共查询到20条相似文献，搜索用时 281 毫秒
1.
2.
基于Zienkiewicz提出的非饱和多孔介质波动理论,考虑两相流体和固体颗粒的压缩性以及惯性、黏滞和机械耦合作用,采用半解析的方法获得了一类典型边界条件下单层非饱和多孔介质一维瞬态响应解。首先推导出无量纲化后以位移表示的控制方程,并将其写成矩阵形式;然后,将边界条件齐次化,求解控制方程所对应的特征值问题,得到了满足齐次边界条件的特征值和相对应的特征函数。根据变异系数法并利用特征函数的正交性,得到了一系列仅黏滞耦合的关于时间的二阶常微分方程及相应的初始条件。在此基础上,运用精细时程积分法给出了常微分方程组的数值解。最后,通过若干算例验证了结果的正确性并探讨了单层非饱和多孔介质一维瞬态动力响应的特点。该方法可推广应用于其他典型的边界条件。 相似文献
3.
4.
引用了流体饱和两相多孔介质的动力控制方程分析半空间埋置动点源荷载问题的位移和变形。经过Laplace Hankel变换 ,控制方程化成常微分方程组。利用数学软件mathmatic对上述方程组求解 ,可以得到单层砂土的传递矩阵。分析过程中 ,假设在两层面上 ,位移与应力相互连续 ,可以借鉴有限元的思想进行耦合计算。这样就获得了在饱和砂土中施加竖向动荷载问题的Laplace Hankel变换解 ,其最终的解还需要通过Laplace Hankel逆变换得到 相似文献
5.
利用点荷载,作用于半无限空间的Mindlin位移解,考虑锚杆与土体界面的渐进破坏过程,推导出界面摩阻力的微分方程解析解。编制了相应的计算程序,把计算结果和现场试验值进行比较,结果较为吻合,二者的数据都表明,随着锚头拉力的增加,土-锚杆摩阻力峰值逐渐向锚杆末端转移,而锚杆前端则发生部分范围的滑移。然后,利用所求得的解析解,研究了土体弹性模量、锚杆孔径对锚杆摩阻力分布的影响,可见土体弹性模量越大,则界面上的摩阻力越容易达到峰值,从而产生破坏,而锚杆孔径越大,则界面上的摩阻力上升越慢,可延缓破坏过程。 相似文献
6.
利用弹性矩形板与多层地基表面的竖向位移协调条件与光滑接触条件,由横观各向同性多层地基应力与位移非耦合的传递矩阵解,推导出弹性矩形板下竖向应力和位移的解析解。在此基础上,编制了相应的程序,并进行了数值计算。计算结果表明：矩形板刚度对板底竖向位移及板中心下的竖向应力有着较为显著的影响;板底竖向位移及板中心下的竖向应力随着板刚度的增加而减小,相同荷载作用下横观各向同性地基与均匀各向同性地基模型的计算结果差异较大,实际工程中很有必要采用更符合土体性质的横观各向同性地基模型 相似文献
7.
单层不可压缩饱和多孔介质一维瞬态响应精确解 总被引：1，自引：0，他引：1
基于Biot理论,考虑惯性、黏滞和机械耦合作用,假定固体颗粒和流体均不可压缩,得到了表面任意竖向荷载作用下单层饱和多孔介质一维瞬态响应的精确解。导出了以固体骨架位移表示的无量纲控制方程,并将边界条件齐次化。求解对应无黏滞耦合作用的特征值问题,得到一组满足齐次边界条件、关于空间坐标的正交函数基。利用变异系数法和基函数的正交性,得到一系列相互解耦的、关于时间的二阶常微分方程及相应的初始条件,并采用状态空间法求解常微分方程,得到位移分量。对整体平衡方程关于空间坐标积分,根据边界条件可确定总应力,并进而求得孔隙压力。通过算例验证所得解法的正确性 相似文献
8.
爆管法是目前正在兴起的一种非开挖管道修复前沿技术。利用建立弹塑性力学模型的方法对爆管法施工过程中钻孔孔壁进行力学分析,依据几何方程、变形协调条件和本构方程求解施工作业过程中的应力分布状态,得到孔壁应力解和径向位移解为爆管法施工提供一定理论分析和技术参考。 相似文献
9.
