银山矿田外围找矿方向

外围找矿是资源危机矿山的一个重要找矿方向,本文根据银山矿田成矿规律和成矿模式,结合银山铜铅锌金银多金属矿床的地质特征。笔者提出了银山矿田的Z型探矿模式,利用该模式指导银山矿田外围找矿,确定外围找矿方向和靶区。     

借鉴石咀子铜矿开采经验探讨银山矿深部开采问题

本文首先对石咀子矿深部开采情况作一简介,提出该矿和银山矿遇到的类似问题,并对出现这些问题的原因进行分析.最后对银山矿在深部开采中应用留矿采矿法的可行性作出分析.     

银山矿床成因的再研究与找矿耙区的预测

本文在前人研究的基础上 ,简述了本人对银山矿床成因的认识和在找矿工作中的应用。为今后对银山矿田区域内寻找深部铜金资源、边缘铅锌资源有着重要的指导意义。     

银山矿床成矿作用时空特征及矿床成因分析

银山矿床的形成多与燕山期第二阶段轻微的次火山岩具有非常密切的时空特征和物质组成关系,次火山岩大多来自于深部隐伏岩体的岩浆分异流体和溶体产物。至于产物形成的特殊性,且分布特征也具有多中心、对称性、叠加性和定向性。本文为了进一步探究银山矿成矿作用的时空特征和矿成因,进一步研究银山多金属矿床的成矿时空分布特征和成矿原因。     

江西省银山次火山热液型铜铅锌矿床研究进展

江西银山矿床属铜铅锌多金属矿床,矿体主要产在中-新元古界地层双桥山群地层之中,与燕山期构造—岩浆活动有着成因上的密切联系,为一个特大型火山-次火山热液矿床。最新研究成果表明,银山含矿岩体通过多期的作用形成,主要有3个旋回,其中第2旋回为主要成矿期。银山的含矿岩体形成于中侏罗世,180-170Ma,主量、微量元素与稀土元素特征显示,银山火山-次火山岩具埃达克岩属性。     

导坑——留矿法开挖硐室在银山铅锌矿的应用

银山铅锌矿银山西区3~#竖井于1989年8月动工基建,1991年5月竖井主体开拓工程基本完成.如何开挖该竖井-240m中段水泵房和中央变电硐室,形成完善的竖井排水系统,加快银山西区开拓,是银山矿1994年的重点工程.本文就应用导坑——留矿法开挖3~#竖井-240m中段水泵房和变电硐室的实践作一扼要述评.     

降低银山矿北山区采矿损失率的途径探讨

扼要的介绍了银山矿北山区开采技术条件和目前采矿现状，分析了造成北山区采矿损失率高的原因，提出了降低北山区采矿损失的途径。     

银山外围天门村—孔家地区地质特征及找矿方向

银山矿床是大型火山岩—次火山岩型银铅锌多金属矿床,在新一轮的地质找矿进程中,取得了显著的找矿成果,银铅锌多金属资源量不断扩大,而其外围仍然没有突破。通过对银山矿床外围的地质特征及物化探资料总结和分析,认为银山南西方向天门村—孔家地区具有较好的找矿潜力,对今后在该区地质找矿工作具有一定的指导意义。     

降低贫化损失的经验

矿产资源是矿山的物质基础。本文分析了贫化损失产生的原因，为了保护资源，提高矿山的经济效益，银山矿采取了一系列措施，加强生产技术管理，降低贫化损失。     

新型滚动给矿机

根据银山铅锌矿选厂原使用的下矿漏斗直接给矿、摆式给矿机给矿和电振给矿所存在的问题，设计出新型的滚动给矿机，通过生产实践，效果良好。     

Drawdown due to Temporally Varying Pumping Discharge: Inversely Estimating Aquifer Parameters

A ramp kernel method is proposed for accurately calculating the drawdown due to any temporal variation in pumping discharge. The use of the ramp kernels assumes the linear variation between the two consecutive measured pumping discharges. The prior studies assume a rectangular variation between the two consecutive measured pumping discharges. In the rectangular variation, a uniform pumping rate is assumed during a time span. An analytical equation for calculating the ramp kernel is derived. An optimization method is used with the proposed ramp kernels for inversely estimating the aquifer parameters from drawdown due to an arbitrary unsteady pumping discharge. Unlike the prior methods, the proposed method accurately identifies the parameters even when the sampling interval for the drawdown and pumping discharge is longer than that needed for assuming a linear variation. The proposed method outperforms the prior method. Application of the proposed method is illustrated using examples.     

