Andrew Dawson

Andrew Dawson
AHH Enterprises · Consultancy

About

242
Publications
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Publications

Publications (242)
Article
In this study, a new three-dimensional (3D) reinforcement element comprising a horizontal ring connected to the vertical legs is introduced. A series of 1g laboratory scale tests were conducted on a circular footing that rested on a sand bed containing planar or new 3D-reinforcements. The effects of depth of first layer, reinforcements configuratio...
Article
Full-text available
Reclaimed asphalt pavement (RAP) and blends of RAP with virgin aggregate (VA) were characterized in this study to be utilized as base course aggregate. Multi-stage and single repeated load triaxial (RLT) tests were conducted in the laboratory to characterize the materials. The results from these tests were used to develop a mechanistic design appro...
Article
Protecting sensitive and/or valuable facilities is of concern when placing them near a machine foundation. There are methods available and well-studied such as wave barriers to reduce transmitted vibration and noises in the vicinity of a vibration source. Wave barriers are feasible to protect objects that are far enough from the vibration sources b...
Article
In this paper, an impulse-based Discrete Element numerical Method (iDEM) included in a physics toolbox, has been used to compact virtual aggregates. Firstly, geometrical properties, such as area, aspect ratio, perimeter, minor and major feret, circularity and roundness, of eleven types of coarse aggregates were measured. Then, a mass of each of the...
Article
In many applications, geotextiles are subjected to dynamic loading conditions, for example, below roads and railways, for which a Gradient Ratio (GR) test is often used to assess filtration compatibility of soil-geotextile systems. This paper presents results from GR filtration tests with internally-stable and -unstable soils under dynamic loading...
Chapter
Water content is one of the causes of railway tracks’ poor performance. Implementing its effects into design and management numerical tools is not always straightforward because the relevant descriptive partial differential equations (PDEs) involved are highly nonlinear. The paper describes the creation of a surrogate model to predict water flow in...
Article
Full-text available
This study proposes reusing post-consumer soil-filled PET (polyethylene terephthalate) bottles as a novel soil reinforcing element by conducting a laboratory-scale experimental investigation. The concept is that the polymer bottle walls act to confine the interior soil so that the bed behaves somewhat like a brick-built load spreading zone. The soi...
Article
It is crucial to accurately predict the resilient modulus of subgrade soils. The modulus is influenced by a soil’s properties, as characterised by the soil’s moisture index values. Thus, it may be feasible to predict resilient modulus based on the soil index. Consistency index, as one of the common soil indices, incorporates plasticity index and mo...
Article
A B S T R A C T Arya and Paris developed a model in 1981 to predict the water retention curve of a soil from the grain size distribution and the porosity. This model was very convenient due to the simplicity of the input parameters, and because experimental measures are expensive and with no lack of uncertainties. The model was based on very simple...
Preprint
Full-text available
Background SARS-CoV-2 variants of concern (VOCs) have been associated with higher rate of transmission, and evasion of immunisation and antibody therapeutics. Variant sequencing is widely utilized in the UK. However, only 0.5% (~650k) of the 133 million cumulative positive cases worldwide were sequenced (in GISAID) on 08 April 2021 with 97% from Eu...
Article
Full-text available
An algorithm to re-create virtual aggregates with realistic shapes is presented in this paper. The algorithm has been implemented in the Unity 3D platform. The idea is to re-create realistically the virtual coarse and crushed aggregates that are normally used as a material for the construction of roads. This method consists of two major procedures:...
Article
The precise, quick and efficient simulation of asphalt concrete is an important step to select asphalt mixtures for a range of applications. A method to create virtual aggregates based on aggregates' topological properties and aggregate skeletons like those of asphalt concrete using a physics engine is proposed. It can produce hundreds of virtual a...
Article
Full-text available
Newly laid asphalt must be adequately cool before it can be trafficked to prevent the development of costly premature damage. Selecting an appropriate traffic-opening temperature of newly laid asphalt airport runway overlay would avoid early damage – while also minimising the disruption to the airport service due to prolonged runway closure in a bu...
