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By Jozef F. Zurawski

River Des Peres Foul water Interceptor (Skinker–McCausland Tunnel) is a gravity sewer tunnel constructed to eliminate dry sewage overflows during high river stages and to improve the wastewater collection and treatment. The original 78-inch (2m)finished diameter Skinker-McCausland Tunnel started as a 21,500 feet (6.5km)interceptor with 13 work, drop and access shafts. The tunnel constructions included soft ground, mixed face and rock tunneling in karst formation with maximum overburden of 175 feet (53m). Due to the success of the project, the tunnel alignment was extended another13,361 feet (4.1 km) and 7 new structures by negotiating two additional segments with the contractor and the designers.

Jan 1, 2001

By N. W. Xu, C. Sha, F. Dai, Y. G. Zhu, B. Li

Underground caverns stability and excavatability of rock masses are of significance in geotechnical engineering, in both design and construction stages. Risks associated with underground group caverns of Houziyan hydropower station in southwestern China are growing as a result of continuous excavation-induced unloading. To improve our understanding of the underground caverns instability and resolve the complex subsurface conditions of the highly fractured rock mass, a high resolution microseismic monitoring system was established in the deep underground caverns, pursuing the relationship between the measured data about microseismic activity and excavation damage zones of surrounding rock mass. Through analyzing the tempo-spatial distribution of microseismic activity, excavation damage zones and potential risk regions in underground caverns were identified. Furthermore, the correlation between microseismic activity and pre-existing geological structures, as well as traditional monitoring was analyzed. In order to validate the correlation between seismicity and potential slip surface of underground caverns, a model was implemented into numerical code to further evaluate the deformation and stability of surrounding rock mass. The monitoring results demonstrate that microseismic events mainly occur at high stress concentration regions, which coincides with the results obtained from numerical analysis. Therefore, the comprehensive method incorporating microseismic monitoring and numerical analysis, as well as traditional monitoring and filed observation has been proven to be very promising in deformation and even instability prediction of surrounding rock mass in underground caverns subject to delineation of potential slip surfaces and excavation damage zones.

Jan 1, 2015

By C. Newman

"Over the past decade, as conventional underground deposits have been depleted, mining operations have been forced to produce at greater depths and in more geologically and geometrically challenging conditions. As such, there has been a global increase in the application of cemented paste backfill (CPB) in tabular deposits utilizing open stope mining method with a delayed backfill placement. Despite the extensive use of CPB, many fundamental factors affecting the design of safe and economical fill structures are still not well understood. A critical issue in the design of backfilled stopes is the determination of stress states within the fill material itself as well as the surrounding rock mass. Analytical equations provide a means of quickly evaluating the effectiveness of a given design. However, in developing these equations large assumptions are implemented to simplify the design problem. It is important that one understands these simplifications as well as their effect on the overall design. This paper investigates common analytical equations utilized in the evaluation of single vertical backfilled stopes and their assumptions through comparisons to numerical modeling results. INTRODUCTION AND BACKGROUND As the mining industry continues to produce at greater depths and in more geometrically and geologically complex conditions, cemented paste backfill (CPB) has gained traction as a means of providing localized ground support in modern stope-and-fill mining operations. The application of CPB in stope-and-fill mining as a ground support material has led to the reduction of mine waste costs, while increasing both mine production and stability. In an attempt to achieve total extraction of the mining reserve, stope-and-fill mining operations often employ a primary-secondary excavation-support sequence (see Figure 1). In this practice, primary stopes are initially excavated and then backfilled in a two-stage pour; plug and final pours. During the first stage (plug), a CPB material with increased cementitious content is placed at the bottom of the stope providing a strong base from which to build a backfill structure as well as protect mine works from material breakthrough. Following placement, the backfill plug is allowed to cure to a given strength as designated by the mine design. Upon achieving the required cure strength, a less cementitious CPB material is used to backfill the remaining stope area. This is referred to as the final pour stage. With all primary stopes excavated and supported using backfill, the extraction of the secondary stopes commences as primary stopes are utilized as artificial pillars. While the application of CPB in a primary-secondary extraction-support mining sequence allows for a substantial increase in reserve recovery, it is imperative the mining personnel and planning engineers have a clear understanding of the material’s behavior and stress interaction with the surrounding rock mass to ensure the most efficient, cost-effective, and safe extraction of underground deposits."

