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基于核磁共振的脆硬性泥页岩水化损伤演化研究 总被引：1，自引：0，他引：1
为研究脆硬性泥页岩水化后细观结构的损伤演化特征,利用核磁共振技术对不同浸泡时间的脆硬性泥页岩试样进行测量,得到不同浸泡时间的试样质量变化、横向弛豫时间T2谱分布以及核磁共振成像。结果表明：水化作用会对岩石内部产生损伤,岩样吸水率在最初的8 h内变化相对较大,1 d后相对接近稳定,之后变化不明显。随着浸泡时间的延长,微裂缝在水化的作用下快速扩展、贯通使岩样表面产生明显裂纹。核磁共振T2谱图和成像结果表明,水化作用使岩样微观结构重新分布,T2曲线信号幅度发生明显的变化,并随着浸泡时间的延长而增加。整个水化损伤分为3个阶段：大尺寸孔隙裂纹发展阶段;小孔隙产生、大尺寸孔隙裂纹加剧扩展;小孔隙加剧产生扩展、大尺寸孔隙裂纹归并贯通至水化破坏阶段。核磁共振图像显示同一块岩样在不同浸泡时间的内部微观结构分布,动态地显示岩石的水化损伤过程。 相似文献
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利用偏光显微镜对经历不同高温循环作用后的细粒大理岩进行观测,通过统计微裂纹长度、开度、数量等参数,探讨不同加热循环次数后岩样内微裂纹的扩展规律。结果表明,（1）经历不同热循环次数作用的岩样,微裂纹的数量和长度均不同,未经热处理岩样内颗粒致密,胶结较好,内部无明显的微裂纹。经历4次热循环作用后岩样内微裂纹发育明显,以晶界裂纹为主,开度和长度均显著增加。岩样经历16次热循环作用后开度持续增大,为55 µm,是4次热循环的4倍;（2）对不同热循环处理后岩样内部发育微裂纹的方向进行了统计,发现微裂纹无明显的方向性,还表明细观切片的取样位置对微裂纹的发育影响不大;（3）线性裂纹密度随热循环次数的增加而增大,经历16次热循环作用后岩样的线性裂纹密度是没有经历热处理岩样的21倍。 相似文献
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提出了一种用于边坡位移监测的微机电系统双轴测斜仪原始采集数据累计位移的降噪算法,通过采用卡尔曼滤波器与Hamming窗FIR滤波器组合滤波的方法,对MEMS双轴测斜仪自身以及外部环境因素影响产生的高频噪声和随机噪声能够实现较好地去除,从而可提高监测数据的处理与解释精度。在原始采集数据高频异常振荡较大的区域,先卡尔曼滤波再Hamming窗FIR滤波其输出数据更符合实际应用,趋势拟合更好。 相似文献
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为有效地指导煤层气水平井压裂工程,评价压裂施工效果,提出将微地震成像裂缝监测技术应用于煤层气水平井压裂施工中。利用微地震成像监测煤层气水平井裂缝延伸的方位、缝长及缝高,分析裂缝双翼不对称发育原因。以沁水盆地寺河区块为例,将水平井和同规模、同层位垂直井的裂缝监测结果进行对比分析,结果显示,因布井方位及施工工艺影响,水平井压裂液滤失量大、易产生多裂缝,且裂缝延伸距离相对较短。指出后续水平井布井应考虑水平段轴线与最小主应力方向平行,增大压裂设计规模和压裂级数,以保证煤层气水平井高效开发。 相似文献
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单孔岩样水压致裂的数值分析 总被引：2，自引：0，他引：2
水压致裂是改变岩体结构的一种天然行为和人为手段。采用F－RFPA2D软件,对水压致裂过程、裂缝扩展形态及注水孔形状和大小、应力条件和岩样强度等影响因素进行了研究。将开始出现声发射的水压称为微裂压力,将声发射急剧增多、裂缝非稳定扩展直至岩样破坏的水压称为破裂压力。岩样尺寸一定时,微裂压力和破裂压力随内孔面积增加而降低,方形孔岩样的微裂压力和破裂压力均小于同面积的圆形孔。微裂压力和破裂压力随围压或岩样强度增加而增加,且其差值随岩样强度增加而增加,理论破裂压力与模拟值趋势基本一致。方形孔的宏观裂纹起裂位置多在角点附近,而圆形孔比较随机。无围压时,宏观裂纹的延伸方向随机;有围压时,宏观裂纹扩展方向大致与主应力方向一致,且沿较大主应力方向的宏观裂纹扩展至岩样破坏,较小主应力方向宏观裂纹不完全发育。研究结果对水压致裂试验和工程实践有一定参考意义。 相似文献
