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Improving traffic load outcomes for impact assessment of existing pipes under new infrastructure
Infrastructure upgrades often encounter buried pipes that are impacted by traffic loading. Depending on the outcome of impact assessment, pipe diversion or protection works are often required. Given the significant constraints in working space, working hours and traffic management, pipe diversion or protection works often result in significant impacts on project schedule and cost.
An integral part of impact assessment is the evaluation of vertical stress transferred to pipe level from traffic loads. Australian Standards such as AS 5100.2(2017) and AS/NZ 3725(2007) provide guidelines on stress distributions under traffic load, treating the ground as a “uniform elastic soil mass”. Given the economic implications, the authors consider that a multi-layered approach offers benefits compared to this approach by accounting for greater vertical stress dissipation resulting from overlying stiffer pavement layers.
Multi-layered stress analyses are routinely carried out by pavement engineers to evaluate stresses within pavement layers and the pavement subgrade. However, layered modelling techniques are often not applied in impact assessment of pipes buried under pavements. This paper presents multi-layered stress analysis for a number of load cases including both road and light rail loadings. Typical pavement configurations have been considered and a series of plots have been developed giving vertical stress distributions under these conditions. These vertical stress distributions are compared with those resulting from the AS 5100.2(2017) and AS/NZ 3725(2007) approaches to demonstrate the potential benefits of adopting multi-layered stress distributions.
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Decked Rockfill Dams In Tasmania
The construction of dams for the seasonal storage of water began with the arrival of European settlers in Tasmania during the early part of the 19th century. A variety of small water storages with dams <15m high were constructed to meet the needs of local communities. The construction of ‘large dams’ began in Tasmania with the Lower Reservoir during the 1850s. It was Hobart’s first seasonal water storage.
During the second half of the 19th century three water supply dams were completed to serve Hobart and Glenorchy. These dams, Lower Reservoir, Upper Reservoir, and Tolosa Reservoir, had a combined storage volume of 945,000m3 (ANCOLD, 1990). With developments in mining, agriculture and industry the need for reliable supplies of water increased notably. The result was a near exponential growth in the construction of large dams (as defined by ANCOLD) for water storage during the 20th century.
The majority of these dams were rockfill (36) and earthfill (34) embankments. Other types included concrete gravity (7), concrete buttress (2) and concrete arch (5). There are 21 decked rockfill dams, i.e., ~25% of all large dams. Most of these are concrete faced rockfill dams (CFRDs), two are bituminous concrete faced rockfill dams (BFRDs). The first CFRD was constructed in 1907-8; the last was completed in 1993. This paper covers the development and performance of decked rockfill dams in Tasmania.
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Rainfall data analysis at Newport and the relationship to landsliding in Pittwater
It is well recognised that the most common natural triggering factor for landslides is rainfall. A general relationship of more landslide events in wetter than average years was apparent from initial examination of the 195 landslide events on the database gathered as part of the National Disaster Mitigation Programme project to study the likelihood of landsliding in the Pittwater area. This paper reports the results of a more detailed analysis of rainfall data using daily rainfall and cumulative rolling totals from 2-day to 90-day periods. The resulting rainfall data was related to the landslide events on known dates which comprises only about 40% of the landslide database. No single pattern of results was available from the data. The chance of landslides occurring in Pittwater increases with higher 1-day rainfall. There is probably almost 100% chance of one or more landslides in the Pittwater area when the 1-day rainfall is 125mm or more. Days on which multiple landslides are likely to occur are often related to a maximum return period associated with 30 to 60 day antecedent rainfall. All the multiple landslide days are related to relatively long recurrence period rainfalls of about 20 years.
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Geotechnical challenges for on-site wastewater management in the Hunter Region
A large number and growing proportion of both single lot residential and larger scale new developments in the Hunter Region are not serviced by a conventional reticulated sewerage system. In such cases, wastewater treatment, its possible reuse and final disposal, is on-site, where the effluent is generated.
