Brendan Scott | University of Adelaide (original) (raw)

Conference Presentations by Brendan Scott

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Proceedings of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, 2017

Rolling dynamic compaction (RDC) is the generic term used for soil densification involving traver... more Rolling dynamic compaction (RDC) is the generic term used for soil densification involving traversing the ground with a 3-, 4-or 5-sided module. Originally developed in South Africa in the late 1940s, RDC is particularly attractive as it is able to compact the ground more effectively, i.e. to greater depths than its static and vibrating roller counterparts, and more efficiently because of its greater speed-12 km/h compared with 4 km/h using conventional circular drum rollers. Due to the combination of kinetic and potential energies, and the large mass of the module, RDC has demonstrated compacting effort to more than 3 m in some soils, which is far deeper than conventional static or vibratory rolling, which is generally limited to depths of less than 0.5 m. In order to understand better the efficacy of RDC in a range of soil types and ground and field conditions, a sophisticated 1:13 scale testing facility has been established. The paper presents an overview of RDC, its applications in civil and mining engineering, the testing facility and experimental program, and the research outcomes to date.

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Proceedings of the 2020 Coal Operators Conference, 2020

The construction and management of haul roads remains a critical element in the efficient operati... more The construction and management of haul roads remains a critical element in the efficient operation of all mines. Significant effort has been applied to design practices, extending the use of design charts and computer programs. Attention has been paid to the pavement materials and material properties, based on decades of geotechnical data and experience. Opportunities still exist for improvements to be realised in compaction protocols, particularly in the use of rolling dynamic compaction (RDC). RDC involves the delivery of a dynamic compactive effort using non-circular towed compactors, which are designed to deliver a combination of potential energy of a falling weight and kinetic energy mobilised due to the relatively high towing speed. The objectives include the proof-rolling and preparation of subgrade areas, exposing soft spots and weak zones and often establishing a sufficiently competent raft layer, as well as deep lift compaction offering cost-efficient construction of ramps and haul road pavements with programming benefits. The ability to compact deeper lifts allows fill particles to be larger without inhibiting the compaction process, which increases the sustainability of the process through reducing the constraints on the fill materials by allowing a larger maximum particle size. Case studies are cited where RDC has been trialled on several mine sites and many mines have benefited from the use of the technology. The continued attention to improving haul road construction will result in less road maintenance, less vehicle damage and improved truck tyre life, and RDC offers a method of contributing to these improvements. The compaction energy of RDC offers more leniency in moisture conditioning where adequate compaction densities can be achieved with much lower water addition than conventional laboratory optimum moisture content. When applied to coarse surface layer materials RDC will generate sufficient fines to provide a high-friction tyre-friendly low-maintenance finish on haul road surfaces.

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Proceedings of the 4th World Congress on Civil, Structural, and Environmental Engineering (CSEE’19), 2019

Rolling dynamic compaction (RDC) is a ground improvement method that involves towing, typically w... more Rolling dynamic compaction (RDC) is a ground improvement method that involves towing, typically with the aid of a tractor, a 3-, 4-or 5-sided, non-circular module. Due to the mechanics of its operation, as well as the increased travel speed of 10–12km/h when compared with the 4 km/h speed of conventional vibrating and drum rollers, RDC has demonstrated improved earthworks efficiency and greater effectiveness at depth below the ground surface. Despite the significant benefits derived from RDC, much research is needed to facilitate the development of models to predict the extent of ground improvement, as a function of soil type, ground conditions, travel speed, module type and weight, and the number of passes. This paper presents the results of an extensive research program undertaken to quantify the behaviour of RDC and its consequent effect of the ground. The research involves field studies incorporating in situ measurement, laboratory testing of small-scale physical models involving novel instrumentation, numerical modelling using dynamic finite element analyses, and the implementation of artificial intelligence. Each of these aspects is treated in detail in the paper.

