Search Documents

By M. Javier

In business mining, dilution is the result of the operating parameters that occur too often and cause serious consequences to mine performance, questioning TO WHOM BENEFITS DILUTION. Mining persists in changing perception of real meaning of dilution. The lack of interrelation between mineral processes and nature compromises the understanding of dilution; this absence of interrelation occurs due to the misinterpretation of nature, otherwise, Geomimic could be helpful to filling the gap of misinformation. NATURE provides LIMITED metals in low content deposits; it is a challenge to obtain them. Nature never considers dilution. Furthermore, though dilution is a human concept, dilution is accepted and promoted. Reality of dilution is in its errors accumulation that translates into technology level or status applied in nature. It is doubtful that dilution can continue surviving if it is ?meaningless?. It will discourse: Is dilution illegal? If the change occurs in the prediction of mining will prevail a different destiny, it is important to touch the cores of the business; otherwise, it would represent repetition of the same ?negative? effects, as usual. Mining defines many losses during the disturbance of nature, from NPV elaboration to the metal recovery to commerce, demanding BETTER DESIGN. This paper introduces and applies MANAGEMENT BY LOSS, as first steps, to limit risks and uncertainties in mining. As result, the management of dilution will be obtainable under mining practices which promotes its character of SUSTAINABILITY.

Feb 23, 2014

By D. W. Gunkle

Processing of various ores and materials in a reducing atmosphere has been done for many years. However, the typical device currently used is a large, often high maintenance, expensive piece of equipment; the rotary kiln. While it is a very reliable and a proven technology, the rotary kiln also has its limitations. It is limited by its ability to process very fine materials without creating a huge dust loss to the air pollution control equipment. This leads us towards the development of an alternate technology; the Gas Suspension System. Gas suspension preheating of various materials has been in commercial use since the early 1950's, but recently has been expanded to include Gas Suspension Reduction. Laboratory experience has proven successful on several materials; Nickel Laterite Fines, Iron Ore Fines, Fluorspar, and Clays. The gas suspension reduction system has many advantages over the conventional reduction kiln when processing fines. They are; lower cost, more fuel efficient, able to process fines, less real estate required, etc.

Jan 1, 1998

By R. P. King

The MODSIM mineral processing plant simulator is used to find optimal combinations of target separation specific gravities in a typical modem coal washing plant. A plant that is set up with these optimal targets can deliver up to 10% more yield at the same ash content as the same plant set up with separation targets chosen by conventional methods. MODSIM is the only simulator currently available that can simulate the liberation of pyrite and other mineral matter during open-and closed-circuit grinding operations. The simulator can therefore be used to assess the benefits of grinding operations in the flowsheet.

Jan 1, 1997

By J. L. Bellanca, L. R. Swanson

DISCLAIMER The findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention. Mention of any company or product does not constitute endorsement by NIOSH. ABSTRACT Proximity detection systems (PDSs) for mobile machines have the potential to decrease injuries and fatalities. Early adopters of the technology have identified some challenges, which presents an opportunity to explore and improve the integration of mobile PDSs in underground coal mines. The current study applied the task-technology fit framework to investigate the fit between mobile PDS technology and mining relative to health and safety, from the perspective of leaders at two coal mines. Quantitative results from the study show that mine leaders evaluated mobile PDS favorably for training and ease of use, system feedback, user authorization and experience, and less favorably for safety, compatibility, task completion, and reliability. Qualitative results reveal specific task, mine, and system characteristics that may have influenced leaders' evaluations. The study includes considerations for safe technology integration. INTRODUCTION Striking, pinning, and crushing accidents related to mobile machines continue to be a major concern in underground coal mining. The National Institute for Occupational Safety and Health (NIOSH) linked 22 of the 75 underground mine fatalities reported between 2011 and 2015 to power haulage [1]. The Mine Safety and Health Administration (MSHA) asserts that proximity detection systems for mobile machines (mobile PDSs) could help to prevent these types of fatal injuries [2]. Mobile PDSs use a collision avoidance technology that allows the mine to establish hazard zones and employ electromagnetic sensors to detect workers equipped with a miner-wearable component (MWC) working near these mining machines. The authors characterize a mobile PDS as an automated technology, because—in line with Lee & See’s [3] definition of automation—a mobile PDS actively “selects data, transforms information, makes decisions, or controls processes” (p. 50). When the system detects workers in the established hazard zones, it issues alerts and slows or stops the mobile machine. Even though a mobile PDS may be a viable and promising safety solution, there are still a number of questions regarding how well this automated technology will fit with mining tasks and conditions. Using a mixed-methods approach, the current study explored factors that influence the fit of mobile PDSs in the underground mining environment.

