Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Oil & Gas
Abstract In this study, the possibility of measuring rock surface roughness by means of open-source photogrammetric methods was investigated. With simple commercially available digital cameras, samples of varying roughness were measured. As a reference, the samples were also measured with a high-resolution white light strip scanner and additionally manually with a contour gauge. By comparing the digital datasets it became clear that the open-source structure-from-motion (SFM) algorithms were able to capture the overall topography but with clearly less accuracy than the white light scanner. This had a marked influence on the determined roughness parameter JRC (joint roughness coefficient). For smooth surfaces the JRC was higher than the reference value, for rough surfaces it was lower. In general, with the introduced method it was possible to reproduce the surface of the rocks but care has to be exercised when roughness parameters are to be deduced from the datasets. 1 Introduction The shear strength of rock joints is primarily dependent on their surface roughness. In order to achieve a save and cost-efficient design in rock engineering it is desirable to measure joint roughness as accurate as possible. In the past, tools like contour gauges (Barton & Choubey 1977) and mechanical profilometers (e.g. Weissbach 1978) were used to measure unevenness of rock surfaces. Nowadays, high-resolution laser scanners (e.g. Fardin et al. 2001, Milne et al. 2009) or white light strip scanners (Tatone & Grasselli 2013) are applied to investigate rock surfaces. But, as these methods being cost-intensive, alternatives are needed. Therefore, in this study, open-source photogrammetric software was utilized to measure surface roughness. With a simple off-the-shelf digital camera in connection with well-established structure from motion algorithms five surfaces varying in roughness were investigated.
- Europe (0.70)
- North America > United States (0.29)
- North America > Canada > Ontario > Toronto (0.15)
- Geology > Rock Type (0.55)
- Geology > Geological Subdiscipline > Geomechanics (0.32)
Abstract Global warming is one of the major threats of 21st century and the CO2 sequestration in unmineable coal seams can be a feasible solution to this problem. However, the effect of CO2 on the physical and mechanical properties of the host rock has a major control on the storage capacity of the coal seams. This paper presents the results of a laboratory based CO2 sequestration study on the Indian coal. The coal samples were treated for twenty-five and forty-five days in a "saturation chamber" under a low pressure and room temperature condition. The mechanical, physical and mineralogical properties of the pre- and post-saturation samples were analyzed to identify the potential changes. The comparative analyses show that CO2 adsorption in the coal matrix has a negative effect on the strength of coal. Moreover, the post-saturation particle size and pore size reduction are interpreted to be a direct effect of this adsorption. 1 Introduction Carbon dioxide sequestration has emerged as one of the most potential way to curb the global carbon dioxide emission. In this regard, the high CO2 adsorption capacity of coal makes it an ideal candidate for sequestration. With the increasing global interest in the carbon dioxide sequestration and associated coal bed methane (CBM) recovery, a plethora of research have been undertaken throughout the world to investigate the mechanical, strength and reservoir properties of the coals (Khandelwal & Singh 2010, Busch & Gensterblum 2011 and Masoudian et al. 2013). Researchers have experimentally evaluated the effect of CO2 adsorption on the physical properties of different coals (Ettinger & Lamba 1957, Vishal et al. 2013 and Vishal et al. 2015). However, the relation between the adsorption nature and the poro-mechanical behavior of the coal varies widely and a generalized consensus is yet to be achieved. This is mainly because, the coal properties are controlled by the organic content, grade and rank of the coal, depth of the seam, presence of cleat, confining pressure and the surrounding temperature. So, it is required to develop basin and coal seam specific understanding of the strength properties of coal under normal and fluid-saturated conditions. This article discusses the results of an experimental investigation on the effect of carbon dioxide on the strength and micro-structure of Indian coal. By correlating the post-treatment strength of the coal with its micro-properties, a conceptual model of this interaction has been developed.
