岩石物性与岩体结构物性研究进展

利用地球物理属性定量化研究岩体结构的成果在国内外较少见。由于风化和构造等原因,浅层岩石与一定范围内岩体的地球物理性质有很大的差别。本文从Archie公式出发介绍岩石物性研究现状,在岩体结构和工程物探研究的基础上,除了介绍岩体结构物性的概念和研究现状外,还分析了以岩心为约束条件下电阻率与波速联合的研究现状,初步探索后认为在工程上能用各种地球物理参数帮助精确描述岩体结构,因此岩体结构物性是一个新的研究方向。     

江汉平原北部汉水以东地区新石器晚期文化兴衰与环境的关系

新石器晚期江汉平原北部汉水以东地区成为长江中游的文化核心区,出现了文化高度繁荣又快速衰落的逆转,处于发展初期的区域文明走向崩溃。文章基于屈家岭剖面常量元素氧化物和TOC含量的分析结果,综合多种环境要素,探讨汉水下游地区全新世中晚期地貌、气候、水文等环境变化与文化兴衰的关系。研究认为,该地区5.4～4.6kaB.P.的气候整体暖湿,晚期暖湿程度有所降低;4.6～4.2kaB.P.气候较为稳定,温暖湿润程度有所回升; 4.2～2.7kaB.P.气候处于持续变干凉阶段; 2.7～0.5kaB.P.气候温湿程度开始回升,并略有波动,但比4.2kaB.P.前仍然偏干凉。以岗状平原为主的江汉平原北部地区优越的地理环境,整体暖湿的气候,为屈家岭文化、石家河文化的高度繁荣提供了环境基础,该时期的聚落数量和分布密度达到了长江中游新石器时期的最高峰。石家河晚期的气候变干变凉,对文化发展产生了一定影响,但不是石家河文化衰落的主要原因。该地区5～3kaB.P.的水位存在波动上升的趋势,这种变化主要受构造沉降、全新世以来海面上升和泥沙淤积的控制。江湖水位的波动上升而引起的洪患加剧,及人类活动向地势低平的江汉平原腹地扩展,这种水文过程和社会发展过程的矛盾,到石家河文化晚期尤为突出,可能是导致石家河文化走向衰落的主要原因。该地区内部或同其他地区之间的冲突可能加速了石家河文化的崩溃。     

华南陆块陆内成矿作用的一些科学问题

华南陆块由扬子地块和华夏地块组成,是全球罕见的世界级多金属成矿省,成矿潜力巨大。华南陆块的形成和演化,受到了很有特色的陆内大陆动力学过程的影响,其中的晚古生代地幔柱成矿系统、中生代大面积低温成矿系统、中生代大花岗岩省成矿系统等陆内成矿系统,在全球背景中很有特色,是全球研究陆内成矿作用的理想基地。对华南陆块地质历史时期的大陆动力学过程如何制约上述成矿作用的发生,以往已开展不同程度的研究并取得重要成果。笔者在论述这些研究进展的基础上,提出了三大成矿系统需要进一步研究的一些科学问题。     

A thermodynamic model for calculating methane solubility, density and gas phase composition of methane-bearing aqueous fluids from 273 to 523 K and from 1 to 2000 bar

A thermodynamic model is presented to calculate methane solubility, liquid phase density and gas phase composition of the H₂O-CH₄ and H₂O-CH₄-NaCl systems from 273 to 523 K (possibly up to 573 K), from 1 to 2000 bar and from 0 to 6 mol kg⁻¹ of NaCl with experimental accuracy. By a more strict theoretical approach and using updated experimental data, this model made substantial improvements over previous models: (1) the accuracy of methane solubility in pure water in the temperature range between 273 and 283 K is increased from about 10% to about 5%, but confirms the accuracy of the Duan model [Duan Z., Moller N., Weare J.H., 1992a. Prediction of methane solubilities in natural waters to high ionic strength from 0 to 250 °C and from 0 to 1600 bar. Geochim. Cosmochim. Acta56, 1451-1460] above 283 K up to 2000 bar; (2) the accuracy of methane solubility in the NaCl aqueous solutions is increased from >12% to about 6% on average from 273 K and 1 bar to 523 K and 2000 bar; (3) this model is able to calculate water content in the gas phase and liquid phase density, which cannot be calculated by previous models; and (4) it covers a wider range of temperature and pressure space. With a simple approach, this model is extended to predict CH₄ solubility in other aqueous salt solutions containing Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl⁻ and , such as seawater and geothermal brines, with excellent accuracy. This model is also able to calculate homogenization pressure of fluid inclusions (CH₄-H₂O-NaCl) and CH₄ solubility in water at gas-liquid-hydrate phase equilibrium. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm.     

