共查询到17条相似文献，搜索用时 323 毫秒
1.
利用Instron1342型电液伺服材料试验机,采用双扭常位移松弛法对花岗岩试件在空气中及饱和水两种条件下进行了亚临界裂纹扩展试验研究,获得了相应的裂纹扩展速率V与应力强度因子KI的关系（KI -V曲线）及亚临界裂纹扩展参数,讨论了两种环境下裂纹亚临界扩展的规律,并对两种环境下亚临界裂纹扩展参数进行了对比分析。研究表明：采用常位移松弛法所测试的两种条件下的lgKI -lgV关系都有很好的线性规律。在双对数坐标空间中,含饱和水试件的lgKI -lgV曲线位于空气中试件lgKI -lgV曲线的左上角,曲线斜率减小,而截距增加。在同一应力强度因子水平上,含饱和水试件的裂纹扩展速度大,说明水能加速亚临界裂纹扩展,与实际相一致。 相似文献
2.
不同岩性及含水率的岩石声波传播规律试验研究 总被引：2，自引：0，他引：2
利用智能声波仪对红砂岩、大理岩和花岗岩试样在干燥及饱和条件下进行了声波纵波透射试验,研究声波在岩石中传播的速度特征,同时利用傅里叶变换及小波变换研究声波在岩石中传播的波形、波幅衰减规律、波谱特征。结果表明： （1）红砂岩、大理岩和花岗岩在饱和状态下的纵波波速比其在干燥状态下略高。（2）岩石纵波速度受到岩石的致密程度、孔隙度、密度及硬度的影响。（3）在同样的激发信号下,饱水的砂岩、大理岩、花岗岩岩样声波信号能量集中在低频部分较多,而干燥岩样声波信号能量集中在高频部分较多。（4）饱水的3种岩样声波信号能量衰减较快,尾波不发育;干燥的3种岩样声波信号能量衰减较慢,尾波较发育。（5）穿过岩石的声波信号的波速、波形的时域特征、频域特征及时-频域特征能在一定程度上反映出岩石内部的孔隙及微裂隙的发育情况和岩石含水情况等特征。 相似文献
3.
脆性对岩石破裂机制及声发射特性具有重要影响。采用花岗岩及大理岩两种不同岩性的岩石,开展了单轴压缩及声发射测试试验,获取了两种岩石的强度及变形特性,并对其脆性大小进行定量评价,分析了单轴压缩过程中两种岩石声发射能量演化特性,结合声发射b值计算结果及其物理意义,对比了两种岩石破裂机制的差异性。结果表明:(1)试验所采用的两种岩石,花岗岩的σcd/σp之比介于0.676~0.745之间,平均为0.706,而大理岩的σcd/σp之比介于0.439~0.615,平均为0.52;(2)基于脆性评价指标,结合试样宏观破坏现象及形态,本次试验采用的花岗岩其脆性大于大理岩;(3)岩石脆性程度越大,在裂纹不稳定扩展阶段,在产生相同的轴向压缩变形的情况下,环向变形量越大;(4)强脆性的花岗岩在裂纹不稳定扩展阶段持续出现高能级的声发射信号,而弱脆性的大理岩则表现出能量持续降低的变化趋势,峰值强度后,弱脆性的大理岩其高能级能量的声发射信号更活跃;(5)单轴压缩下,与大理岩相比,花岗岩破坏过程中大尺度的破裂事件所占比例较大。 相似文献
4.
高渗压条件下压剪岩石裂纹断裂损伤演化机制研究 总被引：2，自引：1，他引：1
探讨了高渗透压作用下压剪岩石裂纹的起裂规律及分支裂纹尖端应力强度因子的演变规律,建立了高渗压下裂隙岩体发生拉剪破坏的临界水压力值和初裂强度判据,分析了不同渗压作用下裂纹的扩展情况表明,渗透压的存在加剧了分支裂纹的扩展,高渗透压作用下分支裂纹扩展由稳定扩展变成不稳定扩展,并导致分支裂纹尖端岩桥剪切破坏,同时考虑分支裂纹的相互作用,建立了高渗透压作用下压剪岩石裂纹体岩桥剪切贯通的断裂破坏力学模型,最后依据裂隙岩体的损伤力学效应研究了岩体的初始损伤及损伤演化柔度张量,提出了高渗压下压剪岩石裂纹渐进破坏的损伤演化方程。该理论为定量研究高渗压下裂隙岩体的失稳破坏提供了理论依据。 相似文献
5.