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Proceedings 13th Australia New Zealand Conference on Geomechanics, 2019

This paper reviews compaction by dynamic means and discusses factors that influence the effective... more This paper reviews compaction by dynamic means and discusses factors that influence the effectiveness of the following techniques: Dynamic Compaction, Rapid Impact Compaction and Impact Rolling, all of which have their particular application in ground engineering. Case study examples covering a wide range of projects and soil conditions, are included. The improvement depths for each of these dynamic ground improvement techniques are explored, with the results from the case studies compared with published information to help the reader make informed choices given similar soil conditions. Case studies that report the measured magnitude of ground vibrations are also presented to assist with the assessment of the potential source of nuisance to people or damage to surrounding structures.

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Proceedings 7th International Conference on Unsaturated Soils, 2018

Unsaturated clays found in the Plains of Adelaide, South Australia, are typically stiff-to-hard a... more Unsaturated clays found in the Plains of Adelaide, South Australia, are typically stiff-to-hard and can exhibit high shear strength due to very high suction. Such suction hardening behavior allows deep vertical cuttings to stand unsupported for significant periods of time. It is evident, from previous studies, that unsaturated soil mechanics is particularly relevant to the design of earth structures in South Australia because of its semi-arid climate. The South Australian Government is currently constructing a 4 km section of non-stop roadway, featuring 3 km of a depressed motorway to a maximum depth of 8 m below street level. In the early design and planning stages of the project, various retaining wall options were considered. Cantilever soldier piles were constructed adopting varying diameters and center-to-center spacings, as part of a full-scale field trial that was undertaken during the design phase. This study examines the use of numerical methods for stability analysis of deep cuttings, using the finite element method to model the performance of the piled retaining walls with different design configurations.

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Proceedings 7th International Conference on Unsaturated Soils, 2018

To better understand the behaviour of unsaturated clays for retaining wall design in Adelaide, So... more To better understand the behaviour of unsaturated clays for retaining wall design in Adelaide, South Australia, a trial soldier pile retaining wall supporting an 8 m deep excavation was constructed for a proposed 3 km long underpass. The full scale trial retaining wall was constructed prior to the start of summer to allow the soil to shrink over an extended dry period, typical of an Adelaide summer. At the end of summer, the soil was wetted up via a controlled inundation program that replicated a pipe burst or leaking water main, critical considerations for retaining wall design. As part of an extensive testing and monitoring program, in situ moisture probes were used to quantify the change in soil moisture content before, during and after inundation. This paper presents a practical means to estimate soil suction based on the calibration of moisture probe data and the use of a site specific soil-water characteristic curve. Limitations of using moisture probes to infer suction are discussed, with suggestions provided for the future use of similar moisture probes in very stiff to hard clay soils as encountered on this site.

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5th International Conference on Geotechnical and Geophysical Site Characterisation, 2016

Rolling Dynamic Compaction (RDC) involves a heavy non-circular module that rotates and falls to i... more Rolling Dynamic Compaction (RDC) involves a heavy non-circular module that rotates and falls to impact the ground dynamically; it has a greater depth of influence compared to conventional circular rollers. The depth of influence to which an impact roller can compact soil is known to vary, and is dependent upon factors such as soil type, moisture content and applied input energy, thus verification of impact rolling is particularly important to quantify the extent to which soil has been improved. This paper compares before and after compaction test results using three in situ testing methods, field nuclear density, dynamic cone penetrometer (DCP) and spectral analysis of surface waves (SASW), as well as the ground response due to RDC using earth pressure cells, accelerometers and surface settlement measurements used during the compaction trial.

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3rd International Symposium on Cone Penetration Testing (CPT'14), 2014

Rolling Dynamic Compaction (RDC) is a ground improvement technique that involves compacting soil ... more Rolling Dynamic Compaction (RDC) is a ground improvement technique that involves compacting soil using a non-circular roller. Whilst conventional circular rollers are able to compact layer thicknesses typically in the range of 200 mm to 500 mm, thicker layers are able to be compacted using RDC. However, the depth of influence of RDC can vary significantly depending on the soil type, moisture content, loose layer thickness and number of passes. This paper focuses on how cone penetration testing was used during a compaction trial as a key site investigation technique to determine the zone of influence of RDC at a site involving quartzose and carbonate sand fill. The results presented quantify the increase in cone tip resistance with depth and illustrates how a number cone penetration tests (CPTs) were used to evaluate changes in soil strength due to increased roller passes, changes in moisture content or placed loose layer thickness.

