Journal Articles by Paul J Vardanega
Canadian Geotechnical Journal, 2024
This note presents the application of the mobilisable strength design (MSD) method to the monitor... more This note presents the application of the mobilisable strength design (MSD) method to the monitoring results of the multipropped excavation in the south area of the British Library Euston, constructed in a highly overconsolidated stiff clay deposit. The MSD method is an energy-based approach (a nonlinear finite-element method for a single-degree-of-freedom soil-wall system) introduced to develop a simplified design methodology that satisfies both ultimate and serviceability limit states. Wall displacement predictions based on the MSD method are compared with considerable field monitoring data. The sensitivity of the method to reasonable variations in input parameters is considered. A spreadsheet and python code demonstrating the MSD analysis from this paper are provided in the online supplement alongside details of the mathematical formulation.
Infrastructure Asset Management, Jun 16, 2023
The visual inspection of bridges is a major undertaking for asset owners and operators. In the UK... more The visual inspection of bridges is a major undertaking for asset owners and operators. In the UK, visual inspections require inspectors to visit bridges on-site and often at night and in unfavourable weather conditions. Therefore, it would be beneficial to move some of the visual inspection process off-site. This paper studies whether the defect classification aspects of the inspection process could be conducted remotely using photographs. This study examines the defect ratings assigned by ten survey participants who were tasked with examining photographs from visual inspections of ten UK bridges. The survey results were compared with the results from the general inspections previously carried out for the bridges in question. From this dataset, the differences in the ratings given and the extent to which defects are missed were examined. The results show that a higher number of defects were identified for a given bridge by the remote inspectors. Statistical analysis shows that aggregated defects rated by off-site inspectors tend to be more severe and of a higher priority rating compared to those from the on site inspectors. The results also indicate that there is closer agreement between on-site and off-site inspectors for defects of a higher severity rating.
Proceedings of the Institution of Civil Engineers – Bridge Engineering, 2022
Visual inspection remains key for assessing the condition of bridges and hence assisting with pla... more Visual inspection remains key for assessing the condition of bridges and hence assisting with planning and
maintenance activities. There have been many efforts to improve or supplement visual inspection processes using new sensing technologies and data capture methods to usher in an era of ‘smart bridges’ or ‘smart infrastructure’. One method to improve data capture is a ‘remote inspection’ where inspectors use digital photographs of a bridge to identify and grade structural defects to the standard of a ‘general inspection’. In this paper, survey data are presented to help formulate a preliminary assessment of the potential for engineers to implement this possible evolution of the visual inspection process. A potential schema for remote visual inspections is developed and presented as a conceptual web application. The focus on the development of the schema includes the need for ease of use by inspectors and integration of collected digital data into bridge management systems. The suggested platform is seen as a transitional method to aid in the long-term implementation of further automation of the inspection process. The system architecture is provided along with possible technologies that may support or enhance it, as well as a discussion of the potential barriers to implementation.
Sustainable and Resilient Infrastructure, Mar 15, 2023
Scour is a significant cause of bridge failure, and resulting bridge closures are likely to gener... more Scour is a significant cause of bridge failure, and resulting bridge closures are likely to generate significant disruption to infrastructure networks. The management of scour-susceptible bridges is a significant challenge for improving transport resilience, but tends to be heuristic and qualitative. Such assessments often suffer from insufficient knowledge of key factors and require assumptions, which may increase their estimation and relative uncertainty. Analysis of publicly available technical documents reveals that various definitions of “risk” are adopted, as well as multiple approaches are applied. This paper has three objectives: (i) to illustrate the concept of risk in bridge scour management; (ii) to propose a simple scoring system to analyse existing risk-based approaches to manage bridge scour; and (iii) to analyse and compare such approaches on the basis of the obtained scores. A sample of nine documents containing bridge scour risk assessment practices or approaches was analysed using the developed rating system.
