Theory of Seepage into an Auger Hole in a Confined Aquifer

A steady-state theory is presented for predicting flow into an auger hole partially penetrating a homogeneous and anisotropic confined aquifer that is underlain by an impermeable layer. The developed equations can be directly applied (i.e., without resorting to a coordinate transformation) to translate the rate of rise of the water in a pumped auger hole into directional conductivities of soil. The study shows that the conductivity values calculated by neglecting the confining pressure of an artesian aquifer (i.e., by applying the existing unconfined auger-hole seepage theories to experimental auger data obtained from a confined aquifer) may lead to serious error; hence, the confining head of an aquifer must be considered while the conductivity values are computed. Further, the distance of the outer layer also plays an important role in determining the flow to an auger hole penetrating a confined aquifer, and this parameter must therefore be included in the theoretical analysis of the problem. The validity of the proposed theory is checked by comparing a few results obtained from the theory with corresponding results obtained from numerical and analytical works. The developed theory is an addition to already existing auger-hole seepage theories for water-table aquifers; together with the available theories, the proposed solution is expected to cover the most commonly encountered auger hole experimental flow situations in the field.     

Theory of Fine Sediment Infiltration into Immobile Gravel Bed

A theoretical model is developed to describe the process of fine sediment infiltration into immobile coarse sediment deposits. The governing equations are derived from mass conservation and the assumption that the amount of fine sediment deposition per unit vertical travel distance into the deposit is either constant or increases with increasing fine sediment fraction. Model results demonstrate that fine sediment accumulation decreases rapidly with depth into coarse substrate initially void of fine sediment, which is consistent with experimental observations that significant fine sediment infiltration occurs to only a shallow depth. Comparisons of the theory with flume data indicate that the model adequately reproduced the weighted-averaged fine sediment fraction values from experiments. An early model developed by Sakthivadivel and Einstein for fine sediment infiltration is in part based on the generally incorrect assumption that intragravel flow remains constant following fine sediment infiltration. Applying a correction to the Sakthivadivel and Einstein model based on alternate hypothesis that introgravel flow is driven by a constant head gives similar results as the proposed model.     

承压开采技术在地下矿山废水减排中的应用

地下矿山的废水减排是针对地下矿山开采过程中造成的水环境严重破坏问题而提出的。承压开采是在尽量不影响矿井水文地质条件下所使用的带压开采技术,可以很好地解决资源开采对地下水原始赋存状态的破坏问题,从而取得良好的经济、社会和环境效益。论文以冀中能源股份有限公司葛泉矿东井1195回采工作面为例,系统总结了地下矿山承压开采的技术方法和途径,分析了承压开采在矿山废水减排中的意义和作用及取得的社会和经济效益。     

Characteristics of Submerged Jets in Evolving Scour Hole Downstream of an Apron

This paper reports an experimental investigation on the velocity and turbulence characteristics in an evolving scour hole downstream of an apron due to submerged jets issuing from a sluice opening detected by an acoustic Doppler velocimeter. Experiments were carried out for the conditions of submerged jets, having submergence factors from 0.96 to 1.85 and jet Froude numbers from 2.58 to 4.87, over sediment beds downstream of a rigid apron. The distributions of time-averaged velocity vectors, turbulence intensities, and Reynolds stress at different streamwise distances are plotted for the conditions of initial flat bed, intermediate scour holes, and equilibrium scour hole downstream of an apron. Vector plots of the flow field show that the rate of decay of the submerged jet velocity increases with an increase in scour hole dimension. The bed-shear stresses are determined from the Reynolds stress distributions. The flow characteristics in evolving scour holes are analyzed in the context of self-preservation, growth of the length scale, and decay of the velocity and turbulence characteristics scales. The most significant observation is that the flow in the scour holes (intermediate and equilibrium) is found to be plausibly self-preserving.     

Hydraulic Performance of Geosynthetic Clay Liners in a Landfill Final Cover

Percolation from a landfill final cover containing a geosynthetic clay liner (GCL) as the hydraulic barrier is described. The GCL was covered with 760?mm of vegetated silty sand and underlain with two gravel-filled lysimeters to monitor percolation from the base of the cover. Higher than anticipated percolation rates were recorded in both lysimeters within 4–15?months after installation of the GCL. The GCL was subsequently replaced with a GCL laminated with a polyethylene geofilm on one surface (a “composite” GCL). The composite GCL was installed in two ways, with the geofilm oriented upwards or downwards. Low percolation rates (2.6–4.1?mm/year) have been transmitted from the composite GCL for more than 5?years regardless of the orientation of the geofilm. Samples of the conventional GCL that were exhumed from the cover ultimately had hydraulic conductivities on the order of 5×10?5?cm/s. These high hydraulic conductivities apparently were caused by exchange of Ca and Mg for Na on the bentonite combined with dehydration. The overlying and underlying soils likely were the source of the Ca and Mg involved in the exchange. Column experiments and numerical modeling indicated that plant roots and hydraulic anomalies caused by the lysimeters were not responsible for the high hydraulic conductivity of the GCL. Despite reports by others, the findings of this study indicate that a surface layer 760?mm thick is unlikely to protect conventional GCLs from damage caused by cation exchange and dehydration. Accordingly, GCLs should be used in final covers with caution unless if cation exchange and dehydration can be prevented or another barrier layer is present (geomembrane or geofilm).     

