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Journal of Rock Mechanics and Geotechnical Engineering 2021年第2期13卷 275-288页

作者： Sankhaneel Sinha gabriel Walton Geology and Geological Engineering Colorado School of MinesGoldenCO80401USA

Bonded blockmodel(BBM)has shownpotential in replicating rockmass behavior aswell as the rockesupport interactionmechanism,but their practical application is limited totwo dimensions due to the high associated computational *** allow for the use of BBM in simulating three-dimensional(3D)problems,this study proposes an integrated 3D continuumetwo-dimensional(2D)discontinuum approach,in context of rock pillars.A cross-section of a granite pillar was simulated using a BBM with a load path from a calibrated mine-scale FLAC^(3D)*** support as employed in the mine was also incorporated in different stages during the *** was calibrated by varying the input parameters until the displacements at six locations within the pillarmatchedthosemeasuredby amulti-point borehole extensometer(MPBX)inthe *** calibratedmodel was subsequently used to understand how the support and load path influenced the damage evolution in the *** shear component of the load pathwas found to have amajor effect on the severity and extent of the damaged *** the support density was increased in the model,the lateral displacements along the pillar walls were significantly suppressed in a somewhat unpredictable *** explained by the interaction between the supports and the damaged regions at the corners,which ultimately modified the stresses along the pillar *** amount of displacement reduction obtained by increasing the support density illustrates the potential of BBMto be used as a support design tool.

关键词： Bonded block model(BBM) Rock pillars Supports Continuum-discontinuum integration

Modeling behaviors of a coal pillar rib using the progressive S-shaped yield criterion

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第3期12卷 484-492页

作者： Sankhaneel Sinha gabriel Walton Colorado School of Mines GoldenCO80401USA

Spalling of pillar ribs has been a major hazard in the mining industry for *** the absence of rib support guidelines,accidents have continued to occur in recent *** effective support guidelines requires a complete understanding of complex pillar damage *** models represent a convenient tool for analyzing this problem,but the behavior of such models is dependent of the choice of the constitutive *** this study,a recently proposed constitutive model was used to simulate the rib fracturing process in a longwall chain pillar at West Cliff *** calibration,the model was able to capture the rib displacement profiles for multiple locations of the longwall face and the stress evolution 4 m into the *** rib bolts in the model were found to be yielding over 60% of their length under the headgate loading *** model also predicted a steady damage accumulation in the rib for certain face locations,which is consistent with the description of the rib at the *** was localized along the upper part of the pillar and underscored the role that the dirt band played in controlling rib deterioration at the *** ability of the numerical model to replicate field measurements provides confidence in the capabilities of the new constitutive ***,the need of using multi-point calibration is highlighted by comparing the results of the calibrated model to an alternative model calibrated to a smaller amount of data.

关键词： S-shaped yield criterion Coal pillar Back-analysis Numerical modeling

Challenges associated with numerical back analysis in rock mechanics

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Journal of Rock Mechanics and Geotechnical Engineering 2022年第6期14卷 2058-2071页

作者： gabriel Walton Sankhaneel Sinha Department of Geology and Geological Engineering Colorado School of MinesGoldenCO80401USA

Numerical back analysis is a valuable tool available to rock mechanics researchers and *** studies related to back analysis methods focused primarily on applications of increasingly sophisticated optimization algorithms(primarily machine learning algorithms)to rock mechanics *** methods have typically been applied to relatively simple problems;however,more complex back analyses continue to be conducted primarily through ad hoc manual trial-and-error *** paper provides a review of the basic concepts and recent developments in the field of numerical back analysis for rock mechanics,as well as some discussion of the relationship between back analysis and more broadly established frameworks for numerical *** challenges of flexible constraints,non-uniqueness,material model limitations,and disparate data sources are considered,and representative case studies are presented to illustrate their impacts on back *** role of back analysis(or“model calibration”)in bonded particle modelling(BPM),bonded block modelling(BBM),and synthetic rock mass(SRM)modelling is also considered,and suggestions are made for further studies on this topic.

关键词： Back analysis Numerical modelling Inversion Case studies

Large-scale phase retrieval

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Light(Science & Applications) 2021年第10期10卷 1814-1815页

作者： gabriel Popescu Quantitative Light Imaging Laboratory Department of Electrical and Computer EngineeringBeckman Institute for Advanced Science and TechnologyUniversity of Illinois at Urbana-ChampaignUrbanaIL 61801USA

The coherent interaction between an electromagnetic field and a 3D weakly scattering medium results in a simple Fourier transform relationship between the object’s structure and the complex scattered *** a result,knowledge about the phase of the scattered field is necessary for solving this inverse problem with a unique ***,in applications,such as X-ray crystallography,typically one only has experimental access to the amplitude of the diffracted field,which results in ambiguities of the *** century-old challenge,known as“the phase problem”2 motivated the development of computational algorithms combined with a priori knowledge about the object of interest to limit the solution *** generally successful,this approach sometimes led to multiple solutions,i.e.,different inferred object structures for the same set of data:“Not all the guesses have been *** is clear,for example,from the following:Two different structures were predicted for the mineral bixbyite,one by ***,the other by *** is not known which,if either,is correct.”(Chapter 7 in ref.2).