Jan 1, 2018

By B. T. Wells

This work concerns the stress fields encountered around mining tunnels. A critical review is undertaken of the various analytical assessments of the support requirements for mining tunnels. Comments are made regarding degree and type of support together with method and timing of installation. The results have been used to indicate the type of support required in different mining and geological conditions.

Jan 1, 1981

By M. Z. Emad, N. Abbas, Y. Majeed

Room-and-pillar mining is commonly employed for the extraction of rock salt in undergroundmines. Pillar stress is a major concern in these mines as it is directly related to stability and mineralrecovery. In this study a flat jack method was used to measure pillar stresses in three undergroundrock salt mines in Pakistan. The field work included determination of in-situ stress, in-situ elastic modulus, recording of field variables (pillar length and width, height and width of opening, opening width to height ratio, extraction ratio, and overburden height) and collection of salt block samples. The geomechanical properties of rock salt (uniaxial compressive strength, Young’s modulus, Brazilian tensile strength, and density) were also determined to estimate overburden stress, pillar strength, and factor of safety (both estimated and actual). It was found that the measured pillar stresses are proportional to the overburden stress values, with their magnitude ranging from 6.05 MPa to 11.97 Mpa, and the pillars were found to be stable. Regression analysis was performed to develop statistical models for in-situ stress and in-situ elastic modulus. Finally a quick guideline chart was developed to determine the suitable length of pillar for a given span and required level of safety.

Jun 5, 2023

By P. H. S. W. Kulatilake

To exploit an underground mine effectively and safely, it is important to have a good understanding of the geotechnical behavior around underground excavations made in the mine. The aim of this study was to investigate the geotechnical behavior around a tunnel excavated in a metal mine in China at the three-dimensional level. Using the information available on lithology, geological structures, in-situ stress measurements, physical and mechanical properties of intact rock, discontinuities and interfaces between different rocks, a three-dimensional numerical model was built by using the 3DEC software to simulate a tunnel excavation under a high in-situ stress condition. Effect of the discontinuity network, possible intact rock and discontinuity parameter variability, representation of rock masses as discontinuum or continuum material and rock support system on the deformation, stress, failure zone and stability around the tunnel was investigated. A very good agreement was obtained between the collected field deformation monitoring results and the results of the conducted numerical stress analyses.

Jan 1, 2012

By Fidelis T. Suorineni

Rockbursts are a major hazard in deep hard rock underground mining and tunneling. To date a significant number of rockbursts still defy conventional explanations. A review of rockburst case histories in the literature has shown that pillars and tabular excavations under shear loading are prone to rockbursting in situations where they are least expected under conventional knowledge of rockburst causes. Despite the evidence of the effects of shear loading on underground infrastructure, and the frequency of their occurrence, little is known about how this loading mechanism causes such large magnitude events and extensive damage. In this paper analytical and numerical modeling are used to understand the behaviour of pillars and tabular excavations under shear loading. The numerical modelling results show that pillars under shear loading are less confined than their equivalents in loaded in pure compression in the same geologic environment, and are therefore more brittle and weak. For tabular excavations under shear loading, the behaviour depends on whether such excavations are continuous, co-planar or offset with rock bridges. Analytical results based on slit theory show releasable potential energy in tabular excavations increases nonlinearly with excavation half-span. The study results are important for the safe and economic extraction of orebodies under shear loading.

