黄土液化微细观特性试验研究

黄土液化演化过程的微观机理分析是液化防御的科学问题之一。通过微细观及动力学试验探索黄土液化的本质和影响因素。首先用CT细观扫描实验探索黄土渗透液化的细观变化,研究表明土体液面上升的根本原因是弱碱性盐类胶结物的吸水作用导致土样含水面整体上升;试样达到高饱和度,大孔隙周围颗粒间胶结物质破坏后有效应力为零,土层液化。粉土的孔隙尺寸和特殊的胶结物质导致高饱和度。土样微观结构的差异也会影响土的液面上升和破坏强度。针对低黏性粉土、粉质砂土及粉质黏土的三类黄土液化实验分析表明,低黏性粉土动荷加载时间更短,更易于液化,即低粘性粉土液化最为严重,粉质砂土为中等液化,粉质黏土相比其他黄土类别不易液化。电镜扫描土样微观结构参数分析表明,土颗粒周围胶结物质的化学元素比值(Ca/Fe),以及土颗粒粒径分布和孔隙尺寸(孔隙与颗粒比)均影响液化等级,可初步判断液化的强弱。     

大兴安岭两侧控盆断裂域地球物理场基本特征与地质意义

大兴安岭重力梯度带两侧控盆断裂域的地球物理场基本特征与构造属性存在巨大差异,本文通过研究大兴安岭西坡德尔布干断裂以及松辽盆地中央孙吴—双辽断裂附近的重力、大地电磁测深资料,并结合满洲里—绥芬河地学断面(GGT)资料,对德尔布干断裂和孙吴—双辽断裂的控盆作用以及地质意义进行论述.研究结果表明:德尔布干断裂控制了海拉尔—根河盆地的演化,并在区域动力作用下被改造;使断裂深部倾向北西,浅部倾向南东.孙吴—双辽断裂控制着松辽盆地的形成演化,断裂深部倾向近垂直,浅部主要受太平洋西向俯冲和蒙古—鄂霍茨克洋闭合的影响,在浅部产生双向逆冲推覆构造.德尔布干断裂位于盆地的附近,由于岩浆沿断裂的侵入与喷发,因此有利于生烃也有利于形成重要的金属成矿带;孙吴—双辽断裂位于盆地中央,含油气层附近的双向逆冲推覆构造可能更有利于油气的聚集,使松辽盆地成为最重要的产油盆地之一.     

A study on relation between acoustic emission and characteristic displacement field on the sample with multi en echelon structures — The theoretic and experimental explorations of strain gap

Based on the phenomena that the deformation gap was observed before the great Tangshang earthquake, this paper discusses the strain gap according to test and theory. The (strain) patterns were recorded photographically by realtime holographic interferometry and shadow optical method of caustics, as soon as the loading process started. In the meantime, the AE (acoustic emission) signals were recorded by a micro crack information storage-analysis system. According to damage theory and location of micro fracture, we have studied the stain gap and gained: a) It is necessary that strain gap appears under the condition of linear elasticity theory, and its situation is relatively stable, corresponding to stress concentration. b) Micro fractures, which appear initially at area of high stress, occur rarely at the strain gap, and their locations are finally in the zone between the stress concentration area and the strain gap, which indicate the clusters or groups. However, the major macro fracture (final rupture) started from the shadow areas, and then grew quickly towards the strain gaps, which resulted in failure of sample. Foundation item: The Dual Project of China Seismological Bureau (9691309020301), the Specialized Funds for National Key Basic Study (G1998040704), the project for the MOST under contract (2001BA601B02) and Youth Funds for applied basic study of the Science and Technology Bureau of Yunnan Province (98D019Q).     