地下水在弱膨胀性土边坡稳定中的影响

地下水是影响边坡稳定一个重要因素,主要体现为内、外两个方面的影响。经常考虑的地下水对边坡地层重度、强度等方面的影响属于内的方面;地下水还可能对边坡岩土体产生如浮托力、静水压力、动水压力、渗透力等附加力属于外的方面。通过对一弱膨胀性土边坡失稳各阶段、各影响因素下的分析,阐述了地下水在弱膨胀性土边坡稳定分析中内、外方面的不利影响。并得出结论：在边坡稳定分析时,仅考虑地下水对地层重度、抗剪强度等指标的影响,其分析结果偏于不安全;尤其是边坡地层为弱膨胀性土时,浸水后强度大幅下降,应采用浸水试验指标进行边坡稳定性复核;其次还应考虑地下水渗流排泄对边坡产生的附加荷载。     

煤矿床工程地质勘查中岩石质量指标(RQD)存在问题的探讨

岩石质量指标(RQD)是评价岩体完整性及质量分级的一个重要指标。针对矿区工程地质勘查规范中推荐的岩体质量评价方法,详细分析了岩石质量指标(RQD)在用于岩体分类与评价中存在的岩心长度的计算、采取率、硬度和结构对其赋值大小的影响,以及对规范理解的差异,提出了解决这些问题的有效方法与途径,为岩石质量指标(RQD)的正确应用及煤矿床岩体质量合理评价做了有益的探讨。     

Numerically modelling groundwater in an arid area with ANN‐generated dynamic boundary conditions

Groundwater is sensitive to the climate change and agricultural activities in arid and semi‐arid areas. Over the past several decades, human activities, such as groundwater extraction for irrigation, have resulted in aquifer overdraft and disrupted the natural equilibrium in these areas. Regional groundwater simulation is important to determine appropriate groundwater management policies, and numerical simulation has become the most popular method. However, most groundwater models were developed with static boundary conditions. In this research, the Minqin oasis, an arid region located in northwest China, was selected as the study area. An artificial neural network (ANN) was developed to simulate effects of weather conditions, agricultural activities and surface water on groundwater level in a dynamic boundary of the domain. Subsequently, a groundwater numerical model, named ANN‐FEFLOW model, was developed, with a dynamic boundary condition defined by the ANN model. The verifying results showed that the model has higher precision, with a root mean square error (RMSE) of 0·71 m, relative error (RE) of 17·96% and R² of 0·84 relative to the great groundwater change. Furthermore, the groundwater model has higher precision than the conventional groundwater model with static boundary condition, particularly in the area near the dynamic boundary. This study demonstrated that dynamic boundaries can improve the precision of the regional groundwater model in an arid area and that ANN can provide higher accuracy prediction capability for groundwater levels with dynamic boundary. Copyright © 2010 John Wiley & Sons, Ltd.     

An Analytic Model of Galactic Winds and Mass Outflows

Galactic winds and mass outflows are observed both in nearby starburst galaxies and in high-redshift star-forming galaxies. We develop a simple analytic model to understand the observed superwind phenomenon with a discussion of the model uncertainties. Our model is built upon the model of McKee & Ostriker for the interstellar medium. It allows one to predict how properties of a superwind, such as wind velocity and mass outflow rate, are related to properties of its starforming host galaxy, such as size, gas density and star formation rate. The model predicts a threshold of star formation rate density for the generation of observable galactic winds. Galaxies with more concentrated star formation activities produce superwinds with higher velocities. The predicted mass outflow rates are comparable to (or slightly larger than) the corresponding star formation rates. We apply our model to both local starburst galaxies and high-redshift Lyman break galaxies, and find its predictions to be in good agreement with current observations. Our model is simple and so can be easily incorporated into numerical simulations and semi-analytical models of galaxy formation.     

射电脉冲星搜寻工作的进展

评述了射电脉冲星搜寻及观测研究的巨大贡献和重要意义，分析了影响脉冲星搜寻工作的几个关键因素（如灵敏度，色散，观测频率及设备等），着重介绍和分析了自发现脉冲星（特别是发现第一颗秒脉冲星）以来所进行的卓有成效的脉冲星搜寻工作（包括脉冲星的早期寻，毫秒脉冲星的初期搜寻，高银续脉冲星搜寻，定向搜寻以及进一步的广域深空搜寻等）的情况，结果，意义和进展。