Search Documents

By Dennis McLaughin

This report contains a description of the contract activities performed by ENSCO, Inc. under contract No. H0178069. The purpose of this project was to enhance the Bureau of Mine?s Cableless Electronic Survey System use to aid in the drilling of long (approx. 2000 feet) boreholes in coal. This drilling is performed as part of the methane drainage program. The system that was ultimately developed was field tested 2nd demonstrated in actual in-mine drilling activities. The significance of this system as compared to previous drill survey systems is the fact that it surveys without having to be inserted and removed for each survey point. It is so designed that it can withstand the shock and vibration experience by the drill string during drilling. This means an increased productivity is now possible in that drill operators can determine drill bit positioning in a near real-time environment.

Jan 1, 1981

By Blom W. M

Shareholders, creditors, government agencies and auditors all have a different perspective of financial reports which is determined by the uses to which they put the information disclosed in the report.Shareholders today are better informed than previously and are more aware of the market in which they are investing. This is the result of the increasing role of institutional investors and the increasing reliance being placed on analysts to interpret financial information.

Jan 1, 1990

By L. B. Rothfeld

This paper presents preliminary results of a Bureau of Mines study of potential costs of compliance with the federal Resource Conservation and Recovery Act for copper heap and dump leaching. Specifically, estimates are given for the cost of compliance with possible technology standards that would require the use of liners and closure caps regardless of terrain and underlying geology and hydrology. This cost is compared to the co lit of compliance with present state requirements for terrain a typical of those found at existing copper leach sites in the Southwestern U.S.A. Incremental compliance costs are found to widely exceed screening criteria used by the Environmental Protection Agency to denote significant economic impact.

Jan 1, 1993

By P. O. Metz, E. L. Wiehe, J. S. Foster

BASED on their analyses of growth kinetics, ibbs' and Harris et al.' have recently proposed that the rate of subcritical graphitization of steel is controlled by the rate of diffusion of carbon in ferrite. illert has concluded that this is the rate controlling growth mechanism when the growing graphite particles are relatively large. Harris et al.' also propose that the matrix surrounding a growing graphite particle is plastically deformed to make room for the growing particle. If this plastic deformation does occur, then preferred recrystallization may be observed around the larger particles. If diffusion of carbon in ferrite is rate controlling, then a graphite particle growing in a matrix of, say, tempered martensite or pearlite, should be surrounded by a carbide depleted zone. Thus, the simple metallographic experiments reported here are sufficient to determine whether or not diffusion of carbon in ferrite is the dominant mechanism for the growth of graphite in steel. The present investigation considers graphitization in five alloys. The compositions are given in Table I. Graphitization was carried out at three temperatures: 900°K (627"C), 950°K (677"C), and 990°K ('717°C). Samples were reacted in both the martensitic and the pearlitic initial conditions. In the hypoeutectoid steels, Sets 7 and 8, .and in the hypereutectoid Fe-C binary, Set 6, graphitization was very limited after 1000 hr at temperature. In these samples graphite particles observed were less than 10 p in diam. In the hypereutectoid commercial steels, Sets 1 and 3, large graphite particles (100 p) did not appear until after 250 hr at temperature. The limited number of graphite particles observed and the range of sizes obtained prohibited measurement of growth rates in this investigation. However, in all samples showing graphitization, neithe a carbide depleted zone nor recrystallization was observed. illert's model predicts that diffusion of carbon in ferrite should become dominant for graphite particles larger than about 300 p in diam. The largest graphite particle observed in this investigation was approximately 450 p in diam. No evidence of carbide depletion was noted. Fig. 1 shows a typical graphite particle. This nodule is from an initially pearlitic sample from Set 3 after

