Numerical analysis of deformation behaviour of quay walls under earthquake loading

In the last 50 years, there have been many incidences of failure of gravity quay walls. These failures are often associated with significant deformation of liquefiable soil deposits. Gravity quay wall failures have stimulated great progress in the development of deformation-based design methods for geotechnical structures. In this paper, the effective-stress analysis method has been used in conjunction with a generalised elasto-plasticity constitutive model implemented into a finite element procedure. Various monotonic and cyclic triaxial paths are simulated in order to demonstrate the capabilities of the constitutive model. The FEM is validated by back analysis of a typical Port Island PC1 caisson type quay wall, which was damaged during the 1995 Hyogoken-Nanbu earthquake. The numerical results are compared with the observed data obtained consisting of seaward displacement, settlement and tilting. In addition, both the influence of permeability, on the generation of pore water pressure and the influence of the relative density of the backfill and foundation layers, on the residual deformation of gravity quay walls are investigated.     

Reactive transport in stratified flow fields with idealized heterogeneity

A two-dimensional equation governing the steady state spatial concentration distribution of a reactive constituent within a heterogeneous advective–dispersive flow field is solved analytically. The solution which is developed for the case of a single point source can be generalized to represent analogous situations with any number of separate point sources. A limiting case of special interest has a line source of constant concentration spanning the domain’s upstream boundary. The work has relevance for improving understanding of reactive transport within various kinds of advection-dominated natural or engineered environments including rivers and streams, and bioreactors such as treatment wetlands. Simulations are used to examine quantitatively the impact that transverse dispersion (deviations from purely stochastic-convective flow) can have on mean concentration decline in the direction of flow. Results support the contention that transverse mixing serves to enhance the overall rate of reaction in such systems.     

Geostatistical evaluation of magnetic indicators of forest soil contamination with heavy metals

The goal of the study was the geostatistical evaluation of quantitative magnetic measures, which can be used for effective delineation of the extent of the area polluted with heavy metals. Several parameters of magnetic susceptibility, measured in the soil profile, were proposed as magnetic indicators of soil pollution and analyzed in detail. The following parameters were calculated: maximum magnetic susceptibility, magnetic susceptibility at the depth of 3 cm and 5 cm, and the area under the curve of magnetic susceptibility. Measurements were performed at two forested study areas, located in Upper Silesian Industrial Area (Poland). Analyses were performed using geostatistical methods, and the results were verified using dense chemical measurements. The results showed that the area under curve of magnetic susceptibility was the most effective magnetic indicator of soil contamination with heavy metals. It was possible to detect the entire polluted area, and only about 16% of the study area was assumed to be contaminated while being unpolluted. The results obtained with maximum magnetic susceptibility and magnetic susceptibility at the depth of 3 cm and 5 cm were less effective in comparison with the area under curve of magnetic susceptibility.     

Three-layer model for vertical velocity distribution in open channel flow with submerged rigid vegetation

Based on the detailed laboratory experiments and theoretical analysis, a new three-layer model is proposed to predict the vertical velocity distribution in an open channel flow with submerged vegetation. The time averaged velocity and turbulence behaviour of a steady uniform flow with fully submerged artificial rigid vegetation was measured using a 3D Micro ADV, and the vertical distribution of velocity and Reynolds shear stress at different vegetation height, vegetation density and measuring positions were obtained. The results show that the velocity profile consists of three hydrodynamic regimes (i.e. the upper non-vegetated layer, the outer and bottom layer within vegetation); accordingly different methods had been adopted to describe the vertical velocity distribution. For the upper non-vegetated layer, a modified mixing length theory combined with the concept of ‘the new vegetation boundary layer’ was adopted, and an analytical model was presented to predict the vertical velocity distribution in this region. For the bottom layer within vegetation, the depth average velocity was obtained by numerically solving the momentum equations. For the upper layer within vegetation, the analytical solution was presented by expressing the shear stress as a formula fitted to the experimental data. Finally, the analytical predictions of the vertical velocity over the whole flow depth were compared with the results obtained by other researchers, and the good agreement proved that the three-layer model can be used to predict the velocity distribution of the open channel flow with submerged rigid vegetation.     

泰安重力观测高频波动信号分析

系统分析了泰安重力观测资料正常和异常时信号的周期特征,研究了高频异常信号与台风、气压和强震之间的关系.结果表明:泰安重力观测正常时信号周期为2～4分钟,异常时信号周期只有2～3分钟,异常信号幅值约为正常信号的5倍;高频异常信号主要是由西太平洋洋面上生成的进入中国大陆或近海的台风引起的,占台风引起泰安重力出现高频异常信号的90%;重力高频信号与台风中心速度正相关,与台风距离负相关,并且随台风的结束高频信号也随之消失;少数高频异常信号与强震也有一定关系,占地震总数的17.24%;高频异常信号与气压变化无关.     

