福建及其邻区背景噪声面波群速度层析成像

基于福建及邻区108个宽频带地震台站2016年6月到7月两个月垂直和水平分量波形连续记录, 利用相位加权叠加算法提高信噪比, 计算得到108个台站对的高质量经验格林函数。 对所获取的经验格林函数, 采用时频分析的方法在1~20 s频段内量取了大量高质量的Rayleigh波和Love波群速度频散数据。 在此基础上, 采用基于射线追踪的二维层析成像方法反演得到了福建及其邻区1~20 s的Rayleigh波和Love波群速度分布。 分辨率测试结果表明群速度分布的分辨率能达50 km。 成像结果显示1~10 s的群速度分布与地壳中上部地质特征有很好的一致性, 区内的福州盆地和漳州盆地在浅层结构中表现出明显的低速异常。 长周期的群速度则揭示了漳州西北的高地热区内中下地壳低速体, 政和-大埔断裂两侧的速度差异, 表明其可能是一个深大断裂, 并呈现明显的东西差异。     

砌体和钢混结构建筑群的破坏概率模型研究

通过对已有震害预测的易损性矩阵进行研究,对目前易损性矩阵的概率模型进行了修改。分析了华南地区建筑群的3种主要结构类型:钢混结构,砖混结构和砖木结构。将3种结构在各种烈度下的破坏状态分别进行了拟合和参数计算,针对其差异性提出了偏态分布和正态分布,给出了不同的破坏概率模型。在广东省惠州市数据的验算下,证明了对于砌体和钢混建筑群易损性矩阵的呈现有一定的参考意义。     

液化场地桥梁群桩-土耦合体系强震反应分析

针对振动台试验,采用u-p形式控制方程表述饱和砂土的动力属性,选用土的多屈服面塑性本构模型刻画饱和砂土和黏土的力学特性,引入非线性梁-柱单元模拟桩,建立试验受控条件下液化场地群桩-土强震相互作用分析的三维有限元模型,并通过试验结果验证数值建模途径与模拟方法的正确性。以实际工程中常用的2×2群桩为例,建立桩-土-桥梁结构强震反应分析三维有限元模型。基于此,针对不同群桩基础配置对液化场地群桩-土强震相互作用影响展开具体分析。对比发现,桩的数量相同时,桩排列方向与地震波输入方向平行时比垂直时桩基受力减小5%~10%,而对场地液化情况无明显影响;相同排列形式下,三桩模型中土体出现液化的时间约比双桩模型延缓5s,桩上弯矩和剪力减小33%~38%。由此可见,桩基数量增加,桩-土体系整体刚度更大,场地抗液化性能显著,桩基对上部桥梁结构的承载性能明显增强,其安全性与可靠性更高。这对实际桥梁工程抗震设计具有一定的借鉴意义。     

导航星座抗毁组网结构研究

为提高整个二代导航卫星网络的抗毁性能,对其抗毁组网结构进行了研究。基于分群管理、链路冗余与修补方法,提出并设计分析了一种基于GEO星层、MEO星层以及地面节点联合组网的二代导航卫星网络组网结构,根据快照周期内位置固定的方法对星座中MEO星层进行分群管理,设计其群首的备份选择机制,以及群首MEO替代失效群管理者GEO机制,提高了星座网络的通信链路的抗毁性。通过分析二代导航卫星网络中数据传输过程与类型,设计网络结构中群内、星层以及整个二代导航星座的通信链路,特别是对星座中MEO星层的通信链路进行充分的冗余设计,启用视距范围内间隔失效卫星间次相邻卫星节点链路连接的链路设计,并同时提高了整个二代导航卫星网络的通信性能和通信容量,可以满足各种不同业务需求的数据包传输。     

导航星座抗毁路由方法与技术研究

基于分群管理、群首备份、链路冗余、链路修补的二代导航卫星网络组网结构,提出并设计了一种基于GEO星层、MEO星层、地面节点联合组网的抗毁路由算法（DRRA）。基于二代导航动态卫星网络中卫星移动的动态卫星网络中,提出的DRRA算法在定位信号稳定、数据包路由抗毁、数据包路由最短延时等方面具有优势,并分析了其主要原因。     