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微地震的线性方程定位求解及其病态处理 总被引：7，自引：0，他引：7
岩体破裂时会产生微地震现象,微地震的发生与岩体内部的能量释放以及进一步的裂纹演化、破裂有着密切的关系。所以,可以用微地震的时空分布来预测岩体的破裂。微地震定位是预测岩体破裂的基础。研究了微地震定位方程求解过程中不同情况下解的几种情况无穷解、唯一解和最小二乘解。由于定位问题属于反问题,因此,定位方程往往呈现病态,为此,进一步分析了病态方程的正则化处理方法。实际算例证明,用正则化方法求解定位方程具有计算简单、收敛速度快的优点,非常适合求解此类问题。 相似文献
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微地震监测技术在水平井压裂中的应用 总被引：1，自引：0，他引：1
用微地震法在油田生产波及区对生产动态进行实时监测,是目前国内外广泛关注的前沿课题。文中论述了产生微地震事件的力学机理、微地震监测原理及方法。利用微地震监测技术对泌阳凹陷BYHF1页岩水平井分段大型压裂过程实时监测,运用偶极子测井和VSP资料建立监测井区的初始速度模型,并通过射孔炮对其校正。在识别出有效微震事件的基础上,利用纵波和横波信息计算得到微地震事件的位置,通过可视化技术对压裂井区裂缝发育的方向、大小、空间分布进行了描述,监测结果与成像测井结果吻合良好。 相似文献
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对称和非对称载荷下声发射特征的数值模拟研究 总被引：3，自引：0，他引：3
利用自行开发的岩石破裂过程分析RFPA^2D系统，研究了对称载荷和非对称载荷下岩样的破坏过程以及破坏过程中所呈现的声发射特征。数值模拟结果演示两种条件下由微破裂诱致宏观破坏的演化过程以及和微破裂相关的声发射事件源的空间分布特征和事件序列特征。数值模拟结果指出，和对称载荷压缩实验相比，两者的最大区别在于在非对称载荷压缩实验中局部的剪切破坏的发生以及一个更加局部化的声发射事件源分布。从物理意义上讲非对称载荷实验提供了在预定破裂路径下研究脆性破坏的方法，从声发射研究方面来说非对称实验比对称实验能更好地观察声发射事件源的局部化。 相似文献
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We study the aspect of unstable behavior (like strain localization bands) in elastic solids as a consequence of micro-fracturing.
A two-scale approach of computational homogenization is considered. The macroscopic behavior is investigated by finite element
computations on a unit cell. At the micro-level, we consider a granular structure with elastic grains. The inter-granular
boundaries are modeled with cohesive laws, friction and unilateral contact. We show that decohesion between grains gives rise
to macro-instabilities, indicated by the loss of ellipticity, typical for deformation localization bands. The relation between
the microscopic softening on inter-granular boundaries and the onset of macro-instabilities is studied through numerical examples.