Article
In this study, the efficiency of employing rubber sheets to modify the dynamic response of a concrete machine foundation model of size 400 × 400 mm is explored by conducting a series of steady-state vertical vibration tests. Rubber is a low-cost energy dissipater material having high resistance to erosion which can be used in a form of sheets and s...
Article
An investigation was undertaken to study the behaviour of cement-stabilized aggregate mixtures modified with small amounts of rubber under compressive loading with the aim of providing more sustainable and less brittle mixtures for use in semi-rigid pavements. Three rubber replacement levels (15%, 30%, and 45% by same volume of one aggregate fracti...
Article
This manuscript is a part of a novel investigative approach focusing on the design of inverted pavements in the United Kingdom. This paper reports the permanent deformation response of simulative (laboratory-scale) inverted pavements with various thickness combinations through the use of two laboratory devices. A new analytical methodology is imple...
Article
The ability to create realistic digital aggregates is the first step to computationally optimise civil engineering materials such as concrete, asphalt, or ballast, which are based on aggregates. A method to generate aggregates with realistic shapes has been created in a physics engine. The approach uses morphological properties of the aggregates as...
Chapter
This chapter introduces expanded polystyrene (EPS) geofoam as a relatively new material for civil engineering applications. EPS geofoam is significantly lighter that common civil engineering materials (for example, 1%–2% of soil density) and it is available in a wide range of compressive strengths. Therefore it is a suitable material for a large va...
Article
This paper reports full scale experiments, under simulated heavy traffic, of geocell and EPS (expanded polystyrene) geofoam block inclusions to mitigate the pressure on, and deformation of, shallow buried, high density polyethylene (HDPE) flexible pipes while limiting surface settlement of the backfilled trench. Geocell of two pocket sizes and EPS...
Article
Full-text available
An inverted pavement (IP) is a type of the pavement in which an unbound granular material (UGM) layer is constructed between a stiffer cement-treated base (CTB) and a hot mix asphalt (HMA) surface. The presence of the CTB layer in the inverted pavement gives high overall pavement stiffness but also leads to the possibility of reflective cracking in...
Article
Warm-mix asphalt (WMA) is commonly mixed and compacted 15°C to 30°C below that of conventional hot mix asphalt (HMA). The lower production temperature of WMA is expected to give an advantage of a lower cooling time of newly laid asphalt overlay before it can be opened to traffic during the nighttime airfield pavement construction. The reduced cooli...
Article
Full-text available
Flexible pavements and climate are interactive. Pavements are climate sensitive infrastructure, where climate can impact their deterioration rate, subsequent maintenance, and life-cycle costs. Meanwhile, climate mitigation measures are urgently needed to reduce the environmental impacts of pavements and related transportation on the macroclimate an...
Article
Roller compacted concrete (RCC) is a form of plain concrete pavement (JPCP). RCC is a zero-slump concrete consisting of well-graded aggregate, cement and water. RCC has many advantages over other pavement types, particularly cost and speed of construction. Recently, RCC has undergone many developments mostly directed towards improving quality, incl...
Article
The suitability of geocell reinforcement in reducing rut depth, surface settlements and/or pavement cracks during service life of the pavements supported on expanded polystyrene (EPS) geofoam blocks is studied using a series of large-scale cyclic plate load tests plus a number of simplified numerical simulations. It was found that the improvement d...
Article
Climate factors have not become a typical metric to consider for pavement life cycle cost analysis (LCCA). Changes in climate may affect pavement rutting, roughness, and cracking and lead to consequent changes in maintenance decision-making and life cycle costs. This study develops a methodology to incorporate the effects of climate variability int...
Conference Paper
Reducing the cooling period of newly laid asphalt overlays could help airport authorities to quickly open remediated pavements to traffic. This paper reviews four strategies for a reduced cooling period, prior to trafficking, of newly-placed asphalt overlays: (1) defining and selecting the warmest permissible asphalt temperature at opening to traff...
