Simulation of hydraulic fracture propagation near a natural fracture using virtual multidimensional internal bonds     

Z. Zhang  A. Ghassemi 《国际地质力学数值与分析法杂志》2011,35(4):480-495

A virtual multidimensional internal bond (VMIB) model developed to simulate the propagation of hydraulic fractures using the finite‐element method is formulated within the framework of the virtual internal bond theory (VIB) that considers a solid as randomized material particles in the micro scale, and derives the macro constitutive relation from the cohesive law between the material particles with an implicit fracture criterion. Hydraulic pressure is applied using a new scheme that enables simulation of hydraulically driven cracks. When the model is applied to study hydraulic fracture propagation in the presence of a natural fracture, the results show the method to be very effective. It shows that although the in situ stress ratio is the dominant factor governing the propagation direction, a natural fault can also strongly influence the hydraulic fracture behavior. This influence is conditioned by the shear stiffness of the fault and the distance to the original hydraulic fracture. The model results show that when the fault is strong in shear, its impact on hydraulic fracture trajectory is weak and the hydraulic fracture will likely penetrate the fault. For a weak fault, however, the fracture tends to be arrested at the natural fault. The distance between the fault and the hydraulic fracture is also important; the fault influence increases with decreasing distance. The VMIB does not require selection of a fracture criterion and remeshing when the fracture propagates. Therefore, it is advantageous for modeling fracture initiation and propagation in naturally fractured rock. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

短脉冲激光在实验室天体物理方面的研究进展     

孙嘉宁  袁大伟  王菲鹿 《天文研究与技术》2021,(2):248-254

随着啁啾脉冲放大技术(Chirped Pulse Amplification,CPA)的飞速发展,激光功率密度实现了飞跃式的提升,利用短脉冲激光开展实验室天体物理研究的条件日趋成熟。短脉冲激光与靶相互作用可以产生相对论粒子(正负电子、质子、中子等)和高能电磁辐射(X射线、γ射线),这些粒子和辐射的产生过程与天体中的某些物理现象相对应。介绍了利用短脉冲激光开展实验室天体物理的研究进展,重点介绍了核天体物理、空心离子光谱学、相对论无碰撞冲击波以及等离子体状态诊断等。  相似文献   

GDCORS多星系统定位平台测试与分析          下载免费PDF全文

邓思胜  刘文建  胡斯斌 《全球定位系统》2020,45(2):74-79

广东省连续运行卫星定位服务系统(G DCORS)建成了兼容多星系统的北斗地基增强平台,组织开展了新平台与原平台的外业测试.并从内符合精度评定、重复性精度评定、外符合精度、初始化时长等方面对网络实时动态(RTK)定位结果进行了统计和比对分析.测试结果表明,新平台能够提供高可靠性、高精度的网络RTK服务.文中研究结果可为GDCORS用户使用新/原平台提供实际应用参考.  相似文献   

Internal erosion in granular media: direct numerical simulations and energy interpretation          下载免费PDF全文

Luc Sibille  Franck Lominé  Philippe Poullain  Yacine Sail  Didier Marot 《水文研究》2015,29(9):2149-2163

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基于多源卫星遥感数据的安达曼海及其邻近海域内波分布特征分析          下载免费PDF全文

王隽  杨劲松  周礼英  贺双颜  贺治国  肖清梅  刘安国  许明光 《海洋学研究》2019,37(3):1-11

安达曼海是内波频繁发生的海区之一,对其内波的研究是当今海洋研究的热点。本文利用2013—2016年间覆盖整个安达曼海的3 000多幅Terra/Aqua MODIS、GF-1、Landsat-8、Sentinel-1 等卫星遥感图像,从中提取和解译了内波波列线和波向信息,得到安达曼海海洋内波的时间分布特征,并绘制了内波空间分布图。结果表明,安达曼海及其邻近海域内波主要出现在4个区域:苏门答腊岛以北海域、安达曼海中部海域、安达曼海北部海域以及尼科巴群岛以西海域,尺度较大的内波主要分布在苏门答腊岛以北海域和安达曼海中部海域。在时间分布上,2013—2016年间安达曼海内波的年发生次数相近;在热季、雨季及冬季遥感都能观测到内波的发生;2-4月遥感观测到的内波最多,其次为8、9月,7月遥感观测到的内波较少,这可能是由于雨季光学影像受云影响,安达曼海海域晴空影像过少造成,还需要借助更多的遥感影像进一步证明。在波向上,安达曼海多数内波向岸传播,在苏门答腊岛北部、安达曼海中部海域,内波向东或向东南传播;在安达曼群岛东部,内波向东传播,传播一定距离后与海底地形交互作用,一部分继续向前传播,一部分产生反射,向西南方向传播至安达曼群岛;在尼科巴群岛以西海域,内波由尼科巴群岛向孟加拉湾传播。  相似文献   

