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
-
Geotechnical mapping using a geophysical method of investigation
Site characterization procedures have hitherto overlooked areal mapping of sub-surface geotechnical properties of soil/rock and have instead emphasized conventional “point” testing processes to find and document these properties. On the other hand, the fast pace of construction and advancements in geophysical methods have led to the possibility of developing matching site characterization methods and geotechnical mapping is considered here as the way forward. In many countries around the globe, it is now argued that current lack of geotechnical maps, which could be used as support for planning in new areas, is one of the reasons for the development of areas with less favourable geotechnical conditions. Furthermore, contemporary developments in geotechnical engineering clearly exhibit an agreement with geotechnical mapping, seen as a helpful tool in rapid assessment of sub-soil conditions and hence suitability or otherwise of a particular site for a construction project. Current research is about geotechnical mapping of subsurface soil properties of a selected area in the vicinity of Islamabad with the help of the electrical resistivity method. The research is believed to be the first of its kind on a comparatively new subject.
-
On best practices for trackbed design
This paper reviews the best practices of trackbed design for railway projects. Various existing methods have been studied and recommendations for more economical design are provided. The analytical/empirical methods from various standards such as UIC, AREMA, British Rail, and Australian standards, as well as other commonly used methods such as Raymond and Li-Selig are compared based on a typical track embankment cross section. The outcome was then evaluated against 2D and 3D numerical models. Incorporating numerical methods is shown to render considerable reductions in the required prepared subgrade/structural fill materials and allow for assessment of long-term design issues, such as subgrade shear failure due to excessive plastic deformations.
-
Hydraulic calculation of clay-based backfill and plug for the intersections of tunnels in the geological repository for high-level radioactive waste
A geological repository for vitrified high-level radioactive waste (HLW) has a range of different types of tunnels with different geometries depending on function: transport and emplacement of engineered barrier materials and waste packages, or access to underground facilities etc. At points where tunnels intersect, a complex arrangement of closure components will be placed to ensure long-term isolation performance of a disposal system. It is a key issue to identify requirements for the design of the materials and layout of these components, including clay-based backfill and plug. In this study, three-dimensional simulations of groundwater flow are conducted to investigate the sealing performance of clay-based backfill and plug at the tunnel intersection for given hydraulic conditions around the tunnels. In the analytical results, it is found that the direction of hydraulic gradient, hydraulic conductivities of concrete and backfilling materials and the position of clay plug had impact on flow condition around the engineered barrier system (EBS).
-
Assessment Of Existing Foundations For Building Upgrade Projects
Building owners are often faced with the question of whether to demolish and rebuild to gain extra floor space, or to assess if existing buildings can support additional levels. Aside from the adequacy of the superstructure, consideration must be given to the capacity of the existing foundation system to cater for the increased loading. Douglas Partners (DP) has employed a range of portable equipment for use in often congested basements and poor access areas, to investigate and develop a geotechnical model for such sites.
Where no records exist, or where the assessment of the existing pile foundation is required for QA purposes, low-strain pile testing techniques may be used to determine pile lengths. The geotechnical model and existing foundation details are subsequently combined to assess the capacity and expected settlement performance of the existing foundation system. In most cases, increased confidence in parameters and advances in foundation analysis and design methods has permitted extra floors to be added, thus realising a large capital benefit for the owner of the building.
-
Excavations and the Next Door Neighbour
I have recently seen an increasing number of geotechnical reports that imply that using Ko=1-sinφ’ (the coefficient of earth pressure at rest) to design basement retaining walls is appropriate and will, to a large extent, prevent movement of neighbouring properties. Can this be justified?
Ko, as we all know, is the ratio of the horizontal to the vertical stress in the ground. Although it is generally accepted that Ko = 1 -sinφ’ applies to normally consolidated soils (Bishop 1958), it is a function of stress history. Since most Australian soils are the product of complex weathering and desiccation processes, they are generally over-consolidated and it is probably wrong, more often than not, to assume Ko=1-sinφ’.
Alternatives are available and guidance can be found in papers such as Mayne and Kulhawy (1982), from which the expression Ko =(1 – sinφ’).OCRsinφ’ might be chosen as a more rational alternative. This could present problems if, as is so often the case, testing has been omitted to save money and neither φ’, nor OCR, are known. In this case it might be better to guess a plausible, but conservative, value of Ko based on experience and a knowledge of the local geology. In most cases a “conservative” value of Ko is a high one, but the specific application needs to be considered and a high, or low, value chosen as appropriate. Ko=1 may not be unreasonable, at least as a starting point, in many situations.
It is simple enough to design a retaining wall to withstand Ko stresses, but this does not mean they will eventuate, or that the resulting wall will prevent ground movement. If the objective is to try and minimise movement then analysis of the entire construction sequence is required, using realistic values of the basic parameters. It may be worth keeping the following thoughts in mind:
- Ko stresses will only be maintained if zero ground movement occurs. Even with diaphragm walls and very stiff, top down, construction this is hard to achieve in practice, so actual stresses are nearly always less than the Ko ones.
- Relatively small movements of a wall during excavation and anchor installation are enough to cause stresses to drop to the active (Ka) value. This can be demonstrated using WALLAP, FREW, or a finite element/difference program to model the construction sequence.
