757 research outputs found

    Alaska University Transportation Center 2012 Annual Report

    Get PDF

    Reuse and Sustainability of Flood Defences

    Get PDF
    Rainfall has always been an important quantity to measure throughout history due to its importance in predicting floods and droughts. In the present day, such predictions on the severity of flooding events are critical so that appropriate flood defences may be constructed in anticipation of these events to limit any damages. With the increasing concerns of human influenced (anthropogenic) climate change will affect rainfall, there is a growing need to quantify and incorporate these events into the design of flood defences, such as earthfill embankments. As geotechnical modelling techniques are being developed to assist in the design and upgrading of earth embankments, various failure mechanisms and the behaviour of the soil within an embankment are better understood. However, one concern which arises is that there is an uncertainty on how climate change would affect the performance of these embankments. Therefore, the main purpose of this research is to identify the key failure mechanisms that may occur throughout the embankment’s life cycle, taking into account climate change effects, and to develop solutions to these issues. A site on the Thames estuary was chosen as the setting for this research. Taking into consideration a changing climate, sub-daily rainfall was produced for this site using a combination of stochastic rainfall generators and projected climate variables at the location. Following calibration and validation analyses for the foundation and embankment soils, a complete lifecycle analysis framework was established, using the previously generated rainfall as inputs to the soil-atmosphere boundary. The lifecycle framework was able to inform on both the general long-term performance of the embankment in a changing climate, and the resilience of the embankment to future extreme events. With the detailed lifecycle analysis, various strategies in reusing the embankment by raising it was also explored, to improve the embankment’s adaptability to future climate.Open Acces

    Assessing soil erosion associated with main roads in south-eastern South Africa.

    Get PDF
    Ph. D. University of KwaZulu-Natal, Pietermaritzburg 2014.Construction of linear infrastructure such as roads is increasing worldwide for the provision of efficient transportation of both humans and commodities. However, roads have been widely recognised as significant causes of increased soil erosion due to their influence on the hydrologic and geomorphic processes through the modification of natural hill-slope profiles, the construction of cut and fill embankments as well as impervious road surfaces that concentrate runoff. Accelerated soil erosion due to roads is of particular concern since the associated environmental impacts have economic ramifications related to water treatment and soil rehabilitation. In the light of the above, a better understanding of road-related soil erosion is required to guide environmentally sustainable future developments and erosion control efforts. The present study assesses soil erosion associated with main tar roads in the south-eastern region of South Africa. The first part of the study provides an overview of the linkages of roads with soil erosion by water, related structural designs that facilitate soil erosion processes as well as available approaches for assessing road-related soil erosion and the available erosion control techniques. Secondly, the study focuses on exploring the characteristics (i.e. gradient, length, and vegetation cover) of degraded and non-degraded roadcuts with a view to understanding why some roadcuts are degraded while others are not. Moreover, the study investigates the relationship between the characteristics of the roadcuts and the dimensions (i.e. width and depth) of the rills. Results show that degraded roadcuts are steeper, longer and have a lower percentage of vegetation cover when compared to non-degraded roadcuts. The results further show that there is a significant relationship between the width and depth of the rills, and the slope gradient and percentage of vegetation cover of the roadcuts. These results prompted the need to evaluate the volume of soil loss, using rill dimensions on roadcuts as well as an assessment of the relationship between the volume of soil loss and the soil properties. Results show that soil loss correlates significantly with all the rill dimensions, and the rill depth is the foremost variable in calculating rill volume than the rill width and length. In addition, the results show that there is a significant relationship between the volume of soil loss and the soil properties of the roadcuts. The study further used remotely sensed data to assess gully erosion related to road drainage release and examined the relationship between physical and climatic factors (i.e. road contributing surface area, vegetation cover, hillslope gradient and rainfall) and the volume of gullies. The results indicate that the road contributing surface area, vegetation cover and hillslope gradient have a significant contribution and influence on the size of the gullies along major armoured roads. Moreover, the results show that remote sensing technologies have the capability to investigate road-related gully erosion where detailed field work remains a challenge due to economic and time constraints. Finally, in order to evaluate the effectiveness of soil erosion control methods along the roads, the study investigates the performance of different soil erosion control methods utilised on the roadcuts. It was observed that most of the slope stabilisation methods are successful in controlling soil erosion while the majority of drainage control methods performed poorly. The results show that good performance is related to vegetation re-establishment, while poor performance may be attributed to improper application, lack of inspection and maintenance. Overall, the study provides an understanding of erosion related to the post construction phase of roads. In this regard, it is expected that the results of this study will contribute to the management of roads from the soil erosion perspective through appropriate interaction with the South African National Roads Authority (SANRAL). It is hoped that this work will lay the foundation for environmentally sustainable road construction, maintenance and the formulation of effective soil erosion control measures in the future

