An extended displacement discontinuity method for analysis of stress wave propagation in viscoelastic rock mass

An extended displacement discontinuity method (EDDM) is proposed to analyze the stress wave propagation in jointed viscoelastic rock mass (VRM).The discontinuities in a rock mass are divided into two groups.The primary group with an average geometrical size larger than or in the same order of magnitude of wavelength of a concerned stress wave is defined as "macro-joints",while the secondary group with a high density and relatively small geometrical size compared to the wavelength is known as "micro-defects"...     

强夯置换深度的估算

强夯置换加固效果指标中 ,置换深度是一个关键性课题 ,难以预测 ,也难以控制。本文首次以波能传播理论为基础 ,考虑土对波的吸收系数和实际施工情况 ,对强夯置换加固效果中的最终置换深度和随夯击击数变化的置换深度增量进行了预测 ,8个工程实例表明此方法简便实用 ,理论基础可靠 ,可直接为工程实践服务。     

红岭井田煤岩层对比分析

通过对红岭井田内含煤地层特征的研究与分析,采用煤岩层组合特征、煤层、标志层及层间距、物性特征和煤质特征等多种手段对区内煤岩层进行对比,可以准确地判定地层层位和确定煤层,更好地指导和服务于生产。     

Estimation of seismic active earth pressure on reinforced retaining wall using lower bound limit analysis and modified pseudo-dynamic method

Present study estimates seismic active earth pressure on the reinforced retaining wall by combining the lower bound finite element limit analysis and the modified Pseudo-dynamic method. A series of parametric analyses are performed by varying seismic acceleration coefficient, time period of seismic loading, soil friction and dilation angles, reinforcement spacing, length of reinforcement, soil-reinforcement interface, damping ratio of soil, soil-wall interface, wall inclination, and ground inclination. Maximum active earth pressure is exerted when natural time period of reinforced soil matches with the time period of an earthquake. Reinforcement is found to be effective in terms of reducing active earth pressure significantly on the wall subjected to seismic loading. Effectiveness of reinforcement depends upon two factors, namely vertical spacing and soil-reinforcement interface friction angle. For relatively smaller reinforcement spacing, soil-reinforcement behaves like a composite block, which helps to constraint stresses within a small area behind the wall. Maximum tensile resistance is developed when fully rough interface condition is assumed between soil and reinforcement layer. Failure patterns are provided to understand the behaviour of reinforced retaining wall under different time of seismic loading.     

Vulnerability analysis of large concrete dams using the continuum strong discontinuity approach and neural networks

Probabilistic analysis is an emerging field of structural engineering which is very significant in structures of great importance like dams, nuclear reactors etc. In this work a Neural Networks (NN) based Monte Carlo Simulation (MCS) procedure is proposed for the vulnerability analysis of large concrete dams, in conjunction with a non-linear finite element analysis for the prediction of the bearing capacity of the Dam using the Continuum Strong Discontinuity Approach. The use of NN was motivated by the approximate concepts inherent in vulnerability analysis and the time consuming repeated analyses required for MCS. The Rprop algorithm is implemented for training the NN utilizing available information generated from selected non-linear analyses. The trained NN is then used in the context of a MCS procedure to compute the peak load of the structure due to different sets of basic random variables leading to close prediction of the probability of failure. This way it is made possible to obtain rigorous estimates of the probability of failure and the fragility curves for the Scalere (Italy) dam for various predefined damage levels and various flood scenarios. The uncertain properties (modeled as random variables) considered, for both test examples, are the Young’s modulus, the Poisson’s ratio, the tensile strength and the specific fracture energy of the concrete.     

Estimation of bearing capacity of basalts at the Atasu dam site,Turkey

This paper describes the results of the engineering geological investigations and bearing capacity studies carried out at the proposed site of the rock fill Atasu Dam, to be constructed on basalts and pyroclastics. Rock mass strength and modulus of elasticity of the rock mass were determined using the Hoek–Brown empirical strength criterion. Rock mass classifications for the dam rock foundation were undertaken following the RMR, Q and GSI systems and the stress distributions using the finite element technique. To estimate the bearing capacity of the basalts, different empirical equations were used and compared.      

Estimation of the surface displacement field due to construction of Cairo Metro Line El Khalafawy - St. Therese

During the design stage of the Line 2 of the Greater Cairo Metro Project, a numerical study was carried out at the University of Alberta, Canada, in order to related the expected ground movement due to the tunnel construction to the ground control measures imposed during the construction process. A finite element analysis is carried out at the part of the line from Khalafawy to Saint-Therese Station. The study is based on the available documentary related to the ground conditions at the site and to the details of the construction method. The three-dimensional numerical model is constructed to emulate the most probable working conditions taking into account the excavation sequence. A non-linear stress-strain constitutive model is adopted to represent the ground surrounding the tunnel. The results are presented in term of the maximum displacement at the ground surface and the slope of the displacement trough.     

