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By V. V. Severov, Z. Lafhaj

The flotation separation of salt type calcium minerals is problematic, due to the similarities in their formation properties and the same active Ca2+ related site for interaction with anionic collectors and similar physicochemical characteristics such as solubility, point of zero charge, surface speciation, Ca-site density. The work was performed to achieve effective and selective separation of the calcium-minerals using pure minerals samples: four calcite, two fluorite, and two apatite samples. The effect of pure and mixing anionic collectors such as oleic and linoleic acid to different ratio (2:1; 1:1; 1:2) as well as the role of nonionic collectors on the selective separation of Ca minerals were studied. All flotation tests were performed in self-aspirated flotation cell. The results obtained with the blend of anionic collectors with the molar ratio of 2:1 show a separation between apatite and calcite at pH 5 and a ratio 1:2 at pH 9. The enhancing of separation contrast using the sodium silicate as a depressant for calcite and apatite is also examined as a function of oleate/linoleate ratio. Additionally, this paper discusses the enhancing of the selective separation of Ca minerals when anionic collectors were blended with nonionic reagents. The surface reactions in aqueous mineral suspensions and the adsorption of anionic collectors blended with nonionic reagents were studied by FTIR spectroscopy. An unexpected synergistic effect was observed for some ratios between anionic and nonionic reagents. The mixture of fatty acids and nonionic reagent showed very high flotation efficiency in comparison with fatty acid alone for the flotation of an igneous low-grade phosphate ore.

Jan 1, 2016

By S Flanagan, M M. Mete, A R. Tiryaki, M Guresci

First Quantum Minerals (FQM) operates the Cayeli underground copper mine in Turkey. In response to a lost time incident (LTI) that occurred at the mine in 2022, the mine management decided to introduce a new safety approach on-site. The initiative began with a comprehensive safety culture analysis conducted by Arti Consulting, involving focus group studies. Employees actively participated in candid discussions, sharing their insights on safety issues and offering solutions. These conversations were meticulously audio recorded, resulting in over 150 000 words collected from more than 100 employees. These transcribed narratives then underwent rigorous semantic analysis, with the assistance of a sociologist, to identify and dissect patterns of unsafe behaviour. This analysis found areas for improvement, particularly in near-miss and incident reporting, quality of safety toolbox talks and effectiveness of pre-work risk assessments. Subsequently, mine management deliberated on these insights and devised corrective actions. An emphasis was placed on involving all employees in the corrective actions through communication training, empowering them to own the decisions and changes made. These impactful measures were seamlessly integrated into FQM’s Think! Safety Program, which embodies FQM’s sensible health and safety strategy. FQM partnered with Strika Entertainment (Strika) to develop innovative visual-first safety communication tools that use illustration, animation and graphic design to simplify complex messaging into easy-to-understand edutainment. As part of this approach to safety communications, Cayeli and Strika revamped the safety toolbox talks to encourage employees to voice their concerns and receive feedback when their suggestions were implemented. The response from employees has been positive, with over 200 unsafe behaviours and conditions reported within the initial two months of launching the Think! Safety Program. Remarkably, the Cayeli Mine has not experienced any LTIs for the past 500 days as of 9 December 2023. This paper encapsulates the dedicated efforts to transform Cayeli into a safer mining operation.