Jan 1, 1970

By Steve Karl

Introduction Technological advances in mining and processing have started the domestic mining and mineral industry back on the road to competitiveness. A massive trade deficit, however, coupled with foreign competition and more government regulations threaten to slow this recovery. So say mining executives in Colorado and Minnesota. These industry decision-makers agree that their challenge is to continue the technical innovations of their industry. The journey back to profitability and competitiveness means improved products, they say, but at lower production costs. At separate gatherings in January, officials in both states said that they believe their industry is up to the challenge. Worker attitudes will have to change, they understand, and management styles will need adjusting. And, while they are willing to make the necessary adjustments, they are going to need some help. Or, at the very least, less interference from the federal government. Foreign markets, all but closed to American products, must be opened up on a reciprocal basis. The nation's $170 billion trade deficit is a priority item that can no longer be ignored. And, closer to home, federal and state environmental regulations concerning mineral production must themselves be monitored. 1987 in Colorado While Colorado's service and trade industries should have a fairly good 1987, the state's mining industry can expect another disappointing year filled with layoffs and declining profits, according to the Colorado Mining Association. Once again, foreign competition and government regulations are seen as the main reasons for the mineral industry's woes. And state mining officials see little relief until at least the 1990s. Speaking to a group of reporters at its annual press briefing in Denver, CMA officials said Colorado's overall nonfuel mineral production is expected to fluctuate between a flat and declining growth trend. Mining employment in the state is expected to fall by 400 people this year, to about 7500. In 1981, Colorado mines employed as many as 17,800 people. During the 1970s and early 1980s, the employment rate in mining in the state grew by 12% annually, according to a summary report compiled by the CMA. Last year, worldwide molybdenum production continued to exceed demand US moly producers, therefore, were forced to continue their familiar path of production cutbacks, as well as workforce reductions. And some molybdenum mines in the US closed altogether, the CMA report stated. In Colorado, Amax's Climax and Henderson molybdenum mines operated at about 50% of combined capacity. Climax employed about 200 people at the beginning of 1987, producing about 5.4 kt/d (6000 stpd) or ore. Henderson employed about 700 people, producing about 24.5 kt/d (27,000 stpd) of ore. In coal, the number of licensed coal mines in Colorado has declined from 124 in 1960 to 43 in 1986, of which only 23 were producing. Once a stable source of employment and production, the metallurgical coal industry in the state has only one surviving metallurgical coal mine, Mid-Continent's Orchard Valley mine. High production and transportation costs, weakness in the US steel industry, and a weak market position have contributed to the decline, the summary reported. "The challenge facing most mining companies in the United States today is to survive," said

Jan 3, 1987

By H. R. Bullis

"Abstract- This paper discusses what appears to be a flaw in the current belief, widely held within the gold mining industry and investment community, that the creation of ever-larger gold mining companies is desirable for mining companies and investors alike. The basis of the flaw is in the underlying assumption that very large gold producers can discover or acquire new gold deposits of the size necessary to replace extracted reserves on a year-on-year basis over the intermediate to long term (i.e., five to ten years and longer). As it will be noted in this paper, deposits of the size required to replace annual production of very large gold producers (VLGPs) are relatively few in number. Although discoveries of new gold deposits continue to be made, they are predominantly in the 0.5 to 2.0 million ounce range. Data represented here suggest that, although gold production from individual VLGPs continues to increase, the change is due to merging or acquiring other companies or projects with similar reserve life profiles. Therefore, the reserve life profiles of VLGPs have remained flat or have decreased.The paper will note recent changes in the industry and the remarkable increase in gold production reported by individual mining companies over the past several years. It will provide an overview of the geographical and geological distribution of known gold deposits and the range of deposit sizes. Finally, the paper will discuss the challenges that face large gold producers in replenishing their reserves that are being depleted at an ever-increasing rate. Unless otherwise stated, all production and reserve data have been taken from company documents in the public domain or publicly available information."

Jan 1, 2001

By Alcides Freitas

The great importance of aggregates as a basic building and maintenance material for both public and private projects makes the identification and availability of this valuable resource imperative for our economic and social well being. This was one of the main reasons that led the California Legislature to enact the Surface Mining and Reclamation Act of 1975 (SMARA). The Act requires the State Geologist to classify mineral areas in the state and the State Mining and Geology Board to designate mineral deposits of regional or statewide significance. What is the "Classification and Designation" process and how is it working?

Jan 1, 1984

By V. T. McLemore

Petrographic analysis of rocks is traditionally performed with optical microscopy using thin sections and point counting. However, this does not provide accurate mineral proportions for sedimentary, volcanic, and soil-like material, because rock fragments, groundmass, and matrix are not identified as specific minerals. In addition, groundmass phases in volcanic rocks can be too fine to identify individually, and making thin sections of intact soil-like material is difficult because much of the material is not well cemented. ModAn is a normative calculation that estimates modes ??by applying Gaussian elimination and multiple linear regression techniques to simultaneous mass balance equations? (Paktunc, 2001) and allows location-specific mineral compositions to be used. One of the features of ModAn that makes it appropriate for this study is that it can model one of several sulfide minerals. Mineral compositions for Questa minerals were determined from electron microprobe analysis and entered into ModAn. Then by combining and normalizing results, bulk quantitative mineralogy can be determined using ModAn, petrographic observations, electron microprobe analysis, clay mineral analysis, and the whole-rock chemistry of the sample.

