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Abstract A small opencast coal mine has been developed over previous underground workings in the Malvern Hills, inland Canterbury, New Zealand. The coal measure strata dip at ~45° to the southeast, and consist of finely laminated mudrocks with multiple coal seams of varying thickness. Production is in the range 10,000 to 15,000 tonnes per annum from two principal seams with an aggregate thickness of ~4.5m. The open pit has been designed with footwall batters parallel to bedding, vertical bench separation of 15m, and the highwall formed to a nominal 4V:1H. Preliminary examination of the open pit mine site in 2003 indicated that footwall failures involved de-lamination due to drying out on exposure, and buckling and/or shearing along bedding surfaces. During mine development it became apparent that the batters formed easily where thin (less than 0.3m thick) coal seams were present in the sequence. In the 2004 campaign the pit floor was lowered, with a new batter and bench formed to expose the 3m thick Main Seam coal. The day after completion of this batter, a large buckle failure occurred involving the entire length of the pit (85m along strike), and a 2m thick intact slab with a total volume of ~3700m³ translated down dip 6.2m on the base of a thin coal seam to form a pronounced buckle at the toe. Even though footwall batters are cut to the angle of dip, which is entirely realistic geotechnically, the de-coupling and buckling that occurred compromised the safety and economics of the whole operation. Buckling failure in moderately dipping soft rock sequences has been identified in footwall slopes of coal mining operations. Models used in the literature to simulate similar footwall failures include: the Euler solution using column and beam buckling theory to calculate the kinematic feasibility of a slab-buckle, conceptual modelling using a base friction table, and numerical modelling using distinct element analysis. Back analysis of the Malvern Hills failure was necessary to investigate the controls on the footwall stability, and for future mine design. Engineering geological description of the pit and slab materials was done, and an engineering geological model created. Samples of the slab material and failure surface were collected by coring and trenching, with testing of these materials to establish the required parameters for use in the Euler solution. Back analysis using three different forms of the Euler solution provided unrealistic results that overestimated the overall length of a stable slope by more than 10 times. An engineering geology reassessment was undertaken, and a number of inadequacies in the Euler solution methodology were identified particularly in relation to pore pressure and elasticity considerations. Given that the Malvern Hills toe-buckle slab failure displays both elastic and plastic deformation components in the soft mudrocks, and the slab itself cannot be considered as homogenous, reservations must exist about conventional predictive analytical techniques for pit slope failures of this type. No further large scale slab-buckle failures have developed at the mine site, in part because of the slow rate of coal extraction, but precautionary drainage of the footwall slopes has been undertaken to improve overall batter stability. The location of the slab-buckle failure on a critically positioned pre-sheared thin coal seam with full hydrostatic head is considered the most probable cause, rather than inherent instability of the generic bench and batter arrangement adopted. The adoption of a precedent based engineering geology approach to future mine design is considered the most appropriate solution in the circumstances.