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Proceedings International Conference on Ground Improvement and Ground Control, 2012

Rolling Dynamic Compaction (RDC) is a generic term associated with densifying ground using non-ci... more Rolling Dynamic Compaction (RDC) is a generic term associated with densifying ground using non-circular (impact) rollers. RDC is suited to deep fill applications because of the ability to compact ground efficiently by means of its faster operating speed (10-12 km/h) and greater depth of influence when compared to conventional circular rollers. Whilst conventional circular rollers are able to compact layer thicknesses typically in the range of 200-500 mm, thicker layers are able to be compacted using RDC. This paper discusses performance based specifications and the applicability of both the Standard and Modified Proctor compaction tests to RDC. For projects where impact rollers are used, the Modified Proctor test is strongly recommended as the energy imparted onto the soil is more representative than the Standard test.

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Proceedings of the 11th Australia - New Zealand Conference on Geomechanics, 2012

Rolling Dynamic Compaction (RDC) is a generic term associated with densifying the ground using a ... more Rolling Dynamic Compaction (RDC) is a generic term associated with densifying the ground using a non-circular roller. The application and use of RDC in the mining industry is increasing because of its ability to compact ground efficiently by means of a faster operating speed (10-12 km/h) and compaction of thicker layers than conventional circular rollers. Whilst conventional rollers are able to compact fill in layers up to 400 mm, thicker layers are able to be adopted using RDC for the construction of tailings dams and mining haul roads. Increased layer thicknesses enable larger particle sizes to be used, therefore greater reuse of mine spoil material can be undertaken with a reduced need to screen out large quantities of oversized materials. As well as demonstrating how RDC has been used effectively for the compaction of bulk earthworks at two different mine sites, this paper also discusses various aspects and factors associated with conducting a compaction trial on mine spoil materials.

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Proceedings XVII International Conference on Soil Mechanics and Geotechnical Engineering, 2009

As a major component of research activities at Sydney and Adelaide Universities into various aspe... more As a major component of research activities at Sydney and Adelaide Universities into various aspects of rolling dynamic compaction as performed with the " square " impact roller, an experimental test site has been established. The test site is approximately 100m by 50m, and is part of a larger industrial property in Wingfield, South Australia. Geologically, the site comprises approximately 1-2m of non-engineered fill, overlying Estuarine deposits. The primary objectives of the work at the test site relate to quantifying the effects of the impact roller in terms of energy delivered to the ground and the ground response. Impact rollers with solid 4-sided modules of mass 8t and 12t are utilised. A monitoring and testing regime has been developed that includes physical measurements of energy on and below the impact module, surface settlement and sub-surface layer compression measurements. Early results from the testing programme provide a basis for understanding and developing the relationship of delivered to transmitted energy for the particular impact modules used at this site, the dissipation of energy through the ground and the effects on the various strata at depth due to module mass and number of passes (or energy input). The output from this study will form the basis for modelling ground conditions at this site and the effects of the impact rolling. The data thus generated will support further studies into numerical modelling of rolling dynamic compaction and the ongoing programme of testing at other sites with different geological characteristics.

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Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering, 2013

Rolling Dynamic Compaction (RDC) is a soil improvement technique, which involves a heavy (6– to 1... more Rolling Dynamic Compaction (RDC) is a soil improvement technique, which involves a heavy (6– to 12–tonne) non-circular module (impact roller) that rotates about a corner as it is towed, causing the module to fall to the ground and compact it dynamically. This paper focuses on the 4-sided module and aims to quantify the effectiveness of RDC by means of a combination of field studies and numerical modeling. The field studies involved embedding earth pressure cells beneath the ground at varying depths and measuring the in situ stress over a range of module passes. In addition, a variety of in situ tests were performed including penetrometer, field density and geophysical testing to measure density improvement, again as a function of the number of module passes. The field measurements indicated that the depth of improvement exceeded 2 meters below the ground surface. Numerical modeling was undertaken using the dynamic finite element analysis software, LS-DYNA; the results align well with those obtained from the field studies. Parametric studies were also undertaken to determine the influence of varying soil parameters on the effectiveness of RDC.