胶东平度北部山区地下水蓄水构造与开采条件分区

平度北部山区位于胶北隆起西南与胶莱盆地的西北部,属鲁东低山丘陵松散岩、碎屑岩、变质岩类为主水文地质大区,胶莱盆地和胶北低山丘陵两个水文地质亚区。开展1∶5万水文地质调查,综合运用物探、水文地质钻探、抽水试验等工作手段,分析了研究区气象水文、地层构造、水文地质条件,划分了松散岩类孔隙水、碎屑岩类孔隙水、碳酸岩类孔隙水和基岩孔隙水4种地下水类型。分别从地形地貌、地层构造、含水层岩性、补径排条件等因素研究地下水富集规律,新发现东柳圈基岩裂隙水富水地段,可作为小型水源地,为城市应急供水。总结了研究区两种蓄水构造,分别为断裂破碎带型和岩性接触带型。通过分析研究区地下水富集规律和不同蓄水构造类型地下水的补径排特征及赋存情况,分析了地下水开采条件,为平度北部山区的找水打井提供技术支持。     

基于Ruger近似式预测裂缝型储层的可行性研究

叠前纵波方位各向异性检测裂缝是目前应用最为广泛的方法,该方法主要是利用AVAZ地震资料椭圆拟合的长轴与短轴信息来评价裂缝,该方法在具体应用时,认为裂缝型储层AVAZ响应特征的变化仅由各向异性参数决定,而没有考虑非各向异性参数的影响,从而引起裂缝评价的多解性。为提高该技术的裂缝评价精度,从模型分析入手,将模型中各向异性参数及岩性参数设置为概率密度分布函数,然后采用Monte Carlo随机方法进行叠前AVAZ正演模拟。首先,对各向异性参数对椭圆拟合的影响进行简单分析,得出各向异性参数γ对椭圆扁率B/A与各向异性因子B影响最大、δ次之、ε最小。然后,进一步重点分析不同标准差的速度与密度模型的B/A与B响应特征,得出地层的速度与密度的变化在较小范围内时,该技术评价裂缝才具有一定的可行性,其中,地层纵波和横波速度的变化（尤其是纵波速度）对叠前AVAZ响应影响较大,地层密度几乎没有影响,故当横向岩性变化较大时,该方法在评价裂缝型储层时的结果具有一定的不确定性。      

Seismic fracture evaluation of diaphragm joints in welded beam-to-box column moment connections

Steel box columns are widely used in steel building structures in Taiwan due to their dual strong axes. To transfer the beam-end moment to the column, diaphragm plates of the same thickness and elevations as the beam flanges are usually welded inside the box column. The electro-slag welding (ESW) process is widely used to connect the diaphragms to the column flanges in Taiwan because of its convenience and efficiency. However, ESW may increase the hardness of the welds and heat-affected zones (HAZs), while reducing the Charpy-V notch strength in the HAZ. This situation can cause premature fracture of the diaphragm-to-column flange welds before a large plastic rotation is developed in the beam-to-box column joints. To quantify the critical eccentricity and the effectiveness of fracture prediction, this study uses fracture prediction models and finite element model (FEM) analysis to correlate the test results. In this study, two beam-to-box column connection subassembly tests are conducted with different loading protocols and ESW chamber shapes. To implement a fracture prediction model, the material parameters are established from circumferential notched tensile tests and FEM analysis. Test results indicate that the fracture instances can be predicted on the basis of the cumulative plastic deformation in the HAZs. Analytical results indicate that fracture instances and locations are sensitive to the relative locations of the ESW joints and beam flange. Tests also confirm that the possible fracture of the diaphragm-to-column flange joints can be mitigated by enlarging the chamber of the ESW joint.     

