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By Robert B. Hopler

First, a definition: “an explosive is called a permissible explosive when it is similar in all respects to the sample that passed certain tests by the national Bureau of Mines, and when it is used in accordance with the conditions prescribed by that bureau. * This was the definition as stated in Miners’ Circular No. 2,” published by the United States Bureau of Mines in 1911, and it is still applicable today. Of course there have been changes over the years, with the name “MSHA Permitted Explosive” now the legal terminology since January 1989, but the old 1911 circular still tells us what the material is. Note that the definition doesn’t even specifically state “coal mining.” A permissible can be required in guy underground operation that is deemed to have a gas or dust hazard, although in 1911 it was certainly meant to refer only to coal.

Jan 1, 1995

By M. J. Michaud, M. J. Lavigne

"A cornerstone of any successful mining project is an understanding of the mineral assemblage and metal distribution comprising the deposit. Knowledge of the precise mineral/ metal zoning enables an operation to utilize different mining and processing methods optimized for different parts of the deposit. The Lac des Iles mine, located in northwestern Ontario, is one operation that depends on a good understanding of these issues. Current resources for the Roby Zone total 94.1 Mt grading 1.66 g/t Pd, 0.18 g/t Pt, 0.14 g/t Au, 0.062% Cu, and 0.053% Ni.The Roby Zone occurs within the gabbroic portion of the Lac des Iles intrusive complex and consists of three compositionally and texturally different ore types with variable PGE, base and precious metal contents. PGE occur as sulphides and bismuthotellurides in net-textured sulphides, coarse sulphide blebs and as finegrained inclusions within secondary silicates.Knowledge of the precise mineral/metal zoning has directly and indirectly improved several operational aspects, including resource modelling, mining, and processing. For example, metallurgical recoveries have been increased by up to 3% to 5% and concentrate grades have increased by up to 100%. IntroductionLac des Iles Mines Ltd., a wholly owned subsidiary of North American Palladium Ltd., owns and operates a 3000 t/d open pit mine and concentrate facility, located 100 km north of Thunder Bay in northwestern Ontario. The Lac des Iles PGE-gold-copper-nickel mine has been in commercial production since 1993 and in 1997, produced 1.8 million grams of palladium, 127 000 g of platinum, 114 000 g of gold, 438 000 kg of copper and 354 000 kg of nickel (North American Palladium Ltd., 1998).Under the Industrial Research Assistance Program (IRAP), a two-year study of the mineralogy of the Roby Zone was undertaken with a goal of improving the profitability of the mine. Geological mapping, petrography and geochemistry of the Roby Zone were completed during this study. Utilization of the detailed mineral/metal zoning identified as part of this study was implemented at the mine and shown to positively impact many operational aspects including mining and processing."

Jan 1, 2003

Introduction Some people say it is almost impossible to get mining permits in California. Some say the day of the lone mining entrepreneur is past. And some say you cannot make money mining gold where old-timers have already mined it, especially in Tertiary gravels. But a young mining operator and SME member, Tim Callaway, is proving these ideas wrong. Callaway's company, Brush Creek Mining and Development Inc., has the necessary permits for its Gardner's Point gold mine in Sierra County, CA. And, Callaway has secured funds for the 7.7 km'/d (10,000 cypd) Tertiary gravel operation. The company's initial goal is to produce 373 to 466 kg/a (12,000 to 15,000 oz per year) of gold at Gardner's Point mine at a cost of less than $6.43/g ($200 per oz). Feasibility studies are currently being conducted to consider product levels up to the 1555 kg/a (50,000 oz per year) involving additional plants and infrastructure. While exploring for other hard-rock properties, the Brush Creek company already operates the Brush Creek lode gold mine. The mine sits high on a ridge south of Goodyear's Bar, which is located on the North Yuba river. It might be noted that the Brush Creek mine has been the subject of media stories recounting how a mine can operate with sensitivity to the environment. Gardner's Point project In 1983, Callaway negotiated with the Gardners Point Ltd. Partnership for control of the Gardner's Point property. The Partnership had been engaged for three years in securing permits, mapping and drilling, and test mining. The Partnership actually mined about 43.5 dam3 (57,000 cu yd) of gravel, which yielded 25.2 kg (810 oz) of free gold. Later, the Brush Creek company acquired ownership of the property. The company then began its own exploration and development program. As underground development proceeded at the Brush Creek mine, plans matured for a high-volume operation at Gardner's Point. Australian and English investors contacted Callaway. A joint venture was negotiated. The Australian owners became majority participants; the Brush Creek company, a minority participant and the operator. The Australian investors agreed to contribute $3.5 million (60%) to the Brush Creek Joint Ventures. The Brush Creek company will contribute its expertise as well as assets and liabilities valued at $2.3 million (40%). About $2 million has been allocated to the Gardner's Point project. Later, Brush Creek Mining and Development Inc. sold 50.4% of the company's common stock to English investors for $5.4 million. Callaway negotiated this private placement, which permits further exploration of projects being investigated. Geography and history The Gardner's Point mine is located in the northern Sierra Nevada of California, about 9.6 km (6 miles) east of the little town of La Porte in Plumas County. The mine lies high on a ridge above Slate Creek, which divides Plumas and Sierra Counties. La Porte is accessible from the Sacramento area by a winding, paved, two-lane highway. But the mine is reached only by two different unpaved county and Forest Service roads. Both roads include steep grades in and out of the Slate Creek canyon. Mine elevation is about 1.4 km (4600 ft) above sea level. The area is thus threatened by occasional heavy winter snows, though it