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ISSMGE - TC 211 International Symposium on Ground Improvement IS-GI , 2012

Rolling dynamic compaction (RDC) involves traversing the ground by means of a non-circular module... more Rolling dynamic compaction (RDC) involves traversing the ground by means of a non-circular module consisting of 3, 4 or 5 sides. Over the last few decades, a number of studies have been carried out in an effort to quantify the effectiveness of RDC. In this study, the zone of influence of the 4-sided 'impact roller' was measured in a systematic fashion in the field by means of a series of earth pressure cells (EPCs) embedded in the ground, in situ density measurements and dynamic cone penetration tests. Measurements obtained from the field trial, which was conducted at an open-cut mine in South Australia, suggest that the depth of influence for which there is significant and quantifiable improvement with the roller is approximately 2.1 m below the ground surface and this corresponded to soil stress readings of between 150 and 200 kPa. Positive pressure readings due to RDC were also measured by the EPCs buried up to 3.85 m below the ground surface, indicating that the actual zone of influence (for which there is improvement) extends beyond this depth.

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Proceedings 7th Australia - New Zealand Young Geotechnical Professionals Conference, 2006

The remediation works recently carried out to stabilize a section of the cliff face at Witton Blu... more The remediation works recently carried out to stabilize a section of the cliff face at Witton Bluff, South Australia are described. These remediation works were required because continuing terrestrial erosion has lead to large sections of the Witton Bluff cliff face becoming unstable. The remediation methods included the use of a geogrid reinforced earth retaining wall, used for the first time in South Australia in a coastal environment. The importance of community involvement, including working closely with the local Aboriginal people, is emphasised. Experiences gained from the project provided several lessons for future projects of a similar nature.

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Proceedings 8th Australia - New Zealand Young Geotechnical Professionals Conference, 2008

Rolling dynamic compaction (RDC) is a commonly used ground improvement technique. A key feature o... more Rolling dynamic compaction (RDC) is a commonly used ground improvement technique. A key feature of RDC is the ability to provide deep layer compaction when compared to conventional rollers. This greater zone of influence makes it a productive and cost-effective option in earthworks applications. Whilst RDC has been used successfully on many projects in Australia and overseas in applications such as roads, airports, construction and land reclamation projects, there are cases where the expected ground improvement has not occurred. There is a lack of information indicating what the zone of influence of the roller is, and how much input energy is required for different soil conditions. The methods of testing the effectiveness of RDC need improvement. Relationships are needed that relate the input energy and the ground improvement that can be expected for different soil types.

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Earthworks Seminar Proceedings, Australian Geomechanics Society, SA/NT Chapter, 2004

This paper outlines the nature of the soil conditions at the site, the method of ground treatment used to preconsolidate the soft soils, and the results of settlement readings extending over time periods up to 9 months. The results of predictions of the settlement over a 15-year time period are outlined. Pavement configurations for the heavy container and truck areas are described.

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Proceedings - 10th Austraila - New Zealand Conference on Geomechanics, 2007

Ground improvement using impact rolling was adopted. After initial impact rolling, seismic methods were used to obtain an indication of the nature of the subsoil by non intrusive methods. Traditional intrusive methods alone and reliance on a method specification were considered too risky given the nature of the fill material.

A Multi-channel Analysis of Surface Waves (MASW) seismic survey was adopted, enabling near surface anomalies to be identified and correlations of seismic velocity with Young’s Modulus to be determined. The seismic survey results generally gave good correlation with traditional geotechnical investigation methods that were also undertaken, and enabled deficient areas to be identified and reworked or excavated and replaced.