Cold Regions Science and Technology, Sep 1, 2023
This paper presents laboratory data from tests on four fine-grained soils: reconstituted Kaolinit... more This paper presents laboratory data from tests on four fine-grained soils: reconstituted Kaolinite, destructured Bothkennar clay, reconstituted Bothkennar clay, and reconstituted Gault clay. The soil samples were conditioned in an oedometer cell while being subjected to varying numbers of freezing and thawing cycles. The influence of freeze-thaw cycles on key soil parameters, including the hydraulic conductivity, Atterberg limits, compression and swelling index was studied. The experimental results were then compared with the analysis of a previously published database of hydraulic conductivity measurements on fine-grained soils called FG/KSAT-1358. The paper demonstrates that while multiple cycles of freezing and thawing affect some of the studied soil parameters, such as the Atterberg limits and the compression characteristics, the effects on the hydraulic conductivity transformation model parameters, linking the water content ratio to hydraulic conductivity are less apparent. The results are useful for geotechnical and pavement engineers when making assessments of freeze-thaw effects on subgrade materials in cold regions.
Transportation Geotechnics, Jul 1, 2023
This paper reviews commonly used parameters and prediction models for assessing the permeability ... more This paper reviews commonly used parameters and prediction models for assessing the permeability of granular soils. Following a review of published models for prediction of soil permeability, a dimensional homogenous transformation model for a-priori estimation of soil permeability was calibrated using a large database (CG/ KSAT/7/1278) comprising permeability data for a wide range of granular soils sourced from over 50 publications. The new transformation model requires knowledge of the void ratio and gradation of the material to make estimates of the soil permeability. The prediction accuracy of the calibrated model was then assessed alongside that of other empirical and semi-empirical models also calibrated using CG/KSAT/7/1278. The potential influences of void ratio, key gradation parameters and permeability test type on the prediction accuracy of the proposed model are also examined. The paper shows that while the fitted constants in the proposed transformation model are affected to varying extents by the aforementioned parameters, it does offer reasonable predictions of permeability with only knowledge of the void ratio and material gradation required.
Proceedings of the Institution of Civil Engineers - Forensic Engineering, 2022
The UK has a large stock of highway bridges that is ageing and deteriorating. This paper presents... more The UK has a large stock of highway bridges that is ageing and deteriorating. This paper presents the results of a programme of work to understand the reliability of the visual inspection data that are used to inform the management of Highways England’s structures. This paper presents a data set comprising evidence collected during the presence of research team inspectors at the principal inspection and/or testing of 200 bridges randomly sampled from Highways England’s bridge network, coupled with asset-management data for Highways England’s entire bridge stock. Recommendations are made for future improvements in visual inspection practice and use of such data in future asset-management efforts.
Bulletin of the Seismological Society of America, Dec 2022
The time-averaged shear-wave velocity in the upper 30 m (VS30) is widely used as a proxy for site... more The time-averaged shear-wave velocity in the upper 30 m (VS30) is widely used as a proxy for site characterization in building codes. Regional estimations of VS30 often use either slope-based, terrain-based, or geological approaches as a proxy. This technique has proven useful at a number of locations globally, and slope-based estimates formed the basis of the original global VS30 model implemented by the U.S. Geological Survey. Geostatistical models involve the study of potentially spatially correlated parameters. Modeling challenges arise when parameters are scarce or uncertain, and traditional geostatistical workflows cannot be implemented in all settings. In this study, the benefits of the spatial extents of VS30 proxies are used to supplement local data to implement a methodology for improving estimates using a multi-Gaussian Bayesian updating framework. This methodology is presented in the context of a data-scarce region, specifically, the Kathmandu Valley in Nepal. Using geostatistical approaches typically used by the petroleum industry, this article develops a novel practice-oriented framework for VS30 estimation that can be adapted for use on a region-by-region basis. This framework provides an informed estimate and assessment of the uncertainties in which quantification of VS30 is required in geotechnical earthquake engineering applications.
Georisk: Assessment and Management of Risk for Engineered Systems and Geohazards, Dec 20, 2022
The availability of reliable field data is critical for the advancement of geotechnical engineeri... more The availability of reliable field data is critical for the advancement of geotechnical engineering. This is particularly the case for piled foundations; due to the substantial geotechnical uncertainties. The settlement (performance) predictions from established analytical methods may deviate from field measurements by as much as an order of magnitude. This paper provides a statistical assessment of the uncertainty of predictions of pile performance under axial loading using an openly accessible geotechnical database of pile load tests from the United Kingdom. The collected database information was classified by pile type, location, test data quality and availability of geotechnical data. With reference to the data from fine-grained soils, two analytical models were employed to predict foundation settlement. The settlement prediction performance was then studied statistically and the model bias and error compared with reference to the aforementioned categories to identify the impact of different sources of uncertainty and evaluate the use of both models for future geotechnical practice. The two models investigated generally over-predict settlement, which is likely due to conservative selection of key model parameters, such as soil strength.
