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The Screw Driving Sounding (SDS) method developed in Japan is a relatively new in-situ testing technique to characterize soft shallow sites, typically those required for residential house construction. The method consists of drivi...
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The Screw Driving Sounding (SDS) method developed in Japan is a relatively new in-situ testing technique to characterize soft shallow sites, typically those required for residential house construction. The method consists of driving a rod, equipped with a screw point at the tip, into the ground at different steps of loading while being rotated. The machine used to penetrate the rod can measure continuously the required torque, load, speed of penetration and rod friction; thus, compared to the more popular Standard Penetration Testing (SPT) and Swedish Weight Sounding (SWS) techniques, the method can provide a better insight of the soil profile. In this paper, the SDS method is introduced and the results of its application to characterize Christchurch sites-are discussed. Since most of the tests were conducted at sites where Cone Penetration Tests (CPT) and borehole logs are available, the comparison of SDS results with this information shows that the SDS method has great potential as an in-situ testing method for geotechnical site characterization.
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The Debswana Diamond Company (DDC) Jwaneng mine in Botswana, is a large open pit diamond mine extracting three kimberlite pipes. Open pit operations will cease in the early 2030s; studies are currently underway to transition to an...
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The Debswana Diamond Company (DDC) Jwaneng mine in Botswana, is a large open pit diamond mine extracting three kimberlite pipes. Open pit operations will cease in the early 2030s; studies are currently underway to transition to an underground operation at the cessation of open pit mining. It is anticipated that underground mining will be undertaken using a combination of sublevel caving (SLC) and other caving methods; mining will extend to a depth of ~1,000 m below surface. The Jwaneng open pit has been in full production since 1982 and has a mature high-quality geotechnical model that has been progressively developed and improved over many years. Debswana makes use of a geotechnical review board to guide the development of the geotechnical model.The comprehensive geotechnical model is the foundation for all the open pit and underground designs at Jwaneng. The geotechnical model comprises of several components: lithology model, major structures model, rock mass model, fabric model and hydrogeology model. For the underground studies the geotechnical model has been extended in both depth and lateral extents. In 2018 the geotechnical logging procedure was changed to incorporate parameters and rock mass indices appropriate for underground mining. The Jwaneng mine is structurally complex with many large geological structures and a variable rock mass with strengths ranging from weak kimberlites (25 MPa) to very competent dolomites (>250 MPa).The various components of the geotechnical model are regularly updated; generally, this is planned to coincide with the study stage, the intent being to meet the confidence level required for each stage. This paper considers all components of the geotechnical model but focuses on rock mass and fabric models for the underground studies. This included developing systems and workflows to allow for comparison of the pre and post 2018 geotechnical data before combining the data. Length weighted histograms and descriptive statistics for various parameters (RQD, Q', RMR_(89), RMR_(2000), GSI, etc.) were determined for different lithologies and structural blocks to assist with defining geotechnical domains.
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Selection of appropriate shearstrength parameters for mine spoil slope stability analysis and design is difficult because it requires prohibitively large laboratory equipment to test characteristic spoil samples under meaningful s...
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Selection of appropriate shearstrength parameters for mine spoil slope stability analysis and design is difficult because it requires prohibitively large laboratory equipment to test characteristic spoil samples under meaningful stresses. A convenient alternative to estimate mine spoil shear strength is to adopt published guidelines that have been tried-and-tested in practice. For more than two decades, the Australian coal mining industry has adopted a linear shear strength framework derived from small-scale test data and verified in practice by slope performance of dragline-scale spoil dumps up to 120m in height, and to date this framework has appeared reliable. However, in the field ofrockfill dam design there is a broad acceptance of a curvilinear shear strength envelope, and if this is applicable to coal mine spoils, then this industry-accepted framework may overestimate the strength and stability of dumps at higher stress levels. This is particularly relevant in modern times where dump heights (>350m) often exceed the scale (<120m) for which the framework was developed. This paper explores the applicability of this framework for high-dump situations fora range of coalmine spoils. This is achieved by comparing their framework-assigned strength envelopes with direct measurements of their strength obtained from a custom-built large direct shear machine (LDSM). The machine can test at a much larger scale, in terms of combined specimen size (720mm x 720mm x 600mm) and stress (σ'_nup to 4.6MPa) than has ever been achieved using a direct shear machine for geotechnical testing of rockfill. A critical outcome is that the LDSM data highlights several non-compliant mine spoils, and stress-dependent shearing behaviour, for which correct application of the published framework will not provide reliable shear strength parameters for design.