A range of geotechnical factors including the site geology, geomorphology, soils, availability and performance of geo and geosynthetic materials, along with climatic factors, have a bearing on the selection, design, sizing and performance of an on-site wastewater system which will perform adequately and meet regulatory requirements. Geotechnical skills in site and soil assessment are fundamental to and necessary for good on-site wastewater system design and to ensure that the environmental impacts associated with on-site wastewater management are minimised.
The Hunter Region displays a number of challenging geological settings and soil types for wastewater management. These include perched and shallow water tables, sensitive aquifers, floodplains and coastal lake and estuary catchments. Soils include sodic, dispersive and duplex soils and high permeability sandy soils with limited capacities for wastewater assimilation. Hydraulic and nutrient loading capacities of some of the region’s soils are limiting and present a challenge to designers.
An understanding of transport and assimilation of nutrients and pathogens through permeable materials is significant in understanding the potential contribution of on-site wastewater management systems to surface and groundwater contamination and the protection of those sensitive receiving bodies by appropriate design.
This paper reviews the geotechnical aspects of on-site wastewater management in the Hunter Region and illustrates, with a number of case studies, both the problems commonly encountered and their possible solutions.
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Use of dredged materials in a materials offloading facility embankment, Barrow Island, Western Australia
This paper describes aspects of the geotechnical design and construction of a Materials Offloading Facility (MOF) embankment up to 20m high, that consists of material sourced from dredging and plant site development works for the Chevron-operated Gorgon Project – the largest single resource project in Australia’s history. The MOF is located on the eastern side of Barrow Island (BWI), a Class A Nature Reserve. Several significant challenges were faced in sourcing the range of materials required for the MOF. These challenges related to the local geological conditions on BWI and in the near shore environment proposed for the dredging works. Source rock from BWI was used in construction of the initial section of causeway from Town Point to the Pioneer MOF (PMOF) platform, however, this paper only refers to the PMOF and beyond to the MOF Head where the LNG Jetty Abutment structure is located. The materials for these works were sourced from the near shore environment and generally comprised carbonate rich limestone and calcarenite. These dredged materials were considered primarily as rock fill and methods for sourcing and characterisation of the rock fill, selection of parameters, geotechnical analyses and relevant construction details are also discussed in this paper. Design parameters, based on particle size distribution, unconfined compressive strength, particle shape and roughness characteristics were selected and slope stability analyses were undertaken using the limit equilibrium method. Load deformation analyses applied the finite elements coded in the latest readily available geotechnical software. Potential creep and seismic effects were taken into consideration. High strength geotextile reinforcements were used to achieve the required long term embankment stability. Various compaction methods including the relatively new Cofra Dynamic Compaction (CDC) method were adopted at different levels and locations of the embankment and innovative Seismic Surface Wave geophysical methods were combined with Plate Load Testing for verification of the heterogeneous fill materials to ensure the design assumptions would be realised.
The Gorgon Project is operated by an Australian subsidiary of Chevron (47.3 percent interest), in joint venture with the Australian subsidiaries of ExxonMobil (25 percent), Shell (25 percent), Osaka Gas (1.25 percent), Tokyo Gas (1 percent) and Chubu Electric Power (0.417 percent).
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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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Innovative Use of Recycled Rubber and Mining By-Products for Sustainable Rail and Road Infrastructure
Encouraging more real-life applications of circular economy perspectives in transportation infrastructure design and construction, this paper focuses on utilising granular wastes (i.e. coal wash and steel slag) from coal and steel mining for port reclamation, and recycled rubber elements including granulated rubber particles, rubber mats, tyre cells and truck tyre segments for stabilising track formations and reducing ballast degradation. The mixtures of coal wash and steel slag were optimised through a proposed novel customer-made selection criteria and verified through field trial. Moreover, the promising damping property of rubber (with respect to strain energy capacity) was fully exploited to design substructure energy retention layers to minimise deformation and degradation of track elements including impact damage caused by track irregularities such as rail corrugations. The large-scale laboratory testing results obtained using the large-scale triaxial, Process Simulation Prismoidal Triaxial Apparatus, and the prototype National Facility for Cyclic Testing of High-speed Rail and the field trial verify that rail tracks altered with the above-mentioned rubber elements easily satisfy the specified standards and are even superior to conventional ballast tracks in terms of degradation, deformation, stress distribution, and track vibration. In addition, these environmentally friendly approaches promote the reuse of mining by- products and discarded tyres and conveyor belts in transportation infrastructure while providing long-term cost benefits that can save millions of dollars annually in track maintenance and quarrying natural rock aggregates.
