采空区稳定性评价及处治对策

根据煤层开采后影响上覆岩层及地表而产生移动和变形的时间的变化关系定性分析采空区稳定性,而且采用FLAC3D模拟了在施加地面建筑载荷后地表变形情况,确定了采空区需要处理的范围;依据建筑物荷载集度及其重要程度,采用了不同注浆处治对策.通过对采空区上覆岩体的沉降和建筑物沉降监测数据的统计分析,评估了处治效果.     

The effects of brine disposal on a subtidal meiofauna community

Desalination plants generate notable (>1,000 s m³) quantities of hypersaline brine which potentially affect the biological communities in the receiving area. We assessed whether proximity to a brine discharge point located off Gran Canaria (Canary Islands, eastern Atlantic) altered patterns in the abundance and assemblage structure of subtidal, soft-bottom, meiofauna. Samples were collected twice (May 2008 and January 2009) at 0, 15 and 30 m away from the brine discharge point, corresponding to a change in salinity from 45 to 36. Proximity to the brine discharge point affected overall meiofaunal abundances: lowest abundances were observed at 0 m (64.55 ± 39.86 ind 10 cm⁻², mean ± SD) than at 15 (210.49 ± 121.01 ind 10 cm⁻²) and 30 m (361.88 ± 102.64 ind 10 cm⁻²) away from the brine discharge point. This pattern was particularly notable for the most conspicuous meiofaunal groups: nematodes and copepods, and meiofaunal assemblage structure also differed with varying proximity to the brine discharge point. Although multivariate techniques identified changes in salinity as a relevant driver of patterns in meiofaunal assemblage structure with varying proximity to the brine outfall, a shift in particle size composition between May 2008 and January 2009 also contributed to explain differences in meiofaunal abundances and assemblage structure with varying proximity to the brine discharge point. Hence, meiofauna can be considered a suitable tool to monitor environmental impacts derived from the discharge of hypersaline effluents on subtidal, soft-bottom, assemblages if potential confounding drivers, i.e. here temporal changes in particle size composition, are accounted for to avoid possible confusing interpretations.     

Resource management and agriculture in the periurban interface of Kumasi,Ghana: Problems and prospects

This paper outlines pressures on agricultural land in periurban Kumasi, Ghana. A survey of agricultural practices underlines the recent and rapid transition from agricultural to urban land use in the periurban interface, and shows how farmers are reacting by reducing fallow periods. Farmers are also intensifying agriculture near streams and rivers through increased use of irrigation, in response to growing urban markets for a wider range of vegetables. We identify specific problems of water resource pollution and waste management, with particular reference to farmland irrigation. We report results of composting interventions as a community‐based waste management strategy. We consider integrated organic waste recycling as a generic strategy to help protect periurban natural resources, to enhance food production through nutrient recycling, and to improve community sanitation.     

Application of numerical modelling in the design of a full‐scale heated Tunnel Sealing Experiment

The Tunnel Sealing Experiment (TSX) was a full‐scale in situ demonstration of technology for constructing nearly water tight‐seals in excavations through crystalline rock deep below the surface of the earth. The experiment has been carried out at Atomic Energy of Canada Limited's (AECL's) Underground Research Laboratory near Lac du Bonnet, Canada, in support of international programs for geologic disposal of radioactive waste. The TSX, with partners from Canada, Japan, France and the United States, was carried under conditions of high pressure (up to 4 MPa) and elevated temperature (up to 85°C). Comparing numerical model predictions with eight years of data collected from approximately 900 sensors was an important component of this experiment. Model of Transport In Fractured/porous Media (MOTIF), a finite element computer program developed by AECL for simulating fully coupled or uncoupled fluid flow, solute transport and heat transport, was used to model both the ambient temperature and heated phases of the TSX. The plan to heat the water in the TSX to 85°C was developed using model predictions and a comparison of simulated results with measurements during heating of the water in the TSX to about 50°C. The three‐dimensional MOTIF simulations were conducted in parallel with axisymmetric modelling using Fast Lagrangian Analysis of Continua (FLAC), which computed the heat loss from pipes that carried the heated water through the rock to and from the experiment. The numerical model was initially used to develop a plan for operation of the experiment heaters, and then subsequently used to predict temperatures and hydraulic heads in the TSX bulkhead seals and surrounding rock. Copyright © 2005 John Wiley & Sons, Ltd.     

