基于随机理论的地下水环境风险评价

针对确定性模型难以描述含水层非均质空间分布的问题,提出基于随机理论的地下水环境风险评价方法。以矩形场地地下水污染风险评价为例,采用蒙特卡罗法生成大量渗透系数随机场,模拟含水层参数各种可能的非均质空间分布,在此基础上建立场地地下水流模型与溶质运移模型,分别计算污染物在地下水中的迁移转化情况。统计大量随机模拟中污染事故发生的频率,当模拟次数足够多时,污染频率收敛于污染概率,污染风险即通过污染概率体现出来。该方法将模型参数设为满足一定分布特征的随机变量,避免了确定性方法得出的武断的评价结果,可为工厂的选址、水源地的选址等工作提供科学指导。     

气动试验法测定渗透系数的可行性分析

基于竖管法测定沉积物渗透系数的原理,设计一种以空气作为流体测定沉积物渗透率的试验方法—气动试验法,将沉积物的空气渗透率(k_a)转换成用水当做流体时测定的渗透系数(K_w)。利用气动试验法和竖管法分别测定3组沙漠砂样和7组河漫滩砂样的渗透系数。试验结果表明,气动试验法测定沉积物的渗透系数可行,与竖管法相比更加方便、快捷,可以解决竖管法耗水、耗时的局限性,可应用于干旱-半干旱地区野外沉积物渗透系数的测定。     

湘西合仁坪金矿床角砾岩的地质特征及形成机制

湘西合仁坪钠长石-石英脉型金矿中,角砾岩普遍发育,主要分布于矿脉中,与金成矿关系密切。在详细的野外观察和室内研究的基础上,文章对合仁坪金矿床中角砾岩的形态、大小及胶结物进行了较系统的研究,并结合角砾岩的矿物组合特征,探讨了该区角砾岩的形成机制。研究表明,合仁坪金矿床中的角砾岩大多数呈原地破裂特征,角砾分选差,成分简单,且角砾之间的拼合性较好,为钠长石、石英等热液矿物所胶结,角砾的长轴方向大致具有定向排列的特点,表现出明显的液压致裂特征,反映出成矿流体的特征。研究区的液压致裂作用具有脉动性,每期液压致裂作用大致可分为应力腐蚀、岩石破碎、裂隙愈合3个阶段。     

An experimental,analytical and numerical study on the thermal efficiency of energy piles in unsaturated soils

Energy piles are bi-functional foundation elements used as structural support as well as ground heat exchangers for shallow geothermal energy systems. Because they are relatively short, energy piles may be partially embedded in unsaturated soils. Saturation conditions influence the thermal properties of the ground and therefore the heat exchange rate, which in turn affects the efficiency of energy piles. This paper combines analytical, experimental and numerical investigations to evaluate the heat exchange rate of energy piles partially or fully embedded in unsaturated soils. The proposed analytical solution is based on the cylindrical heat source theory that treats the soil as a semi-infinite, homogeneous, and isotropic medium. The solution from this theory is multiplied by a function developed analytically in this paper and the outcome is the heat exchange rate for energy piles in unsaturated soils. The proposed function depends on soil saturation, soil and pile thermal properties, and pile geometry. The analytical solution was compared against a finite element solution; which was in turn validated against results from laboratory experiments. Very satisfactory agreements between the analytical, numerical and experimental outputs were observed. The proposed method can be used for a quick and simple evaluation of the efficiency of energy piles in unsaturated conditions. The proposed analytical solution can also be a useful tool for the verification of numerical codes developed for the design of energy piles in unsaturated soils.     

滇中红层软岩微观结构及水理特性试验研究

滇中红层软岩具有成岩作用差、易产生较大变形、遇水易软化、易崩解等特征,本文采用环境扫描电镜试验和水理特性试验,对红层软岩的微观结构特征,崩解、膨胀、软化等水理特性进行了研究。试验结果表明,红层软岩矿物粒间空隙大多被粘土矿物填充,粘土矿物以伊利石和蒙脱石为主,为混层结构,结晶程度相对较差,多数有蚀变的痕迹。具有微小裂隙的红层软岩在1~2次充分饱水烘干后,崩解性开始显现;随着干湿循环次数增加,岩样的质量变化呈减小趋势;干湿循环次数继续增加,崩解性指数趋于平缓。红层软岩由于风化作用影响程度和自然含水率的差异,岩体内部崩解张力具有明显不均匀性。经过自由浸水48h后,红层软岩的单轴抗压强度降低29.83%~58.47%,各地层软化系数在0.4~0.7之间,遇水后呈现显著软化效应。这些结果为红层软岩地区公路工程建设的工程地质研究提供了一定参考。     

Indexing large geographic datasets with compact qualitative representation

This paper develops a new mechanism to efficiently compute and compactly store qualitative spatial relations between spatial objects, focusing on topological and directional relations for large datasets of region objects. The central idea is to use minimum bounding rectangles (MBRs) to approximately represent region objects with arbitrary shape and complexity and only store spatial relations that cannot be unambiguously inferred from the relations of corresponding MBRs. We demonstrate, both in theory and practice, that our approach requires considerably less construction time and storage space, and can answer queries more efficiently than the state-of-the-art methods.     