The influence of the cohesive law and friction parameters is analyzed. For periodic distributions of granular structures,
we prove the loss of periodicity by failure and the corresponding size dependence effect in the homogenized response. We present
numerical examples of bifurcation of solutions for granular cell structures and of particular solutions specific to elementary
volumes with periodic cell distribution. Size dependence appears in the unstable regime and is strongly influenced by cohesion
and friction parameters. 相似文献
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Shi-Li Qiu Xia-Ting Feng Jian-Qing Xiao Chuan-Qing Zhang 《Rock Mechanics and Rock Engineering》2014,47(2):401-419
The behavior of rock damage evolution under unloading conditions is of utmost importance for the analysis of the stress-induced failure of overstressed rock masses. In this paper, a new experimental approach, the incrementally cyclic loading–unloading pressure test (ICLUP test), is designed to quantify stress-induced micro-fracturing and fracturing under the condition of confining pressure reduction. The experimental results demonstrate that the pre-peak damage and deformation characteristics of marble specimens may be easily quantified by irreversible strains, and two damage stages, namely, the linear steady stage and the nonlinear unsteady stage, which are, respectively, represented as a linear steady rate and a nonlinear unsteady rate of damage evolution, occur along with the increase of unloading damage. The new model is proposed to describe the features of pre-peak unloading damage evolution, and the physical meanings and ranges of its material parameters are explained and analyzed. Furthermore, the evolution of volumetric dilation and elastic parameters which occurs along with the increase of unloading damage is revealed. Also discussed in this paper are the inhomogeneity and initial damage of specimens, as well as related research planned to be performed in the future. 相似文献
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The landslide can destroy all kinds of constructions, and seriously hinder people's production and life as well as the development of national economy. Bolt is one of the main methods for slope treatment, but it is difficult to monitor its construction quality and anchoring effect directly. With the rise and development of MEMS (Micro-electro mechanical system) technology, MEMS sensors, with the advantages of small size, low cost and high precision, quickly come out from the conventional monitoring methods and provide new possibilities for the monitoring field in geological engineering. In this paper, based on MEMS sensors, a model test was designed to explore the stability of the slope after treatment by bolts. Natural river sands were used to prepare slopes with angle of 45° through the air-plluviation method. In addition, the tests were divided into two groups (with or without bolts). MEMS sensors were set up in the slope to wirelessly and continually capture the acceleration, angular velocity and angle of slope sliding triggered by simulated rainfall in real-time. It was found that: with no treatment, the acceleration and angle in the interior and the bottom of the slope gradually changed during rainfall, while those parameters in the rear and the surface of the slope had no significant change, which indicated that the slope creep mainly occurred in the interior and the bottom of the slope before failure. When landslides occurred, the movement monitoring indexes in the interior and the bottom of the slope suddenly changed, followed by those in the rear and the surface of the slope, which means that when the sandy slope slides, the interior and the bottom of the slope slides first, and then the rear and the surface of the slope surface fail. This is a typical retrogressive landslide. After the slope was treated by bolts, only creep could be observed during long-term rainfall, and the acceleration and angle in the bottom, interior and surface of the slope gradually changed, while almost no change was found in the rear of the slope, which shows that under rainfall conditions, overall creep occurs for the slope after reinforcement, the slope angle decreases, and there is no landside. The experimental results prove that MEMS sensors can realize low-cost, high-precision, continuous real-time monitoring of slope, and can capture gradual changes of movements before failure and the sudden change when landslide occurs. It should play a certain role in the study of landslide mechanism and landslide warning, and has a broad application in the field of geological engineering monitoring. 相似文献
