Research-based computer games to train civil engineering students to be lifelong learners

In spite of vast efforts to adopt available information technology in higher education teaching and learning, the truth is that most of university students and academic staff make only limited use of communication technology. Selwyne [1] concluded that there is a growing need for the education community to account for the distinct ?digital disconnect? between the enthusiastic rhetoric and rather more mundane reality of university information and communication technology use. Recent advances in computer science and multimedia as well as optimistic effects of multifaceted modes of education on student learning, have encouraged teachers to look at adopting the new technology to improve students? learning experience. Chang et al. [2] have suggested that digital games can be powerful informal learning environments encouraging active and critical learning, supplementing traditional teaching methods. It is well accepted that well designed discipline based computer games can help with student learning process and experience in higher education. In this study, a computer game called ?Back to Bedrock? has been developed for soil Behaviour subject at undergraduate level and students? learning process has been monitored and evaluated. It was aimed to help Civil Engineering students with information collection methods, creative thinking, problem solving, and lifelong learning abilities, through a research-based computer game. The results of this project indicate that implementing innovative methods such as computer game based assignments can provide enjoyable competitive and cooperative learning environment enhancing students? learning motivation, and critical thinking abilities, improving the overall performance of students in the subject

General and Technical Considerations for Implementing High Speed Rail Systems in Australia

Australia has a number of medium speed rail services such as the Prospector, which runs from East Perth to Kalgoorlie, at speeds of up to 160 km/hr. Speeds as high as 210 km/hr have been reached by the tilt train from Brisbane to Rockhampton. Although there are a few medium speed rail systems in Australia, there is not a passenger rail transport with the high transit speeds seen in other countries. This paper presents the feasibility of implementing high speed rail systems in Australia by looking at the main elements that a high speed train is composed of. This paper also reviews the performance of high speed rail systems around the world and the factors contributed to their success made them successful. The main objective of this study is to look at how the solutions from overseas and how the technical requirements particularly the geotechnical aspects of tracks for a high speed rail system can be applied in Australian existing and new tracks. Australia has its own unique demographic, geographic and economic characteristics and the aim is to identify where there are overlaps between Australiaâs characteristics and countries with high speed rail systems. High speed rail transport might not necessarily be one the best solutions for the transportation at present in Australia, but it can be what a nation needs to succeed in its future transportation system

Improving geotechnical properties of closed landfills for redevelopment using fly ash and quicklime

University of Technology, Sydney. Faculty of Engineering and Information Technology.Many closed municipal solid waste (MSW) landfills are located near urban areas, even though originally established away from residential or commercial communities. Construction on top of closed landfills is generally a challenging task due to complex behaviour of creep, settlement and weak shear strength of waste materials. There is a high prospective to reuse these sites for redevelopment in spite of potential risk for human health and environment. The deep dynamic compaction technique is a common ground improvement technique due to its relatively economical and easy application for landfill sites. With deep dynamic compaction, large voids reduce and afterward other techniques such as cement, fly ash or lime grouting can further reduce the remaining smaller voids. Numerous studies have been conducted to treat and stabilise different types of problematic soils using fly ash with combination of lime. However, there is no comprehensive research on improvement of physical properties of MSW landfills using chemical admixtures such as fly ash and lime. This study presents the experimental and numerical results of employing fly ash (class F) and quicklime (calcium oxide) in stabilisation of municipal solid wastes. The waste materials, used in this study, were collected from a closed landfill in the south-west of Sydney. The samples were prepared by integrating MSW, with a mixture of fly ash-quicklime with a ratio of 3:1 in percentages of 5, 10, 15 and 20 of fly ash by dry weight of the MSW. An array of experimental tests has been conducted on treated and untreated MSW samples including sieve analysis, Atterberg limits, compaction, permeability, large direct shear, unconfined compressive strength and consolidated-drained triaxial tests. Results of this investigation are evidence for a significant improvement in geotechnical properties of MSW materials, mixed with fly ash and quicklime. It has been found that the chemical stabilisation effectively increases the maximum dry density, the compressive strength, the shear strength parameters, the stiffness and the brittleness index, while decreases the compressibility, the permeability coefficient and the optimum moisture content of the MSW. It has been quantified that by increasing fly ash-quicklime admixtures from 0 to 26.7% (0 to 20% fly ash) the internal friction angle increased from 29° to 39° and the cohesion intercept increased from 11 kPa to 30 kPa. Under an effective confining pressure of 300 kPa, the peak strength, the brittleness index and the Young’s modulus at failure increased from 600 kPa to 1150 kPa, 0.13 to 0.35 and 5.5 MPa to 28 MPa, respectively, by addition of 26.7% fly ash-quicklime admixture. The coefficient of permeability for untreated specimen was 6.2×10-8 m/s and it was reduced to 3.2×10-8 m/s for specimens mixed with 26% fly ash-quicklime (under average confining pressure of 250 kPa). The compression and the secondary compression indices decreased from 0.33 to 0.23 and 0.052 to 0.033, respectively. Moreover, increasing the curing time enhanced the unconfined compressive strength, the friction angle, the cohesion and the preconsolidation pressure of the treated specimens, whereas no change in the permeability coefficient, the primary compression index and the secondary compression index were observed. The findings of this study may facilitate the calculations of the bearing capacity and settlement as well as the slope stability analysis of chemically treated closed landfill sites. A finite element program, PLAXIS version 9, has been used to evaluate the settlement of the untreated and chemically treated landfill layers for 10 and 20 years after applying surcharge loads such as the traffic load. The effects of depth of stabilisation and the fly ash-quicklime content on vertical and horizontal displacements of the model have been investigated. Treated and untreated MSW parameters, used for the model, have been obtained from the results of the extensive laboratory program performed in this study. The numerical results indicated that treatment of MSW with fly ash-quicklime reduced the vertical displacement of the model under traffic load at the midpoint below the embankment. This reduction is more pronounced with higher fly ash-quicklime contents and deeper improvement of layers. For depths of 3m, 6m, 9m, 12m and 24m of the landfill improved with 26.7% fly ash-quicklime, the vertical settlements at the centreline of the embankment, 10 years after applying traffic load, were reduced by 20%, 32%, 40%, 46% and 58%, respectively. Horizontal displacements of the landfill model also significantly reduced in sections below the toe of the embankment, under traffic load. The reduction in horizontal displacements is more pronounced with improvement into deeper layers