A simulation of large‐scale groundwater flow and travel time in a fractured rock environment for waste disposal purposes

Two‐dimensional regional groundwater flow was simulated based on a conceptual model of low‐permeability crystalline rocks of the Whiteshell Research Area (WRA) in south‐eastern Manitoba. The conceptual model consists of fracture zones that strike in different directions and dip at various angles in the background rock mass. The thickness and hydraulic properties of the fracture zones in the conceptual model were varied as were the fluid properties and the boundary conditions of the groundwater flow system. The effects of these variations on the groundwater flow pattern and on the convective travel time along pathways from a hypothetical disposal vault at 500 m depth to discharge locations at the ground surface were evaluated. The vault was located in the regional discharge area of the groundwater system. A homogeneous conceptual model of the WRA, having only freshwater flow, formed a groundwater flow pattern with a regional flow system. Local flow systems developed increasingly with the introduction of fracture zones 20 m and 3 m thick, and depth‐dependent fluid density. This indicates a reduction in groundwater residence time by fracture zones and fluid density. Flow pathways were analysed using both a stream‐function and a particle‐tracking technique. The pathways and their lengths from the location of the vault to the surface varied spatially according to the flow patterns. The minimum travel time along these pathways was less than 150 000 and greater than 4 000 000 years in models with and without fracture zones, respectively, indicating that the presence of fracture zones was the major controlling factor. A precise knowledge and refinement of conceptual model parameters is necessary during site selection for waste disposal purposes. Copyright © 2004 John Wiley & Sons, Ltd.     

Phosphorus retention in constructed wetlands enhanced by zeolite- and clinopyroxene-dominated lava sand

Constructed wetlands (CWs) are engineered systems for treating wastewater by sequestering nutrients and contaminants. Our aim was to assess the main phosphorus (P) binding states in operating CWs to assess P saturation and indications on P recycling potential of filter materials, which might be necessary under future peak P scenarios. The investigated vertical flow CWs (operation time up to 16 years) are based on either fluviatile (Fluv) sand or zeolite- (Ze-LS) and clinopyroxene (Cl-LS)-dominated lava sand. Organic and inorganic P accumulated in all CWs independent of filter materials and showed a considerable increase with operation time. Concentrations of P decreased sharply with depth in the Fluv-CWs compared to only a slight decrease in the lava sand CWs, with P concentrations of deeper horizons approximating the relatively P enriched original lava sand substrates. Orthophosphate was the dominant pool in all CWs, while the sum of organic fractions ranged between 11% and 33%. Sequential extraction indicated that P was mainly associated with Fe and Al (hydr)oxides for Fluv-CWs and Ze-LS-CWs, while Ca and Mg bound mineral phosphates dominated in Cl-LS-CWs. Oxalate extractions pointed to a clear dominance of P fractions associated with poorly crystalline Fe- and Al-(oxy)hydroxides. Solution ³¹P NMR analyses revealed that inositol hexakisphosphates were a major pool of organic P in surface layers of CWs, which increased with operation time. With a maximum of 0.5% P content, filter sands do not appear to be a suitable fertilizer for direct application to agricultural fields. The dominance of inorganic, poorly crystalline P species point to potentially high desorption capacity which might be investigated further, to assess recycling potential of P or usage of filter materials as soil amendments with relatively high plant available P. The latter might become feasible and economically attractive under future P scarcity. Simultaneously, P saturation indexes (DPS) did not indicate an imminent P saturation of filters, since P accumulation was not restricted by binding to Al and Fe minerals.     

