地下水在引发边坡病害中的作用

人们普遍认为由于地下水的浸泡降低滑带土的抗剪强度值是导致边坡失稳的内部机制。文章以云南元磨公路边坡为实例，对其进行了探究，发现病害边坡主要滑带土的天然含水量与其剪切试验所得的内聚力和内摩擦角之间并没有明显的线性关系。于是，文章采用极限平衡方程从理论上论述了地下水在边坡失稳过程中的力学作用，并对比边坡开挖前后入渗系数值的变化幅度，揭示出工程活动与降雨共同对边坡破坏的作用机制。     

太平洋板块俯冲对中国大陆的影响

在中国大陆及周边地区ITRF2000速度场的基础上,建立欧亚板块整体旋转与线性应变运动模型,得到中国大陆及邻区的局部形变场,分析此形变场发现东北块体和华北块体东部地壳存在一致的向西或北西西向运动,平均运动速率东北为2.9 mm/a,华北东部为1.4 mm/a,推测这是太平洋板块向欧亚板块俯冲的影响。其影响范围仅限于东北和华北块体,影响较大的是120°E以东和40°N以北地区。并分析太平洋板块俯冲对中国大陆影响的表现形式和形成机制。     

西安市气候变暖与城市热岛效应问题研究

选取1961—2003年西安站和周围4站月平均气温资料, 利用西安站与周围4站气温距平滑动平均变化趋势的差异, 发现该站平均气温有两个明显的上升期, 热岛效应使西安站平均升温1.07 ℃, 并建立了西安市城市热岛效应模型。在此基础上分离了气候变暖过程中由于城市热岛效应引起的增温作用。     

中国人工增雨研究进展

随着全球气候变暖的加剧,水资源短缺问题表现得越来越突出,如何有效地开发利用空中水资源已成为人们关注的热点问题之一。本文回顾了人工增雨的发展历史,概述了当今国内外人工增雨的发展状况,归纳了各地区云状、积云特征、液态含水量、冰晶浓度等云物理特征,并在此基础上对我国各地区尤其是西北地区的增雨潜力进行了分析,最后归纳总结了人工增雨的常用手段、经验和检验人工增雨效果的方法。     

Distribution and fractionation mechanism of stable carbon isotope of coalbed methane

The stable carbon isotope values of coalbed methane range widely, and also are gener- ally lighter than that of gases in normal coal-formed gas fields with similar coal rank. There exists strong carbon isotope fractionation in coalbed methane and it makes the carbon isotope value lighter. The correlation between the carbon isotope value and Ro in coalbed methane is less obvious. The coaly source rock maturity cannot be judged by coalbed methane carbon isotope value. The carbon isotopes of coalbed methane become lighter in much different degree due to the hydrodynamics. The stronger the hydrodynamics is, the lighter the CBM carbon isotopic value becomes. Many previous investigations indicated that the desorption-diffusion effects make the carbon isotope value of coalbed methane lighter. However, the explanation has encountered many problems. The authors of this arti- cle suggest that the flowing groundwater dissolution to free methane in coal seams and the free methane exchange with absorbed one is the carbon isotope fractionation mechanism in coalbed methane. The flowing groundwater in coal can easily take more 13CH4 away from free gas and com- paratively leave more 12CH4. This will make 12CH4 density in free gas comparatively higher than that in absorbed gas. The remaining 12CH4 in free gas then exchanges with the adsorbed methane in coal matrix. Some absorbed 13CH4 can be replaced and become free gas. Some free 12CH4 can be ab- sorbed again into coal matrix and become absorbed gas. Part of the newly replaced 13CH4 in free gas will also be taken away by water, leaving preferentially more 12CH4. The remaining 12CH4 in free gas will exchange again with adsorbed methane in the coal matrix. These processes occur all the time. Through accumulative effect, the 12CH4 will be greatly concentrated in coal. Thus, the stable carbon isotope of coalbed methane becomes dramatically lighter. Through simulation experiment on wa- ter-dissolved methane, it had been proved that the flowing water could fractionate the carbon isotope of methane, and easily take heavy carbon isotope away through dissolution.     

Variations of <Emphasis Type="Italic">δ</Emphasis><Superscript>18</Superscript>O in precipitation from the Muztagata Glacier,East Pamirs

Expeditions to Muztagata (in the eastern Pamirs) during the summer seasons of 2002 and 2003 collected precipitation samples and measured their oxygen isotopes. The δ ¹⁸O in precipitation displays a wide range, varying from −17.40‰ to +1.33‰ in June-September 2002 and from −22.31‰ to +4.59‰ in May-August 2003. The δ ¹⁸O in precipitation correlates with the initial temperature of precipitation during the observing periods. The positive correlation between δ ¹⁸O and temperature suggests that δ ¹⁸O can be used as an indicator of temperature in this region. The δ ¹⁸O values in fresh-snow samples collected from two snow events at different elevations on the Muztagata Glacier show a strong “altitude effect”, with a ratio of nearly −0.40% per 100 m from 5500 m to 7450 m.     

防震减灾网络宣传工作不容忽视--网上一则热帖带来的启发

本文结合我国互联网使用现状和网络对现实生活的影响,对网络在地震宣传方面的重要作用进行论证,提高决策人员和管理人员对地震专业网站建设的重视度。     

An approximate analytical solution for the deposition of heavy particles released from an elevated line source

This work re-examines and further develops an analytical solution for the deposition swath of heavy particles released in the atmosphere from an elevated source over uniform terrain, correcting the particle diffusivity for the crossing trajectory effect. The revised (approximate) analytical solution proves to be accurate within 20% over a wide range of micrometeorological conditions and particle size, despite its neglect of the turbulence component of the deposition flux. It compares very satisfactorily with experimental data and with the simulations of a Lagrangian stochastic model, provided the variable U(H)/w _g ≤7 (ratio of the mean horizontal wind speed at source height to the particle settling velocity). In this domain of validity, simple formulae relating the statistics of the deposition swath to U(H)/w _g are derived.     

PHC管桩挤土效应试验研究

PHC管桩通常为挤土沉桩模式,因而沉桩过程中的挤土效应研究对设计、施工具有重要意义。通过对PHC管桩打桩前后原位地基土变化情况的测试、打桩的监测以及孔隙水压力增长与消散的监测等试验研究,分析了PHC管桩沉桩挤土效应,为工程设计及施工提供可借鉴的依据。     

爆破动力作用下边坡稳定性的积分解法与应用

岩质边坡在爆破开挖过程中的稳定问题是一个亟待解决的重要问题。对实际工程进行监测,得到适合该地区的能反应高程效应的爆破地震波传播规律,并采用拟静力法计算爆破地震惯性力,提出边坡在爆破动力作用下稳定安全系数的新计算方法———积分法,同时使用MATLAB程序搜索边坡最危险滑裂面并计算最小安全系数。实例证明,此方法是分析边坡动力稳定性的有效方法之一。