Jan 1, 2009

By Steven J. Page, Wm. Randolph “Randy” Reed, John A. Organiscak

Researchers studying dust generation from blasthole drills developed a simple, quick fix that reduced respirable dust concentrations by more than 63% at the dump point. This device, which requires almost no maintenance, is small and inexpensive, and it will help operators maintain compliance to the dust standard. The thought process was that a reduction of respirable dust at any of the multiple sources on the drill, in this case the dust collector dump point, should reduce the total respirable dust generated by the drill. The U.S. Mine Safety & Health Administration (MSHA) has a coal respirable dust standard of 2 milligrams per cubic meter (mg/m3) for an 8-hour shift. MSHA and mine operators periodically collect personal dust samples to determine compliance with this dust standard. Drill operators have one of the highest exposure levels to respirable dust. This has been proven through many reviews of the MSHA dust sampling database. Prior to 1987, the highwall driller at surface coal mines had the most severe exposure to respirable silica dust, a trend that continues today based on MSHA's respirable dust sampling database. A review of the MSHA database for the years 1985 through 1992 shows that 81% of the respirable silica dust samples taken exceeded the permissible exposure limit for the highwall drill operator at surface coal mines. A more recent review of the MSHA database, for the years 1996 through 2000, shows that only 31% of the respirable silica dust samples taken exceeded the respirable silica dust limit for the highwall driller at surface coal mines. This suggests a substantial improvement in preventing the exposure of silica dust to the highwall drill operator. The drill operator, however, still tops the list of job occupations that have the highest exposure to respirable silica dust Respirable dust has been shown to be harmful to human health, especially when silica is present in the dust. It causes a disease known as silicosis, which can occur in three levels: chronic silicosis, which occurs after 10 years of exposure; accelerated silicosis, which occurs between 5 and 10 years of exposure; and acute silicosis, which can occur within a few weeks to five years of very high exposure to silica dust. Respirable dust consists of the dust particle size fraction whose median diameter is 4 micrometers (µm). The drilling machine generates high concentrations of respirable dust from several sources: drill table shroud leakage, dust leakage through the table bushing, dust discharge from the dust collector exhaust due to impaired filters, and dust entrained from the dust collector fines dumped onto the bench. The National Institute for Occupational Safety and Health's (NIOSH) Pittsburgh Research Lab (PRL) has been studying different methods to reduce respirable dust from these sources. During its testing, the institute identified a simple solution that reduces the amount of respirable dust generated at the collector dump point.

By Sanket Rawat, Ravi Kant Mittal, Vikash Prasad

"The understanding of the response of pile foundations under various types of loads is a necessary prerequisite to analyze and design them properly. Therefore, this paper highlights and compares the provisions available in Indian Standard IS 2911:2010 to estimate the capacity of laterally loaded pile foundation with the provisions available in different country codes and existing literature. Comparisons are made between the Indian standard method, Broms method and Matlock & Reese method for the analysis of laterally loaded piles due to popularity and prevalence of the later methods in design offices worldwide. This has been achieved using a parametric study on pile embedded in pre-consolidated clay and sand for both fixed head and free head case in terms of displacement and ultimate load capacity. It has been found that there are various limitations to the Indian Standard method associated with various cases such as short pile analysis, complete moment distribution etc. Therefore, suitable recommendations have been made on the basis of the above comparison to improve the accuracy of the design in Indian perspective. The proposed comparison and subsequent area of improvements will present the design engineers all across the globe, a broad sight of design specifications of laterally loaded piles.INTRODUCTIONPiles in groups are very often subjected to both axial and lateral loads. In the 1960’s, designers used to assume that the piles could carry only axial loads and the lateral load is to be carried by batter piles. However, later, a large number of load tests authenticated that vertical piles also can transfer lateral loads through shear, bending, and lateral soil resistance rather than purely acting as axially loaded members. Initial attempts to analyze laterally loaded piles used the finite-difference method, as described by Howe (1955), Matlock and Reese (1960), and Bowles (1968). Matlock and Reese (1956) used the finite difference method to get a series of non-dimensional curves to enable the user to input the appropriate curve with the given lateral load and estimate the ground-line deflection and maximum bending moment in the pile shaft. Later, Matlock and Reese (1960) extended the earlier curves to include selected variations of soil modulus with depth."