Apr 16, 2024

By J Rowland

"Ventilation models are invaluable tools for both prediction of routine daily ventilation changesin an operating mine to circuit performance expectations at the mine in 20 yearsÆ time. Arguably ventilation offi cers are becoming increasingly reliant on maintaining an accurate ventilation model with which to do their work. This paper relates to the practical assessment of the accuracy and thus ability of a mine site ventilation model to be reliably utilised on such varied tasks. The author's experience shows that in some cases the incumbent model is found to be in a state of tune that demonstrates a mine wide detailed assessment of branch resistances is simply not required. The money spent on a detailed mine wide ventilation survey that is not required would be far bett er served purchasing much needed monitoring equipment, rather than fixing something that is possibly not even broken. The term ænot rocket scienceÆ has been incorporated into the title of this paper because it appears that many practitioners believe that circuit validation is diffi cult. As long as clear att ention to detail is paid to the actual data collection process then drawing an accuracy comparison between the circuit performance and the model performance at any particular point in time, is really very simple. This paper will show a manner in which a circuit can be analysed to determine its actual state of health by using various diagnostic tools and tips. It will help ensure that subsequent work scopes to address any highlighted model defi ciencies can be more effi ciently scoped and targeted. It will hopefully remind operational people that such self assessments can easily be done æin houseÆ if the appropriate steps are followed."

Jun 1, 2012

By R Jacobs, J Yeates

"The Stockman base metals project is situated in State Forest in the alpine area of East Gippsland, Victoria, adjacent to a National Park and within the headwaters of a major Ramsar-listed wetland catchment and the Murray-Darling River system. Site topography is steep, and elevated (650 m – 1200 m above sea level), and subject to circa 1 m annual rainfall, with occasional winter snowfall. The project consists of two volcanogenic massive sulfide (VMS) deposits to be mined by underground methods and treated in a 1.0 Mt/a central concentrator to produce copper and zinc concentrates for export over a ten year operational life. New resource projects are rare in Victoria. Recognising the sensitive setting, planning for the Stockman Project, which is now in the advanced permitting stage, has focused on balancing economic, environmental and social outcomes to ensure social licence to operate is secured and can be maintained. This has involved close attention to triple bottom line (TBL) risks and outcomes. Stockman has successfully gained State and Federal approvals via the Environmental Effects Statement process. The process of obtaining these approvals has required close attention to effective stakeholder involvement, and management of a lengthy and difficult approvals process, which is still to be finally concluded. This paper is a case study of the process of that permitting and the issues encountered to date. Key learnings from the experience have included: successful approvals require close attention to much more than just the project and its technical aspects and physical setting – effective stakeholder involvement and endorsement is critical the differing consultation requirements for local, regional and government stakeholders, to design and plan implementation of a project to meet TBL objectives, and to gain social licence to operate within the Victorian approvals process, the need for an effective lead government agency with policy authority dealing with material policy change requiring post-closure financial sureties estimating realistic permitting time and cost during the project evaluation phase. CITATION: Jacobs, R and Yeates, J, 2016. Stockman base metals project – sustainability, social licence to operate and permitting lessons learnt, in Proceedings Project Evaluation 2016, pp 98–110 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Mar 8, 2016

By D L. Kennedy

It has always been a challenge to accelerate the underground development progress by increasing the advance rate of each development round. Surveys have shown that most of the development rounds have only been pulled 84 per cent to 94 per cent of the drilled length. Where bare detonators have been used as primers, less advance rate is expected. In order to obtain a good understanding of the influence of priming upon the advance rate in underground development, a series of high energy primer trials has been conducted by Orica Explosives in the goldfields using various types of Orica high energy Anzomex « primers. It has been shown that development face has been pulled an extra 140 mm to 420 mm by priming with Anzomex « K primers compared with conventional primers. From all the trials at different sites, we have seen that the face pulled using K primers was more square than that pulled using conventional primers. Virtually, no butts and toe were left on the face developed using K primers. Computer simulation has been conducted using either a conventional primer, a bare detonator or a K primer as initiator. The study compared the predicted crack patterns developed around the toe of the hole and it was deducted that a detonator-initiated hole would leave a butt some 200 mm longer than that from a conventional primer-initiated hole, and a K primer-initiated blasthole would give rise to stronger initial p-wave, promoting crack development around the toe and increasing the ability to pull close to the full depth.

