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By Ludwig Hermann

"Phosphorus is required by every cell of living organisms and essential for plant growth. It is a non-renewable resource that must be mined from natural deposits, going gradually into depletion. Abundant secondary resources are available in sewage sludge and meat and bone meal, with the highest exploitable P concentrations in ashes that remain from their widely used combustion with energy recovery. ASH DEC has successfully removed heavy metals and transformed sewage sludge ash into a marketable P fertilizer by application of a thermo-chemical treatment process. Pilot scale investigations in which ash was treated proved that generally heavy metal limits required by fertilizer legislation can be attained. To achieve a high P availability for crops – an essential fertilizer quality feature – was a more challenging R&D task. Our presentation demonstrates the scientific approach and R&D results that lead from assessment of market requirements to licensed products.IntroductionPhosphorus (P) is required by every cell of living organisms. It is one of the major elements for plant nutrition and therefore essential for crop production. P supply in plant nutrition depends entirely on external inputs into soils [1]. This is achieved by P-fertilizers deriving from rock phosphate deposits that are gradually going into depletion. Serious prognoses anticipate that rock phosphate will be the first low running resource in the world [2]. In the EU, last year 2.530 kt of phosphorus (P2O5 in fertilizers) was consumed and only 313 kt (P2O5 in rock phosphate) was mined. Since 2007, rock phosphate prices have increased by 500% because of a tight supply situation [3].For these reasons, P recycling is becoming an increasingly important issue. Suitable secondary raw materials with regard to their high P-content and abundance are sewage sludge and meat and bone meal. In the EU 989 kt P2O5 are accumulated annually in theses materials, of which 632 kt P2O5 are permanently lost to landfills and other forms of disposal. The main reasons for their limited recycling are concerns on heavy metal contents and organic pollutants that may incite health hazards. As an additional shortcoming, the availability of P from these materials to plants is poor and storage and transportation are problematic issues [4, 5]."

Jan 1, 2008

By S. A. Hovanessian

The method of characteristics which reduces the Buckley-Leverett mnlineur, partial differential equation to two first-order, linear differential equations is applied to the solution of a waterffood recovery problem for multiple lines of producing wells and one line of injection wells. The application of the method is described by a numerical example, and a brief theoretical background is given. From the results of this study, it is concluded that the cumulative water injected and oil produced are the same for single and multiple sets of producing wells. INTRODUCTION In this paper, the method of characteristics is applied to the solution of a waterflood recovery problem with multiple lines of producing wells and one line of injection wells. The application of the method to this type of recovery problem considerably simplifies the procedure of obtaining a numerical solution. It differs from the method described by Kern1 because it eliminates the need for integration in obtaining saturation fronts. In addition, the saturation history at any location within the field is obtained from a single diagram (time vs distance with saturation as a parameter)'. The paper includes a brief theory of the method of characteristics and its application to the solution of oil recovery problems. A numerical example is worked out, and the cumulative oil recovery-vs-time curve for a system with multiple sets of producing wells is obtained. This curve is then compared with the recovery curve of a system with only one set of producing wells. From this study, it is concluded that the cumulative water injected and oil produced are the same for single and multiple lines of producing wells. However, the recovery time is considerably longer for multiple sets of producing wells.

By Lewis Finch

Oil and .gas reservoirs exist under pressure within the pore spaces of rock structures or traps. Wells are drilled to produce these reservoirs. Under primary operation, the natural energy of expanding fluids in and adjacent to the reservoir forces or drives oil and gas to the wells. There are three basic sources of energy: dissolved gas, water, and gas cap. Typical recovery by primary methods is only 10 to 25 per cent of the oil in place for the dissolved gas drive but is generally higher for the others. Secondary recovery involves the injection of water or gas to supplement natural energy, thereby increasing recovery over that obtainable by primary operation alone. In many cases ultimate recovery with secondary methods is 1.2 to 2.0 times the expected primary recovery. The type programme adaptable in a field depends on its 'primary performance and on certain reservoir characteristics. In the United States, application of secondary recovery methods is becoming increasingly important. About 22 per cent of United States oil production now comes from fields in which injection projects are operating. In 1953, nearly 1.4 million barrels of oil daily came from such fields, more than double the amount in the early 40's. Ultimate primary recovery from known pools is estimated at roughly 73 billion barrels. Secondary recovery projects already in operation will increase this to almost 80 billion, an increase of almost 10 per cent. Unitized secondary recovery projects have been very successful. From unitized projects alone, industry reserves of oil in the United States have been increased by 3 1/2 billion barrels. In Canada, secondary recovery has not been so wide spread mainly because D-3 reef reservoirs which have held the major reserves are under water drive. However, appreciable amounts of water are being injected in the Redwater D-3, Leduc D-2 and Joarcum Viking reservoirs, and gas in the Golden Spike D-3. In both countries, possible achievements in increased recovery through secondary recovery methods now in use and by new ones which may be developed through research and field trial are a challenge to the scientist and the industry.