The Haast Pass highway has had a long history of instability since it was constructed in 1960. Steep slopes and deeply incised river create an actively changing geomorphic environment making maintaining the highway corridor hazardous and difficult. This thesis study provides the first comprehensive investigation of the highway corridor between the Summit and Thunder Creek Falls using LiDAR and detailed air-photo analysis to provide the basis for geomorphic mapping. Management of slope hazards to date has been based on a reactive approach treating the immediate unstable areas around landslides after they occur. This study presents the first large-scale geomorphological assessment of the highway corridor identifying surface unit type, slope processes and slope hazards in order to facilitate the development of a long-term highway management strategy. Because dense vegetation covers nearly all the slopes above the highway in the study area as as such, it has not been possible to adequately investigate slope geomorphology until the availability of LiDAR. This study is the first to use Light direction and ranging[LiDAR] for corridor hazard mapping beneath dense vegetation in New Zealand. The LiDAR survey was flown by New Zealand Aerial Mapping in January 2014 for the New Zealand Transport Agency and was provided for use in this study. The LiDAR surface model created serves as the basis for mapping surface units and landslide features, enabling the identification of slope processes and landslide hazards. Aerial photos were also used to identify surface unit type and slope processes where vegetation was absent and enabled the activity of slopes to be evaluated. Interpretations made using LiDAR were validated using aerial photography and targeted ground truthing with all ground truthing sites confirming the interpretations made. Large scale geomorphology mapping was undertaken on slopes above the highway on the western side of the valley and showed that there were distinct differences between the southern and northern parts of the highway corridor. Between The Haast Pass Summit and Pipson Creek the slopes are dominated by schist bedrock with regolith confined to small deposits next to the highway and larger deposits in tributary valleys. The slope hazards affecting the highway in this zone are confined to debris sliding and rockfall from regolith deposits and bedrock cliffs next to the highway between Robinson and Pipson Creeks. The slopes between Pipson Creek and the Gates of Haast, in contrast, consist of deep regolith deposits and regolith veneered slopes. Evidence of active and recently active slope processes on the slopes facing the highway confirm the instability is associated with slope hazards including debris flows, debris slides, rock fall and highway collapse. Small-scale detailed evaluations were undertaken at Diana Falls, Ford Creek, The Hinge and the Gates of Haast with the sites selected based on their history of instability and/or their particu- larly hazardous appearance during the large-scale geomorphology and hazard identification. Using the LiDAR surface model surface units and landslide features were identified and mapped with small-scale engineering geomorphology maps. This information was then used to interpret the subsurface geometry and the failure mode/slope processes acting on the slope enabling an assessment of the current stability and future slope development to be made. Diana Falls was found to have scarps and tension cracks running across the regolith covered slope indicating that future landslides from this site will be an ongoing problem. At Ford Creek the landslide was identified as a rock compound slide, but assessments of its current stability and future development were unable to be made. Detailed investigations at The Hinge revealed evidence of a large creeping debris slide and the existence smaller debris slides below the highway through the entire investigation area; the debris slides identified show signs of activity and continued debris sliding will continue to affect the highway in the future. The investigation of the Gates of Haast revealed that the slope instability is not as extensive as it has been in the past, however, recent rock slides and debris flows have continued affect the highway and will continue to pose a hazard in the future. This thesis provides fundamental information required to develop a comprehensive management plan for the Haast Pass highway corridor between the Haast Pass summit and the Gates of Haast. A new landslide management plan has been developed outlining immediate, short-term and long- term options and programmes that should be implemented. Immediate options are steps that can be taken to quickly increase the safety of road users and include moving of highway closure gates and installation of warning signage. Short-term options aim to mitigate landslide hazards where feasible including the installation of rockfall barriers and debris flow attenuators, and lay the groundwork for future avoidance of hazards by undertaking investigations of highway realignment and developing highway closure rainfall thresholds. Long-term options are recommended where landslides will continue to impact the same section of the highway repeatedly and focus on hazard avoidance by building landslide shelters or major highway realignments. The adoption of a management plan ensures security of the highway, protects against loss of life and provides the most cost effective long-term solution to manage the landsliding hazards.

Samples of an over-consolidated saturated silty clay, Keuper marl, and a partially saturated granular material, Breedon gravel, have been used in a triaxial test programme, with a view to characterising certain aspects of the material behaviour for use in a flexible pavement design procedure. Samples of over-consolidated Keuper marl were subjected to repeated axial sinusoidal loads. In addition, further samples were tested under creep loads and standard slow rate of strain triaxial tests. The results from these tests are used to relate the plastic deformation under repeated loads to simple creep tests and to the standard undrained soil strength test. In addition, the resilient behaviour is shown to be a function of the stresses applied to the soil. The samples of granular material were tested drained and were subjected to cyclic vertical and horizontal stresses. The development of a method of lateral strain measurement allowed a fundamental analysis of the behaviour of this material under a cyclic lateral stress. The resilient and permanent deformations occurring under a cyclic horizontal stress have been related to those occurring under the simpler situation of a static horizontal stress. A review of previous work considers research carried out on flexible pavement design with special reference to the role of unbound materials. In addition, an outline is given of studies carried out on creep of clays and repeated behaviour of clays and granular materials. The behaviours of the silty clay and the granular material are analysed in the context of a theoretical pavement structure. The basic testing apparatus is outlined briefly, while developments to the apparatus including an automated computer based data collection system are described in the form of appendices. A summary of the test results is given in the conclusions together with suggestions for further work.