Jan 3, 1987

By Jack Eloranta

"This paper compares energy requirements for blasting, crushing and grinding. By tracking electricalconsumption for various powder factors, a general trend has appeared. This study involved over 100million tons of ore and powder factors ranging from .5 lbs/L,T to .8 lb&T. Actual energy usage iscompared to predicted energy based on the Bond equation."

Jan 1, 1998

By R. V. Ramani

This volume, the first of a six volume final report, provides an executive summary of the research and results carried out under a grant from the U. S. Bureau of Mines on underground coal mine ventilation. Under the project, a mine ventilation simulator was developed. Sensitivity of leakage and friction factors on the total quantity and pressure requirements was studied. The simulator was applied to a new mine under development, and to an operating mine, to demonstrate the usefulness of the simulator in ventilation planning and in evaluating proposed changes to existing ventilation system. The titles of the other volumes are as follows: Volume II: Mine Ventilation Network Theory Volume III: User's Manual for PSU/MVS Volume IV: Sensitivity of Leakage and Friction Factors Volume V: Application of PSU/MVS to Ventilation Planning of a New Mine Volume VI: Application of PSU/MVS to the Analysis of Modifications to Existing Ventilation Systems

Jan 1, 1977

By Dae S. Young

The paper point out a new procedure to calculate the volumetric distribution of rock fragments. The method combines the practicality of digital image processing of the rock surface with the theoretical volume calculations based on principles and laws of fractal geometry. The final volumetric distribution curve is compared with the results from traditional sieving indicating close agreement.

Jul 17, 2000

By G. H. Lewis, C. L. Krcil, N. S. Harding, D. E. Havekotte

Introduction Limestone injection work was completed in a 440-kW (1.5-million Btu per hour) pilot-scale combustor in preparation for a 50,000-kg/h (110,000-lb per hour) industrial steam boiler limestone injection test program. The main objectives were to: (1) identify the important variables that affect sulfur capture, (2) determine the maximum SO2 removal, and (3) determine the effect of limestone addition on furnace operability and heat transfer. A more detailed report is given by Lewis et al. (1985). The test program was divided into two phases. The objectives of Phase I were to determine the important variables that affect SO2 reduction and to investigate the effect of limestone addition on combustor operation and heat transfer surfaces. The objective of Phase II was to determine, using only the important variables identified during Phase I, the conditions that resulted in the greatest sulfur dioxide reduction. Phase I Test program Using one limestone, five variables were identified as having an effect on SO2 reduction. These are noted with their respective ranges: heat release rate [103 to 166 kW/m3 (10,000 to 16,000 Btu per hour-cu ft)], Ca/S molar ratio (0 to 3), flue gas oxygen concentration (3% to 5%), additive particle size [90% -150 µm (-100 mesh) and 90% -45 µm (-325 mesh)], and burner stoichiometry (SR = 0.75 and >1.15). A 2.3% sulfur northern West Virginia coal, pulverized to a nominal grind of 70% -75 µm (-200 mesh), was burned for the tests. The limestone used was obtained from a Maysville, KY, quarry and contained 51.75% (wt) CaO. An 11-run statistically designed program (plus three duplicates) was used to screen the five variables. The effect of limestone injection on the combustor heat transfer surfaces was determined by comparing the heat transfer rates through a slag panel and fouling probes during periods with and without limestone injection. Combustor operation was determined by noting any operating problems that occurred during the tests. Test procedure After furnace wall temperatures had stabilized at operating conditions, heat transfer surfaces (slag panel and fouling probes) and the convection section were blown clean, and a four-hour test was begun. The