Jan 1, 1956

By James Douglas

THOUGH liberality is not supposed to be a prominent trait of the Scottish character, Canada owes to a Scotchman, Sir Wm. Macdonald, more than to any other of its people, not only wise ideas, but pecuniary help towards extending education: and another Scotchman, in New York, has sumptuously housed under one roof three branches of the engineering fraternity, of which we are one. Having thus created us members of the same family-for the metaphorical meaning of house and kinship is identical-Mr. Carnegie expresses more emphatically than even he could in words, that, by affording facilities for closest intercourse, he in¬vites the mechanical, electrical and mining engineers to par¬ticipate in the freest interchange of idea and experience, and to correlate and combine the results of their studies and activi¬ties; and, being members of the same household, to banish re¬serve and secrecy. And now we, the members of the - American Institute of Mining Engineers, meet as though we were at home in a neighboring country. For whether we meet in Canada, in England, or elsewhere, the Institute is always received as though no political or geographical divisions separated its members from those of congenial associations in the land of its host. In truth, the title which we have assumed claims for the sphere of our activities the whole American continent, regardless of such trifling details as boundary-lines. The fact that we meet to communicate each other's experience, to discuss our difficulties, and to seek each other's aid in solving the intricate problems that so often present themselves in the course of our profes¬sional life, is an acknowledgment of our individual helpless¬ness; and therefore an argument for united effort. But no effort can be of any value if there is an underlying suspicion

Jan 9, 1907

By John Johnston

ONLY two of the Institute's 26 Local Sections were unrepresented at the delegates' three sessions, held on Monday morning and afternoon and Thursday afternoon of the annual meeting. The Philadelphia and Wyoming Sections alone sent no delegates. In all, seven hours were spent most profitably in reviewing the work done by the Institute at headquarters and in the field, comparing ideas and practices in varied activities, and in establishing personal contacts. Cordiality and the co¬operative spirit marked the meeting and apparently no one had any serious grievances to air. Four motions were introduced and unanimously passed. The first, which was introduced by B. L. Sackett, was a recommendation by the delegates that a national committee be appointed to cooperate with Local Sections in the matter of student activities, to promote Institute welfare. It was agreed that this recommendation be made simultaneously to the Board of Directors and to the Mineral Industry Education Division. A subsequent resolution by A. M. Smith was passed asking that a part of the duties of this committee be to secure the opinions of Local Sections as to the most desirable methods of interesting students in the preparation of technical papers, by giving prizes or otherwise, and to report their findings at the Section Delegates' meeting next year.

Jan 1, 1933

By AIME AIME

NO FEATURE of the annual meeting is considered more important at Institute headquarters than the assembly of delegates from the various local sections and divisions. There the president of the Institute and other officials may learn at first hand what the members are thinking and doing in every part of the country, and the delegates, in turn, may find that head- quarters is not a group of more or less cold-blooded New Yorkers whose primary function is to send out annual bills for $15. This year, the section and division delegates required three sessions to thresh out the matters of common interest: Monday morning and afternoon and Thursday afternoon. They were also guests of the Institute at the Directors' dinner on Tuesday night, and at the Directors' meeting afterward.

Jan 1, 1932

By Louis Doremus Huntoon

HAVE been asked many times by financial men in New York as to the best way of securing an interest or control of a gold mine in Canada. It must be understood at the start that prospectors and early owners will not sell a 100 per cent interest. They not only retain from 10 to 25 per cent interest, depending upon the work done, but usually demand more or less cash to reimburse them for expenses. These conditions are accepted by Canadian capital and operating mines looking for new properties. The winter is not a hindrance to work but may be of great advantage. The overburden of soil and gravel is generally wet and most difficult to trench in the summer time especially if at all deep. The snow also permits easy transportation of freight. Properties distant from rail transport all of their machinery and supplies during the winter months.