竖向圆形荷载作用下弹性半空间问题的位移和应力解是桩基分析的基础。利用Hankel积分变换,首先导出了弹性地基半空间位移与应力的积分形式的通解。通过适当地引入边界条件和界面位移和应力的连续条件,求得了内部作用竖向圆形荷载时弹性地基半空间位移与应力的积分形式解。在此基础上,给出了不同深度处荷载作用投影范围内竖向位移和竖向正应力的平均值。数值结果验证了解析解的正确性。 相似文献
10.
假设锚杆为与周围介质相同的材料,视锚杆作用的岩土体为弹性半空间位移体;基于Mindlin位移解,求出集中力作用下周围岩土体沿锚固体的轴向位移;根据压力型锚杆锚固段的受力状态,计算锚固体在轴向荷载作用下压缩变形,利用锚固体与周围岩土体变形协调假定,推导出锚固段轴向应力和剪应力分布的理论解。经过与已有现场试验实测数据对比分析,验证了理论解的可行性,并在此基础上讨论了相关岩土参数对锚固段轴向应力和剪应力的影响。锚杆现场试验和理论分析结果表明:压力型锚杆的锚固段所受轴向应力和剪应力与锚固力成正比;压力型锚杆的锚固段所受剪应力的分布形式受周围岩土体弹模、泊松比以及锚固体与周围岩土体界面的内摩擦角等因素的影响。其中周围岩土体的弹模影响最大。 相似文献
11.
Wang Jing-tao 《岩土力学》1979,1(2):73-80
We applied the theory of interacting continua in dynamics of composite materials to study the problem of cylindrical wave propagation in layered rock mass .A set of differential equations has been derived to determine displacements and stresses in
Each layer and to describe the geometrical dispersion of cylindrical wave propagation in layered rock mass .The corresponding frequency relation has been obtained . 相似文献
12.
近些年来,随着复合材料生产的发展,复合材料力学性质的理论和实验研究也相应地发展起来了.由于许多岩体是复合体,因此运用复合材料力学理论的基本原理和方法来处理岩石力学问题是很有意义的,它更能比较真实地反映岩体的力学特性.最近,有些人已开始做了这方面的研究工作. 相似文献
13.
危岩是三峡库区典型的地质灾害类型之一,而主控结构面受荷断裂扩展是危岩发育成灾的关键核心。将危岩主控结构面类比为宏观裂纹,利用扩展有限元法在模拟裂纹扩展方面的优势,基于考虑裂纹面水压力作用的虚功原理推导出了采用扩展有限元法分析水力劈裂问题的控制方程,给出了危岩主控结构面水力劈裂问题的扩展有限元实现方法,对重庆万州太白岩危岩主控结构面的水力劈裂进行了数值模拟分析。计算结果表明：暴雨是威胁危岩稳定性的最敏感因素,随着裂隙水压力上升,裂端拉应力会急剧升高,危岩的稳定性降低;I型裂纹扩展是危岩主要的结构面扩展形式,结构面一旦发生开裂,将处于非稳定扩展状态。 相似文献
14.
水力压裂作为煤层强化增透技术的一种,其应力演化特征及裂隙形态与扩展范围的判断尤为重要。采用离散元数值方法,以导向压裂为背景,建立水力压裂流固耦合模型;通过应力路径、裂纹热点图等手段,探究水力压裂过程中压裂排量、泊松比、天然裂隙密度对应力演化和裂隙演化的影响及其细观规律。结果表明:不同压裂排量下的应力演化方向及最终应力路径曲线形状有着明显的不同,低排量下裂隙附近的应力比值逐渐增大,而在高排量下先增大后减小;煤层泊松比越大,平均压裂半径越低,但对起裂时间及裂隙的扩展形态影响不明显;天然裂隙的发育情况对水力裂隙的扩展起着关键性作用,高裂隙发育煤层水力裂隙扩展的方向性无法预测,应力演化方向会出现反转现象;压裂过程中不同区域的应力演化特征能够反映出裂隙的扩展状态,现场可通过监测压裂区域附近应力变化,判断水力压裂缝网的扩展范围。 相似文献
15.
