Beneficial Reuse of FGD Material in the Construction of Low Permeability Liners: Impacts on Inorganic Water Quality Constituents

In this paper, we examine the water quality impacts associated with the reuse of fixated flue gas desulfurization (FGD) material as a low permeability liner for agricultural applications. A 0.457-m-thick layer of fixated FGD material from a coal-fired power plant was utilized to create a 708?m2 swine manure pond at the Ohio Agricultural Research and Development Center Western Branch in South Charleston, Ohio. To assess the effects of the fixated FGD material liner, water quality samples were collected over a period of 5?years from the pond surface water and a sump collection system beneath the liner. Water samples collected from the sump and pond surface water met all Ohio nontoxic criteria, and in fact, generally met all national primary and secondary drinking water standards. Furthermore it was found that hazardous constituents (i.e., As, B, Cr, Cu, and Zn) and agricultural pollutants (i.e., phosphate and ammonia) were effectively retained by the FGD liner system. The retention of As, B, Cr, Cu, Zn, and ammonia was likely due to sorption to mineral components of the FGD liner, while Ca, Fe, and P retention were a result of both sorption and precipitation of Fe- and Ca-containing phosphate solids.     

Factors Affecting Long-Term Efficiency of Compensation Grouting in Clays

Compensation grouting has been attracting attention in recent years to control ground settlement caused by underground construction. A successful and effective application of compensation grouting depends not only on the use of a good monitoring system in the field but also on a fundamental understanding of grout behavior in soils. For compensation grouting in clay, there is a need to consider the long-term effectiveness of compensation grouting. Grout injection tests were conducted in the laboratory to examine soil fracturing patterns and consolidation effects in relation to compensation grouting. Both compaction and hydrofracturing modes of grouting were tested on kaolin clay specimens with different overconsolidation ratios. Finite-element analysis was also conducted to simulate the balloon expansion tests (ideal compaction grouting tests) and the results were compared with the data from the laboratory tests. Based on the research findings, new design criteria are proposed to improve the long-term efficiency of compensation grouting for clays.     

Use of Waste Materials for Control of Acid Mine Drainage and Subsidence

This paper presents the results of a study of the use of fluidized-bed combustion ash in an underground coal mine for control of acid mine drainage and subsidence. Fluidized-bed combustion ash (FBC ash) is a waste by-product of advanced coal combustion. Presently, most of the FBC ash produced in power generation is disposed in landfills. Subsidence and acid mine drainage are two major problems found in coal mining areas. The problems of disposal of FBC ash, mine subsidence, and acid mine drainage can be reduced by placing the ash in abandoned coal mines. The study included laboratory experiments, computer modeling, and a field application of FBC ash in an abandoned underground mine. Potential subsidence values under different backfill configurations were computed by using the finite element method. Strength requirements for the grout were determined on the basis of site-specific geologic information and a stress analysis. The FBC ash was placed in a mine cavity by pumping it in the form of a grout to explore the viability of hydraulic backfilling. Field observations were made on the field strength and flow characteristics of the FBC ash grout. The paper contains information on strength requirements of the grout, flow characteristics of the grout, expected reductions in potential subsidence, and acid mine drainage around the grouted mine. The results show that a grout made of fluidized-bed combustion ash can be successfully placed in a mine cavity by hydraulic backfilling in order to reduce the problems caused by subsidence and acid mine drainage.     

浅析金属矿山主井涌水治理方法

地下水是产生井筒涌水的主要水源,研究表明矿区地下水资源丰富,主要源自大气降水,而矿区断裂普遍发育,构成了涌水通道,为主井涌水提供了条件.通过对比分析,并结合矿区井筒地质概况,选择静水抛渣注浆封水、壁后注浆充填截水作为井筒涌水的治理方案,在此基础上,介绍了涌水治理的施工工艺、主要技术参数及排水问题.在井筒涌水淹井后,采用...     

Lessons Learned from Field and Laboratory Testing of a DBR Project

Where faulting takes place due to the absence of dowel bars and inadequate subbase support in jointed concrete pavement (JCP), dowel bar retrofit (DBR) is used to improve load transfer efficiency (LTE) and to prevent further faulting of slabs at transverse joints. Even though DBR generally improves LTEs and overall performance of JCPs, not all DBR projects have been successful. Faulting reoccurred within 2?years after DBR treatment on US59 in Texas. An investigation from the cores taken in the project revealed excessive voids under a dowel bar due to poor consolidation of the grouting material. A laboratory investigation was performed to determine the most critical factors for adequate consolidation of grouting materials in DBR. Typical rapid-setting grout materials widely used in DBR were selected and full-scale specimens were made for evaluations. Four testing variables for consolidation performance were investigated: time of placement after mixing, vibration time, slot width, and maximum aggregate size. Maximum aggregate size and slot width were not critical factors for consolidation performance of grout. The most significant factor was vibration time. Twenty s of vibration is recommended. Placement time was also an important factor, with grout materials placed after initial set performing poorly. Delayed placement of grout materials without vibration led to the most voids under the dowel bars.     