Journal of Geotechnical and Geoenvironmental Engineering, May 6, 2022
Estimation of nonlinear pile settlement can be simplified using one-dimensional "t-z" curves that... more Estimation of nonlinear pile settlement can be simplified using one-dimensional "t-z" curves that conveniently divide the soil into multiple horizontal "slices." This simplification reduces the continuum analysis to a two-point boundary-value problem of the Winkler type, which can be tackled by standard numerical procedures. Theoretical "t-z" curves can be established using the "shearing-of-concentric cylinders" theory of Cooke and Randolph-Wroth, which involves two main elements: (1) a constitutive model cast in flexibility form, γ =γ(τ); and (2) an attenuation function of shear stress with radial distance from the pile, τ =τ(r). Soil settlement can then be determined by integrating shear strains over the radial coordinate, which often leads to closed-form solutions. Despite the simplicity and physical appeal of the method, only a few theoretical "t-z" curves are available in the literature. This paper introduces three novel attenuation functions for shear stresses, inspired by continuum solutions, which are employed in conjunction with eight soil constitutive models leading to a set of 32 "t-z" curves. Illustrative examples of pile settlement calculation in two soil types are presented to demonstrate application of the method.
Géotechnique, Jul 2022
Use of the Casagrande-style plasticity chart to classify fine-grained soils using Atterberg’s liq... more Use of the Casagrande-style plasticity chart to classify fine-grained soils using Atterberg’s liquid and plastic limits is ubiquitous in geotechnical engineering. This classification is dependent on the thread-rolling and Casagrande-cup tests, which are both more operator dependent than the fall-cone liquid limit test. This paper shows that the slope of the data acquired during the fall-cone liquid limit test (the fall-cone flow index) can be used to redraw the plasticity chart, thus allowing classification of fine-grained soils to be achieved solely from fall-cone liquid limit data.
Proceedings of the Institution of Civil Engineers – Bridge Engineering, Feb 16, 2022
During bridge design and assessment, effects of thermal actions are accounted for by means of a u... more During bridge design and assessment, effects of thermal actions are accounted for by means of a uniform temperature variation and temperature difference components. The uniform temperature variations cause changes in length and width of the structure, whereas the temperature difference components primarily cause curvatures and internal stresses. The effects of these strains on the superstructure depend on the structure's articulation and restraint. Design profiles used to model the temperature difference components vary between design codes, which can have a significant effect on the induced curvatures. Thermal data findings obtained from a comprehensive, year-long monitoring programme on Waterloo Bridge in London are examined, which allows comparison of these various models with performance data. The design thermal model in BS EN 1991-1-5 is examined, supplemented by the models from the AASHTO and New Zealand codes. The measured uniform bridge temperature generally fell within the stipulated limits of BS EN 1991-1-5; however, at low temperatures the minimum deck temperature may be lower than the design relationship provided. The resultant moments implied from the measured vertical profiles: significantly exceed the worst-case values predicted by the UK model; exceed the AASHTO model at different bridge sections; and do not exceed the New Zealand model.
Bulletin of Earthquake Engineering, Jan 1, 2022
An assessment of liquefaction potential for the Kathmandu Valley considering seasonal variability... more An assessment of liquefaction potential for the Kathmandu Valley considering seasonal variability of the groundwater table has been conducted. To gain deeper understanding seven historical liquefaction records located adjacent to borehole datapoints (published in SAFER/GEO-591) were used to compare two methods for the estimation of liquefaction potential. Standard Penetration Test (SPT) blowcount data from 75 boreholes inform the new liquefaction potential maps. Various scenarios were modelled, i.e., seasonal variation of the groundwater table and peak ground acceleration. Ordinary kriging, implemented in ArcGIS, was used to prepare maps at urban scale. Liquefaction potential calculations using the methodology from (Sonmez, Environ Geol 44:862-871, 2003) provided a good match to the historical liquefaction records in the region. Seasonal variation of the groundwater table is shown to have a significant effect on the spatial distribution of calculated liquefaction potential across the valley. The less than anticipated liquefaction manifestations due to the Gorkha earthquake are possibly due to the seasonal water table level.
