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Thermal properties of some Melbourne soils and rocks
The thermal conductivity of soils and rocks is an important property for the design of thermally active ground structures such as geothermal energy foundations and borehole heat exchange systems. This paper presents the results of a laboratory study on the thermal conductivity and volumetric heat capacity of soils and rocks from around Melbourne, Australia. The thermal conductivity and volumetric heat capacity of six soils were experimentally measured using a thermal needle probe and the thermal conductivity of three rock types were measured using a divided bar apparatus. Soil samples were tested at a wide range of moisture contents and densities. The results demonstrated that the thermal conductivity varied with soil moisture content, density, mineralogical composition and particle size and that volumetric heat capacity was strongly dependent on the moisture content of the soils. Rock samples were tested dry and water saturated. Rock samples demonstrated an improvement in thermal conductivity with an increase in density when dry. However, when water saturated, siltstone and sandstone rocks showed no significant correlation between density and thermal conductivity. This was attributed to both variations in mineralogy and anisotropy. The thermal conductivity and volumetric heat capacity data obtained from this study provides an initial dataset of soils and rocks thermal conductivities for the design of thermally active ground structures installed throughout Melbourne, Australia.
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A Comprehensive Geotechnical Investigation For The New Bridge Over The Clarence River At Harwood
The new bridge over the Clarence River at Harwood forms an integral part of the Pacific Highway upgrade in northern NSW and is currently under construction by the Acciona-Ferrovial Harwood Joint Venture (AFHJV). The proposed bridge extends 1.5km between abutments, spans the Clarence River with a water span of approximately 560m and is founded on 2m to 2.4m diameter driven hollow steel tubular piles to over 60m depth in some areas.
The underlying geology of the site consists of 30 to 40m of soft estuarine silts, clays and loose to medium dense sands underlain by saturated basal sands, gravel and cobbles up to 25m in thickness. Historical ground investigation information has thus far failed to provide confidence in the characterisation and engineering properties of this basal gravel and cobble layer due to limitations with conventional SPT, CPT and drilling techniques. The focus of this paper is primarily on characterisation of the basal sand and gravel units encountered in the River and North portions which largely drove the selection of innovative ground investigation techniques and methodologies.
A comprehensive ground investigation (GI) scope was proposed to support the bridge detailed design phase undertaken in parallel with the field works. This paper presents a perspective on the challenges of developing a ground model within this complex geological sequence and how this was addressed through a diverse, state-of-art GI campaign. It presents a methodology to derive ground profiles and soil parameters from advanced geotechnical testing and provides comparison of these innovative techniques against industry standard approaches.
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A Perspective On Rolling Dynamic Compaction Research Collaboration Between Industry And Academia
In the three to four decades since the Broons Group (formerly Broons Hire) introduced the 4-sided “square” impact roller into Australia in the mid-1980s, collaboration between industry, including consulting and contracting, and universities has been strong. This paper is a personal view on how this collaboration has developed and progressed over time. The paper outlines aspects of historical collaboration between the industrial and academic sectors when it comes to rolling dynamic compaction (RDC), or impact rolling. It is, however, within the last 18 years or so that there has been an acceleration of this collaborative effort. In summary, modelling and numerical studies have been carried out Adelaide and Sydney Universities; physical installations and site studies at Adelaide University; and testing techniques at Adelaide and Monash Universities. Most of these activities have involved the RDC suppliers and contractors, to some extent. The results of these efforts have included the construction of scale model test beds, instrumented ground treatment pads, undergraduate and post-graduate projects, including PhD theses, and numerous published collaborative case study papers. While RDC has provided a fresh and relatively un-researched topic for academic activity, the collaborative research activities and the interest of academics has assisted industry with development and marketing of the technology. Several aspects of the extensive collaboration between industry and academia are addressed, covering a broad view of the topic. In particular, the research initiatives, undergraduate and post-graduate research topics and co-authored technical papers resulting from this collaboration are highlighted.
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Case Study Of Seven Ground Improvement Techniques Implemented At Coal Export Terminals On Kooragang Island, Australia
This paper describes a case study in which various ground improvement techniques were implemented to enable the development of one the world‟s largest coal export facilities. To service the Hunter Valley coal industry, Coal Export Terminals (CET) with associated rail and coal handling/train unloading infrastructure have been constructed on Kooragang Island, Newcastle, New South Wales, Australia, in the last decade. The coal terminal expansion has brought about fundamental geotechnical challenges. Kooragang Island was formed by dredging and infilling between and around former islands and delta features of the Hunter River estuary. The presence of recent estuarine and alluvial soft clay deposits combined with variable thicknesses of fill comprising dredged materials, coal washery reject and steel slag, introduced significant geotechnical issues in relation to bearing capacity, stability and long term total and differential settlements. To support combined stacker/reclaimers with up to 24m high coal stockpiles, rail loop realignment and a new rail flyover, Ground Improvement was required to address the above issues. In order to limit the post-construction settlements and to satisfy the settlement criteria for machinery and railway operation, a suite of seven ground improvement techniques has been employed to suit the specific performance requirements, programme and geotechnical conditions across the site. These consisted of Wick Drains, Dry Bottom-Feed Stone Columns, Wet TopFeed Stone Columns, Dynamic Replacement, Mass Soil Mixing, Deep Soil Mixing and Rigid Inclusions. All of the above methods were successfully applied over the course of an eight year development period on a design and construct basis. The process of using ground improvement techniques, their construction restraints and geotechnical design considerations are discussed. The performance based on monitoring data collected under operating conditions is presented.
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Shallow Ground Improvement For A New Rail Depot / Maintenance Facility In Sydney
A new rail maintenance and stabling facility comprising rail sidings and associated maintenance buildings / facilities is to be constructed in a heavily urbanised area in Sydney, NSW. The site will be on a raised earthworks development platform for flood mitigation purposes.