高压注浆技术与预应力锚杆的应用

高压注浆技术与预应力锚杆是矿山特殊岩土工程加固的两种主要技术手段，文中通过对高压注浆浆液扩散过程及注浆结石体强度增长机理分析研究，认识到该技术能从根本上改良土体和岩石的物理化学性质，从而 在浇注范围内产生一种新的介质；同时，文章对某工程加因过程中现场试验及观测结果进行了分析，表明高压注浆技术能达到显著提高预应力锚杆承载能力的目的。     

Long-term environmental impact of tailings deposits

This paper, within the MiMi project, explains the models and the modelling used in the performance assessment (long-term) calculations for the remediation of sulphidic mine tailings. The long-term impact of tailing deposits on the environment is addressed for two types of cover: soil and water covers. Oxygen intrusion is the process that determines the sulphide oxidation and the generation of acid mine drainage containing toxic metals. The primary acidity generated in the tailings from the sulphide oxidation is to a large extent neutralised by the buffering minerals in the deposit. However, when the water leaves the deposit, more acidity is generated due to the oxidation of mainly the ferrous iron (latent acidity). For soil covers, the generated acidity and dissolved metals flow downward with the infiltrating water. However, in a water cover, the reaction products formed may diffuse upwards into the water covering the deposit. Therefore, the acidity is not neutralised in the interior of the deposit. The behaviour of metals/metalloids such as Cu, Pb, Cd and As are also studied. They may be sorbed on the mineral surfaces of the minerals and retained in the deposit for a long time. Some of them may dissolve the more soluble sulphides (e.g., pyrrhotite) and precipitates as secondary sulphides. The data were selected based on experience from primarily Kristineberg (northern Sweden) but also from other sites.     

江西崇义茅坪钨钼矿矿井突水灾害隐患分析及防治措施

通过对江西崇义茅坪钨钼矿水文地质条件和井巷疏排地下水现状的调查分析,根据矿区不同地段的矿坑充水条件,对地下水产生矿井突水的可能性进行了初步的分区评价,并为矿区地下水隐患的防治工作提出了一些措施建议。     

Applying MODFLOW Model for Drainage Problem Solution: A Case Study from Jahir Irrigated Fields, Israel

High water table and soil salinization processes are common in irrigated fields in Israel. Subsurface drainage systems are a common technique to solve soil salinity problems. Subsurface drainage models can contribute to the efficiency of the drainage system as it can assist in the selection of the proper drainage system and its proper placement in the field. In this study we used the MODFLOW groundwater flow model to simulate groundwater levels in Jahir irrigated fields, the Jordan Valley, Israel. Using a three-layer groundwater flow model, the most efficient drainage system was found to be a combination of deep drains with relief wells and a pump placed in the area with soil salinity problem and upward hydraulic pressure. It was found that simulated drainage system can yield nearly 200,000?m3 of water per year. Given certain information, a spatially distributed groundwater flow model such as MODFLOW can provide more reliable information than different analytical solutions for planning of an effective subsurface drainage system.     

Experimental Investigation of Grouted Helical Piers for Use in Foundation Rehabilitation

Building rehabilitation is critical for numerous older urban areas, many of which have inadequate foundations to support new demands. Consequently, development of practical methods to strengthen existing foundations is crucial. In engineering practice, both subsurface grouting and helical piers have been widely used to address these issues by strengthening the foundation. If the solid shaft of a typical helical pier is replaced by a hollow shaft, then helical piers provide the ability to deliver grout. It is hypothesized that these grouted helical pier systems could address foundation strengthening needs. This paper presents findings from an exploratory research program where grouting and pier placement tools were developed and tested on the large geotechnical centrifuge at the University of California, Davis. Experimental methods and procedures developed are presented, and observations regarding the formation of grout bulbs under different conditions are analyzed. Physical observation of the test specimens indicates that average grout bulb diameters of 0.6–1.9 times the helix diameter (Dh) are attainable. For similar grout mixes, 20–50% larger grout bulbs can be attained by adding just a modest amount of injection pressure. Future research may use these results to develop load performance data.     

