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Improvements to the Australian wheel tracking protocol for asphalt deformation resistance measurement
With the introduction of new pavement technologies, asphalt performance-based mixture design has become increasingly important in the pavement industry. A key consideration for performance-based mixture design is to ensure that laboratory performance-indicative tests link sample preparation and test parameters to expected in-field conditions appropriately. For the performance assessment of deformation resistance, the most common test method in Australia is the wheel tracking test. Recent research involving the assessment of stone mastic asphalt deformation resistance properties identified several elements of the Australian wheel tracking protocol requiring improvement. This paper details recommendations to improve the Australian wheel tracking protocol in terms of sample preparation and laboratory test parameters, to increase reliability of the results and to better link laboratory assessment to in-field performance.
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Collaboration Between Industries For The First MRT Line In Malaysia
This paper presents a summary of some of the collaborations that were undertaken to ensure the successful completion of the Klang Valley Mass Rapid Transit (KVMRT) – Kajang Line in Kuala Lumpur, Malaysia. As a developing nation with the will and desire to construct the first MRT Project, the local joint venture company of MMC and Gamuda was presented with many challenges. To start the ball rolling, the team would have to make do with predominantly local resources. To meet the stringent requirements of the tunnelling fraternity and the underwriters, collaboration with the client and upskilling of the local industry players were necessary. While many of the points mentioned herein may be a norm in countries where Metro projects are already mature, the local construction industry in Kuala Lumpur still had a lot of catching up to do. The collaboration with the client, the site investigation contractors, laboratory/ testing agencies and geophysics service providers was instrumental in making the project a success.
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The weighted plasticity index in road design and construction
The commonly used Plasticity Index (PI) test disposes the material retained on the 425 micron sieve, thus is not representative of the whole sample. In Australia, residual soils are very common, with a high granular content in โclayeyโ soils. Thus a significant portion of the sample is discarded for the PI (only) test. The weighted plasticity index (WPI) accounts for the portion used in the PI test and this is important for classification of residual soils. The background and historical development of the WPI is presented with its relationships, applications and limitations. Changes in testing Standards affects the correlations expected with the original WPI classification.
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Risk Prediction Model for Formation of Underground Cavities and Sinkholes due to Defective Sewer Pipes
Sinkhole formation due to internal erosion around defective sewer pipes is identified as a serious threat in urban infrastructure system. Post-repair and rehabilitation after pipe failure are not effective as emergency pipe repairs are very costly and pipe failure leads to various public and environmental consequences. Only a few studies have been conducted on the prediction of the risk of ground erosion around pipe defects. Therefore, the main objective of this article is to propose a model which can predict the risk of formation of sinkholes around sewer pipelines based on the weighted factors method when a pipe defect is certain. The proposed methodology relies on different factors which contribute to void development and severity of the consequences. The Risk of Erosion (ROE) combines the effect of Likelihood of Erosion void formation (LOE) and Consequence of Erosion cavity formation and ground failure (COE). The LOE rating is related to many parameters, including soil properties, hydraulic conditions, and pipe defect characteristics, while the COE rating is related to the environmental, economic, and social consequences of pipe failure. Therefore, this model, which can predict the risk of developing a sinkhole close to an existing pipe defect, will enable sewer assets maintenance teams to evaluate each pipe and prioritize the maintenance and rehabilitation work based on the risk to each pipe.
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The strenuous Leura weak sandstone
The Leura weak sandstone (LWSS), the highly weathered shallow parts of the Banks Wall Sandstone, is one of the dominating surface rocks in the Blue Mountains region in the Sydney Basin. While many infrastructure projects constructed in the Blue Mountains region involved very weak, highly friable LWSS, the mechanical properties of the rock are poorly understood. In this work, a detailed characterization of the rock is presented including sampling and sample preparation, grain size distribution, and results from scanning electron microscopy (SEM), permeability tests, uniaxial compressive strength (UCS) tests, triaxial compression tests, and erosion tests.
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What is the total suction of soil at oven dry?