Below-Average Bidding Method

The low-bid method, typically used for competitive bidding in the United States, may result in a contract with a firm that submits either accidentally or deliberately an unrealistically low-bid price. Such an occurrence hurts both the owner and the contractor by promoting disputes, increased costs, and schedule delays. To address this problem, other countries have adopted bidding methods based on the average of the bids submitted. One such approach is the below-average method where the winning bid is closest to but below the average of all bids. A competitive bidding model for the below-average-bid method is presented and its merits relative to the average-bid method and the low-bid method are explored. The below-average-bid process is investigated analytically and through Monte Carlo simulation. The results of bidding models for the below-average, the average, and the low-bid methods are presented in four easy-to-use nomograms which allow contractors to determine the optimal lump-sum bid price for each method without the need for complicated analysis. A comparison of the three methods provides information and insights to help owners with the difficult choice of a suitable bidding method for the project at hand.     

Failure Resistance of Historic Stone Bridge Structure of Charles Bridge. II: Susceptibility to Floods

The paper is a follow-up to the first part devoted to an analogical problem investigated with a view to the degradation of the stone structure due to the effects of nonstress load, and it deals with the probability problem of the bridge structure collapse under the effect of an extreme flood wave. The paper presents the results of the numerical analysis of the response of the historic stone bridge structure of Charles Bridge of the 14th century to the flood wave effect simulated by angular rotation, subsidence, and shifting in the footing bottom of a bridge pier. Special focus is on the effect of interventions into the stone bridge structure dating back to the last major overhaul of 1967–1975, particularly, on the effect of the reinforced concrete slab (tie plate) connecting the opposite bridge breast walls increasing the rigidity of the breast walls and their structurally efficient connection to the vaults of the bridge arches. The numerical analyses performed point out the prevailing negative effects of the implemented interventions in terms of structural rigidity of the stone bridge structure exposed to the effect of a flood wave.     

Addition of Cobalt to Lead Anodes Used for Oxygen Evolution—A Literature Review

A review of the literature dealing with the effect of cobalt on lead-based anodes for oxygen evolution during electrolysis of sulfuric acid solutions verifies that the presence of cobalt at the anode–electrolyte interface, either as constituent of the anode material or as ions in the electrolyte, catalyzes the evolution of oxygen and reduces the corrosion of the anodes and the contamination by lead of metal cathodes produced during electrowinning. However, due to harmful effects of cobalt ions on the cathodic reaction in some processes, these benefits are limited to the electrowinning of copper. Efforts to develop a way of introducing cobalt at the anode–electrolyte interface without interfering with the cathodic reactions are reviewed in this paper. The use of lead–cobalt alloy anodes has had limited success due to issues arising from the low solubility of cobalt in lead, segregation during casting of the alloys, and nonuniform distribution of cobalt which affects the integrity of the anodes. This has been overcome in part lately by inclusion of cobalt into only the surface layer of a lead or lead alloy substrate, by thermal treatment of a cobalt salt to form a catalytic cobalt oxide surface species, or by electrodeposition of composite lead–cobalt oxide anodes. The last approach in particular has been actively investigated by several groups, but to our knowledge it is yet to find application in the industry. The review also critically examines the likely reaction mechanisms involved.     

New Orleans Levee System Performance during Hurricane Katrina: London Avenue and Orleans Canal South

Hurricane Katrina was one of the worst natural disasters in U.S. history. The effects of the hurricane were particularly devastating in the city of New Orleans. Most of the damage was due to the failure of the levee system that surrounds the city to protect it from flooding. This paper presents the results of centrifuge models conducted at Rensselaer Polytechnic Institute and the U.S. Army Corps of Engineers simulating the behavior of the levees at London Avenue North and South that failed during Hurricane Katrina. Those levees failed without being overtopped by the storm surge. Also included are the results of a centrifuge model of one levee section at Orleans Canal South, which did not fail during the hurricane. The key factor of the failure mechanism of the London Avenue levees was the formation of a gap between the flooded side of the levee and the sheetpile. This gap triggered a reduction of the strength at the foundation of the protected side of the levee. The results are fully consistent with field observations.     

Leaching Behavior of Lead, Chromium (III), and Zinc in Cement/Metal Oxides Systems

This paper reports the study of the leaching behavior of cement/metal oxides mixtures containing lead, chromium (III) and zinc oxides. A fractional factorial design of experiments (24?1) was carried out considering four factors, the concentration of ZnO, Cr2O3, PbO, and Fe2O3 in the formulations. Iron oxide was also included in the experimental design as it is usually the main constituent of industrial wastes from thermal processes, where lead, chromium and zinc oxides are also found. After 56 days of curing, samples were subjected to the Acid Neutralization Capacity Test and the concentrations of Cr, Zn, and Pb were determined in the leachate at different pH after filtering. The output variables for the analysis of the experimental data were the concentration of metals at initial pH (in water), at pH 9, 7, and 4, and the acid neutralization capacity of the samples at pH 9. The analysis of the results indicates that the immobilization of Zn and Pb in Portland cement is poor; these metals behave as their amphoteric hydroxides. However, the leaching of Cr (III) is in the range found in the control sample, indicating that the stabilization of Cr (III) is successful.     