Optimising the pattern of semi-rigid columns to improve performance of rail tracks overlying soft soil formation

With Australia facing a rapid increase in population in the next 30 years, the government is being proactive in handling the forecasted growth. The release of 2010 Metropolitan Transport Plan by the New South Wales (NSW) Government shows that the State of NSW will see an increase in commuter travel by rail. The NSW rail system is one of the most complex networks in the world and due to population growth, the network will require further expansion with construction of new railway lines partly on weak and marginal ground and will also require more frequent train running on existing lines. This study seeks to identify the effectiveness of semi-rigid inclusion ground improvement techniques particularly stone columns and deep soil mixing in controlling settlement of soft soils when placed under the dead loads of the rail structure and the large live loads of freight trains. The employed numerical study assesses the relationship between the column position in the track cross section and the overall settlement of the ballasted rail formation. The numerical results show that the overall settlement of the track reduces significantly with the use of columns close to the centre of the track and not just under the rail. In addition, application of one layer of geogrids between sub-ballast and sub-grade assists to reduce the maximum settlement of track decreasing the future maintenance costs

Parametric Study On Behavior Of Reinforced Soil Walls With Combined Horizontal And Vertical Geosynthetics

The reinforced soil system employing geogrids, as a cost effective reinforcement technique, has come to play an important role in a variety of civil and geotechnical engineering applications. In regular reinforced soil wal1s, the reinforcements are usually laid horizontally in the soil. In this study, the behaviour of reinforced soil retaining walls with combined horizontal and vertical reinforcements are investigated experimentally as well as numerically. The results, indicating the effects of vertical reinforcement inclusion, are compared to conventional reinforcing types under static and dynamic loads. The performance of retaining walls employing vertical reinforcement in conjunction with horizontal reinforcement is convincing from the results of the shake table tests conducted by the authors. In this paper, PLAXIS, well-known geotechnical software, is used for conducting a series of pararoetric studies on behaviour of reinforced soil walls under construction and subject to earthquake loading, incorporating the vertical reinforcement. The vertical reinforcement layout and its strength are among the major variables of the investigation. The geometry of the model, soil properties and reinforcement characteristics have been kept identical in all different cases selected for parametric studies. The performance of the wall is presented for the facing deformation and crest surface settlement, lateral earth pressure, tensile force in the reinforcement layers and acceleration amplification. The vertical ctefOlIDation, horizontal deflection, reinforcement force and earth pressure develop drastically under earthquake loading compared to the end of construction. The results show that these variables are considerably reduced when incorporating the vertical reinforcement in the system. In addition, the findings suggest better performance and higher structural safety for reinforced soil walls, when employing this proposed orthogonally horizontal-vertical geosynthetics

Effects of Dynamic Soil-Structure Interaction on Performance Level of Moment Resisting Buildings Resting on Different Types of Soil

In this study, two structural models comprising five and fifteen storey moment resisting building frames are selected in conjunction with three different soil deposits with shear wave velocity less than 600m/s. The design sections are defined after applying dynamic nonlinear time history analysis based on inelastic design procedure using elastic-perfectly plastic behaviour of structural elements. These frames are modelled and analysed employing Finite Difference approach using FLAC 2D software under two different boundary conditions namely fixed-base (no soil-structure interaction), and considering soil-structure interaction. Fully nonlinear dynamic analyses under the influence of different earthquake records are conducted and the results of inelastic behaviour of the structural models are compared. The results indicate that the inter-storey drifts of the structural models resting on soil types De and Ee (according to the Australian standard) substantially increase when soil-structure interaction is considered for the above mentioned soil types. Performance levels of the structures change from life safe to near collapse when dynamic soil-structure interaction is incorporated. Therefore, the conventional inelastic design procedure excluding SSI is no longer adequate to guarantee the structural safety for the building frames resting on soft soil deposits