    An evidential reasoning geospatial approach to transport corridor susceptibility zonation

    Get PDF
    PhD ThesisGiven the increased hazards faced by transport corridors such as climate induced extreme weather, it is essential that local spatial hot-spots of potential landslide susceptibility can be recognised. Traditionally, geotechnical survey and monitoring approaches have been used to recognise spatially landslide susceptibility zones. The increased availability of affordable very high resolution remotely-sensed datasets, such as airborne laser scanning (ALS) and multispectral aerial imagery, along with improved geospatial digital map data-sets, potentially allows the automated recognition of vulnerable earthwork slopes. However, the challenge remains to develop the analytical framework that allows such data to be integrated in an objective manner to recognise slopes potentially susceptible to failure. In this research, an evidential reasoning multi-source geospatial integration approach for the broad-scale recognition and prediction of landslide susceptibility in transport corridors has been developed. Airborne laser scanning and Ordnance Survey DTM data is used to derive slope stability parameters (slope gradient, aspect, terrain wetness index (TWI), stream power index (SPI) and curvature), while Compact Airborne Spectrographic Imager (CASI) imagery, and existing national scale digital map data-sets are used to characterise the spatial variability of land cover, land use and soil type. A novel approach to characterisation of soil moisture distribution within transport corridors is developed that incorporates the effects of the catchment contribution to local zones of moisture concentration in earthworks. In this approach, the land cover and soil type of the wider catchment are used to estimate the spatial contribution of precipitation contributing to surface runoff, which in turn is used to parameterise a weighted terrain accumulation flow model. The derived topographic and land use properties of the transport corridor are integrated within the evidential reasoning approach to characterise numeric measures of belief, disbelief and uncertainty regarding slope instability spatially within the transport corridor. Evidential reasoning was employed as it offers the ability to derive an objective weighting of the relative importance of each derived property to the final estimation of landslide susceptibility, whilst allowing the uncertainty of the properties to be taken into account. The developed framework was applied to railway transport earthworks located near Haltwhistle in northern England, UK. This section of the Carlisle-Newcastle rail line has a ii history of instability with the occurrence of numerous minor landslides in recent years. Results on spatial distribution of soil moisture indicate considerable contribution of the surrounding wider catchment topography to the localised zones of moisture accumulation. The degrees of belief and disbelief indicated the importance of slope with gradients between 250 to 350 and concave curvature. Permeable soils with variable intercalations accounted for over 80% of slope instability with 5.1% of the earthwork cuttings identified as relatively unstable in contrast to 47.5% for the earthwork embankment. The developed approach was found to have a goodness of fit of 88.5% with respect to the failed slopes used to parametrise the evidential reasoning model and an overall predictive capability of 77.75% based on independent validation dataset.TETFUND Nigeria, Nasarawa State University and my family members for their financial support towards the completion of the PhD programme

    Railway Ecology

    Get PDF
    carbon footprint; environmental impacts of railways; transportation; wildlife; landscape; planning; engineering; efficiency; sustainability; biodiversity; animal casualties on rail

