长江三峡及邻区板内中强地震的孕震动力学分析

本文在研究长江三峡及邻区地壳─上地幔结构和现今地壳重力场基础上，分析了该区板内中强地震的孕震动力学过程，探讨了整体上相对稳定的长江三峡及邻区孕育和发生中强地震的动力学机制，并提出了该区板内中强地震预测的动力学标志。     

推覆构造滑脱层有限变形力学分析

本文根据推覆构造滑脱层的变形特点,运用以S—R分解定理为基础的有限变形力学理论,研究了断坪与断坡滑脱层的变形场特征。用全量及增量方法逆解求出了变形滑脱层所受的边界外力;利用变形场与应力场的分析结果,给出了推覆构造在拆离时推覆席体的推移距离及作用推力的简捷计算公式。     

Water temperature and conductivity variability as indicators of groundwater behaviour in complex aquifer systems in the south‐east of Spain

Groundwater temperature and electrical conductivity logs were applied in this study to gain an understanding of the hydrogeological behaviour of a complex system. This system, compartmentalized by a large number of fractures, which may even cause geothermal anomalies, is that of the Campo de Dalías in the south‐east of the Iberian Peninsula. In addition to this complexity one must consider the different levels with aquifer properties and their varying lithologies, which in some cases are in direct contact with the sea. Vertical sections based upon the various logs allow lateral correlation to be made between the anomalies detected, and provide information on the existence of both ascending and descending vertical flows, and the inflow of sea water into the system. Analysis of environmental isotopes (¹⁸O and D) indicate the areas of recharge with the greatest flow velocity. No seasonal variation in the isotopes was observed, which suggests that the residence time of the groundwater in the aquifer is several years. Radiocarbon dating gave estimates of generally long residence times, although in some sectors it is possible to detect the current recharge based on its tritium content, from rainwater infiltration or seawater intrusion. Copyright © 2002 John Wiley & Sons, Ltd.     

辽河油田曙一区杜84块兴隆台油层构造应力场研究

根据辽河油田已有地层、构造资料，研究了杜84块构造格架、主要断裂特点，在此基础上,建立了构造应力场模拟的三维地质模型，用3D-σ软件进行了构造应力场三维有限元模拟研究。其结果表明，杜84块油层受构造应力状态为最大和中间主应力近水平，最小主应力垂直。在此应力场作用下，区内断层运动方式为正断兼水平扭动。三维有限元模拟计算结果表明，沿断层带均发生压应力和剪应力集中现象,从而有利于断层发生扭张性运动。位移分析表明，有明显的呈阶梯状组合的正断位移。据破坏率分析，在现有应力场作用下，油层所在岩体局部会产生裂缝。     

A Generalized Backward Euler algorithm for the numerical integration of an isotropic hardening elastoplastic model for mechanical and chemical degradation of bonded geomaterials

An extended version of the classical Generalized Backward Euler (GBE) algorithm is proposed for the numerical integration of a three‐invariant isotropic‐hardening elastoplastic model for cemented soils or weak rocks undergoing mechanical and non‐mechanical degradation processes. The restriction to isotropy allows to formulate the return mapping algorithm in the space of principal elastic strains. In this way, an efficient and robust integration scheme is developed which can be applied to relatively complex yield surface and plastic potential functions. Moreover, the proposed algorithm can be linearized in closed form, thus allowing for quadratic convergence in the global Newton iteration. A series of numerical experiments are performed to illustrate the accuracy and convergence properties of the algorithm. Selected results from a finite element analysis of a circular footing on a soft rock layer undergoing chemical weathering are then presented to illustrate the algorithm performance at the boundary value problem level. Copyright © 2002 John Wiley & Sons, Ltd.     

