Nonlinear Analysis of Local Site Effects on Seismic Ground Response in the Bam Earthquake

The influence of local geologic and soil conditions on the intensity of ground shaking is addressed in this study. The amplification of the ground motion due to local site effects resulted in severe damage to dwellings in the Bam area during the 2003 Bam Earthquake. A unique set of strong motion acceleration recordings was obtained at the Bam accelerograph station. Although the highest peak ground acceleration recorded was the vertical component (nearly 1 g), the longitudinal component (fault-parallel motion) clearly had the largest maximum velocity as well as maximum ground displacement. Subsurface geotechnical and geophysical (down-hole) data in two different sites have been obtained and used to estimate the local site condition on earthquake ground motion in the area. The ground response analyses have been conducted considering the nonlinear behavior of the soil deposits using both equivalent linear and nonlinear approaches. The fully nonlinear method embodied in FLAC was used to evaluate the nonlinear soil properties on earthquake wave propagation through the soil layer, and compare with the response from the equivalent linear approach. It is shown that thick alluvium deposits amplified the ground motion and resulted in significant damage in residential buildings in the earthquake stricken region. The comparison of results indicated similar response spectra of the motions for both equivalent and nonlinear analyses, showing peaks in the period range of 0.3–1.5 s. However, the amplification levels of nonlinear analysis were less than the equivalent linear method especially in long periods. The observed response spectra are shown to be above the NEHRP building code design requirements, especially at high frequencies.     

Interference of Multiple Strip Footings on Sand Using Small Scale Model Tests

By using small scale model tests, the interference effect on the vertical load-deformation behavior of a number of equally spaced strip footings, placed on the surface of dry sand, was investigated. At any stage, all the footings were assumed to (i) carry exactly equal magnitude of load, and (ii) settle to the same extent. No tilt of the footing was permitted. The effect of clear spacing (s) among footings on the results was explored. A new experimental setup was proposed in which only one footing needs to be employed rather than a number of footings. The bearing capacity increases continuously with decrease in spacing among the footings. The interference effect becomes further prominent with increase in soil friction angle. In contrast to an increase in the bearing capacity, with decrease in spacing of footings, an increase in the footing settlement associated with the ultimate state of shear failure was observed. The present experimental observations were similar to those predicted by the available theory, based on the method of characteristics. As compared to the theory, the present experimental data, however, indicates much greater effect of interference especially for larger spacing among footings.     

采用碳氮稳定同位素技术对黄海中南部鳗鱼食性的研究

根据2005年4～5月在黄海和长江口海域进行的春季底拖网调查，应用稳定同位素方法研究了黄海中南部鯷鱼（Engraulis　japonicus）及其可能摄食饵料的碳氮稳定同位素比值，结果表明：（1）黄海中南部鯷鱼的食物组成为不同粒径的浮游动物、太平洋磷虾（Euphausia pacifuca）和仔稚鱼，其中以粒径为500-900μm的浮游动物为主，贡献比例占61％～84％；仔稚鱼贡献比例占16％～21％，较传统胃含物方法分析的结果小；（2）黄海中部海域鯷鱼的碳氮稳定同位素比值平均值较南部海域高，原因可能与各海域的能量来源不同或存在微食物环有关，也可能与不同海域鯷鱼的能量转换途径不一样，即与食物链长短不一有关．     

Diel Patterns in Chlorophyll <Emphasis Type="Italic">a</Emphasis> Specific Absorption Coefficient and Absorption Efficiency Factor of Picoplankton

Diel patterns in the chlorophyll a specific absorption coefficient of surface picoplankton, a*_pico (γ) (m²·[mg chlorophyll a]⁻¹), were studied at 7 stations under daily cycle of in situ light condition in the western subarctic Pacific and Japan Sea. All the data were normalized by dividing the anomaly with daily averaged a*_pico (γ). Opposite diel patterns were observed for the normalized a*_pico (443) and a*_pico (675) with maximum toward dawn or dusk and minimum toward midday at 4 stations under low-irradiance (LI) conditions and vice versa at 3 stations under high-irradiance (HI) conditions. The absorption efficiency factors at red absorption peak, Q _a (675), were determined by reconstruction with intracellular chlorophyll a concentration and cell diameter. The normalized Q _a (675) also showed diel pattern with maximum toward midday and minimum toward dawn or dusk under LI. The diel pattern in a*_pico (675) and Q _a (675) were primarily caused by changes in intracellular chlorophyll a concentration due to photoadaptation under LI. The diel pattern in a*_pico (443) was influenced by pigmentation, as recognized by blue to red ratio [a*_pico (443)/a*_pico (675)] under HI. This study proposed that the opposite diel pattern in a*_pico (γ) might occur for a wide range of algal species. The results presented here have important consequences for the interpretation of diel variations in optical properties observed in the open ocean.     

