10 research outputs found
Performance parameters and target values for construction of UK road foundations
There is impetus in the UK to move away from empirical design of road foundations and method specification towards analytical design assured by end product testing during construction. Current research at Loughborough University, sponsored by the Highways Agency, is aimed at introducing such a performance based specification. This paper introduces the philosophy behind the research and explains the primary objectives. Selective results are presented from a full-scale field trial construction of a road foundation on a soft subgrade, which was characterised by a variety of field devices and subsequently trafficked. This paper focuses on insitu stiffness modulus (ER), measured by several devices for comparison. The setting of suitable target values for field ER is seen as a key factor and the influence of inherent variability in material response a concern. The discrepancy between devices and the problem of long-term stability are discussed and highlighted as a key focus for the remainder of the work
Threshold stress and asymptotic stiffness of UK clays in the repeated load triaxial test.
Recent research at Loughborough University has produced a draft performance
specification for pavement foundations. To assess the performance parameters of stiffness and resistance
to permanent deformation of the subgrade, an extensive series of repeated load triaxial
tests has been performed on a range of fine grained subgrades. Assessment of the data has shown
that the deviator stress at which the cumulative permanent deformation starts to increase significantly
(i.e. the threshold stress) is equal to half that at failure (and occurs at approximately 1%
permanent strain). The resilient stiffness of the materials tends to low asymptotic values at higher
deviator stress. Comparison between the elastic and plastic behaviour has shown that the deviator
stress at ‘threshold’ is coincident with the stiffness asymptote. This paper presents a suggested
simplified mechanistic design approach for pavement foundations based on these findings
Stiffness behaviour of trial road foundations.
This paper reports the results of two full-scale field trials to determine the stiffness and density
of granular materials receiving different levels of compaction energy and support. The research showed that
there were greater improvements in density with initial input of compaction energy, and yet little change in
density, but significant increases in stiffness, with the final applications of compaction energy. Density is
thus an inappropriate indicator of performance (i.e. resilient elastic stiffness
Workplace parking levies: the answer to funding large scale local transport improvements in the UK?
Despite positive experiences in Australia of utilising area wide workplace parking place
charges to pay for public transport improvement, only one UK local authority, to date,
Nottingham City Council has chosen to implement a Work Place Parking Levy scheme
(WPL). This scheme intends to allocate the revenue raised to fund (amongst other things)
two new tram lines.
Acceptance by the public and the business community are seen as key barriers to
implementing a WPL. The two major criticisms of the Nottingham scheme prior to its
implementation were that a WPL would discourage business investment and thus damage
the economy while its intended impact on traffic congestion would be minimal.
Therefore a detailed assessment of the Nottingham WPL scheme’s performance is essential
in order to facilitate transferability of this approach to other UK and European Cities and thus
bring WPL into the mainstream for funding transport improvements.
This paper outlines the barriers to implementation of the Nottingham WPL scheme, and the
rationale behind the chosen use of revenue and how the scheme’s performance will be
evaluated as a transport demand management measure, as well as some initial performance
monitoring data following the first year of operation.
The results to date are discussed with a view to identifying any early indications as to
whether traffic congestion and business investment has been impacted by the scheme’s
introduction
Stakeholder views of materials selection for road pavements
The growing prominence of Carbon calculators in the road construction sector has lead to a greater
general awareness of the sustainability issues associated with road pavement materials and their
selection. This paper presents results from a series of semi-structured interviews conducted with key
stakeholders from the highways industry, which were used to gain an understanding of industry
perceptions on the use of sustainability assessment in the selection of highway materials for road
construction.
The stakeholders consulted ranged from government bodies and trade associations to contractors and
academics. Analysis of the interviews has shown that there is a clear focus on Carbon/Climate change.
The frequency with which various topics were mentioned has been used in the analysis to produce a
basic hierarchy of sustainability drivers for the highways industry. A comparison is also made against
the existing civil engineering environmental quality assessment and award scheme (Ceequal) categories
to identify gaps and areas of consensus to further enhance Ceequal. The paper concludes that several
factors should be taken forward within any on-going development of LCA (Life Cycle Assessment) frameworks or Carbon assessment methodologies for road construction projects including, Carbon
(footprinting)/Climate change, Maintenance phase considerations and broader Environmental Issues
Subgrade equilibrium water content and resilient modulus for UK clays
The main functional requirement of the subgrade is to resist excessive
deformations during construction and in service. Deformation is controlled by ensuring
adequate foundation resilient modulus. UK pavement design currently relies upon the
determination of long-term CBR values for subgrades, which results in conservative
pavement foundation design. To allow more realistic design an analytical approach is
required, including measured values of resilient modulus at anticipated short- and long-term
equilibrium subgrade water contents. Resilient modulus is determined from repeated load
triaxial tests with on-sample strain measurement. Results from these tests on samples
adjusted to model the subgrade behaviour at various design conditions are presented.
These results are discussed, highlighting problems both with measuring small strains on
undisturbed soils and in predicting and modelling accurately long-term soil behaviour.