Study of Ni exchangeable pool speciation in ultramafic and mining environments with isotopic exchange kinetic data and models

Soils and ore samples influenced by mining and metallurgical activity were collected in ultramafic soils (UM) complexes of Barro Alto and Niquelândia, in order to determine the contribution of each Ni bearing phases to the total exchangeable pool of Ni, and to point out if this pool was affected by anthropic activities. For this purpose, the IEK-model previously developed by the group (Zelano et al., submitted) was applied, on the basis of IEK experiments performed on pure typical Ni scavengers (serpentines, chlorite, smectite and iron oxydes) from ultramafic systems. For each typical scavenger, this model describes the percentage of Ni associated to exchangeable pool(s) as well as their corresponding kinetic constant(s) of exchange. The mineralogical composition of soil and ore samples and Ni solid speciation were first determined, and the IEK-model was applied on these bases. In almost all samples, an important contribution of serpentine to Ni exchangeable pool was highlighted, ranging between 10% and 45%. The important amount of organic matter (OM) in one of the studied soil samples, allowed to extrapolate generic OM E_Ni and k parameters, which were introduced in the IEK-model to improve its predictive capability. Obtained results provided evidences of how even a small content (3 wt%) of organic carbon (OC), can represent an important contribution of OM to the total E_Ni pool (60%). In the investigated ore samples, up to the 60% of E_Ni was attribute to smectite, responsible for fast E_Ni pool kinetic evolution. In addition, the model highlighted the role of the Fine Black Ash (FBA), by-products of the pyrometallurgical activity, detected into a soil sample, that is responsible for the 15% of E_Ni. This approach allowed to determine, for the first time, the relative contribution of each Ni bearing phase to the total exchangeable pool, in terms of concentration and kinetics.     

Application of 3D hydrodynamic and particle tracking models for better environmental management of finfish culture

Hydrographic conditions, and particularly current speeds, have a strong influence on the management of fish cage culture. These hydrodynamic conditions can be used to predict particle movement within the water column and the results used to optimise environmental conditions for effective site selection, setting of environmental quality standards, waste dispersion, and potential disease transfer. To this end, a 3D hydrodynamic model, MOHID, has been coupled to a particle tracking model to study the effects of mean current speed, quiescent water periods and bulk water circulation in Mulroy Bay, Co. Donegal Ireland, an Irish fjard (shallow fjordic system) important to the aquaculture industry. A Lagangrian method simulated the instantaneous release of “particles” emulating discharge from finfish cages to show the behaviour of waste in terms of water circulation and water exchange. The 3D spatial models were used to identify areas of mixed and stratified water using a version of the Simpson-Hunter criteria, and to use this in conjunction with models of current flow for appropriate site selection for salmon aquaculture.The modelled outcomes for stratification were in good agreement with the direct measurements of water column stratification based on observed density profiles. Calculations of the Simpson-Hunter tidal parameter indicated that most of Mulroy Bay was potentially stratified with a well mixed region over the shallow channels where the water is faster flowing. The fjard was characterised by areas of both very low and high mean current speeds, with some areas having long periods of quiescent water. The residual current and the particle tracking animations created through the models revealed an anticlockwise eddy that may influence waste dispersion and potential for disease transfer, among salmon cages and which ensures that the retention time of waste substances from cages is extended.The hydrodynamic model results were incorporated into the ArcView^TM GIS system for visualisation and interrogation of results and to allow effective holistic environmental management and site selection for fish cage aquaculture.     

复合硅藻土混凝剂的制备及在油田废水处理中的应用

由于目前人类生活生产所产生的废水、污水对环境造成了严重的污染,尤其是工业废水、油田废水,对环境的威胁极其严重,污水的处理已成为人类进步与发展过程中的重要课题。本文通过选取改性剂,成功地制备出了复合硅藻土混凝剂。在对油田废水的处理中,提高了除油率。     

废泥浆脱水的试验研究

岩土工程施工产生的废泥浆含水量高,脱水性差,因此如何提高废泥浆的脱水量至关重要。试验中通过对废泥浆的物理化学调质,以改变废泥浆颗粒表面物化性质和组分,破坏废泥浆的胶体结构,减小与水的亲和力,从而改善废泥浆的脱水性能。对不同种类的无机材料和有机高分子絮凝材料的试验分析发现,有机高分子聚丙烯酰胺PAM的絮凝脱水效果要优于无机材料。在阳离子型PAM、阴离子型PAM、非离子型PAM三类材料对废泥浆的絮凝脱水效果中,阳离子型PAM的絮凝脱水效果最好。