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Implementation of the AGS geotechnical data transmission format: the Brazilian experience
In the technology age, when cloud computing and artificial intelligence are prominent, the Association of Geotechnical and Geoenvironmental Specialists (AGS) digital data format gains its greatest importance. This paper presents a case study using the AGS digital transmission standard for geotechnical investigations in Brazil. The AGS data transmission standard developed in the United Kingdom is discussed with reference to reporting qualities in terms of flexibility and robustness. Next, two sectors in Brazil that started using the AGS format before it was officially implemented in the country are presented. It includes highways operated by private companies and academic researchers focused on the application of Artificial Intelligence and Data Science techniques to a national geotechnical investigation Big Data. Hence, the urgent need to implement a standardized format for geotechnical data transmission; as well as the opportunities that it presents, such as the integration with Building Information Modelling (BIM) software. It includes information for maintenance, operation of infrastructures and the development of automated geotechnical correlations. In conclusion, the case study indicates that, if the digital demands are not met by the official standardization in Brazil of geotechnical data transmission, private and scientific researchers may force this to occur through widespread use.
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Landslide failure perspectives in practice in South East Queensland
Quantitative Risk Analysis (QRA) is one of the tools used in Landslide Risk management. Ideally its matrix approach should provide similar conclusions when used by different geotechnical professionals. However in practice some differences in interpretation and application occur. This assessment tool is examined for various case studies in south east Queensland.
By examining landslide events that have occurred with the benefit of hindsight in order to calibrate the approach, one finds that the interpretation of consequences has scope for variation in the application of this QRA tool if it is applied as is. The perception of risk governs landslide risk management in practice in Queensland. Other consequential variables also have a significant effect and may govern the result of the risk assessment process. The QRA is a decision tool with risk analysis at its core, but users must also not overemphasise the analysis in a risk assessment approach.
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In-situ Waste Characterisation For Primary Settlement Assessment For High Embankment Built Over Municipal Solid Waste
Due to land restriction, some sections of several highway and railway projects have to be constructed over poor and uncommon foundation such as waste materials placed as part of the preceding landfill operation. Waste/Municipal Solid Waste (MSW) materials especially those comprising high amount of organic and readily degradable materials are highly compressible and have high variability in composition and void distribution. Conventional geotechnical laboratory testing and limited in-situ testing are often insufficient to characterise waste material. A design of field trial to understand the settlement characteristics will also require a reasonable understanding of the properties of waste materials.
This paper presents a basic methodology for in-situ characterisation of waste materials to enable the assessment of geotechnical properties of these materials on the basis of their composition and organic content. This includes the selection of suitable drilling method to allow for a good quality and continuous waste sample recovery. From such characterisation, a dimensionless Waste Compressibility Index (WCI) can then be derived based on procedures given in the published literature. The WCI value can then be correlated with compression ratio used to analyse primary consolidation settlement.
A case study is presented in this paper where a railway embankment was to be built over a landfill foundation consisting of existing Municipal Solid Waste (MSW) in the east coast of Australia. The foundation was treated by means of high surcharge. The abovementioned methodology has been used in the design to characterise MSW materials and assess primary settlements. The back-analysis by using settlement monitoring data indicate a reasonable agreement between the WCI related to the back-analysed compression ratio and the estimated WCI values. This agreement was obtained despite the variability in the aforementioned correlation. It shows that a basic methodology for in-situ waste characterisation on the recovered waste sample was able to provide a reasonable estimate of compressibility parameters for the purpose of analysing primary settlements.