Jan 1, 2017

By B. V. Knelson

"GENTLEMEN:This paper will deal with centrifugal separation - theory and practical, and since the Knelson Concentrator is the only centrifugal concentrator with a properly fluidized bed, this paper will cover the Knelson Concentrator and its technical and structural advances over the last five years. As I am the person with the most experience in this line, I guess I am some kind of an expert; what kind I’m not sure, but some kind.This type of concentrator truly was developed because I’m lazy and I constantly look for easier ways to do things. My experience in the mining industry was very limited but I did realize in looking at placer operations, which is the application where I spring from, that it was tremendously labour intensive and my first reaction that ""my god, there must be some method or way-of handling product in a more efficient (and you can read that as being able to quickly recover very fine particle gold) way than was being shown at that time"". So, the Knelson Concentrator was born - about 6 or 7 years later. Our first attempt was a cone with about the same degree of slope as our present machine and since we had no knowledge of vibration dampening and centrifugal forces at that point, it was just an idea that this should work.Our first run was one of twenty minute duration. We did make that first machine variable speed by a mechanical belt system and we found that at about 240 rpms we were virtually shaking the gravel plant apart that we were attached to. So the first run was twenty minutes and back to the drawing board. However, that first run produced a concentrate so superior to anything we had seen previously, that we knew without any question, we were definately and accurately on the right track."

Jan 1, 1985

By K. G. Stowe

"1. Introduction Mattagami Lake Mines and Orchan Mines operate zinc copper mines adjacent to one another near Matagami, Quebec, situated approximately 300 kilometres north-east of Rouyn-Noranda. (Note: Mattagami Lake and Orchan are in the process of being absorbed by Noranda Mines and will become Noranda Mines-Matagami Division). Both concentrators began operations in late 1963.The Mattagami Lake concentrator is capable of treating up to 3,500 metric tons per day of massive sulphide ore with a mineral composition shown in TABLE 1. The Orchan concentrator consists of two separate circuits - the Orchan circuit with a capacity of 1,050 metric tons per day and a custom circuit with a capacity of 825 metric tons per day. Throughout its operation, Orchan has custom milled ore from several smaller deposits in the Matagami district."

Jan 1, 1979

By A. J. Magerowski

Energy consumption is a main component of operational costs for the comminution of mineral bearing ores. Reduction of energy consumption has continually been addressed by mill operators and equipment manufacturers. Our testing over the last few years strongly indicates that the overall energy needed to comminute a mineral bearing ore can be brought down significantly, if more work is done in the crushing stages of the comminution circuit.This calls for uprating of the conventional crushing equipment into a new generation of crushing equipment to produce finer products. This will result in the emergence of new ideas in the design and application of equipment and corrnninution circuits.

Jan 1, 1986

By G Akdogan, R V. R Handfield-Jones

The application of microwave energy as a substitute for conventional heating has drawn interest from many researchers in extractive metallurgy. Microwaves have a heating effect just as many other forms of radiant energy. Microwaves are able to penetrate the substance at which they are directed and in being absorbed heat the material from the inside. As a result of heat generated in the interior of a particle, microwaves can affect the rupture of a particle (in this case a host ore) and break down the matrix of the particle (host ore) and expose the recoverable mineral to the leaching reagent. Two series of leaching experiments were carried out at temperatures above 90????C using a conventional heater (hot plate) and a modified 850 W, 2.45 Ghz microwave oven. One series of tests was carried out at ambient temperature. A pyritic/arsenopyritic gold concentrate was leached with 3.3 kg/t to 6.8 kg/t NaCN for two hours. The extraction of gold at 6.8 kg/t NaCN was higher in microwave assisted leaching (59 per cent) than the extraction obtained in leaching at conventional heating (39 per cent) and ambient temperature (28 per cent). Extraction of gold was dependent on the size fraction used and was 48 per cent for û75 ¦m, 43 per cent for û90+75 ¦m and 37 per cent for û150 + 90 ¦m size ranges.

