Soft rock pillars     

J. F. Abel Jr. 《Geotechnical and Geological Engineering》1988,6(3):215-248

Summary Soft rock pillars can be designed by several methods available in the mining literature. All of these methods include the effect of shape, or geometry, on the average strength of specimens and pillars. All of the pillar design methods include some measurement of the strength of specimens of the pillar rock. The most common rock specimen strength property measured is the unconfined compressive strength. However, the average strength of triaxially confined rock specimens is much greater than the unconfined specimen strength, which can be more important to pillar strength. The estimation of the strength of a pillar is complicated by the decrease in rock specimen strength with increase in specimen size.Editor's note: In common with North American engineering practise, the paper uses English units throughout, where feasible conversions are included in the text. Where not, the following factors may be used: 1 inch=25.4 mm; 1 ft=0.3048 m; 1 lbf/in.^–2=6.895 kn/m^–2; 1Tonf.=8.896 kN.  相似文献   

Influence of longwall support on the occurrence of roof cavities     

A. Vervoort 《Geotechnical and Geological Engineering》1988,6(4):313-326

Summary The forming of roof cavities in longwall faces is a complicated process. A likely explanation for this process is the presence of relaxed zones in the first beds of the roof above and ahead of the support. If existing or potential fissures are allowed to open through insufficient constraint, the block of roof delimited by these fissures will collapse. An increasing unsupported distance, an increasing distance between the face and the first row of legs, a lower vertical bearing force and a lower support pressure on the roof will increase the extent of the relaxed zones. These effects are investigated through underground observations and numerical modelling.Supplementary to this local influence, there is also a spatial relation between the support characteristics of one element in one coal step and the occurrence of fall outs in the roof uncovered by the next coal steps (3 on average) and above the neighbourhood elements (2 to 4 on average). It is probable that, once a cavity is formed, it is extended easily (in the two directions), until appropriate measures are taken.  相似文献   

Support and strata interaction at coal faces     

Ke-Bin Zhang 《Geotechnical and Geological Engineering》1988,6(1):85-88

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The fractal geometry of flow paths in natural fractures in rock and the approach to percolation   总被引：2，自引：0，他引：2  

D. D. Nolte  L. J. Pyrak-Nolte  N. G. W. Cook 《Pure and Applied Geophysics》1989,131(1-2):111-138

The distributions of contact areas in single, natural fractures in quartz monzonite (Stripa granite) are found to have fractal dimensions which decrease fromD=2.00 to values nearD=1.96 as stress normal to the fractures is increased from 3 MPa up to 85 MPa. The effect of stress on fluid flow is studied in the same samples. Fluid transport through a fracture depends on two properties of the fracture void space geometry. the void aperture; and the tortuosity of the flow paths, determined through the distribution of contact area. Each of these quantities change under stress and contribute to changes observed in the flow rate. A general flow law is presented which separates these different effects. The effects of tortuosity on flow are largely governed by the proximity of the flow path distribution to a percolation threshold. A fractal model of correlated continuum percolation is presented which quantitatively reproduces the flow path geometries. The fractal dimension in this model is fit to the measured fractal dimensions of the flow systems to determine how far the flow systems are above the percolation threshold.  相似文献   

PAN－S光度法测定水和河泥中微量锰     

魏琴  杜斌  马荣 《矿物岩石》1994,(3)

本文研究了ＰＡＮ－Ｓ与锰的显色反应。配合物的最大吸收峰位于５３８ｎｍ波长处，表观摩尔吸光系数为２．９×１０￣４Ｌ·ｍｏｌ￣（－１）·ｃｍ￣（－１），锰量在０─１．６μｇ／ｍｌ范围内符合比尔定律，方法用于水和河泥中微量锰的测定，结果良好。  相似文献   

The frictional behavior of lizardite and antigorite serpentinites: Experiments,constitutive models,and implications for natural faults   总被引：2，自引：0，他引：2  

Linda A. Reinen  John D. Weeks  Terry E. Tullis 《Pure and Applied Geophysics》1994,143(1-3):317-358

Laboratory studies of the frictional behavior of rocks can provide important information about the strength and sliding stability of natural faults. We have conducted friction experiments on antigorite and lizardite serpentinites, rocks common to both continental and oceanic crustal faults. We conducted both velocity-step tests and timed-hold tests on bare surfaces and gouge layers of serpentinite at room temperature. We find that the coefficient of friction of lizardite serpentinite is quite low (0.15–0.35) and could explain the apparent low stresses observed on crustal transform faults, while that of antigorite serpentinite is comparable to other crustal rocks (0.50–0.85). The frictional behavior of both types of serpentinite is well described by a two-mechanism model combining state-variable-dominated behavior at high slip velocities and flow-dominated behavior at low velocities. The two-mechanism model is supported by data from velocity-step tests and timed-hold tests. The low velocity behavior of serpentinite is strongly rate strengthening and should result in stable fault creep on natural faults containing either antigorite or lizardite serpentinite.  相似文献   

冻土切削力学特性的试验和理论分析   总被引：5，自引：2，他引：5  

张招祥  余群 《冰川冻土》1994,(2)

利用笔者所研制的冻土切削试验台，在室内对不同冻土在不同温度、含水量、切削速度、切削深度和切刀前角下进行了一系列切削试验。结果表明，切削时，冻土主要呈脆性断裂破坏，其切削过程被认为是刀刃切入和撕裂冻土的结果，切削阻力随冻土温度降低而非线性增加，随切削速度提高而略有增加，随切削深度增加而近似线性增加，最佳切刀前角随切削深度增大有增大趋势。但平均切削阻力与最大切削阻力之比值对不同试验条件基本在０．４－０．６５间变化。同时，根据切削过程机理，从理论上建立了最大切削力模型，此模型考虑了切入和撕裂冻土阻力。  相似文献   

Flow through anisotropic networks     

L. Rothenburg  A. Bogobowicz 《Stochastic Hydrology and Hydraulics》1990,4(3):175-191

This paper presents an analysis of Hagen-Poiseulle flow through plane random anisotropic networks of interconnected channels. Macroscopic permeability tensor of the network is expressed in terms of statistico-geometrical characteristics like the degree of anisotropy in channel orientations, average co-ordination number of the network and first two moments of channel length distribution. Analytical results are illustrated and verified using numerical analysis of flow in a simulated random network. The emphasis of the paper is on the effects of anisotropy on distributions of flow rates in channels. It is shown that, due to anisotropy the maximum flow rate generally occurs in channels that are not aligned along the direction of the macroscopic pressure gradient.  相似文献   

分层弹性地基场地土地震反应分析     

刘宗贤  李玉亭 《华北地震科学》1994,12(2):1-13

本文对场地土按分层弹性地基土建立了合理的力学模型，通过动力分析，给分层弹性地基场地土水平方向自振特性及在水平方向地震荷载作用下强迫反应的解析解。  相似文献   

卫星轨道力学模型分析   总被引：2，自引：0，他引：2  

周建华 《测绘学院学报》1994,(4)

本文分析了目前卫星定轨中采用的轨道力学模型误差状况。使用Ｌａ－ｇｅｏｓ卫星的全球激光测距资料，利用长短弧定轨比较方法，给出了力学模型误差对此卫星的影响特性，并对所采用的力模型进行定性、定量分析。结果表明，卫星长弧定轨误差源来自于力学背景尚不十分清楚的因素。  相似文献