May 1, 2011

By K. S. Lane

The problem of stability of slopes in reservoirs is one of real interest in civil engineering. The problem is whether the valley walls will remain stable or whether they are likely to slide as conditions are changed by storage of water in the reservoir. If major slides are indicated, as on the walls of relatively steep canyons, one must estimate whether they will be so located and of sufficient size as to interfere with operation of the reservoir-as by blocking the outlets, or by displacing sufficient water to over-top the dam in a huge wave. Some cases involve problems in soil mechanics for slides in earth or weaker rock; other locations need the assistance of rock mechanics for slides in harder rock. While this is not a new problem, attention has recently been focused on its importance by the hugh landslide into the Vaiont reservoir in 1963, which claimed the lives of over 2000 people and forced abandonment of the dam and powerhouse. VAIONT RESERVOIR SLIDE Fig. 1 shows Vaiont Dam in Italy which is a double curvature arch, 875 ft high, located on a tributary of the Piave River, north and west of Venice. When completed in 1960 it was the highest arch dam in the world. In 1960 a sizable landslide (some 700,000 cu yd) occurred on the left abutment a short distance above the dam. Following this, the reservoir was held down for construction of a by-pass tunnel through the right valley wall to insure connection with the upper end of the reservoir in event of further slides. In October 1963 a giant landslide occurred on the left valley wall, over a width of some 14 miles (see Fig. 2). Over 300 million cu yd slid into the reservoir, displacing the water and forming a hige wave 700 ft above the top of the dam as it hit the opposite, or right, wall of the valley. The wave then passed some 500 ft over top of the dam, followed down the tortuous winding canyon and debouched into the

Jan 1, 1967

By Lane, K. S.

The problem of stability of slopes in reservoirs is one of real interest in civil engineering. The problem is whether the valley walls will remain stable or whether they are likely to slide as conditions are changed by storage of water in the reservoir. If major slides are indicated, as on the walls of relatively steep canyons, one must estimate whether they will be so located and of sufficient size as to interfere with operation of the reservoir-as by blocking the outlets, or by displacing sufficient water to over-top the dam in a huge wave. Some cases involve problems in soil mechanics for slides in earth or weaker rock; other locations need the assistance of rock mechanics for slides in harder rock. While this is not a new problem, attention has recently been focused on its importance by the hugh landslide into the Vaiont reservoir in 1963, which claimed the lives of over 2000 people and forced abandonment of the dam and powerhouse.

Jan 1, 1969

By D. F. Coates

Slope problems arise on mining properties from cuts for roads and railroads and from open pits. When it is 'realized that 1,000,000 extra tons of waste may have to be mined as a result of an average slope being reduced by 1 ° it is easy to appreciate that the slope problems connected with open pits are of far greater importance than the others. The type of slope failure that can occur can be classified in different ways. The most useful classification would be one that separates the causes in such a way as to provide a basis for studies to deal with problems of prevention and control. Using this criterion the types of slope failures are classified into four groups. Having classified the problems in this way an understanding can be gained of the various mechanisms involved in failure ..

Jan 1, 1961

By D. R. Brox, J. Levell

The Montana Tunnels Mine was mined out to a depth of 900 feet at the end of 1999. The first signs of instability were recognized in 1996 along the upper slope area of the northwest sector when the pit was mined out to a depth of approximately 500 feet. To extend the life of mining operations, it has been proposed to extend and steepen the northwest highwall to a depth of 1000 feet. Slope stability analyses were carried out using the UDEC software program to assess the stability and deformation of the proposed highwall design. Back analysis of an instability in 1997 along the upper slope section and highwall deformation to date has indicated reasonable agreement with the observed mode of failure and displacement monitoring results. The results of detailed analyses of the proposed highwall design have indicated very limited additional deformation, further development of tension cracks is unlikely and large-scale instability is not expected to occur. A total of 40% of additional mining has been completed and ongoing displacement monitoring to date has confirmed very limited additional movement and no further tension crack development.

Jan 1, 2001

By Magnus Ruin

The dry deep mixing method for stabilization of soft soil has been used in the Scandinavian countries for 25 years. The typical application has been stabilization of soft inorganic clay. Today the method is used more frequently in organic soil with good results. The Limix System, introduced in the USA by Hercules Grundläggning AB and TREVIICOS Corporation, is a cost-effective dry deep mixing method used to stabilize most types of soft soil. This paper presents the general principles of stabilizing organic soil with the dry mix method and two case histories of soil stabilization projects in organic soil. Between October 2000 and June 2001 the Limix System was used in England to stabilize soft organic alluvium at the Channel Tunnel Rail Link, Contract 440. During year 2000 the Limix System was used in soft organic soil in Holland near the Groene Hart Tunnel entrance to support trench excavations for slurry walls and concrete barrettes.

