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1.
Poro‐mechanical and thermo‐mechanical processes change the fracture aperture and thus affect the water flow pattern in the fracture during the cold water injection into enhanced geothermal systems (EGS). In addition, the stresses generated by these processes contribute to the phenomenon of reservoir seismicity. In this paper, we present a three‐dimensional (3D) partially coupled poro‐thermoelastic model to investigate the poroelastic and thermoelastic effects of cold water injection in EGS. In the model, the lubrication fluid flow and the convective heat transfer in the fracture are modeled by the finite element method, while the pore fluid diffusion and heat conductive transfer in the reservoir matrix are assumed to be 3D and modeled by the boundary integral equation method without the need to discretize the reservoir. The stresses at the fracture surface and in the reservoir matrix are obtained from the numerical model and can be used to assess the variation of in situ stress and induced seismicty with injection/extraction. Application of the model shows that rock cooling induces large tensile stresses and increases fracture conductivity, whereas the rock dilation caused by fluid leakoff decreases fracture aperture and increases compressive total stresses around the injection zone. However, increases in pore pressure reduce the effective stresses and can contribute to rock failure, fracture slip, and microseismic activity. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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白鹤滩水电站坝区深部破裂岩体地应力演化特征 总被引：1，自引：0，他引：1
还原深部破裂岩体赋存地应力场演化过程,研究深部破裂岩体成因、形成年代及发展演化趋势。以岩体深部破裂特征为基础,结合构造演化、河谷演化及浅生改造理论,采用数值模拟方法,从地应力场变化及应变能释放角度解释深部破裂形成演化过程。研究表明,宽谷期大规模夷平作用使深部破裂赋存应力场发生根本性改变,与现今应力场趋于一致,但并未导致深部破裂形成;侧向卸荷是深部破裂形成的主要原因,侧向卸荷导致主应力减小,但方向维持不变,当侧向临空面出现,伴随应变能释放,NW向结构面拉张形成具有继承性的NW向深部破裂;错动带的差异回弹形成残余拉应力,导致NE向新生性深部破裂形成;深部破裂形成地质年代应大致对应于Ⅲ级阶地形成初期,即Q2晚期～Q3早期阶段 相似文献
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This paper presents an intrinsic micromechanical model for poroelasticity that leads to an alternative set of material constants. In the intrinsic model, the deformations of the solid phase, the fluid phase, and the pore space are explicitly modeled, and porosity is considered as a primary variable. The averaging process distinguishes an external frame surface averaging and an internal phase volume averaging. The variational principle leads to a porosity equilibrium equation that defines the nonlinear deformation of pore volume. Three fundamental deformation modes with their intrinsic material constants are identified: the shape preserving volumetric deformation of the solid phase, the porosity change due to solid grain rearrangement, and the porosity change associated with the microanisotropy and microinhomogeneity of solid phase. The linearized model is fully consistent with the Biot theory of poroelasticity. A semilinear model considering only porosity deformation nonlinearity with linear material constant leads to a universal exponential strain hardening law. The theory is tested against laboratory data of sandstone. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
4.