Interaction mechanisms among waves,currents and a submerged plate     

《Applied Ocean Research》2019

Wave-induced loads on a submerged plate, representative of submerged breakwater, coastal-bridge deck and a certain type of wave energy converter, in a uniform current are investigated in this study using fully nonlinear numerical wave tanks (NWTs) based on potential flow theory. The coupling effect of wave and current is explored, and the underlying interaction mechanisms of the hydrodynamic forces are described. The presence of a background current modifies the frequency dispersion. It produces changes of the water-surface elevation, and also has an effect on wave-induced loads. Depending on the nonlinearity, higher harmonic wave components are generated above the submerged plate. These contribute to the wave forces. It is found that the horizontal and the vertical force, hence the moment, are affected in the opposite way by the currents. The Doppler shifted effect dominates the vertical force and the moment on the plate. Whereas, the Doppler shifted effect and the generation of higher wave harmonics play opposite roles on the horizontal forces. The contribution of 2^nd order harmonics is found to be up to 30% of the linear component. The current-induced drag force, represented by the advection term ρU∂φ/∂x in the pressure equation, is found to lead to a decrease in the moment for the most range of wavelengths considered, and an increase in the moment for a small range of longer waves.  相似文献   

考虑桩间土体抗滑作用的单排抗滑桩受力计算方法          下载免费PDF全文

肖世国 《中国地质灾害与防治学报》2020,31(1):89-94

为了充分考虑桩间距范围内滑体对抗滑桩受力的影响,从单排抗滑桩加固边坡的整体稳定角度出发,在采用传递系数法分析指定设计安全系数情况下抗滑桩的内力时,提出对一个桩间距范围内的加固坡体进行整体分析,将抗滑桩所在部位单独划分条块,该条块包括桩体受荷段及其两侧桩间距范围内的滑体。推导了与此分析模型相应的桩体受荷段底端内力计算公式,并给出了在滑坡推力线性分布条件下作用于受荷段的净滑坡推力计算表达式。分析结果显示,在不考虑与完全考虑受荷段两侧桩间距范围内滑体抗力作用时,得到是桩体内力及位移的上、下边界值。实例分析进一步表明,理论分析与数值模拟结果具有良好的一致性。所提出的方法比传统方法更有利于抗滑桩设计的经济性。  相似文献   

Analytical solution for longitudinal seismic response of long tunnels subjected to Rayleigh waves     

Yusheng Yang  Haitao Yu  Yong Yuan  Mi Zhao 《国际地质力学数值与分析法杂志》2020,44(10):1371-1385

The longitudinal seismic response of a long tunnel subjected to Rayleigh waves is investigated in this paper. The tunnel is assumed to be infinitely long, has a uniform cross section, and rests on a viscoelastic foundation. The free-field deformation under Rayleigh waves traveling parallel to the tunnel axis is decomposed into two directions, namely, the axial motion and the vertical motion, and transformed into dynamic loads imposed on the tunnel. Based on the Fourier and Laplace integral transform techniques, the governing equations of tunnels are simplified into algebraic equations, and the analytical solutions are obtained with the convolution theorem. The final solutions of the tunnel responses in terms of deflection, velocity, acceleration, axial force, bending moment, and shear force are investigated. The proposed solution is verified by comparison of its results and those from the finite element program ABAQUS. Further parametric analysis is carried out to investigate the influence of soil-structure relative stiffness ratio and wave frequency on dynamic longitudinal responses of the tunnel.  相似文献   

Wave energy conversion under constrained wave-by-wave impedance matching with amplitude and phase-match limits     

《Applied Ocean Research》2019

This paper investigates an approach to limit the fullness of ‘tuning’ provided by wave-by-wave impedance matching control of wave energy devices in irregular waves. A single analytical formulation based on the Lagrange multiplier approach of Evans [1] is used to limit the velocity amplitude while also limiting the closeness of the phase match between velocity and exciting force. The paper studies the effect of the present technique in concurrently limiting the device velocity and the required control/actuation force. Time domain application requires wave-profile prediction, which here is based on a deterministic propagation model. Also examined in the time domain is the effect of possible violation of the displacement constraint, which for many designs implies impacts at hard stops within the power take-off mechanism. Time domain simulations are carried out for a 2-body axisymmetric converter (with physical end-stops) in sea states reported for a site off the US east coast. It is found that the approach leads to effective power conversion in the less energetic sea states, while as desired, considerable muting of the optimal response is found in the larger sea states. Under the assumptions of this work, the end-stop collisions are found to have a minor effect on the power conversion. The present approach could be used to guide the design of power take-off systems so that their displacement stroke, maximum force, and resistive and reactive power limits are well-matched to the achievable performance of a given controlled primary energy converter.  相似文献   

The influence of the bottom contour on the deformed state of the ice cover due to the motion of the submarine     

《Applied Ocean Research》2019

The authors have previously determined that the effectiveness and failure pattern of the ice cover caused by flexural-gravity waves generated by a submerged body motion near the bottom ice can greatly depend on the depth of the water area. In its turn, the presence of a ledge on the ice surface may affect a wave propagation pattern. This paper presents an experimental study of the bottom contour influence on the deflection and length of flexural-gravity waves. The authors describe a numerical model for the analysis of the deformed state of ice caused by hydrodynamic loads due to a submarine motion, taking into account the bottom contour. The experiments are carried out in the ice tank. The results of calculations and experiments are compared.  相似文献