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Application of a transversely isotropic brittle rock mass model in roof support design

International Journal of Mining Science and Technology 2012年第5期22卷 639-643页

作者： David Oliveira coffey geotechnics NSW 2066Australia

Accurate modelling of the potential failure modes in the rock mass is an essential task towards a robust design of roof support systems in coal *** use of generalised rock mass properties based on averaged properties(***-Brown model) has been found to limit the capability to reproduce the actual rock mass behaviour which may include a wide range of interacting and complex failure mechanisms such as shear and tension fracturing of the intact rock and shear and separation of pre-existing discontinuities,including *** studies have also shown that traditional models,such as the Mohr-Coulomb,may not accurately describe the behaviour of the intact rock,particularly for stress induced failures where spalling and slabbing are *** is mainly due to the cohesion and friction components of the shear strength of the intact rock not being mobilised at the same rate with strain-softening of the former component playing an essential role in the post peak *** addition,coal measure rocks are often transversely isotropic,both by way of the preferred orientation of clay particles within the finer grained lithology and by bedding textures and bedding partings,and this is often ignored in computer simulations.A newly developed transversely isotropic brittle rock mass model is applied in the simulation of a hypothetical and simple roadway development.A Cohesion Weakening-Friction Strengthening(CWFS) approach is adopted to describe the intact rock where the mobilisation and strain-softening of the two shear strength components are linked to plastic *** impacts of anisotropy and brittle rock on the development of the excavation disturbed zone or height of softening,as often referred to,are investigated and their implication in the roof support design discussed.

关键词： Transverse isotropy Brittle behaviour Cohesion weakening-friction strengthening Ubiquitous joints

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Determination of pile failure mechanism under pullout test in loose sand

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Journal of Central South University 2015年第4期22卷 1490-1501页

作者： K.Faizi R.Kalatehjari R.Nazir A.S.A.Rashid Department of geotechnics and Transportation Universiti Teknologi Malaysia

Estimating the deformation of soil around the pile contributes to reliable design of structures under pullout force. This work presents the results of a series of small-scale physical modelling tests designed to investigate the uplift resistance of piles with diameter of 5 cm and slenderness ratios of 1, 2, 3 and 4 in loose sand. Close photogrammetric technique and particle image velocimetry(PIV) were employed to observe the failure patterns due to uplift force on piles. The results show that the shear zones curve slightly outward near the ground surface. After peak resistance, the shear strain concentrates into a pair of narrow shear bands,then a flow around mechanism is formed accompanied by a reduction in the uplift resistance. The results from the laboratory tests were verified by analytical method proposed by Chattopadhyay and PLAXIS 2D and 3D finite element method software. It is found that the depth and width of the failure surface increase with the increment of the slenderness ratio. A good agreement is observed among the measured bearing capacity and obtained failure surface of the models and the results of numerical modelling. Finally, the maximum deformation of loose and dense sand respectively with densities of 25% and 75% were compared in the stage of fully removing pile. The results shows that the deformation of the soil is related to its density, therefore it depends on its dilatancy.

关键词： pile uplift sand particle image velocimetry

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Damage detection on framed structures: modal curvature evaluation using Stockwell Transform under seismic excitation

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Earthquake Engineering and Engineering Vibration 2015年第2期14卷 265-274页

作者： R.Ditommaso F.C.Ponzo G.Auletta Department of Structures Geotechnics Engineering Geology University of Basilicata School of Engineering University of Basilicata

The key parameters for damage detection and localization are eigenfrequencies, related equivalent viscous damping factors and mode shapes. The classical approach is based on the evaluation of these structural parameters before and after a seismic event, but by using a modern approach based on time-frequency transformations it is possible to quantify these parameters throughout the ground shaking phase. In particular with the use of the S-Transform, it is possible to follow the temporal evolution of the structural dynamics parameters before, during and after an earthquake. In this paper, a methodology for damage localization on framed structures subjected to strong motion earthquakes is proposed based on monitoring the modal curvature variation in the natural frequency of a structure. Two examples of application are described to illustrate the technique: Computer simulation of the nonlinear response of a model, and several laboratory(shaking table) tests performed at the University of Basilicata(Italy). Damage detected using the proposed approach and damage revealed via visual inspections in the tests are compared.