颗粒破碎对于粗粒土的应力变形性质有显著影响。在Rowe剪胀方程的基础上考虑颗粒破碎耗能的影响,并引入颗粒破碎的演化规律对颗粒破碎耗能进行计算,得到了一个简单实用且对粗粒土适用性较好的剪胀方程。主要结论如下：（1）通过粗粒土的三轴CD试验结果分析并证明了弹性应变对于剪胀比的影响较小,因此,可以将剪胀比 表示为 ,进而得到了剪胀方程表达式的一般形式。（2）将剪胀方程中的临界状态应力比Mc折减为摩擦系数M,并引入了颗粒破碎的演化规律,将M定量表示为广义剪应变的函数,从而使得所计算的破碎耗能在剪切过程中是递增的,且逐渐趋于稳定值,符合了颗粒破碎不可逆的规律。（3）试验表明,剪胀方程中的未知量 与摩擦系数M之间呈现显著的线性关系,将该关系代入剪胀方程即确定了方程的具体表达形式,并且利用堆石料的三轴CD试验证明了其对粗粒土的剪胀性预测效果较好。 相似文献
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一种处理加筋体结构问题的有限元分析模型 总被引：2，自引：0，他引：2
在用有限元法分析混凝土中钢筋或峒室岩体中的锚杆变形问题时,经常会遇到线单元与体单元耦合变形的问题,现有的方法一般是将锚杆或钢筋简化成桁架或梁单元,作为嵌入单元将其贡献刚度叠加到体单元的刚度矩阵中。但无论哪种简化都没有反映复杂应力状态下加强构件变形处处不均匀的特性。在总结其他学者研究的基础上,将这类问题统称为加筋体问题,并提出一种新的的有限元分析模型。模型中利用连续介质力学基本理论将加强构件的轴向变形能、扭转变形能及弯曲变形能叠加到实体单元的势能泛函中,用最小势能原理导出了一种非线性的单元平衡方程。利用该模型编制了相应的程序,并与商用软件Abaqus的计算结果作了对比分析。 相似文献
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在依据摩尔图解及断裂力学理论对底板卸荷突水破坏分析的基础上,运用损伤断裂力学并结合统一强度理论,建立了考虑渗透水压作用下分支裂纹端部形成的塑性区范围计算方程与岩体发生贯穿破坏时的损伤阀值。将裂纹扩展过程与岩体损伤耦合起来,确定了裂纹的损伤断裂能量计算公式并分析了其影响因素。结果表明：侧压系数 0.5时,最大主应力完全卸荷状态下裂纹端部应力强度因子比双轴应力状态下大,岩体易发生破坏。考虑了裂纹端部塑性区的影响,裂纹损伤断裂能量相比于不考虑其影响时偏大,增大了煤层底板突水的危险性。裂纹损伤断裂能量 与裂纹半长 、裂纹面连通面积与总面积之比 、裂纹面渗透水压 及最小主应力 呈正相关,与裂纹面摩擦系数 及岩体的弹性模量 呈负相关。分析结果为底板突水破坏机制研究提供了一定的参考依据。 相似文献
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接触变质带中冷凝收缩缝裂缝参数定量研究 总被引：1，自引：0，他引：1
模拟岩浆侵入时期的温度场及应力场获取围岩中温度及应力的分布,综合应用应变能及表面能理论,建立热应力与冷凝收缩缝参数之间的定量关系,对裂缝参数作出定量预测,进而总结变质带中冷凝收缩缝的发育规律。对GY凹陷北斜坡接触变质带研究发现：变质带厚度随侵入岩厚度增大而增大,侵入岩厚度小于20 m时无变质带;热应力随着距离侵入岩距离的增大而减小。冷凝收缩缝主要靠近侵入岩体分布,裂缝线密度最大值约为13条/m;远离侵入岩体裂缝线密度迅速变小,至变质带外边缘,裂缝线密度降为3～6条/m。整体上,上变质带孔渗性能稍好于下变质带孔渗性能。冷凝收缩缝孔隙度最大值位于侵入岩厚度最大部位;短轴方向裂缝渗透率与铅直方向渗透率分布相似,两者值均大于长轴方向渗透率。岩心统计资料验证了模拟计算结果的可靠性。 相似文献
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岩石在细观尺度上是由矿物颗粒胶结而成,除细观结构的力学特性外,其几何特征（颗粒界面网络结构和颗粒粒度分布）也对宏观断裂能具有一定的影响。为了探索这种几何特征与大理岩断裂能之间的相关性,从而进一步揭示岩石细观断裂机制,首先通过三点弯曲试验测定大理岩的断裂能,然后在试验后的三点弯试件断口处取岩石切片,进行电镜（SEM）扫描以获取岩石细观结构图像。利用图像处理技术获取岩石细观颗粒的界面网络图。通过对颗粒界面网络图分析,发现颗粒界面网络拓扑结构与颗粒粒度分布具有较强的分形特征。将二者分形维数与试件宏观断裂能相对比,发现它们之间具有很强的相关性。界面网络分形维数与宏观断裂能具有很强的二次相关性,而粒度分布维数与宏观断裂能之间具有较强的线性相关性。宏观断裂能随着两种分形维数的增大而增大。该研究结果揭示了宏观断裂能与岩石细观结构几何特征的相关性,加深了对宏观断裂能细观机制的理解。 相似文献
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O. Coussy 《国际地质力学数值与分析法杂志》2007,31(15):1675-1694
