细尾矿砂非饱和渗流稳态含水率二维解析解

为准确描述非饱和细尾矿砂内部含水率的空间分布规律,采用解析方法求解了非饱和尾矿砂的二维Richards方程,探讨了解析求解过程中方程和求解区域简化的思路,介绍了非饱和细尾矿砂含水率空间分布的实验结果,采用混沌粒子群优化算法计算了求解过程中引入的常数。研究结果表明:解析解具有无穷级数的形式,且级数的系数具有很好的收敛性,非饱和细尾矿砂含水率在水平和竖直方向上的分布均近似服从指数函数,混沌粒子群优化算法的误差收敛性明显,利用解析模型得到的各点含水率计算值与实验测量值均符合的比较好。所得解析公式能够很好地描述非饱和细尾矿砂内部含水率的空间分布规律。     

Seepage from deep bedded and poultry litter systems

Abstract

The work reported indicates that there could be a potential of ground water pollution by NO₃‐N from turkey facilities built on both sandy and clay soils. At four different depths (30.54, 61.08, 91.62, and 122.16 cm), the NO₃‐N levels for the clay soil were 1572, 497, 66, and 28 ppm, and those for the sandy soil were 293, 425, 324, and 164 ppm, respectively. No significant P increases were observed but there did exist a significant increase of K in the topsoil for both clay and sandy turkey structures. The results show that swine hoop houses with less than three or four years of age may not pose a threat to groundwater pollution due to the leaching of nutrients. The only dairy feedlot sampled in this study, although it has been used for more than 20 years, did not show leaching of NO₃‐N and P. However, it did show a significantly elevated concentration of potassium in the topsoil, as compared to the background sample. More sites should be investigated to verify this.     

包头西6.4级地震震害及经济损失评估

介绍了１９９６年包头西６．４级地震震害并对地震经济损失作出了评估;根据包头市的震害评估经验,提出了大工业城市震害评估和工业设备、仪器仪表地震经济损失评定的基本原则和方法;此外,对大工业城市震害评估中有待解决的问题进行了探讨。     

降雨入渗对三峡库区堆积层滑坡稳定性的影响

基于三峡水库库水位调控方案和极端降雨情况,笔者利用有限元模拟库水位在175~145m波动和降雨时红石包滑坡Ⅲ的暂态渗流场,将计算得到的暂态孔隙水压力分布用于滑坡的极限平衡分析,并考虑基吸力对非饱和土抗剪强度的影响。探讨降雨强度对滑坡稳定性的影响,并考虑暴雨与库水位骤降共同作用下滑坡的稳定性。研究表明:滑坡稳定性的影响受控于滑坡土的入渗能力和滑坡结构形态;当暴雨强度为300mm/d时,红石包滑坡Ⅲ的临界降速1m/d。其成果将为库区滑坡治理提供科学依据。     

建筑抗浮设计水位取值方法——以北京市某工程为例

近年来,随着首都北京城市建设的高速发展,城市建设用地越来越少,地下空间的开发和利用成为发展的必然趋势。大量带有纯地下车库的高层建筑,以及地下管廊、下沉式广场的兴建,使抗浮问题非常突出。抗浮标准如何确定,抗浮水位如何取值,各类规范均没有明确规定,传统方法多依据经验确定抗浮水位取值,缺乏理论依据,不符合客观实际情况,使得抗浮设计存在安全隐患或增大了工程造价。笔者以北京市区某一工程为例,通过研究区域内浅层地下水的赋存与渗流特性,水位变化的历史过程和影响因素,通过渗流分析,从客观的角度提出建筑抗浮设计水位的取值方法,使得取值更具科学性和经济性。     