Jan 1, 2000

By L. K. Walker, G. A. Kosick, P. D. Young

"MillEX is an information management system designed by mineral processors for mineral processors. The system utilizes ""cutting edge"" software technology to gather and store all automatically and manually recorded data from the plant operation and laboratories. This data is delivered to the desk of superintendents, metallurgists, technicians and managers, and permits the user to query, correlate, graph, report and present this data in minutes. In the past this task would have taken days and even weeks of tedious work to complete.MillEX allows the engineer/analyst to quickly develop a very thorough understanding of the complex relationships of process variables and equipment that exist in the plant, and their effect on product quality and quantity. The time and resources that are currently wasted on duplicating data entry will be an effort of the past.This paper describes the structure of MillEX and how it conforms to the needs of mineral processing personnel.INTRODUCTIONPicture a personal computer on your desk which will carry out the following commands:1. Plot a graph over the last six months, using weekly averages, of percent minus 200 mesh material in the primary cyclone overflow.2. Overlay this graph with a graph of concentrate grade versus recovery over the same time period.3. Retrieve a prior month end report, update all operating supplies tables and metallurgical performance with this months data, and embed the graphs created above.4. Edit text and print the current month end report. This is only one example of the type of power MillEX isbringing to the mineral processing industry."

Jan 1, 1992

By B. R. Broekman, K. J. R. Ford

Over the last decade significant development and use has been made of a simulation model that describes the HCFeMn smelting operations in Assmang Ltd. This spreadsheet based, semi-empirical, predictive model is derived from data from the submerged arc furnaces at Assmang?s Cato Ridge, KwaZulu-Natal smelter site. Departures from the empirical base case mass balance due to changes in the ores, reductant feeds and operating parameters are accounted for by use of fundamental relationships and heuristic type ratios which are applied in an iterative manner in the model. The model performs a sequential set of calculations to iteratively converge on a fully consistent mass and energy balance solution, which predicts Mn alloy and slag output masses and compositions for a given set of feeds. 440 MWh per operating day is used as the basis of energy input. The paper describes the key model components, assumptions made and calculation approach. Added to the mass and energy balance is a cost and revenue balance, which allows prediction of the economic performance for each simulation. Substantial use of the model has been made in simulating the performance of the current Assmang HCFeMn furnaces for both smelter investigations and future production planning. The model has also been a valuable tool in the strategic analysis of the use of future Mn ores and has formed the vital link between mine ore grades (metal and slag elements) and the expected alloy output, grade and profitability. Additionally, the model has been used in benchmarking exercises to predict other Mn smelting operations with remarkable accuracy. The paper highlights some aspects of the approaches taken in using the model to benchmark Assmang?s own furnace performance and cost competitiveness with other producers. For Assmang the development and application of this modelling technology has led to transformation in understanding of the Assmang HCFeMn furnace operations and increased awareness of the potential of its Mn ore bodies.

Jan 1, 2004

By Frank G. Wickert

One key to maintaining successful mining operations in today?s global economy is in having the ability to access real-time machine operating data ([1] G. Brown, B. Ebacher, W. Koellner,2000)([2] Brochure of Siemens E&A, Order Number 141000-1). With recent and ongoing advances in mining equipment systems it is imperative that mine managers have full knowledge of the status of their equipment at any given point in time. This knowledge is critical to ensuring that the productivity of each and every machine is maximized. Knowledge of machine status is only the first step, however, in controlling and optimizing a piece of mining equipment. Computer based diagnostic systems, traditionally offered on mining equipment, have provided a link for collecting data and trouble-shooting problems as they occur. One problem existed, though, that those systems stopped short of providing full drive systems access. A maintenance technician could see the data but to make critical adjustments or make repairs the technician needed to be on the machine. In extreme cases the machine would be down until OEM assistance could reach the mine site. The key then to reducing down-time and maximizing machine productivity was creating a system that could not only monitor drive systems but also provide remote access to those systems. Essentially a link needed to be created through which a technician could gain drive access remotely then make adjustments or repairs without being on the piece of equipment. This paper will introduce AccessDirectTM, a new remote diagnostic system for Bucyrus mining shovels and draglines. AccessDirectTM combines all three important elements of remote diagnostics: ? Vital Signs and Production Monitoring (SiRAS-M) ? Automatic analysis (SiRAS-A) of faults, and tracking of trends for preventive and reliability centered maintenance , and ? Fast, direct Intervention (SiRAS ? I) for troubleshooting support, repairs, and system optimization.

