InSAR复影像配准方法与实践

利用合成孔径雷达干涉测量技术获取地表三维信息的研究，受到世界各国的广泛关注。高精度复影像配准是InSAR数据处理的关键步骤，其结果直接影响生成干涉相位的质量，进而影响获取数字高程模型的精度。本文采用相干系数法进行粗配准，采用基于相干系数拟合的方法进行精配准，可以实现复影像数据的高精度配准。经机载和星载数据的试验验证，该方法有效可行且运算效率高，具有实用性。     

Suitability analysis for topographic factors in loess landslide research: a case study of Gangu County,China

Loess Plateau is one of the ecologically fragile regions in China. It is one of the slippery strata of which landslides often developed. The formation and development of landslides are mainly affected by various natural environments, triggering factors, the vulnerability of landslide-bearing bodies, and topography has a controlling effect on landslides and determines landslide distribution. As important environmental elements, the selection and reclassification of topographic factors are the basis for loess landslide vulnerability map. In this study, our research suggests an effective workflow to select and analyze the topographic factors in the loess landslides. Nine hazard-formative environmental factors [e.g., slope, aspect, slope shape (SS), slope of slope (SOS), slope of aspect (SOA), surface amplitude (SA), surface roughness (SR), incision depth (ID) and elevation variation coefficient (EVC)] are prepared for landslide suitability analysis. The models of certainty factor, sensitivity index and correlation coefficient are combined to select and analyze the suitability of these factors. Four topographic factors (i.e., slope, SOS, SS and SR) were ultimately selected to carry out the landslide vulnerability mapping with other factors. Our results showed that most of the landslides were located in medium and high classes and accounting for 75.3%, and these places also coincided with higher economies and intense human activities. Our research also suggested that in situ measurements are necessary to determine how to reclassify these topographic factors and how many grades these topographic factors divided, which would further improve the reliability of landslide vulnerability map for the decision makers to deal with the possible future landslides in terms of safety and human activities.     

Study on acoustic emission characteristics of sandstone under different fracture modes

To investigate the characteristics of the sandstones under two fracture modes which are tensile fracture and shear fracture, we proposed three-point bending test and a modified shear test. Meanwhile, numerical simulations using particle flow code (PFC) and acoustic emission (AE) analysis are performed to obtain their differences. The AE hits and amplitude analyses prove that no matter which mode, they experience obvious three stages. The AE hit curve and amplitude are lower in the first stage. Then, the curve goes up steadily and the amplitude value becomes relatively large in the second stage. Entering into the third stage, the curve increases quickly to its peak value and a lot of AE signals with higher amplitude are generated. Moreover, AE b-value analysis is also used to make crack magnitude assessment. It was obvious that the distribution of b-value curve can be divided into three stages, which are just corresponding to the division of AE hits and amplitude distributions. The b-values are diverse and fluctuating largely in stage I and then show small fluctuations and have increasing trends in the whole process in stage II whereas finally exhibit sharp down to the minimum points at the stage III. The average b-values for tensile fracture tests are in the range of 0.877–1.09 whereas for shear fracture tests are within the range of 0.815–0.876. Comparing to tensile fracture, when shear fracture occurs in the rock sample, the AE energy releases faster and the proportion of large magnitude cracks is larger. The research results in this article could make more instructive and applied value to in situ non-destructive monitoring of fissure development for engineering rock mass.     

Machine learning-based thermokarst landslide susceptibility modeling across the permafrost region on the Qinghai-Tibet Plateau

Landslides - Thermokarst landslides (TL) caused by the thaw of ground ice in permafrost slopes are increasing on the Qinghai-Tibet Plateau (QTP), but the understanding of the spatially suitable...     