Ground conditions include variable non-engineered surficial fill over up to 4m thickness of variable density alluvium (dune sands) overlying dense to very dense Botany Sands above deep alluvium to over 40m depth with a shallow groundwater level. Some site areas have been previously loaded by former development.
Identified geotechnical risk relates to potential unacceptable ground surface settlement of the development due to embankment loading of low density variable surface soils against the need to limit total and differential settlement of rail track-slab and building foundations within specified design and operational tolerances for a design life of 75 years.
A ground improvement solution was required to improve these surface soils to reduce the potential for both total and differential settlement under loading from the proposed earthworks and structures. The achievement of differential settlement criteria is critical to the long term performance of the track slab system, particularly at the interfaces with buildings.
This paper describes the site ground conditions, the ground improvement options considered and the selection of high energy impact compaction (HEIC) as the optimal solution for the proposed site development. HEIC trials including performance validation of the ground improvement are described. Site specific Specifications were then developed for HEIC construction phase works. The trials also included noise and vibration monitoring to define construction control limits and buffer zone distances from sensitive adjacent areas including residential properties and a heritage building.
Significant cost savings and construction programme benefits are realised utilising shallow ground improvement methods compared to the other ground improvement options considered.
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Significance of considering soil-structure interaction effects on seismic design of unbraced building frames resting on soft soils
The current study carries out a comprehensive critical review on available and well-known research studies in the area of seismic behaviour of braced and unbraced building structures affected by soil-structure interaction (SSI). Based on the current review outcomes, it has become apparent that considering effects of SSI in seismic design of braced building structures is not necessary and assuming fixed-base structure is deemed to be conservative. However, SSI effects can amplify the lateral deflections and corresponding inter-storey drifts of unbraced building structures founding on soft grounds, forcing the structure to behave in the inelastic range, resulting in severe damage of the building structures. Consequently, seismic design procedure of unbraced building structures founding on soft soils without taking into account detrimental influences of SSI cannot adequately assure structural sufficiency and safety for the benefit of the community.
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How Wide Can A Rock Cavern Be Opened?
The largest known cave, Sarawak Chamber, which is in the Gunung Mulu National Park, Malaysia, is a remarkable natural wonder and measures 700m by 400m and over 70m in height. A cave of this size can fit the entire city streets and skyscrapers. Theoretically, empirical rock and structural mechanics principles could be used to interpret these physical phenomena of large span rock-opening structures. On this basis, hypothesizing a jointed-rock cavern could be supported by reinforced rock arch using rock reinforcement techniques formed by application of confining pressure via the bolts or cables, utilising the inherent strength of the rock to support the rock load above the opening. This reinforced arch is considered as a continuous arched-structural beam all along the cavern. Generally, rock caverns and tunnels are designed mostly to be arch shaped, either circular or parabolic. However, the function of arch shape, geometry, span and ratio of the rise of arch for rock excavations have seldom been discussed, together with rock reinforcement applied on the opening periphery. An investigation initiative is proposed to examine the maximum span of the opening with respect to the critical load of the arch for the opening; properties of rock mass; and other variable coefficients related to geometry of the arch. This is done by using the rock reinforcement method together with the Dinnik’s equation, which is a simplified rule with variable coefficients for the analysis of the elastic arch when the loss of stability occurs. A numerical model is conducted in this paper to get a preliminary concept and agreement on this combination applications between rock mechanics and structural design. A desktop investigation initiative is outlined at the next stage for further verification of the concept on how wide a rock cavern could be opened.
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Sinkhole threats management in urban developments
Subsidence and sinkholes in urban areas pose catastrophic consequences if not detected and addressed effectively. Such phenomena have been observed in recent new urban developments in Madrid (Spain), highlighting the urgency of soil treatment to mitigate these risks. Upon discovering significant underground voids, traffic was halted until viable solutions could be identified. Preliminary studies utilizing microgravimetry, ground-penetrating radar, and boreholes revealed the presence of large cavities due to karstification. Subsequent research proposed testing plans, inspection programs, and intervention methods to repair existing sinkholes and prevent future occurrences. Throughout this article, the most suitable investigations for such terrains are explained, following a detailed study in a test area that has served as the basis for establishing a methodology for future work. This research underscores the critical need for proactive measures, emphasizing the necessity of soil treatments within urbanized areas to efficiently address situations and mitigate the potentially catastrophic impacts of subsidence and sinkholes while fostering a sense of security and stability within the community.
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Application of a multi-technique ground engineering solution to overcome geotechnical and physical challenges in Docklands
A high-grade mixed-use development has been proposed in the heart of Melbourne, Australia situated on the banks of the Yarra River. The proximity of the project to an existing heritage-listed seawall dock structure required the detailed design and analysis of proposed foundation and retention system to ensure all adjacent structures were protected and the project specifications and performance criteria are met. The proposed project consisted of a single level basement in very soft clays with a high groundwater table and deep foundation piles socketed into a bedrock at depths exceeding 35m. This paper describes the methodical process of assessing and implementing a sheet pile solution to protect and maintain the integrity of the existing seawall for the enabling and pile installation works. The building is supported by deep foundation Continuous Flight Auger (CFA) piles with column loads exceeding 35MN with dynamic pile testing being carried out for performance verification. The paper also shares the application of the wet mass soil mixing (MSM) ground improvement technique combined with the conventional soldier piled wall for an internal deep excavation to construct the core and lift overrun structures for the building. The purpose of the MSM was to act as a bottom strut to a soldier piled wall and a barrier to control lateral and vertical flow of soft soils and groundwater.