Jan 1, 2001

By James J. Brady, Kenneth L. Faught, Chadi El Mohtar, Chaoshi Hu

"During construction of a 9.5-ft. diameter sanitary sewer tunnel, the City of Edmonton encountered a large pocket of flowing sand that flooded their TBM and caused significant surface subsidence, stopping further tunneling by the TBM through this zone. A unique collaborative effort ensued between the authors representing the city, consulting engineers and academic researchers to develop the optimal strategy for grouting the problematic soils. The site has a layer of very find sand between 20 and 30 ft. in depth with fines contents ranging from 5% to more than 40%. The collaboration extended from requesting additional site investigation efforts to shipping samples to the UT-Austin laboratories for grout testing plus ground and grouting characterization tests resulting in field recommendations for a full scale ground improvement program. New research information on the grouting of fine sands along with a collaborative framework for the design of in-situ grouting projects are the key topics presented. INTRODUCTION Encountering a large unexpected pocket of flowing sand with an open-faced TBM while excavating a tunnel below the groundwater table is never a good thing. This was certainly true for the City of Edmonton when one of their Lovat TBM’s became inundated by flowing sand while excavating the 9.5-ft. diameter Millwoods Double Barrel Replacement Tunnel in September 2013. However, since the City of Edmonton self-performed this work, a rare situation existed where the site could be investigated objectively, without the prejudice of contending parties selectively influencing how information was gathered and presented, to accurately examine site conditions with a goal of identifying the best remediation measures."

Jan 1, 2016

By S K. Das

An intensive investigation into modern roof support technology, including hy draulic and control systems, has been carried out against the perspective of global development and support behaviour on longwall faces across the Indian sub-continent. The wide ranging study examined various types and designs of modern supports used in seams of varying thickness and inclination where caving and stowing were practised. Consideration has been given to structural analysis, support resistance, the various forces acting over and on the powered supports and to support compatibility. The examination of the phy sical parameters has been allied to field experience and, together, have led to the formulation of standard designs for both the powered support structure and structural systems. A realistic mathematical model has been formulated for calculating the capacity of roof support requirements resulting from the actual behaviour of the immediate roof stratum. As a result of the work, it should be possible to readily select the most appropriate type of support sy stem for the conditions and longwall mining method that is to be employed.

Jan 4, 1997

By Rundqvist

The best method to minimise disturbances from traffic to the neighbourhood and in Urban is probably to go underground. For obvious reasons this will cause vibrations, noise and other environmental effects which need very strict regulations and quality assurance in order to complete the work successfully. One project is “Southern Link”, a part of a ring road system. The system of tunnels includes 16 kilometres of tunnels right beneath the south part of the city of Stockholm. At least 20.000 people will be or could be affected by different kinds of disturbances and pollution such as vibrations, noise, gas and groundwater. Another project is the “Arlanda Link”. A new railway with three stations has been built under the existing and running to Arlanda airport with its terminals. Authorities have carefully judged these projects, which cause complaints from neighbours due to disturbances. The blasting operations are professionally managed by the contractors and controlled by consultants to keep the regulations according to the Swedish standards, which are well described in the tender documents by risk analysis and technical descriptions. In spite of that, one conclusion is that it is not always possible to go underground without exceeding stipulated regulations with existing technique. Some of the regulations also double the cost of excavation

Jan 1, 2001

By Heiner J. Sander

Stanford University operates the National Research Facility which is located at the Stanford Linear Accelerator Center (SLAC) in Menlo Park, California. In order to improve and allow for enhanced experiments, the current facilities required expansion. A1500 foot long tunnel (20 ft wide by 21 ft high) and a 220 foot long underground cavern (49 ft wide by 32 ft high) were excavated through the Ladera Sandstone formation which is an intermediate geo-material with week rock properties. The overburden between surface and crown of the structures varies from 10 to 80 feet. The underground structures were excavated according to the principles of the NATM (New Austrian Tunnel Method). This paper addresses the challenges that were encountered during the construction phase of the project and how construction issues were resolved mutually by the owner, engineer and contractor. The implementation of geotechnical instrumentation, recorded data and interpretations, soil conditions and behavior encountered during construction are also presented.