This paper aims at revisiting the constitutive equations of unsaturated porous solids at the light of a Lagrangian saturation concept. By referring the currently wetted porous volume to the reference configuration, the Lagrangian saturation is the state variable associated with the interfacial energy changes only, irrespective of the elastic energy required for deforming the solid matrix. The Lagrangian saturation concept provides the basis of a generic approach to the theory of poroelastoplasticity in unsaturated conditions. We successively examine the case where the saturating fluids occupy disconnected networks and the case where the networks are connected so that the saturating fluids can invade the porous solid or recede from it. The analysis provides the restricted situations where the averaged pore pressure may play the role of an effective pore pressure. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Stress of urban energy consumption on air environment 总被引：1，自引：0，他引：1
With rapid urbanization and heavy industrialization as well as the rapid increase of cars in China, the effect of energy consumption
on urban air environment is increasingly becoming serious, and has become a hot topic for both scholars and decision-makers.
This paper explores the effect mechanism and regulation of urban energy consumption on the air environment, and summarizes
the framework of the stress effect relationship and the evolutionary process. In accordance with the effect relationship of
the internal factors between the two, analytic approaches studying the stress effect of urban energy consumption on air environment
are proposed, including the analysis of air environment effects caused by urban energy consumption structure change, and the
analysis of air environment effects caused by urban energy economic efficiency change, as well as a decomposition analysis
of air pollutant emission caused by urban energy consumption. Applying the above-mentioned approaches into a case study on
Beijing City, this paper analyzes the effect relationship among urban energy consumption structure improvement, energy economic
efficiency increase and air quality change since the period when Beijing City officially proposed to bid for the 2008 Olympic
Games in 1998. In addition, it further analyzes the effect and contribution of urban industrial activity level, industrial
economic structure, industrial energy intensity, and industrial energy structure as well as emission coefficients on the change
in industrial SO2 emission, which can provide valuable information to the government for making comprehensive environmental policies, with