Model of Compaction Grouting

Compaction grouting is an important soil improvement and underpinning technique that involves injection of a very stiff grout material into the soil. The objective is to displace and compact the surrounding soil without permeating or hydrofracturing it. Compaction grouting has been developed and used almost entirely on the basis of practical experience. The present study proposes a theoretical model that describes the mechanics of the compaction grouting process and rationally considers the different soil and grouting parameters that govern the overall design and performance of the method. The theoretical basis of the model draws from the theory of cavity expansion as well as the conical shear failure above the grout bulb. This model was validated using limited available data. The results indicate reasonable agreement and show a good potential of the proposed model for rationally optimizing the design of compaction grouting operations.     

辽宁省岫岩某金矿水文地质条件分析

通过对辽宁省岫岩县某金矿水文地质概况分析,地下水类型分析、补径排条件分析、矿坑涌水量、矿区供水水源等条件进行分析,评价矿区水文地质条件。分析矿区开采风险程度。     

化学注浆技术在三山岛金矿的研究与应用

三山岛金矿直属矿区属海底及滨海地下开采矿山,为基岩裂隙充水矿床,水文地质条件复杂。矿区巷道涌水量大,有腐蚀性,且作业环境温度高、湿度大。近年来,通过开展化学注浆设备选型和注浆施工技术试验研究,采用ZBQS气动双液注浆泵,灌注HK9101材料等措施,成功治理高温、高湿、高卤和大流量的巷道涌水,取得了较好的经济效益,对深部巷道开拓涌水治理具有一定的研究和推广价值。     

Porous Reactive Walls for the Prevention of Acid Mine Drainage: A Review

Abstract

Laboratory tests and field-scale demonstrations indicate that permeable reactive walls, designed to induce bacterially mediated sulfate reduction within aquifers, have the potential to prevent the discharge of acidic, metal-rich waters. Laboratory batch studies were conducted to determine optimal mixtures of organic materials. Column studies were conducted to evaluate the potential for sulfate reduction and metal sulfide precipitation under dynamic flow conditions at groundwater velocities similar to those observed in the field. These laboratory studies established that sulfate reduction and metal sulfide precipitation mechanisms result in decreases in the concentrations of sulfate and iron and other metals. In the column experiments, sulfate and Fe were removed from synthetic mine drainage water at rates of 500-800 mmol/day/m³. In a pilot-scale field study, test cells installed into an aquifer containing a plume of mine waste-impacted groundwater, induced sulfate reduction and metal-sulfide precipitation. Within a flow path of less than one metre sulfate reduction and metal sulfide precipitation reactions resulted in the removal of iron, and production of alkalinity to the extent that the acid generating potential of the plume water was removed. A full-scale porous reactive wall was installed at the same site in August 1995. Comparing water entering the wall to treated water exiting the wall; sulfate concentrations decrease from 2,400-4,500 mg/L to 200-3,600 mg/L and Fe concentrations decrease from 250- 1,300 mg/L to 1.0 - 40 mg/L. After passing through the reactive wall, groundwater is transformed from acid producing to acid consuming.     

大红山铜矿485水仓排水系统自动控制技术研究

485水仓是大红山铜矿井下排水系统的重要组成部分,该水仓汇聚了地下水、生产用水以及巷道清用水,水量较大、水质较差、颗粒物较多。文章分析了大红山铜矿485水仓排水系统的现状和面临的问题,提出采用远程自动控制技术的解决思路。在此基础上,对该水仓的自动控制方案与设备选择进行了系统的研究和开发。系统运行效果表明：采用自动控制技术和设备进行485水仓的监督与管理,可以大大减少值班工人数量,降低工人劳动强度,同时通过错峰运行,节省大量能耗。     

Transplacental cocaine exposure. 1: A rodent model

Contaminated groundwater poses a significant health hazard and may also impact wildlife such as amphibians when it surfaces. Using FETAX (Frog Embryo Teratogenesis Assay-Xenopus), the developmental toxicity of ground and surface water samples near a closed municipal landfill at Norman, OK, were evaluated. The groundwater samples were taken from a network of wells in a shallow, unconfined aquifer downgradient from the landfill. Surface water samples were obtained from a pond and small stream adjacent to the landfill. Surface water samples from a reference site in similar habitat were also analyzed. Groundwater samples were highly toxic in the area near the landfill, indicating a plume of toxicants. Surface water samples from the landfill site demonstrated elevated developmental toxicity. This toxicity was temporally variable and was significantly correlated with weather conditions during the 3 days prior to sampling. Mortality was negatively correlated with cumulative rain and relative humidity. Mortality was positively correlated with solar radiation and net radiation. No significant correlations were observed between mortality and weather parameters for days 4-7 preceding sampling.     