Jan 1, 1999

By J. W. Thompson

This work is a codification and annotation of the Congressional enactments relating to minerals, mineral lands, and mining. It covers every enactment of Congress from the original ordinance of 1785 to the present time, as well as all sections of the Revised Statutes of the United States relating to these subjects. These laws are grouped according to their general subject matter, and are arranged thereunder in numerical or chronological order. Many of the mining statutes include matter not pertinent to the subject, and only those parts of such acts are quoted as will properly show their relation to minerals and mineral lands and indicate how they should be construed. Some mining acts have been repealed or have become obsolete, and others have become incorporated substantially in sections of the Re- vised Statutes; but these are retained in order to show the changes made, and the constructions placed thereon by the courts are given as aids in construing the new or repealing acts. The annotations consist of legal propositions abstracted from the decisions of the various courts and executive officers of the Govern- ment that have interpreted the sections and statutes so codified. These legal propositions are arranged under the different sections and acts with appropriate headings, titles, and subtitles, in logical order, exhibiting the present status of each particular section or act and its application to the subject of mines and mineral lands. The annotations do not purport to be abstracts of decisions on the sub- stantive law of mines and mining generally, but are limited strictly to the interpretation placed on a given section or act definitely re- ferred to by a court or executive officer by the number of the section of the Revised Statutes or the volume and page of the Statutes at Large in which the Congressional enactment is found. It may be observed that the legal propositions stated are not always pertinent to the particular section or act under which they are classed and of which they purport to give a construction. The arrangement, however, is not an arbitrary one, but is so made for the reason that the courts or officers in the construction of a particular section or act definitely referred to by number or volume and page incorporated in the decision matter not strictly pertinent to the par- ticular section or act so designated. This statement applies especially to the interpretations placed on the sections of the Revised Statutes. The decisions abstracted for the purpose of this work are those of the United States Supreme Court, 234 volumes; the various Federal courts, 214 volumes; the decisions of the Department of the Interior

Jan 1, 1915

By Jürgen Kretschmann

According to the model of product life cycles, the global coal mining industry is in the stagnation phase. The coal demand of the main consumer, China, has peaked in 2013 and is slowly declining. The Norwegian sovereign wealth fund, the world’s largest, has excluded coal-related companies for ethical reasons. Important players like the UN or the EU have already begun to describe pathways towards decarbonization. Increasing competition between coal mining companies and the mining regions can be expected worldwide if companies want to keep their positions on the global and national coal markets. Companies will focus on the best deposits. European countries like France, Spain, or Germany are only forerunners of this development—their centuries of coal production have been finished. The concept of sustainable development (SD) is fundamentally based on a model of progress where ecological, economic, and social dimensions should be developed equally and positively. But without the idea of competition, the concept of SD is incomplete. Questions arise, such as how can SD be realized on stagnating or declining markets without guarantees for companies “to live forever”? How can SD be a corporate goal in a phase of decline? How can declining mining regions sustainably progress into a better future? The German hard coal mining industry’s lifecycle has ended in 2018 after 60 years of stagnation and decline. As of 2019, all hard coal consumed in Germany will be imported, especially from Colombia, Russia, and South Africa. What has been done in Germany to handle the coal decline in a sustainable way and the lessons learned from this process is described in this paper. It may be useful for mining regions who will face a similar future sooner or later.

By O. D. Staman

The risk assessment project examines the likelihood of inorganic contaminants from copper dump-leaching operations to contaminate domestic water supplies. The project examines contaminant transport by modeling contaminant movement from the base of a leach pile through the unsaturated zone and into the saturated zone. The modeling effort is unique in that it models infiltration, contaminant transport in the unsaturated and saturated zone combined with geochemical modeling of the unsaturated zone. The project incorporates probability theory to reflect the uncertainty of hydrogeologic parameters.