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (1.00)
- Geology > Geological Subdiscipline (1.00)
- Materials > Metals & Mining > Coal (1.00)
- Energy > Oil & Gas > Upstream (1.00)
Abstract Rock scours after a spillway of a dam can lead to major problems regarding the stability of the structure. The pressures on the floor are dependent on the height of the dam and the water cushion in the pool. They can reduce the effective stress between the rock blocks significantly and hence the friction resistance. This mechanism leads to proper instabilities in the foundation and the structure. A model test at the Institute of Hydraulic Engineering and Water Resources Management should expose the pressures on the bottom floor. The results of the test case show a significant decrease of these pressures due to the evaluated configuration of the model. Further investigations, in a more detailed model, with cracks in the rock for different quantities of the jet velocity and the depth in the stilling basin are planned as well as numerical simulations by means of fluid-foundation interaction for comparison reasons. 1 Introduction Rock scour next to the spillway of dams can influence the stability of the structure significantly. Dynamic pressures on the rock foundation due to the impact of high velocity jets lead to abrasion and hence instability. The increasing accuracy of methods for determining the hydrological data lead to assessment criteria that are more exact (Achterberg et al. 1998). This fact concerns mainly older structures, where additional measurements will therefore be necessary. In addition, newer structures are also affected by rock scour, because the knowledge about theses dynamic pressures is still very limited. Although, more and more papers have been published in this field recently (e.g. Bollaert 2002). However, the foundation at the impact zone will crack eventually and the dynamic pressures induced will propagate through the cracks and possible fault zones. These water pressures can reduce the effective stress between the rock blocks significantly and hence the friction resistance. A model test for a survey at the Institute for Hydraulic Engineering and Water Resources Management at Graz University of Technology led to the idea to investigate this problem more elaborated. Therefore, a more detailed model with a wedge and joints is planned to be evaluated along with different discharges and water depths (water cushion) as well as numerical simulations for comparison reasons.
Abstract It is a widely accepted opinion in the tunnelling community that the primary stress state influences the cutting process, however basically no rigorous analysis regarding these effects has been conducted. In order to better understand these effects, the work has been separated in the following steps:A 3D numerical analysis of the secondary stress state in the rock mass while the advance approaches a fault zone, thus causing a stress increase in the face area of the competent pillar; 3D numerical analysis of the cutting process on heterogeneous numerical models with brittle softening behavior, with various stress states as determined from the overall 3D analysis. The results allow definite qualitative statements about the influence of the stress state 1 Introduction As the TBM performance prediction is used to make reliable cost and price estimates as well as to characterize the ground conditions, special attention has been given to this currently insufficiently explored issue. Therefore, the influence of the primary stress state has to be investigated, as it is a widely accepted opinion that it has an influence on the cutting process. In order to examine the influence of the primary stress state, the research is based on four different fields of activity:Numerical modelling of a TBM advance towards a fault and examination of the stresses induced at the face; TBM data analysis from real projects (currently pending); Numerical simulation of the cutting process with a highly sophisticated numerical model and examination of the influence of the stress boundary conditions on the cutting process; Laboratory testing of the cutting process with and without confinement stresses, in order to verify the findings of the numerical analysis. This paper concerns only the numerical simulation of the TBM advance and estimation of the secondary stresses, and their evaluation regarding cutability.