Jan 1, 1933

By Masaru Sakakibara, Ngo Tuan Anh, Mitsuo Nozu

"In the southern region of Vietnam and the southern United States, numbers of Deep Mixing (DM) columns have been installed to increase the stability of slopes and mitigate ground settlement. However, in some cases, there were some quality problems for in-situ cement mixing such as inclusion of unmixed lumps. According to the investigations by the X-ray diffraction analyses, electrical conductivity (EC) test, and careful observations of in-situ mixing quality, it has been observed that the existence of expansive soil and its high EC value cause the insufficient in-situ mixing. The countermeasures to address these problems have been taken.INTRODUCTIONIn South Vietnam, under the guidance of numbers of references and standards (Miki, 1998, JGS, 2000, Kitazume et.al., 2001, BS 2005), Deep Mixing (DM) has been used in recent years for soft clay improvement to increase the stability of slopes and to reduce consolidation settlement (Nozu 2005, Tung et.al., 2009, S. T. G. Peng et.al, 2009). However, at the initial phase of the DM operation, the authors have encountered some unusual phenomena such as (1) lower strength and inclusion of unmixed lumps (Figure 1), (2) less amount of up-heaved soil, and (3) sticking of large lumps of clay to the mixing blades. In regard to the above (3), Photo 1 shows one of the countermeasures against the sticking. By means of the placement of additional plates, the stuck clay has been reduced significantly.Subsequently, we have noticed that the quality of DM columns has not been so good, which meant that there have been some unmixed lumps in the column despite high cement dosage such as more than 300kg/m3. The authors also have encountered the similar incidents in Vietnam and United States during the deep soil mixing work. For example, Photo 2 is the core samples taken from the DM test column in northern Vietnam adopting cement injection during penetration (CIDP) procedure. To solve this problem, various tests and investigations have been performed so far (Nozu 2010, 2012)."

Jan 1, 2015

By Stefan Mede

Robot Supported Moulding—this is the name of Herrenknecht Formwork’s entry to the world of automated segment production. What had been considered impossible for a long time, has been achieved by Herrenknecht experts together with the Swiss company Marti AG: unmanned segment production on the working line. The moulds open and close autonomously with the help of a hydraulic system. A robot cleans and greases the moulds at one work station and inserts the injection sockets at another. The next step will include further automation and digital networking of all processes from production to installation in the tunnel.

Jun 13, 2021

By Lori Bassman, Cassandra George, Cullen McMahon, Md. Zakaria Quadir, Michael Ferry

"Complete and accurate analysis of subgrain microstructural features must include three-dimensional information. Three-dimensional electron backscatter diffraction (EBSD) data can be used to characterize these features; however their boundaries first must be determined. This cannot be accomplished simply with pixel-to-pixel misorientation thresholding because many of the boundaries are gradual transitions in crystallographic orientation. Fast Multiscale Clustering (FMC) is an established image processing technique that we have combined with quaternion representation of orientation to segment this kind of data. Segmentation algorithms often have issues handling images with both distinct and subtle boundaries. Our implementation of FMC addresses this by using a novel distance function and statistical analysis to take into account the variance in orientation of each feature. Although FMC was originally a twodimensional image processing algorithm it can be generalized to analyze threedimensional data sets. As an example, a segmentation of microbands in cold-rolled aluminum is presented.IntroductionThree-dimensional electron backscatter diffraction (3D-EBSD) is a method for mapping the local crystallographic orientations of points in a volume. The technique uses a dual beam platform consisting of a focused ion beam (FIB) and SEM with EBSD, where FIB is used for serial sectioning and EBSD for orientation mapping of 2D slices. These 2D slices may then be stacked to create a 3D volumetric data set.Typical uses of such a data set include characterizing the geometries and crystallographic orientations of surfaces between structures in 3D [1-5]. This involves identifying boundaries accurately, either in 2D slices with subsequent 3D reconstruction (as illustrated in Figure 1) or in the 3D data set. All such data sets present the challenges of i) aligning data slices to correct for instrument drift, ii) identifying relevant boundaries, and iii) implementing appropriate smoothing or interpolation algorithms. The focus of this paper is boundary identification."

