-cost AE monitoring system to warn of incipient landslides, which can be widely deployed and operated by communities globally to help protect vulnerable people. This paper describes a novel AE measurement sensor that has been designed and developed with the cost constrained to a few hundred dollars (US). Results are presented from physical model experiments that demonstrate performance of the AE system in measuring accelerating deformation behaviour, with quantifiable relationships between AE and displacement rates. Exceedance of a pre-determined trigger level of AE can be used to communicate an alarm to users in order to alert them of a slope failure. Use of this EWS approach by communities worldwide would reduce the number of fatalities caused by landslides

Effectiveness of a national quality improvement programme to improve survival after emergency abdominal surgery (EPOCH): a stepped-wedge cluster-randomised trial

Background: Emergency abdominal surgery is associated with poor patient outcomes. We studied the effectiveness of a national quality improvement (QI) programme to implement a care pathway to improve survival for these patients. Methods: We did a stepped-wedge cluster-randomised trial of patients aged 40 years or older undergoing emergency open major abdominal surgery. Eligible UK National Health Service (NHS) hospitals (those that had an emergency general surgical service, a substantial volume of emergency abdominal surgery cases, and contributed data to the National Emergency Laparotomy Audit) were organised into 15 geographical clusters and commenced the QI programme in a random order, based on a computer-generated random sequence, over an 85-week period with one geographical cluster commencing the intervention every 5 weeks from the second to the 16th time period. Patients were masked to the study group, but it was not possible to mask hospital staff or investigators. The primary outcome measure was mortality within 90 days of surgery. Analyses were done on an intention-to-treat basis. This study is registered with the ISRCTN registry, number ISRCTN80682973. Findings: Treatment took place between March 3, 2014, and Oct 19, 2015. 22 754 patients were assessed for elegibility. Of 15 873 eligible patients from 93 NHS hospitals, primary outcome data were analysed for 8482 patients in the usual care group and 7374 in the QI group. Eight patients in the usual care group and nine patients in the QI group were not included in the analysis because of missing primary outcome data. The primary outcome of 90-day mortality occurred in 1210 (16%) patients in the QI group compared with 1393 (16%) patients in the usual care group (HR 1·11, 0·96–1·28). Interpretation: No survival benefit was observed from this QI programme to implement a care pathway for patients undergoing emergency abdominal surgery. Future QI programmes should ensure that teams have both the time and resources needed to improve patient care. Funding: National Institute for Health Research Health Services and Delivery Research Programme

Effectiveness of a national quality improvement programme to improve survival after emergency abdominal surgery (EPOCH): a stepped-wedge cluster-randomised trial

BACKGROUND: Emergency abdominal surgery is associated with poor patient outcomes. We studied the effectiveness of a national quality improvement (QI) programme to implement a care pathway to improve survival for these patients. METHODS: We did a stepped-wedge cluster-randomised trial of patients aged 40 years or older undergoing emergency open major abdominal surgery. Eligible UK National Health Service (NHS) hospitals (those that had an emergency general surgical service, a substantial volume of emergency abdominal surgery cases, and contributed data to the National Emergency Laparotomy Audit) were organised into 15 geographical clusters and commenced the QI programme in a random order, based on a computer-generated random sequence, over an 85-week period with one geographical cluster commencing the intervention every 5 weeks from the second to the 16th time period. Patients were masked to the study group, but it was not possible to mask hospital staff or investigators. The primary outcome measure was mortality within 90 days of surgery. Analyses were done on an intention-to-treat basis. This study is registered with the ISRCTN registry, number ISRCTN80682973. FINDINGS: Treatment took place between March 3, 2014, and Oct 19, 2015. 22 754 patients were assessed for elegibility. Of 15 873 eligible patients from 93 NHS hospitals, primary outcome data were analysed for 8482 patients in the usual care group and 7374 in the QI group. Eight patients in the usual care group and nine patients in the QI group were not included in the analysis because of missing primary outcome data. The primary outcome of 90-day mortality occurred in 1210 (16%) patients in the QI group compared with 1393 (16%) patients in the usual care group (HR 1·11, 0·96-1·28). INTERPRETATION: No survival benefit was observed from this QI programme to implement a care pathway for patients undergoing emergency abdominal surgery. Future QI programmes should ensure that teams have both the time and resources needed to improve patient care. FUNDING: National Institute for Health Research Health Services and Delivery Research Programme

Acoustic emission generated by granular soil-steel structure interaction

This study has established quantitative interpretation of acoustic emission (AE) generated by granular soil/steel structure interaction. This new knowledge will enable the evolution of soil/structure interaction behaviour to be interpreted from AE measurements. AE monitoring could now provide early warning of soil/structure system (e.g. buried pipelines, pile foundations and retaining structures) limit state failures in the field and enhance insights into element and physical model tests in the laboratory. Results from a programme of large direct-shear tests performed on granular soil/steel interfaces show that AE generation is influenced by the normal effective stress, mobilised shearing resistance and shearing velocity. Compression-induced AE activity in granular soil/steel systems is negligible until the current stress conditions exceed the maximum that has been experienced in the past. Relationships have been quantified between AE and normal effective stress, mobilised shearing resistance and shearing velocity, enabling quantitative interpretation of cyclic and accelerating soil/structure interaction behaviour from AE measurements