- Europe (0.73)
- North America > United States > Colorado (0.15)
Numerical Study on Slope Stability in Consideration of the Influence of Weathering by Two-Phase Flow Analysis
Ishida, Jumpei (Nagasaki University) | Jiang, Yujing (Nagasaki University) | Omine, Kiyoshi (Nagasaki University) | Sugimoto, Satoshi (Nagasaki University) | Higashi, Yukihiro (Geoscience Research Laboratory) | Ogata, Yusuke (Nihon Chiken Co., Ltd)
Abstract In recent years, localized torrential rainfall caused by abnormal weather happens frequently, which triggers numerous sediment disasters accompanied with slope failure. Generally, slope stability analysis is performed, considering the parameters of the soil layers as homogeneous. However, in fact, soil particle configurations vary with depth, due to the influence of weathering. In this study, numerical simulations are performed with the reduction of cohesion and increment of friction angle taking into account the ground weathering with depth, utilizing the finite difference method (FDM). There are two types of failure modes, failure of whole weathered soil layer and surface of lower slope. Based on these results, it can be concluded that cohesion has greater impact for shear resistance force than friction angle in surface layer, conversely, at the boundary between weathered soil layer and strongly weathered rocks, friction angle has a greater impact on shear resistance force than cohesion. 1 Introduction In recent years, localized torrential rainfall caused by abnormal weather happens frequently, which triggers numerous sediment disasters accompanied with slope failure. If there is a technique to detect a slope which has potential of failure or may present behavior of failure, it would greatly contribute to slope disaster preventions. During the heavy rainfall, saturability of the ground increases rapidly with water flow. It is considered that pore air closing is caused with rapid water flow in some cases. Since natural slope is often unsaturated, it is required to consider the effects of pore air pressure. Generally, slope stability analysis is performed, considering the parameters of soil layer as homogeneous. However, as a matter of fact, soil particle configurations vary with depth due to influence of ground weathering. In this study, coupled stress-flow analysis is performed by calculating two-phase flow, taking into account the effects of pore air pressure. Furthermore, the impacts of weathering on slope stability are also investigated.
Abstract Deep-hole resistivity anomaly was observed in Heping geoelectric station before the earthquakes occurred in Heyuan. Different from the resistivity anomaly of most resistivity stations in China, the daily mean value curve of resistivity in Heping station shows long trend of decline in quiet periods while turns flat or rising before the earthquakes. In this paper, based on the geological and hydrological information near the station, a series of three-dimensional finite element models were constructed to analyze and verify the disturbance caused by the electrode polarization, the changes of moisture content and water table in the rock masses. The results of simulation indicate that 1) under constant stress in the quiet period, with the electrode polarization, the apparent resistivity has a downward trend; 2) before the earthquake, with the compressive stress increased, the comprehensive effect of rising high-conductivity particles and increasing water table will jointly lead to the flat or rising trend. 1 Introduction Earth resistivity observation is known as a resultful earthquake precursor method. In China, ground surface electrodes are widely applied in the apparent resistivity observation, and the electric current concentrates upon the surface of the earth and it is easily interfered by the environment changes such as temperature, rainfall, human activity etc. The resistivity observation with deep-hole electrodes is similar to the whole space measurement so it is efficacious in reducing the interference effect and increasing the observation accuracy (Liu et al. 1994). Heping geoelectric station is located in Heping Village Heyuan city, about 6 km east of Hsinfengkiang Dam where the 1962 Ms6.1 earthquake occurred. This survey area is with smooth terrain and small relative height difference. This low hill red rock terrace with altitude 70 m is mainly composed of Cretaceous sandstone and conglomerate. The electrodes are more than 500 m away from west and southwest river. Schlumberger array is used in this observation, the array orientation is N80°W, the source electrodes spacing is 54 m (AB) and the measuring electrodes spacing is 18 m (MN), electrode buried depth is 65 m (see Figure 1). The electrodes are made by lead with solid cylinder shape. Observation instrument is CAT-S digital earth-resistivity equipment developed by earthquake administration of Guangdong province, China.