三沙湾亚硝酸氮、氨氮、磷酸盐的异常、机制及影响

闽东三沙湾是最典型的多河流汇入的封闭型海湾,是世界上最大的大黄鱼网箱养殖基地和全国最主要的渔业养殖基地之一,多次调查却发现该湾藻类生产量远低于其他海湾,呈现"营养多藻类少"独特的生态特征,但都没有深入讨论其机制.本研究2018-2020年采用定点和大面走航方式,调查了5项营养盐(活性硅酸盐(SiO₃-Si)、硝酸氮(NO₃-N)、亚硝酸氮(NO₂-N)、氨氮(NH₄-N)、活性磷酸盐(PO₄-P))的潮汐运动及空间分布,结果发现:(1)流域输入导致SiO₃-Si、NO₃-N落憩浓度大于涨憩浓度,并从岸向湾内随盐度增加而线性减少.(2)湾内养殖和自然生态系统输出导致NO₂-N、NH₄-N、PO₄-P涨憩浓度大于落憩浓度,洪季浓度大于枯季浓度,从岸向湾NO₂-N随盐度增加而非线性增加,NH₄-N、PO₄-P随盐度增加而平均分布等异常现象,但沿岸排污口附近NH₄-N、PO₄-P呈落憩浓度大于涨憩浓度.(3)湾内养殖和沿岸排污输入的高浓度NH₄-N、PO₄-P,是三沙湾水质严重污染和富营养化的主要原因,湾内养殖引起的高浓度NO₂-N是引起三沙湾"营养多藻类少灾害多"这一独特的生态特征的主要因素.      

Genesis of the titanian andradite in alkaline rocks and their petrological and mineralization significance:A study example of the garnet from the Fanshan ultramafic. syenitic complex in North China CratonSCIEI北大核心CSCD

富钛钙铁榴石是硅不饱和碱性火成岩中的特征矿物,其Ti含量和Ti进入石榴石的方式可直接反映岩浆体系的硅饱和度和氧逸度。河北矾山超镁铁岩-正长岩杂岩体是华北克拉通北缘东西向展布三叠纪碱性岩带的重要岩体之一,其岩石中发育三种类型的富钛钙铁榴石:类型Ⅰ发育于岩体外带的石榴石辉石正长岩中,与辉石、黑云母呈岩浆共生关系,端元组成为Adr_(25-65)Mmt_(15-37)Slo_(8-28)Grs_(10-14),以高TiO_(2)含量(6.08%~18.61%)、较低的SiO_(2)含量(25.46%~33.26%)为特征,为原生岩浆成因;类型Ⅱ见于各类岩石,呈细粒他形充填于其他矿物颗粒之间,端元组成为Adr_(57-69)Mmt_(5-19)Slo_(0-6)Grs_(19-27),以高Al_(2)O_(3)含量(3.95%~5.56%)为特征,为岩浆演化后期熔体富Al_(2)O_(3)时结晶而成;类型Ⅲ亦见于各类岩石,主要呈细粒他形或细碎状发育于其他矿物内,端元组成为Adr_(68-79)Mmt_(8-14)Slo_(0-5)Grs_(6-14),以低的Al_(2)O_(3)含量(1.18%~2.89%)和较高的FeO含量(21.65%~24.62%)为特征,为岩浆期后热液成因。在矾山杂岩体的富钛钙铁榴石中,Ti主要以Si→Ti^(4+)和2Fe^(3+)→Ti^(4+)+Fe^(2+)/Mg替代方式进入到晶体结构中,反映了矾山杂岩体的母岩浆体系为二氧化硅不饱和的碱性岩浆,并具有较高的氧逸度。受石榴石的主量元素组成和相应的晶体结构控制,在微量元素组成上,矾山杂岩体中的富钛钙铁榴石富集轻稀土或中稀土、亏损重稀土,大离子亲石元素(Rb、Ba、Pb和Sr)含量较低或极低,而高场强元素(如Th、U、Nb、Ta、Zr和Hf等)含量普遍较高。本文对石榴石的成因研究结果支持矾山杂岩体不同类型的岩石形成于封闭体系下同一母岩浆系统充分的结晶-分异和堆晶作用;此演化模式可以较好地解释矾山杂岩体的同心环状特征和韵律层状结构,以及磁铁矿和磷矿的成因。     

Late Permian to Early Triassic subduction and retreating of the Paleopacific slab: Constraints from continental arc magmatism in Hainan IslandSCIEI北大核心CSCD