关键词： phase scattered typically

Understanding roof deformation mechanics and parametric sensitivities of coal mine entries using the discrete element method

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International Journal of Mining Science and Technology 2020年第1期30卷 123-129页

作者： Rami Abousleiman gabriel Walton Sankhaneel Sinha Department of Geology and Geological Engineering Colorado School of MinesGoldenCO 80218USA

Although conventional coal mine designs are conservative regarding pillar strength,local failures such as roof-falls and pillar bursts still affect mine safety and *** studies have identified that discontinuous,layered roof materials have some self-supporting *** research is a preliminary step towards understanding these mechanics in coal-measure *** others have considered broad conceptual models and simplified analogs for mine roof behavior,this study presents a unique numerical model that more completely represents in-situ roof *** discrete element method(DEM)is utilized to conduct a parametric analysis considering a range of in-situ stress ratios,material properties,and joint networks to determine the parameters controlling the stability of single-entries modeled in *** results are compared to empirical observations of roof-support effectiveness(ARBS)in the context of the coal mine roof rating(CMRR)*** such as immediate roof displacement,overall stability,and statistical relationships between model parameters and outcomes are presented *** practical applications of this line of research include:(1)roof-support optimization for a range of coal-measure rocks,(2)establishment of a relationship between roof stability and pillar stress,and(3)determination of which parameters are most critical to roof stability and therefore require concentrated evaluation.

关键词： Numerical modeling Discrete element method Coal mine roof rating Analysis of roof bolt systems Sensitivity analysis Strain softening ubiquitous joints Discrete fracture network

Assessment of soil degradation and chemical compositions in Rwandan tea-growing areas

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Geoscience Frontiers 2011年第4期2卷 599-607页

作者： Jean de la Paix Mupenzi Lanhai Li Jiwen Ge Achal Varenyam gabriel Habiyaremye Nzayisenga Theoneste Kamanzi emmanuel xinjiang Institute of Ecology and Geography Chinese Academy of Sciences State Key Laboratory of Oasis Ecology and Desert Environment 818 Beijing South Road Urumqi Xinjiang 830011 China School of Environmental Studies China University of Geosciences 388 Lumo Road Hongshan Administrative District Wuhan Hubei 430074 China Hubei Key Laboratory of Wetland Evolution ＆ Eco-Restoration 388 Lumo Road Hongshan Administrative District Wuhan Hubei 430074 China

This study has focused on the processes of soil degradation and chemical element concentration in tea-growing regions of Rwanda,*** degradation accelerated by erosion is caused not only by topography but also by human *** soil degradation involves both the physical loss and reduction in the amount of topsoil associated with nutrient *** samples were collected from eleven tropical zones in Rwanda and from variable depth within each collecting *** these,Samples from three locations in each zone were analyzed in the laboratory,with the result that the pH of all soil samples is shown to be less than 5（pH〈5） with a general average of *** elements such as iron（Fe）, copper（Cu）,manganese（Mn）,and zinc（Zn） are present in high concentration *** contrast calcium （Ca） and sodium（Na） are present at low-level concentrations and carbon（C） was found in minimal *** addition,elements derived from fertilizers,such as nitrogen（N）,phosphorous（P）,and potassium（K） which is also from minerals such as feldspar,are also present in low-level concentrations. The results indicate that the soil in certain Rwandan tea plantations is acidic and that this level of pH may help explain,in addition to natural factors,the deficiency of some elements such as Ca,Mg,P and *** use of chemical fertilizers,land use system and the location of fields relative to household plots are also considered to help explain why tea plantation soils are typically degraded.

关键词： Chemical elements Fertilizer use pH Soil degradation Tea plantations

Optimum Sizing and Siting of an Embedded Solar Photovoltaic Generation: A Case Study of 33 kv Sub-Transmission Network at Tarkwa, Ghana

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Journal of Power and Energy Engineering 2021年第3期9卷 1-24页

作者： Armstrong Okai Ababio gabriel Takyi emmanuel Kwaku Anto Energy Consulting and Telco Business Directorate Electricity Company of Ghana Ltd. Accra Ghana Department of Mechanical Engineering Kwame Nkrumah University of Science and Technology Kumasi Ghana Department of Electrical & Electronic Engineering Kwame Nkrumah University of Science and Technology Kumasi Ghana