Jan 1, 2011

A fast, easy, and inexpensive method of determining the consolidation of overburden in surface mining operations through seismic analysis has been developed. The method involves use of a refraction seismograph which measures overall consolidation of subsurface materials, including such factors as rock hardness, stratification or lamination, fracturing or jointing, and the degree of weathering or decomposition. It also is possible to determine the thickness of various layers of subsurface materials to depths exceeding 100 ft.

Jan 8, 1959

By Don Deardorff, Ke Yang, Yingcai Han, Ken Sorensen, Robert Kruger, Mark Petersen, Diane Fiorelli, Larry Goldfarb, Kathryn Petek, Kwabena Ofori-Awuah

Design of deep foundations for lateral loads requires an understanding of soil-foundation-structure response during loading. Lateral loads on a deep foundation (piles) could be due to earthquakes, winds, waves, and/or machine vibrations. Over the years, analysis of response of piles due to lateral loads evolved from closed-form solutions to p-y methods to strain wedge to finite element/finite difference modeling. Although analysis of lateral response of piles and shafts is routinely performed, there is no single guidance document and/or standard for design and testing. Several different analytical methods are available for the analysis, and the resulting design can result in significantly different responses which can create confusion. This is especially true for analyzing and designing piles in potentially liquefiable soils with lateral spread issues under seismic conditions.This guidance document is intended to assist geotechnical engineers, pile designers, and contractors in analysis, design, and testing of piles and drilled shafts for lateral loads. This document discusses the background of different analytical and testing procedures and presents the recommended methods for analysis, design and testing of piles for lateral loads.Chapter 1 defines the different kinds of lateral loads to which a single pile or pile group may be subjected. This first chapter also presents different types of piles used to resist lateral loads.Chapter 2 discusses geotechnical issues related to lateral pile design such as liquefaction and lateral spreading and other non-seismic issues. Also addressed in Chapter 2 is geotechnical site characterization (as related to lateral loads) in terms of site investigation, in-situ testing, geophysical testing, laboratory testing, and estimation of soil/rock properties.Chapter 3 discusses the background and available analytical methods and tools for the analysis and design of single piles and drilled shafts. Several methods of analyses from closed-form elastic solutions to the finite element/finite difference solutions and their applicability are discussed. Available commercial computer software packages for analyzing single piles and drilled shafts are also presented.Chapter 4 expands the discussion of single piles and drilled shafts into the analysis and design of pile groups. In addition, group effects, resistance of pile caps, results of previous experimental and analytical studies, and available analysis tools and software for pile groups are discussed.Chapter 5 presents the issue of lateral resistance of piles and drilled shafts as discussed in different national and international building and non-building codes. A summary of extensive research on several codes are presented to facilitate the compliance with different codes.Chapter 6 discusses structural design issues of individual piles and drilled shafts such as depth of fixity.Chapter 7 discusses soil structure interaction issues related to kinematic and inertial effects due to seismic loading and available methods of analyses.Chapter 8 discusses and presents the typical procedures for the lateral load testing of piles. This guideline was developed as an aid to the practicing engineer in providing information, direction and commentary on the lateral design of deep foundations. Although all reasonable effort has been made to accurately compile the material and information contained herein, no warranty is made with regard to any such material or information and the Deep Foundation Institute assumes no responsibility for any possible errors or any direct or indirect result of the use of any such material or information. It is not intended that this document address every factor affecting lateral design for every situation. Therefore it is the responsibility of the person utilizing information from this document to confirm that it is appropriate and correct for their situation as well as to understand and properly apply