Conceptual development and numerical modelling of vegetation induced suction and implications on rail track stabilisation

The effects of tree roots on soil suction and ground settlement are investigated. This paper highlights the inter-related parameters contributing to the development of a conceptual evapo-transpiration and root water uptake equilibrium model that is then incorporated in a comprehensive numerical model. The developed numerical model based on the finite element analysis (ABAQUS) considers fully coupled flow-deformation behaviour of soil. Field measurements obtained by the authors from a field site in western Victoria and from past literature are used to validate the model. The predicted results show acceptable agreement with the field data in spite of the assumptions made for simplifying the effects of soil heterogeneity and anisotropy. The numerical analysis proves that the proposed root water uptake model can reliably predict the region of maximum matric suction away from the tree axis. The paper also compares the natural favourable effect of tree roots with the stabilising mechanisms of geosynthetic vertical drains subjected to vacuum pressure. Although this analogy is only justified for shallow vertical drains, the comparison still emphasises the obvious economical advantages of native vegetation

Seismic behavior of building frames considering dynamic soil-structure interaction

The seismic excitation experienced by structures is a function of the earthquake source, travel path effects, local site effects, and soilstructure interaction (SSI) influences. The result of the first three of these factors is referred to as free-field ground motion. The structural response to free-field motion is influenced by the SSI. In particular, accelerations within structures are affected by the flexibility of the foundation support and variations between the foundation and free-field motions. Consequently, an accurate assessment of inertial forces and displacements in structures can require a rational treatment of SSI effects. In the current study, to depict these effects on the seismic response of moment-resisting building frames, a 10-story moment-resisting building frame resting on a shallow foundation was selected in conjunction with three soil types with shear-wave velocities of less than 600 m/s, representing Soil Classes Ce, De, and Ee according to an existing Australian Standard. The structural sections were designed after applying dynamic nonlinear time-history analysis, based on both the elastic method, and inelastic procedure using the elastic-perfectly plastic behavior of the structural elements. The frame sections were modeled and analyzed using the finite-difference method andthe FLAC 2D software under two different boundary conditions: (1) fixed-base (no SSI) and (2) considering the SSI. Fully nonlinear dynamic analysis under the influence of various earthquake records was conducted and the results of the two different cases for elastic and inelastic behavior of the structuralmodel were extracted, compared, and discussed. The results indicate that the performance level of themodel resting on Soil Class Ce does not change substantially and remains in the life safe level while the performance level of themodel resting on Soil Classes De and Ee substantially increase from the life safe level to near collapse for both elastic and inelastic cases. Thus, considering SSI effects in the elastic and inelastic seismic design of concrete moment-resisting building frames resting on Soil Classes De and Ee is essential. Generally, by decreasing the dynamic properties of the subsoil such as the shear-wave velocity and shear modulus, the base shear ratios decrease while interstory drifts of the moment-resisting building frames increase relatively. In brief, the conventional elastic and inelastic design procedure excluding the SSI is not adequate to guarantee structural safety for moment-resisting building frames resting on Soil Classes De and Ee. © 2013 American Society of Civil Engineers

Numerical and experimental investigations on seismic response of building frames under influence of soil-structure interaction

In this study, an enhanced numerical soil-structure model has been developed which treats the behaviour of soil and structure with equal rigour. The proposed numerical soil-structure model has been verified and validated by performing experimental shaking table tests. To achieve this goal, a series of experimental shaking table tests were performed on the physical fixed based (structure directly fixed on top of the shaking table) and flexible base (considering soil and structure) models under the influence of four scaled earthquake acceleration records and the results were measured. Comparing the experimental results with the numerical analysis predictions, it is noted that the numerical predictions and laboratory measurements are in a good agreement. Thus, the proposed numerical soil-structure model is a valid and qualified method of simulation with sufficient accuracy which can be employed for further numerical soil-structure interaction investigation studies. Based on the predicted and observed values of lateral deflections of fixed base and flexible base models, lateral deflections of the flexible base model have noticeably amplified in comparison to the fixed base model. As a result of the lateral deflection amplifications, it is observed that the performance level of the scaled structural model changed significantly which could be safety threatening

Numerical Analysis of Geosynthetic Reinforced Soil Wall as Bridge Abutment

This paper presents the finite element analysis of a geosynthetic reinforced soil wall as a bridge abutment built in Tehran, and the predictions are compared with the available field measurements. This abutment is analysed using both Limit Equilibrium Method (LEM) for stability analysis and Finite Element Method (FEM) for deformation analysis. Two dimensional plane strain finite element model is adopted for the simulation. Polyvinyl Alcohol (PVA) geogrid with high tensile moduli and low creep characteristics has been adopted in this project to limit the deformation of the bridge abutment. In this model, the backfill soil and geogrids simulated adopting Mohr-Coulomb model, and the elasto-plastic material model that only works in tension, respectively. Bridge abutments can be stabilised by including geosynthetic layers with high tensile moduli satisfying both stability and deformation criteria reducing the construction cost and time, post construction deformations, and future maintenance cost