Search results for: Latest H19-461_V1.0 Exam Questions Vce 🏯 H19-461_V1.0 Labs 🐒 H19-461_V1.0 New Study Plan 🙊 Search for ✔ H19-461_V1.0 ️✔️ on 「 www.pdfvce.com 」 immediately to obtain a free download 🧎H19-461_V1.0 Best Vce
-
Experimental investigations into subballast filtration behaviour under cyclic conditions
In rail track environments the loading system is cyclic unlike the monotonic seepage force that usually occurs in embankment dams. The mechanisms of filtration, interface behaviour and time-dependent changes of the drainage and filtration properties occurring within the filter medium require further research to improve the design guidelines. A novel cyclic process simulation filtration apparatus was designed and commissioned at the University of Wollongong, and a standard testing procedure was established. The test apparatus was designed to simulate heavy haul train operations. Key parameters that influence the change in porosity and pore water pressure within the subballast layer under cyclic conditions in rail track environments were identified.
-
Numerical simulation of soft ground improved with cement
This paper examines, using a numerical model based on the finite element method, the undrained bearing capacity of shallow circular footings on soft ground improved with deep cement mixing. Guidelines are given to identify the importance of the degree of cementation on the bearing capacity of shallow footings. Using a bearing capacity improvement factor, the influence of the degree of cementation and the extent of the cemented region on bearing capacity has been investigated. Finally, the performance of deep cement-mixed columns has been investigated using the numerical model. The results indicate that there exists an optimum length to diameter ratio for the deep mixed cement columns and this optimum ratio depends on the degree of cementation of the soil.
-
A constitutive model of sand with inherent transverse isotropy, considering effects of B values
The objective of this paper is to propose a constitutive model of sand with inherent transverse isotropy taking the effects of b values into consideration, and to verify its validity. In order to apply the proposed constitutive model to initial and boundary value problems, it was implemented in a three–dimensional finite element program code. The proposed constitutive model was developed based on consideration of experimental results and the theory of the multi–surface model. It was verified by comparing the experimental results with the calculations.
-
Recent advances in practical design of rock socketed piles in Victoria
Piles socketed into rock are a common foundation solution to carry large loads from buildings and bridges. They have experienced widespread use in Melbourne for many years and have been installed over a wide range of subsurface conditions. The load applied to the pile is primarily carried by the bottom part of the pile which is “socketed” into the rock. Rock sockets in Melbourne comprise siltstone/sandstone and Newer and Older Volcanics (basalt). Throughout the world, rock socketed piles have been and are still designed by many engineers by assessing estimates of allowable shaft and allowable base resistance, with little if any assessment of the displacement performance of the pile. Settlements are quoted based on experience rather than by calculation. The estimates of allowable shaft and base resistance are usually based on local ordinances, experience or empirical correlations with the uniaxial strength of the intact rock (e.g. see Figure 1).
The performance of most rock socketed piles at serviceability loads is dependent predominantly on the shear resistance developed at the interface between the concrete shaft and the surrounding rock, i.e. shaft resistance. The shaft resistance developed depends on many factors including the shaft diameter, the type, stiffness and strength of the rock and construction effects such as socket roughness, the thickness of smear zone or residual drilling fluid coating the socket walls and the pressure imposed onto the socket rock due to fluid concrete placement (e.g. Johnston, 1977; Williams and Pells, 1981; O’Neill and Hassan, 1994). Shaft resistance is very sensitive to a number of these parameters and as a result, socket performance can vary significantly from one site to another, even in the same rock type. This provides an explanation for the large scatter observed in published correlations between shaft resistance and rock strength; for example Williams, Johnston and Donald (1980) or Rowe and Armitage (1984). The use of such empirical correlations requires the designer to choose a design shaft resistance from within a relatively wide scatter and as a result a conservative assessment is usually made.
-
Soil nailed retention – A practical approach to field verification
In Melbourne, soil nailed retention has been used on a number of major road projects for about 20 years and since that time the walls appear to have performed satisfactorily. During the intervening period to the present, there has been much debate about how the system of soil and embedded nails actually works and world wide a number of design approaches have been developed. These design approaches fall into three main categories:
- bi-linear slip surfaces and a limiting equilibrium analysis method (UK and USA – NailSolver, 1990; SnailWin)
- circular slip surfaces and limiting equilibrium analysis method (Australia – STARES)
- numerical analysis methods (FLAC and PLAXIS)
The nails form passive resistance elements that become stressed as excavation proceeds and the nails strain as there is load redistribution between the soil and the nails. It is now generally accepted that the contribution of the shear (bending) resistance of the nails is minor and most current design methods ignore the nail shear resistance. However, there is much debate about various aspects of design and it is still unclear what distribution of nail forces exists in practice, with various researchers finding a large variation in actual nail forces compared with the forces predicted according to the design methods (FHWA, 1999). The design for head force can be a particularly complicated issue, with the FHWA design method recognizing the contribution arising from both the flexural strength of the wall facing and punching shear modes of failure.
If the nail force distribution is not well predicted by the various design methods it would seem reasonable to adopt a simplified type of analysis in which the nail head force is limited to a nominated value and the wall facing pressures are then determined according to the limiting nail head forces established, providing that near-face failures cannot occur after assessing possible shallow face failure modes. The computer program STARES developed by the University of Sydney is one design approach that allows ready analysis of soil nailed walls using this approach.