the use of the logarithmic mean Divisia index (LMDI) method. It is shown that under the precondition that the industrial economy
maintain a continuous and rapid increase, improvements in energy intensity and a decline in emission coefficients are the
main means for reducing Beijing’s industrial SO2 emissions. 相似文献
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非静水应力作用固体的化学位及其构造地球化学意义 总被引：1，自引：1，他引：0
非静水应力作用的含水岩石中的力学 -化学相互作用是构造地球化学研究的主要对象之一 ,非静水应力作用固体物质的化学位则是了解这种作用的关键。本文在总结前人有关成果的基础上 ,从理论上了提出了非静水应力作用固体岩石中固 -液界面上的固体物质的化学位的一般形式。在此基础上 ,根据 Onsager扩散方程和局部平衡假设 ,推导了固体物质在颗粒间流体中溶解浓度随固体岩石中应力场和应变能的时空变化关系的动力学方程。以此论证了在温度较低时 ,固体物质在颗粒间流体中的溶解的浓度的时间变化是受固体岩石中应力梯度和应变能梯度控制的 相似文献
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充填体的变形破坏、能量耗散与围压的变化密切相关,通过开展不同灰砂配比、浓度的充填体单轴、三轴压缩试验,基于系列试验结果,研究了不同围压加载阶段充填体的变形特征、破坏模式及能量耗散与围压的内在关系。结果表明,随着围压的增加,充填体的峰值应变随之增大,且两者呈线性相关;低围压时充填体呈现脆性破坏,表现为应变软化特征,随着围压增大,充填体由脆性向应变硬化转化,灰砂比越大、浓度越高,充填体发生脆-延性的临界围压值越大。充填体的破坏裂纹发展形式各异,大致可分为单一、平行、交叉和复合4种类型;宏观破坏表现主要呈“X”状、“Y”状剪切模式,破坏面的类型主要分为：直线式光滑摩擦面、圆弧式破碎摩擦面、直线式破碎摩擦面以及台阶式破碎摩擦面。充填体的峰值强度与围压也呈正线性相关,内摩擦角对灰砂比的敏感性要高于浓度。围压的增大能够相当程度上提高充填体各阶段的应变能,峰前、峰后能耗量、单位体积变形能以及总能耗与围压皆呈正相关性。 相似文献
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泄洪雾雨区裂隙岩质边坡饱和-非饱和渗流场与应力场耦合分析 总被引：4，自引：0，他引：4
岩质滑坡除与地质条件、降雨等因素有关外,泄洪雾雨也成为其不可忽视的催化剂。通过裂隙岩体渗透性与应力关系,裂隙岩体的弹塑性本构关系以及渗流场的控制方程,建立起饱和非饱和渗流场与应力场耦合的等效连续介质模型。编制了有泄洪雾雨影响的饱和-非饱和渗流与应力耦合三维有限元程序,通过迭代求解达到两场耦合目的。以实际工程为例,根据边坡的地表信息、开挖信息、岩层分界信息以及排水洞和帷幕信息等,建立起边坡地质模型。通过耦合计算,详细分析了耦合后边坡岩体的变形、应力以及塑性区等。计算结果表明,雾雨区的边坡稳定与渗流场变化有着重要关系,在评价边坡稳定与否时,要考虑渗流场对其影响。计算成果为实际工程的安全评价提供了一定的科学依据。 相似文献
15.
Thermal recovery from a hot dry rock (HDR) reservoir viewed as a deformable fractured medium is investigated with a focus on the assumption of local thermal non‐equilibrium (LTNE). Hydraulic diffusion, thermal diffusion, forced convection and deformation are considered in a two‐phase framework, the solid phase being made by impermeable solid blocks separated by saturated fractures. The finite element approximation of the constitutive and field equations is formulated and applied to obtain the response of a generic HDR reservoir to circulation tests. A change of time profile of the outlet fluid temperature is observed as the fracture spacing increases, switching from a single‐step pattern to a double‐step pattern, a feature which is viewed as characteristic of established LTNE. A dimensionless number is proposed