Search results

Robotic industrial applications are very well established in the manufacturing industry, while they are relatively in their infancy phase in the construction sector. The need for automation in construction is clear especially in repetitive tasks. The excavation process, which is generally critical in most construction projects, is a prime example of such tasks. This paper addresses automation assistance in excavation. The work utilized the robotics approach towards the automation of a typical excavator model, whose structure closely resembled that of an industrial manipulator. A simulation package using Matlab was developed using several embedded design and analysis tools. Emulation was also carried out on the RHINO educational robot to confirm the simulation results. The constructed simulation package offered an integrated environment for trajectory design and analysis for an excavator while addressing the constraints related to the excavator structure, safety and stability, and mode of application.

This paper aims to present the framework for a model that can be used to estimate the production rate, activity duration, total fuel use, and total pollutants emissions from earthwork activities. A case study and sensitivity analysis for an excavator performing excavations are presented.

The tool is developed by combining the multiple linear regressions (MLR) approach for modeling the productivity with the EPA's NONROAD model. The excavator data were selected to build the productivity model, and emission factors of all type of pollutants from NONROAD model were used to estimate the total fuel use and emissions.

Results indicate that the excavator productivity model had high precision and accuracy, low bias, with trench depth and bucket size are in the model, it can explain 92 per cent variability of productivity rate data, and can be used as the basis for estimating the fuel quantities that will be required and the total expected pollutant emissions for the project.

The estimating tool proposed in this paper will be an effective means for assessing the fuel consumptions and air emissions of earthwork activities and will allow equipment owners or fleet managers, policy makers, and project stakeholders to evaluate their construction projects. The tool will help the contractors to estimate the fuel quantities and pollutant emissions, which would be valuable information for a preliminary environmental assessment of the project.

Although there are already methods and models for estimating productivity rate and emissions for heavy duty diesel (HDD) construction equipment, there currently is not a means for doing all of these at once.

Construction plant and equipment harbour significant health and safety hazards. One particular item, the mini‐excavator, presents a hazard from its inherent instability and tendency to overturn during use. The purpose of this paper is to investigate turnover incidents to observe prominent factors and contribute to development of best practice guidance for improving health and safety relating to mini‐excavator use.

Comprehensive documentary data from eight case study incidents, along with anecdotal data from a further three, were qualitatively analysed in terms of: machine weight, machine activity, ground type/topography, operator competence, type of overturn, damage to property, and injury to person(s). Results were presented to experts in the field for comment and conclusions/recommendations accordingly developed.

Observed prominent casual factors include: inadequate assessment of risk and non‐adherence to safe working practice, working on poor ground, and working on inclined surfaces. The use of sealed operator cabs and proprietary seat restraint mechanisms seem to mitigate risk of personal injury to operators during overturn incidents. A need for cyclic training to reiterate good operator and banksman practice is emphasised, while construction managers should also be aware of the risks, and help implement risk controls.

Findings will inform construction plant management research generally, and the subject of mechanised workplace transport stability specifically.

Best practice protocol will inform health and safety management of mini‐excavators at the workplace.

Academic research into mini‐excavator stability is embryonic; this paper furthers evolving knowledge in the field.

The extensive use of mini‐excavators in construction presents a significant health and safety risk from their tendency to become unstable, or in the extreme to roll‐over, under certain working conditions. No standard exists to specifically assess excavator stability, so the purpose of this paper is to document the development and trial of a series of practical field tests designed to achieve this.

Tests were designed in collaboration with a group of plant experts and competent operators. The tests were subsequently trialled by applying them to four mini‐excavators, the aim being to see if these plant items could be reliably assessed in terms of their stability characteristics. Results of the study were presented to H&S experts for comment.

The tests were able to assess mini‐excavator stability. For each machine, five “stability criteria” were scored thereby producing an overall score, by which mini‐excavator stability could be conveniently represented.

No previous field test research has been identified in this area. The results produced here may go some way towards developing an international standard for on‐site stability tests.

The tests are easy to apply at the work site so long as performed by competent persons under appropriately risk‐assessed and risk controlled conditions; and if disseminated to industry, could act as a means of standardising mini‐excavator stability tests until such time an International Standard becomes available.

Research in this area is entirely novel.

Tracked hydraulic excavators are versatile and ubiquitous items of off-highway plant and machinery that are utilised throughout the construction industry. Each year, a significant number of excavators overturn whilst conducting a lifting operation, causing damage to property, personnel injury or even fatality. The reasons for the overturn are myriad, including: operational or environmental conditions; machine operator acts or omissions; and/or inadequate site supervision. Furthermore, the safe working load (SWL) figure obtained from manufacturer guidance and utilised in lift plans is based upon undertaking a static load only. The purpose of this paper is to determine whether the SWL is still safe to be used in a lift plan when slewing a freely suspended (dynamic) load, and, if not, whether this may be a further contributory factor to overturn incidents.

Previous research has developed a number of machine stability test regimes but these were largely subjective, impractical to replicate and failed to accurately measure the “dynamic” horizontal centrifugal force resulting from slewing the load. This research contributes towards resolving the stability problem by critically evaluating existing governing standards and legislation, investigating case studies of excavator overturn and simulating the dynamic effects of an excavator when slewing a freely suspended load at high rotations per minute (rpm). To achieve this, both the static load and horizontal centrifugal force from slewing this load were calculated for six randomly selected cases of an excavator, with different arm geometry configurations.