Jan 12, 1986

By Tuck M. A

The increasing depth, mechanisation and distance of working areas from surface connections places an ever greater contaminant burden on ventilation airflows. Some British Coal mines are already experiencing significant problems in providing adequate climatic conditions in the working areas and have had to introduce air conditioning. Previous work has shown that in mines of low to moderate virgin strata temperature the application of controlled district recirculation could serve to improve climatic conditions at the working area.

Jan 1, 1988

By Mohammad Irshad, Klaus Mussger, Harald Wagner

Despite the fact that the New Austrian Tunneling Method; NATM, has been used in the United States for the past 23 years or so, still considerable misconceptions exist in the industry about the nature of the method and its implementation. In the authors’ view its implications are usually not well understood. The paper provides an overview of the highlights of NATM usage over the past two decades to illustrate the point that NATM is now a well-established tunneling method in the U.S.A. Accordingly the thrust of this paper is on the more pragmatic aspects of the NATM technology usage as it concerns the Owners, Designers and the Contractors. Prior to examining the implications of NATM usage from the viewpoints of various stakeholders, it should be helpful to first briefly provide an overview of the history of the method as it was introduced and implemented on several key tunneling projects in the US, over the last 2 plus decades.

Jan 1, 2005

By Kenneth Gavin

Design practice for piles installed in Irish glacial till has developed in an ad-hoc manner, based on the results of un-instrumented load tests. This had led to designers using similar design parameters for both CFA and displacement piles. To address the concerns of industry a series of instrumented pile tests were performed by two Irish Universities. These tests summarized herein, revealed that CFA piles develop higher shaft resistance than piles driven in glacial till. However, they exhibit low base stiffness and the end bearing resistance that can be mobilized at acceptable pile settlement is low. The use of simple non-linear elastic design approaches to predict the load-displacement response is considered. The methods are used to predict the capacity of two large diameter CFA piles installed in glacial till. While the predictions were reasonably accurate at predicting the initial load-displacement of the piles, significant creep settlement developed at higher load levels. The cause of the creep settlement was investigated through the use of plate load tests and the consequences for pile design are discussed.

Jan 1, 2009

By B. Amadei, F. Tonon

Rock stress measurement is cast in the more general context of the determination of boundary conditions for rock engineering. A study on the effect of elastic anisotropy on underground excavations reveals that this effect is actually controlled by the imposed boundary conditions. Applications to tunneling and to the Underground Research Laboratory (URL), Canada, exemplify a procedure for boundary condition estimation formerly developed by the authors. The procedure displayed fast convergence despite the complex geometry, and the high degree of non-linearity of the models. In the URL application, the 3-D model was able to completely reproduce the complex measured stress pattern, and the 90° rotation of the principal in situ stresses with depth. In order to reliably estimate the boundary conditions reproducing the current in situ state of stress, response measurements of the rock mass to current disturbances are necessary as input data. La mesure des contraintes in situ tombe dans le domaine général de la détermination des conditions aux limites pour les problèmes de mécanique des roches. Une étude sur le rôle de l’anisotropie élastique sur les excavations souterraines montre que ce rôle est contrôlé par les conditions aux limites qui sont imposées. L’application aux tunnels et au Laboratoire Souterrain de Recherche (URL) au Canada, nous permet de présenter une méthode de détermination des conditions aux limites. La méthode converge rapidement bien que le géométrie soit complexe et que le problème soit non-linéaire. Pour le URL, le modèle 3D est capable de reproduire la distribution des contraintes qui ont été mesurées ainsi que la rotation de 90 degrés des contraintes in situ avec la profondeur. Afin de déterminer avec précision les conditions aux limites responsables pour la distribution actuelle des contraintes, la réponse du massif rocheux doit être connue et mesurée. In der Felsentechnik sind die Spannungsmessungen in Gestein an die Bestimmung der Randbedingungen gebunden. Eine Studie legt dar, dass der Effekt elastischer Anisotropie in unterirdischen Aushoehlungen von den Randbedingungen kontrolliert ist. Eine von den Authoren entwickelte Methode zur Bestimmung der Randbedingungen wird an Beispielen im Tunnelbau und im Underground Research Laboratory (URL) in Kanada illustriert. Auch bei komplexer Geometrie und einem hohen Grad an Nicht-Linearitaet zeigt diese Methode ein schnelles Konvergenzverhalten. Ein 3D-Model und dessen 90° Drehung der lokalen Hauptspannungen mit der Tiefe, kann bei einer URL Anwendung vollstaendig reproduziert werden. Um mit dieser Methode die Randbedingungen zuverlaessig abschaetzen zu koennen, werden der gegenwaertige lokale Spannungszustand sowie die Antwort des Gesteins und die resultierenden Stoerungen als Eingabedaten benoetigt.

