三维裂隙间距对砂浆材料力学特性的影响   总被引：1，自引：0，他引：1  

杨磊  李术才  郭彦双  朱维申  林春金 《岩土力学》2010,31(1):32-38

采用刚性伺服试验机和声发射仪器,研究了预置三维裂隙间距对砂浆材料力学特性的影响,总结了含裂隙试件的破坏过程。综合分析单轴压缩应力-应变曲线和声发射数据可知,含三维裂隙试件的破坏主要由预置裂隙扩展、贯通造成,破坏过程可以分为微裂纹萌生、预置裂隙起裂、扩展、贯通几个基本阶段,试件最终破坏型式为单斜面剪切破坏。裂隙间距d与椭圆形裂隙长轴2c之比(d/2c)在0～1范围内,随着d/2c值增大,试件起裂应力σi和峰值强度σp有降低的趋势。当d/2c值从1/3增至2/3时,σi和σp发生突降,可见此范围为影响强度的敏感区间。d/2c值为1的试件σi和σp最低,相对完整(无预置裂隙)试件分别降低了22.48%和18.60%。裂隙间距不同的试件σi和σp之比变化范围为83.1%～78.9%,且随d/2c值增大,σi/σp有下降趋势。可见裂隙间距越大,从起裂应力到峰值应力的承载空间越大,这对工程实践有一定参考价值。  相似文献   

基于数值流形法的重力坝多裂纹扩展研究     

徐栋栋  杨永涛  郑宏  邬爱清 《岩土力学》2016,37(12):3598-3607

传统数值流形法（NMM）在处理非连续变形问题时,仅限于几何构型不发生破坏的情况。针对这一不足,通过在裂纹尖端附近的物理片上增加用于模拟应力奇异性的增强位移函数,进一步发展了可用于几何构型破坏的扩展的高阶NMM。然后,将其应用到重力坝由连续到非连续的破坏过程分析中。首先,针对一含单裂纹的重力坝模型进行了敏感性分析,结果表明,在不同的扩展长度或网格密度下,其扩展路径基本相同且与文献结果保持一致。进而在此模型基础上又开展了多裂纹扩展分析,结果仅一条主导裂纹发生扩展,与文献结果基本一致。最后,针对印度的Koyna重力坝,通过设置不同的漫顶高度研究了其裂纹扩展路径的变化。结果表明,随着漫顶高度的增大,裂纹扩展路径逐渐趋向于水平方向扩展,而且坝体抵抗破坏的能力逐渐减弱。总体表明,NMM在求解实际工程问题时具有很好的数值稳定性和鲁棒性。  相似文献   

A model of foreshock occurrence   总被引：2，自引：0，他引：2  

T. Yamashita  L. Knopoff 《Geophysical Journal International》1989,96(3):389-399

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Interpretation of tectonic versus magmatic processes for resetting apatite fission track ages in the Niğde Massif, Turkey     

Annia K. Fayon  Donna L. Whitney 《Tectonophysics》2007,434(1-4):1-13

A network of 10 OBS operating in continuous recording mode was deployed in June 2003 in the Galicia passive Margin, surrounding the sinking zone of the ‘Prestige’ oil tanker. The OBSs recorded very different signals, including air-gun shots, seismic events, whale vocalizations or noise associated to ships, as well as two sets of atypical seismic signals that are the object of this contribution and can be described as harmonic tremors and short-duration events. Harmonic tremors appear in most sites as intense monochromatic signals lasting for up to 4 h, with coherent polarization and a wide range of amplitudes. Even if they may be recorded at different sites within a time interval, their envelopes are not correlated, suggesting a source origin at the vicinity of each receiver. A time periodicity close to 6 h is observed, suggesting a correlation with the tidal variation. Most OBSs show also a large number of impulsive events of short-duration, between 1 and 2 s, a very regular decrease of amplitude in the signal coda and characteristic frequency spectrum with one or two narrow peaks. As for the tremors, those events are detected only in individual sites, suggesting very local source zones. We favor the interpretation of both seismic features as coming from the resonance of fluid-filled cracks induced by impulsive pressure transients, in agreement with the theoretical model of Chouet [Chouet, B. 1988. Resonance of a fluid-driven crack: radiation properties and implications for the source of long-period events and harmonic tremor. J. Geophys. Res., 93, 4375–4400.]. The observed harmonic tremors would be the result of sustained pressure fluctuations, probably related to the stress variations induced by the tidal change of the oceanic load, while the short duration events are interpreted as the impulse response to the tremor-generating system.  相似文献   