Surficial fractures in the Navajo sandstone,south-western USA: the roles of thermal cycles,rainstorms, granular disintegration,and iterative cracking

Deep (> 5 m) sheeting fractures in the Navajo sandstone are evident at numerous sites in southern Utah and derive from tectonic stresses. Strong diurnal thermal cycles are, however, the likely triggers for shallow (< 0.3 m) sheeting fractures. Data from subsurface thermal sensors reveal that large temperature differences between sensors at 2 and 15 cm depth on clear summer afternoons are as great as those that trigger sheeting fractures in exposed California granite. Extensive polygonal patterns in the Navajo sandstone are composed of surface-perpendicular fractures and were produced by contractile stresses. Numerous studies have shown that porewater diminishes the tensile strength of sandstone. Based on our thermal records, we propose that cooling during monsoonal rainstorms triggers polygonal fracturing of temporarily weakened rock. On steep outcrops, polygonal patterns are rectilinear and orthogonal, with T-vertices. Lower-angle slopes host hexagonal patterns (defined by the dominance of Y-vertices). Intermediate patterns with rectangles and hexagons of similar scale are common. We posit that outcropping fractures are advancing downward by iterative steps, and that hexagons on sandstone surfaces (like prismatic columns of basalt) have evolved from ancestral orthogonal polygons of similar scale. In lava flows, fractures elongate intermittently as they follow a steep thermal gradient (the source of stress) as it rapidly moves through the rock mass. In our model, a steep, surficial thermal gradient descends through unfractured sandstone, but at the slow pace of granular disintegration. Through time, as the friable rock on stable slopes erodes, iterative cracking advances into new space. Hexagonal patterns form as new fractures, imperfectly guided by the older ones, propagate in new directions, and vertices drift into a configuration that minimizes the ratio of fracture length to polygon area. © 2020 John Wiley & Sons, Ltd.     

互层胶结土中正断层地震地表破裂位错特征研究

为了解决采用Trimble GX 3D地面激光三维扫描仪分析互层胶结土中正断层地震地表破裂位错特征时,未有效模拟地表垂直和水平位移的基本特征,获取的地表破裂位错特征结果不准确的问题。提出新的互层胶结土中正断层地震地表破裂位错特征研究方法,先构建地震地表弹性位错模型,分析互层胶结土正断层的地表三维断裂特征,得到地表在受到走滑、逆冲和张开错动导致的地表错位变化情况;再通过正断层地震地表破裂离心机试验,获得互层胶结土中正断层地震地表破裂位错特征。试验结果说明,所提方法可有效分析互层胶结土中正断层地震地表破裂位错特征,且破裂点在土体模型中部和中下部的裂缝深度分别为22.4 m和33.4 m,裂缝上的破裂点处于土体模型的中下部时,裂缝的深度越深。     

单裂缝不同传播方向Krauklis波振幅变化的实验研究

裂缝广泛分布于地壳岩石中并具有多尺度的特点,研究地震波在裂缝介质中的传播规律具有重要的科学意义和应用价值.含流体的裂缝中传播的Krauklis波(也曾被称为慢流体波、裂缝波、斯通利导波等)近年来逐渐成为地球物理学界的研究热点之一.本研究利用地震物理模型技术研究横波在单裂缝样品中传播时随传播方向变化的响应特征,在实验室用环氧树脂为基质构建模型样品,一个为不含裂缝的参考样品,一个为含直径30 mm、厚度0.2 mm的薄币状单裂缝的模型,利用0.5 MHz换能器测试了横波在模型中传播时透射信号的特征.实验结果显示在单裂缝样品中透射横波发生了波形的畸变和振幅降低,振幅谱显示透射信号的主频明显降低,在初至横波之后为具有一定能量的尾波.对尾波进行时频分析,发现在方位角较小时尾波能量较弱而方位角较大时尾波能量较强,尾波中信号的主频在0.1 MHz左右,与前人理论和实验研究结果一致.     

京西北地区地震重定位及构造特征

采用双差定位法对京西北地区（39.5°—41.5° N,113°—117° E）2013年1月1日至2017年12月31日6 223次有效地震进行精确定位,得到该区震源分布的精细图像和震源深度剖面图。结果显示,重新定位后地震的水平分布更集中,沿断裂带分布特征更加明显,震中在断裂带呈更明显的条带状、簇状分布,地震与线状的深浅断裂构造的关系密切;大部分地震发生在中上地壳,震源分布为典型震源密集区的空间形态,呈纵深约15 km、直径20—40 km的近圆形“厚饼状”。