Jan 1, 2003

By D P. Yang, Yang R. G

The laws of throwing and heaping of engineering blast are important for making use of throwing and heaping of thrown body to form certain shape, such as building dams by directional blast. The article is to apply Ballistic theory of single thrown body to take the throwing course of thrown body as the movement of particle system, and then delimit the total of thrown body into units of thrown bodies, and regard the heaping shape of single thrown body as a perfect triangle, and found a quantitative relation between macro-geometry parameters of perfect triangle and designed parameters of explosives. The theory has been adopted in blast practice and gotten good effects.

Jan 1, 1999

By R N. Robson, A B. Christie, I J. Graham

Strategy development by the minerals industry identified the fragmented management of mineral resources as a significant impediment to the discovery and development of New Zealand Æs mineral resources. The total gross value of New Zealand Æs potential resources of coal and minerals is estimated at about $400 billion, but their potential value is not being realised. The management of minerals is now largely under the control of 86 local authorities (regional and district councils) and the lack of recognition of the significance of the sector has lead to inconsistencies in the way minerals are managed. The industry strategy influenced science funding for minerals, with the result that the 'mineral wealth' component now includes research on making better use of resource data in minerals management. Initially this research has targeted Otago and Northland regions where a number of initiatives are now in progress.   In Otago the Regional Council has budgeted to contribute $1 million towards a regional geophysical survey to advance mineral exploration and the management of subsurface resources in the region, to work cooperatively towards improving public awareness of the significance of minerals to regional economic activity, and to better coordinate policy-making for minerals at regional and district levels.   Crown Minerals, and the Far North and Whangarei district councils are considering providing funding support for an economic study of the mineral potential of Northland, building on a mineral resource assessment undertaken by GNS Science. Enterprise Northland is adding minerals to their list of potential growth sectors, and is supporting the operation of a Northland region minerals focus group.   Regional development agencies and local authorities have shown that they are willing to include mineral resources in their development strategies and to provide for them in policies and plans when supplied with information and assisted with technical support.

Jan 1, 2006

By N. A. Gjostein

From their study of the anisotropy of grain boundary mobility in aluminum, the authors conclude that tilt boundaries have a higher mobility than twist boundaries because the atomic misfit at the pure-twist boundary is relatively small compared to the misfit at a tilt boundary for a given amount of misorientation. If this is true, then one would expect a twist boundary to have a lower grain boundary energy than the corresponding tilt boundary. Fig. 6, taken from the work of Gjostein and Rhines,10 shows that this is indeed the case for [001]-cu tilt and twist boundaries in the high-angle region, thus lending support to the authors' conclusion.

Jan 1, 1968

By J. A. Rusnak, M. M. Gadde, S. S. Peng

In situ stresses are one of the key inputs to a successful underground excavation design. Because of the complex mechanisms involved in arriving at the current state of stress at a point in the Earth’s crust, often the only reliable way of estimating in situ stresses is by actual measurement. In the United States coal mines, overcoring relief method is by far the most popular technique used for estimating the virgin stress field. Typically, for stress measurement with overcoring, a vertical borehole is drilled into the roof or floor of an underground coal mine opening to a certain distance and change in borehole diameter is monitored at multiple points along the length of the hole when this borehole is overcored. For the measured stresses to represent the pre-mining stress field, the measurement points should be located beyond the influence zone of the mine opening. Actual data from several US coal mines have been collected to check if the measured stresses by overcoring represent true in situ stresses. The data indicate that most of the stress measurements were within the excavation influence zone. A three-dimensional numerical modeling methodology was applied to one of the collected cases to correct the measured stresses for the excavation influence. The modeling approach demonstrated the usefulness of integrating numerical modeling into a stress measurement program to estimate ‘true’ in situ stresses.