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A fine-grained industrial sludge is to be used to construct an embankment founded on previously disposed and comparatively consolidated sludge. Various laboratory and in situ tests have been carried out to ascertain the engineerin...
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A fine-grained industrial sludge is to be used to construct an embankment founded on previously disposed and comparatively consolidated sludge. Various laboratory and in situ tests have been carried out to ascertain the engineering properties of the sludge and to investigate the stability of the dam. The general properties and behaviour of the sludge have been found to correspond closely to that of clay and it is suitable for the construction of the dam.
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A fine-grained industrial sludge is to be used to construct an embankment founded on previously disposed and comparatively consolidated sludge. Various laboratory and in situ tests have been carried out to ascertain the engineerin...
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A fine-grained industrial sludge is to be used to construct an embankment founded on previously disposed and comparatively consolidated sludge. Various laboratory and in situ tests have been carried out to ascertain the engineering properties of the sludge and to investigate the stability of the dam. The general properties and behaviour of the sludge have been found to correspond closely to that of clay and it is suitable for the construction of the dam.
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In the South Baltic cooperation project DredgDikes different dredged materials are investigated to be used in dike construction. Depending on the type of dredged material combinations with different geosynthetic solutions and comp...
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In the South Baltic cooperation project DredgDikes different dredged materials are investigated to be used in dike construction. Depending on the type of dredged material combinations with different geosynthetic solutions and composites from dredged materials and ashes are tested. The investigations are mainly performed in Rostock and Gdansk. In Rostock, focus is given to uncontaminated fine-grained organic dredged materials from the Warnow river delta, dewatered and ripened on the Hanseatic City of Rostock's containment areas. Therefore a considerable geotechnical and chemical laboratory programme has been performed for material characterisation and a large-scale experimental dike has been built. The dike with a height of 3.30 m consists of ten different cross-sections with three different dredged materials, different geosynthetics solutions, and varying slope inclination. Since the dredged materials possess high natural water contents even after the ripening process, they tend to considerable shrinkage, which is why geosynthetic reinforcement has been placed in parts of the dike cover layers to reduce cracking. Also geosynthetic erosion control products have been installed at parts of the surface to reinforce the roots of the turf and thus to strengthen the whole construction with respect to surface erosion. The construction can be filled with water for seepage investigations and some sections are prepared for overflowing experiments to test crest and landside slope with respect to erosion stability. Additional laboratory tests have been performed of which an overflowing test is presented in more detail. Both on the dike and on especially prepared testing plots the turf development on different dredged material surfaces and in different weather conditions has been investigated. The first results have been summarised here. Apart from general problems on the construction site in the very wet summer of 2011, the installation of the dredged material in the experimental dike was unproblematic. Different compaction approaches have been examined and the results are presented here.
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In the South Baltic cooperation project DredgDikes different dredged materials are investigated to be used in dike construction. Depending on the type of dredged material combinations with different geosynthetic solutions and comp...
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In the South Baltic cooperation project DredgDikes different dredged materials are investigated to be used in dike construction. Depending on the type of dredged material combinations with different geosynthetic solutions and composites from dredged materials and ashes are tested. The investigations are mainly performed in Rostock and Gdansk. In Rostock, focus is given to uncontaminated fine-grained organic dredged materials from the Warnow river delta, dewatered and ripened on the Hanseatic City of Rostock's containment areas. Therefore a considerable geotechnical and chemical laboratory programme has been performed for material characterisation and a large-scale experimental dike has been built. The dike with a height of 3.30 m consists of ten different cross-sections with three different dredged materials, different geosynthetics solutions, and varying slope inclination. Since the dredged materials possess high natural water contents even after the ripening process, they tend to considerable shrinkage, which is why geosynthetic reinforcement has been placed in parts of the dike cover layers to reduce cracking. Also geosynthetic erosion control products have been installed at parts of the surface to reinforce the roots of the turf and thus to strengthen the whole construction with respect to surface erosion. The construction can be filled with water for seepage investigations and some sections are prepared for overflowing experiments to test crest and landside slope with respect to erosion stability. Additional laboratory tests have been performed of which an overflowing test is presented in more detail. Both on the dike and on especially prepared testing plots the turf development on different dredged material surfaces and in different weather conditions has been investigated. The first results have been summarised here. Apart from general problems on the construction site in the very wet summer of 2011, the installation of the dredged material in the experimental dike was unproblematic. Different compaction approaches have been examined and the results are presented here.