Jan 1, 1994

By Lance R. Barron

The U.S. Bureau of Mines (USBM) conducted ground pressure analysis of a wide abutment-type chain pillar in a two-entry gate road of a Western U.S. coal mine with an extremely weak immediate roof. About 15 m of fragile, low-strength mudstone lies between the seam and the lowest competent roof member. Three-and two-entry gate road designs with several pillar sizes and various secondary support systems have been employed to improve tailgate-entry stability, with varying results. This report discusses gate road layout and performance and secondary support effectiveness. The results of the pillar pressure study are compared to pillar loading predicted by a widely used pillar design method and to similar studies in other mines. A stability evaluation of the most recent longwall headgate, using the USBM Analysis of Longwall Pillar Stability (ALPS) method, indicates marginal stability in first-panel mining and instability in second-panel mining. The ALPS method and the USBM Coal Mine Roof Rating system are used to evaluate tailgate-mining stability of the previous gate roads and to determine pillar and entry width and top coal thickness criteria for tailgate stability in future panels.

Jan 1, 2010

By Brent A. Slaker, Khaled M. Mohamed

"Understanding coal mine rib behavior is important for inferring pillar loading conditions as well as ensuring the safety of miners who are regularly exposed to ribs. Due to the variability in the geometry of underground openings and ground behavior, point measurements often fail to capture the true movement of mine workings. Photogrammetry is a potentially fast, cheap, and precise supplemental measurement tool in comparison to extensometers, tape measures, or laser range meters, but its application in underground coal has been limited. The practical use of photogrammetry was tested at the Safety Research Coal Mine, National Institute for Occupational Safety and Health (NIOSH). A commercially available, Digital Single-Lens Reflex (DSLR) camera was used to perform the photogrammetric surveys for the experiment. Several experiments were performed using different lighting conditions, distances to subject, camera settings, and photograph overlaps, with results summarized as follows: The lighting method was found to be insignificant if the scene was appropriately illuminated. It was found that the distance to the subject has a minimal impact on result accuracy, and that camera settings have a significant impact on the photogrammetric quality of images. An increasing photograph resolution was preferable when measuring plane orientations; otherwise a high point cloud density would likely be excessive. Focal Ratio (F-stop) changes affect the depth of field and image quality in situations where multiple angles are necessary to survey cleat orientations. Photograph overlap is very important to proper three-dimensional reconstruction, and at least 60% overlap between photograph pairs is ideal to avoid unnecessary post-processing. The suggestions and guidelines proposed are designed to increase the quality of photogrammetry inputs and outputs as well as minimize processing time, and serve as a starting point for an underground coal photogrammetry study.INTRODUCTIONThe stability of underground mine ribs has been a safety concern for underground coal mines for decades. Unfortunately, the average rib fatality rate has been about 1.3 per year between 1996 and 2013 (Jones et al., 2014). In an effort to better understand coal rib behavior, photogrammetry is being investigated in this study as a measurement tool for surveying ribs in an underground coal mine environment."

Jan 1, 2016

By E. Isokangas

The production of minerals for economic use is a two-stage process, involving mining to extract the mineral from the ground, and processing to convert the mineral into a marketable product. Generally, mining and processing have been viewed as self-contained entities. Both have separate objectives, separate cost centres and key performance indicators (KPIs) that do not reflect the customer/supplier relationships that inherently exist. However, mining and processing operations are inter-connected and therefore intimately inter-related with the performance of one operation affecting the performance of another. Optimizing each stage separately without considering the whole system often misses potential economic benefits and energy savings. During the past fifteen years, the authors have been involved in implementing a holistic methodology ?Mine to Mill Process Integration and Optimisation (Mine to Mill PIO)? to maximize the overall profitability of the operation rather than just optimizing any individual process in a mining operation. Metso Process Technology and Innovation (PTI), along with their project partners, have conducted several projects to significantly increase their production- generating typically 5% to 20% higher throughput and improve the overall mine and concentrator performance through PIO methodology. This proven methodology has applications ranging from greenfield projects to long-standing operations with AG/SAG, HPGR or conventional grinding circuits. This paper explains the Mine to Mill PIO methodology and discusses the benefits of such an approach on the energy consumption, the overall costs and benefits of mining operations. The paper also summarizes several case studies illustrating the use of PTI methodology in a variety of applications. Keywords: integration, optimization, simulation, modeling, mine-to-mill, comminution, blast, drill, crushing, grinding

