崩塌体水力输移与塌岸淤床交互影响试验

以二元结构河岸崩塌模式为研究背景,在弯道水槽中展开系列试验,研究凹岸坡脚处成型崩塌体在水力作用下输移过程及其对岸坡稳定性与河床冲淤的交互影响。试验成果表明,崩塌体经水力分解破碎呈块状、片状或颗粒状起动,部分随水流带至凸岸或下游,堆积在坡脚附近的崩塌体残留量随水力作用大小及土体特性不同而变化。崩塌体临水面周围尤其上下游端水流紊动强烈易形成较大剪切力区,临坡面上下游端附近剪切力较无崩塌体时减小;崩塌体体积越大,对剪切力区特征的改变也越明显。崩塌体的存在虽不能制止附近岸坡的再次崩塌,但可能抑制崩岸发展及附近河床淤积的程度,崩塌体的粘性或体积越大,这种抑制作用越显著;相同崩塌体抑制附近河床淤积的程度较抑制岸坡崩塌的程度大。     

粤连电厂拦灰坝土石混合料碾压试验研究

对拦灰坝土石混合料进行3种不同铺填厚度、3种不同加水量、5种振动碾压遍数组合的现场试验,通过测试碾压前后的颗粒组成,沉降量、变形模量、干湿密度等确定1组优化参数作为现场施工控制参数,并对试验结果进行了分析,提出了相应的处理措施和建议。     

Hydrofracture mechanisms in rock during pressure grouting

Summary Hydrofracture Mechanisms in Rock During Pressure Grouting. The paper examines the basic meachnisms controlling the initiation of fractures in rocks and layered soils during pressure grouting, and their subsequent propagation into the ground mass. Previous analyses of fracture initiation have tended to concentrate on simplified models in which the ground is treated as an impervious elastic or Mohr-Coulomb continuum. The present method allows for the porous or fissured nature of the ground by considering the effect of seepage forces induced by the pore pressure gradient. The effect is quantified by use of a parameterN such that the ratio of fluid force used in expanding the injection hole, to that used in forcing fluid through void spaces, isN to (1—N).Analysis of hydrofracture propagation is based on stress analysis of a borehole in an elastic continuum, the propagating fracture zone around the borehole being represented as a non-elastic material governed by the Mohr-Coulomb failure criterion. This is supplemented by an energy approach which equates the energy supplied to the ground from the injection pump, with the energy stored in the ground and the energy necessary to fracture it.

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Zusammenfassung Brucherscheinungen im Fels bei Verprearbeiten. In der Arbeit wird der grundlegende Mechanismus untersucht, welcher bei Verpreßarbeiten in Fels und geschichtetem Boden zur Einleitung und Ausbreitung von Brüchen führt. Frühere Untersuchungen des Bruchbeginns stützten sich im wesentlichen auf vereinfachte Modelle, in denen der Untergrund als undurchlässiges Kontinuum angesehen wird, das entweder elastisch ist oder der Mohr-Coulombschen Bruchbedingung genügt. Die neue Methode berücksichtigt dagegen eine Porosität oder Klüftung des Untergrundes durch Ansatz der vom strömenden Medium auf das Gebirge ausgeübten Belastung. Diese Belastung wird aufgeteilt in einen Druckverlust an der Bohrlochwand (gleich ParameterN mal Verpreßdruck) und die entsprechende, über den gesamten durchströmten Bereich verteilte Belastung.Die Untersuchung der Bruchausbreitung geht von der Spannungsermittlung um ein Bohrloch in einem elastischen Kontinuum aus, wobei in der sich ausbreitenden Bruchzone um das Bohrloch herum nichtelastisches Material angenommen wird, das dem Mohr-Coulombschen Bruchkriterium genügt. Zur Ergänzung dient eine Energie-Betrachtung, bei der die von der Injektionspumpe abgegebene Energie gleichgesetzt wird der im Untergrund gespeicherten Energie und der aufgewendeten Brucharbeit.