MODELING RUNOFF FROM VARIABLE SOURCE AREAS IN HUMID,SHALLOW WATER TABLE ENVIRONMENTS1

ABSTRACT: Variable Source Areas (VSAs) are zones with water saturated soils in forested wetlands fringing streams and creeks. Runoff from these areas is generated by saturation excess after a shallow water table rises and inundates the ground surface. In humid regions, like Florida and the Southeast, VSAs are believed to produce most of the runoff in shallow water table environments. Modeling the spatial extent and temporal fluctuation of a VSA is difficult because the formation of a VSA depends on a number of hydrological and morphological factors like rainfall intensity, soil texture, water table depth, and topographic attributes of the terrain. In this paper, we couple a digital elevation model with a two‐dimensional variable saturation model to illustrate the formation of a VSA at the hillside scale. The topography derived from the digital elevation model forms the upper domain geometry for the two‐dimensional finite element simulations of variable saturated flow. The objectives are: (1) to model the spatial and dynamic fluctuation of a VSA, and (2) to understand the roles of rainfall variability and terrain attributes on the formation of a VSA. Results show that hillsides with shallow water table depths, low saturated hydraulic conductivity, mild slopes, and concave slope curvature were more susceptible to runoff from a variable source. Runoff from a variable source showed little sensitivity to rainfall intensity. In general, landscapes with steep slopes generated a small VSA and a seepage face that vanished rapidly with time. In contrast, flat terrains are more amenable to VSA and retain ground surface inundation for longer periods of time.     

某电站溢洪道边坡运行期地下水渗流场特征数值模拟

西南某电站位于岷江上游河段,水库蓄水后库水位将抬升130余米,改变了边坡地下水原有渗流场特征及其排泄补给条件,使地下水位以下岩体的物理力学性质产生一定程度的变化,并将由此产生的孔隙水压力叠加于边坡上,库水位的升降也将引起动水压力的变化,所有这些必然对溢洪道边坡长期稳定性产生一定程度的影响,因此研究边坡运行期间地下水渗流场特征具有重要意义。文章在大量现场调查和室内分析的基础上,利用三维数值模拟技术,对溢洪道边坡在蓄水前、蓄水后以及库水位骤降后的地下水渗流场特征展开了详细的分析研究,取得了较为科学、合理、可信的研究成果。     

鄂尔多斯盆地东缘石油苗的成因探讨

最近在鄂尔多斯盆地东缘石露头（二马营组T(e2)）发现一油气苗，通过对油苗的微观分子组成和碳同位素地球化学特征分析，认为该油苗的地球化学性质与在鄂尔多斯盆地迄今所发现的原油或凝析油差别较大，推测其油源岩为下古生界的碳酸盐岩，这一发现对鄂尔多斯盆地东缘油气勘探可能具有重要的意义。     

MODELING PERCOLATION LOSSES FROM A PONDED FIELD UNDER VARIABLE WATER-TABLE CONDITIONS1

ABSTRACT: A numerical simulation model was developed to predict the vertical and lateral percolation losses from a ponded agricultural field. The two-dimensional steady-state unsaturated/ saturated flow equation was solved using the finite-difference technique. A constant ponding depth was maintained at the soil surface with different water table conditions in an application of the model for rice fields bordered by bunds. Field experiments were conducted for two different water table depths to collect data on the spatial distribution of volumetric soil-moisture content for model verification. The measured soil-moisture content values were found to be in close agreement with those predicted by the model. The sensitivity analysis of the model with selected hydrologic conditions shows that the model is most sensitive to the values of saturated hydraulic conductivity, but relatively less sensitive to water table depth, ponding depth, and evaporation rate from the soil surface. It implies that, in a ponded rice field condition, the lateral and vertical percolation losses are mostly governed by the hydraulic conductivity of the soil. The vertical percolation losses were almost equal to the saturated hydraulic conductivity values and, in most cases, these losses increased with deeper water table depths. The lateral percolation losses also increased with deeper water table depths; however, these losses were relatively small in comparison to the vertical percolation losses. The vertical and lateral percolation losses increased with the increase in ponding depths. The lateral percolation losses through the bund decreased when the evaporation losses increased from the soil surface. The results of this study indicate that the percolation losses from a ponded field may be predicted accurately for a wide range of soil and hydrological conditions when the values of hydraulic conductivity, evaporation rate, depth of ponding, and water table depth are accurately known.     

一种用于尾矿库干滩长度在线监测的新方法

通过分析当前常用干滩长度在线监测方法所适应的条件及其存在的问题,提出了一种可用于干滩长度在线监测的新方法——渗流反推法,其基本原理是通过在干滩面上依次布置一定数量的渗压计,以获取实时的浸润线,然后通过建立浸润线的库长-坝高坐标系,再结合库水位,通过解算浸润线与库水位方程组,计算出尾矿库的干滩长度。该方法具有适应性强,监测准确,费用低、操作与维护简单、抗雷电能力强等优点,为干滩长度在线监测新方法的探索提供了参考。