RÉSUMÉ: Le critère principal d’une sous-couche est de résister à des déformations
excessives en construction puis en service. La conception des chaussées au Royaume-Uni
est actuellement basée sur la détermination de l'indice portant Californien (CBR) à longterme
des sous-couches. Pour une conception plus réaliste, il est nécessaire d'adopter une
approche prenant en compte des valeurs de module de résilience mesurées à des degrés
d'humidité de sous-couches à l'équilibre simulés à court et long-terme. Le module de
résilience est déterminé à partir d'essais répétés en charge triaxiale avec mesure des
contraintes sur l'échantillon. Dans cet article les résultats de ces tests sur des échantillons
simulant le comportement de la sous-couche sous diverses conditions de conception sont
présentés. Ces résultats sont discutés, en soulignant les problèmes résultant de la mesure
de faibles contraintes sur des sols non-perturbés, et dus à la prédiction et à la modélisation
du comportement des sols à long-terme
Insitu assessment of stiffness modulus for highway foundations during construction
Several portable field devices that measure stiffness modulus are reviewed in detail in
this paper including the German Dynamic Plate Test (also known as the Lightweight Drop Tester),
the TRL foundation tester (UK), the Prima (Denmark) and the Humboldt Soil Stiffness Gauge
(USA, also known as the GeoGauge). Laboratory and field data are presented which explain the
many important influences on the measured data and demonstrate comparative performance with
respect to the Falling Weight Deflectometer. These field data show significant scatter and site
specific correlation. A strategy for compliance testing during construction, as part of a performancebased
specification approach for the UK, is suggested. Conclusions are made regarding the devices’
relative merits and limitations, and considerations for their introduction into contractual use for
routine assessment during construction
Drainage behavior of sports pitches–A case study review
The drainage behavior of sports pitches has
traditionally been designed from experience
with hydraulic performance rarely measured
in detail. Within the wider industry and regulatory bodies there is a perception that storm water and increased drainage rates from sports pitches contribute to local flood risk. Empirical observations have suggested that in reality pitch drainage systems may discharge water at low volumes and rates and there is often limited surface run-off. Furthermore it appears that lack of technical guidance on the discharge of water from sport pitch drainage systems may have led to misunderstanding their drainage behavior and possible benefits they could bring to water management as opposed to perceived dis-benefits. This paper summarizes selected results of a case study which included field measurements of weather and discharge behavior on a range of natural turf sports pitches in England. The findings from this study indicate that natural turf sports pitches can provide resistance to flow and hence advantageous attenuation of rainfall
and storm water. Additionally sports pitches can store large volumes of water within the pervious materials used in their design. The study has confirmed that sport pitches demonstrate the key functions that are reflected in the design requirements of Sustainable Urban Drainage Systems (SuDs) such as pervious pavements providing source control of surface rain water
The performance of pavement foundations during construction
There is an impetus in the UK to move away from empirical pavement foundation design
and the current method specification, towards an analytical design approach. For an
analytical design approach to be adopted, the required performance properties of stiffness
and resistance to permanent deformation of the foundation materials (sub grade and
capping) need to be measured, both in the laboratory for design and in the field in order
to ensure compliance.
This thesis studies the influence of the sub grade on the constructability and performance
of a series of full-scale pavement foundations. This has been achieved by measuring the
performance parameters of several sub grade materials in the laboratory, using repeated
load triaxial testing. These data have been compared to comparable data collected in situ
using dynamic stiffness measuring devices during the construction of trial pavement
foundations. The performance of the trial foundations has been measured during the
placement and compaction of the different foundation materials, and again after their
subsequent trafficking.
The testing demonstrates the stress dependency of the foundation materials. The
laboratory testing shows that the sub grade permanent deformation under cyclic loading
(used to simulate construction operations) becomes unstable at a deviator stress of half
the deviator stress at failure (0.5qmax)· The stiffness at this applied stress and above is
shown to be approaching a consistent value. This indicates that large changes in the
stiffness of inversely stress dependent fine grained soils occur below the deviator stress at
which the permanent deformation becomes unstable. Significant variability of data has
been found in the performance parameters measured (both in the laboratory and in the
field) for samples of subgrade collected from small areas of the same site. However
comparable patterns of stress dependency have been observed between measured
laboratory and field performance using the different apparatus.
The resistance to permanent deformation is shown to be a more critical design load case
for construction than the need for adequate stiffness of support required to compact the
foundation layers. The performance of a composite road foundation is shown to be
material and site specific, and this will have important implications for design and site
compliance testing
A case study on evaluating and selecting soil /pipeline interaction analysis software for the oil and gas industry
The evaluation and selection of appropriate software solutions to meet an organisation’s inherent business requirements can be a problematic process that if done incorrectly can have a significant, costly and adverse effect on the business and its processes. The aim of this paper is to showcase a process and evaluation criteria in order to identify the right engineering software for the identified business requirement such as functionality and usability. A case study approach coupled with an action-based research methodology was undertaken to aid an organisation within the Oil and Gas Industry, by using an innovative solution suitable for conducting stress analysis for Soil-Pipeline Interaction Analysis (SPIA). Through development and use of the below presented software selection and evaluation process to capture and measure key requirements, it was possible to determine a viable approach to selection of a suitable software for the organisation’s requirements. This paper investigates software evaluation criteria for evaluating software packages and methodologies for selecting software packages. The study will also provide an explanation of the adopted methodology. The key findings of the study are: (1) there is currently no universal selection criteria within the gas and oil engineering industry, (2) how the presented methodology could be used to capture business requirements to evaluate software for SPIA consultants (3) findings must be validated based on the evaluation technique and evaluation criteria for selecting software packages for the engineering industry. The findings of the study are offered to support consultants in the Oil and Gas industry to improve software selection methodologies for SPIA