Jan 1, 2012

By Bradley J. Fleming

Although soil improvement and its application to deep foundations is gaining popularity in the engineering community, this technique is not widely used in high seismic regions due to lack of fundamental understanding of both the behavior of improved soils under high-strain cyclic loading and the interactions between the pile, improved soil, and unimproved soil. This paper describes part of an ongoing Network for Earthquake Engineering Simulation (NEES) project, where two identical full-scale steel pipe piles were driven at a soft clay site in Oklahoma. The soil surrounding one of these piles was improved using the cement deep soil mixing technique in order to enhance its lateral load behavior. Both piles were tested for seismic resistance using dynamic and quasi-static loading. The pile in unimproved soil provided larger displacements with limited lateral force resistance. This pile was subjected to lateral displacements of up to 400 mm, but experienced minimum inelastic actions. On the other hand, the pile in improved soil reached its lateral capacity at a displacement of 100 mm, at which point the critical region at the base of the pile just above the improved ground experienced buckling and fractured due to low cycle fatigue. Compared to the pile in unimproved soil, the improved ground increased the system strength by 42%. Although the soil was improved over 2900 mm, the effective improvement depth was approximately 1300 mm below the ground surface. In this paper, it is demonstrated that the effects of block type soil improvement of limited horizontal and vertical dimensions can be described using a simplified theoretical approach involving a modification to the well-known p-y representation of soil response. An example using this method is presented and shown to give adequate support to a standard 12-inch diameter steel pipe pile embedded in soft soil.

By Jin-Wei Huang, Bradley J. Fleming, Sri Sritharan

"Although soil improvement and its application to deep foundations is gaining popularity in the engineering community, this technique is not widely used in high seismic regions due to lack of fundamental understanding of both the behavior of improved soils under high-strain cyclic loading and the interactions between the pile, improved soil, and unimproved soil. This paper describes part of an ongoing Network for Earthquake Engineering Simulation (NEES) project, where two identical full-scale steel pipe piles were driven at a soft clay site in Oklahoma. The soil surrounding one of these piles was improved using the cement deep soil mixing technique in order to enhance its lateral load behavior. Both piles were tested for seismic resistance using dynamic and quasi-static loading.The pile in unimproved soil provided larger displacements with limited lateral force resistance. This pile was subjected to lateral displacements of up to 400 mm, but experienced minimum inelastic actions. On the other hand, the pile in improved soil reached its lateral capacity at a displacement of 100 mm, at which point the critical region at the base of the pile just above the improved ground experienced buckling and fractured due to low cycle fatigue. Compared to the pile in unimproved soil, the improved ground increased the system strength by 42%. Although the soil was improved over 2900 mm, the effective improvement depth was approximately 1300 mm below the ground surface.In this paper, it is demonstrated that the effects of block type soil improvement of limited horizontal and vertical dimensions can be described using a simplified theoretical approach involving a modification to the well-known p-y representation of soil response. An example using this method is presented and shown to give adequate support to a standard 12-inch diameter steel pipe pile embedded in soft soil,IntroductionPilings are the preferred foundation support for many civil engineering structures including highway bridges, railroad bridges, and port wharves. These structures and their foundations are subjected to forces created by earthquakes, wind, waves, water current, vessel impact, ice, and gravity. All loads applied to the superstructure must be transmitted to the foundation where they are resisted by the surrounding soil. With significant lateral loads, use of pile foundations may be the only solution to transmit large structural loads to competent soils. Piles supported by competent soils are relatively easy to design and costs are often attainable. However, thick layers of weak soils such as soft clays are widespread in high seismic areas (e.g., San Francisco, southern Nevada, Washington, Eastern Missouri, and Arkansas), exacerbating design challenges. Soft clays reduce the lateral resistance of the pile-soil system, making the pile foundation less cost effective. In this case, the current design practice is to use an increased number of larger diameter piles, which is a costly alternative (see SDC, Caltrans 2010). An innovative and more cost-efficient solution to this problem is to improve the soil within a short depth surrounding the foundation, thereby increasing its lateral stiffness. Some well-known methods for improving soil include deep soil mixing, stone columns, and simple soft soil replacement with select granular material."