Jan 1, 2006

By Rob Thomas

Main gate roof control during longwall retreat is subject to a significant increase in horizontal stress and risk. The implementation and management of an appropriate roof support design is as a result, an imperative requirement for any longwall mine and must in addition to the likely consequences of a roof fall, also consider the variables of the geotechnical environment, associated support costs and practicalities. This paper will therefore summarise a number of recent advances in main gate roof control in the Australian coal industry. Points considered include; (i) the ?Longwall Acceleration? concept, (ii) macro-scale horizontal stress notching, (iii) micro-scale horizontal stress notching, (iv) bedded versus laminated roof types and (v) the type of cable reinforcement used.

Jan 1, 2006

By J. P. Harrison

ABSTRACT: The significant effect of fracture surface morphology on the mechanical behaviour of rock masses is well known and has been studied by many people. For linear profiles taken from fracture surfaces, short- and long-period variation has traditionally been described using the descriptors ‘roughness’ and ‘waviness’, with Fourier series analysis being perhaps the most commonly used technique to distinguish between the two attributes. However, the mathematical procedure is involved and the assumptions that have to be made may not be appropriate for rock fracture surfaces. In this paper, an alternative method is presented that enables us to distinguish between roughness and waviness of a linear profile by performing only one straightforward analysis. In our technique, surface morphology is studied in terms of the distribution of unit normal vectors to the profile. The statistical analysis of the distribution is performed using Riemannian, rather than the customary Euclidean, geometry, and from this the 1D Riemannian dispersion parameter (DR1) is obtained, which quantifies the geometry of the profile. The method is applied at different scales to both synthetic sinusoidal profiles and real rock profiles. The results show how periodic behaviour of the profile is revealed at scales where DR1 is substantially equal to zero. RESUME: L’influence significative de la morphologie des épontes sur le comportement mécanique des massifs rocheux est bien connue et a fait l’objet de nombreuses études. Pour les profils lineraires, les variations de courtes et longues périodes sont traditionnellement décrites par les indicateurs “rugosité” et “ondulation” qui sont le plus couramment distingués à l’aide d’une analyse en series de Fourrier. Cependant, la méthode de calcul utilisée et les hypothèses faites ne sont pas appropriées dans le cas des épontes rocheuses. Cet article présente une méthode alternative qui permet de distinguer la rugosité de l’ondulation d’un profil en réalisant une seule analyse directe. Avec notre technique, la morphologie de l’éponte est étudiée comme une distribution spatiale de vecteurs normaux au profil. L’analyse de cette distribution est réalisée à l’aide de la géométrie Riemannienne plutôt que la géométrie classique Euclidienne et permet d’identifier la dispersion Riemanienne en 1D (DR1) qui quantifie la géométrie du profil. Cette méthode est appliquée à différentes échelles sur des profils artificiels sinusoïdaux et des épontes naturelles. Les résultats montrent que le comportement périodique du profil est révélé à des échelles où DR1 est essentiellement égal à zéro. ZUSAMMENFASSUNG: Der signifikante Effekt von Bruchoberflaechen Morphologien auf das mechanische Verhalten von Gesteinsmassen ist gut bekannt und von vielen Bearbeitern untersucht worden. Traditionel lineare Profile von Bruchflaechen sind mit kurz und lang periodischen Variationen, die auch als “Rauhigkeit” und “Welligkeit” bezeichnet worden sind, beschrieben worden. Hierbei ist wohl die Fourier Serien Analyse das wichtigste Hilfsmittel zur Unterscheidung der beiden Attribute gewesen. Hierfuer wird jedoch ein mathematisches Prozedere verlangt und Vorraussetzungen gemacht, die vielleicht nicht fuer Gesteinsbruchflaechen zutreffend sind. In dieser Publikation wird eine andere Methode vorgestellt, die uns mit Hilfe nur einer einfachen Analyse erlaubt zwischen “Rauigkeit” und “Welligkeit” bei einem linearen Profil zu unterscheiden. In unserer Methode wird die Gesteinsoberflaeche unter zu Hilfenahme der Verteilung von Einheitsnormalvektoren beschrieben. Die statistische Analyse der raeumlichenVerteilung dieser Vektoren wird mit Hilfe der Riemannschen, anstatt der ueblicherweise benutzten Euklidischen, Geometrie durchgefuehrt. Von ihr wird der Riemannsche Dispersions Parameter (DR1) abgeleitet, der die Geometrie des Profils quantifiziert. Diese Methode ist bei verschiedenen Masstaeben sowohl auf rein harmonische (sinusoidale), syntetische Profile als auch auf Gesteinsprofile angewendet worden. Die Ergebnisse zeigen, dass bei Masstaeben bei denen DR1 nahe Null ist periodische Characteristika der Profile hervortreten.

