混凝土膨胀剂使用中存在的问题及解决措施

混凝土膨胀剂具有补偿混凝土干燥收缩的效果,但在地下室防水混凝土工程中,使用效果不理想,存在掺加膨胀剂后地下室底板和外墙出现混凝土开裂渗漏的现象。本文从设计源头,力求全面地、准确有效地提出解决措施。     

含初始缺陷地铁隧道的抗震动力学行为研究

针对含初始缺陷的既有地铁隧道受邻近穿越隧道施工影响的首都地铁隧道工程背景,基于有限差分方法,通过对既有地铁车站结构受邻近隧道穿越后的抗震性能研究,揭示其抗震动力响应机理。结果表明,在邻近隧道穿越影响下,含初始缺陷的既有隧道各薄弱控制点在地震作用下位移和应力动力时程的波动趋势具有相似性,说明衬砌结构是整体运动的,其位移、应力较穿越前均有所增加,边墙和仰拱在穿越后抗震性能影响最大,剪切破坏主要以车站结构周边土体为主,新线穿越后其剪切破坏分布范围有所增大,应进行注浆加固处理,与自身结构刚度相匹配,提高抗震能力。     

关中盆地地下水环境地质问题研究

陕西关中盆地做为西部大开发的一个核心支撑区,而水资源紧缺成为经济进一步发展的制约因素。根据盆地内主要城市地下水的开采利用现状及供水结构变化,系统地分析盆地内的地下水不合理开采所导致地下水降落漏斗、地裂缝、地面沉降、渍水及土壤盐渍化等环境地质问题,最后提出可行的防治措施,以恢复生态环境良性循环。     

蓬莱市土地储备出让工作运行与探讨

土地储备出让工作是我国为改变传统的土地供应模式、规范调控土地市场、优化土地资源配置,实现土地收益的最大化而做出的重大创新。通过调查研究并结合蓬莱市土地储备出让工作运行实际,就土地储备出让过程中存在的问题作出分析并提出相应建议。     

Interactions of aquaculture and waste disposal in the coastal zone

Throughout the world, the coastal zones of many countries are used increasingly for aquaculture in addition to other activities such as waste disposal. These activities can cause environmental problems and health problems where they overlap. The interaction between aquaculture and waste disposal, and their relationship with eutrophication are the subjects of this paper. Sewage discharge without adequate dispersion can lead to nutrient elevation and hence eutrophication which has clearly negative effects on aquaculture with the potential for toxic blooms. Blooms may be either toxic or anoxia-causing through the decay process or simply clog the gills of filter-feeding animals in some cases. With the development of aquaculture, especially intensive aquaculture, many environmental problems appeared, and have resulted in eutrophication in some areas. Eutrophication may destroy the health of whole ecosystem which is important for sustainable aquaculture. Sewage discharge may also cause serious public health problems. Filter-feeding shellfish growing in sewage-polluted waters accumulate micro-organims, including human pathogenic bacteria and viruses, and heavy metal ion, presenting a significant health risk. Some farmed animals may also accumulate heavy metals from sewage. Bivalves growing in areas affected by toxic algae blooms may accumulate toxins (such as PSP, DSP) which can be harmful to human beings.     

Kinematic dynamo action in a sphere: Effects of periodic time-dependent flows on solutions with axial dipole symmetry

Choosing a simple class of flows, with characteristics that may be present in the Earth's core, we study the ability to generate a magnetic field when the flow is permitted to oscillate periodically in time. The flow characteristics are parameterised by D, representing a differential rotation, M, a meridional circulation, and C, a component characterising convective rolls. The dynamo action of all solutions with fixed parameters (steady flows) is known from earlier studies. Dynamo action is sensitive to these flow parameters and fails spectacularly for much of the parameter space where magnetic flux is concentrated into small regions, leading to high diffusion. In addition, steady flows generate only steady or regularly reversing oscillatory fields and cannot therefore reproduce irregular geomagnetic-type reversal behaviour. Oscillations of the flow are introduced by varying the flow parameters in time, defining a closed orbit in the space ( D,?M ). When the frequency of the oscillation is small, the net growth rate of the magnetic field over one period approaches the average of the growth rates for steady flows along the orbit. At increased frequency time-dependence appears to smooth out flux concentrations, often enhancing dynamo action. Dynamo action can be impaired, however, when flux concentrations of opposite signs occur close together as smoothing destroys the flux by cancellation. It is possible to produce geomagnetic-type reversals by making the orbit stray into a region where the steady flows generate oscillatory fields. In this case, however, dynamo action was not found to be enhanced by the time-dependence. A novel approach is being taken to solve the time-dependent eigenvalue problem where, by combining Floquet theory with a matrix-free Krylov-subspace method, we can avoid large memory requirements for storing the matrix required by the standard approach.     

四川眉山芒硝矿主要环境地质问题与防治对策

眉山市芒硝矿开采和生产过程中的主要环境地质问题是矿区地下水和地表水疏干、污染及矿区土壤污染等,影响了矿山及附近居民的生产生活,威胁了人民的身体健康。本文在芒硝矿山环境地质问题调查的基础上,针对存在的主要问题,提出了防治措施。     

烟台市土地使用过程中存在的问题及建议

近年来,烟台市不断深化土地使用制度改革,引入市场竞争机制,规范土地市场管理,较好地发挥了市场机制配置土地资源的作用,促进了经济和城市建设的发展。但随着全市社会经济的快速发展,对土地的需求也越来越多,土地使用过程中一些新的问题和矛盾也凸显出来。该文通过分析烟台市土地使用状况以及土地使用的特点,找出了土地使用过程中存在的问题,并结合实际情况提出了相应的对策建议。     

“入世“给地质勘查业带来的机遇与挑战

我国"入世"后,外国跨国公司必然会进入我国的地质市场.对比,本文指出了国内地勘单位与跨国公司相比,在技术力量、资本和管理水平等方面存在的问题,以及它们的介入所带来的不利影响和机遇,针对这些问题提出了具体的对策及所采取的措施.