One proposed geothermal heat extraction scheme relies on water circulation in a large vertical crack created by hydraulic fracturing in a hot dry impermeable rock mass. Water flow, heat convection and crack opening widths are analysed by finite elements. Governing field equations of the problem are first set up rigorously and then various small terms are identified and neglected, retaining the effects of pressure gradient, buoyancy, velocity head (kinetic energy) and head loss due to viscous friction in the water flow equation, and the effects of heat convection in water and heat conduction in rock in the heat transfer equation. The finite element scheme for water flow is based on a variational principle that is typical for diffusion problems, and for heat transfer it is based on the method of least-square residuals. The system of differential equations is highly non-linear. The non-linear terms and coefficients are treated in the fiaite element analysis as constant; the finite element analysisof, the steady-state pressures, fluxes and temperatures is then iterated, evaluating all non-linear terms and coefficients on the basis of the solution obtained in the previous iteration. Numerically calculated fields at various times after the start ofcooling are presented. They indicate some features favourable for the geothermal scheme, such as formation of eddy currents, and downward flux of water toward hotter rock. However, other important questions would have to be solved to gain full understanding, of this proposed geothermal scheme. 相似文献
16.
储层岩体中的天然结构面对水力压裂缝网改造具有重要的影响。本文采用真实破裂过程分析软件RFPA2D-Flow,在考虑岩体非均质性和岩体渗流-应力-损伤破裂特性的基础上,对不同尺度天然结构面影响的水力压裂裂缝扩展与演化行为进行了模拟分析和讨论,研究结果表明:（1）当水力裂缝遇天然非闭合裂隙时,在水力裂缝靠近非闭合裂隙区间形成拉张应力区,水力裂缝与区间非闭合裂隙间微元体累进性张拉破坏是导致水力裂缝与非闭合裂隙贯通的主要机制;（2）层理等优势结构对水力压裂裂缝扩展及缝网形态影响十分显著,当最大主应力方向与层理面走向小角度相交时,层理结构面对水力裂隙的扩展起主要作用,当最大主应力方向与层理面走向大角度相交时,最大主压应力与层理面共同对缝网扩展起主导作用,随着优势结构面的增多和差应力的增大,水力压裂形成的缝网范围和复杂性程度随之增大;（3）储层水力压裂是一种局部范围内的短暂动力扰动过程,尽管断层的存在可以极大地影响水力裂缝的扩展模式,增大水力裂隙扩展高度,但相比于储层埋深,水力压裂对断层封闭性的破坏范围和断层活动性的扰动程度十分有限。 相似文献
17.
Shujun Peng Zhennan Zhang Jianye Mou Bing Zhao Zhiyuan Liu Jiading Wang 《国际地质力学数值与分析法杂志》2019,43(1):441-460
The improved element partition method (IEPM) is a newly developed fracture simulation approach. IEPM allows a fracture to run across an element without introducing extra degrees of freedom. It can also simulate any number of fractures in a prescribed mesh without remeshing. In this study, the IEPM is extended to hydraulic fracture simulation. First, the seepage and volumetric storage matrix of a cracked element are derived using virtual nodes (the intersection points of a crack with element edges). Subsequently, the fully coupled hydromechanical equation is derived for this cracked element. To eliminate the extra degrees of freedom (virtual nodal quantities), the water pressure and displacement of the virtual nodes are associated with their adjacent nodes through least squares interpolation. Finally, the fully coupled equation in terms of nodal quantities is obtained. The verification cases validate the method. By using this method, the field-scale hydraulic fracturing process is well simulated. The proposed approach is simple and efficient for field-scale hydraulic fracture simulation. 相似文献
18.
