Search results for: Free PDF Quiz 2024 High Hit-Rate EMC D-PM-IN-23 Latest Test Report 🍂 Search for ✔ D-PM-IN-23 ️✔️ and download exam materials for free through [ www.pdfvce.com ] 🦞Questions D-PM-IN-23 Exam
-
Ground-Structure Interaction
Panel Discussion
-
2019 Queensland AGS Symposium
Risk & Resilience in Geotechnical Engineering
Dr Tim Mote, Deryk Forster, Dr Bindumadhava Aery, Ian Shipway, David Folan, William Eom, Greg Anderson, Amir Shahkolahi, Mehdi Davari, Stephen Buttling and Jun Sugawara
-
An alternative view on geotechnical parameters for tunnel design in Sydney
Bertuzzi (2014) presented an update of the geotechnical design parameters previously proposed by Bertuzzi and Pells, (2002). The updated parameters focused on tunnel design with two sets of parameters introduced to cater for different design approaches dependent on the scale of the assessments. The proposed parameters provide a useful starting point and reference for practitioners working on tunnel design. However, Bertuzzi (2014) provides no guidance on the appropriate use in a model which may, in some cases, result in discrepancies between the two different design approaches and expected range of ground behaviour. This paper provides additional comments on the differences between the two design approaches and guidance on the use of updated design parameters. The objective is a compatible behaviour independent of design approach chosen. In addition, design parameters may vary dependent on different interpretations and new sets of parameters based on the discussions in this paper are suggested as an alternative reference.
-
Revisiting the applicability of Voussoir Beam Theory for tunnel design in Sydney
The design of semi flat-roofed tunnels, i.e. with a high arch radius to roof span ratio, in Sydney has been proven successful over time. The horizontally bedded nature of Sydney’s Hawkesbury Sandstone draws designers to the voussoir beam theory. Such analogy and the associated method of analysis can be easily implemented in computer spreadsheets, which significantly facilitates the design of semi flat-roofed tunnels in geological conditions such as Hawkesbury Sandstone. Like any other engineering simplified model or theory, the voussoir beam theory has some limitations. However, it seems that some of these limitations are not well understood and often ignored and/or misinterpreted. Such lack of understanding of the theory and its limitations often raises question about the applicability of the analytical solution in practice, misleading engineers to believe that the only reliable and comprehensive design method is through numerical analysis such as Distinct Element Method (DEM). This paper investigates the applicability of the analytical or closed-form solution of the voussoir beam theory through comparison with numerical modelling, focusing on some of the perceived limitations and their impact on the design of tunnels in Sydney. The results illustrate that the voussoir beam theory can be confidently used in practice if its limitations are well understood and good engineering judgment is applied to take the local geology into account. In addition, the results also demonstrate that some of the limitations can be on the conservative side. For example, the potentially positive effect of high horizontal stresses ignored in the voussoir beam theory may explain why some of the unfavourable conditions are less pronounced in practice.
-
South Australian collapsing soils
The study was designed to evaluate and compare typical collapsing soils from South Australia and to evaluate the use of such soil in pavement construction after chemical stabilization with cement and rice husk ash (RHA). The three soils in the study were classified as silty sands, usually with calcium carbonate. Shear strength decreased markedly with inundation. In the natural state, a severe degree of collapse could be reached following saturation. The stabilization of soil from Port Augusta resulted in reduction of the collapse index and an increase of the shear strength. Even after heavy compaction, the soil still had slight potential for collapse upon wetting. On the other hand, the chemically stabilized and compacted soil exhibited minor swelling upon wetting. The saturated shear strength of compacted soil increased when compared to that of undisturbed soil. For evaluation of application of the stabilized soil in pavement construction, the California Bearing Ratio (CBR), unconfined compressive strength and durability were determined. Based on the soaked CBR and strength tests, the non-stabilized, compacted soil was classified as a good sub-grade. The chemically stabilized soil with a low percentage of additives could be used as a sub-base. However durability testing indicated stabilization with either 6% cement and 2% RHA is required. Further work is required to determine the resilient properties of compacted stabilized collapsing soil.
-
Geotechnical And Coastal Engineering Aspects Of Risk Assessment For Coastal Protective Works And Assets
There are numerous coastal assets in NSW that are located in areas subject to beach erosion and hence are at potential risk of damage in coastal storms. Two risk assessment procedures are presented herein, namely:
- a geotechnical risk assessment of foreshore stability and protective works that was applied by Jeffery and Katauskas on the north coast of NSW and
- a coastal engineering risk assessment of damage to assets along beaches in Warringah as applied by WorleyParsons for Warringah Council.
