柱脚可更换的地下结构抗震截断柱技术性能分析

基于功能可快速恢复的抗震韧性设计目标,结合提升中柱水平变形能力的地下结构抗震截断柱技术,提出了可有效避免由于柱脚应力集中产生的破坏和震后可快速更换的地下结构中柱设计思路,其中复合截断中柱与顶、底纵梁采用剪力销栓连接,柱脚部采用局部增强或增韧可更换材料进一步替代。采用数值模型分析了复合柱的承载力、变形能力以及柱脚采用不同材料时对复合柱变形和承载力的影响规律,并与整体现浇柱进行了对比。结果表明:一般截断柱的承载能力明显低于整体现浇柱,但其变形能力远远优于整体现浇柱。随着中柱变形的增加,一般截断柱中柱柱脚位置出现明显的“应力集中”现象,局部增强或增韧材料的采用可有效避免复合截断柱脚部因应力集中而产生的破坏,提高了复合截断柱的水平变形能力。     

水平分层土层系统等效阻尼比的简化计算方法

在实际工程场地中,很多土层可视为水平分层,各层土的物理和力学性质存在差异,其中包括土的振动阻尼比。本文讨论水平分层土层系统的等效阻尼比的近似计算方法,基于5个不同的加权函数推导了10种等效阻尼比的计算公式。通过2个算例,分别以等效阻尼比为参数计算水平分层土层的地震反应,并与准确解相比较,分析了不同等效阻尼比近似计算方法的计算精度。数值结果表明,若等效阻尼比计算方法选择不恰当,会导致土层地震反应的计算结果出现较大误差。针对2种不同类型的水平分层土层,建议采用基于三角形分布的加权函数来计算土层系统的等效阻尼比。     

Major advances in studies of the physical geography and living environment of China during the past 70 years and future prospects

The natural environment provides material essentials for human survival and development. The characteristics,processes, regional differentiation and forcing mechanisms of the elements of the natural environment(e.g. geomorphology,climate, hydrology, soil, etc.) are the main objects of research in physical geography. China has a complex natural environment and huge regional differentiation and therefore it provides outstanding reserach opportunities in physical geography. This review summarizes the most important developments and the main contributions of research in the physical geography and human living environment in China during the past 70 years. The major topics addressed are the uplift of the Tibetan Plateau and the evolution of its cryosphere, the development of fluvial systems, the acidification of the vast arid region of the Asian interior, variations in the monsoon and westerly climate systems on multiple timescales, the development of lakes and wetlands, the watershed system model, soil erosion, past human-environment interactions, biogeography, and physical geographic zonality. After briefly introducing international research developments, we review the history of research in physical geography in China, focusing on the major achievements and major academic debates, and finally we summarize the status of current research and the future prospects. We propose that in the context of the national demand for the construction of an ecological civilization, we should make full use of the research findings of physical geography, and determine the patterns and mechanisms of natural environmental processes in order to continue to promote the continued contribution of physical geography to national development strategies, and to further contribute to the theory of physical geography from a global perspective.     

柴达木盆地北缘反S形褶皱冲断带变形机制的物理模拟研究

阿尔金断裂走滑变形的侧向传递十分有限,难以解释柴达木盆地北缘反S形褶皱冲断带的形成。本文设计的一组具有不同性质基底条件的弧形边界砂箱实验表明:刚性块体边界形态控制了褶皱冲断带走向和构造格局,同时基底力学性质也有部分影响作用,因而可用“刚性块体弧形边界联合作用”来解释其形成,即:1)冷湖反S形褶皱冲断带的形成是赛什腾山前弧形边界与昆特依凹陷弧形边界联合作用的结果;2)鄂博梁反S形褶皱冲断带的形成是昆特依凹陷与一里坪凹陷弧形边界联合作用的结果;3)位于一里坪凹陷南侧、与阿尔金断裂左行走滑变形呈反牵引关系的褶皱冲断带则与该凹陷西南侧向南西突出的弧形边界有关。     

基于无人机摄影测量技术的地震地表破裂带定量参数提取 ——以1709年中卫南M7½地震为例

本文首先介绍了无人机摄影测量技术获取数字高程模型(digital elevation model,缩写为DEM)和地貌数据(正射影像)的作业流程,对比分析了三种不同质量密集点云生成的DEM在水平位置和高程上的差异;然后以1709年中卫南M7?大地震的主体地表破裂带为例,提取其上地震断层的垂直位错量和水平位移量.研究结果...     