福建东南沿海重力场演变特征及其与地震的关系

分析研究了福建地区2001～2008年的流动重力测量资料,探讨了福建东南沿海地区重力场变化与永春ML4．6和长泰ML=4．7级地震的关系。结果表明：这2次地震前,靠近震中测点的重力值有明显的变化。     

共偏移距道集平面波叠前时间偏移与反偏移

在Dubrulle提出的共偏移距道集频率波数域叠前时间偏移的基础上,提出了共偏移距道集频率波数域叠前时间偏移与反偏移一对共轭算子.讨论了该对算子的变孔径实现过程.并把该对共轭算子串连起来实现了叠前地震数据的规则化处理.指出最小二乘意义下的叠前地震数据规则化会得到更好的效果.v(z)介质模型和Marmousi模型的数值试验结果表明,方法理论正确、有效.     

实数编码多种群遗传算法的改进及应用

本文首先从分析实数编码的GA理论出发,提出实数编码条件下不需要继续沿用二进制编码条件下常用的传统单点、两点及多点交叉算子,基因选择可采用基因位独立（locus independent）的方式进行.据此研制了相应的交叉算子,并给出了一种实现方式,试验计算验证了该算子的有效性.其次,针对地球物理反演问题的复杂性以及遗传算法参数设置对问题的敏感性,将算法性能调整的灵活性作为方法选择的重要标准,采用了多种群遗传算法作为反演方法,设计了两个种群级的改进策略,并验证了其效能.最后,将改进的实数编码多种群遗传算法应用于重力模型反演,完成了梯形变密度体组合模型和2.5度体多边形棱柱组合模型的反演试算,取得了预期效果,并成功地应用于新疆地区实际资料的处理与解释.     

重力场动态变化与汶川MS8.0地震孕育过程

基于中国大陆1998～2007年（复测周期2～3年）流动重力观测数据,结合GPS、水准观测成果和区域地质构造动力环境,分析研究了汶川8.0级地震区域重力场动态变化演化特征和孕震机理.结果表明：区域重力场动态演化大体反映了青藏高原物质东流的动态效应和汶川大震孕育的中长期（2～10年）信息;汶川大震孕育的显著重力标志为震中西南持续多年的正重力变化（上升）和出现较大规模的重力变化梯级带,前者有利于地震能量的不断积累,后者有利于地震剪切破裂的发生;与地震孕育相关重力场变化总体呈增大—加速增大—减速增大—发震的过程;8年累积重力变化幅差最大约200×10^-8m·s^-2;2001年昆仑山口8.1级地震孕育发生和震后恢复调整,对区域重力场动态变化和汶川大震的孕育发展具有重要影响;松潘—甘孜块体一般呈现负重力变化,可能反映深部壳幔局部上隆、壳内温度较高而膨胀,有利于逆冲或推覆体运动的形成和大震的发生.     

太行山东缘石家庄南部地壳结构及断裂活动性探测

采用深、浅地震反射和钻孔地质剖面相结合的方法,对太行山东缘石家庄南部的地壳结构和隐伏断裂的活动性进行了研究.深地震反射探测结果表明,该区地壳厚度33~38km,莫霍面从华北平原向太行山下倾伏.石家庄—晋县凹陷是受拆离断层控制的盆岭构造,太行山山前断裂为凹陷的西边界断裂,表现为上陡下缓的铲形断裂.石家庄—晋县凹陷中还发育北席断裂和栾城断裂,它们与太行山山前断裂一样受拆离断层的控制,未错断早更新世晚期以来沉积的地层不属于活动断裂.深地震反射剖面的中部还揭示了一个近垂直的穹窿状反射异常体,它可能起源于莫霍面,向上,穿过上、下地壳分界面,并延伸至上地壳.穹窿状反射异常体内部反射波视频率随深度增加而降低,在莫霍面附近的壳幔过渡带也出现明显的频率降低、界面扭曲和变形现象,推断它可能是上地幔岩浆上涌到地壳内部的侵入体.结合电磁测深结果可以发现,上地幔热物质的上涌和东、西向拉张可能是形成石家庄—晋县凹陷的动力学机制.探测结果为深入理解石家庄地区的深部地球动力学过程、华北克拉通破坏机制、深浅构造关系和地震构造提供了依据.