May 1, 2002

By Clarence R. Zink

A problem has always existed in deep and fast drilling situations such as coal overburden drilling, or when drilling with a tight annulus, such as 9 7/8" bits and 8 5/8" pipe. This problem is the difficulty experienced by blasthole bit and blasthole drill rig manufacturers to attain large jumps in bit and drill rig productivity through bit and rig design, when drilling in these specific situations. In other drilling situations, these large jumps in productivity have been easily attained.

Jan 1, 1998

By E. Pezennec

A voluntary comprehensive environmental Risk Assessment was launched at the end of 2004 by the International Chromium Development Association. The completion is scheduled for mid 2006.EURAS, a leading environmental consultancy, was commissioned for this project, as this firm wrote in particular the Metals Environmental Risk Assessment Guidelines, the reference document for the metals and metals compounds, in particular for the forthcoming European new Chemical Policy and the Globally Harmonized System for the Classification and Labelling of Chemicals (GHS). This project follows a stepwise approach, comprising 3 distinct steps: - Initial Risk Assessment: compilation, evaluation of the existing effects and exposure data for chromium III compounds and chromium metal. This information will be used for the compilation of an initial Risk Assessment Report. - Data gap analysis: which type of additional effects data should be collected and/or which exposure scenarios merit a more detailed targeted risk assessment? Recommendations and/or suggestions for further research will be formulated. - Road map: prioritization and ranking of the different proposed research programs. The presentation will mainly focus on the results and recommendations of the initial environmental Risk Assessment from an International perspective and not from an European point of view. - Hazard assessment ? definition of the Predicted Non effect Concentration (PNEC) for each environmental compartment (water, sediment, soil) - Exposure assessment ? definition of the Predicted Environmental Concentrations (PEC) for each environ-mental compartment - Comparison of the local PEC with PNEC for the chromium III compounds and chromium metal EU industry sectors covered in the project: mining of chromite, metallurgical production of chromium metal, chromium containing alloys production, production of trivalent chromium chemicals and the main applications (pigments, leather tanning, etc..). The current status on the environmental Classification and Ranking for chromium III compounds, Chromium metal and its alloys in the GHS will also be covered.

Jan 1, 2007

By Reda M. Bakeer

"An approach slab is the roadway segment that immediately follows a bridge intended to provide a smooth transition between the two elements. Some approach slabs have developed rough rideability with time due to differential settlement between the roadway embankment and the bridge. Soils in south Louisiana are generally poor and highly compressible and, therefore, pile-supported approach slabs were occasionally used. Timber piles of variable lengths are driven into the soft soils where no appreciable toe support exists. This resulted in the soils both supporting loads through shaft resistance and yet experiencing long-term consolidation settlement. Field testing and review of the records of over 120 approach slabs constructed in south Louisiana yielded the conclusion that their performance is primarily governed by negative skin friction (downdrag) imposed on the relatively short timber piles. A software (TU-DRAG) was developed to evaluate the deflection profile of a pile-supported approach slab based on its geometry and conditions of the underlying soils. It evaluates the effect of dragload considering the number and spacing of the piles at each transverse row and their variable lengths along the approach slab. TU-DRAG was utilized in the design of two transportation related projects which have been in service for more than 10 years.INTRODUCTIONThe problem of differential settlement at bridge approaches or “the bump at the bridge” has been recognized for many years. Research studies (1986, 1989, 1997, 2009 and 2013) by the Transportation Research Board (TRB) and the Federal Highway Administration (FHWA) provided comprehensive evaluations of the performance of bridge approach slabs by assessing their field conditions and construction and maintenance records. Various states have also performed their own studies to investigate the performance of bridge approach slabs. The studies considered various types of structures including soil- and pile-supported approach slabs, integral bridge abutments and open-end abutments. Recommendations were provided for the design of new structures and for maintaining and repairing existing structures. Guidelines were offered regarding tolerable movements of bridges and their foundations based on measurements of vertical and horizontal movements of 580 bridges Moulton (1986). Vertical and horizontal movements greater than 102 mm (4 inches) and 51 mm (2 inches), respectively, were considered intolerable. Tolerable limits for angular distortion (differential settlement to span length) were suggested to be 1/250 and 1/200 for continuous and simple spans, respectively. It was reported that a differential settlement greater than 13 mm (0.5 inch) at the bridge interface would be sufficient to constitute a “bump” requiring mitigation."

Jan 1, 2017