Abstract Non-Euclidean continuum model is used for construction of the stress field for different problems. The general idea of the model is to introduce the parameter which allows us to describe incompatible deformation of rock masses in the terms of the non-Euclidean geometry. The non-Euclidean continuum model is applied for description of the zonal stress field around a cylindrical opening. The phenomenological parameters of the model are determined on the basis of comparison with experimental data. The anomalous deformation behavior in the cylindrical rock sample is analyzed on the foundation of the non-Euclidean continuum model as well. The problem of the non-Euclidean continuum model application to the mesocracking structures description on the different hierarchical rocks and rock massifs levels is discussed. 1 Introduction The excavation of underground openings at great depths is a challenging issue for mining engineers. Deep rock masses are characterized by zonal disintegration which is referred as a zonal quasi-periodic structure around an excavated rock. The zonal failure structures were widely observed in deep gold mines in South Africa (Adams & Jager 1980). Similarly, the zonal disintegration phenomena have also been discovered in the Taimyrskii and Mayak mines in Russia (Shemyakin et al. 1986). The zonal structure is characterized by the occurrence of irreversible strains ije in a rock and leads to the incompatibility condition for eij. In the classical theory of elasticity, the strain deformations satisfy the Saint-Venant compatibility conditions. So a novel theoretical idea is founded on abandoning the kinematics hypothesis of the classical continuum model. From the mathematical viewpoint it means that the internal geometrical structure of the rock does not coincide with the geometry of the observer's Euclidean space (Guzev 2010). The standard formalism of non-equilibrium thermodynamics was used to obtain the constitutive equations for the non-Euclidean model. However from a physical perspective, its geometric characteristics cannot be directly measured. Therefore, practical results of the model can be verified by a comparison with experimental data.
- Materials > Metals & Mining (0.69)
- Energy > Oil & Gas > Upstream (0.47)
Abstract Multiple Point Geostatistics (MPS) is a timely approach for the three-dimensional modeling of the geological substrate. As compared with 3D design approaches, model update is straightforward and reproducible. In contrast to traditional, variogram-based geostatistical modeling and simulation, MPS incorporates geological expert knowledge via a Training Image (TI). The TI permits geologists the intuitive formulation of geometrically complex geological structures plus their genetic relationships like cross-cutting joint generations or mutually eroding sediment types. MPS extracts patterns and associated statistical parameters from the TI. During simulation, patterns are conditioned to hard or soft primary data like outcrops, drillings or geophysics. MPS simulation yields equally probable realizations, enabling scenario modeling at the voxel-level. In a processing pipeline, MPS results convey to FE or particle modeling (hydrological, rock mechanical) as 2D or 3D grids. MPS versatility is demonstrated with examples from tunneling in hard rock and from aquifer modeling. 1 Geostatistical Geological Modeling With roots in the concept of random variables (Journel 1989, Cressie 1993), geostatistics deals with "the study of phenomena that fluctuate in space and/or in time" (Olea 1991). More on an applied geology level, geostatistics can be seen as a toolbox for the analysis, optimized modeling and simulation of 3D spatial variability. Geostatistics handles metric data - e.g., geochemical concentration or porosity - as well as categorical data like rock class or joint type. Compared with 3D design approaches (CAD-based 3D modeling sensu lato), which yields surfaces or internally homogeneous 3D-solid bodies, geostatistics provides results in grid format. Geostatistical 3D-models are voxel models i.e., the modeling volume is made up of adjacent, non-overlapping prismatic unit cells that store the result (Marschallinger et al. 2014). As opposed to deterministic grid modeling approaches like inverse distance, minimum curvature, radial basis functions etc., geostatistics explicitly incorporates uncertainty. This is the basis for dedicated scenario modeling (Caers 2011).
- Geology > Geological Subdiscipline (0.68)
- Geology > Rock Type (0.51)
Abstract We use a model analysis for explaining the fracture movement caused by the thermal expansion of the rock in two configurations. The first is a rock heating experiment, instrumented by both stress and displacement sensors, where the model can partly explain a combination of the sensor expansion together with the compressive stress by shear fracture movements. The second is a tunnel with the seasonal varying temperature, crossed by sub vertical fractures not perpendicular to the axis – different volume of each side of the fracture results in different expansion to the tunnel space. The model is based on the specific use of 2D or 3D finite elements for the rock continuum. Case studies include the computing of the threshold of thermal-induced displacement (or stress) changes in the massif, with a possible comparison with the measurement. 1 Introduction Effect of fractures is one of the difficulties in numerical simulation of phenomena in the rock mechanics. Standard methods evaluate the rock properties in the scale above the fracture scale, allowing use various equivalent continuum methods. Fractures can be included as discrete objects between either rigid or deformable blocks – by means of e.g. discrete/distinct element methods – or be included to an existing continuum discretization in the extended finite element method (XFEM). The former is used by several established rock mechanics simulation codes, with selection of semi empirical stress-strain or strength constitutive relations. While these are specific features of rock mechanics, they are not easily available in general-purpose multiphysics codes. In this work, we demonstrate a simple approach to include fractures with use of a linear-elastic model – therefore accessible in COMSOL software used for the previous continuum models. The purpose of the model studies is to check the possible effects of fracture – if they can contribute to an explanation of the measured phenomena. It is convenient to start with a simpler extension of the current model and after the evaluation, it can tell if it is worth to consider a use of a specific method or code with realistic constitutive relations. The work is motivated by two projects in the sites in the Czech Republic. In the first, the coupled thermo-mechanical model without fractures has been developed formerly and verified successfully. The comprehensive case study is nowadays prepared for a separate publication (Rálek et al. 2015).