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Résumé Les mécanismes de la fracturation hydraulique dans les roches pendant les injections sous pression. Le mémoire examine les mécanismes fondamentaux qui gouvernent l'initiation des ruptures dans les roches et les sols stratifiés, au cours des injections et leur propagation dans les massifs. Les analyses antérieures de l'initiation de la rupture, se sont concentrées sur des modèles simplifiés où l'on considérait la roche comme un milieu élastique et imperméable, ou comme un milieu de Mohr-Coulomb. La présente méthode admet que le massif est poreux ou fissuré, en considérant l'action des forces de percolation engendrées par le gradient de pression interstitielle. Cette action est quantifiée par un paramètreN, tel que le rapport de la force du liquide employée à dilater le forage d'injection, à celle employée pour forcer le coulis à travers les vides soitN/(1—N). L'analyse de la propagation des ruptures se base sur l'analyse des contraintes autour d'un forage dans un milieu élastique, alors que la zone de la rupture qui se propage autour du forage est représentée par un milieu non-élastique admettant le critère de rupture de Mohr-Coulomb. Cette analyse est complétée par une approche énergétique, où l'énergie qui est fournie au massif par la pompe d'injection est égalée à l'énergie emmagasinée dans la roche et à l'énergie de rupture.

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Nomenclature A area of new cracks created per unit volume of time t - E total work done by injection fluid - E _i irrecoverable component of energy - E _{i c} work done in fracturing rock or soil - E _{i l} work done to overcome various frictional forces in grouting system - E _{i p} work done to cause plastic deformation of fractured zone - E _{i s} work done to overcome shear strength of fluid during flow - E _{i v} work done to overcome frictional drag between fluid and rock in soil surfaces during flow - E _r recoverable component of energy - E _{r f} elastic strain energy stored in fluid - E _{r s} elastic strain energy stored in rock or soil - h height of overburden - i j 1, 2, 3 - K ₀ coefficient of horizontal earth pressure - k permeability of ground to grout - L length of cylindrical grout source - n rock or soil porosity - p average fluid pressure between timet and (t + t) - p ₀ injection pressure - R radius of grout front - r radial distance from borehole axis - r ₀ radius of borehole - r ₁ radius of fractured zone - S specific surface area of rock or soil - S _T tensile strength of rock or soil - t time - u grout seepage velocity - V volume of grout injected - v volumetric strain - specific surface energy of rock - bulk density of rock or soil - _{i j} ^e elastic strain increment tensor - _{i j} plastic strain increment tensor - v Poisson's ratio - _{i j} average stress tensor in the ground during timet and (t + t) - _R , _T, _Z radial, tangential and vertical stresses induced by grouting - _r , _t , _z radial, tangential and vertical stress around borehole before grouting - grout shear strength - angle of internal friction of rock or soil With 7 Figures     

某抽水蓄能电站输水系统下平段区围岩渗透薄弱部位探测

对于地下工程围岩渗透薄弱部位的探测是一项具有隐蔽性和复杂性的地质工程。为避免或减少采用单一探测方法可能出现的不确定性,以一抽水蓄能电站为例,并行采用了4种方法对研究区进行了探测：（1）放射性法;（2）高密度电法;（3）天然示踪法;（4）水质分析法。就其原理而言,前2种方法属于应用地球物理范畴,而后2种方法则属于应用地球化学范畴。根据探测成果,认为区内岩体渗透薄弱部位是存在的,而以 射线强度负异常、低电阻、渗漏水点水温及其他水质指标含量比较接近其补给源作为标志。就其形成机制而言,为多场耦合作用的产物;其中,水动力作用、水化学作用及其耦合作用为最活跃的因素。     

Electromagnetic emissions during dilating fracture of a rock

A lot of experiments on electromagnetic emissions (EMEs) have been reported under axial compressive fracture, shear fracture, indentation fracture and stick–slip (friction) in lab and blasting in situ, but there are rare reports on the in-lab experimental work on EMEs during dilating fracture of a rock which is helpful in studying and understanding EMEs related to slow earthquakes and the earthquakes due to volcanic activities and water level changes of reservoirs. Therefore, in the present paper in order to check whether there are detectable EMEs during dilating fracture of a rock in lab, dilating fracture experiments were conducted. The dry cuboid specimens of initially intact granodiorite and limestone were tested inside magnetic field free space (MFFS) at room temperature. We arranged evenly 20 EME antennas whose resonance frequencies range from 2.5 kHz to 540 kHz close to rock specimens. Our experimental results strongly indicate that detectable EMEs could generate during dilating fracture of a rock. They were recorded only associated with some but not all phases of fracture. Their waveforms often took on the trend that a peak arrived at first and then attenuated sharply and followed by a series of low-amplitude oscillations. The electromagnetic (EM) signals after eliminating the effects of EME antennae via deconvolution had the maximum peak-to-peak amplitudes of about 80.0 mV and 40.5 mV for granodiorite and limestone, respectively. Their main spectral components often concentrated in the band of several kHz to ∼60 kHz and of several kHz to ∼280 kHz. The emission of electrons and charged particles from fracture surfaces and/or micro-fracture electrification could be possible mechanisms for our experimental results.     