海南岛大规模二叠-三叠纪侵入岩的形成是与古特提斯洋有关,还是与古太平洋俯冲闭合有关还存在巨大争议。本文对琼中金波两处辉绿岩脉及其围岩花岗岩的研究显示,露头1辉绿岩脉的锆石U-Pb年龄为245.4±3.8Ma,TiO_(2)含量(1.07%~1.18%)低,而MgO(8.60%~9.41%)和Mg^(#)值(62.31~65.02)较高,为钙碱性系列,球粒陨石和原始地幔标准化配分曲线中具有明显的Eu、Nb、Ta、Ti和Ba负异常,以及显著Th、U、Zr、Rb和Pb等正异常,(^(87)Sr/^(86)Sr)_(i)=0.707138~0.712797,(^(143) Nd/^(144)Nd)_(i)=0.511884~0.511965,ε_(Nd)(t)值为-7.01~-8.58,指示其形成于大陆岛弧环境。相比之下,露头2辉绿岩锆石U-Pb年龄为242.8±3.1Ma,但其TiO_(2)(2.65%~3.06%)含量较高,而MgO(4.24%~5.39%)和Mg^(#)值(40.09~45.86)较低,具有Eu、Rb、Pb、Nb、Ta和Ti弱正异常和Th负异常,(^(87)Sr/^(86)Sr)_(i)=0.690244~0.717031,(^(143) Nd/^(144)Nd)_(i)=0.512886~0.512915,ε_(Nd)(t)值为+6.41~+7.93,具有板内玄武岩的特征,指示其形成于板内裂解环境。辉绿岩脉围岩二长花岗岩的锆石U-Pb年龄为255.3±3.0Ma和255.7±3.2Ma,含少量角闪石和黑云母,具有较高的SiO_(2)(71.62%~73.72%)、Na_(2)O+K_(2)O(6.60%~9.17%)和Al_(2)O_(3)(平均14.88%)含量,A/CNK值(0.97~1.03)较低,亏损Nb、Ta、Ti、Sr和Ba,富集Rb、Th、U和Pb,为高分异I型岛弧花岗岩。总的来看,二长花岗岩和辉绿岩形成于大陆岛弧挤压向伸展过渡的构造环境。对比二叠-三叠纪侵入岩体的走向、碰撞前-同碰撞-碰撞后岩浆岩的时代以及榴辉岩的变质年龄等,发现海南岛侵入岩与哀牢山-松马造山带明显不同,而与日本和朝鲜半岛的岛弧岩浆岩类似,由此我们认为海南岛大规模晚二叠-早三叠世岩浆岩为古太平洋板片向欧亚板块俯冲后撤的产物,后撤过程受到古特提斯俯冲板片的影响。     

Optimization of Supporting Structures and Parameters of Tunnels in Soft Phyllite

The study investigated the extra-long Shuangxiling tunnel in soft phyllite within Nanchang–Ningdu highway in Jiangxi province, China. The supporting scheme of reducing the size and density of anchor rods while strengthening the stiffness and strength of preliminary support was put forward aiming at the repeated occurrence of great deformation of surrounding rocks during tunneling. Moreover, two groups of comparative supporting schemes were introduced for comparison. Based on the numerical simulation, the study calculated the amount of displacement deformation, stress on anchor rods, development of plastic zones, stress on shotcrete, and stress on secondary lining structure under different supporting schemes. By conducting field monitoring test, the surrounding rock deformations and pressures under different supporting schemes were monitored and measured in real time. The research results showed that after strengthening the stiffness and strength of preliminary support, the surrounding rock pressure on the supporting structure increased. It limited the preliminary stress release rate of surrounding rocks, protected the integrity of surrounding rocks and controlled the sustained deformation of surrounding rocks. However, weakening the size and density of anchor rods had an insignificant effect on the whole supporting effect. The result of field test was basically consistent with that obtained through numerical simulation, which theoretically and practically verified the scientificity and feasibility of the supporting scheme of weakening the size and density of anchor rod while strengthening the stiffness and strength of preliminary support. The research result provides references for the support optimization of similar tunnels along the highway.