The results from the six cases are presented and a worked example of one is detailed to demonstrate how the results were derived. The findings reveal that the SWL quoted on an excavator’s lift rating chart considerably underestimates the extra forces experienced by the machine when an additional dynamic load is added to the static load whilst lifting and slewing a freely suspended load.

This work presents the first attempt to accurately model excavator stability by taking consideration of the dynamic forces caused by slewing a freely suspended load and will lead to changes in the way that industry develops and manages lift plans. Future research proposes to vary the weight of load, arm geometry and rpm to predict machine stability characteristics under various operational conditions, and exploit these modelling data to populate pre-programmed sensor-based technology to monitor stability in real time and automatically restrict lift mode operations.

Excavator productivity calculations embrace myriad variables, which in turn, can be modelled in several ways. A key productivity variable is operator competence (O _c ) because this can impact on so many of the other variables. Earlier research has studied excavator productivity, but little has attempted to simultaneously model productivity variables in relation to O _c . The purpose of this paper is to address the void in extant literature.

A numeric, theoretical analysis is undertaken using the Caterpillar® hydraulic excavator productivity model to estimate excavator production, given: first, variance in modifying factors based on derived maximum and minimum values; and second, variance resulting from linear calculations based on excavator operator competence.

Excavator productivity resulting from incremental variance of modifying factors in isolation is shown to be linear except, in the case of bucket payload. Simultaneous application of modifying variables results in a greater, curvilinear productivity trend; while it is demonstrated that quantification of key modifying factors can to a significant extent be related to operator competence.

Findings add to productivity literature generally and to that of plant and equipment more specifically. Results will help productivity estimation of excavation in a practical sense while informing subsequent design of an empirical academic research of this problem.

Originality relates principally to determining modifying factor ranges and their analysis of simultaneous effect on each other, especially, as influenced on assumptions of operator competence.

The paper analyses the nature and causes of fatal incidents involving excavators occurring in the Australian construction industry. A three-level incident causation model developed by researchers at Loughborough University forms the theoretical framework for this analysis, which seeks to identify immediate circumstances, shaping factors and originating influences in selected incidents.

Case study incidents were identified from the National Coronial Information System database. These incidents were subjected to content analysis to identify causal factors.

Ten cases were analysed in total. In all of these cases immediate circumstances could be identified. These included the use of unsafe work methods and the condition, suitability or useability of plant. In several cases shaping factors, such as communication between work-team members and the design of work processes, were identified as likely contributors to the incidents. In none of the cases could originating influences be identified.

The research was limited by the relatively small number of cases for which detailed investigation reports were available and the fact that, for the most part, the reports focused on the immediate circumstances surrounding the incidents.

The circumstances of the fatal incidents in Australia are similar to those reported in the UK and the USA and the identified causes have known safety solutions. The persistence of these incidents in the Australian construction industry suggests that there may be underlying reasons why known safety solutions are not implemented. Further in-depth analysis of incident causes may help to identify organisational and/or cultural causes of incidents involving excavators.

The analysis provides a more detailed qualitative analysis of the causes of fatal incidents involving excavators than would is possible using national compensation data, which restricts analysis to a classification of the mechanism and agency of injury.

This paper aims to develop a quantitative model for predicting the productivity of excavators using artificial neural networks (ANN), which is then compared with the multiple regression model developed by Edwards & Holt (2000). A neural network using the architecture of multilayer feedforward (MLFF) is used to model the productivity of excavators. Finally, the modelling methods, predictive behaviours and the advantages of each model are discussed. The results show that the ANN model is suitable for mapping the non‐linear relationship between excavation activities and the performance of excavators. It concludes that the ANN model is an ideal alternative for estimating the productivity of excavators.

The dispatching of trucks in earthmoving and like operations is worthy of examination because of potential emission reductions and savings through the appropriate allocation of trucks to excavators and dump sites. The paper aims to discuss this issue.

Truck dispatching is performed through linear programming (LP) and the effect of truck allocation on unit emissions and unit costs established. Number of trucks, unit cost and unit emissions are all considered as objective functions. A cut and fill operation on a road project provides a numerical case study.

It is demonstrated analytically that the minimum unit emissions solution is the same as that for minimum unit cost. Numerical results from the case study, including sensitivity analyses on the underlying parameters, support this conclusion.

The LP dispatching solution, based on minimizing truck numbers and unit costs, accordingly impacts the environment the least in terms of emissions. The paper's results will be of interest to those designing and managing earthmoving and like operations for production, cost and emissions.

While LP has been used by others to examine optimum unit cost dispatching, this paper is original in examining the dispatching or truck allocation based on both unit cost and unit emissions, and showing the relationship between the optima for both.

The purpose of this paper is to explore the wear phenomena on the bottom surface of an excavator bucket and optimize the design parameters to reduce wear rate by converting sliding motion to rolling motion of rock during the time of operation.

A test rig has been developed to study the wear phenomena and type of wear on the excavator bucket. Three different bottom plates have been fabricated for experiments to observe the difference of severity of wear in terms of volume of material removal.

It has been observed that the bottom plate having the mesh-type wear bar pattern was comparatively more resistive to wear than the other two models. Wear-affected zone on the bottom plate was also detected and represented with the help of colour contour.

It is expected that these findings will contribute towards the development of the bottom plate of the excavator bucket with some new pattern of a wear bar, which will be efficient to reduce the phenomena on its surface.

The excavator is one of the important equipment in coal mining. A proper design of the excavator bucket will reduce the wear, as well as the running cost of equipment, and increase the rate of production.