Monthly Water Resources and Irrigation Planning: Case Study of Conjunctive Use of Surface and Groundwater Resources

The Tehran metropolitan area is one of the mega cities of the world and has an annual domestic water consumption close to one billion cubic meters. The sewer system mainly consists of traditional absorption wells. Therefore, the return flow from the domestic consumption has been one of the main sources of groundwater recharge. Some part of this sewage is drained into local rivers and drainage channels and partially contaminates the surface runoff and local flows. These polluted surface waters are used in conjunction with groundwater for irrigation purposes in the southern part of the Tehran. In this paper, a systematic approach to surface and groundwater resources modeling in the study area, with its complex system of water supply, groundwater recharge, and discharge, is discussed. A dynamic programming optimization model is developed for conjunctive use planning. The objective function of this model is developed to supply the agricultural water demands, to reduce pumping costs, and to control groundwater table fluctuations. To develop the response function of the aquifers located in the study area, a mathematical model for simulation of the Tehran aquifer water table fluctuations has been developed and calibrated with the available data. Different scenarios are defined to study the long-term impacts of the development projects on conjunctive use policies and water table fluctuations. Comparison of the results showed how significant is the effects of an integrated approach to the surface and groundwater resources allocation in Tehran metropolitan area. The proposed model is a useful tool for irrigation planning in this region.     

Monitoring and Modeling Grout Efficiency of Lifting Structure in Soft Clay

An inclined eight-story reinforced concrete building on a thick soft clay deposit was leveled by compensation grouting with short gel time grout injected through sleeved pipes. The monitoring system is used to record the injected grout volume, the mat foundation’s heaved volume after grouting, and the mat foundation’s settled volume during pore pressure dissipation. The grouting efficiencies improved from negative value to less than one, and the stress histories of clay soils changed from normally consolidated to overconsolidated states. A final compensation efficiency of 9.78% was achieved and the building was successfully leveled. A series of numerical simulations were conducted to assess the capability of compensation grouting modeling. The numerical simulation results indicate that the consolidation behavior and the stress history of clayey foundation soils can be modeled reasonably well. However, the computed final grout efficiency is larger than that from the monitoring data because the simulation of fracture grouting by volumetric strain input is more like compaction grouting mode rather than fracture grouting mode, and this induces lesser excess pore pressure, lesser settlement and higher grout efficiency. These findings are also confirmed from other researchers’ laboratory and field testing results.     

Integrated Water Management for the 21st Century: Problems and Solutions

Most of the projected global population increases will take place in third world countries that already suffer from water, food, and health problems. Increasingly, the various water uses (municipal, industrial, and agricultural) must be coordinated with, and integrated into, the overall water management of the region. Sustainability, public health, environmental protection, and economics are key factors. More storage of water behind dams and especially in aquifers via artificial recharge is necessary to save water in times of water surplus for use in times of water shortage. Municipal wastewater can be an important water resource but its use must be carefully planned and regulated to prevent adverse health effects and, in the case of irrigation, undue contamination of groundwater. While almost all liquid fresh water of the planet occurs underground as groundwater, its long-term suitability as a source of water is threatened by nonpoint source pollution from agriculture and other sources and by aquifer depletion due to groundwater withdrawals in excess of groundwater recharge. In irrigated areas, groundwater levels may have to be controlled with drainage or pumped well systems to prevent waterlogging and salinization of soil. Salty drainage waters must then be handled in an ecologically responsible way. Water short countries can save water by importing most of their food and electric power from other countries with more water, so that in essence they also get the water that was necessary to produce these commodities and, hence, is virtually embedded in the commodities. This “virtual” water tends to be a lot cheaper for the receiving country than developing its own water resources. Local water can then be used for purposes with higher social, ecological, or economic returns or saved for the future. Climate changes in response to global warming caused by carbon dioxide emission are difficult to predict in space and time. Resulting uncertainties require flexible and integrated water management to handle water surpluses, water shortages, and weather extremes. Long-term storage behind dams and in aquifers may be required. Rising sea levels will present problems in coastal areas.     

Physical Model Testing of Compaction Grouting in Cohesionless Soil

Preliminary results of small-scale model compaction grouting tests performed in a geotechnical centrifuge are presented. The soil response to a one-stage grout bulb injection in dry uniform sand was examined at various prototype depths, and the effects of grout composition on grout bulb development and shape and on soil response are evaluated. Preliminary results indicate that the shape of the injected grout bulb is a function of overburden pressure. For specific grouting conditions, there is a maximum size that the grout bulb will achieve. Observed soil deformations were similar to those observed in models of deep uplift anchors. The addition of either clay or flyash to the grout mix reduced the ability to sustain high injection pressures.