Using Sr isotopes to trace the geographic origins of Chinese mitten crabs

Identifying the geographic origins of Chinese mitten crabs is important for food safety and fair market competition. In this study, we used strontium (Sr) isotopes as a tool to trace the geographic origins of Chinese mitten crabs. Chinese mitten crabs, water, and different types of crab feed were collected from four different lakes for Sr isotope analyses. The results showed that the Sr isotope compositions of the different parts from one single crab were consistent within error, indicating that any piece of a crab could be used to represent the Sr isotope characteristics of the whole crab. The Sr isotope compositions of Chinese mitten crabs from the same lake were consistent within the analytical error, and the values were similar to the Sr isotope composition of the water from the same lake. However, the Sr isotope compositions of water and crabs from different lakes are significantly different. Therefore, the Sr isotope compositions of Chinese mitten crabs are mainly controlled by lake water composition, while the impact of feed is limited. This study provides an effective method for tracing the geographic origins of Chinese mitten crabs.

     

生态输水条件下塔里木河下游断面尺度地下水流数值模拟

由于中国西北地区地表水资源有限,地下水则成为重要的备用水资源,而地表水和地下水转化过程及其耦合模拟是水资源开发利用和科学评价的基础,因此,为了准确反映塔里木河下游间歇性生态输水后地下水的动态变化,以塔里木河下游英苏断面为例,基于Boussinesq方程建立了改进的地下水动力学(GH-D2)模型,模拟了塔里木河下游绿色走廊典型断面地下水对全时段(2000-2015年)间歇性生态输水的响应过程。结果表明,尽管Boussinesq方程的GH解能较好地模拟地下水位的瞬态变化,但模拟地下水位多年变化的结果并不理想,而改进的GH-D2模型考虑了间歇性生态输水对地下水位变化的滞后效应,对长时间尺度地下水位变化的模拟具有较好的效果。与GH和GH-D1模型相比,GH-D2模型模拟的地下水位值更接近于观测值,这将对塔里木河下游实施科学合理的生态输水计划以及生态恢复和重建策略提供关键的技术支撑。     

A 1-g shaking table investigation on response of a micropile system to earthquake excitation

Acta Geotechnica - Considering the increasing applications of micropile systems in seismically active areas, a better understanding of their seismic performance and the key controlling factors is...     

Mineralization age and sources of ore‐forming material of the Nanmushu Zn‐Pb deposit in the Micangshan Tectonic Belt at the northern margin of the Yangtze Craton,China: Constraints from Rb‐Sr dating and Sr‐Pb isotopes

The Nanmushu Zn‐Pb deposit, hosted by the Neoproterozoic Dengying Formation dolostone, is located in the eastern part of the Micangshan tectonic belt at the northern margin of the Yangtze Craton, China. This study involves a systematic field investigation, detailed mineralogical study, and Rb‐Sr and Pb isotopic analyses of the deposit. The results of Rb‐Sr isotopic dating of coexisting sphalerite and galena yield an isochron age of 486.7 ± 3.1 Ma, indicating the deposit was formed during the Late Cambrian to Early Ordovician. This mineralization age is interpreted to be related to the timing of destruction of the paleo‐oil reservoir in the Micangshan tectonic belt. All initial ⁸⁷Sr/⁸⁶Sr ratios of sphalerite and galena (0.70955–0.71212) fall into the range of the Mesoproterozoic Huodiya Group basement rocks (0.70877–0.71997) and Dengying Formation sandstone (0.70927–0.71282), which are significantly higher than those of Cambrian Guojiaba Formation limestone (0.70750–0.70980), Cambrian Guojiaba Formation carbonaceous slate (0.70766–0.71012), and Neoproterozoic Dengying Formation dolostone (0.70835–0.70876). Such Sr isotope signatures suggest that the ore strontium was mainly derived from a mixed source, and both of the Huodiya Group basement rocks and Dengying Formation sandstone were involved in ore formation. Both sphalerite and galena are characterized by an upper‐crustal source of lead (²⁰⁶Pb/²⁰⁴Pb = 17.849–18.022, ²⁰⁷Pb/²⁰⁴Pb = 15.604–15.809, and ²⁰⁸Pb/²⁰⁴Pb = 37.735–38.402), and their Pb isotopes are higher than, but partly overlap with, those of the Huodiya Group basement rocks, but differ from those of the Guojiaba and Dengying Formations. This suggests that the lead also originated from a mixed source, and the Huodiya Group basement rocks played a significant role. The Sr and Pb isotopic results suggest that the Huodiya Group basement rocks were one of the most important sources of metallogenic material. The geological and geochemical characteristics show that the Nanmushu Zn‐Pb deposit is similar to typical Mississippi Valley type, and the fluid mixing may be a reasonable metallogenic mechanism for Nanmushu Zn‐Pb deposit.     

“地理国情监测”服务县域生态环境监测及动态分析

走生态优先、绿色发展之路,是推动经济发展的基本要求。生态环境保护是我国当前及今后长期坚持的一项基本任务,已居于压倒性的战略地位。本文以多期地理国情监测数据为主要数据源,开展县域生态环境监测及动态评价,推进地理国情普查与监测成果的社会化应用。