Sep 1, 2012

By Zoheir Khademian, Gabriel S. Esterhuizen, Morgan Sears

Based on the 2010-2019 Mine Safety and Health Administration (MSHA) accident report database, 91% of reported ground control accident in the US longwall mines were caused by gateroad roof instability. This can be related to the significant changes in loading conditions that gateroads are subject to from the development to the longwall abutment loading phases, combined with the thinly bedded shale roof, found in many US longwall coal mines. One of the challenges in designing efficient support systems is to understand the roof instability mechanisms along with support-roof interactions under this complex loading condition. Field monitoring of roof displacement and stress changes coupled with detailed analyses using numerical models are well-documented techniques to study the causes of roof instabilities. However, traditional modeling techniques require additional calibration to simulate delamination and buckling of shale roof, one of the main roof instability mechanisms in longwall mines. One alternative modeling technique is the UDEC Bonded Block Method (BBM) where bedded roof and support interactions can be explicitly captured. This paper presents the development of a BBM model of a longwall entry at a 180 m depth of cover with a three-entry gateroad layout along with roof extensometer monitoring results. The models are validated against the monitoring data, showing the potential for BBM numerical models capturing the complex roof and support system interactions to assist with optimizing gateroad layouts and support systems.

By Karen J. Dawson, Francisco Johnson

"Pressure-grouted high strength helical displacement piles are a recently developed pile type that can be useful in conditions where noise or vibrations must be low or where access or clearance is limited. However, there is no information in the literature that can be used to estimate the soil resistance of these piles or production rates. To fill this information need, this paper presents a New Jersey installation case history and the results of static axial and lateral load tests on both pressure-grouted and ungrouted high strength helical piles at the case history site and trial installation locations in New Jersey and Washington State. Piles between 25 and 50 feet long comprised of steel shaft diameters of 4.5, 5.5, and 7 inches with equivalent grout column diameters ranging from 12 to 22 inches were tested. Lateral loads of up to 100 kips and axial compression loads of up to 700 kips were applied. The results of the load tests are compared to predictions of lateral deformation and axial resistance.INTRODUCTIONHelical piles have long been recognized as a useful foundation type in situations where noise and vibrations must be limited, or where there are access or clearance restrictions. Relatively well-documented design methods and torque to capacity correlations have been developed for the most commonly used helical piles, which are relatively small (typically shafts of 6 inches or less) with corresponding low load carrying resistance.With the increased need to construct in congested urban environments, there is incentive to develop helical piles with higher axial resistance. Seismic and other loading conditions also require lateral resistance, which is low for the typically small helical pile shafts. One method of increasing the soil resistance, both axially and laterally and at relatively low cost, is to place grout around the shaft. Injecting the grout under pressure through the hollow helical pipe section and out a grout port or ports located near the toe of the pile has the potential to increase the pile resistance significantly above that which can be achieve by gravity grouting. Not only does the pressurized grout push out against the surrounding soil, but the rotating helix helps to distribute the grout laterally. Unfortunately, little information is available in the literature to help designers estimate the resistance of grouted helical piles in general and none is available regarding pressuregrouted helical piles."