A major factor in soil nail analysis is the bond between the nails and the ground and this is one of the most critical aspects of soil nailed retention design because if the bond fails, large volume wall failures can potentially occur. It is therefore important to carefully consider soil-to-nail bond in design and this is one aspect that can be checked by a careful program of field verification and testing. Unfortunately, in many cases the testing and field verification procedures do not relate explicitly to particular soil nail designs and are often derivatives of test specifications for stressed anchor systems. For production soil nails, it is often impossible to carry out testing to the loads required to validate design bond values without nail yield so proof load testing of completed nails may be of little practical use in confirming design bond values.
A carefully designed program of field testing can however be used to verify design bond values and provide confidence in this critical aspect of soil nail performance.
-
Verification of the effects of rolling dynamic compaction using a continuous surface wave system
Impact rolling or rolling dynamic compaction (RDC) has been used to redevelop the site of an old waste tip. The fundamental principle of RDC is a non-circular drum rotating about one corner and falling to impact the ground, while being towed at 10-12 km/h. Surface wave measurements show that the RDC has been effective in improving the strength of the material below ground surface. The successful application of the RDC resulted in a cost-effective and environmentally sustainable solution.
-
Rock mass strength derived from rock mass characterization
The assessment of rock mass strength is a key element for the analysis of many rock excavations, both open pit and underground. There have been attempts to assess this strength using a suitable rock mass strength criterion having input derived using a Rock Mass Classification system. The most well developed criterion is the Hoek-Brown Failure Criteria using the Geotechnical Strength Index (Hoek, 2002) as input. Despite its popularity the GSI has some inconsistencies. Rock masses with differing fracture frequencies and joint conditions can have the same GSI value and therefore the same strength characteristics would be applied. To address this issue, this paper describes a method to determine the input to the criterion on the basis of the joint condition and fracturing of the rock mass.
-
State dependent dilatancy relationship for sands
The stress dilatancy relation which accounts for the dependencies on stress level and density is proposed. The consideration of these aspects would give a significant implication on the modelling of granular materials behaviour since it is mostly dominated by the evolution of dilatancy and density history. Modified Cam clay dilatancy is modified through state index parameter Is proposed by Verdugo (1992) which measures the ratio between the deviation of the current void ratio and its relative critical void ratio to a reference one. The proposed stress dilatancy relation is compared to the experimental result from undrained triaxial test for wide range density and stress level. It also indeed exhibits a special case of general anisotropic dissipation function introduced by Dafalias (1986).
-
Energy driven piles in Australia: Design and construction lessons from a trial at Fishermans Bend
About 50% of the energy bill of buildings arises from space heating and cooling (air conditioning). The associated greenhouse gas (GHG) emissions of the sector account for between 14% and 25% (or higher, particularly overseas) of the total emissions. Geotechnical engineering designers and contractors have an opportunity to contribute to a more sustainable future. Shallow geothermal technology for efficient heating and cooling represents one such opportunity. Through a partnership between Wagstaff Pilling and The University of Melbourne, the design and construction of the first energy driven piles in Australia was undertaken in 2019, with the last field thermal performance testing completed in January 2020. These energy piles can be connected to a geothermal system.
This paper discusses the construction and installation of this small-scale field trial at Fishermans Bend (Victoria), comprising three different energy driven pile configurations. An investigation into the thermo-mechanical efficiency of driven energy piles to evaluate their capacity to provide heating and cooling for buildings is undertaken. Peer-reviewed literature already exists discussing shallow geothermal energy systems and bored energy piles. However, there is a significant gap in the literature considering driven energy piles specifically, and no public guidance about construction; thus, we aim to start redressing these issues herein. Experimental data collected by running Thermal Response Tests (TRTs) on selected energy driven piles at Fishermans Bend are presented. The information collected from the fieldwork will be used to validate detailed Finite Element Method (FEM) models and to optimise construction, minimising costs and to demonstrate none or minimal program delays.
-
Experience of Overcoring the ANZI Strain Cell in HQ Exploration Boreholes to Determine the Three Dimensional In Situ Stresses A Depths Approaching 1KM
This paper describes recent use of the ANZI (Australia, New Zealand Inflatable) strain cell and the overcoring method of stress relief in an HQ exploration borehole at depths approaching 1km to determine the three dimensional in situ stress field in a one-day operation. The stages of a routine overcoring operation are presented to illustrate each step of the process. The results from a European metalliferous mining site are presented to illustrate the process of characterising the three dimensional in situ stress environment when multiple high confidence measurements are achieved.
The ANZI strain cell is an instrument system that uses the overcoring method of stress relief to determine the three dimensional in situ stresses in rock. The instrument has been used successfully for over three decades in numerous underground mining and civil projects but technical advances over the last decade have allowed the system to be deployed routinely in surface exploration boreholes. Recent development of a downhole electronic data logger, a wireline enabled drilling system and an instrument deployment system has simplified the process of obtaining three dimensional overcore measurements at previously inaccessible depths remote to any underground excavation.
The capability to deploy ANZI strain cells from surface exploration boreholes represents a significant breakthrough for the design of underground civil structures. High confidence characterisation of the in situ stresses at design stage provides the opportunity to design key infrastructure to take advantage of the in situ stress field from the outset before any excavation and construction activity even begins. Understanding the three dimensional in situ stress field not only provides a measure of the magnitude and direction of loads acting within the rock mass, it is also provided insight into the mechanics of the all the various processes driving ground deformations.