切削机理模型是研究岩石钻进切削过程中的切削力以及切削热的基础。在分析岩石切削机理模型的基础上,基于摩尔理论和裂纹扩展理论,分析中硬岩石切削状态,认为在中硬岩石切削过程中岩石存在着脆性切削和延展性切削2种方式,在此基础上得到新的中硬岩石切削机理模型。以砂岩、大理岩和花岗岩为钻进对象,开展微钻实验研究。结果表明：切削过程为岩石在刀具的扭矩和推进力作用下发生破坏,导致小岩屑、大切屑不断循环产生的过程,小大切屑形成主要源于岩石挤压变形和裂纹生成扩展。实验结果与岩石切削机理表现出较好的一致性。 相似文献
6.
液氮温度极低（?195.8℃）,当与储层岩石接触时,能够改变岩石物性并对岩石结构产生损伤致裂,因此,可用于储层压裂改造。为了研究液氮压裂时低温对岩石力学性能的影响,分别对不同含水状态（干燥与饱和）的不同类型（大理岩、砂岩和花岗岩）岩石进行液氮冻结处理,并对冻结前、后岩样进行抗拉及单轴抗压强度对比测试。结果表明,经液氮冻结后,岩石的单轴抗压强度、抗拉强度和弹性模量都降低;岩石在干燥状态下,液氮冻结对大理石强度的影响大于对红砂岩的影响;岩石饱和水状态下,液氮冻结对红砂岩强度的影响大于对大理岩的影响;饱和水状态岩石经液氮冻结后,其应力-轴应变曲线在弹性变形阶段出现一个拐点;对于同种类型岩石,饱和水状态能加剧液氮冻结并对岩石损伤,岩石强度影响显著;对3种岩样微观结构进行了电镜扫描（以大理岩为例进行分析）,发现经液氮冻结后在矿物颗粒之间生成了微裂隙。研究结果可为进一步研究液氮压裂机制提供试验依据。 相似文献
7.
水-岩化学作用等效裂纹扩展细观力学模型 总被引：2，自引：0，他引：2
从化学腐蚀下岩石细观结构的变化出发,研究水化学溶液对岩石中裂纹的腐蚀作用。运用地球化学矿物-水反应的溶解动力学,考查水-岩反应化学溶液中不同时间段离子浓度的变化,从理论上探讨化学腐蚀下等效裂纹扩展的定量化分析方法。通过质量守恒定律计算出裂纹在迹长及隙宽方向的变化,将水化腐蚀等效成有效裂纹长度,建立了水-岩化学作用下等效裂纹扩展的计算公式并计算应力强度因子。通过对砂岩的研究结果表明,水-岩化学作用对岩石裂纹的扩展有显著影响,并且具有时间效应。同时,水化学溶液的离子浓度及pH值大小对裂纹的扩展存在影响,其中pH值的变化对岩石的断裂力学效应更加显著。当溶液的酸性越强或碱性越强,腐蚀越大,裂纹扩展越快;pH值为中性时,腐蚀作用得到较大缓解,裂纹发展缓慢。为定量研究裂隙岩体在水岩化学作用下的细观机理提供了一种新的思路。 相似文献
8.
含水状态下膏溶角砾岩破裂全程的细观力学试验研究 总被引：1，自引：0，他引：1
利用新型岩石细观力学试验系统,对石家庄-太原铁路专线太行山隧道工程6#斜井的膏溶角砾岩在单轴压缩荷载作用下的岩石细观损伤裂纹扩展直至破裂的全程进行了实时观测,得到了不同含水状态下岩石初始损伤微裂纹的萌生、扩展、连接、贯通直至宏观破裂的数字显微和全场实时图像。从岩石细观损伤机制出发,结合同时获得的应力-应变曲线,将损伤破裂过程分为4个阶段,得到了含水状态下岩石损伤发展演化的初步规律,并给出了应力损伤门槛值,发现水环境影响下造成的初始损伤微裂纹是水对膨胀软岩力学性质产生软化作用的重要因素。 相似文献
9.
