A study of interaction between surface water and groundwater using environmental isotope in Huaisha River basin

The surface water and groundwater are important components of water cycle, and the interaction between surface water and groundwater is the important part in water cycle research. As the effective tracers in water cycle research, environmental isotope and hydrochemistry can reveal the interrelationships between surface water and groundwater effectively. The study area is the Huaisha River basin, which is located in Huairou district, Beijing. The field surveying and sampling for spring, river and well water were finished in 2002 and 2003. The hydrogen and oxygen isotopes and water quality were measured at the laboratory. The spatial characteristics in isotope and evolution of water quality along river lines at the different area were analyzed. The altitude effect of oxygen isotope in springs was revealed, and then using this equation, theory foundation for deducing recharge source of spring was estimated. By applying the mass balance method, the annual mean groundwater recharge rate at the catchment was estimated. Based on the groundwater recharge analysis, combining the hydrogeological condition analysis, and comparing the rainfall-runoff coefficients from the 1960s to 1990s in the Huaisha River basin and those in the Chaobai River basin, part of the runoff in the Huaisha River basin is recharged outside of this basin, in other words, this basin is an un-enclosed basin. On the basis of synthetically analyses, combining the compositions of hydrogen and oxygen isotopes and hydrochemistry, geomorphology, geology, and watershed systems characteristics, the relative contributions between surface water and groundwater flow at the different areas at the catchments were evaluated, and the interaction between surface water and groundwater was re- vealed lastly.     

Equivalent fixed-base models for soil-structure interaction systems

To simplify the consideration of the soil-structure interaction (SSI) effects, a single degree-of-freedom (SDOF) replacement oscillator has been successfully utilized to represent an SSI system with SDOF structural model. In the present paper, this approximation is first extended to an equivalent fixed-base model with modified system parameters. Based on this generalization, a methodology is then proposed to determine the equivalent fixed-base models of a general multi degree-of-freedom SSI system using simple system identification techniques in the frequency domain. Various fixed-base models are formulated and their accuracy is compared for a five-story shear building resting on soft soil. It is shown that the actual SSI system can be accurately represented with an appropriate fixed-base model.     

相邻结构-地基-土相互作用的分支模态实用研究

本文在提出模态综合二步分析法研究相邻结构－地基－土相互作用的基础上,采用振动特性和实际结构相同的模拟结构,求得上,下部之间的耦合项,将耪合项和地震动一起组成修正地震动,以此作为刚性基础的结构抗震的分析的地震输入,本文为利用专业程序进行相邻结构－地基－土相互作用抗震分析提供了新的途径。     

Sensitivity of seismic structural response to interpretation of soils data

This paper investigates the sensitivity of the predicted seismic response of buildings in a PWR nuclear power station to the potential changes in the techniques and methods of interpreting soil data that have occurred over the last decade. The investigation is based on the soil-structure interaction (SSI) response of a typical PWR reactor building on a soft site during a seismic event. The current techniques and methods of interpretation of soils data tend to lead to a stiffer site with lower soil material damping than the earlier techniques. This leads to an increase in the SSI natural frequencies of typical buildings and an increase in its seismic response. This increase in the seismic response could put into question any seismic design based on seismic loads derived using the previously accepted generic soil data. The paper concludes with a recommendation for further consideration of the proposed departure from the previously accepted soil data.     

中层耗散大气中Rossby波包的非线性相互作用理论

采用弱非线性近似得出中层耗散大气连续谱Ｒｏｓｓｂｙ波包的非线性时空演化方程，讨论了Ｒｏｓｓｂｙ波包的三波相互作用问题．数值计算表明，耗散和非线性的共同效应决定了Ｒｏｓｓｂｙ波包的演变．当一个Ｒｏｓｓｂｙ波包通过大气传播时，它的振幅若超过某个阈值，空间尺度分别比它大和比它小的两个次级Ｒｏｓｓｂｙ波包的振幅会随时间增长．特别当这两个次级波包同时随时空变化时，仅当主波的振幅超过一个更大的阈值，且其群速度介于两次级波包的群速度之间时，两次级波包的振幅才会随时空同时增长，即出现绝对不稳定现象，耗散和３个波包的频率失配都会增大不稳定的阈值．     

水平向不均匀土对箱基动力阻抗的影响

采用薄层元素法和有限单元法,建立了地基-箱形基础动力相互作用的三维分析模型,该模型可考虑箱形基础周围土的不均匀性影响.利用该模型,分析了水平方向不均匀土对箱形基础的水平和摇摆阻抗的影响.分析了水平方向不均匀土的厚度、剪切弹性模量以及材料阻尼比的影响.分析结果表明:水平方向不均匀土使得箱形基础的各种阻抗均降低,特别是阻抗的虚部.水平方向不均匀土对摇摆阻抗的影响较大.水平方向不均匀土的剪切弹性模量的影响较大而其材料阻尼的影响较小.随着水平方向不均匀土的厚度的增加和基础埋深的增加,其影响增大.     