Jan 1, 2003

By Mingju Liu

China has been suffering from coal and gas outbursts since 1950s. Nowadays, the situation has become worse than ever with the need to mine deeper coal deposits at higher production rates in a more complex underground mining environment. In the year 2006 alone, 37 outbursts occurred in underground coal mines with a death toll of 232. This paper describes a case study of an outburst event, which occurred in July 2006 during the shaft development of the Mengjin Coal Mine, Henan Province, China at a depth of 768m below surface. Detailed analysis of the possible causes that led to the occurrence of the outburst is reported. These include the study of complex geological features, gas storage conditions, possible improper technical management practice as well as incomplete prevention and control measures. Based on the case study and the observation of outburst occurrence in China in the year 2007, suggestions have been put forward to help prevent and control future coal and gas outbursts.

Jan 1, 2007

By Y. Poornachandra Rao, P. C. Sudhakar, L. Malakondaiah

NBV commissioned a 27.6 MVA furnace in the year 2005. This paper explains: a)Furnace design features b)Furnace process control, Direct slag granulation c)Continuous casting, Waste heat recovery, Sintering d) Gas cleaning plant, Protection of Environment. Keywords: Furnace Equipment, SiMn Production, Casting, Heat Recovery and Low hood

Jan 1, 2007

By Cory J. E. Yacyshyn

Anchored steel pipe piles are being used more frequently in British Columbia for shoreline projects such as public ferries, cruise ship docks, containership terminals and locally in the expansion of the Vancouver waterfront convention center. While a 36? diameter driven pile may provide adequate compression loads it will not always achieve enough penetration to provide the required tension loading. That is why bundles of threaded anchors or strands are drilled through the center, past the pile tip, and anchored into the underlying strata. Drilling up to 250 feet deep through the piles in variable water bearing strata presents challenges. Southwest Contacting Ltd. (SWC) recently completed the three largest anchored pile projects in BC; Vancouver Port and Convention Center Expansion, Vanterm Container Terminal and the new Prince Rupert Cruise Ship Terminal. This paper will present the separate challenges encountered drilling the anchors. At Prince Rupert, the recently completed Northland Cruise Ship Dock ultimately required a cased system to drill and install triple thread bar anchors. When 200 foot long steel pipe piling was unable to penetrate the highly fractured gneiss/schist bedrock to obtain a seal and consolidation grouting was unsuccessful, a modified cased system was advanced deep enough into the rock to eventually seal. The 3-#20 bars were changed to 12-strands since the bars wouldn?t fit through the smaller cased hole. The options were limited because each dolphin only had enough room for a small hydraulic drill rig that wouldn?t have the power to fully case the holes. The Canada Place Pier Extension in Vancouver?s Harbor led to the development of an innovative tip design used later at Vanterm. The 36? diameter steel pipe piles were driven closed end but modified to permit drilling through a concrete plug at the base. The driving of the piles at Canada Place often knocked out the plug so we were faced with 50 feet of sand up inside the pile when the drilling started. This led to discussions on how to safely remove the sand, solidify the tip, and continue drilling to get past the tip without undermining the pile. Finally, Vanterm Berth Extension was completed with a unique drilling system because the pile tips stopped in hydraulic sands, as opposed to the native till. We were faced with advancing the casing to the till without undermining the base of the pile. With 100 psi water pressure at the pile base after we broke through the concrete plug, the trick was to prevent charging the sand with our 250 psi air which liquefies it and forced it up our drill casing. And of course, it has to happen just before Christmas holidays!

Jan 1, 2004