随着扩展有限元理论的深入研究,利用扩展有限元方法模拟水力压裂具有了一定的可操作性。相比于常规有限元方法,XFEM方法具有计算结果精度高和计算量小的优点。但是,如何模拟射孔孔眼、如何模拟流体与岩石相互作用以及分析水力裂缝的扩展规律仍然是难题。以研究水力压裂裂缝扩展规律为目的,建立了岩石多孔介质应力平衡方程、流体渗流连续性方程和边界条件。通过有限元离散化方法对耦合方程矩阵进行处理。通过富集函数定义初始裂缝（射孔孔眼）,选择最大主应力及损伤变量D分别作为裂缝起裂和扩展判定准则,利用水平集方法模拟水力裂缝扩展过程。数值模拟结果显示：增加射孔方位角、压裂液排量和减小水平地应力差,起裂压力上升;黏度对起裂压力无明显影响。增加射孔方位角、压裂液排量、黏度和减小水平地应力差值有助于裂缝宽度的增加。增加水平地应力差值、压裂液排量和减小射孔方位角以及压裂液黏度有助于裂缝长度增加,反之亦然。基于ABAQUS的水力裂缝扩展有限元法可对不同井型和诸多储层物性参数及压裂施工参数进行分析,且裂缝形态逼真,裂缝面凹凸程度清晰,结果准确。此研究可作为一种简便有效研究水力压裂裂缝扩展规律的方法为油田水力压裂设计与施工提供参考与依据。 相似文献
19.
Bingxiang Huang Pengfeng Li Jian Ma Shuliang Chen 《Rock Mechanics and Rock Engineering》2014,47(4):1321-1334
Because of the advantages of integrating water pressure blasting and hydraulic fracturing, the use of hydraulic fracturing after water pressure control blasting is a method that is used to fully transform the structure of a coal-rock mass by increasing the number and range of hydraulic cracks. An experiment to study hydraulic fracturing after water pressure blasting on cement mortar samples (300 × 300 × 300 mm3) was conducted using a large-sized true triaxial hydraulic fracturing experimental system. A traditional hydraulic fracturing experiment was also performed for comparison. The experimental results show that water pressure blasting produces many blasting cracks, and follow-up hydraulic fracturing forces blasting cracks to propagate further and to form numerous multidirectional hydraulic cracks. Four macroscopic main hydraulic cracks in total were noted along the borehole axial and radial directions on the sample surfaces. Axial and radial main failure planes induced by macroscopic main hydraulic cracks split the sample into three big parts. Meanwhile, numerous local hydraulic cracks were formed on the main failure planes, in different directions and of different types. Local hydraulic cracks are mainly of three types: local hydraulic crack bands, local branched hydraulic cracks, and axial layered cracks. Because local hydraulic cracks produce multiple local layered failure planes and lamellar ruptures inside the sample, the integrity of the sample decreases greatly. The formation and propagation process of many multidirectional hydraulic cracks is affected by a combination of water pressure blasting, water pressure of fracturing, and the stress field of the surrounding rock. To a certain degree, the stress field of surrounding rock guides the formation and propagation process of the blasting crack and the follow-up hydraulic crack. Following hydraulic fracturing that has been conducted after water pressure blasting, the integrity of the sample is found to be far lower than after traditional hydraulic fracturing; moreover, both the water injection volume and water injection pressure for hydraulic fracturing after water pressure blasting are much higher than they are for traditional hydraulic fracturing. 相似文献
20.
Hydraulic fracturing is the method of choice to enhance reservoir permeability and well efficiency for extraction of shale gas. Multi‐stranded non‐planar hydraulic fractures are often observed in stimulation sites. Non‐planar fractures propagating from wellbores inclined from the direction of maximum horizontal stress have also been reported. The pressure required to propagate non‐planar fractures is in general higher than in the case of planar fractures. Current computational methods for the simulation of hydraulic fractures generally assume single, symmetric, and planar crack geometries. In order to better understand hydraulic fracturing in complex‐layered naturally fractured reservoirs, fully 3D models need to be developed. In this paper, we present simulations of 3D non‐planar fracture propagation using an adaptive generalized FEM. This method greatly facilitates the discretization of complex 3D fractures, as finite element faces are not required to fit the crack surfaces. A solution strategy for fully automatic propagation of arbitrary 3D cracks is presented. The fracture surface on which pressure is applied is also automatically updated at each step. An efficient technique to numerically integrate boundary conditions on crack surfaces is also proposed and implemented. Strongly graded localized refinement and analytical asymptotic expansions are used as enrichment functions in the neighborhood of fracture fronts to increase the computational accuracy and efficiency of the method. Stress intensity factors with pressure on crack faces are extracted using the contour integral method. Various non‐planar crack geometries are investigated to demonstrate the robustness and flexibility of the proposed simulation methodology. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献