三轴应力下水对粉砂质泥岩蠕变力学特性影响作用试验研究 总被引：1，自引：0，他引：1
采用岩石流变试验机,在三轴应力下分别对干燥与饱水两种含水状态的粉砂质泥岩开展室内蠕变力学试验。分析了水对粉砂质泥岩蠕变量、蠕变长期强度的影响作用。依据岩石的蠕变性质,选取Burgers蠕变模型对其进行描述,得出两种含水状态下岩石的蠕变模型参数。对比干燥与饱水含水状态下岩石的Burgers蠕变模型参数,分析得出了水影响Burgers蠕变模型参数的基本规律。结果表明:（1）相同应力水平下,水对粉砂质泥岩的瞬时应变特性影响较小,而对岩石的蠕应变特性影响相对较大;（2）饱水试样的蠕变长期强度是干燥试样的39.3%,由于水的作用,粉砂质泥岩的蠕变长期强度大幅降低,在工程中应考虑由于水的影响作用而导致的岩石长期强度降低问题;（3）水对Burgers蠕变模型各参数的影响作用从大到小依次为:η1、G1、G2和η2,即水对Burgers模型中串联的元件力学特性影响较大,而对并联的元件力学特性影响相对较小;（4）由于水的影响作用,粉砂质泥岩达到稳定蠕变阶段所需的时间显著增加,岩石的稳态蠕变速率显著增大;（5）由于水的影响作用,导致粉砂质泥岩的蠕变力学特性发生显著改变。因此,在重大岩石工程中应重视水对岩石时效变形的影响作用。 相似文献
10.
《岩土力学》2017,(7):1999-2006
岩体冻融风化作用主要受控于岩性、岩体结构、饱和状态及温变环境等因素。采取新疆寒区4种裂隙岩石进行温度变化下的冻融应变试验,得到了裂隙岩石在饱水及干燥冻融状态下的应变过程,即饱水状态下为8个阶段、干燥状态下为5个阶段;针对饱水裂隙岩石提出了冻融作用的胀缩率?,得到了不同岩性的?与冻融循环次数的拟合关系表达式,同时分析了在循环冻融过程中应变的变化规律,即裂隙岩石的冻胀阶段的微应变最大值都随循环次数的增加而增大。此外,通过在不同恒温下裂隙岩石冻融应变试验,分析了应变的变化规律,得到应变与不同恒温的拟合关系表达式;试验结果表明:裂隙岩石的?都随冻融次数的增加而增大,胀缩率的变化程度与不同岩样的孔隙率特征有关。饱水裂隙岩石在冻融过程中对温度具有较强的敏感性,损伤表现在温度损伤和冻胀损伤。 相似文献
11.
Subcritical crack growth plays an important role in evaluating the long-term stability of structures in rocks. By applying the constant-displacement-relax method, two groups of test specimens that one immersed in groundwater and the other in air were tested to get the parameters of subcritical crack growth in double torsion test. The relations of the stress intensity factor K I versus the subcritical crack growth velocity V were obtained under the two different environments, and the behavior of subcritical crack growth was also analyzed. The results showed: the relations of lg K I ? lg V accorded with linear rules, which is in good agreement with Charles theory; Compared with specimens in nature state, the lg K I ? lg V curves of saturated water specimens locate top left comer of those of air specimens. The slope of curve is smaller, and the intercept is bigger, which shows that the water–rock interaction speeds up the subcritical crack growth. And A increases 2.9 × 1018 folds but n decreases from 85.12 to 40.83 because of the water–rock interaction. Meanwhile, the fracture toughness K IC also decreases obviously from 2.55 in air to 2.26 in water due to water rock interaction. The testing results provide a basis for time-dependence of rock engineering stability. 相似文献
12.