Jan 1, 2019

By S. G. Malghan

Flotation is the primary method for copper minerals separation from porphyry ores. The need to process difficult-to-float porphyry copper ores presents challenges to engineers and scientists in several areas. This paper is concerned with summarizing generalized problems faced in the processing of porphyry ores and treatment methods to overcome the specific problems. Though some of the problems are interrelated the problems have been classified into three broad catagories. The case studies of some of the successful applications of innovative methods to solve problems related to ore mineralogy, metallurgical aspects of ore treatment and process variables show that quite often the problems are solvable by a judicious choice of flotation variables.

Jan 1, 1984

By Paul D. Tomlingson

The difficult and often harsh working environment of the mining industry can stress both personnel and equipment to the extreme. Often, the unintended consequences of this environment lead to confrontations between departments, as each goes about its tasks of mining, maintaining or supporting these activities. On occasion, the confrontations may result in criticism of other departments for perceived or real sins or omissions. The offended department may not be able to change the circumstances, but can only complain while frustration persists. The most effective solutions are the actions of the mine manager. By establishing mutually supporting roles of each department and specifying conditions for the interactive conduct of maintenance, the mine manager can better assure that the inherent problems of the mining environment are neutralized.

Jan 1, 2011

By W. B. Lambert

A common decision in openpit mining is to determine the extraction sequence of notional three-dimensional production blocks so as to maximize the net present value of the extracted orebody, while adhering to precedence and operational resource constraints. This openpit block sequencing (OPBS) problem is commonly formulated as an integer program, with binary variables representing if and when each block is extracted. In practical applications, the number of blocks can be large and the time horizon can be long; therefore, instances of this problem can be difficult to solve using the exact approach of optimization. The problem is even more challenging to solve when it includes explicit minimum operational resource constraints. Our maximum value feasible pit (MVFP) algorithm generates an initial integer feasible solution for OPBS problems, in which minimum operational resource constraints are strictly enforced. As an exact approach, we present a Tailored Lagrangian Relaxation (TLR), in which the selection of constraints to dualize is guided by information provided by the MVFP algorithm. We present results and graphics to demonstrate the utility of our techniques for instances containing up to 25,000 blocks and 10 time periods.

Jan 1, 2013

By Charles Dumaresq

The management of mine tailings poses a complex range of potential risks, including physical risks, such as the risk of catastrophic failure of a tailings facility and chemical risks such as the risk of long-term leaching of contaminants into the downstream environment. If these risks materialize, they can lead to a wide range of impacts on people and the environment, including human fatalities and severe impacts on downstream ecosystems, and the costs of recovery borne by industry, communities, governments, and society as a whole can be immense. Tailings facility failures in Canada (2014), Brazil (2015 and 2019), South Africa (2022), and in other locations around the world underscore how high the stakes are when mines produce and manage tailings (WISE Uranium Project 2019). Understandably, many people do not trust the mining industry to manage tailings responsibly. As an industry, it is our responsibility to manage tailings in a manner that is responsible and strives to minimize harm associated with tailings management, including effectively managing both the physical and chemical risks associated with tailings. Standards have an important role to play in responsible tailings management by setting expectations for standards of care and providing a means to measure and report on performance. In jurisdictions with strong legal requirements for tailings management, standards play a complementary role, pushing performance improvements in areas that may be difficult or impossible to address in legal requirements. In jurisdictions where legal requirements are lagging, standards may represent the de facto leading practice and may be the primary tool to help ensure responsible tailings management. Implementation of standards can help companies demonstrate that tailings are being responsibly managed and help build trust and credibility. Most importantly though, standards are important tools to help ensure that the risks associated with tailings are reduced, and that remaining risks are effectively managed. However, we must recognize that conformance with standards can have a down-side – the proverbial two-edged sword. Having standards is vital but there is a risk that implementing standards becomes a “box checking” exercise, with ongoing conformance leading to complacency. We must not allow ourselves to fall into the trap of believing that, just because we are complying with applicable standards and laws, we are therefore doing our best, and that “it can’t happen to us.” In addition, if conformance becomes the goal and the standard does not have mechanisms to drive continual improvement, then once the standard is met, there may be no incentive to improve. The point of complying with standards is not to pass the test. The point is to manage tailings responsibly, prevent catastrophic failures, and minimize harm. The point is to do better, because we must do better. To do that, we need to strive not for conformance, but for excellence in tailings management, driven by continual improvement and a quest to do better.