to delineate between local thermal equilibrium (LTE) and non‐equilibrium. This number embodies local physical properties of the mixture, elements of the geometry of the reservoir and the production flow rate. All the above properties being fixed, the resulting fracture spacing threshold between LTNE and LTE is found to decrease with increasing porosity or fluid velocity. The thermally induced effective stress is tensile near the injection well, illustrating the thermal contraction of the rock, while the pressure contribution of the fracture fluid is negligible during the late period. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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岳豪杨胜利翟瑞昊张燊崔轩 《岩土力学》2023,(4):1230-1244
含砂岩石是发生突水溃砂灾害前在高位关键层形成的特殊岩石,其强度与力学性质均与普通岩石不同,决定着高位关键层的稳定性。研究发现：不同裂隙角的裂隙岩石与含砂岩石具有不同的特征应力,且随着裂隙角的增加,裂隙岩石与含砂岩石的起裂应力、损伤应力和峰值应力均增加,双峰应力先增加后减小。相同裂隙角下的含砂岩石各特征应力均小于裂隙岩石,说明砂体对岩石特征应力具有弱化效应。从破坏形态来看,裂隙岩石易呈现翼形拉伸裂隙,含砂岩石在低裂隙角（30°）条件下形成拉伸裂隙,高裂隙角（60°）条件下易形成剪切裂隙,表明砂体进入岩石裂隙后对岩石具有剪切效应。同时建立了充砂力学模型,指出了含砂岩石强度小于裂隙岩石的原因是砂体降低了岩石的摩擦系数。根据声发射累计振铃计数定义了岩石损伤量并分析了含砂岩石致灾机制,现场溃砂灾害可分为4个阶段：弹性变形阶段、裂隙扩展阶段、蓄砂储能阶段、溃砂释能阶段。最后利用PFC2D验证了裂隙岩石与含砂岩石的差异性,分析了不同类型岩石的能量演化规律。研究结果可作为煤矿顶板突水溃砂现象的前兆信息识别,有助于指导突水溃砂工作面的安全生产。 相似文献
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能量相互转化过程的综合作用导致了岩石破坏,而其破坏的根本原因是岩石中储存的应变能的释放。对中低应变率加载条件下岩石尺寸效应能量特征的研究结果表明：花岗岩破坏时吸收的总能量U、弹性应变能Ue以及损伤应变能Ud均随试件尺寸的增长而降低;岩石强度与岩石中储存的能量有关,尤其与弹性储能有关,即弹性应变能愈高,岩石强度越大;试件长度由50 mm 变为125 mm时,弹性储能逐渐降低,岩石破坏形态从劈裂破坏变为剪切破坏,大尺寸时局部化变形明显。能量是不同应变率加载条件下岩石破坏细微观及宏观特征存在差异的内在动力;亦是导致岩石强度存在尺寸效应的本质动因。 相似文献
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从内能角度分析发生蠕变的机制,基于应变能理论,采用Perzyna黏塑性理论与西原正夫元件模型相结合,建立了一种能描述衰减蠕变、稳定蠕变和加速蠕变3个阶段全过程的蠕变统一本构模型。该模型考虑了应力状态对加速蠕变的影响,通过定义加速蠕变临界应变能密度值可以有效判断加速蠕变发生时刻,并在统一蠕变本构模型基础上进行简化,采用Drucker-Prager（D-P）屈服准则结合相关联流动法则,用过屈服应力比反映加速阶段蠕变应变速率变化,建立了一个实用的能预测加速蠕变并能反映蠕变3阶段全过程的简化蠕变本构模型,结果表明,数值模拟结果与试验数据基本吻合,研究成果为岩石蠕变断裂过程研究提供了一种新的思路。 相似文献
20.
近距离上保护层开采瓦斯运移规律数值分析 总被引：10，自引：1，他引：9
采动裂隙是瓦斯运移的通道,搞清瓦斯运移规律是瓦斯治理的前提。在考虑岩石动态破坏过程和含瓦斯煤岩渗流-应力-损伤耦合的基础上,结合平煤五矿实际地质条件和开采工艺,建立了数值计算模型,应用RFPA-Gas程序模拟了近距离上保护层采动顶底板岩层变形破坏、裂隙演化规律与瓦斯运移规律。模拟结果较好地再现了保护层开采过程中煤岩层应力变化、顶底板损伤及裂隙演化过程,得到了上覆岩层移动的“上三带”（冒落带、裂隙带和弯曲下沉带）和底板变形的“下两带”（底板变形破坏带和弹塑性变形带）。得到了被保护层瓦斯流量分布、瓦斯压力分布和透气系数的变化规律,卸压煤层瓦斯透气性增大了2 500倍,得到了煤壁下方压缩区和膨胀区之间的张剪瓦斯渗流通道,并将保护层底板压缩区和膨胀区的瓦斯渗流特征提炼出来：压缩区对应的是渗流减速减量区、膨胀区由卸压膨胀陡变区和卸压膨胀平稳区组成,分别对应着渗流急剧增速增量区和渗流平稳增量区。指出卸压膨胀陡变区是瓦斯突出危险区,为近距离保护层开采瓦斯治理指明了方向。实践表明,瓦斯治理效果显著。 相似文献