工业结构—设备体系在地震作用下的动力相互作用研究

根据工业结构－设备体系动力相互作用特点，本文提出了利用主，子结构边界耦合矩阵变换的一般建模方法。通过本文作者完成的六种不同类型的结构－设备复合模型体系在我维地震动作用下振动台试验，总结了工业结构－设备动力相互作用的一般规律和特点。     

Evaluation of rainfall–runoff model performance under non-stationary hydroclimatic conditions

ABSTRACT

Understanding of rainfall–runoff model performance under non-stationary hydroclimatic conditions is limited. This study compared lumped (IHACRES), semi-distributed (HEC-HMS) and fully-distributed (SWATgrid) hydrological models to determine which most realistically simulates runoff in catchments where non-stationarity in rainfall–runoff relationships exists. The models were calibrated and validated under different hydroclimatic conditions (Average, Wet and Dry) for two heterogeneous catchments in southeast Australia (SEA). SWATgrid realistically simulates runoff in the smaller catchment under most hydroclimatic conditions but fails when the model is calibrated in Dry conditions and validated in Wet. All three models perform poorly in the larger catchment irrespective of hydroclimatic conditions. This highlights the need for more research aimed at improving the ability of hydrological models to realistically incorporate the physical processes causing non-stationarity in rainfall–runoff relationships. Although the study is focussed on SEA, the insights gained are useful for all regions which experience large hydroclimatic variability and multi-year/decadal droughts.     

Characterization of the dynamic behavior of a concrete arch dam by means of forced vibration tests and numerical models

The characterization of the dynamic behavior of an arch dam, and its evolution throughout the structure's lifetime, provides important data for the safety control process. Forced vibration tests remain a reliable technique for this purpose. The Baixo Sabor dam is a 123 m high arch dam recently built in Portugal. Forced vibration tests were performed before and after the reservoir filling. Two techniques for forced vibration test are compared, discrete frequency scanning, the standard methodology, and continuous frequency scanning (sine sweep), a new proposed methodology, which allowed faster results without loss of precision. For the interpretation of test results two numerical models of the dam-reservoir-foundation system were built, and calibrated with the experimental data. A good match of numerical and experimental results was obtained for the six lowest frequencies and corresponding mode shapes.     

大别苏鲁地区层状地幔反射体及其解释

深反射地震虽然己广泛应用于地壳上地幔调查,然而,来自地幔的反射体在全世界 都还比较少见,尤其是尚未有发现上地幔中多层水平反射体的报道. 近年来,作者用24s 的 深反射地震记录揭示了在大别苏鲁地区岩石圈地幔内存在5组水平的反射体, 表明该区具有 特殊演化作用形成的上地幔组构, 它们可随深度增加分别命名为M1到M5 . 这些反射体不仅 可在地震叠加剖面上看到,有时还可在野外单炮记录上看到. 反射体M1对应Moho面,而M5大 概与现今岩石圈底界对应,根据地热资料,苏鲁热岩石圈厚度约为78km. 其他3个反射体可 能是中生代岩石圈减薄诱发的壳幔作用的结果. 根据岩石学与地球化学的数据,在晚中生代 中国东部岩石圈的厚度约从150km减薄到约60km,在新生代又略微加厚到平均 78km. 这一减 薄作用引起岩浆底侵并在下地壳产生麻粒岩层,而早侏罗纪扬子克拉通向北的陆-陆俯冲又 在上地幔产生榴辉岩层. 在双程走时12s处的反射体M2 则是麻粒岩层与榴辉岩层的边界,它 也是古生代的 Moho面. 反射体 M3 出现在14s 前后,看来是榴辉岩层的底面, 它的下面应 保存有残留的古生代上地幔. 由于新老岩石圈地幔成分不同,其界面产生反射体 M4. 这种 多层岩石圈地幔反射体的存在表明,所研究地区的地幔结构与中国东部中生代岩石圈减薄作 用有关. 同时,由于20世纪80年代以来一直认为上地幔在反射地震上是相对透明的,多层反 射体的发现对这一认识是新的挑战, 表明采用爆炸震源与地震反射新技术有可能揭露岩石圈 地幔内部结构细节,这些细节也是地幔动力学作用的产物.