Case Study of Fluvial Modeling of River Responses to Dam Removal

A plan was made to remove Matilija Dam on the Ventura River. With dam removal, the delta in the reservoir and the downstream channel were expected to undergo major changes in morphology. The FLUVIAL-12 model was employed to simulate reservoir and river channel responses after dam removal. As a first step, the model was calibrated using the Ventura River data to establish its validity. In calibration, the model was used to simulate the fluvial processes starting from the time of dam completion. The simulated sediment deposition above the Matilija Dam matches closely with the deposits measured by the U.S. Bureau of Reclamation. A large amount of sediment was stored in the reservoir; some of the stored sediment would be transported downstream after dam removal. An important consequence of dam removal is the major increase of sediment release to the river channel downstream. The sediment supply to the downstream reach is not only from the stored sediment in the reservoir but also from natural sediment inflow from the upstream watershed. Therefore, sediment supply to the downstream reach will exceed the natural sediment flow before the dam presence. This situation tends to overload the downstream reach with sediment, resulting in excessive deposition. The amount of sediment release from the area above the removed dam is closely related to the changes in reservoir morphology. It is necessary to model changes in the channel bed profile and channel width during erosion in order to determine the amount of sediment removal. The amount of sediment release may not be simulated using an erodible-bed model but it may be determined using an erodible boundary model.     

Bridge Blockage and Overbank Flow Simulations Using HEC–RAS in the Keelung River during the 2001 Nari Typhoon

On September 16, 2001, Typhoon Nari resulted in severe flooding in the Keelung River basin. More than 1,000 shipping containers were swept by the rising water from the floodplain into the river, blocking 14 bridges. A severe overbank flow due to the blockage occurred at the Ba-Tu Railway Bridge. The overbank flow then passed through a railway tunnel and inundated Keelung City, resulting in significant damage. The objective of this study was to determine the influence of the bridge blockage and the Ba-Tu overbank flow on the water stages in the Keelung River during Typhoon Nari. The floating-pier-debris module and the lateral-weir module in the Hydrologic Engineering Center–River Analysis System (HEC-RAS) unsteady-flow routing model were applied to investigate water stage variation due to the bridge blockage and overbank flow. The numerical simulation results provided by this study served as an important reference for authorities who needed to clarify the responsibility of the containers’ owners for the loss of lives and property during this typhoon.     

Pseudostatic Coefficient for Use in Simplified Seismic Slope Stability Evaluation

Pseudostatic slope stability procedures are commonly used in engineering practice. However, the selection of the seismic coefficient employed in the analysis is often based on precedence without due consideration of the amount of seismic displacement that constitutes satisfactory performance for each particular project and without incorporating the vastly different seismic exposure for sites around the world. In this Note, a rational basis for selecting the seismic coefficient is presented. The proposed procedure requires that the engineer establishes the project-specific allowable level of seismic displacement. The seismic response characteristics of the slope are represented by the fundamental period of the potential sliding mass, and the site-dependent seismic demand is characterized by the 5% damped elastic design spectral acceleration at the degraded period of the potential sliding mass. The level of uncertainty in the estimates of the seismic demand and displacement can be handled through the use of different percentile estimates of these values. With the proposed equations, the engineer can properly incorporate the amount of seismic displacement judged to be allowable and the seismic hazard at the site in the selection of the seismic coefficient.     

Reliability-Based Optimal Design of Truss Structures Using Particle Swarm Optimization

In this work, the particle swarm optimization method is employed for the reliability-based optimal design of statically determinate truss structures. Particle swarm optimization is inspired by the social behavior of flocks (swarms) of birds and insects (particles). Every particle’s position represents a specific design. The algorithm searches the design space by adjusting the trajectories of the particles that comprise the swarm. These particles are attracted toward the positions of both their personal best solution and the best solution of the swarm in a stochastic manner. In typical structural optimization problems, safety is dealt with in a yes/no manner fulfilling the set of requirements imposed by codes of practice. Considering uncertainty for the problem parameters offers a measure to quantify safety. This measure provides a rational basis for the estimation of the reliability of the components and of the entire system. Incorporating the reliability into the structural optimization framework one can seek a reliability-based optimal design. For the problems examined herein, the reliability indexes of the structural elements are obtained from analytical expressions. The structure is subsequently analyzed as a series system of correlated elements and the Ditlevsen bounds are used for the calculation of its reliability index. The uncertain-random parameters considered in this work are the load, the yield-critical stress; and the cross sections of the elements. The considered design variables of the optimization problem are the cross-sectional areas of the groups, which control the size of the truss, and the heights and lengths that control the shape of the truss. The results of the optimization are presented for a 25-bar truss and a 30-bar arch and the robustness of the optimization scheme is discussed.