Conference Paper
The increase in 24-hour airport operation and activity has limited the periods available for the execution of airport pavement rehabilitation. The early opening of asphalt overlays to traffic would reduce the overall rehabilitation period due to more volume done each night. On the other hand, the insurance of adequate cooling before opening to traf...
Article
An investigation has been undertaken to investigate the influence of rubber inclusion at different levels of stabilisation on the behaviour of cemented granular mixtures, under static and cyclic flexural testing, and to compare this with mixtures without rubber. Both are intended to be used as base courses of semi-rigid pavement structure. 3%, 5%,...
Article
Due to the importance of soil reinforcement using geotextiles in geotechnical engineering, study and investigation into long-term performance, design life and survivability of geotextiles, especially due to installation damage are necessary and will affect their economy. During installation, spreading and compaction of backfill materials, geotextil...
Conference Paper
Full-text available
Bhutan is a country with one of the lowest per capita incomes and very limited financial and industrial resources. Situated in the Himalayan foothills and mountains, its road transport network must negotiate very challenging terrain in terms of topography, rainfall and earthquake propensity with a widespread risk of flooding and landslides. For the...
Article
Plate anchors are commonly used to resist static, cyclic and monotonic after cyclic-loading uplift loads. Under cyclic loading, progressive sudden failure may occur, characterized by accumulated displacement – even under loads significantly less than the static capacity. Despite extensive usage of geocell for increasing the cyclic resilience, the i...
Article
The soil-geotextile filtration mechanism is a complex process which depends on physical compatibility between the geotextile and the soil to be retained. Several methods have been proposed by researchers for assessing the filtration behaviour of soil-geotextile composite systems under steady state conditions. The Gradient Ratio (GR) test is the mos...
Article
This paper has been prepared in the frame of a research focused on the development of Cold Mix pavement materials made with calcium-alginate Capsules (CMC) instead of with just bitumen emulsion, as it is normally made. The initial objective was to remove most of the water in cold mix asphalt by encapsulating bitumen droplets. The encapsulation meth...
Article
This study introduces a mechanism for initial assessment and future development to improve understanding of expanded polystyrene (EPS) behavior as a super-lightweight material for road construction. Large scale cyclic plate load tests on model pavements were performed. The effect of several factors including thickness of soil, thickness of subseque...
Article
Cement-stabilized aggregate mixtures (CSAMs) have been used effectively within semi-rigid pavement structures. However, the sensitivity to cracking under tensile loading is the main problem that may cause a deterioration due to reflection to the overlaying layers. The primary objective of this research is to show the extent to which the steel fiber...
Article
Plate anchors are frequently used to provide resistance against uplift forces. This paper describes the reinforcing effects of a geocell-reinforced soil layer on uplift behavior of anchor plates. The uplift tests were conducted in a test pit at near full-scale on anchor plates with widths between 150 and 300 mm with embedment depths of 1.5–3 times...
Article
Full-text available
Abstract In order to reduce accident risk, highway authorities prioritise maintenance budgets partly based upon previous accident history. However, as accident rates have continued to fall, this approach has become problematic as accident ‘black spots’ have been treated and the number of accidents at any individual site has fallen, making previous...
Article
Cement-stabilized aggregate mixtures (CSAMs) have been used effectively within semi-rigid pavement structures. However, the sensitivity to cracking under tensile loading is the main problem that may cause a deterioration due to reflection to the overlaying layers. The primary objective of this research is to show the extent to which the steel fiber...
Article
Full-text available
In order to reduce accident risk, highway authorities prioritise maintenance budgets partly based upon previous accident history. However, as accident rates have continued to fall, this approach has become problematic as accident ‘black spots’ have been treated and the number of accidents at any individual site has fallen, making previous accident...
Conference Paper
Full-text available
The main aim of this study is to explore if it is possible to improve identification of locations where the risk of accidents is high, using harsh braking incident (HBI) data obtained from routinely collected truck performance data. For this purpose, HBIs were used, along with traffic and geometric variables, as an independent variable for predicti...