The values of total suction (moisture potential) ascribed to the oven dry condition by various authors are reviewed. An explicit calculation of the limiting total suction imposed by a drying oven is described. The variables are the oven temperature together with the relative humidity and temperature of the ambient air that is necessarily admitted into the oven. The calculation requires reference to psychrometric relationships between relative humidity, temperature and humidity ratio. These relationships are accessible in commonly available psychrometric charts as well as in other forms. For typical laboratory conditions, the limiting total suction imposed by a drying oven will fall in the range 5.8 to 6.0 logkPa (6.8 to 7.0 pF). The direction and magnitude of the change in total suction that occurs when an oven dried soil sample cools from oven temperature to room temperature is also considered by reference to published experimental data and the known temperature trends of the physical phenomena associated with suction. A small set of experimental measurements of the humidity over soil samples cooled from near oven dry to room temperature are reported. These experiments were aimed at the narrow question of the direction and magnitude of the change in the soil suction upon cooling from drying oven temperature. Some published data on the suction attained when a soil is dried to zero moisture content by a room temperature process are also reviewed.
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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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Proximal Sensing Of Density During Soil Compaction By Instrumented Roller
The measurement of density or void ratio during the compaction of geomaterials (soils and unbound granular materials) in the field during road construction is essential for superior performance. The specifications adopted by the road authorities worldwide are exclusively based on density. However, estimating density evolution proximally or non-destructively is challenging. Conventional field-based density measurement techniques are hazardous, slow to use and are point-based measurements.
This study developed a novel methodology to estimate the density of geomaterials non-destructively in real-time during the compaction process. The methodology included measuring the surface deformation using Light Detection and Ranging (LiDAR) systems attached to rollers and developing physics-based 1-Dimensional and machine learning (ML) based constitutive models to relate the measured parameters to the density. The developed methodology was validated in an indoor environment where a large soil box (dimensions: 7.5 mร4 mร0.8 m) was fabricated and a well-graded sand in 5 layers of 100 mm was compacted using a 1.5-tonne instrumented roller. The measurement of deformation provided an opportunity to estimate the density in real-time. The estimated density using 1-D model and a ML based classification model had an error of 20% and 16% respectively when compared to density measured from Nuclear Density Gauge (NDG).
This novel instrumentation allowed the density to be measured during compaction with high accuracy, which presents an unprecedented advantage over other conventional approaches, which are intrusive and pointwise, thereby ensuring that the road will be constructed expediently and will function satisfactorily, minimising the occurrence of premature failures. The continual measurement of density during compaction will also facilitate maintaining uniformity of the density, thereby reducing the potential for excessive differential deformations.
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Compaction Density Of Residual Soils And Weathered Rock
Residual soils, weathered rock and overburden quarry fill represent a significant amount of fill used in road embankments. These have a high stone content which affects both the bulk density and the accuracy of the quality tests associated with compaction control. Density is the parameter that one is most likely to have a good estimate. It is used as an input in settlement and slope stability analysis of fills. The assumed density value may become critical for high fills or when embankments are placed on soft and compressible soils. Density testing is widely used in earthworks quality control (QC) and is arguably the parameter with the largest database. Construction records from compacted embankment fills from QC for major construction projects are used to check this most basic and simplest of design assumptions. Observation of commonly used density value in geotechnical investigation and design reports compared with construction records show that industry has a persistent error in analyses for an input that is arguably the easiest and simplest input parameter to determine. Three cases studies are used to illustrate the influence of an assumed density. Two of these cases led to contractual and legal issues as this simple parameter affects quantities placed, settlement and stability analysis.
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The consolidation behaviour of alluvial soft clay in Gladstone, Central Queensland
Infrastructure, port facilities and road embankments built on existing soft clay sediments impose various geotechnical challenges. A trial embankment has been constructed at the Wiggins Island Coal Export Terminal (WICET), Gladstone, Queensland to investigate the consolidation behaviour of soft, quaternary alluvial sediments. Large settlement associated with prolonged consolidation time is of particular interest. To predict the magnitude and rate of settlement to allow the design to meet often tight construction schedules, consolidation parameters such as compression and recompression indices, pre-consolidation pressure, coefficients of primary and secondary consolidation need to be reliably estimated. In this paper the consolidation properties of soft clay at WICET were evaluated using three approaches, which are: i) laboratory testing (oedometer); ii) field testing (CPTU with pore pressure dissipation); and iii) back analysis of field monitoring results from an instrumented trial embankment. Derivation of the parameters from the above approaches are discussed, with the results compared and assessed. The benefits of back-analysing instrumentation data to improve the construction programme are also discussed.