Response of a scale-model pile group for a jacket foundation of an offshore wind turbine in liquefiable ground during shaking table tests

To investigate the seismic response of a pile group during liquefaction, shaking table tests on a 1/25 scale model of a 2 × 2 pile group were conducted, which were pilot tests of a test project of a scale-model offshore wind turbine with jacket foundation. A large laminar shear box was utilized as the soil container to prepare a liquefiable sandy ground specimen. The pile group model comprising four slender aluminum piles with their pile heads connected by a rigid frame was designed with similitude considerations focusing on soil–pile interaction. The input motions were 2-Hz sinusoids with various acceleration amplitudes. The excess pore water pressure generation indicated that the upper half of the ground specimen reached initial liquefaction under the 50-gal-amplitude excitation, whereas in the 75-gal-amplitude test, almost entire ground was liquefied. Accelerations in soil, on the movable frames composing the laminar boundary of the shear box, and along the pile showed limited difference at the same elevation before liquefaction. After liquefaction, the soil and the movable-frame accelerations that represented the ground response considerably reduced, whereas both the movable frames and the piles exhibited high-frequency jitters other than 2-Hz sinusoid, and meantime, remarkable phase difference between the responses of the pile group and the ground was observed, all probably due to the substantial degradation of liquefied soil. Axial strains along the pile implied its double-curvature bending behavior, and the accordingly calculated moment declined significantly after liquefaction. These observations demonstrated the interaction between soil and piles during liquefaction.     

山东省昌乐县新生代火山口新发现及旅游地质意义

昌乐蓝宝石闻名遐尔，但蕴藏蓝宝石的火山岩及火山群却少有人知。昌乐县境内几十个由新近纪临胸群牛山组尧山组玄武岩构成的山包，大都是古火山口(颈)。近期，在北岩镇南开出的古火山口(颈)，其玄武岩柱状节理的扇状展布和罕见的两次熔岩喷发交切遗迹，比以往已开发的乔官镇团山子古火山口更为奇特和壮观。火山地貌景观区历来是人们向往的旅游胜地，对昌乐古火山群旅游资源，应加大开发和保护力度，使其尽快成为人们观赏地质奇观、增长科学知识的基地。发展地质旅游将促进当地经济的腾飞。     

三峡工程运用后坝下游河道泥沙输移变化规律

三峡工程蓄水后"清水"下泄,坝下游河段将会长期处于严重不饱和状态,水流含沙量沿程恢复将会引起坝下游长距离冲刷,本文根据三峡工程蓄水前、后的实测资料分析了坝下游河道泥沙输移变化规律,探索不同粒径组沙量沿程恢复对河床冲刷的影响,得到以下结论:在蓄水初期d≤0.031 mm沙量恢复主要受河床补给与江湖入汇共同的影响,随着水库下泄该粒径组沙量递减,使得各站该粒径组年均输沙量均远小于蓄水前的水平,沙量恢复仍主要受河床补给与江湖入汇的影响,这是造成坝下游河道发生长距离冲刷的主要原因之一;在蓄水初期0.031 mmd≤0.125 mm沙量恢复主要受河床补给的影响,但江湖入汇的影响较大,随着河床补给量逐渐减少,各站该粒径组年均输沙量均小于蓄水前的水平,沙量恢复仍主要受河床补给的影响,江湖入汇的影响逐渐减小,这也是坝下游河道发生长距离冲刷的主要原因之一; d0.125 mm沙量恢复主要受河床补给的影响,蓄水初期该粒径组沙量在宜昌监利河段沿程恢复速率较快,且在监利站达到蓄水前的水平,随着时间推移,在宜昌监利河段沿程恢复且速率仍较快,在监利站达到最大值,其数值逐渐小于蓄水前的水平,这是造成坝下游河道冲刷重点集中在宜昌监利河段的主要原因.     