Poster
Full-text available
THE RELATIONSHIP BETWEEN TRUCK HARSH BRAKING INCIDENTS AND TRUCK ACCIDENTS AT ROUNDABOUT APPROACHES
Conference Paper
Full-text available
Roller compacted concrete (RCC) is a mass concrete with zero slump consisting of well-graded aggregate, cement and water. RCC has many advantages over other pavement types, particularly cost and speed of construction. Recently, RCC has undergone many developments mostly directed towards improving quality, including smoothness and durability. RCC no...
Article
Interfacial bonding between constituent materials and pore sizes in a concrete matrix are major contributors to enhancing the strength of concrete. In a bid to examine how this phenomenon affects a laterized concrete, this study explored the relationship between the morphological changes, porosity, phase change, compressive, and split tensile stren...
Article
Using industrial wastes and local materials as artificial aggregates in cement based materials remains a relevant measure for conservation of natural sources. In this study, novel cementitious mixes containing pulverized ceramic blended cement, ceramic aggregate and laterite were systematically combined to produce cement mortars. The mortar specime...
Article
In this article, a novel method to mitigate pavement temperatures by the means of air convection is presented. The technique introduced here is based on a new type of experimental setup called a ground source heat simulator, which is able to feed air at a controlled temperature to a set of pipes embedded under a test pavement surface. The air at th...
Article
Full-text available
This paper presents a set of results of plate load tests that imposed incremental cyclic loading to a sandy soil bed containing multiple layers of granulated rubber-soil mixture (RSM) at large model scale. Loading and unloading cycles were applied with amplitudes incrementally increasing from 140 to 700 kPa in five steps. A thickness of the RSM lay...
Article
A brief review is given of ground freezing technology as a means of providing groundwater cut-off and temporary structural support in weak ground for transportation tunnelling and shaft-sinking operations. Then detailed coverage of a particular case history is reported in variable soils in Queens, New York. As part of the upgrading of rail access f...
Conference Paper
Full-text available
Roller compacted concrete (RCC) is a mass concrete with zero slump consisting of well-graded aggregate, cementitious materials and water. RCC has many advantages over other pavement types, particularly cost and speed of construction. However, it also presents difficulties with high-speed applications related to surface texture and surface evenness....
Article
In this article, the performance of a convection-powered air flow through an asphalt prototype pavement is investigated in a field test. An asphalt prototype pavement with pipes buried in its aggregate layer was connected to a constant temperature heat source and installed at the University of Nottingham, UK. In the experimental configuration chose...
Conference Paper
Full-text available
The principal aim of this study is to develop a suitable model for predicting truck accidents at roundabouts and to identify the significance of the exposure variables (traffic and geometric characteristics) on truck accidents. To accomplish this, 70 roundabouts (with 284 approaches) were selected in the UK. The data used for model prediction inclu...
Conference Paper
Full-text available
The principal aim of this paper is to explore if analysis of truck harsh braking incidents (HBIs) can help to predict accident risk for road safety studies. The findings may be useful for the identification of locations with high accident risk without waiting for an accident history to develop. To achieve the aims, position data (i.e, latitude, lon...
Article
Full-text available
This paper describes the beneficial effects of multiple layers of rubber–sand mixture (RSM). The plate load tests, using circular plate of 300 mm diameter, were performed at an outdoor test pit, dug in natural ground with dimensions of 2000 × 2000 mm in plan and 720 mm in depth to facilitate realistic test conditions. The rubber used in the RSM lay...
Article
In this paper, an analysis of a convection-powered asphalt solar collector prototype is approached by the means of experimental trials and computational fluid dynamics (CFD) simulations in order to evaluate how to optimise its design for the reduction of high urban pavement temperatures. Since the energy harvesting setup consists of a series of pip...
Article
Full-text available
Abstract Roundabouts have been widely used in the UK on all road classes, as they are generally considered safer than other types of intersections. The objective of this study is to examine geometric and traffic characteristics and their influence on accident numbers. The study comprises 70 roundabouts (284 approaches). The data used included all...