With ever increasing demands on land use large areas of land are being considered for development which due to past or present mining activities are covered by substantial depths of fill materials. The problem faced with the development of land infilled with open cast mining backfill is in predicting the behaviour of the fill upon development. To be able to design foundations suitable to withstand the movements that occur within opencast backfill or design a backfilling operation that produces land suitable for a proposed after development, a means of predicting backfill settlement is required. From the analysis of a considerable quantity of data collected from the monitoring of backfilling operations and backfill movement at a range of opencast coal sites located within the UK, the behaviour of opencast backfill has been examined and better understood. This information has enabled a method of predicting backfill settlement to be developed which has been subsequently implemented as a computer program running under the Windows operating system. Factors taken into consideration during the prediction process are the timing of backfilling operations, the compactive state of the backfill, the inundation of the backfill and the influence of surrounding material and a means of predicting differential settlement due to backfill heterogeneity is proposed. Examples are given demonstrating the significance of these factors upon settlement predictions made at a hypothetical site. Finally, a comparison is made between predicted settlements and those monitored at an actual site to demonstrate the validity of the method proposed.

With the increased availability of computers of various sizes, it is becoming more common to predict the responses of geotechnical structures using numerical analyses which incorporate more realistic models of soil behaviour. The main objective of this research is to develop and evaluate a series of unified critical state models. These models are then used to solve some typical boundary value problems in geotechnical engineering. The new models are based on a critical state model called CASM which was formulated based on both the state parameter concept and a non associated flow rule. The main feature of CASM is that a single set of yield and plastic potential functions is used to model the behaviour of clay and sand under both drained and undrained loading conditions. These models are developed by incorporating a new non-linear elasticity rule, the combined hardening concept and the bounding surface plasticity theory. A new non-linear elasticity rule for clay materials is introduced into CASM, this gives a better prediction on the behaviour of soil. The new combined volumetric-deviatoric hardening model is named CASM-d and provides a better prediction of the behaviour of lightly overconsolidated clays and loose sands. The new bounding surface model is named CASM-b and provides a more realistic prediction of soil behaviour inside the state boundary surface. The new cyclic bounding surface model is named CASM-c and provides a good prediction of soil behaviour under cyclic loading conditions. To evaluate their adequacy, CASM and its extensions are implemented into a finite element package called CRISP. This program was specifically developed to incorporate the critical state type of constitutive models. The analyses of a variety of typical geotechnical engineering problems are carried out to further check the validity of the new constitutive models. The models prove themselves to be very robust and useful tools for solving a wide range of practical geotechnical problems under different loading conditions.

Artificial ground freezing (AGF) provides a means by which excavations can be given temporary or permanent structural support. It may also be used to control the movement of groundwater without the risk of pollution of potable aquifers. As AGF is called upon to strengthen ground at ever increasing depths, the design process needs to be adapted to account for the greater stresses encountered. In strong materials, the prime consideration is the short term strength of the materials and closed-form formulae can be used in design. In weaker materials, the time dependent creep behaviour of the frozen ground predominates and more complex analysis techniques have been devised (e. g. finite elements). Previous works in this field have been chiefly concerned with uniaxial states of stress. In this thesis, consideration is given to the problem of modelling creep under triaxial stress conditions. An introduction is followed by an outline of the general applications and design procedures currently used in ice wall design. Descriptions are then given of a selection of soils and weakly cemented rocks which have been incorporated into a programme of tests to investigate both short and long term strength behaviour. The apparatus available at the start of this project was suitable for uniaxial and low pressure triaxial tests only. Equipment subsequently developed to extend the confining pressure capability to 12 MPa, is described in detail. Short term strength tests show the increase in strength on freezing of ground materials is almost entirely due to the cohesion contributed by the ice matrix. Analysis of the creep test results leads to the development of a new empirically based triaxial creep equation for frozen soils. A sensitivity analysis of the parameters in this equation is followed by its application to a simplified design. Suggestions for further work in this field are included.

Thesis (MS )--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Robert L. Mokwa. Includes bibliographical references (leaves 100-109).

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Mary F. Wheeler. Vita. Includes bibliographical references. Also available from UMI.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb. 23, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dr. Brent Rosenblad, Dissertation Supervisor. Vita. Includes bibliographical references.