- Walls are often allowed to cantilever as much as they can before the first row of anchors is installed. This causes movement that is usually close to the maximum that the wall will experience on completion and the stresses drop to the active value.
- Stressing anchors to high levels, once a wall has been allowed to deflect, increases stresses in the wall, but does little to redress ground movements that have already occurred.
- In practice, ground movements are more likely to be limited by undrained conditions during excavation, than by anything that the engineer can do to stiffen the restraint. Whether this can be relied on in a particular instance to limit ground movements needs careful evaluation.
- Where a basement is built in open cut, ground movements will have occurred during excavation and cannot be reversed. In this case earth pressures on the wall are more likely to be governed by the level of compaction given to the backfill, as suggested by Ingold (1979), than by the original Ko condition.
To me this illustrates that design, of even a commonplace construction element such as a basement wall, requires very careful consideration and my concern is that there is a modern tendency to ignore the complexities. This may be due to a lack of time, a lack of money, or even to a lack of interest in the subject, as Tim Sullivan’s recent discussion of post- graduate study might suggest (Australian Geomechanics, December 2003). Whatever the cause, geotechnical engineers are paid to give advice that is reasonable and appropriate in relation to every one of their projects. This requires site specific data and site specific thought. Relying on “off the shelf” reports with little or no data can have dire consequences and the excuse that it was only a “cheap” investigation holds no water when things go wrong. I urge any of you who provide geotechnical design advice to keep your thinking cap on at all times – to lose it is to court disaster!
-
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.
-
Understanding Liquefaction Triggering Risk – An Australian Geotechnical Design Perspective
Resilience is the ability to quickly recover during an adverse event. Following an earthquake the resilience of a community can be directly related to working infrastructure. Geotechnical resilience design must consider liquefaction from future large earthquakes.
Although Australia is considered a stable continental region with relatively low seismic hazard, earthquakes do occur and where susceptible geological conditions exist, liquefaction can occur. In fact, liquefaction has been documented in Australia on at least three occasions. In 1897, liquefaction was observed during a large (Ms 6.5) earthquake near Beachport, south-eastern South Australia (Collins et al., 2004); in the 1903 Warrnambool, Victoria (Ml 5.3) earthquake (Mitchell and Moore, 2007); and in 1968, numerous “sand blows” were observed following the Ms 6.8 earthquake at Meckering in Western Australia (Collins et al., 2004).
Liquefaction is a credible geohazard considered in current Australian geotechnical engineering practice, and infrastructure planning desk studies in Australia commonly identify liquefaction as a geohazard where susceptible soils exist within the project footprint. Further assessments are required in subsequent feasibility and detailed design phases. Accurately assessing the liquefaction triggering potential is an essential part of geotechnical design considerations.
The low seismicity of Australia creates a situation where liquefaction triggering is marginal at design hazard levels. This low level of seismic hazard makes the liquefaction trigger assessment very sensitive to the derivation of the seismic inputs. The lack of guidance on liquefaction from AS1170.4 requires interpretation of the basis seismic hazard inputs.
This paper explored the sensitivity to seismic inputs in low seismicity hazard Australia, to better understand liquefaction triggering risk in Australian geotechnical design. The components of the seismic hazard inputs are reviewed. A case study is presented showing that for liquefaction assessments in low seismicity regions, liquefaction triggering is sensitive to the selection of design magnitude and the calculation of the ground motions through the soil profile.
-
Highly flexible catch fences and high performance drape mesh systems for rockfall protection in open pit operations
Rockfall hazards in open pit applications mainly occur in steep open pit walls due to aggressive pit design, in flat walls without berms while following shallow dipping ore bodies or locally on batter level. Areas with high damage potential such as decline portals or haulage ramps are especially hazardous. Dangers from falling rocks have to be reduced as much as possible. The protection systems to cope with such hazards from the manufacturer Geobrugg which are described in this paper are highly flexible and consist of high-tensile steel components. They are field tested and are thus rated with a certain energy absorption capacity. In order to get impact velocities and energies, a rockfall simulation is run, utilising actual slope characteristics. This study deals with three case studies of rockfall protection systems recently implemented in Western Australia. The first study describes a portal protection fence, the second one a ramp protection fence and the third one a high-performance drape system with impact section.
-
Reliability-based geotechnical design in an Australian context
The design philosophy adopted by the international geo-engineering community over the last few decades has largely evolved from working stress design (WSD), in which a single or lumped factor of safety (FoS) is adopted, to a load and resistance factor design (LRFD) approach. In LRFD, partial factors are applied to actions (i.e. loads), soil parameters and / or resistances. These partial factors vary in magnitude depending on the relative uncertainty of each parameter to which they are applied. The approach adopted in Australia has differed, with both WSD and LRFD approaches being widely used. In the authors’ experience, there is limited awareness in the Australian geo-engineering community of the relationship between the concept of reliability and the partial factors adopted in LRFD, and therefore of the potential benefits of undertaking reliability-based design (RBD). The outcome of this is that RBD, in which the uncertainty of the variables which may affect the design is individually assessed, is rarely undertaken. This paper discusses the concept of RBD and its place within the framework of Australian Standards and presents practical means of adopting RBD with accompanying examples from the literature. The intention of the paper is to encourage practitioners to consider uncertainty in geotechnical design more rigorously, whilst acknowledging the importance of maintaining engineering judgement in design.