The ground improvement proved successful in achieving the required 100 kPa bearing capacity.

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Proceedings - 20th International Geophysical Conference and Exhibition, 2009

The output from an MASW survey and analysis is essentially a series of 1-dimensional S-wave velocity profiles, generating spatially discrete data points similar to borehole data. As the data are collected along a line and sampled at closely spaced intervals, it is common to present the data in the form of a 2-dimensional section of S-wave velocities along the survey line, rather than a 1-dimensional profile with depth. If an MASW survey consists of closely spaced survey lines, it is possible to present the output of the surveyed area as a 3-dimensional data set.

This paper presents an example of an application of the MASW survey method at a landfill site, with data presented in plan view with a number of depth slices.

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Papers by Brendan Scott

The remediation works recently carried out to stabi lize a section of the cliff face at Witton Bl... more The remediation works recently carried out to stabi lize a section of the cliff face at Witton Bluff, S outh Australia are described. These remediation works were required b ecause continuing terrestrial erosion has lead to l arge sections of the Witton Bluff cliff face becoming unstable. The remediation methods included the use of a geogrid reinforced earth retaining wall, used for the first time in South Au stralia in a coastal environment. The importance o f community involvement, including working closely with the loc al Aboriginal people, is emphasised. Experiences g ained from the project provided several lessons for future project s of a similar nature.

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Proceedings of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, 2017

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Proceedings of the 2020 Coal Operators Conference, 2020

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Proceedings of the 4th World Congress on Civil, Structural, and Environmental Engineering (CSEE’19), 2019

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Proceedings 13th Australia New Zealand Conference on Geomechanics, 2019

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Proceedings 7th International Conference on Unsaturated Soils, 2018

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Proceedings 7th International Conference on Unsaturated Soils, 2018

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5th International Conference on Geotechnical and Geophysical Site Characterisation, 2016

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3rd International Symposium on Cone Penetration Testing (CPT'14), 2014

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Proceedings International Conference on Ground Improvement and Ground Control, 2012

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Proceedings of the 11th Australia - New Zealand Conference on Geomechanics, 2012

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Proceedings XVII International Conference on Soil Mechanics and Geotechnical Engineering, 2009

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Proceedings of the 18th International Conference on Soil Mechanics and Geotechnical Engineering, 2013

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ISSMGE - TC 211 International Symposium on Ground Improvement IS-GI , 2012

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Proceedings 7th Australia - New Zealand Young Geotechnical Professionals Conference, 2006

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Proceedings 8th Australia - New Zealand Young Geotechnical Professionals Conference, 2008

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Earthworks Seminar Proceedings, Australian Geomechanics Society, SA/NT Chapter, 2004

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Proceedings - 10th Austraila - New Zealand Conference on Geomechanics, 2007

The ground improvement proved successful in achieving the required 100 kPa bearing capacity.

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Proceedings - 20th International Geophysical Conference and Exhibition, 2009

This paper presents an example of an application of the MASW survey method at a landfill site, with data presented in plan view with a number of depth slices.

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$Research paper thumbnail of Inferring soil water characteristics for Adelaide clay using fractal theory$

A full scale trial pile wall was constructed as part of an initial investigation for a road under... more A full scale trial pile wall was constructed as part of an initial investigation for a road underpass project in Adelaide, South Australia. The purpose of the trial was to determine if a soldier piled retaining wall could support a deep vertical excavation upon wetting up of the unsaturated clay behind the wall. Soils encountered in this case study were clays of low-to-medium plasticity, and were shown to be fractal via the use of sieve and hydrometer testing, whereby a linear relationship between particle size and percentage passing was obtained when plotted on a logarithmic scale. The confirmation of this Adelaide clay soil being fractal, and that fractal dimensions of particle size and pore size distributions are not equal, are findings that are of significance in gaining a greater understanding of unsaturated soil behaviour. Soil water characteristics inferred from fractal theory are described within this paper, in addition to the results obtained from laboratory testing for suction and moisture content of soil sampled during the trial investigation.