Feb 1, 2025

By S. Frimpong, E. Siami-Irdemoosa, S. R. Dindarloo

"Electric and hydraulic shovels are the dominant loading machinery in surface mining operations. Despite their critical role in production and their high capital and operating costs, no reliable and comprehensive quantitative performance metric is available. In this paper, a stochastic shovel effectiveness (SSE) measure is proposed for the purpose of quantifying the performance effectiveness of these shovels. The SSE is based on the widely used method of overall equipment effectiveness (OEE) in the manufacturing industry. The OEE measures the performance effectiveness of equipment by multiplying its mechanical availability, utilization and production quality. In manufacturing processes, quality rate is the ratio of the total number of products minus the number of defective products – equivalent to the number of acceptable products – to the total number of products. The SSE similarly uses the mechanical-availability and utilization terms, but instead of quality rate it uses a new parameter named bucket rate.The variability or randomness of the input data, that is, availability, utilization and bucket rate, are further incorporated into the SSE, and a final stochastic SSE distribution is derived in the form of a probability density function. One hydraulic and one electric shovel in a surface mining operation were selected to test the validity of the proposed method. The SSE scores for the two shovels, operating continuously for one year, were derived and compared. As with the OEE, the three-parameter SSE method yielded more representative results for overall performance measurement than a single-parameter approach. Using Monte Carlo simulation, a three-parameter Weibull and a normal distribution were derived for quantifying the overall effectiveness of hydraulic and electric shovels, respectively. As a decision aid, the proposed methodology promises to render a more informative tool than traditional metrics for mine equipment maintenance and management."

Jan 1, 2015

By T. A. Lloyd

The use of tank cells over the years has provided a means for low cost, space efficient, extra capacity in existing flotation circuits. In some cases, new plants have selected tank cells as the machine of choice. Typical tank cells use high efficiency impellers for mixing, which results in low power draw. Unfortunately, these mixers have poor aerating characteristics that compromise metallurgical performance. This has all changed with Outokumpu's new flotation concepts. Outokumpu has recently developed the HG or High Grade flotation cell that can provide higher recovery with better selectivity while maintaining the simple operation of conventional cells.

Jan 1, 1993

By Y. J. Son, S. S. Nageshwaraniyer, K. M. Kim

"This paper reports on the development of a simulation-based framework for obtaining optimal blast design parameters for a hard-rock mine. To do this, a conventional medium-sized hard-rock mine was taken as a case study. The mine has two pits containing hard and soft rock types. The proposed framework contains a combination of regression analysis using Excel software by Microsoft and discrete-event simulation using Arena software by Rockwell Automation, applied to construct a model of the material-handling network of the mine. Specifically, blasting parameters are estimated by Excel-based regression analysis, processes including blasting and haulage from pits to crushers are modeled by a Forward Blasting simulation submodel, and material-handling operations including crushing, storage in stockpile, and haulage via conveyors and into SAG and ball mills are modeled by a Crusher to Ball Mill simulation submodel. A Reverse Blasting submodel is then used to obtain the optimum blast design corresponding to a target P80 particle size. Using the proposed framework, an economic analysis was performed to demonstrate the cost savings that could be realized for each rock type as a function of specific explosive energy. IntroductionIn a modern hard-rock mine, various processes such as drilling, blasting, crushing, grinding and mineral liberation are optimized to increase productivity, a practice known as mine-to-mill (MTM) optimization. Blasting is important in MTM optimization as it is the first comminution process and has an impact on all downstream processes (Julius Kruttschnitt Mineral Research Centre, 1996; Nielsen and Lownds, 1997; Nielsen and Malvik, 1999; Chung and Katsabanis, 2000; Kim and Kemeny, 2011a; Kim and Kemeny, 2011b).Two main research topics have emerged in the area of blasting design: (1) identifying the optimal target blast fragmentation at each shot and (2) controlling the blast fragmentation for that target. As part of an MTM optimization study, Kim and Kemeny (2011a; 2011b) developed a site-specific blast fragmentation prediction model that can be used to identify the target blast fragmentation and can be incorporated into MTM optimization. They also reported methodology for assigning model parameters easily and with minimal human bias."