    Characterising soil moisture in transport corridors using remote sensing

    Get PDF
    This thesis assesses the ability of remote sensing techniques to characterise soil moisture in a transport corridor environment. Much of the world’s transport networks are built on earthwork embankments or in cuttings. In the UK, many of these earthworks were constructed in the mid-19th Century and are susceptible to slope instability. Instability in transport corridors is often triggered by an increase in pore pressure, which is directly influenced by an increase in soil moisture. Although a number of studies have investigated the use of remote sensing techniques for estimating soil moisture, they have tended to be conducted under controlled conditions and few have considered their capacity for being operational. This study addresses this point by exploring the use of high spatial resolution digital elevation models (DEMs) and airborne hyperspectral imagery for characterising soil moisture in transport corridors. A number of terrain (topographic wetness index (TWI), potential solar radiation, aspect) and spectral analysis (red edge position estimation, derivative stress ratios, continuum removal analysis, partial least squares (PLS) regression modelling, mapping biological indicator values) techniques were assessed using terrestrial systems over a test embankment, and airborne data for a transport corridor. The terrain analysis metrics TWI and potential solar radiation were found to be highly sensitive to the DEM spatial interpolation routine used, with a thin plate spline routine performing best in this study. This work also demonstrated that Ellenberg indicator values extended for the UK can be mapped successfully for transport corridor environments, providing potential for a number of different applications. Individually, the techniques were shown to be generally poor predictors of soil moisture. However, an integrated statistical model provided an improved characterisation of soil moisture with a coefficient of determination (R2) of 0.67. Analysis of the model results along with field observations revealed that soil moisture is highly variable over the transport corridor investigated. Soil moisture was shown to increase in a non linear fashion towards the toe of earthwork slopes, while contribution from surrounding fields often led to concentrations of moisture in cutting earthworks. Critically, while these patterns could be captured using the data investigated in this study, such spatial variability is rarely taken into account using analytical slope stability models, potentially raising important challenges in this respect.EThOS - Electronic Theses Online ServiceEngineering and Physical Sciences Research Council (EPSRC)GBUnited Kingdo

    Innovative Methods and Materials in Structural Health Monitoring of Civil Infrastructures

    Get PDF
    In the past, when elements in sructures were composed of perishable materials, such as wood, the maintenance of houses, bridges, etc., was considered of vital importance for their safe use and to preserve their efficiency. With the advent of materials such as reinforced concrete and steel, given their relatively long useful life, periodic and constant maintenance has often been considered a secondary concern. When it was realized that even for structures fabricated with these materials that the useful life has an end and that it was being approached, planning maintenance became an important and non-negligible aspect. Thus, the concept of structural health monitoring (SHM) was introduced, designed, and implemented as a multidisciplinary method. Computational mechanics, static and dynamic analysis of structures, electronics, sensors, and, recently, the Internet of Things (IoT) and artificial intelligence (AI) are required, but it is also important to consider new materials, especially those with intrinsic self-diagnosis characteristics, and to use measurement and survey methods typical of modern geomatics, such as satellite surveys and highly sophisticated laser tools

    Geotechnical asset management for climate change risk

    Get PDF
    Geotechnical asset management is a process and tool which encourages robust data management, optimised programming and evidenced based decision-making. Although asset management has come a long way since becoming a more accepted practice in the highways sector , and has fundamentally changed the way that assets are maintained, there are aspects that are still evolving as clarity on asset and network need improves and extends into future years. However, in gaining more sight into the future of asset networks, unforeseen risks begin to appear. These risks may not have been known or well understood at the time the asset network was constructed, or may not have been an issue when the asset was originally designed, yet, over the years the changing use of the asset network by users has led to new risks becoming apparent. One of these historically unknown risks is climate change. While knowledge about how climate change is expected to impact assets is improving, the understanding of the scale and scope of assets that will be affected by climate change is less well developed. The tool presented in this research is a risk assessment, which evaluates the risk profile of the effects of climate change on a geotechnical asset as the result of the critical condition impact factors. This risk profile is completed by a scoring the impacting factors on a scorecard, for subsequent inclusion in the final risk score. The likelihood element of the risk assessment uses probability scores taken from the medium emission scenarios presented by the UKCIP 2018. The resultant risk score can then be utilised as a forward planning tool for maintenance, or increased monitoring, where appropriate. Three case studies were assessed to show the practical application of the system. The results of the case studies show that the process works and produces results which aid the planning of maintenance to mitigate for climate change
    • 

    corecore