Proceedings of the Institution of Civil Engineers - Forensic Engineering, Dec 2021
Bridge scour is a complex bridge-management problem. It is also a difficult forensic engineering ... more Bridge scour is a complex bridge-management problem. It is also a difficult forensic engineering challenge, as the greatest risk occurs during large flows and flood events, when visual inspection of the bridge piers is often not possible. This paper presents a review of scour prediction and modelling methods, whose results are used to determine the key parameters that scour-monitoring systems need to capture. Then, a review of existing monitoring approaches and technologies for scour monitoring is presented. The paper concludes with the proposal of a novel rating system for evaluating different scour-monitoring techniques. The new rating system is trialled ex-post for seven previously published bridge-scour-monitoring case studies to illustrate the use of the new methodology.
Journal of Unmanned Vehicle Systems, Jun 2021
Aerial robotic technology has potential for use in a wide variety of civil engineering applicatio... more Aerial robotic technology has potential for use in a wide variety of civil engineering applications. Such technology potentially offers low-cost methods to replace expensive structural health monitoring activities such as visual inspection. Aerial robots also have potential uses in civil construction and for regional surveys. This paper presents the results of a review on the applications of aerial robotic technology in civil engineering. Such civil engineering applications can be classified into three broad areas: (i) monitoring and inspection of civil infrastructure; (ii) site management, robotic construction, and maintenance; and (iii) post-disaster response surveys and rapid damage assessments. The motivations for uptake of aerial robotics in the civil engineering industry generally fall into the following categories: (i) cost savings, (ii) improved measurement capability, and (iii) safety improvements. The categories of aerial robotic use in civil engineering are then classified as either “established” or “emerging” uses.
Frontiers in Built Environment, May 7, 2021
Seismic hazard assessment often relies on static piezocone penetration tests (CPTu) to estimate t... more Seismic hazard assessment often relies on static piezocone penetration tests (CPTu) to estimate the cyclic resistance ratio (CRR) and for the evaluation of in situ soil behavior. This article presents CPTu data acquired in the Kathmandu valley sediments and makes use of established CPTu interpretation procedures to assess the soil in situ properties. Up to this point predominantly SPT data and limited shear wave velocity measurements have been relied upon to assess the variability and seismic response of soil deposits underlying Kathmandu. This article provides 1) additional data to add to the existing SAFER/GEO-591 database, 2) new shear-wave velocity measurements, and 3) initial estimates of CRR at the sites visited. Based on the work presented in this article, it is concluded that a more detailed methodology is needed for liquefaction assessment mainly due to the presence of saturated silts in the valley.
Earthquake Spectra, May 1, 2021
Geostatistical methods are valuable to better understand the spatial distribution of geotechnical... more Geostatistical methods are valuable to better understand the spatial distribution of geotechnical parameters at regional scale and to optimize the locations of future ground investigations. This article investigates the use of the kriging interpolation method to extend the knowledge of a specific geotechnical property from a few sites to a broader geographical area with a focus on the Kathmandu valley (Nepal). A Bayesian form of kriging is proposed in this article. The estimation of the shear wave velocity in the uppermost 30 m of soil (V S30) in the Kathmandu valley is examined. Slope-based V S30 estimates from the United States Geological Survey are used as prior information, and 15 V S30 measurements are used as more precise data. Considering the limited number of high-quality V S30 measurements available in the valley, it is shown that the Bayesian scheme can lead to a more robust estimation of V S30 than that obtained with the ordinary kriging approach. A methodology for conditioning prior low-precision data to the measurements is also presented.
Quarterly Journal of Engineering Geology and Hydrogeology, 2021
The sharing of ground investigation (GI) data within the UK is commonly practised only in large i... more The sharing of ground investigation (GI) data within the UK is commonly practised only in large infrastructure projects. A vast amount of GI data collected on routine projects is commonly not made publicly available which is arguably inefficient and potentially unsustainable. This paper captures the opinions of the geoscience community and the GI industry on data sharing to better understand current working practices and potential barriers to data sharing. The results of a survey carried out at the Janet Watson Meeting 2018: A Data Explosion: The Impact of Big Data in Geoscience held at the Geological Society of London are reported. This survey is compared with the results of interviews undertaken during the Dig to Share project, a collaborative project led by Atkins, British Geological Survey (BGS) and Morgan Sindall. The opinions and practices of geoscientists towards data sharing across a project life cycle are reviewed. Drivers of risk relating to geotechnical aspects of a project are directly linked to current data sharing practice.