Jan 1, 2015

By A. B. Cecala

Video technology coupled with datalogging exposure monitors have been used to evaluate worker exposure to different types of contaminants. However, previous application of this technology used a stationary video camera to record the worker?s activity while the worker wore some type of contaminant monitor. these techniques are not applicable to mobile workers in the mining industry because of their need to move around the operation while performing their duties. the Helmet-Cam is a recently developed exposure assessment tool that integrates a person-wearable video recorder with a datalogging dust monitor. these are worn by the miner in a backpack, safety belt or safety vest to identify areas or job tasks of elevated exposure. After a miner performs his or her job while wearing the unit, the video and dust exposure data filesare downloaded to a computer and then merged together through a NIOSH-developed computer software program called enhanced Video Analysis of Dust exposure (eVADe). by providing synchronized playback of the merged video footage and dust exposure data, the eVADe software allows for the assessment and identificationof key work areas and processes, as well as work tasks that significantlyimpact a worker?s personal respirable dust exposure. the Helmet-Cam technology has been tested at a number of metal/nonmetal mining operations and has proven to be a valuable assessment tool. mining companies wishing to use this technique can purchase a commercially available video camera and an instantaneous dust monitor to obtain the necessary data, and the NIOSH-developed eVADe software will be available for download at no cost on the NIOSH website.

Sep 1, 2013

By Brianna M. Eiter, Jennica L. Bellanca

Mineworkers face a challenging and dynamic work environment every workday. To maintain a safe workplace, mineworkers must be able to recognize worksite hazards while they perform their jobs. Though hazard recognition is a critical skill, recent research from the National Institute for Occupational Safety and Health (NIOSH) indicates that mineworkers fail to identify a significant number of hazards. To further the understanding of mineworkers’ hazard recognition ability and to begin to address hazard recognition performance, NIOSH researchers analyzed data collected during a laboratory research study to determine the effect of individual mineworker factors including risk attitude, work experience, and safety training on hazard recognition accuracy. The results of this study show that mineworker risk attitude and safety-specific work experience affect hazard recognition performance while hazard-specific safety training does not. These results suggest that some of these individual factors can be overcome through experience and training. Potential strategies that can be used to address these factors are also discussed.

Aug 31, 2020

By Q. Xiao, R. Naidu, W. Li, S. Song

Acid mine drainage (AMD) derives from the oxidation of sulfide minerals, primarily pyrite (FeS2), and is the most severe environmental issue facing the minerals industry. The most common short-term approach to AMD treatment is migration control, such as acid neutralization and metal/metalloid and sulfate removal, through the addition of alkaline materials, including lime (Ca (OH)2), limestone (Ca CO3), gangue minerals and industrial wastes. This requires the continuous input of materials and may result in the production of a vast amount of secondary sludge requiring further treatment and disposal. Addition of chemicals is usually more important in metal/metalloid removal than in sulfate removal unless the sulfate is present in very high concentrations. A more promising long-term strategy for AMD prevention is source control through the complete removal of pyritic minerals and encapsulation of potential risk minerals by coating with impermeable surface layers. This is regarded as the most cost-effective approach, although the mechanisms underpinning this and the implementation procedures are yet to be fully elucidated. It is likely that long- and short-term practices can be combined to optimize the remediation of contaminated mining sites. Some factors such as differing geological and mineralogical characteristics and transportation costs must also be considered for the successful implementation of AMD prevention and remediation strategies. This review also considers some implications for AMD remediation, but the promising bioremediation of AMD is not discussed as it has been extensively reviewed.

By G. A. Christie

This paper presents a vision system capable of providing an accurate estimate for the volume of stockpiles using 2D images. By imaging a stockpile from multiple viewpoints with a two-camera system, a 3D point cloud of known scale is generated using image-based 3D reconstructions. With a small amount of user interaction, the points that correspond to the surface of the stockpile are extracted and used to measure the volume. The hardware required for the two-camera system is light enough to be carried by a small unmanned aircraft and is a cheaper alternative to LiDAR while still being competitive in terms of accuracy. When testing the volume measurement algorithm on a stockpile of known volume, the measured output was found to have less than a 3% error from the ground truth.