Measurement and analysis of rock mass discontinuity spacing and frequency in part of the Fimiston Open Pit operation in Kalgoorlie, Western Australia: a case study

The Fimiston Open Pit is located in the Eastern Goldfields of Western Australia and is mining an area traditionally known as the Golden Mile. The geological succession in part consists of a 3000–4000 m thick sequence of ultramafic to mafic volcanic rocks and mafic sills, including the Golden Mile Dolerite and the Paringa Basalt into which 650 m high pit slopes will ultimately be excavated. A total of 349 m of scanline were mapped (770 discontinuity measurements), 1022 m of core logged (a further 1795 discontinuity measurements) and a detailed analysis of discontinuity spacing and frequency were undertaken.The total discontinuity spacing values for the study area clearly follow the shape of the exponential distribution, which is consistent with many previous workers’ results. Although not as clearly defined, the normal set spacing values also appear to follow the exponential distribution. The total average calculation for rock quality designation (RQD*) in this study is within 5% of the total average estimate for RQD. This confirms that the method proposed by Priest and Hudson (Int J Rock Mech Min Sci & Geomech Abstr 13 (1976) 135) provides a valuable tool that would be particularly beneficial for geotechnical investigations where diamond core is not readily available.Discontinuity spacing results are complicated by the influence of quartz veining and foliation planes. The veins appear to have influenced the scanline mapping data to a greater extent than the core logging data, while the foliation appears to have influenced the core logging data to a greater degree.     

置换通风式空调房间内速度场和温度场数值模拟

应用计算流体力学的理论和方法模拟了三维空调房间的空气的湍流流动,研究强迫对流作用下的置换通风式空调室内气流的速度和温度分布及换热规律,并利用CFD软件FLUENT对模型进行具体的计算,得出了一些有益的结论。     

Geomechanical behaviour of laminated, weak coal mine roof strata and the implications for a ground reinforcement strategy

This paper describes a component of the results from an ARC-SPIRT funded collaborative research project between UNSW, Powercoal Pty Ltd. and Springvale Coal Pty Ltd. The research project was aimed at identifying strategies for appropriate ground control in particularly weak and soft roof strata in underground coal mining. A field investigation was undertaken at Angus Place Colliery in the Western Coalfield of New South Wales. The investigation incorporated a range of geotechnical instrumentation and was conducted over a period of time from the development face until the site was lost into the goaf of a retreating longwall panel. This paper describes the outcomes from the field investigation, together with a selection of supporting laboratory studies. The paper also presents a number of alternative presentation modes for extensometry data. The results clearly demonstrate the time and face-proximity related influences on roof integrity, and particularly demonstrated the distribution of deformation, bed separation and strata failure into the roof and across the full span of the roadway, together with reflection of this behaviour within the fully encapsulated roof bolt reinforcement system installed.     

Three-dimensional stability analysis of seismically induced landslides using the displacement-based rigorous limit equilibrium method

Bulletin of Engineering Geology and the Environment - Previously, the stability analysis of seismically induced landslides was investigated by the factor of safety of the entire sliding body, which...     

山西省沁水煤田固县井田主要可采煤层及煤质特征分析

以大量钻孔成果数据为基础,通过钻探取芯、数字测井等手段对井田范围内主要可采的3号、15号煤层在横向平面上的厚度变化规律进行了分析研究,并利用煤质化验数据及测井曲线相对比的方式对15号煤层在垂向上的煤质特征变化规律进行了研究,结果表明:3号煤层全区稳定可采,为低灰、特低硫、高发热量之无烟煤,15号煤层全区稳定可采,为低灰、高硫、高发热量之无烟煤。     

可控源微波场促进煤体中甲烷解吸的试验研究

 针对煤层瓦斯抽采过程中吸附瓦斯难以解吸的技术难题,提出可控源微波场促进煤层瓦斯解吸的新思路,采用可控源微波场作用下煤岩瓦斯解吸试验装置,研究有、无可控源微波场作用下煤体中甲烷的解吸规律,探讨可控源微波场对煤体中甲烷解吸特性的影响机理。研究结果表明,可控源微波场能够促进煤体中甲烷的解吸,使煤体的甲烷解吸速率增大且解吸后期衰减变慢、累计甲烷解吸量增加1.65～3.79倍;有、无可控源微波场作用下煤体的甲烷解吸动力学曲线形态基本一致,且能用动扩散系数模型较好地描述;相同解吸时间条件下,可控源微波场作用下煤体的甲烷扩散系数比无微波场作用时大。可控源微波场对煤体中甲烷解吸特性的影响机理主要在于可控源微波场能够增强煤体中甲烷分子的活性、提高煤体的甲烷扩散系数、改变甲烷解吸过程中煤体的扩散阻力级差,使煤体中甲烷的解吸速度增加、扩散速度加快、扩散阻力减小,从而有利于促进煤体中甲烷的解吸。     

Undrained stability of a spherical cavity in cohesive soils using finite element limit analysis

A parametric study of undrained stability of a spherical cavity in clays is investigated by finite element limit analysis with an axisymmetric condition.Influences of cover depth ratio of cavity and dimensionless overburden factor on predicted failure mechanisms and dimensionless load factor are examined.It is found that a previously recommended and up-to-date lower bound solution to the problem was significantly inaccurate for practice use.Thus,an accurate approximate solution to the problem is proposed from nonlinear regression analysis of the computed average bound solutions.New cavity stability factors for the soil cohesion and soil unit weight are proposed.New findings are revealed for the threedimensional effect of the cavity shape on these factors between the axisymmetric and plane strain conditions,and their applications to the undrained stability evaluation of cavity problems in practice are described.     