Code
This MATLAB algorithm (see https://dx.doi.org/10.6084/m9.figshare.3839526) allows you to pack n circles in a rectangular domain (see sample images at the DOI). The void ratio (i.e., amount of empty space in the rectangle) is user-defined and met precisely. The domain has an arbitrary size that you can choose. Other parameters are also available for...
Code
This MATLAB algorithm (see https://dx.doi.org/10.6084/m9.figshare.3839532) allows you to pack n circles in a circular domain (see sample images at the DOI). The void ratio (i.e., amount of empty space in the circular domain) is user-defined and met precisely. The domain has an arbitrary diameter that you can choose. Other parameters are also availa...
Data
This dataset (https://dx.doi.org/10.6084/m9.figshare.3837966) includes the X-ray CT scans of a 50 mm thick asphalt core with a diameter of 100 mm. In this dataset, only a portion of the overall thickness of the sample is available. The images have a very high size and are in .tif format. Images are numbered in sequential order. The resolution of...
Data
This dataset (https://dx.doi.org/10.6084/m9.figshare.3837972) includes the X-ray CT scans of a 50 mm thick asphalt core with a diameter of 100 mm. The images have a very high size and are in .tif format. Images are numbered in sequential order. The resolution of the scans is 65.2 um (micrometers). The slices are generated at 0.4 mm (400 um) from...
Data
This dataset (https://dx.doi.org/10.6084/m9.figshare.3837990) includes the X-ray CT scans of a 50 mm thick asphalt core with a diameter of 100 mm. The images have a very high size and are in .tif format. Images are numbered in sequential order. The resolution of the scans is 65.2 um (micrometers). The slices are generated at 0.4 mm (400 um) from...
Data
This dataset (https://dx.doi.org/10.6084/m9.figshare.3837984) includes the X-ray CT scans of a 50 mm thick asphalt core with a diameter of 100 mm. The images have a very high size and are in .tif format. Images are numbered in sequential order. The resolution of the scans is 65.2 um (micrometers). The slices are generated at 0.4 mm (400 um) from...
Data
This dataset (https://dx.doi.org/10.6084/m9.figshare.3837993) includes the X-ray CT scans of a 50 mm thick asphalt core with a diameter of 100 mm. The images have a very high size and are in .tif format. Images are numbered in sequential order. The resolution of the scans is 65.2 um (micrometers). The slices are generated at 0.4 mm (400 um) from...
Data
This dataset (https://dx.doi.org/10.6084/m9.figshare.3837987) includes the X-ray CT scans of a 50 mm thick asphalt core with a diameter of 100 mm. The images have a very high size and are in .tif format. Images are numbered in sequential order. The resolution of the scans is 65.2 um (micrometers). The slices are generated at 0.4 mm (400 um) from...
Article
Full-text available
It has been reported that owing to a densification of the internal structure of concrete, adding mineral admixtures leads to a more brittle behaviour. Therefore, with the intention of modifying (increasing the strength of) foamed concrete to make it suitable for structural purposes by means of admixtures and lightweight aggregate addition, the effe...
Conference Paper
Full-text available
In this paper, a proof of concept of a method is presented for the study of granular materials, such as asphalt, based on the use of a physics engine. To begin with, virtual aggregates are generated with randomized 3D shapes and a size distribution based on a chosen gradation curve. Then, the aggregates are placed in a constrained volume and subjec...
Article
This paper describes a series of reduced scale tests, at unit gravity, performed on circular footings supported by reinforced sand. Reinforcement by multiple layers of geocell was investigated and performance of the footing was compared to one on the same sandy soil containing multi-layered planar geotextile reinforcement. The comparison used geoce...
Article
Full-text available
Different maintenance interventions have different ability to address distresses on flexible pavements. Understanding the maintenance effects can benefit pavement maintenance decision-making. In this study, the immediate maintenance effects on roughness and rutting of three interventions including overlay, overlay with an additional base layer and...
Article
The main focus of this paper is to investigate the tensile properties of virgin and rubberized cement bound granular mixtures. This was conducted using indirect tensile testing with lateral displacement measurements, nondestructive resonant frequency testing, X-ray CT and quantitative assessment for cracking pattern using fractal analysis. The inve...