By S. Tafazoli, N. Himmelman, D. Chan, E. Chow

"While Wearable Technology has been garnering attention in the consumer market, enterprise and industry have just begun exploring its potential applications. Since February 2014, Motion Metrics International has been working in collaboration with Vandrico Solutions Inc. to apply Wearable Technology to improve productivity and safety in the mining industry. This paper discusses the value proposition of using Wearable Technology to deliver critical notifications in mining. The advantages and disadvantages of various form factors are explored. The challenges, both specific to mining and in general to Wearable Technology, are defined. Finally, the concept of MetricsGear™, the first Wearable Technology platform developed for mining by Motion Metrics International in collaboration with Vandrico Solutions Inc., is described. MetricsGear™ is designed to notify the user with minimal distraction to keep the user focused on their primary task, and aware of mission-critical events. This focus and awareness allows the user to work more efficiently and safely. INTRODUCTION The mining process consists of a series of intricate stages, where certain events or conditions in one stage can have a huge impact on other stages. The notification of these critical events or conditions is vital for ensuring the overall efficiency of the mining process. Critical notifications can be classified as two types: time-critical events and contextual information. Time-critical events are situations where a timely response from a responder can have a significant impact on seizing an opportunity or mitigating cost. Some Human-Computer Interaction (HCI) experts classify notification types based on the Interruption, Reaction, and Comprehension (IRC) framework. Time-critical events are classified to have high interruption, high reaction, and low comprehension due to their urgency. The responder should have just enough information to identify the crisis and react as soon as possible (Chow, E. 2014). For example, when a tooth is lost during shovel operation, it is necessary to recover the missing tooth before it jams the primary crusher. The consequence of missing this critical time period is a jammed crusher that can cause the mine to be out of production until the jammed tooth is extracted (Baumann, M. 2013). In this case, the responder only needs to see an image to confirm if the tooth is missing, and information to identify which equipment and when the tooth went missing (see Figure 1). Contextual information is relevant information that is valuable for the receiver to be aware of as it can present an opportunity to improve efficiency or save cost. According to the IRC framework, contextual information is classified as low interruption, low reaction, and high comprehension. They are not as urgent as time-critical events, but provides more detailed and informative information to assist the receiver. For example, when a shovel’s worn tooth is predicted to require replacement soon, a notification to a GET technician can help him or her schedule a pre-emptive replacement of the tooth in an already planned maintenance to prevent having to reactively schedule another one when the tooth is critically worn. This helps reduce the amount of equipment downtime to maximize production (Baumann, M. 2013). In this case, the receiver will look at the information when he has a moment to spare to get a quick forecast, and make use of this information as needed (see Figure 2)."

Jan 1, 2015

By Wayne L. Johnson

The depth capability of engineering seismographs has been greatly increased by the use of signal enhancement, a technique in which seismic waveforms created by repeated impacts are digitized, stored, and summed. Summation amplifies the signal and partially cancels background noise. This gives a clearer picture of the wave aid makes it possible to determine the travel tune of signals from 'eater depth. Signal enhancement combined with continuous display of waveform, permanent recording of waveform, and precision digital readout of travel time has opened new fields of application in mining and engineering. Recent work has clown that replacement sulfides can be distinguished seismically from country rock at Bistee, Ariz. Work on the Iron Range of Minnesota indication,: that, by using a 300 pound weight as the source, the Biwabik iron Formation can be traced down dip to several hundreds of feet traverses over known areas show that reflections can sometimes be identified. Reflection, if identified preclsely, give a mere accurate estimate of depth and buried topography. Comparison of ( ) and weight drop have given some understanding of low wave amplitude varies win; source candid