Jan 1, 2016

By Björn Saxen

Outotec atmospheric Direct Leaching has so far been implemented for zinc production capacities of around 100,000 t/a. Lately, there has been growing interest for small scale direct leaching plants, producing circa 30,000 t/a of Zn. Such small leaching plants can provide extra front-end capacity in existing roaster-based plants and enable treatment of feed materials not suitable for roasting. In small scale plants the proven OKTOP® 9000 Direct Leaching reactors are not readily applicable, due the large size. For smaller installations a modular approach is proposed providing multiple advantages, such as reducing the construction time and amount of the site work required causing less disturbance to regular plant operation with reduced cost. In this paper, we present advantages that can be achieved by using modular OKTOP®C reactors and discuss also process design when connecting a small scale direct leaching process to an existing zinc plant. Also benefits of direct leaching expansion are presented.

By Ihsan Berk Tulu, Ted Klemetti, Deniz Tuncay

Accurately estimating load distributions and ground responses around underground openings plays a significant role in the safety of the operations in underground mines. Adequately designing pillars and other support measures relies highly on the accurate assessment of the mining-induced loads, as well as the load-bearing capacities of the supports. There are various methods that can be used to approximate mining-induced loads in stratified rock masses, both empirical and numerical. In this study, the numerical modeling approach recently developed at West Virginia University, which is based on the modeling approach developed by the National Institute for Occupational Safety and Health (NIOSH), is investigated using the finite difference software FLAC3D. The model includes the longwall panels, the adjacent chain pillar systems, and the different stratigraphic layers of the overburden. Using the 3D model, changes in loading conditions and deformations on the areas of interest, induced by an approaching longwall face, can be examined. This paper details the 3D modeling of a longwall panel utilizing this approach, and the verification of the results against field observations. The studied panel was 360 m wide with a 3-entry chain pillar system and about a 160-m average overburden depth around the studied area. The overburden strata consist of alternating layers of shale, sandstone, and limestone. The FLAC3D results were compared against field measurements from the mine site. The stress change values measured in the chain pillars were comparable with the modeling results. The model also replicated the surface subsidence profile obtained from field measurements fairly well. Overall, the 3D modeling approach was found to be successful for the case study longwall panel.

Sep 23, 2020

By R. J. Hickson

The giant El Abra copper mine project under development in Northern Chile will come on stream in early 1997 at a production rate of 500 million pounds of cathode copper annually. Ownership is 51 % Cyprus Amax and 49% Codelco. Cyprus Amax has construction responsibility. Total project cost is $1050 million. El Abra will incorporate latest operational technology with labor efficient practices to achieve world class productivity levels and low initial cash costs of about US $0.35/lb copper. Development procedures for the almost 800 million ton oxide deposit, as well as the hydrometallurgical processes selected for recovery of the copper values are discussed. Construction costs and pertinent technical data are shown.

Jan 1, 1996

By Franklin H. Persse

The Bureau of Mines estimated reclamation costs for 13 surface coal mines in nine States west of the Missisisppi River. With the exception of the Pacific Coast coal province, at least one mine in each of the western coal provinces was studied. Cost estimates were, made using standard estimating procedures from data obtained from company records, interviews with industry personnel, and onsite observations. Estimated costs are presented in four categories which represent the four phases of mined-land reclamation: (1) Design, engineering, and overhead; (2) bond and permit fees; (3) backfilling and grading; and (4) revegetation. Estimated costs as of the first quarter of 1976 are expressed as averages and ranges in terms of per acre, per ton of coal produced, and per million Btu. Total reclamation costs ranged from $860 to $7,200 per acre, from 6 to 84 cents per ton, and from 4 to 35.3 mills per million Btu. A mine in the Northern Great Plains coal province (Region D) showed the highest per acre cost whereas mines in part of the western region of the Interior coal province (Region A) experienced the greatest per ton and per million Btu cost. The high cost of reclamation in the Western United States is reflected in the backfill in and grading category, particularly in the cost of topsoil removal and subsequent replacement as required by individual State reclamation regulations.