论多层叠置独立含煤层气系统—— 以贵州织金—纳雍煤田水公河向斜为例

基于贵州织金—纳雍煤田水公河向斜的实测资料,采用地质分析等方法,探讨了煤层气地质条件在垂向上的非均质分布规律,提出和初步论证了“多层叠置独立含煤层气系统”的学术观点。研究表明,上二叠统龙潭组单一煤层甲烷平均含量及相邻主煤层之间含气量梯度均呈波动式变化,煤层埋深—压力系数关系在垂向上分为截然不同的两套系统,层序地层格架中二级层序与含气量梯度的独立分段高度吻合。由此揭示,含煤地层地下流体在不同主煤层之间总体上缺乏交换,导致不同煤层群之间的煤层气系统相对独立。笔者等认为,龙潭组层序地层格架特点奠定了该类系统形成的物性基础,含煤地层与上覆、下伏含水层之间缺乏水力联系而构成了该类系统产生的水文地质基础,即多层叠置独立含气系统是沉积—水文—构造条件耦合控气作用的产物。笔者等也指出,在以三角洲—潮坪—潟湖沉积体系为主的多煤层含煤地层中,该类含气系统可能具有普遍意义。     

Measuring and adjusting the weathering and hydraulic sorting effects for rigorous provenance analysis of sedimentary rocks: a case study from the Jurassic Ashikita Group,south‐west Japan

The present study examines the provenance of the Jurassic Ashikita Group distributed in south‐west Japan, which is composed of the Idenohana, Kyodomari and Sakamoto Formations. Two geochemical diagrams for provenance analysis were utilized, which incorporate full consideration of compositional modifications resulting from weathering (MFW diagram) and hydraulic sorting processes (SiO₂/Al₂O₃–Na₂O/K₂O diagram). The MFW diagram delineates weathering trends of sedimentary rocks and allows estimation of the original source rock composition by tracing the weathering trends backwards to an unweathered domain. Weathering trends of the Idenohana and Kyodomari Formations extend backward to the domain of intermediate and felsic igneous rocks. In contrast, sediments of the Sakamoto Formation do not fit into a linear weathering trend, indicating that the source rock cannot be approximated to igneous rocks. On the SiO₂/Al₂O₃–Na₂O/K₂O diagram, sediments are organized into compositional trends, in which the range reflects compositional variations induced by the hydraulic sorting effect. On this diagram, sediments derived from the igneous and recycled sedimentary provenances can be distinguished by reading the inclination of the trend. By utilizing this principle, source rocks of the Idenohana and Kyodomari Formations are interpreted as igneous rocks and those of the Sakamoto Formation are interpreted as recycled sedimentary rocks. Therefore, these diagrams concurrently estimate the source rock composition through quantifying and adjusting the weathering and sorting effects, and reveal a systematic transition in the provenance of the Ashikita Group. The Idenohana and Kyodomari Formations were supplied chiefly from an igneous provenance, which shifted from intermediate to felsic compositions in stratigraphic order. Whereas, sediments of the Sakamoto Formation were sourced primarily from a recycled sedimentary provenance.     

冲击器射流元件内部流场CFD模拟仿真分析

利用CFD数值模拟手段,对射流元件内部流场进行模拟,并对数据进行分析研究,得出结论为：在空载作用下,元件在一侧出流。赋予不同的主喷嘴流量,元件的属性各参量变化不大,可见,元件结构既定,元件射流附壁属性基本确定。该模拟仿真分析丰富了射流元件内部流动的理论研究,完善了参数设计,这对射流式冲击器的设计理念和理论研究有很好的指导意义。     

高寒地区水工建筑物保温基础抗冻效果分析

高寒地区水工建筑物基础采用EPS板来保温,抵御因地基冻胀而引起的破坏,已取得了明显的效果。采用野外现场模拟,对EPS保温基础进行了四个冬春的观测,取得了现场实测资料及成果。通过对不同密度、厚度的EPS保温基础的温度场变化规律的分析研究,验证了EPS基础保温工法可抑制冻胀的可行性,为进一步完善EPS板的防冻理论和实用经验提供了参考依据。