Quantification of cavity excavation produced strong empirical support for the ecological constraints model for the evolution of delayed dispersal in the cooperatively breeding red-cockaded woodpecker. The long times required for cavity excavation select for competition over breeding vacancies in established territories and against excavation of cavities in unoccupied habitat. Duration of excavation varies between woodpecker populations, but may require over 13 years in longleaf pine and over 10 years in loblolly pine. Duration of excavation is extremely variable. Much of the variation is due to variation in effort by excavating woodpeckers, which is in turn partially related to the need for new cavities in relation to the number of available cavities on a territory. An average of only 11 % of an individual's time budget is devoted to excavation, and only one individual per group makes significant contributions to excavation. Once completed, cavities are used for periods that may exceed fifteen years. Cavities in longleaf pine are used for significantly longer periods than cavities in loblolly. Whereas cavities no longer used as nests are abandoned altogether in loblolly, they are still roosted in for many years in longleaf. Final abandonment of longleaf cavities appears to be related to cavity loss. Quantification of cavity turnover revealed that three of the study populations were stable in cavity numbers over the study period, while a fourth underwent alarming declines. The continued use of restrictors and artificial cavities, and the protection of old-growth upon which the woodpeckers depend for excavation, are recommended. / Master of Science

published_or_final_version / Applied Geosciences / Master / Master of Science

Currently McConnell Dowell Constructors Ltd. is involved in the horizontal rebuild of Christchurch as part of the SCIRT alliance. Part of installing new infrastructure is that work is commenced around existing and live services. During installation, live services are occasionally struck which have the potential to cause injury and/or death along with subsequent economic costs of having to repair the damaged services. David Hopper and Shane Soulsby have investigated some of the root causes for service strikes to occur with a distinct focus on process, communication, culture and costs. From that, key findings have been established along with recommendations and an implementation plan in an effort to lower the number of service strikes on projects.

P.ORTEGA-VERDUGO1 S.GUZMAN-AMSTRONG1 D. COBB1, D.V.DAWSON1, J.KOLKER1, M.HERNANDEZ1, J.WARREN 1University of Iowa, Iowa City, USA. NA

Texte remanié de: Doct. diss.--Sydney, 1999. / Bibliogr. p. 320-326.

Acoustic emissions (AEs) are generated as a result of the creation of, or movement on microcracks in a rock mass. Hypocentres of AEs have been used as a very effective method of visualising the extent (amount and location) of microcrack damage. Studies have used AE locations to investigate both the behaviour of rock failure in laboratory experiments, and to evaluate damage in the Excavation Disturbed Zone (EDZ) around underground openings. The latter has particular significance for the safe storage of nuclear materials in deep underground facilities. Because AEs represent phenomena associated directly with the physical processes occurring in microcracking, then they can also be used to evaluate the fundamental mechanics of the failure. In this thesis a moment tensor (MT) inversion procedure is developed for AEs. This utilises full-waveform records from an array of ultrasonic piezoelectric transducers distributed around the rock mass. The procedure is tested using synthetic amplitudes and is shown to be robust even with high amplitude uncertainties. The inversion is particularly good at resolving the volumetric component in the source. The procedure allows a precise and well-constrained analysis of the forces that are creating the AEs, and, in some cases, that are actually creating the damage. The mechanics can then be related to the stress field in the rock mass, or can be compared to results from dynamic micromechanical models. Three case studies are performed. Two of these investigate the fundamental behaviour of microcracking in the laboratory. A series of laboratory tests are conducted using polyaxial stress to study the mechanics of damage under realistic in situ stress paths. The third case study investigates the mechanics of failure operating in the EDZ. AEs are shown to be truly scaled earthquakes although with often-complex non-double-couple mechanisms.

Stability of underground excavations is a prerequisite for the proper functioning of all other systems in a mining environment. From a safety point of view, the lives of people working underground rely on how well the support systems installed underground are performing. The ground control engineer cannot design an effective support system unless the area of the rock mass around the opening, prone to failure, is well identified in advance, even before the excavation of the tunnel. Under high stress conditions, usually experienced at deep mining levels, stress-induced rock failure is the most common type of instability around the underground openings. This thesis focuses firstly on the use of the finite difference numerical tool FLAC to simulate brittle rock failure under static in-situ stresses. Brittle failure of the rock mass around underground openings is a particular type of stress-induced failure, which can result in notch-shaped breakouts around the boundary of the tunnel. Generation of these breakout zones is a discontinuum process and approximating this process using FLAC, which is a continuum tool, requires careful consideration of the stress conditions and the stress related behavior of rock material. Based on plasticity theory, this thesis makes an effort to estimate the breakout formation using an elastic – brittle - plastic material model. Due to seismic challenges that deep mining operations are currently experiencing, rockbursting is a major hazard to the stability of underground structures. Therefore in this research, brittle failure of rock in the vicinity of the underground excavations is approximated also under dynamic loading conditions. The numerically modeled results of two different material models iv are compared with each other along with a previously developed empirical graph. This assessment, when further validated by field observations, may provide a different perspective for underground support design under burst-prone conditions.

No description available.

Increased interestin In-Situ Resource Utilization (ISRU) concept for lunar outpost construction has motivated to the development of autonomous excavation rovers. The system design of two autonomous excavation rover prototypes UNEMEEP and The Musketeers are detailed in this thesis. The problem of autonomous excavation has been explored in the area of agriculture and mining. However, to date very little have been accomplished in the area of an autonomous excavation rover aimed towards space application. A hybrid position and admittance control strategy is implemented on autonomous excavation rovers to achieve digging and leveling capabilities. Integration tests and a full scale multirover mission scenario were also carried out. The results from the experiments are analyzed and recommendations are made to improve upon the capabilities of the rovers.

Increased interestin In-Situ Resource Utilization (ISRU) concept for lunar outpost construction has motivated to the development of autonomous excavation rovers. The system design of two autonomous excavation rover prototypes UNEMEEP and The Musketeers are detailed in this thesis. The problem of autonomous excavation has been explored in the area of agriculture and mining. However, to date very little have been accomplished in the area of an autonomous excavation rover aimed towards space application. A hybrid position and admittance control strategy is implemented on autonomous excavation rovers to achieve digging and leveling capabilities. Integration tests and a full scale multirover mission scenario were also carried out. The results from the experiments are analyzed and recommendations are made to improve upon the capabilities of the rovers.