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$Research paper thumbnail of Inferring soil water characteristics for Adelaide clay using fractal theory$

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Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, ... more Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2020

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The majority of the more recently constructed build ings in the Adelaide CBD are founded within t... more The majority of the more recently constructed build ings in the Adelaide CBD are founded within the ver y stiff to hard Keswick and Hindmarsh Clay, because these strata are relatively homogeneous. This Paper describes the work recently undertaken for a 21-storey office building founded on the underlying more variable Hallett Cove Sandst one formation. Founding piles within the Hallett Cove Sandstone meant fewer piles carrying higher loads could be used than for piles founded in the overlying clay. However the variable nature of the Hallett Cove Sandstone presented sev eral challenges that needed to be overcome.

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The geotechnical conditions at Coghlan Road, Outer Harbor, SA comprise dredged fill over estuarin... more The geotechnical conditions at Coghlan Road, Outer Harbor, SA comprise dredged fill over estuarine clays, sands and peat of the St Kilda Formation. All these soil layers are soft, saturated, and have the property of undergoing large settlements under load. The development of the site into a large export facility involving heavy container handling and storage for the Hardy Wine Company therefore required special earthworks procedures. This paper outlines the nature of the soil conditions at the site, the method of ground treatment used to preconsolidate the soft soils, and the results of settlement readings extending over time periods up to 9 months. The results of predictions of the settlement over a 15-year time period are outlined. Pavement configurations for the heavy container and truck areas are described.

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Rolling dynamic compaction (RDC) is the generic term used for soil densification involving traver... more Rolling dynamic compaction (RDC) is the generic term used for soil densification involving traversing the ground with a 3-, 4or 5-sided module. Originally developed in South Africa in the late 1940s, RDC is particularly attractive as it is able to compact the ground more effectively, i.e. to greater depths than its static and vibrating roller counterparts, and more efficiently because of its greater speed – 12 km/h compared with 4 km/h using conventional circular drum rollers. Due to the combination of kinetic and potential energies, and the large mass of the module, RDC has demonstrated compacting effort to more than 3 m in some soils, which is far deeper than conventional static or vibratory rolling, which is generally limited to depths of less than 0.5 m. In order to understand better the efficacy of RDC in a range of soil types and ground and field conditions, a sophisticated 1:13 scale testing facility has been established. The paper presents an overview of RDC, its application...

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Journal of Rock Mechanics and Geotechnical Engineering, 2019

Abstract The influence of towing speed on the effectiveness of the 4-sided impact roller using ea... more Abstract The influence of towing speed on the effectiveness of the 4-sided impact roller using earth pressure cells (EPCs) is investigated. Two field trials were undertaken; the first trial used three EPCs placed at varying depths between 0.5 m and 1.5 m with towing speeds of 9–12 km/h. The second used three EPCs placed at a uniform depth of 0.8 m, with towing speeds of 5–15 km/h. The findings from the two trials confirmed that towing speed influences the pressure imparted to the ground and hence compactive effort. This paper proposes that the energy imparted to the ground is best described in terms of work done, which is the sum of the change in both potential and kinetic energies. Current practice of using either kinetic energy or gravitational potential energy should be avoided as neither can accurately quantify rolling dynamic compaction (RDC) when towing speed is varied.

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Géotechnique Letters, 2019

Rolling dynamic compaction (RDC) is typically used for improving ground in situ or compacting fil... more Rolling dynamic compaction (RDC) is typically used for improving ground in situ or compacting fill in thick lifts. In many project applications, the effects of RDC are verified by way of testing that is undertaken pre- and/or post-compaction. This study presents results from a full-scale field trial that involved placing an earth pressure cell (EPC) and accelerometers at a depth of 0·7 m within a 1·5 m thick layer of homogeneous sandy gravel to measure the response to RDC in real-time. Double integration of acceleration–time data enabled settlement to be inferred, while the EPC measured the change in stress due to impact. The maximum change in vertical stress recorded over the 80 passes undertaken was approximately 1100 kPa. During a typical module impact, the loading and unloading response occurred over a duration of approximately 0·05 s. The acceleration response of RDC was measured in three orthogonal directions, with the vertical accelerations dominant.