关键词： damage detection S-transform band-variable fi lter

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Finite element analyses of slope stability problems using non-associated plasticity

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第6期10卷 1091-1101页

作者： Simon Oberhollenzer Franz Tschuchnigg Helmut F.Schweiger Institute of Soil Mechanics Foundation Engineering and Computational Geotechnics Graz University of Technology

In recent years, finite element analyses have increasingly been utilized for slope stability problems. In comparison to limit equilibrium methods, numerical analyses do not require any definition of the failure mechanism a priori and enable the determination of the safety level more accurately. The paper compares the performances of strength reduction finite element analysis(SRFEA) with finite element limit analysis(FELA), whereby the focus is related to non-associated plasticity. Displacement-based finite element analyses using a strength reduction technique suffer from numerical instabilities when using non-associated plasticity, especially when dealing with high friction angles but moderate dilatancy angles. The FELA on the other hand provides rigorous upper and lower bounds of the factor of safety(FoS) but is restricted to associated flow rules. Suggestions to overcome this problem, proposed by Davis(1968), lead to conservative FoSs; therefore, an enhanced procedure has been investigated. When using the modified approach, both the SRFEA and the FELA provide very similar results. Further studies highlight the advantages of using an adaptive mesh refinement to determine FoSs. Additionally, it is shown that the initial stress field does not affect the FoS when using a Mohr-Coulomb failure criterion.

关键词： Finite element limit analysis(FELA) Finite element method Slope stability Strength reduction technique Non-associated plasticity Adaptive mesh refinement Initial stresses

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A comprehensive geomechanical method for the assessment of rockburst hazards in underground mining

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International Journal of Mining Science and Technology 2020年第3期30卷 345-355页

作者： Piotr Malkowski Zbigniew Niedbalski Department of Geomechanics Civil Engineering and GeotechnicsAGH University of Science and Technology30-059 KrakowPoland

Rockburst hazard in mining industry all over the world is one of the most severe hazards. It is becoming increasingly common because of the ever-growing depths of mining operations accompanied by the increasing strength of rocks. One of the most difficult issues is to predict this hazard before the mining operations, whether geophysical investigations have been conducted or not. Polish experience in this field shows that in such cases an effective solution can be the geomechanical method. Therefore, extensive studies on rockburst hazard should focus on three main aspects:(1) rock mass and rock(and coal)predisposition to rockburst–laboratory tests and empirical analyses based on lithology,(2) identification of the potential places with stress and elastic energy concentration in the rock mass within the area planned for exploitation, and(3) the assessment of the impact of mining tremors on the surface. This preliminary geomechanical analysis assesses the propensity of the rock mass to dynamic breakage and provides quantitatively the level of rockburst hazard. The paper presents Polish experience in rockburst hazard assessment with the use of geomechanical method, as well as some solutions and examples of such analyses.

关键词： Hazards in underground mining Rockburst hazard assessment Rock mass propensity to rockburst Rock propensity to rockburst Geomechanical analysis

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Revisiting the theoretical prediction of the explosive performance found by the Trauzl test

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Defence Technology（防务技术） 2024年第6期36卷 163-174页

作者： Ivana Dobrilovic Mario Dobrilovic Muhamed Suceska Faculty of Mining Geology and Petroleum EngineeringDepartment of Mining Engineering and GeotechnicsUniversity of ZagrebPierottijeva 6Zagreb10000Croatia

The Trauzl lead block test allows the determination of the approximate performance of explosives in blasting applications by measuring the volume increase(expansion)that is produced by the detonation of an explosive charge in the cavity of a lead *** this paper,we reconsider the possibility of interpreting the Trauzl test results in terms of detonation parameters or *** detonation parameters used in the analysis are calculated using the thermochemical code EXPLO5,while the hydrocode AUTODYN is used to simulate the effect of explosive charge density and reaction rate on the results of the Trauzl *** increase in the volume of the lead block cavity was found to correlate best with the product of the detonation heat and the root of the volume of detonation *** simulation showed that the density of explosive charge and the rate of explosive decomposition affect the dynamics of the interaction of the detonation product and the lead block,and consequently the lead block cavity volume increase.

关键词： Trauzl lead block test Performance of explosives EXPLO5 AUTODYN Detonation heat

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Biological process of soil improvement in civil engineering:A review

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Journal of Rock Mechanics and Geotechnical Engineering 2016年第5期8卷 767-774页

作者： Murtala Umar Khairul Anuar Kassim Kenny Tiong Ping Chiet Department of geotechnics and Transportation Engineering Faculty of Civil EngineeringUniversiti Teknologi Malaysia

The concept of using biological process in soil improvement which is known as bio-mediated soil improvement technique has shown greater potential in geotechnical engineering applications in terms of performance and environmental sustainability. This paper presents a review on the soil microorganisms responsible for this process, and factors that affect their metabolic activities and geometric compatibility with the soil particle sizes. Two mechanisms of biomineralization, i.e. biologically controlled and biologically induced mineralization, were also discussed. Environmental and other factors that may be encountered in situ during microbially induced calcite precipitation （MICP） and their influences on the process were identified and presented. Improvements in the engineering properties of soil such as strength/stiffness and permeability as evaluated in some studies were explored. Potential applications of the process in geotechnical engineering and the challenges of field application of the process were identified.