Fissures in natural rocks play an important role in determining the strength, deformability and failure behavior of rock mass. However in the past, triaxial compression experiments have rarely been conducted for rock materials containing three-dimensional (3-D) fissures and the failure mechanical behavior of fissured rocks is not well known due to the difficulty of conducting triaxial experiments on fissured rocks. Therefore in this research, conventional triaxial compression experiments were performed to study the strength, deformability and failure behavior of granite specimens with one preexisting open fissure. Thirty-one specimens were prepared to perform conventional triaxial compression tests for intact and fissured granite. First, based on the experimental results, the effects of the confining pressure and the fissure angle on the elastic modulus and the peak axial strain of granite specimens are analyzed. Second, the influence of the confining pressure on the crack damage threshold and the peak strength of granite with respect to various fissure angles are evaluated. For the same fissure angle, the crack damage threshold and the peak strength of granite both increase with the confining pressure, which is in good agreement with the linear Mohr–Coulomb criterion. With increasing fissure angle, the cohesion of granite first increases and later decreases, but the internal friction angle is not obviously dependent on the fissure angle. Third, nine crack types are identified to analyze the failure characteristics of granite specimens containing a single fissure under conventional triaxial compression. Finally, a series of X-ray microcomputed tomography (CT) observations were conducted to analyze the internal damage mechanism of granite specimens with respect to various fissure angles. Reconstructed 3-D CT images indicate obvious effects of confining pressure and fissure angle on the crack system of granite specimens. The study helps to elucidate the fundamental nature of rock failure under conventional triaxial compression. 相似文献
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15.
《Russian Geology and Geophysics》2015,56(9):1292-1307
Miarolitic granite pegmatites are a unique natural object that makes it possible to study magmatic processes that lead to the formation of ore-forming media and systems. This paper summarizes modern views on phase transformations in aqueous silicate systems at parameters close to those of the transition from magmatic to hydrothermal crystallization. Comparison of phase diagrams and the results of study of pegmatite-forming media permits making conclusions about the crystallization of the water-saturated magmas of miarolitic granite pegmatites. The fluid regime of aqueous granite systems of simple composition, not enriched in fluxing components, is determined mainly by magma degassing or the supply of volatiles with flows of transmagmatic fluids. These processes cause the separation of essentially carbon dioxide or essentially hydrous fluid. During the evolution of such magmas, crystallization from silicate melt is separated in PT-space and, possibly, in time from the crystallization from aqueous or mixed carbon dioxide-aqueous super- and subcritical solutions. The evolution of chambers of water-saturated granitic and pegmatitic magma enriched in F, B, and alkali metals presupposes the formation of a heterogeneous mineral-forming medium in which crystallization occurs in the magmatic melt at high-temperature stages; as temperature decreases, crystallization can proceed in hydrous fluid, hydrosilicate, and/or hydrosaline liquids simultaneously. Hydrothermal crystallization can also take place in a heterogeneous medium consisting of aqueous solutions of different salinities and vapor or vapor-carbon dioxide gas mixture. The relationship between different fluid regimes during the evolution of volatile-saturated granitic and pegmatitic magmas determines the variety of postmagmatic rocks accompanying granite massifs. 相似文献
16.
A significant drop in seismic travel times of up to 1.0% occurred in the Charlevoix region between 1979 and 1980, possibly related to the M = 5.0 (Aug., 1979) earthquake in the vicinity. A travel-time drop of this magnitude could have been produced either by the closing of dry or saturated cracks in the upper crustal material or by the saturation of dry or partly saturated cracks. However, the anisotropy of travel-time changes in this area supports the view that this travel-time drop was caused by the closing of water-saturated aligned vertical cracks in the crustal material. Three different crack directions with respect to north were resolved: 0 ° or 90 ° in the Precambrian rocks underneath the St. Lawrence River, −18° or 72° in the shallow rocks (< 5 km) of the Charlevoix crater, region, and +35° or 125° in the Paleozoic cover rocks. Crack closure would require a decrease in the pore volume of the rocks which would be expected to produce subsidence in the Charlevoix area. Since repeated levellings restrict the vertical crustal motion during this time interval to less than 2 cm, we conclude that either the effective aspect-ratio of cracks is less than 0.0001 or the process of crack closure occurred in a number of unconnected regions. More specifically the crack deformation would have to occur in isolated inclusions less than 1 km in diameter and no deeper than about 6 km. The process of crack closure may have been triggered by the passage of seismic waves from the M = 5.0 earthquake. 相似文献