Jan 1, 2017

By Matthew Price, Laura Brown, Atulya Verma, Samantha Espley

Burst-prone conditions are a significant hazard in deep hardrock mines, elevating the risk to excavation stability and, more importantly, to worker safety. As mining progresses deeper, induced stress changes may trigger the initiation of rock failure processes which can be detected and recorded as mine seismicity. The implementation of seismic monitoring and routine seismic data analyses enables mine seismicity to be quantified spatially, temporally and on scale. The ability to quantify and characterize mine seismicity offers the opportunity to gauge seismic hazard, identifying high risk zones for mitigation against burst-prone excavation failure. Over the last decade, the Mines Technical Services (MTS) group at Vale Canada Limited’s Garson Mine assessed seismic hazard with the objective of assigning practical mitigating controls to zones identified as having a high rockburst potential. Initially, seismic hazard was computed using the Seismic Excavation Hazard Mapping (SEHM) software developed by the Mining Innovation Rehabilitation and Applied Research Corporation (MIRARCO) at Laurentian University, Canada. More recently, Vale Sudbury Operations partnered with the Australian Centre for Geomechanics and the University of Western Australia’s mXrap consortium. Through the consortium partnership, MTS at Garson Mine implemented the mXrap seismic data analyses platform, including the grid-based seismic hazard assessment tool. Building on 10 years of seismic hazard assessment experience at Vale Garson Mine, this paper summarizes a comprehensive case study, comparing the two tools (SHEM and mXrap) used at Garson Mine to assess, quantify, and represent seismic hazard. Subsequently, results of the Garson Mine comparative seismic hazard study will be discussed, emphasizing the need for an all-inclusive hazard assessment tool, focused on delivering practical mitigating controls that further enhance the overall safety of seismically active underground mines.

Apr 26, 2022

Caving of the second lift of the E26 orebody at Northparkes Mines was monitored with a comprehensive package of instrumentation, including an ISS seismic monitoring system. Seismicity was collected by an array of 19 triaxial accelerometers and 9 uniaxial geophones, giving a high quality seismic data set. The seismic response to block caving at Northparkes has been divided into two papers. The first paper focuses on the seismicity during undercutting. The second paper deals primarily with the seismicity during cave propagation during initial cave production. In this paper, traditional seismic monitoring concepts are applied to seismicity during cave mining. More than 40 000 seismic events were recorded during cave undercutting between February and January 2004. Events up to local magnitude +1.3 were recorded near the mine during undercutting, with event rates of up to 500 per day. Analysis of frequency-magnitude distributions, S-wave to P-wave energy, and temporal variations in event magnitude all gave insight into the seismicity recorded. In addition, a new technique, called apparent stress time history, was shown to be sensitive to stress change from undercut blasting, and useful to identify significant periods during cave development. A significant difference was identified between the cave back location and the halo of seismic events above the cave. Throughout the undercutting, the a seismic zone of loosening was typically 50 to 70 metres in vertical thickness. Based on the seismicity, a stress driven rock mass failure model is proposed. Early in the undercutting, seismicity and movements in the seismogenic zone were directly triggered by stress change from undercutting. Towards the end of undercutting, seismicity was virtually uncorrelated with undercut blasting, and likely due to the onset of cave initiation.

Jan 1, 2008

By L. Trivino

Blast-induced damage criterion based on the peak particle velocity has worked reasonably well for estimating building damage. However, the same criterion cannot be used to estimate damage to rock and mine structures such as shaft and tunnel walls. It does not take into account the nature of seismic radiation pattern in the near-field, which is very different than what is obtained at far-off distances. To investigate this phenomenon, a systematic study has been carried out involving single-hole blasts and normal production blasts, with explosive source ranging from nearly point source charges to standard borehole sizes (6-7 m long explosive column), with charge weight varying from 0.5 kg to 30 kg. In the near-field, it is shown that, both P-wave and S-wave take a dominant position compared to the mainly surface waves measured in the far-field. These are shown to depend strongly not only on the length of the explosive column but also the way it is initiated in the borehole (i.e. direct vs. reverse initiation in the borehole) with respect to the target location. The seismic radiation patterns were recorded by high-frequency triaxial accelerometer stations grouted in the rock mass. This study describes the nature of seismic radiation in the near-field from long and short charges, the role of initiation direction and their effect on frequency with respect to sensor locations or target area of interest, and their implication in prediction of blast-induced damage in the near field.

Jan 1, 2009

By David Pierce

The Port of Seattle, one of the largest on the west coast of North America, made a strong statement regarding their support for reusing existing structures when a decision was made to rehabilitate Pier 69, on Seattle's downtown waterfront, for their new headquarters. Because of its age and location, the pier provided an unusual challenge to the Port and its consultants. The Port hired Peratrovich, Nottingham, and Drage Inc. to design the seismic strengthening of the pier itself. To remedy the lack of seismic resistance in the 70-year-old pier, PN&D designed a new steel-pipe-pile supported concrete apron next to it. The structure relied on a development by PN&D, the "spin-fin pile", to achieve the tension capacities required of the batter piles. The construction of this apron was completed in October of 1991. Another team of consultants performed the superstructure renovation design, which is now under construction.