关键词： Bio-mediated soil improvement Microorganisms Metabolic activities BiomineralizationUrease activity

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A one-dimensional strain-rate based model for soft structured clays

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Science China(Technological Sciences) 2012年第1期55卷 90-100页

作者： YIN ZhenYu WANG JianHua Center for Marine geotechnics Research Department of Civil Engineering Shanghai Jiao Tong University Shanghai 200240 China

The paper aims to investigate the destructuration effect on the time-dependent behaviour of soft structured *** coupled with destructuration is analysed based on experimental observations.A strain-rate based model is developed to de-scribe the mechanical behaviour for both unstructured and structured clays under one-dimensional *** advantage of the proposed model lies in the determination of model parameters in a straightforward way,which leads to an easy use of the model for practical *** with consolidation,the model is used to simulate oedometer tests at constant rate of strain and long-term creep oedometer tests on two structured *** comparisons between predicted and measured results demonstrate that the proposed model can reasonably describe the effect of destructuration on the time-dependent behaviour of soft structured clay under one-dimensional *** the model is proposed for one-dimensional analysis,it can be a good base for developing a more general 3D model.

关键词： structured clays viscoplasticity consolidation creep strain.rate destructuration

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Influence of loading and heating processes on elastic and geomechanical properties of eclogites and granulites

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第1期10卷 127-137页

作者： Hem Bahadur Motra Sascha Zertani Department of Geosciences Marine and Land Geomechanics and Geotechnics University of Kiel Institut für Geologische Wissenschaften Freie Universitat Berlin

Increased knowledge of the elastic and geomechnical properties of rocks is important for numerous engineering and geoscience applications(e.g. petroleum geoscience, underground waste repositories,geothermal energy, earthquake studies, and hydrocarbon exploration). To assess the effect of pressure and temperature on seismic velocities and their anisotropy, laboratory experiments were conducted on metamorphic rocks. P-(Vp) and S-wave(Vs) velocities were determined on cubic samples of granulites and eclogites with an edge length of 43 mm in a triaxial multianvil apparatus using the ultrasonic pulse emission technique in dependence of changes in pressure and temperature. At successive isotropic pressure states up to 600 MPa and temperatures up to 600 ℃, measurements were performed related to the sample coordinates given by the three principal fabric directions(x, y, z) representing the foliation(xy-plane), the normal to the foliation(z-direction), and the lineation direction(x-direction). Progressive volumetric strain was logged by the discrete piston displacements. Cumulative errors in Vpand Vsare estimated to be <1%. Microcrack closure significantly contributes to the increase in seismic velocities and decrease in anisotropies for pressures up to 200-250 MPa. Characteristic P-wave anisotropies of about 10% are obtained for eclogite and 3-4% in a strongly retrogressed eclogite as well as granulites. The wave velocities were used to calculate the geomechanical properties(e.g. density, Poisson’s ratio, volumetric strain, and elastic moduli) at different pressure and temperature conditions. These results contribute to the reliable estimate of geomechanical properties of rocks.

关键词： Anisotropy Elastic wave velocities Dynamic elastic moduli Geomechanical rock properties Microcrack

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The quantity of sand fraction sediment in reservoirs as the basis of an assessment of the bedload transport from a reservoir catchment

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International Journal of Sediment Research 2018年第4期33卷 385-394页

作者： Szczepan Ludwik Dabkowski Lukasz Bak Department of Water Quality Institute of Technology and Life Sciences Department of geotechnics Geomatics and Waste Management Kielce University of Technology

A knowledge of the quantity of the sand fraction in the sediments deposited in reservoirs makes it easier to determine the bedload transport, which is a rarely measured parameter. The current study discusses the results of investigations into the siltation and physical properties of sediment in two small reservoirs located in the southeastern part of Poland. Also, the quantity of the bedload sand fraction was *** estimation of the reservoir capacity loss after t years of operation was based on hydroacoustic measurements. The sediment density, organic matter content, and granulometric composition were evaluated by means of investigations and analyses of bottom sediment core samples. The interpolation of the parameters describing the sediment properties was done using the Kriging method. The analyses indicate that 10.80 thousand m3of sediment were deposited into the Zalew Kielecki Reservoir in the years 2004-2015. Their overall mass was 7320 t, of which sand fraction sediments constituted 39.7%.Between the years 2004 and 2014, the Umer Reservoir retained 11.79 thousand m3of sediment having a mass of 7200 t, of which sand fraction constituted 34.6%.

关键词： Reservoir Sedimentation Bottom sediment properties Bedload transport Bathymetry

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