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Proceedings of the 9th SEGJ International Symposium, 2009

The Multichannel Analysis of Surface Waves, or MASW in short (Park, et al, 1999; Suto, 2007) anal... more The Multichannel Analysis of Surface Waves, or MASW in short (Park, et al, 1999; Suto, 2007) analyses seismic data in the frequency-velocity domain and estimates the S-wave velocity structure under the seismic receiver array. Its application range varies, commonly from only a few metres to tens of metres, depending on the wavelengths of the surface waves used for analysis. The output from an MASW survey and analysis is essentially a series of 1-dimensional S-wave velocity profiles, generating spatially discrete data points similar to borehole data. As the data are collected along a line and sampled at closely spaced intervals, it is common to present the data in the form of a 2-dimensional section of S-wave velocities along the survey line, rather than a 1-dimensional profile with depth. If an MASW survey consists of closely spaced survey lines, it is possible to present the output of the surveyed area as a 3-dimensional data set. This paper presents an example of an application of the MASW survey method at a landfill site, with data presented in plan view with a number of depth slices.

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Ground Improvement Case Histories, 2015

Rolling dynamic compaction (RDC) is a soil improvement technique that involves a heavy noncircula... more Rolling dynamic compaction (RDC) is a soil improvement technique that involves a heavy noncircular module (impact roller) that rotates about a corner as it is towed, causing the module to fall to the ground and compact it dynamically. While conventional circular rollers are able to compact layer thicknesses typically up to 500 mm, thicker layers are able to be compacted using RDC due to the dynamic effect of the module, which yields a greater depth of influence. When combined with the ability to compact ground efficiently, by means of its faster operating speed (9–12 km/h) when compared to conventional circular rollers, RDC can be a productive and cost-effective option in many different earthwork applications. However, the depth of influence of RDC can vary significantly depending on the soil type, moisture content, loose layer thickness, or number of passes adopted.

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Proceedings of the International Conference on Ground Improvement & Ground Control, 2012

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10th ANZ Conference on Geomechanics, Brisbane, 2007

A proposed 1.5 ha industrial estate overlayed 1.5 - 2.0 metres of uncontrolled fill. The site had... more A proposed 1.5 ha industrial estate overlayed 1.5 - 2.0 metres of uncontrolled fill. The site had been left undeveloped for many years due to the problematic ground conditions. The challenge was to engineer the site such that an allowable bearing capacity of 100 kPa was achieved, in order to render the site suitable for development. Ground improvement using impact rolling was adopted. After initial impact rolling, seismic methods were used to obtain an indication of the nature of the subsoil by non intrusive methods. Traditional intrusive methods alone and reliance on a method specification were considered too risky given the nature of the fill material. A Multi-channel Analysis of Surface Waves (MASW) seismic survey was adopted, enabling near surface anomalies to be identified and correlations of seismic velocity with Young’s Modulus to be determined. The seismic survey results generally gave good correlation with traditional geotechnical investigation methods that were also undertaken, and enabled deficient areas to be identified and reworked or excavated and replaced. The ground improvement proved successful in achieving the required 100 kPa bearing capacity.

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World Congress on Civil, Structural, and Environmental Engineering, 2019

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Proceedings of the Institution of Civil Engineers - Ground Improvement

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Proceedings of the Institution of Civil Engineers - Ground Improvement

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Ground Improvement Case Histories: Compaction, Grouting and Geosynthetics, 2015

Rolling Dynamic Compaction (RDC) is a soil improvement technique, which involves a heavy non circ... more Rolling Dynamic Compaction (RDC) is a soil improvement technique, which involves a heavy non circular module (impact roller) that rotates about a corner as it is towed, causing the module to fall to the ground and compact it dynamically. Whilst conventional circular rollers are able to compact layer thicknesses typically up to 500 mm, thicker layers are able to be compacted using RDC due to the dynamic effect of the module, which yields a greater depth of influence. When combined with the ability to compact ground efficiently, by means of its faster operating speed (9-12 km/h) when compared to conventional circular rollers, RDC can be a productive and cost-effective option in many different earthwork applications. However, the depth of influence of RDC can vary significantly depending on the soil type, moisture content, loose layer thickness or number of passes adopted.

