Acoustic emission monitoring of active waveguides to quantify slope stability

The active waveguide is installed in a borehole that penetrates stable stratum below any shear surface or potential shear surface that may form beneath a slope. It comprises a metal waveguide rod or tube that provides a low resistance path for acoustic emission to travel from the source at the shear surface to the sensor at the ground surface. The annulus surrounding the waveguide is backfilled with granular soil. When the host slope deforms, the column of granular soil also deforms and this induces inter-particle friction and releases relatively high levels of acoustic emission that can propagate along the waveguide. Field trials and laboratory experiments reported by the authors have demonstrated that acoustic emission rates generated by active waveguides are proportional to the velocity of slope movement. This summary describes the operation of the active waveguide and Slope ALARMS acoustic emission sensor for use in slope stability monitoring. An on-going research project aiming to develop an algorithm that can quantify slope displacement rates through monitoring active waveguide generated acoustic emission is introduced

Inclinometer casings retrofitted with acoustic real-time monitoring systems

The paper details the concept of retrofitting inclinometer casings with active waveguides in order to provide subsurface instrumentation that can monitor the stability of slopes continuously and in real-time. The operation of the active waveguide, the unitary battery operated Slope ALARMS acoustic emission sensor and warning communication system are described. A field trial previously reported by the authors demonstrates that acoustic emission rates generated by active waveguides are proportional to the velocity of slope displacements, and can therefore be used to detect changes in rates of movement (i.e. accelerations and decelerations) in response to destabilising (e.g. rainfall) and stabilising (e.g. remediation) effects. The paper presents the results of a field trial of the acoustic monitoring system retrofitted inside an inclinometer casing in a reactivated landslide at Hollin Hill, North Yorkshire, UK. The study demonstrates that this approach can provide continuous information on slope movements with high temporal resolution. Converting manually and periodically read inclinometer casings into continuously monitored active waveguides using Slope ALARMS sensors is a cost effective solution to provide real-time information that could be used in the protection of people and infrastructure

Serviceability limit state design in geogrid reinforced walls and slopes

The design of geogrid reinforced walls and slopes, although a well-established science, still contains many unknowns, particularly around long-term serviceability. Serviceability, for walls and slopes, is associated with excessive deformation or damage affecting appearance, maintenance or service life. In most designs, the serviceability limit state is not considered critical. Currently, most serviceability checks do not attempt to determine or prescribe deformation limits on the built wall or slope, but rather impose limits on the theoretical mobilised strains of geogrid reinforcement, considering the unfactored imposed loads. In many cases, these prescribed post-construction allowable strain limits are based on long-term, or accelerated creep testing, undertaken when the geogrid is not interacting with soil. In some situations, designs are grossly overconservative. This paper reviews the current state of practice, summarising some of the serviceability design issues around geogrid reinforced walls and slopes, with a particular focus on long-term post-construction deformations. The paper goes on to highlight areas of non-conformity in serviceability design, between the major national codes in Europe, assessing their strengths and weaknesses. Additionally, the paper highlights potential areas of on-going and further work that may offer a better understanding of the serviceability limit state of geogrid reinforced soil walls and slopes

Quantification of road network vulnerability and traffic impacts to regional landslide hazards [abstract]

Slope instability represents a prevalent hazard to transport networks. In the UK regional road networks are frequently disrupted by multiple slope failures triggered during intense precipitation events; primarily due to a degree of regional homogeneity of slope materials, geomorphology and weather conditions. It is of interest to examine how different locations and combinations of slope failure impact road networks, particularly in the context of projected climate change and a 40% increase in UK road demand by 2040. In this study an extensive number (>50 000) of multiple failure event scenarios are simulated within a dynamic micro simulation to assess traffic impacts during peak flow (7 – 10 AM). Possible failure locations are selected within the county of Gloucestershire (3150 km2) using historic failure sites and British Geological Survey GeoSure data. Initial investigations employ a multiple linear regression analyses to consider the severity of traffic impacts, as measured by time, in respect of spatial and topographical network characteristics including connectivity, density and capacity in proximity to failure sites; the network distance between disruptions in multiple failure scenarios is used to consider the effects of spatial clustering. The UK Department of Transport road travel demand and UKCP09 weather projection data to 2080 provide a suitable basis for traffic simulations and probabilistic slope stability assessments. Future work will thus focus on the development of a catastrophe risk model to simulate traffic impacts under various narratives of future travel demand and slope instability under climatic change. The results of this investigation shall contribute to the understanding of road network vulnerabilities and traffic impacts from climate driven slope hazards