靖远地区大厚度黄土地基浸水湿陷过程及土中竖向应力特征试验研究

为了研究靖远大厚度黄土在浸水条件下的水分入渗规律和自重湿陷变形特征,在中兰铁路沿线的靖远北站黄土自重湿陷场地进行了不打注水孔的现场浸水试验,监测并分析了地表及地下湿陷变形、试坑周围裂缝、含水率和土中竖向应力变化情况,对水分扩散规律、自重湿陷特性和土中竖向应力变化规律进行了研究,并对地区修正系数β0值和浸润角进行了探讨。结果表明：体积含水率变化分为浸水稳定（2个）、快速增加（1个）和缓慢增加（1个）共4个阶段;浸水过程中,水分在21m处竖向入渗加快、径向扩散减缓,湿润峰最终形态呈现为椭圆状。根据探井和钻孔含水率测试结果,推算出浸润角最大为41°。该场地黄土自重湿陷过程历经剧烈湿陷、缓慢湿陷和固结稳定3个阶段。试验结束时共计发展了13圈环状裂缝,裂缝最远处距试坑边缘26m。根据室内试验和现场测试结果,建议地区修正系数沿土层深度进行修正,0～10m内β0值取1.05,10～27 m内β0值取0.95。在地表至21 m深度范围内,地基土浸水饱和且湿陷充分,土中竖向应力沿深度呈线性增加,土中竖向应力接近饱和自重应力,21m以下的地基土未能充分湿陷,土中竖向应力逐渐减小。该研究成果可应用于中兰铁路...     

交叉裂隙岩体裂纹扩展试验及混合有限-离散元数值模拟研究

对预制交叉裂隙岩石试样进行裂纹扩展试验,研究了裂纹萌生、扩展、聚合过程,分析了主裂隙和轴向载荷夹角及主次裂隙夹角对裂纹起裂应力和聚合应力的影响,并用混合有限元-离散元程序,即图形处理器并行化的3D Y-HFDEM代码对试验进行了仿真计算,实现了岩石破坏从连续介质向非连续介质的过渡,对裂纹类及损伤破坏模式进行了识别,捕捉到了试验中难以发现的现象。研究表明：随主裂隙与轴向载荷夹角增加,裂纹聚合区的拉伸裂纹数量增加;裂纹起裂和聚合应力与主裂隙与轴向载荷夹角成正比;主次裂隙夹角增加,岩石的破坏模式由拉伸破坏转为剪切破坏,交叉裂隙加剧岩石破碎程度;主裂隙尖端萌生扩展的拉伸-剪切混合裂缝引起的破坏在岩石破坏中占主导地位,是导致岩体失去承载能力的主控裂纹;混合有限元-离散元仿真软件GPGPU并行化的3D Y-HFDEM IDE在岩石裂纹扩展研究中具有优势,可以捕捉实验室难以发现的损伤断裂类型,可以作为岩石裂纹扩展研究的有力工具。     

卸荷-增孔压条件下花岗岩残积土的力学特性

建（构）筑物因土中孔隙水压力升高而失稳破坏的情形屡见不鲜,常剪应力增孔压试验是相关研究的常用手段,但迄今鲜见考虑施工期开挖卸荷影响的试验研究。为探究初始卸荷对花岗岩残积土增孔压过程力学行为的影响,在常规增孔压试验中增加了初始卸荷阶段,开展了一系列考虑初始卸荷程度和卸荷滞时影响的卸荷-增孔压试验,分析土体变形、屈服和强度特性的初始卸荷效应与卸荷滞时效应,并与常规增孔压试验结果对比以揭示初始应力路径的影响。试验结果表明：增孔压过程的变形发展具有明显的阶段性,土体屈服后因其剪胀潜势和变形迅速而产生负超静孔压增量,有效平均应力转而增大;初始卸荷对增孔压过程土体力学性能具有明显的劣化作用,表现为刚度与屈服强度均随初始卸荷程度的增大而衰减;与被动压缩这种“加荷”式应力路径相比,初始卸荷的不利影响更为显著;土体力学性能的劣化随卸荷滞时的增长而加剧;屈服摩擦角随初始卸荷程度的增大逐渐减小,但始终大于临界状态摩擦角。     

张家口—渤海地震带岩石圈磁场时空变化特征

利用2016—2018年3期华北地区流动地磁矢量原始测量资料, 经数据计算获得2期华北地区和张家口—渤海地震活动带及邻区岩石圈磁场时空变化模型。 研究结果显示: 张家口—渤海地震带岩石圈磁场变化空间分布不均匀, 具有明显的分区特征, 在张家口段(西段)与北京段(中西段)分界处和北京段(中西段)与唐山段(中东段)分界处岩石圈磁场各要素具有明显的异常变化, 如水平矢量存在转向和幅值变化, 磁偏角与磁倾角具有正负异常高梯度带的特征, 这与张家口—渤海地震带构造分段性特征密切相关。 张家口—渤海地震带位于燕山块体与华北平原块体之间, 两者运动的平动速率之差是张家口—渤海地震带左旋走滑的直接动力来源, 而各断裂带左旋走滑速率之差很可能是岩石圈磁场空间变化分段性分布的主要原因。