Abstract The bigger mine waste dumps create the greater the issue to encounter in situ ground conditions. Landfill rock waste makes an inadequate strength and economic issue of the reclamation work is more difficult, especially in determination of slope stability. A clear differentiation based on the lump-size rock type and soil distribution and compression in the field of reclamation. GEO5 FEM, Rocklab and Stereonet7 programs performed with four rockfill modeling and stability analysis for A1, A2, A3 and A4 rock fills models where rock fills of the dump slope were limited. Anisotropic rockfill and soil mixture models were made in laboratory scale. Heterogeneous geotechnical parameters were analyzed. Regarding the topographic maps produced in the 1/1000 scale with field work and the structural cross sections of rock fill models conducted on laboratory experiments, the physical and mechanical properties for each A1, A2, A3 and A4 Models. A1, A2 slopes were close to stable state that showed to be slight safety risk. However, GEO5 programs with limestone fill model through FEM program exhibited stability with A3 and A4. 1 Introduction Because of growing urbanization, reclamation of mine waste dumps is required and has to be concerned. New and bigger urbanization area may face to the reclamation issue around the civil structures. The geotechnical parameters of ground are the decisive factor regarding the type of slope stability work and its efficiency (Bieniawski 1967, Cernica 1995, Das 1994). In the stable ground, the slope has to be actively supported in order to avoid ground settlement. Modified impact resistance of rocks makes use of the 20–30 cm lump massive rock model to provide face scale to 2–3 cm. The indentation by the drilling bit enters in-situ the massive lump rock, where the volume of rock retained can regulate through the advance rate. Depending on the resistivity of the rock volume in the dump, the indentation pressure can be controlled. The pressure can be calculated depending on the slope (bit diameter, overburden depth), geological and hydrogeological conditions and any surcharge in the area affecting the stability alignment (Görög & Török 2006, Görög & Török 2007). The calculation of slope stability of mixed face conditions of the varied rockfills such as local porous limestone, marly limestone. The waste shale and marly shale is based on the assumption of a linear (hydrostatic) distribution of support pressure over the face, which is in equilibrium with the scaling ground and water pressures in laboratory model (Bishop 1955, Hoek 1970, Hoek 2013, Hoek & Brad 1977). However, evaluation of data is made by GEO5 FEM model program (Anonymous 2009, Anonymous 2009, Pruska 2009). Earth face in-situ measurement systems have demonstrated dynamic non-linear stress distribution with strong fluctuations at times of high tonnage lorries transfer. This showed in particular differences between the phones at the slope face and critical weakness spaces in the dumps.
- Europe (0.69)
- Asia > Middle East > Turkey (0.48)
- North America > United States (0.29)
- Geology > Rock Type > Sedimentary Rock > Carbonate Rock > Limestone (0.68)
- Geology > Rock Type > Sedimentary Rock > Organic-Rich Rock > Coal (0.50)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Mudrock > Shale (0.48)
- Water & Waste Management > Solid Waste Management (0.91)
- Energy > Oil & Gas > Upstream (0.89)
- Materials > Metals & Mining (0.83)