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Rock mass classification systems are widely used by geologists and geotechnical engineers for the classification, empirical design, and numerical modelling, especially during the first stages of a mining project, such as for Scopi...
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Rock mass classification systems are widely used by geologists and geotechnical engineers for the classification, empirical design, and numerical modelling, especially during the first stages of a mining project, such as for Scoping and Pre-Feasibility studies.The most used systems in the mining industry are represented by Laubscher rock mass rating, Bieniawski rock mass rating, Barton Q, Laubscher and Jakubec in situ rock mass rating system, and Hoek-Brown geological strength index, consisting of empirical methods that characterise, in a simple and fast way, the rock mass quality while offering engineering applications to the geotechnical design, such as ground support design, pillar strength estimation, fragmentation, rock mass strength, caveability, among others.The authors have been involved in all the engineering stages of numerous large mining projects, from the scoping to the construction, passing through due diligence and peer review. When reviewing the geotechnical database of these projects, common and frequent errors seem to repeat, related to the collection of the basic geotechnical parameters.The most frequent errors are associated to a mistaken distinction among natural and mechanical discontinuities, erroneous joint counts and consequently FF/m calculation and a wrong assessment of the rock quali':/ designation. Other typical errors have been detected in the assessment of the joint condition, most of them referred to the characterisation of the joint alteration (J_a) Barton parameter.The aim of this paper is to show the impact of the geotechnical errors and mistakes over the geomechanical design, quantifying the variation in terms of rock mass strength, caveability, pillar strength, Factor of Safety, etc., that will produce a negative impact on both the capex, opex and high risk for a mining project and/or operation.
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The success of any geotechnical design is dependent on the geotechnical model used in the design assessments. No matter the methodology adopted, the budget allocated, or the expertise assembled for the design analyses, an unsuitab...
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The success of any geotechnical design is dependent on the geotechnical model used in the design assessments. No matter the methodology adopted, the budget allocated, or the expertise assembled for the design analyses, an unsuitable geotechnical model will result in a sub-optimal outcome or misleading results. The nature of any geotechnical model must be dependent on the type, amount, and spatial distribution of the information available and the purpose for which the model is constructed. A geotechnical model for an open pit must allow for the generation of slope design parameters that are most appropriate for the geotechnical environment, taking into account the dominant mode/s of failure, the level of confidence in the data and acceptable levels of risk. It may require a significant amount of evaluation, interpretation, and judgement to develop a model that is fit-for-purpose, even for one that appears simple. It is better for it to be approximately 'right' than precisely 'wrong'! This paper discusses the conception and development of appropriate geotechnical models for slope design. It considers the types of information available, the level of study, the shape of the excavation, controlling failure mechanisms, and uncertainties. It discusses how a model can be spatially defined and how the data can be best used to characterise each zone. The lithology, alteration, structural and hydrogeology models that contribute to the geotechnical model, and the likely slope failure mechanisms are important in selecting appropriate software or analysis methods that should be employed for slope design analyses. In this context, typical pitfalls in geotechnical models are examined.
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Many past research works proved the successful usage of synthetic geotextiles and geogrids as road subgrade reinforcement. However, reinforcing subgrades with natural geotextiles is found to be more economic and eco-friendly. The ...
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Many past research works proved the successful usage of synthetic geotextiles and geogrids as road subgrade reinforcement. However, reinforcing subgrades with natural geotextiles is found to be more economic and eco-friendly. The usage of this is limited by its short degradation time period in soil, and to overcome this, researchers started using treated geotextiles. In this study, a systematic lab investigation has been made to understand the behavior of subgrade strength of roads reinforced with alkali activated binder (AAB) treated jute geotextile. Unreinforced soils, untreated and treated jute reinforced soils are tested for CBR, bearing capacity, and the results showed a considerable increase of CBR, bearing values in treated jute geotextiles.Durability tests such as soil burial tests and tensile strengths of degraded JGT are also carried to study the increase in life expectancy of AAB treated jute geotextile. Alkali activated binder improves life expectancy and mechanical properties of jute,and therefore, treated jute geotextile may be used as alternative material for subgrade soil reinforcement applications.
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