Space and time variations of crustal anisotropy during the 1997 Umbria–Marche, central Italy, seismic sequence     

D. Piccinini  L. Margheriti  L. Chiaraluce  M. Cocco 《Geophysical Journal International》2006,167(3):1482-1490

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Effect of the development of notches and tension cracks on instability of limestone coastal cliffs in the Ryukyus, Japan   总被引：1，自引：0，他引：1  

Tetsuya Kogure  Hisashi Aoki  Akira Maekado  Takashi Hirose  Yukinori Matsukura 《Geomorphology》2006,80(3-4):236-244

Notches cut by waves are currently developing at the base of vertical coastal limestone cliffs in Okinawa, Japan. The cliff height varies from 3.0–22.1 m, and the maximum notch depth is 8.8 m. Many rectangular or cubic blocks, which appear to have originated from cliff failures, are found on platforms in front of the cliffs. On the flat top surface of the cliff, tension cracks often run parallel to the cliff face. The vertical face of the cliffs displays small undulations but no sliding striation, suggesting that cliff failures have been caused by toppling rather than by shearing or sliding. We use slope stability analysis to determine the critical condition for toppling failure. Physical and mechanical properties of the cliff material were first obtained from laboratory tests. The results indicate that the strength of limestone shows a scale effect, such that the strength decreases with increasing size of the test specimens. Based on this result, we estimated the strength of a rock mass corresponding to the size of the coastal cliff. Cliff stability was then analyzed using a cantilever beam model. Comparison of the stability analysis and the dimension of fallen blocks indicates that toppling failure is strongly associated with the development of notches and tension cracks.  相似文献   

程潮铁矿地下开采引起岩层移动机制初探     

程关文  陈从新  沈强 《岩土力学》2014,35(5):1421-1429

在对矿区地质条件、采矿情况以及监测资料分析的基础上,提出了悬臂梁的力学模型。该悬臂梁是由NWW向节理切割下盘的花岗岩岩体而产生。地下采矿引起的岩层移动分为两个阶段,筒状破坏延伸到地表之前为第1阶段;筒状破坏延伸到地表后,则进入第2阶段。筒状破坏延伸到地表使水平构造应力释放,悬臂梁受力发生变化,而发生弯曲折裂变形和破坏,从而形成了深部岩体破坏的4个区:破裂岩体区、破裂过渡带、变形区和未扰动岩体区。通过对矿区地表测点所测数据进行分析,结合上述岩层移动机制和裂缝产生过程,将变形区域划分为:变形累积区、裂缝产生区、裂缝扩展区和裂缝闭合区。随着采矿的进行,深部岩体4区将逐渐向下延伸,地表4区将逐渐向外扩展。  相似文献   

单轴压缩条件下含三叉裂隙类岩石试样力学特性的细观研究     

李露露  高永涛  周喻  金爱兵 《岩土力学》2018,39(10):3668-3676

三叉裂隙是自然界普遍存在的一种岩体缺陷形式,其对岩体的力学特性有重要影响。对含预制三叉裂隙的水泥砂浆试样进行室内单轴压缩试验,配合使用摄像机拍摄裂纹的起裂、扩展、贯通过程,通过数字图像技术处理获取试样的应变场云图,并结合PFC2D程序研究不同?、? 条件下试样的强度特征、裂纹模式和裂纹演化扩展规律。研究表明：三叉裂隙对试样单轴抗压强度有明显的削弱作用。当? 恒定为120°时,试样在? = 30°时达到最大抗压强度;当? 恒定为90°时,随?增大,试样抗压强度呈先减小后增大的趋势,且当? = 45°时达到最大抗压强度。试样产生的裂纹可分为3类,分别是张拉型裂纹(Ⅰ型裂纹)、剪切型裂纹(Ⅱ型裂纹)、混合型裂纹(Ⅲ型裂纹)。这3类裂纹通常从裂隙尖端开始产生,并且Ⅰ型裂纹沿加载方向扩展,通常未扩展至试样边界;Ⅱ型和Ⅲ型裂纹通常与加载方向呈一定角度扩展至试样边界。通过对裂纹的几何形态和组成宏观裂纹的微裂纹成分的分析,得知导致含三叉裂隙试样在单轴压缩条件下失效的是张拉破坏。数字图像技术得到的应变云图表明,当载荷达到一定阶段,裂隙尖端出现应力集中,微破裂开始发育并聚集成微破裂区,微破裂区扩大产生宏观裂纹。通过对主应变和剪应变云图分析,发现导致试样失效的是张拉破坏,剪应变在裂纹扩展过程中的影响较小。  相似文献