Jan 1, 1971

By R. J. Sheets

"What is the primary responsibility of geo-engineers in mining? Early in my career, I was asked this question by an experienced engineer. After explaining some various tasks, I was informed that the main responsibility was to monitor. Although this proved true for many cases, I came to understand that monitoring is merely one means to achieve the primary responsibility of a geo-engineer — ensure the safety of all personnel. The potential for groundwater to impact stability allows this responsibility to be shared with hydrogeologists as well. Inherently, we monitor to identify risks; we analyze designs and develop models to mitigate risks; and we are provided opportunities to explain to supervisors the geo-risks to personnel and mine plans that will result from particular courses of action. A couple years ago, I took an opportunity to share experiences from the first several years of my career as a geotechnical engineer with junior geoengineering staff within my company. The intent was to share situations that were a part of my development, so they could learn and understand their responsibility to the safety of all personnel. Similarly, the purpose of this article will be to share these thoughts with new geo-engineers in the industry in order to help prepare them for the challenges they will face.What is our purpose?A senior hydrogeologist shared an experience that occurred in their career. The experienced hydrogeologist had spent some time with the hydrogeology staff, most of them relatively new to the mining industry, to understand how they viewed, and carried out, what they perceived as their responsibility at an active mining operation. After a couple months of observing and mentoring, the senior hydrogeologist met with everyone and posed the question “What is our purpose?” I am sure that most junior geo-engineers would start explaining different tasks or projects that they must complete. The list would include monitor ground water levels, track slope movement, evaluate designs, build models, oversee drilling programs, etc. These individuals did as well their supervisor. After going around the room allowing each individual to answer, the experienced hydrogeologist provided them the real answer to the question: Safety. If you examine the root intent of nearly every responsibility geotechnical engineers and hydrogeologists have, it is to apply our professional skills to ensure the safety of our workforce. When the objective of safety from the geotechnical and hydrogeology disciplines is achieved, inherently accomplishing the mine plan should follow suit, or it should significantly minimize the impact by gravity or ground water."

Jan 9, 2018

By K. Hanna

Early identification of adverse geologic conditions and high stress concentrations during the high-speed extraction of coal using modern mechanized long wall systems is a major challenge facing the mining industry. Often, unexpected geologic anomalies that affect rock mass quality are encountered more rapidly, leaving the mine operator with insufficient time or information to deal with the changing ground conditions. The RockVision3DTM seismic tomographic system, developed by NSA Engineering, Inc., offers substantial benefits over conventional geologic/stress-detection methods and has been used successfully in coal mines worldwide. Tomographic images, produced economically and in near-real time, are easy to interpret, allowing mine operators to deal with potential hazards on a day-to-day basis. This paper focuses on the application of RockVision3DTM technology for delineating hazards caused by stress and geologic anomalies. Case studies for two bump-prone coal mines will be discussed. For example, (1) in a German deep (>1,130 m) mine, the drilling-yield method was used to verify the effectiveness of this technology in detecting stress anomalies ahead of longwalling; (2) in a Polish mine (-500 m deep), two longwall panels 4 km apart were monitored to assess structural and stress-related factors contributing to differences in mining conditions and magnitude of structural failures.

Jan 1, 1999

By Lena Paar

"Underground construction poses certain challenges for all parties involved because the actual ground conditions are often unpredictable. Highly complex projects like tunnel construction are affected by various uncertainties. To address this complexity, the construction contract has to be flexible enough to be adapted to the actual conditions (e.g. divergent ground conditions, work delays). However, the adaptation of a tunnel construction contract does not guarantee the absence of a margin of interpretation. The perfect construction contract is an illusion because ex ante statements of the actual ground conditions are not feasible. This paper will discuss contractual parameters that must be considered in order to enable an effective adaptation of the contract during excavation. It is therefore necessary to discuss the following topics: decision-making competence, variable remuneration, fair-risk allocation, value engineering and partnering between client and contractor. INTRODUCTION Thinking of tunnel construction processes, engineers’ first (or at least second) association is about ground conditions. When constructing under the surface, the project is directly related to the ground conditions; however, ground conditions are known fairly well in advance. The estimated conditions can be the same or can also differ from the existing ones. A clear view of the conditions is possible only by driving through the section. What Hoek calls “Geological unpredictability which is guaranteed to provide some surprises in even the simplest tunnelling job” is, in addition to contractual issues, one of two critical aspects of modern tunneling (Hoek 1982). Almost no research tries to figure out, what flexibility in this context means and how to approach it in the contracts. Papers dealing with the New Austrian Tunnel Method (NATM) pose some principles to meet the requests for flexibility (cf. Austrian Society for Geomechanics 2011). However, it remains unclear how to create contracts in order to make them “flexible” enough to react to divergent ground conditions."

Jan 1, 2016