VELOCITY CHARACTRISTICS OF SHANXI AND ADJACENT AREA AND ITS TECTONIC SIGNIFICANCE

In order to acquire a better velocity structure of the crustal and uppermost mantle beneath Shanxi area, we obtain the group and phase velocities of Rayleigh wave of the periods 8s to 50s in Shanxi and adjacent area using ambient seismic noise recorded at 216 broad-band stations. All available vertical-component time series for 2014 have been cross-correlated to yield estimates of empirical Rayleigh wave Green's function. Group and phase velocity dispersion curves for Rayleigh wave are measured for each interstation path by applying frequency-time analysis. It describes finer velocity structure of the crust and upper mantle in Shanxi, which reflects the geological structure characteristics at different depths. The resolution is within 50km and the resolution of part periods can reach 40km.The Rayleigh wave group and phase speed maps at short periods(8~18s and 10~22s)show clear correlations with shallow geological structures. Mountain areas on both sides of Shanxi depression zone show apparent high-velocity anomaly, except for low-velocity anomaly in the Taiyuan Basin, Linfen-Yuncheng Basin and Weihe Basin. Especially, the areas of Youyu County-Pianguan County-Kelan County-Shuozhou City and Jingle County-Lishi District of Lüliang City in Lüliang Mountains, and Yu County-Fuping County-Yi County and Yangcheng County-Licheng County in Taihang Mountains, present higher velocity anomaly. In addition, the velocity is lowest in the Weihe Basin, and the amplitude of low velocity decreases gradually from the south to the north of the basins in Shanxi, which probably is related to the process of gradual stretching and development of the Shanxi rift zone from the southwest to the northeast. The obvious velocity difference across the latitude of 38°N exists at 18~30s period of phase and 24~35s period of group velocity maps, which is probably related to the deep and shallow Moho depth variation in the south and north of Shanxi and the suture zone of ancient blocks including "hard" southern block and "soft" northern block. At the same time, the research result of receiver function reveals that partial melting of the lower crust occurs in the northern Taihang Mountains, while the southern section remains stable(Poisson's ratio is above 0.3 in the northern Taihang Mountains and 0.25~0.26 in the southern section). The phase velocity map at 30~50s period clearly shows NW velocity gradient belt, and the low velocity anomaly in the northeast side may be related to Cenozoic volcanism. Meanwhile, the eastern border of Ordos block is the western faults of central basins in Shanxi depression zone. However, some research results indicate that the above border is Lishi Fault in the surface, inferring that the Ordos block shows a shape of wide in the upper and narrow in the lower part from the surface to deep. The Datong volcanic area at 18~45s period of phase and 24~35s period of group velocity maps shows low velocity of trumpet shape from shallow to deep, related to the upwelling of hot material from lower mantle in the Cenozoic causing a large area of intense magmatic activity. It indicates the more specific upwelling channel of Datong volcanoes simultaneously.     

武汉交通学校群楼爆破拆除塌落振动分析

为了分析一次性爆破拆除多栋建筑造成的地面振动的特征及对周边建筑物的影响,对武汉交通学校群楼爆破拆除中的地面振动进行了测量,并对实测的塌落振动的峰值、频谱特性进行分析。结果表明:此次监测记录到的峰值频率在5～10 Hz,对比高架桥以及单一高层结构爆破拆除数据,倒塌叠加使得振动能量在频谱上分布更加离散,其峰值频率与周边结构自振频率相差变大,周边建筑共振的危险性降低;对于周围的结构而言,水平振动持时大于竖向振动,但水平振动幅值明显小于竖向振动;爆破塌落振动的竖向分量对周围结构的威胁较大,应采取有效的缓冲及隔振措施;由《爆破安全规程》和周边建筑爆破前后主振频率分析可知,本次爆破拆除工作未对周边建筑造成破坏性影响,验证了群楼爆破拆除方案的高效性和安全性。