Influence of Inter-Particle Distance, Entrapped Water Volume and Salinity of Water on the Escape Velocity of Particles on a Riverbank

The mechanism of erosion of a riverbank is not easy to analyze and each sediment particle is under influence of number of forces. Among all these forces, force of cohesion between the particles plays a very dominant and significant role, and, till date, not much progress has been made to analyze this force in a deterministic manner. A particle is bound to its neighboring particles under this force of cohesion. In this paper, the analysis of forces acting on a particle on a riverbank has been made with a model called the Truncated Pyramid Model. A particle requires a certain velocity to escape from the riverbank and determination of the escape velocity can pave the way for finding out other parameters like entrainment rate, erosion coefficient and so on. Calculation and estimation of riverbank erosion rate is an important aspect of river basin management. In this paper it has been shown that the escape velocity is dependent on certain micro-level parameters like inter-particle distance and volume of the water bridge between two adjacent particles. Also, for saline water the particle requires less velocity to escape compared to the pure-water scenario. The findings of the present paper exactly fall in line with the results of another paper where the researchers showed that cohesive force between the particles decreases as water turns from pure to impure.

基于Dijkstra算法的煤矿水灾时期最优逃生路径设计

煤矿水灾事故发生后,最棘手的问题就是如何能在最短的时间内实现安全逃生。本文通过在台东山煤矿矿工井下的实际测量,得出井下巷道的类型、坡度、风速、是否设置局部障碍物等对巷道通行难易程度影响的大小,还提出了一种新型水中逃生速度曲线模型,得出不同水位高度不同身高对巷道通行时间的影响大小,继而得出当量长度的计算公式。本文还提出了安全系数的概念,只能当巷道的安全系数值大于0.5时才具备逃生条件。然后提出了加入等高线数值考量的Dijkstra算法最优路径的求取方法,多个安全逃生出口的K则最优路径的优化,以及对K则最优路径提出了新的理解,进行了延伸。最后以台东山煤矿基础数据,以1.7 m平均身高为例,对最优逃生路径的求取进行了实验验证,对实际煤矿水灾时期的逃生具有重大的指导意义。

多层砂岩油藏可视化模型水驱油物模实验研究

为了获得更为直观的多层砂岩油藏水驱油渗流特征和机理,结合实际油藏地质特征,设计制备了一种大尺度可视化砂箱物理模型,进行了不同注水方式、不同注水速度的水驱油实验,考察了不同注采方式、不同注入速度对水驱油效率的影响,以及水驱油过程中的油水运动分布特征。该模型具有设计尺寸大、模拟程度高及直观可视等特点,较其他模型更具代表性。通过模拟NP油田某区块砂岩地层,根据几何相似、井型相同、层序韵律相同、流体黏度相同的原则,更加真实的模拟地层条件。实验结果表明,不同的注水方式及注水速度对模型的采收率有较大影响。采油井数多,单井控制面积小,采收率略高;而注水速度低,油井见水晚,含水率上升缓,可以有效提高采收率,这一过程也反映了重力分异的影响。水驱特征曲线拟合表明,该实验过程符合水驱特征,能够较准确地预测可采储量及采收率。

土壤中重金属迁移数值仿真与参数灵敏度分析

对北京西郊不同地点,土壤中汞吸附和迁移特性进行了实验研究。通过批次实验得到了汞的静态等温吸附系数。经过连续注入,得到了示踪离子(Br)和汞的穿透曲线。分别采用对流弥散模型(CDE)和两点非平衡吸附模型(TSN)对实验室土柱中的重金属迁移的动态行为进行了数值仿真模拟,并探讨了孔隙流速与阻滞因子的关系。通过模型的灵敏度分析,参数V、R、β控制着穿透时间,而ω则控制着穿透曲线的峰值。数值仿真研究表明:采用TSN模型对北京西郊重金属Hg的迁移行为进行研究更为合理。

矿井水灾逃生路径建模及路径规划研究

综合不同水位下,不同身高特征对矿工在矿井突水时期逃生速度的影响,分析了身高不同的矿工在不同水位下的行走速度与水位之间的函数关系,提出并建立了相应的关系函数模型——阻滞型水中逃生速度曲线数学模型,并基于该模型计算影响矿工逃生速度的影响系数;同时为了动态描述巷道的安全通行能力,根据模糊评价原理,引入了相应的安全系数;结合巷道实际道路特征,优化了矿井水灾逃生数学模型。优化后的数学模型不仅可以针对不同身高特征的矿工设计最优逃生路径,也可以在人员较多时采用平均身高设计最优逃生路径。

Study on the mechanism of transport of heavy metals in soil in western suburb of Beijing

Researchers are paying more and more attention to the adsorption and transport of heavy metals in soil. In this study, laboratory experiments were performed to investigate the characteristics of adsorption and transport of mercury in soils of different locations in the western suburb of Beijing. To characterize the adsorption mechanism of mercury in soil, adsorption isotherms were determined through a batch experiment. Soil column experiments were performed in saturated soil under steady-state flow at a specific water head. The breakthrough curves (BTC) for the tracer (bromine) and mercury were obtained after continuous input. Moreover, two solute transport models [convection-dispersion equation model (CDE) and two-site non-equilibrium model (TSN)] were used to simulate heavy metal movement in soil on a laboratory column scale. According to the simulating results, we explored which model is more adapted to simulate the movement of heavy metals in saturated soil in the western suburb of Beijing.

基于线性水平连续介质速度模型的南海中央海盆深水区速度分析

基于线性水平连续介质模型中速度随深度及双程走时的变化规律，通过3个模型实验的结果，为速度分析过程（叠加速度（Vstk）的拾取、层速度（Vn）的计算、平均速度（Va）的计算和时深转换）提供了指导依据，并应用于南海中央海盆深水区的速度分析工作中，在保证数据质量和提高工作效率方面取得了明显的效果。