Assessment of thermal environment using a thermal manikin in a field environment chamber served by displacement ventilation system

This paper presents a thermal comfort study using a thermal manikin in a field environment chamber served by the Displacement Ventilation (DV) system. The manikin has a female body with 26 individually heated and controlled body segments. The manikin together with subjects was exposed to 3 levels of vertical air temperature gradients, nominally 1, 3 & 5 K/m, between 0.1 and 1.1 m heights at 3 room air temperatures of 20, 23 and 26 °C at 0.6 m height. Relative humidity at 0.6 m height and air velocity near the manikin and the subjects were maintained at 50% and less than 0.2 m/s, respectively. The aims of this study are to assess thermally non-uniform environment served by DV system using the manikin and correlate the subjective responses with measurements from the manikin. The main findings indicate that room air temperature had greater influence on overall and local thermal sensations and comfort than temperature gradient. Local thermal discomfort decreased with increase of room air temperature at overall thermally neutral state. The local discomfort was affected by overall thermal sensation and was lower at overall thermally neutral state than at overall cold and cool sensations.     

Predicting roof displacement of roadways in underground coal mines using adaptive neuro-fuzzy inference system optimized by various physics-based optimization algorithms

Due to the rapid industrialization and the development of the economy in each country, the demand for energy is increasing rapidly. The coal mines have to pace up the mining operations with large production to meet the energy demand. This requirement has led underground coal mines to go deeper with more difficult conditions, especially the mining hazards, such as large deformations, rockburst, coal burst, roof collapse, to name a few. Therefore, this study aims at investigating and predicting the stability of the roadways in underground coal mines exploited by longwall mining method, using various novel intelligent techniques based on physics-based optimization algorithms (i.e. multi-verse optimizer (MVO), equilibrium optimizer (EO), simulated annealing (SA), and Henry gas solubility optimization (HGSO)) and adaptive neuro-fuzzy inference system (ANFIS), named as MVO-ANFIS, EO-ANFIS, SA-ANFIS and HGSO-ANFIS models. Accordingly, 162 roof displacement events were investigated based on the characteristics of surrounding rocks, such as cohesion, Young's modulus, density, shear strength, angle of internal friction, uniaxial compressive strength, quench durability index, rock mass rating, and tensile strength. The MVO-ANFIS, EO-ANFIS, SA-ANFIS and HGSO-ANFIS models were then developed and evaluated based on this dataset for predicting roof displacements in roadways of underground mines. The results indicated that the proposed intelligent techniques could accurately predict the roof displacements in roadways of underground mines with an accuracy in the range of 83%–92%. Remarkably, the SA-ANFIS model yielded the most dominant accuracy (i.e. 92%). Based on the accurate predictions from the proposed techniques, the reinforced solutions can be timely suggested to ensure the stability of roadways during exploiting coal, especially in the underground coal mines exploited by the longwall mining.     

A parametric study of the free vibration analysis of rotating laminated cylindrical shells using the method of discrete singular convolution

This paper deals with the free vibration analysis of rotating laminated cylindrical shells. The analysis uses discrete singular convolution (DSC) technique to determine frequencies. Regularized Shannon's delta (RSD) kernel is selected as singular convolution to illustrate the present algorithm. The formulations are based on the Love's first approximation shell theory, and include the effects of initial hoop tension and centrifugal and coriolis accelerations due to rotation. The spatial derivatives in both the governing equations and the boundary conditions are discretized by the DSC method. Frequency parameters are obtained for different types of boundary conditions, rotating velocity and geometric parameters. The effect of the circumferential node number on the vibrational behaviour of the shell is also analysed. The analysis has been verified by comparing results with those in the literature and sufficient agreement is obtained.     

关于火电厂输煤通廊供暖热媒参数限值的讨论

以若干权威性文献的数据论证了现行规范对具有煤尘作业和防火要求的建筑所规定的供暖热煤温度限值的正确性，介绍了某些国家在热媒温度超限时所采取的措施－无（防）尘散热器。     

Two-dimensional stability analysis of a soil slope using the finite element method and the limit equilibrium principle

A slope stability analysis method using the finite element method and the limit equilibrium principle is presented in this paper to determine the critical slip surface and to calculate the minimum safety factor based on the stress field produced by a numerical simulation. This method assumes a cutting export and makes good use of geometric combination to reduce the search range during the calculation process. The proposed method was validated using two classical benchmark slopes and an engineering slope; it was also compared with other conventional limit equilibrium methods. The error between the proposed method and the limit equilibrium method was relatively small. The proposed method resolved several limitations of the traditional methods, and a comparison of the benchmark slopes showed that the proposed method exhibited good accuracy and efficiency. The proposed method can thus analyse both the stability of a natural slope and the stability of a soil slope under seismic loading conditions.