Jan 1, 2008

By Jeff Salai

The CP-3A contract is the final segment of the MWWST’s 28.3 km (17.6 mile)pressurized water supply tunnel for the metropolitan Boston area. The 1,288 m (4,226 feet) of U-shaped tunnel alignment passed through five rock zones employing four different primary support systems. The short tunnel began in Weston, Massachusetts, at Shaft 5A in soft, completely weathered argillite, passed through a fault zone, and ended in Dedham granite. An 18-foot diameter horseshoe starter tunnel was built to accommodate a 4.94 m (16-foot 2 1 / 2 inch) diameter Robbins TBM. Heavy water inflows were anticipated and subsequently encountered during probe drilling. Pre-excavation grouting was implemented at high pressures to displace high water inflows in the starter tunnel and consolidate the fault zone. This paper will provide an overview of the tunnel construction with an emphasis on ground control, grouting and survey control.

Jan 1, 2001

By P. Harvey

"Following initial discovery in 1991, BHP Billiton Diamonds Inc. opened Canada’s first diamond mine, the EKATI Diamond Mine (EKATI) in the Northwest Territories on October 14, 1998. Four short years later, on November 29, 2002, saw the opening of North America’s first underground diamond mine, the Koala North mine. Nestled between the original Panda open pit and the new Koala pit, which is in the early stages of production, Koala North represents the only underground kimberlite mining venture in Arctic conditions outside the new underground mines being developed by ALROSA in the Yakutsk region of eastern Russia. Extensive underground kimberlite mining has been practiced in the Republic of South Africa for much of the 20th century and continues today.Underground mining represents a key component of the long-term business plan for EKATI. As various open pits reach their economic limit, continued recovery of high-value ore at depth is dependent upon the ability to productively mine the kimberlite pipes by underground methods. As a function of its location, size, and value, the Koala North pipe is ideally positioned to host the first underground mine at EKATI. Koala North is designed and approved as a learning mine, from which to gain valuable experience in preparation for the potential mining of other larger, higher value pipes by underground methods in the development, the Koala North mine is well into its production ramp-up phase and currently producing at around 1,200 t/day from the first two production levels."

Jan 1, 2005

By M Norbert, D O’Connor

The mainline running tunnels for Legacy Way comprise two tunnel boring machine (TBM) driven tunnels. Both TBM drives commenced at the Launch Portal adjacent the Mt Coot-tha Road. Excessive surface settlement arising from tunnelling would have had a significant impact to the road infrastructure. The geological structure above the tunnel springline is a mixture of fill, residual soil and weak rock. Given the combination of low ground cover and weak ground materials, along with the use of an open face TBM, an oversize pipe umbrella system has been installed above the tunnels. This pipe umbrella system is similar to that commonly adopted in conventional mined excavation support in soft ground except that the steel pipes are substantially larger in geometry and filled with concrete. It is acknowledged that similar systems with oversize pipe umbrella have been adopted elsewhere in the world in other projects. These systems often comprise of a full arch formed by conjoining oversize steel pipes (in contact only). By aligning the pipes in contact, the arching behaviour of the steel pipe would have been enhanced. However, this poses a degree of construction difficulty due to excavation and installation method of the pipes. The Legacy Way pipe umbrella system only consists of a partial arch at the tunnel crown and each pipe is spaced approximately 1200 mm apart with 900 mm diameter pipe, leaving a gap of approximately 300 mm between pipes. A reinforced concrete portal block was used to support the exposed ends of the pipes.This paper reviews the design analysis, the recorded deflections from the pipe umbrellas and surface monitoring during TBM launch and revisits the analysis using the newly available RS3 program, from Rocscience for 3D analysis of geotechnical structures.CITATION:Norbert, M and O’Connor, D, 2014. Starting the journey – launching of the Legacy Way open face tunnel boring machines in mixed face ground conditions, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 307–314 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

This is the initial issue of STATE MINERAL SUMMARIES. This publication provides estimated data and summaries of mineral activities at the State level for 1988. Most of the estimates are based on nine months data. These summaries have been prepared in cooperation with State geological surveys or related agencies. Individual State summaries are published separately as State Mineral Industry Surveys and copies can be obtained from the appropriate State Activities field office.

Jan 1, 1989