Transportation Engineering, Mar 1, 2021
A new database called AC/k-1624 containing over 1600 measurements of saturated hydraulic conducti... more A new database called AC/k-1624 containing over 1600 measurements of saturated hydraulic conductivity of asphalt concrete has been assembled and analysed. AC/k-1624 was used to investigate the effect of the grading entropy parameters on saturated hydraulic conductivity. A new prediction model comprising both air voids and grading entropy is presented. The database analysis using different predictors of asphalt hydraulic conductivity reveals that the gradation does affect the hydraulic conductivity, but the air void level is necessary to make reasonable a-priori assessments of hydraulic conductivity for asphalt concrete. The new empirical model is shown to have a good predictive capacity for hydraulic conductivity fitting more securely at higher values with more scatter observed at lower values. The effects of test type, gradation classification and Nominal Maximum Aggregate Size (NMAS) are also studied, revealing in general relatively modest influences on the computed regression coefficients.
Proceedings of the Institution of Civil Engineers - Bridge Engineering, Nov 18, 2020
Considerable amounts of data are collected on the UK’s stock of bridges. Much of this data is col... more Considerable amounts of data are collected on the UK’s stock of bridges. Much of this data is collected to inform the planning and scope of maintenance activities. This paper reports on the results of a series of semi-structured interviews with 17 individuals involved in UK bridge asset management and data-collection activities to explore how such data is used in practice. A wide spectrum of organisations and industrial sectors was represented in this dataset. Hierarchical process modelling was used to characterise the UK’s bridge management system and define the processes and sub-processes involved in the management of bridges. Key quotations are used from the interviews to reveal the state of data collection and use in UK bridge infrastructure from the perspective of those directly involved. The study concludes that there is significant variation within the industry regarding the use of visual inspection data and that formal structural health monitoring remains relatively rare. Furthermore, there is a need to develop a new unifying paradigm that will frame the efficient and effective application of emerging artificial intelligence and data science enabled (i.e. ‘smart’) condition-monitoring techniques to bridge management.
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Journal Articles by Paul J Vardanega
maintenance activities. There have been many efforts to improve or supplement visual inspection processes using new sensing technologies and data capture methods to usher in an era of ‘smart bridges’ or ‘smart infrastructure’. One method to improve data capture is a ‘remote inspection’ where inspectors use digital photographs of a bridge to identify and grade structural defects to the standard of a ‘general inspection’. In this paper, survey data are presented to help formulate a preliminary assessment of the potential for engineers to implement this possible evolution of the visual inspection process. A potential schema for remote visual inspections is developed and presented as a conceptual web application. The focus on the development of the schema includes the need for ease of use by inspectors and integration of collected digital data into bridge management systems. The suggested platform is seen as a transitional method to aid in the long-term implementation of further automation of the inspection process. The system architecture is provided along with possible technologies that may support or enhance it, as well as a discussion of the potential barriers to implementation.
maintenance activities. There have been many efforts to improve or supplement visual inspection processes using new sensing technologies and data capture methods to usher in an era of ‘smart bridges’ or ‘smart infrastructure’. One method to improve data capture is a ‘remote inspection’ where inspectors use digital photographs of a bridge to identify and grade structural defects to the standard of a ‘general inspection’. In this paper, survey data are presented to help formulate a preliminary assessment of the potential for engineers to implement this possible evolution of the visual inspection process. A potential schema for remote visual inspections is developed and presented as a conceptual web application. The focus on the development of the schema includes the need for ease of use by inspectors and integration of collected digital data into bridge management systems. The suggested platform is seen as a transitional method to aid in the long-term implementation of further automation of the inspection process. The system architecture is provided along with possible technologies that may support or enhance it, as well as a discussion of the potential barriers to implementation.
The Authors have presented an interesting paper (Hrubesova et al., 2020), which aims (in part) to validate the Moharjerani (1999) calibration approach for establishing the 80 g/30◦ fall-cone penetration depth equating to the liquid limit by the Casagrande percussion-cup approach, determined according to the British Standard. In this paper, the Discussers present some clarifications on, and state various observations regarding, the approaches adopted in the Hrubesova et al. (2020) investigation, as well as the Moharjerani (1999) calibration approach employed therein. The Discussers also present a description of some relevant literature not covered in the Authors’ paper (Hrubesova et al. 2020) aimed at making further clarifications on this important area of geotechnical practice.