Jan 1, 1992

By Cleland N. Conwell

APPLICATION of seismic methods to the location of buried channels in placer mining is fairly common knowledge, yet some of the facets of seismic refraction surveys have remained obscure in their application to mining. This description by a member of the U. S. Bureau of Reclamation team investigating bedrock at the Oso Dam site, may offer a lead to wider application of the method for bedrock determinations in engineering of mine and mill plants, tailing disposal, and water supply. It may also offer assistance in planning geological exploration in areas covered by overburden. Pertinent, and perhaps more than passingly significant, is that the seismic survey of the Oso dam site started at noon and was completed the afternoon of the next day. Location Oso dam site is on the Navajo River, Archuleta, County, Colo., 30 miles southeast of Pagosa Springs, Colo., 10 miles northwest of Chama, N. M. Bedrock at the proposed dam site is Mesa Verde Formation, Cretaceous age sandstone. The nearest good sandstone exposure is about 5/8 of a mile upstream from the location of the seismic determinations. The material above bedrock is sand and gravel with sandy loam soil covering benches above the river. The site appeared favorable, after a geologic and topographic reconnaissance, but overburden thickness was unknown. Exploratory drilling was not contemplated in the near future so a short seismic investigation was selected as the most suitable method of determining depth to bedrock. Field Procedure Geophysically, a seismic depth investigation is simply the measurement of depth from ground surface to the top of a layer which transmits seismic waves at a higher velocity. In this case the high-velocity seismic layer tentatively correlates with the Mesa Verde sandstone. Field procedure required a seismic explorationline or "spread" with 12 geophones set at measured intervals. Explosive charges were buried at few feet in the ground and detonated at shotpoints near the ends of the spread, and at intermediate points. The time of travel of the seismic waves from the shotpoints through the ground to each of the geophones along the spread was measured and recorded photographically with equipment housed in a field truck. The seismograph on each spread provided a time-travel graph. From it were computed the speed of seismic waves in various layers below the surface and depth to each different seismic layer below the shotpoint. In the case of the Oso dam site it was possible, in addition, to determine the depths below certain geophones, because there were only two seismic layers involved. Interpretation In seismic exploration waves are refracted from the top of layers which often correspond to divisions between subsurface formations. When drill holes are available the geologic logs offer a means of correlating stratigraphic breaks with seismic layers, improving reliability of seismic interpretation in terms of depth to bedrock or other geologic terms. There were no drill holes available in the case of the work at the Oso dam site. Geologic conditions appeared favorable for seismic technique because of excellent contrast in seismic wave velocity between the overburden and the Mesa Verde formation. The upper layer had a velocity of approximately 2500 fps and was interpreted as overburden, the lower layer had a velocity of approximately 9000 fps and was assumed to be the sandstone. These velocities are of the order expected in these materials. The seismographs obtained at the Oso dam site were excellent. The energy from the shot came in strongly at each geophone, giving an easily read record. Time-travel graphs plotted from wave arrival times were uniform and made interpretation comparatively easy. In Spreads 1 and 2 near the river the lower velocity layer was 12 to 15 ft deep. For the spreads on higher ground, or the bench south of the river, it was from 15 to 29 ft deep.

Jan 1, 1952

By Bruce B. Redpath, Doug Crice, Rob Huggins

Over the last decade, instrumentation has been developed that allows the application of seismic reflection methods to groundwater and engineering problems. At the Geological Survey of Canada, we have been developing and testing shallow reflection techniques for mapping the bedrock topography and structure within the overburden. We have attempted to develop methods which can be implemented with a minimum investment in equipment and computing capabilities. The data are recorded on a l&channel engineering seismograph, using a single high-frequency geophone per channel, and a hammer or in-hole shotgun (“Buffalo gun”) as the seismic source. Processing and display of the data can be accomplished on an Apple II+ or IIe microcomputer and an Epson wide-track dot-matrix printer.

Jan 1, 1991