The interconnection of Solar PV to the Tarkwa Bulk Supply Point (BSP) has become necessary in order to provide additional capacity to meet the ever-increasing demand of Tarkwa and its environs during the day. The Solar PV Plant will support the Tarkwa BSP during the day. In this study, a grid impact analysis for the integration of Solar PV plant at three points of common coupling (PCC) at Tarkwa Bulk Supply Point’s (BSP) 33 kV network of the Electricity Company of Ghana was carried out. The three PCCs were Tarkwa BSP, Ghana Australia Gold (GAG) Substation and Darmang Substation. Simulations and detailed analysis were carried out with the use of CYME Software (Cyme 8.0 Rev 05). The Solar PV was integrated at varying penetration levels of 9 MWp, 11 MWp, 14 MWp, 16 MWp, 18 MWp, 20 MWp and 23 MWp (representing penetration levels of 40%, 50%, 60%, 70%, 80%, 90% and 100%, respectively) of the 2020 projected light demand of Tarkwa BSP 25.15 MVA network at an average power factor of 0.903. From the study, the optimum capacity of Solar PV power that could be connected is 9 MWp at an optimum inverter power factor of 0.94 lagging, and the GAG Substation was identified as the optimal location. The stiffness ratio at the optimal location was determined as 41.9, a figure which is far greater than the minimum standard value of 5, and gives an indication of very little voltage control problems in the operation of the proposed Solar PV interconnection. The integration of the optimum 9 MW Solar PV Plant to the Tarkwa network represents an additional 12.77% capacity, decreased the technical losses by 7.76%, and increased the voltage profile by 1.97%.

关键词： Grid Integration Embedded Solar PV Sub-Transmission Network Technical Losses

Numerical simulation of roof cavings in several Kuzbass mines using finite-difference continuum damage mechanics approach

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International Journal of Mining Science and Technology 2020年第2期30卷 157-166页

作者： Mikhail Eremin gabriel Esterhuizen Igor Smolin Institute of Strength Physics and Materials Science Siberian BranchRussian Academy of SciencesTomsk 634055Russian Federation National Institute for Occupational Safety and Health PittsburghPA 15236USA National Research Tomsk State University Tomsk 634050Russian Federation

An essential stage of mine design is an estimation of the steps of the first and periodic roof caving in longwall ***,this is carried out using the field experience and can be much enhanced by numerical *** this work,the finite-difference method was applied coupled with the continuum damage mechanics(CDM)approach to simulate the stress-strain evolution of the rock mass with the underground opening during coal *** steps and stages of roof caving were estimated relying on the numerical simulation data,and they were compared with the field data from several operating mines in the south of the Kuznetsk Basin,*** dependence of the first roof caving step in simulation linearly correlates with field *** results correspond to the actual roofs of longwall panels of the flat-dipping coal seams and the average rate of face advancement is approximately 5 m/day.

关键词： Longwall mining Rock mass Underground openings Roof caving Abutment pressure Numerical simulation

Numerical analyses of pillar behavior with variation in yield criterion,dilatancy, rock heterogeneity and length to width ratio

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第1期11卷 46-60页

作者： Sankhaneel Sinha gabriel Walton Colorado School of Mines

With recent advances in numerical modeling, design of underground structures increasingly relies on numerical modeling-based analysis approaches. While modeling tools like the discrete element method(DEM) and the combined finite-discrete element method(FDEM) are useful for investigating small-scale damage processes, continuum models remain the primary practical tool for most field-scale *** results obtained from such models are significantly dependent on the selection of an appropriate yield criterion and dilation angle. Towards improving its capabilities in handling mining-related problems, the authors have previously developed a new yield criterion(called progressive S-shaped criterion). The focus of the current study is to demonstrate its use in modeling rock pillars through a comparative analysis against four other yield criteria. In addition to the progressive S-shaped criterion,only one out of the four other criteria predicted a trend in strength consistent with an empirical pillar strength database compiled from the literature. Given the closely-knit relationship between yield criteria and dilation angle in controlling the overall damage process, a separate comparison was conducted using a mobilized dilation model, a zero degree dilation angle and a constant non-zero dilation angle. This study also investigates the impact of meso-scale heterogeneity in mechanical properties on the overall model response by assigning probability distributions to the input parameters. The comparisons revealed that an isotropic model using a combination of progressive S-shaped criterion and mobilized dilation angle model is sufficient in capturing the behaviors of rock pillars. Subsequently, the pillar model was used to assess the effect of L/W(length/width) ratio on the peak strength.

关键词： Rock pillars Progressive S-shaped criterion Numerical modeling

Recent progress on isospin breaking corrections and their impact on the muon g-2 value

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Chinese Physics C 2010年第6期34卷 712-717页

作者： gabriel López Castro Departamento de Física CinvestavApartado Postal 14-74007000 MxicoD.F Mxico

We describe some recent results on isospin breaking corrections which are of relevance for predictions of the leading order hadronic contribution to the muon anomalous magnetic moment aμ^*** when using τ lepton data. When these corrections are applied to the new combined data on the π^±π^0 spectral function, the prediction for aμ^*** based on τ lepton data gets closer to the one obtained using e^＋e^- data.

关键词： isospin breaking tau decays muon magnetic moment radiative corrections