Lateral Loading of a Rigid Rock Socket Embedded in a Damage-Susceptible Poroelastic Solid

The paper presents a computational assessment of the influence of damage on the behavior of a rigid rock socket embedded in a fluid-saturated poroelastic solid. The iterative computational scheme takes into consideration the irreversible alteration in the fluid transport characteristics that takes place as a result of damage and the stress dependency of the isotropic damage process. Numerical results illustrate the influence of the stress-state-dependent damage process on transient consolidation response of the rock socket head displacement.     

施工方案技术改进在某金矿深孔爆破成井中的应用

深孔爆破施工方法是切割天井快速成井的有效途径,但钻孔偏差是制约深孔爆破成井成功的重要因素。通过对山东某金矿680中段一采场切割天井钻孔偏差及其现场存在的问题进行分析,在原设计方案的基础上对施工方案进行改进。首先提出以炮孔补偿系数、破碎角和自由面系数这3个参数确定补孔位置及炮孔起爆顺序,解决了钻孔偏差问题;其次采用分次爆破和不同爆炸猛度的炸药解决了装药困难及雷管段别不足的问题。第一次爆破采用卷状乳化炸药进行人工装药,炸药猛度高,但装药效率低;第二次爆破采用特制的改性粒状铵油炸药进行机械装药,极大地提高了装药效率,而且爆破产生的有毒有害气体较少。最终作业现场取得良好的爆破效果,证实改进的施工技术方案切实可行,对类似工程具有一定的指导价值。     

Water Table Fluctuation in the Presence of a Time-Varying Exponential Recharge and Depth-Dependent ET in a Two-Dimensional Aquifer System with an Inclined Base

An analytical solution is presented for water table fluctuation between ditch drains in presence of exponential recharge and depth-dependent evapotranspiration (ET) from groundwater table in a two-dimensional gently sloping aquifer. The groundwater head above the drain is small compared to the saturated thickness of the aquifer. A sound mathematical transformation is devised to transform the two-dimensional groundwater flow equation into a simple form, which makes possible to obtain an analytical solution. The transient midpoint water table variations from the proposed solution compare well with the already existing solutions for horizontal aquifer. A numerical example is used to illustrate the combined effect of depth-dependent ET coupled with a time-varying exponential recharge on the water table fluctuation. The inclusion of a depth-dependent ET in the solution results in water table decline at a faster rate as compared to the case when ET is not considered. With an increase in slope of the aquifer base, water table profiles become asymmetric and the water table divide shifts towards the lower drain. The height of the water table profiles increases on moving away from the boundary of the aquifer and the highest level of the ground water table is obtained in the central portion of the aquifer basin due to the presence of drainage ditches on the aquifer boundary. When the effect of ET is incorporated in combination with recharge, the analytical solution results in accurate and reliable estimates of water table fluctuations under situations subjected to a number of controlling factors. This study will be useful for alleviation of drainage problems of the aquifers receiving surface recharge and surrounded by streams.     

Hydrodynamic Modeling and Mathematical Simulation of Flow Field and Temperature Profile for Molten Stainless Steel in an Asymmetrical T‐Type Single‐Strand Continuous Casting Tundish with Arch or Round Hole(s) at Dam Bottom

In order to obtain the optimal structural parameters of the dug arch or round hole(s) at dam bottom in an 18–20 tons asymmetrical T‐type single‐strand continuous casting tundish, the flow field profiles and temperature profiles of molten stainless steel in the tundish with arch or round hole(s) at dam bottom have been investigated using hydrodynamic modeling coupled with mathematical simulation. The optimal structural parameters of arch hole(s) at dam bottom can be obtained from hydrodynamic modeling as that two arch holes with 30 mm as height and 50 mm as radius are symmetrically dug at dam bottom with the distance between arch hole center and dam center as 205 mm; or the optimal structural parameters of round hole(s) can be recommended as that one round hole with 70 mm as diameter is dug at left of the dam bottom with the distance between hole center and dam center as 205 mm. The results of mathematical simulation suggest that digging arch or round hole(s) at dam bottom with above‐mentioned structural parameters cannot obviously induce negative effects on streamlines and velocity vector profiles of molten stainless steel in the tundish by short circuit flow via arch or round hole(s) at dam bottom. The calculated temperature drop of molten stainless steel between the submerged ladle shroud and submerged entry nozzle in the tundish with arch or round hole(s) at dam bottom is about 3.0 K, the maximum temperature drop of molten stainless steel in the tundish is about 6.0 K.     

Does the Theory of Planned Behavior Mediate the Effects of an Oncologist's Recommendation to Exercise in Newly Diagnosed Breast Cancer Survivors? Results From a Randomized Controlled Trial.

This randomized trial examined the effects of 2 oncologist-based exercise interventions--recommendation only (RO) and recommendation plus referral (RR)--versus usual care (UC) on social-cognitive constructs from the theory of planned behavior (TPB). The authors also examined whether the TPB mediated the significant effect of the RO intervention on exercise and explained the null effect of the RR intervention. Independent t tests revealed that both interventions had significant effects on TPB constructs; however, only the RO intervention impacted perceived behavioral control (PBC). Path analyses indicated that PBC was the only construct with a direct effect on exercise and that it mediated the effect of the RO intervention on exercise and explained the null effect of the RR intervention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)