Effect of Cyclic Loading Frequency on Undrained Behaviors of Undisturbed Marine Clay

Based on a series of cyclic triaxial tests, the effect of cyclic frequency on the undrained behaviors of undisturbed marine clay is investigated. For a given dynamic stress ratio, the accumulated pore water pressure and dynamic strain increase with the number of cycles. There exists a threshold value for beth the accumulated pore water pressure and dynamic strain, below which the effect of cyclic frequency is very small, but above which the accumulated pore water pressure and dynamic strain increase intensely with the decrease of cyclic frequency for a given number of cycles. The dynamic strength increases with the increase of cyclic frequency, whereas the effect of cyclic frequency on it gradually diminishes to zero when the number of cycles is large enough, and the dynamic strengths at different frequencies tend to the same limiting minimum dynamic strength. The test results demonstrate that the reasons for the frequency effect on the undrained soil behaviors are beth the creep effect induced by the loading rate and the decrease of sample effective confining pressure caused by the accumulated pore water pressure.     

标志沉积层磁组构特征及其古环境意义研究

通过对长江三角洲及其邻近区域埋藏古土壤、潮坪、长江下游河道浸滩、舟山滨岸风成沙丘、南京黄土古土壤序列沉积体的磁组构测量统计分析，取得了各自的标志特征。该２特征揭示出，舟山滨岸风成沙丘与南京黄土吉土壤序列沉积的搬运介质能量位相基本一致，其物源来向却显示出巨大差异；上述两类沉积体与上述现今潮坪、河道漫滩沉积体地搬运介质能量位相及物源来向均显示出绝然不同的标志特征。然而浸滩物源来民南京黄土的物尖兵为向却     

台湾海峡中北部上升流区各种形态磷的化学特性

根据１９８８年７月调查资料讨论了台湾海峡中北部海域夏季上升流区各种形态磷的分布特征。结果表明，上升流中心区（即海坛岛东侧一带水域）具有低温、高盐、低溶解氧；ＤＩｐ，ＴＤＰ，ＰＰ，ＴＰ较高；ＤＯＰ较低（０．２７）；及ＤＩＰ／ＤＯＰ比值（约为１）较高的特性。ＤＯＰ是该海域磷的主要形态（占ＴＰ的４９．２％），其含量分布及其形态转化与生物活动直接相关，是该海域生物生产力高的体现。     

黑鲷和青石斑鱼对气泡幕反应的比较

在室内水池中观察了黑鲷（Ｓｐａｒｕｓｍａｃｒｏｃｅｐｈａｌｕｓ）和青石斑鱼（Ｅｐｉｎｅｐｈｅｌｕｓａｗｏａｒａ）对孔径０．５ｍｍ、孔距５．０ｃｍ，空气压力０．２５ｋｇ／ｃｍ２固定气泡幕的反应。结果表明，气泡幕对两种海水鱼都有显著的阻拦作用，平均阻拦率分别为黑鲷７５．１％、青石斑鱼８２．４％。分析显示，气泡幕对两种鱼的阻拦率间无显著差异。在本实验中，该两种鱼对气泡幕均无明显的适应现象     

对称式布置锚链系统的线性化处理

用悬链线方程求解了不同锚链状态的锚链力 ,并用多项式回归了锚链力与锚固点位移的关系 ,由此求得锚链恢复力刚度系数。分析了对称式布置锚链系统的非线性程度 ,阐述对称式布置锚链系统所提供的恢复力作线性化处理的可行性及方法 ,并给出了对称布置锚链系统的线性刚度矩阵。为各类受对称式布置锚链系统约束的浮动结构物的动力分析提供了理论依据     

小直径组合桩的波浪力实验分析

本文给出小直径孤立桩、两个桩和2×2个桩的波浪作用力实验结果。在波浪水槽中以0°,45°,90°三个波浪方向测量了各桩所受的纵向力和横向力,文中讨论了组合桩之间的干扰效应,给出了干扰系数随KC数和桩距的变化。