Applications of RDC as well as verification techniques that can be used to quantify ground improvement are presented. A featured case study investigates the zone of influence of a 4 sided ‘impact roller’ that was measured in a systematic fashion in the field by means of a number of earth pressure cells that were buried at varying depths beneath the ground surface and measuring the in situ stress over a range of module passes. In addition, a variety of in situ tests were performed including penetrometer, field density and geophysical testing to measure density improvement, again as a function of the number of module passes. The field measurements conducted on mine tailings indicated that the depth of improvement due to RDC exceeded 2 m below the ground surface. At a depth of 1.5 m, RDC imparted soil stresses of approximately 150 kPa into the ground; positive pressure readings were also measured by earth pressure cells buried up to 3.85 m below the ground surface, indicating that the actual zone of influence (for which there is improvement) extends beyond this depth.

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PhD Thesis, 2020

Rolling dynamic compaction (RDC) consists of a non-circular module of 3, 4 or 5 sides, that rotat... more Rolling dynamic compaction (RDC) consists of a non-circular module of 3, 4 or 5 sides, that rotates as it is towed, causing it to fall to the ground and compact it dynamically. There is currently little guidance available for geotechnical practitioners regarding the depths of improvement that are possible in varying soil conditions. Current practice dictates that practitioners rely on personal experiences or available published project case studies that are limited in scope and applicability as they are typically aimed at achieving a project specification. There is a reluctance to adopt RDC as a ground improvement technique as there is uncertainty regarding its limitations and capabilities.

The underlying objective of this research is to quantify the ground response of the 8-tonne 4-sided impact roller. This research has used full-scale field trials and bespoke instrumentation to capture the ground response due to dynamic loading in homogeneous soil conditions. It was found that towing speed quantifiably influenced the energy imparted into the ground, with towing speeds of 10-12 km/h found to be optimal.

Targeted full-scale field trials were undertaken to quantify the depth of improvement that can be achieved using RDC. Field results were compared to a number of published case studies that have used the 8-tonne 4-sided roller. Significantly, separate equations have been developed to allow practitioners to predict the depths that can be improved for the two major applications of RDC: improving ground in situ and compacting soil in thick layers.

Finally, the in-ground response of RDC was measured using buried earth pressure cells (EPCs) and accelerometers. Force was determined from the measured change in stress recorded by EPCs whereas displacement was inferred from the double integration of acceleration-time data to give real-time load-displacement behaviour resulting from a single impact. The energy delivered to the soil by RDC is quantified in terms of the work done, defined as the area under the force versus displacement curve.

Quantifying the energy imparted into the ground in terms of the work done is a key difference from past studies. Previous estimates of the energy delivered by impact roller at the ground surface has traditionally been predicted based on either gravitational potential energy (12 kJ) or kinetic energy (30 kJ to 54 kJ for typical towing speeds of 9 to 12 km/h). The two different values have caused confusion amongst practitioners. This research has determined that the maximum energy per impact that the 8-tonne 4-sided impact roller is capable of imparting to the ground is between 22 kJ to 30 kJ for typical towing speeds of 9 to 12 km/h.

Quantifying the effectiveness of the 8-tonne 4-sided impact roller in terms of towing speed, depth of influence, and soil response measured via real-time measurements will lead to a greater understanding of the practical applications and limitations of RDC. Significantly, more accurate assessments of RDC will reduce design conservatism and construction costs, reduce instances where the predicted ground improvement does not occur and enable RDC to be used and applied with greater confidence.

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