IP找水与DDJ-1型仪器野外数据采集

用DDJ-1型多功能激电仪对IP法二次场的长延续时段采集,可提高观测数据质量和判断数据采集的可靠性,因而观测到了反映第二层为相对高极化率的三层"K"型极化率曲线.     

斜坡地下水渗透力计算与稳定性分析

分析了基岩山区斜坡区域地下水的渗流模式,指出斜坡堆积体中地下水的一般特征,根据这个特征建立了条分法中斜坡渗透力的简易计算方法,用于改进传统的剩余推力法和Sarma法。该方法不需要额外补充参数,易于工程勘察人员掌握。提出通过极限状态考察斜坡安全储备的思路,对三峡库区某滑坡在水库蓄水前后的稳定性和安全储备进行了评价,结果表明传统方法计算的稳定性系数过高,当库水位快速下降时滑坡稳定性减弱,地下水渗透力是其中不可忽视的影响因素。     

圆形空心钢管混凝土柱的耐火性能实验研究

关于实心钢管混凝土的耐火性能已有大量的实验研究,而空心钢管混凝土的耐火实验目前还非常少见。针对这一不足,对空心钢管混凝土进行了耐火实验研究,其中考虑了不同的空心率,并对中空注水对构件耐火性能的影响也进行了实验研究。实验结果表明：在相同的荷栽比下,构件的耐火时间随空心率先增大后减小。当空心率较小时,中空注水对构件耐火时间的提高作用不明显;当空心率较大时,注水对耐火时间的提高才体现出来。     

深层黏性土变形破坏的影响因素分析

河南刘河煤矿矿二1煤层上为厚度20~40m的第四系覆盖层,其中黏土层平均厚度为6.6m。由于第四系孔隙水含水组的四个含水段均为富水性中等及以上含水层,所以该层黏性土在受到上覆高压影响后能否控制顶板突水显得尤为关键,是解决新生界含水层下的安全开采的关键问题。通过室内实验测得该矿深度约在150m的4个钻孔土样的物理参数和土颗粒级配分析,按实验结果模拟深层黏性土,考虑受力面积、含水率和厚度3个影响黏性土破坏的主要因素,利用正交实验原理安排实验。结果表明,受力面积和含水率越大,黏性土的破坏程度增大;黏性土的厚度越大,破坏程度相应减小;3个因素中,受力面积的影响最大;当黏性土含水率在10%~25%,受力面积越小,厚度越大,黏性土不易发生破坏。该研究对预防和保证矿山安全生产具有重要意义。     

高层建筑荷载引发地面沉降与隆起变形三维数值模拟

针对地下水埋深较浅地区,由高层建筑荷载引起的土体变形问题,以比奥固结理论为基础,结合土体非线性流变理论,将土体本构关系推广到黏弹塑性;同时考虑土体力学参数及水力参数的动态变化关系,建立了高层建筑荷载引发地面沉降与隆起变形的三维有限元数值模型,详细研究了高层建筑荷载影响下的土体变形特征及此过程中土体力学参数及水力学参数的变化特征。结果表明：由高层建筑荷载引起的地面沉降呈现漏斗状,以建筑物中心为漏斗中心,高层建筑荷载施加初期,高层建筑周围出现隆起,到达最大值后隆起逐渐消失;高层建筑底部浅层土体孔隙度、渗透系数及泊松比均呈现缓慢减小趋势,弹性模量呈现缓慢增大趋势;而高层建筑周围浅层土体的孔隙度、渗透系数及泊松比呈现先增大后减小的变化趋势,弹性模量则呈现先减小后增大的变化趋势;高层建筑影响区域浅部土体参数的变化趋势与土体的回弹及压缩有关。