The geotechnical assessments of risk to property and risk to life were based on the AGS (2007) procedures. These risk assessments are seen to be useful in informing emergency services of the potential need for evacuation of some properties in coastal storms, and allowing a framework for monitoring of the foreshore to be developed and implemented.
The coastal engineering risk assessment comprised the development of:
- an inventory of individual property details relevant to consideration of risk,
- resistance ratings for existing protective works located along the beachfront (e.g. based on toe levels and rock size),
- procedures for assigning likelihood ratings for occurrence of damaging events (based on the position of the Immediate Coastline Hazard Line relative to the seaward face of an asset, assuming no protective works),
- procedures for assigning consequence ratings to expected property damage (including consideration of whether the asset was supported on piles and the likely effectiveness of protective works seaward of the asset) and
- an overall risk analysis matrix used to derive a risk rating from different combinations of likelihood and consequence ratings.
These coastal risk assessment procedures are noted as being useful in preparing in advance for coastal storm
events. -
Mechanical Stabilization Of Unbound Layers: Effect Of Geogrids On Low Strain Behaviour Of Granular Materials And Essential Characteristics For Optimum Performance In Permanent Roads
The use of geogrids in mechanically stabilized earth (MSE) structures and for trafficked areas over soft soils is well known. The essential characteristics of geogrids for MSE have well established over many years and are incorporated into national and international codes and standards. However, the mechanisms by which geogrids function in permanent roads and therefore the essential characteristics of geogrids operating at low strains in this application have often been disputed. This paper will present results from several recent research projects that identify the stabilization mechanisms that operate and identifies essential characteristics for geogrids in this function. A comparison is made between the stabilization function of geogrids and tensioned membrane reinforcement function of geogrids and the significance of this functional difference in the selection of essential geogrid characteristics for specification purposes. Such an understanding is essential if specifications are to protect designs that utilise the benefits of mechanical stabilization to increase pavement life.
-
A micromechanics-based approach as an alternative to the experiment to characterise the fatigue behaviour of pavement materials
Pavement materials feature a heterogeneous microstructure, consisting of differently-graded granules randomly distributed in the material domain and/or connected by a binder matrix. This microstructural feature significantly contributes to the complicated fatigue behaviour of the materials when subjected to traffic loadings. Existing experimental methods for pavements have faced difficulties in controlling the material microstructure and its effects on the macro-behaviour. This results in scattered experimental data often observed in the fatigue tests of pavement materials, making it hard to characterise the material behaviour and quantify parameters for practical design. This paper presents a micromechanics- based numerical approach for characterising the fatigue behaviour of pavement materials. This numerical approach can physically reproduce the heterogeneous microstructure of the materials with different gradations thanks to the application of Discrete Element Method (DEM). Moreover, the incorporation of a damage-plastic contact model enables DEM to capture the fatigue behaviour of pavement materials. Through several numerical examples, the numerical approach is shown to predict well the fatigue behaviour and real crack development in pavement materials. Given its better controllable and cost-saving features, this numerical approach can be an effective alternative (to experiments) to assist engineers in the design of road pavements.
-
Experimental and numerical investigation of rate and softening effects on the undrained shear strength of Ballina Clay
We present the basic components of a methodology to investigate two key aspects of the mechanical behaviour of some natural clays, namely the dependency of the undrained shear strength on the rate of shearing, and the softening response at large strains. For that, we will use a blend of novel experimental testing procedures and cutting-edge computational techniques, currently under development at the University of Newcastle. Measurements of the shear stress-strain response under undrained conditions will be obtained using a newly developed miniature vane shear apparatus, featuring automatic control of the blade rotation velocity. Laboratory tests will be complemented with large deformation numerical simulations of the vane test with the coupled Eulerian-Lagrangian method. For that, an appropriate constitutive model is implemented in ABAQUS/Explicit, able to simulate the visco-plastic strain-softening response of soft clays. Testing will be performed on the soft estuarine clay samples retrieved from the national geotechnical soft soil field testing facility, established in Ballina, NSW. With the focus being on Australian soft clays, the long-term goal of this study is to improve the procedures for performing and interpreting in situ tests included in Australian Standards.