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361.
Analysis of rock structure stability in coal mines 总被引:1,自引:0,他引:1
In this paper, the theory of limit point instability is used to analyse the stability of rock structures in coal mines. A general method of analysing stability of rock structures is put forward and a uniform instability condition of rock structures is set up. Some instability phenomena, such as rock bursts in circular roadways, pillars and long walls, and the outburst of coal and gas from circular roadways, are discussed analytically. At a later stage, the critical point of rock structure instability is determined. The influence of relative parameters (such as the mechanical properties of rock, coal, and the geometric sizes) on the stability of the rock structures is carefully analysed. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
362.
The influence of cavern’s span on surrounding rock classification is getting more and more recognition along with large span underground working’s increasingly coming forth. The authors analyse the timbering expense of cavern in jointed rock mass, the radius of plastic loosened zone and the size effect of macroscopical mechanical parameters of rock mass. Based on the complexion of depressing of surrounding rock’s stability due to increment of cavern’s span, the authors pinpoint attaching importance to the influence of cavern’s span on surrounding rock classification; and suggest reckoning the factor of cavern’s span in surrounding rock classification scientifically by studying the size effect of rock mass’s physico-mechanical parameters. 相似文献
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文章通过广西右江百色水利枢纽地下发电厂房进水口与尾水洞高边坡的治理,介绍在此工程中具有特殊性的一些施工方法。该工程地质体为弱风化硅质泥岩夹泥化夹层、强风化含洞穴硅质泥岩石、强风化硅质岩及全强风化辉绿岩,地质条件非常复杂,对坡体的稳定极其不利。根据三维有限元的分析计算和国内有关权威专家的调查研究需施工1500kN、1000kN的锚索方能保证坡体的永久稳定。大吨位的锚索需锚固在强风化岩土体上,锚索设计采用能提高锚固力的防腐型压力分散锚索。通过现场锚索基本试验,其锚固力完全能满足工程需要。为保证进水口总体施工的进度,在施工进水口约30m高的垂直壁上的锚索时,笔者采用了通常施工中较少采用的垂直壁悬吊式施工法,满足了水电站的整体施工进度和要求。 相似文献
367.
L. G. Tham H. Liu C. A. Tang P. K. K. Lee Y. Tsui 《Rock Mechanics and Rock Engineering》2005,38(1):1-19
Summary To understand the failure mechanism of quasi-brittle materials like rock under tensile stress, observations on the failure process of granite and marble plate specimens under tension are summarized and presented. Micro- and macro-failure properties of rock plates under uniaxial tension have been characterized by using an acoustic emission technique. Acoustic emission signals associated with micro-fractures are captured to locate the sources. An algorithm based on arrival time difference is developed for this purpose. The results reveal clearly the failure processes of rock which include initiation, nucleation and propagation of micro-fractures when the axial stress is close to the peak strength of rock. It is believed that the difference in heterogeneity between granite and marble specimens leads to different fracture shapes and different behaviors of associated acoustic emissions. Numerical simulation of acoustic emissions for two-dimensional tensile test is also carried out. The simulated characteristics are in good agreement with the experimental results. 相似文献
368.
This paper presents a novel dynamical model to analyze the long‐term response of a percussive drilling system. This departs from existing approaches that usually consider a single activation and bit/rock interaction cycle for the analysis of the process performance. The proposed model integrates the axial dynamics of an elastic piston and an elastic drill bit, a motion‐dependent pressure law to drive the piston, and a generalized bit/rock interaction law representative of the dynamic indentation taking place at the bit/rock interface. It applies to down‐the‐hole percussive drilling as well as top‐hole, with minor modifications. The model does not account for the angular motion or the hole cleaning, however. The model is first formulated mathematically; then, a finite‐dimensional approximation is proposed for computations. Numerical analyses of the model response, for a low‐size down‐the‐hole percussive system, follow. The period‐1 stationary response for the reference configuration is studied in detail, and parametric analyses assessing the influence on the rate of penetration of the bit/rock interaction parameters, the feed force, and the percussive activation parameters are conducted. These analyses reveal that the multiscale nature of the process is well captured by the model and recover expected trends for the influence of the parameters. They also suggest that a significant increase of the penetration rate can be achieved by increasing the percussive frequency. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
369.
The microstructure of rock was numerically reproduced by a polygonal grain‐based model, and its mechanical behavior was examined by performing the uniaxial compression test and Brazilian tests via the Universal Distinct Element Code. The numerical results of the model demonstrated good agreement with the experimental results obtained with rock specimens in terms of the stress–strain behavior, strength characteristics, and brittle fracture phenomenon. An encouraging result is that the grain‐based model‐Universal Distinct Element Code model can reproduce a low ratio of tensile to compressive strength of 1/20 to 1/10 without the need for an additional process. This finding is ascribed to the fact that the geometrical features of polygons can effectively capture the effects of angularity, finite rotation, and interlocking of grains that exist in reality. A numerical methodology to monitor the evolution of micro‐cracks was developed, which enabled us to examine the progressive process of the failure and distinguish the contribution of tensile cracking to the process from that of shear cracking. From the observations of the micro‐cracking process in reference to the stress–strain relation, crack initiation stress, and crack damage stress, it can be concluded that the failure process of the model closely resembles the microscopic observations of rock. We also carried out a parametric study to examine the relationships between the microscopic properties and the macroscopic behavior of the model. Depending on the micro‐properties, the model exhibited a variety of responses to the external load in terms of the strength and deformation characteristics, the evolution of micro‐cracks, and the post‐peak behavior. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
370.
Including spatial distribution in a data‐driven rainfall‐runoff model to improve reservoir inflow forecasting in Taiwan
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Multi‐step ahead inflow forecasting has a critical role to play in reservoir operation and management in Taiwan during typhoons as statutory legislation requires a minimum of 3‐h warning to be issued before any reservoir releases are made. However, the complex spatial and temporal heterogeneity of typhoon rainfall, coupled with a remote and mountainous physiographic context, makes the development of real‐time rainfall‐runoff models that can accurately predict reservoir inflow several hours ahead of time challenging. Consequently, there is an urgent, operational requirement for models that can enhance reservoir inflow prediction at forecast horizons of more than 3 h. In this paper, we develop a novel semi‐distributed, data‐driven, rainfall‐runoff model for the Shihmen catchment, north Taiwan. A suite of Adaptive Network‐based Fuzzy Inference System solutions is created using various combinations of autoregressive, spatially lumped radar and point‐based rain gauge predictors. Different levels of spatially aggregated radar‐derived rainfall data are used to generate 4, 8 and 12 sub‐catchment input drivers. In general, the semi‐distributed radar rainfall models outperform their less complex counterparts in predictions of reservoir inflow at lead times greater than 3 h. Performance is found to be optimal when spatial aggregation is restricted to four sub‐catchments, with up to 30% improvements in the performance over lumped and point‐based models being evident at 5‐h lead times. The potential benefits of applying semi‐distributed, data‐driven models in reservoir inflow modelling specifically, and hydrological modelling more generally, are thus demonstrated. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献