污水渗滤土地处理系统中的复氧方式及效果   总被引：24，自引：0，他引：24  

何江涛  张达政  陈鸿汉  汤鸣皋 《水文地质工程地质》2003,30(1):103-106,109

复氧是困扰人工快渗、构造湿地等污水渗滤土地处理系统已久的问题。国际上目前采用的方法主要有3种：一是采用干湿交替的工作方式进行系统复氧，一是设置通气管对系统内部进行复氧，再一是利用植物的根系对系统内部进行复氧。研究结果表明，干湿交替的工作方式对系统的复氧条件有明显改善，而小水力负荷周期的工作方式对系统的复氧更为有效。通气管的设置通常与间歇性布水工作方式相结合，其效果通常要明显好于单纯采用干湿交替的工作方式。植物根系对系统的复氧，常因植物不同类型面具有不同的氧传输能力，植物根茎所能到达的范围往往决定了系统有效处理部位的大小。  相似文献   

Hydrological connectivity of soil pipes determined by ground‐penetrating radar tracer detection     

Joseph Holden 《地球表面变化过程与地形》2004,29(4):437-442

Soil pipes are common and important features of many catchments, particularly in semi‐arid and humid areas, and can contribute a large proportion of runoff to river systems. They may also signi?cantly in?uence catchment sediment and solute yield. However, there are often problems in ?nding and de?ning soil pipe networks which are located deep below the surface. Ground‐penetrating radar (GPR) has been used for non‐destructive identi?cation and mapping of soil pipes in blanket peat catchments. While GPR can identify subsurface cavities, it cannot alone determine hydrological connectivity between one cavity and another. This paper presents results from an experiment to test the ability of GPR to establish hydrological connectivity between pipes through use of a tracer solution. Sodium chloride was injected into pipe cavities previously detected by the radar. The GPR was placed downslope of the injection points and positioned on the ground directly above detected soil pipes. The resultant radargrams showed signi?cant changes in re?ectance from some cavities and no change from others. Pipe waters were sampled in order to check the radar results. Changes in electrical conductivity of the pipe water could be detected by the GPR, without data post‐processing, when background levels were increased by more than approximately twofold. It was thus possible to rapidly determine hydrological connectivity of soil pipes within dense pipe networks across hillslopes without ground disturbance. It was also possible to remotely measure travel times through pipe systems; the passing of the salt wave below the GPR produced an easily detectable signal on the radargram which required no post‐processing. The technique should allow remote sensing of water sources and sinks for soil pipes below the surface. The improved understanding of ?owpath connectivity will be important for understanding water delivery, solutional and particulate denudation, and hydrological and geomorphological model development. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

A coupled discrete element model for the simulation of soil and water flow through an orifice          下载免费PDF全文

Yao Tang  Dave H. Chan  David Z. Zhu 《国际地质力学数值与分析法杂志》2017,41(14):1477-1493

Soil erosion around defective underground pipes can cause ground collapses and sinkholes in urban areas. Most of these soil erosion events are caused by fluidization of the surrounding soil with subsequent washing into defective sewer pipes. In this study, this soil erosion process is simplified as the gradual washout of sand particles mixed with water through an orifice. The discrete element method is used to simulate the large deformation behavior of the sand particles, and the Darcy fluid model is coupled with this approach to simulate fluid flow through porous sand media. A coupled 3D discrete element model is developed and implemented based on this scheme. To simulate previous experiments using this coupled model considering the current computing capacity, we incorporated a ‘supply layer’ to study the continuous erosion process. The coupled model can predict the erosion flow rates of sand and water and the shape of erosion void. Thus, the model can be used as an effective and efficient tool to investigate the soil erosion process around defective pipes. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

基于网络流理论的输油管道的最大输送问题研究     

张延飞  姜俊坡 《华东地质学院学报》2007,30(4):392-395

在天然气管道网络系统的工艺设计方案中,对布站的站点选择主要取决于其运营成本的相互比较,但鉴于需求和供应之间的关系,还必须考虑管道的输送能力和站点的容量等问题。对于这样复杂化的问题,利用网络流理论的最大流问题和最小费用的最大流问题,建立了输油管道最大输送问题的网络优化模型,并通过实例说明其有效性和可靠性。为输油管道网系统的构建提供了一种新的优化方法,在天然气管道输送决策管理中具有一定的理论参考价值和现实意义。  相似文献   

Significance of geomorphological and subsurface drainage controls on failures of peat‐covered hillslopes triggered by extreme rainfall     