Indirect economic impact of landslide hazards by disruption to national road transportation networks; Scotland, United Kingdom

Indirect economic impact of landslide hazards by disruption to national road transportation networks; Scotland, United Kingdo

Characterising regional landslide initiation thresholds in Scotland, UK using NIMROD c-band precipitation radar and the BGS National Landslide Database

Characterising regional landslide initiation thresholds in Scotland, UK using NIMROD c-band precipitation radar and the BGS National Landslide Databas

Designing with marginal fills

Some of the most sustainable and economical benefits of using geosynthetics are found in reinforcement applications. These applications allow the use of lower quality on-site material such as fine grained soils often referred to as ‘marginal fills’. This paper identifies the state of practice and understanding of designing with these soils in applications such as embankments, slopes and retaining walls. Designers often rely on published guidance documents and the paper discusses the influence BS 8006 (2010) has on the use of ‘marginal fills’ in construction and how the need for clearer more specific guidance. The study highlights that often well compacted fine grained fills placed close to optimum moisture content generate suctions, and this results in relatively high strength interaction between the fill and geosynthetic reinforcement. In cases where a fine grained fill with high moisture content is used, geosynthetic reinforcement that provides in-plane drainage may be beneficial

Landfill side slope lining system performance: a comparison of field measurements and numerical modelling analyses

Low permeability engineered landfill barriers often consist of a combination of geosynthetics and mineral layers. Even though numerical modelling software is applied during the landfill design process, a lack of data about mechanical performance of landfill barriers is available to validate and calibrate those models. Instrumentation has been installed on a landfill site to monitor multilayer landfill lining system physical performance. The lining system comprises of a compacted clay layer overlaid by high density polyethylene geomembrane, geotextile and sand. Data recorded on the site includes: geosynthetic displacements (extensometers), strains (fibre optics, Demec strain gauges, extensometers) and stresses imposed on the liner (pressure cells). In addition, temperature readings were collected by a logger installed at the surface of the geomembrane, at the clay surface using pressure cell thermistors and air temperature using a thermometer. This paper presents readings collected throughout a period of three years and compares this measured performance with the corresponding numerical modelling of the lining system for stages during construction. Numerical modelling predictions of lining system behaviour during construction are comparable with the measurements when the geosynthetics are covered soon after placement, however, where the geosynthetics are left exposed to the sun for an extended period of time, in situ behaviour of the geosynthetics cannot be replicated by the numerical analysis. This study highlights the significant influence of the effect of temperature on geosynthetics displacements. A simple thermal analysis of the exposed geosynthetics is used to support the explanation for observed behaviour

Personalised learning paths for information literacy using Canvas MasteryPaths

This project report describes using MasteryPaths in the Canvas Virtual Learning Environment as a method of helping improve the information literacy (IL) competence for undergraduate science students studying in their first year at university. The MasteryPaths incorporated a series of formative quiz assessments on referencing and finding and evaluating information, which depending on the students’ initial score directed them to further enrichment or support materials. Four degree courses (Biology, Forensics, Biomedicine and Sport) each included the MasteryPaths in a first-year module in 2020/21, which were available in Canvas following face-to-face IL sessions. Focus groups were conducted with students, and interviews were carried out with two module leaders to explore perceptions of the MasteryPaths design and effectiveness for IL skills. The article provides insight into how online, self-paced, IL formative quiz assessments can be developed in a way to motivate and engage students in their learning.</p

Rationalizing Context-Dependent Performance of Dynamic RNA Regulatory Devices

The ability of RNA to sense, regulate, and store information is an attractive attribute for a variety of functional applications including the development of regulatory control devices for synthetic biology. RNA folding and function is known to be highly context sensitive, which limits the modularity and reuse of RNA regulatory devices to control different heterologous sequences and genes. We explored the cause and effect of sequence context sensitivity for translational ON riboswitches located in the 5′ UTR, by constructing and screening a library of N-terminal synonymous codon variants. By altering the N-terminal codon usage we were able to obtain RNA devices with a broad range of functional performance properties (ON, OFF, fold-change). Linear regression and calculated metrics were used to rationalize the major determining features leading to optimal riboswitch performance, and to identify multiple interactions between the explanatory metrics. Finally, partial least squared (PLS) analysis was employed in order to understand the metrics and their respective effect on performance. This PLS model was shown to provide good explanation of our library. This study provides a novel multivariant analysis framework to rationalize the codon context performance of allosteric RNA-devices. The framework will also serve as a platform for future riboswitch context engineering endeavors