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滑坡破坏各种建筑工程,严重影响了人民生产生活以及国民经济的发展。锚杆作为边坡治理的主要手段之一,其施工质量与锚固效果难以直接监测。随着微机电系统(MEMS)技术的兴起与不断发展,MEMS传感器具有体积小、造价低和精度高等优点,使其从常规监测手段中脱颖而出,为地质工程监测提供了新的可能。通过设计模型试验,基于MEMS传感器探讨锚杆对边坡的加固作用。试验采用天然河砂,通过撒砂法堆坡,边坡坡角为45°,分有锚杆加固和无锚杆加固2组。以降雨触发滑坡,将MEMS传感器布设在边坡内部,实现对边坡内部各点的加速度、角度和角速度的实时连续监测。研究表明:当未加固边坡蠕滑开始时,边坡内部和坡脚处的加速度与角度发生渐变,边坡后缘与表面处的加速度和角度变化不明显,表明边坡蠕滑主要发生在边坡内部与坡脚处;滑坡发生时,边坡内部与坡脚处的加速度和角度率先发生突变,边坡后缘与表面的参数随后发生突变,表明砂土坡破坏的瞬间,其内部与坡脚处先发生滑动,边坡后缘与坡面随后滑动,为典型的牵引式滑坡。采用锚杆加固后,边坡只发生蠕滑,边坡内部、坡脚处与坡面的加速度和角度有明显渐变,边坡后缘的各指标几乎无变化,表明降雨条件下,加固后的边坡发生整体蠕滑,边坡坡角降低,不发生破坏。MEMS传感器能够实现低成本、高精度的连续实时监测边坡蠕滑的渐变规律,捕捉到滑坡发生时运动的明显突变,对研究边坡的滑动机制及滑坡预警有一定的应用价值,在地质工程监测领域具有广阔的应用前景。 相似文献
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Christian Beck 《Earth》2009,96(4):327-49
The late Quaternary sedimentary fills of several lakes of the north-western Alps are revealed to be possible paleo-seismological “archives” in a moderately active seismo-tectonic region. The strongest historically reported events can be correlated with specific layers, whose textures result from different processes: i) mass failures of sub-aqueous slope deposits (especially delta foresets) evolving into hyperpycnal currents influenced by seiche effects and/or multiple reflections on lake basin slopes; ii) in situ liquefaction and flowage; and iii) micro-fracturing. Based on identification of the sedimentary signature of a well-documented historical earthquake, the paleoseismic interpretation can be extrapolated back to 16,000 yrs BP with a reconstruction of a time series and textural identification of slope failure-related turbidites (the most frequent earthquake signature). The obtained time series are compatible with historical seismicity in terms of recurrence interval. 相似文献
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地震检波器技术与发展研究 总被引：4，自引：0，他引：4
地震勘探数据采集的关键器件是检波器,分为模拟检波器和数字检波器。在分析了各种模拟检波器特点之后,再对数字检波器进行研究。这里展示了基于MEMS(Micro Electro Me-chanical systems)技术的数字检波所代表的机电合一、微型化、宽频谱线性响应的发展方向。同时指出,由于目前MEMS数字检波器的不完善,在今后一段时间内,基于电磁感应机理的数字检波器,将与基于MEMS技术的数字检波器长期共存与互补。 相似文献
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《China Geology》2022,5(4):630-636
In this work, the authors monitored the formation and dissociation process of methane hydrate in four different rock core samples through nuclear magnetic resonance (NMR) relaxation time (T2) and 2D imaging measurement. The result shows that the intensity of T2 spectra and magnetic resonance imaging (MRI) signals gradually decreases in the hydrate formation process, and at the same time, the T2 spectra move toward the left domain as the growth of hydrate in the pores of the sample accelerates the decay rate. The hydrate grows and dissociates preferentially in the purer sandstone samples with larger pore size and higher porosity. Significantly, for the sample with lower porosity and higher argillaceous content, the intensity of the T2 spectra also shows a trend of a great decrease in the hydrate formation process, which means that high-saturation gas hydrate can also be formed in the sample with higher argillaceous content. The changes in MRI of the sample in the process show that the formation and dissociation of methane hydrate can reshape the distribution of water in the pores.©2022 China Geology Editorial Office. 相似文献
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Effects of entrapped residual air bubbles on tracer transport in heterogeneous soil: Magnetic resonance imaging study 总被引：1，自引：0，他引：1
Vladimira Jelinkova Michal SnehotaAndreas Pohlmeier Dagmar van DusschotenMilena Cislerova 《Organic Geochemistry》2011,42(8):991-998
Magnetic resonance imaging (MRI) was used to study the process of infiltration and solute transport in an undisturbed soil sample of coarse sandy loam. The sample was subjected to the recurrent ponded infiltration (RPI) experiment, which was carried out in order to assess the changes in the entrapped air volume and its impact on steady state flow rates and solute breakthrough. The main stages of the first and second experimental RPI runs were monitored using an MRI sequence that follows both water density and magnetic relaxation. In a steady state stage of each experimental run a nickel nitrate pulse was injected in order to visualize the solute breakthrough. Effluent from the sample was collected for chemical analysis and a breakthrough curve of the nickel was constructed. To obtain information about the soil structure and to reveal potential preferential pathways, the soil sample was scanned using computed tomography. The local nickel ion transport breakthrough was evaluated from MR images in a series of local observation points distributed along the selected preferential pathways.The preferential flow instability phenomenon with the emphasis on air bubble formation was shown by detecting a 60% decrease of the steady state infiltration rate. The detailed analyses of MRI measurements at observation points revealed air bubble formation, producing a flow rate decrease accompanied by redirection of nickel ion transport trajectories. By analyzing M0 maps it was found that the volumetric water content decrease was 2.2%. 相似文献