Alan P. Dykes  Jeff Warburton 《地球表面变化过程与地形》2007,32(12):1841-1862

On 19 September 2003, 40 landslides of 140–18 000 m³ volume occurred within 2·5 km² on the slopes of Dooncarton Mountain (Republic of Ireland) during a storm that may have exceeded 90 mm within 90 minutes. The landslides were investigated to determine the reasons for such a high density of slope failures. All of the landslides were surveyed within four months, and nine of them were investigated in detail. The six largest landslides, all peat failures, accounted for 57% of the more than 100 000 m³ of material displaced during the event. A consistent sequence of superficial materials was found on the failed hillslopes, including an extensive iron pan at the base of a buried soil horizon 0·3 m below the base of the peat. Morphologically, almost all of the landslides occurred on steep planar slopes or around sharp convexities, with the latter failures developing retrogressively upslope. The only significant relationship found from analysis of 371 subsurface pipes and 142 seepage cracks (defined here as contiguous fissures conducting concentrated subsurface flow) across all the failures was that the thinner the peat cover, the deeper the pipes and seepage cracks occurred below the base of peat. It is concluded that most of the landslides were probably caused by a combination of excess water pressures in the buried soil horizon and the thinner overburden of peat or peaty soil associated with the steeper slope segments. Pipes and seepage cracks formed on the iron pan probably existed prior to the failure event and may have contributed to the high water pressures as rainwater inputs exceeded their discharge capacities. One large peat slide was probably triggered by excess water pressures developed within and between artificial tine cuts. The properties of the blanket peat were generally of little consequence in the occurrence of the landslides, but relict desiccation cracks and other structural weaknesses through the peat mass were probably highly significant. Although several aspects of the peat failures correspond to previously published examples, the context of these failures in terms of the topography and upland catena is distinctive. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

On the external pressure capacity of deepwater sandwich pipes with inter-layer adhesion conditions     

《Applied Ocean Research》2015

Sandwich pipes (SP), a composite structure consisting of two concentric steel tubes and a polymeric or cement-based core has been proposed to be well-insulated and withstand high installation and operational loads in deepwater oil and gas field. In the paper, the post-buckling responses and pressure capacity of sandwich pipes filled with the solid polypropylene annular were investigated. The degree of the inter-layer adhesion condition between the core layer and the surrounding pipes was modeled by the contact surfaces adopting different maximum shear strength values to allow the relative displacement between the layers. The effects such as inter-layer adhesion interactions, thickness-to-radius ratios, the core thickness, the material parameters, the relative initial ovality directions and the inelastic anisotropy on the collapse pressure of SPs were discussed. More than 2000 finite element (FE) models of the sandwich pipes with practical configurations were constructed and analyzed using the programming language Python within the FE software package ABAQUS. Based on the FE results, a simplified equation was developed and recommended for the collapse pressure calculation of sandwich pipes with the polypropylene annular.  相似文献   

单机械手夹持状态下钻杆运移平稳性分析          下载免费PDF全文

李昊轩  王清岩  金赠伍  李苓豪  郭乃铭 《探矿工程》2022,49(3):76-82

本文主要针对一种新型的可以保留钻杆旋转自由度的机械手,研究其运移钻杆时的稳定性和安全性是否满足要求。该机械手通过蓄能器提高了停泵保压效果,通过滚轮结构保留了钻杆的旋转自由度。本文建立了机械手的多体动力学模型及配套的液压控制回路,并进行机-液联合仿真分析。在分别改变钻杆直径和液压回路压力的条件下,观察机械手夹紧效果。通过仿真得到了钻杆的夹紧力变化曲线及钻杆重心位置变化曲线,确定了液压系统的许用压力范围,并验证了单机械手夹持状态下钻杆运移平稳性满足要求。  相似文献   

New data of typomorphic features of diamonds from placers in North Timan     

G. K. Khachatryan  M. B. Kopchikov  V. K. Garanin  M. V. Chukichev  N. N. Golovin 《Moscow University Geology Bulletin》2009,64(2):102-110

The morphological and spectral-optical properties of diamond crystals from placers in North Timan rivers have been studied with IR-spectroscopy and cathode luminescence methods. As a result, correlation between external characteristics of diamonds (size and degree of mechanical damage) and number of optically active centers has been revealed. The habit and the type of distribution of structural defects in diamond crystals studied are comparable with those in diamonds from the Archangelsk Region and North Timan’s placers. Based on the obtained data, origin issues and possible primary sources of diamonds from North Timan’s placers are discussed.  相似文献   

Nonlinear dynamics of a fluid-conveying pipe under the combined action of cross-flow and top-end excitations     

《Applied Ocean Research》2017

We report a theoretical investigation of an elastic and slender fluid-conveying pipe with a top-end excitation subjected to uniform cross flows. Considering the mean drag force and the time varying vortex-induced lift force which is modeled using a nonlinear van der Pol oscillator, the nonlinear partial differential equations of the motion of coupled fluid-structure system are constructed and simplified to a reduced-order model through the Galerkin-type discretization. By virtue of quasi-static displacement conditions, the characteristics of vortex-induced vibration of the pipe are evaluated for the first two lock-in modes. The results show that the top-end excitation can increase the vibration amplitude of the pipe when the cross-flow speed is out of the lock-in regions. When the cross-flow speed is within the lock-in region, however, the top-end oscillation causes a transition between quasi-periodic and periodic in the responses of the pipe, significantly reducing or increasing the vibration amplitudes depending on the excitation acceleration and frequency. This finding has an important guidance in suppressing vortex-induced vibrations by balancing the internal fluid velocity and the top-end excitation.  相似文献   

水热型融雪路面金属导热管合理埋设间距研究     

李侠 《冰川冻土》2015,37(4):1023-1027

为了研究水热型融雪化冰路面结构中金属导热管合理布设间距, 建立了基于传热学理论的路面融雪化冰有限元分析模型, 对不同外界气温、 不同埋设间距工况下金属热管融雪化冰能力进行计算分析. 结果表明: 外界气温在0~-10 ℃之间时, 热管融雪效果明显. 气温低于-10 ℃时, 热管尽量埋设至路面中部; 热管最优间距为100~200 mm, 当热管间距>200 mm时, 即使管内水温高达40 ℃, 0 ℃ 等温线将不再连续.  相似文献