Jan 1, 1977

By Vivian M. Troughton, Clifford J. Wren, Tony P. Suckling

"Secant pile walls are used for the construction of deep basement walls and earth retaining structures. Risk associated with secant pile walls is commonly perceived as being the safety of site personnel and the public during piling operations, or safety used in design. It is recognized that both of these are of paramount importance, but additional risks associated with the construction methods must also be considered to complete the risk management profile for any project. For the particular case of secant pile walls, if Clients take a ""back seat"" they may be unaware of the total risk package they are procuring. The authors argue that the piling contractor should be involved at the earliest stage giving input into the overall risk management process. Such early involvement within the professional team will maximise cost benefits to the Client and minimise the delays and cost increases sometimes associated with these works. A consistent methodology for identifying and then managing all the risks associated with secant pile walls is proposed. An example is used to demonstrate how this methodology should be employed. INTRODUCTIONThis paper discusses the value of a complete and integrated risk management process for structures with basements formed using a secant pile wall.The risk associated with any secant pile wall can be consicfered as comprising four components;1. Safety of people on site2. Safety of design or design methodology3. Construction risks4. Commercial risksAny risk management system needs to fully consider and integrate each of these four components to maximise the likelihood of a successful outcome for the basement.This paper concentrates on the construction risks for secant pile walls, as these are not often understood by the Client (in this paper the term ""Client"" also includes the main contractor, principal contractor, Engineer, Planning Supervisor, quantity surveyor and cost consultant)."

Jan 1, 2005

By Earl M. Frizzell

Investigation of mined land characteristics, evaluation of irrigation systems and evaluations by the mining industry determined that irrigation is a feasible method for aiding the revegetation of coal mined lands in the western arid and semi-arid regions (Sherman, et al. 1980). The various regions studied displayed a commonality of characteristics which enables, independent of the site or region, the recommendation of solid-set irrigation. Irrigation should be supplemental by complimenting natural precipitation and should be implemented on a temporary basis. For germination, the vegetation requires application of small amounts of water in a gentle, frequent, and timely manner. For the establishment phase of growth, moisture should be applied and stored in the soil either through pre-irrigation or deep irrigation.

Jan 1, 1985

By Seth K. Martin, Tony Nichlany, Alan R. Poeppel, Konstantinos Syngros

"This paper presents a case study on bored pile construction in challenging karst conditions below a supertall building in Kuala Lumpur. Innovative design and construction techniques helped keep the project moving through very difficult and unpredictable geological and drilling conditions. The development encompasses about 12,400 square meters and includes a 77-story tower, a 59-story tower, a five-story podium, and four contiguous basement levels. The site is underlain by a residual soil derived from a siltstone/claystone (the Kenny Hill formation), then limestone bedrock. Subsurface conditions are relatively uniform within the Kenny Hill and highly variable at the limestone surface. Extreme cases included 40-meter-tall underground caverns, 40-meter-tall pinnacles, and a 50-meter-tall underground rock ledge. Local piling practice in Kuala Lumpur involves deriving pile capacity entirely in the Kenny Hill formation to avoid the unpredictable limestone surface. However, the massive tower foundation loads and relatively shallow bedrock required the piles to be socketed in the limestone. The 77-story tower will be supported by 2.0- and 2.2-meter-diameter bored piles 50 to 100+ meters long, socketed in limestone, with working loads between 40 and 70 Meganewtons. Two Osterberg-cell load tests were used to develop a site-specific rock socket skin friction correlation with RQD. Exploratory rock probes were drilled at each pile location to design the rock socket length based on the rock quality and sloping rock conditions. The rock mass was pressure-grouted during each rock probe to improve the rock quality and fill voids in the rock.INTRODUCTIONThe Kuala Lumpur City Centre, home of the Petronas Towers and the world’s deepest foundations, will be the future home of a new supertall tower. The 77-story tower will be supported by a piled-raft foundation that relies on piles terminating in the highly erratic, karstic Kuala Lumpur limestone formation. The high building loads coupled with relatively shallow limestone across the majority of the tower footprint forced the piles to extend into the limestone."

Jan 1, 2016