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By M. ]. [Mohkam

The paper describes the features of the problems encountered and the countermeasures taken for two different tunneling projects. Where, slurry shields were used to excavate, in soft heterogeneaous water-bearing grounds, tunnels passing at very low cover beneath existing foundations of H.T. electric pylons, underground structures and major utilities. In order to avoid any ground failure and/or damage to the existing structures, one option was ground treatement by grouting or freezing technics. However, it was judged that, based on previous experiences, excavation with slurry shield could be carried on securely using an appropriate slurry enriched with polymers and applying a well determined pressure at ground face. A three dimensionnal limiting equilibrium analysis model was used to determine proper confinement pressures. And, the appropriate slurry compositions were stabilished based on laboratory test results. The tunnels were excavated successfully, no ground failure was experienced, and the maximum settlement recorded (on pylons) didn't exceed 3 mm.

Jan 1, 1991

In their excellent paper, Milev and Spottiswoode have provided quantitative and definitive descriptions of an important phenomenon that hitherto has been largely the subject of conjecture. They convincingly show that ?site-response? can amplify the strong ground motions on the rock-wall of a stressed tunnel by a factor of 10 to 12 compared with the PPV in the solid rock mass (at the same distance from source). This knowledge gives us a firm foundation from which to begin to build an understanding of the mechanism of damage resulting from a rock burst. Regrettably this understanding is still far from adequate, in my opinion. The authors of this paper, however, have made some statements that are too reassuring and which tend to reinforce the sense of complacency that prevails among many members of the rock engineering community on the deep gold mines.

Jan 1, 2006

J. H. HEGINBOTHAM, a, metallurgist of the General Engineering Co., talked on "Current Milling Practice at Kirkland Lake," at the December meeting of the Utah Section. The ore is enough alike through the whole district so that some generalizations and comparisons may be made. The question as to whether or not the flotation process should be used in the flowsheet for extracting gold by cyanide solutions is still being vigorously debated, and it will seemingly need some years for a definite answer to be given. Most of the gold is either free, though much of it is finely dispersed in quartz, or occurs with pyrite. At times there may be 2 per cent of telluride compounds in the ore, but the amount of gold telluride present is small and has not been definitely established. It has been shown by Dr. Haultain and others that though gold tellurides may be so finely disseminated that it is necessary to grind the ore exceedingly fine, the compounds themselves are not difficultly soluble. (An increase in temperature helps to dissolve tellurides, and also to settle pulps.) It is likely that if the ore were ground through 400 mesh, practically all of the gold would be soluble. As it is, with 96 to 98 per cent of the ore ground to minus 200 mesh, and some 70 per cent minus 325, the cost of

Jan 1, 1934

By A C. Robertson

World urban expansion puts constraints on the available land surface area of our major cities both for accommodating people as well as providing infrastructure and services whilst at the same time attempting to preserve the remaining natural environment. Whilst consideration is often given to underground planning for private and public transport infrastructure, the author is of the opinion that the current lack of underground planning of our cities that are suitable for underground development will have major long implications when finally the need for underground space planning is critical and ultimately recognised. This paper identifies the need for our city planners to integrate surface planning and underground planning as a ‘total planning solution’ where the city plan incorporates the elements of underground space planning as identified in this paper. Investigations by the author reveal that there are very few cities in the world that actually incorporate underground space planning in their city plans. The author uses the City of Brisbane as a case study for the potential introduction of underground space planning as part of the city plan. Despite efforts by the author to include the planning concept of underground commercial development in the latest Brisbane City Plan 2014 as well as four underground space workshops in Brisbane over the past 20 year through the Australasian Tunnelling Society (ATS), underground space planning for the City of Brisbane, apart from infrastructure projects, is not considered of significance to the City of Brisbane.CITATION:Robertson, A C, 2014. Commercial underground space – planned development for the future, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 513–518 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By E. R. Johnson

The copper concentrator of the Braden Copper Co. is at Sewell, Chile, on the westem flank of the main Cordillera of the Andes, at an air distance of approximately 50 miles southeast of Santiago, the capital of Chile. The region is mountainous and space is at a premium because of the rough terrain and the danger of snowslides. The ore, a porphyry copper, is mined by a block-caving method in the El Teniente mine. It is hauled to the crushing plant, a distance of 2.6 miles, through a tunnel because of the severe climatic conditions. The usual large, coarsely set, primary reduction machines found in many ore-treating plants are not required because of the mining method employed and the limiting 12-in. spacing of the grizzlies at the head of each ore pass in the mine. It is the purpose of this paper to describe the numerous improvements made in the crushing section of this large flotation concentrator during the past I5 years to increase the efficiency of the plant and to raise the daily output from around 20,000 to 30,000 tons. The reader should keep in mind that all changes were made within the existing building because of the limited space and the high cost of the heavy mill construction required to withstand the snow loads. The present plant, as well as the former, operates on a 24-hr, 7 days a week basis. The crushing plant commenced operations at its present site in 1921, the main equipment being No. 7½ gyratories, followed by 48-in. horizontal Symons disk crushers. Fines were removed by I-in. stationary grizzlies ahead of each unit. In 1924 a third stage of crushing was provided by the addition of 55½-in. rolls in open circuit. During 1925, the Symons disks were replaced by 73½-in. rolls. All the rolls were changed to closed circuit, with elevators and screens to give a final product of 9 pct plus 3-mesh. The flowsheet of a typical crushing section of this period is shown in Fig I. The ore was withdrawn from a common bill serving the five crushing sections in the plant by means of any number up to six 36-in. wide-apron feeders, which discharged onto a common conveyor belt. This conveyor was equipped with a magnetic head pulley and the crusher attendant was stationed near the discharge end to pick out pieces of mine timber that might be in the ore. The ore was discharged over a 13/4-in. spaced bar grizzly and the oversize of this grizzly was crushed by a No. 7½ McCully gyratory crusher set at 13/4-in. opening on the closed side. The grizzly undersize joined the gyratory discharge and was conveyed to a set of 73½ by 20-in. Garfield rolls set at I in. These rolls operated in closed circuit with a bucket elevator and two vibrating screens placed in parallel.

Jan 1, 1949

By Sarah Wilson, John Kaplin

Plans are underway to extend commuter rail service underground into downtown San Francisco. The Salesforce Transit Center (STC) was completed in 2018 and will serve as a new transit hub, including a commuter rail station after two future connecting tunnel segments are completed. The northern segment, known as the Caltrain Downtown Extension (DTX), which will extend the rail line from its current terminus at 4th and King Streets to the STC, is currently in Preliminary Engineering. The southern segment, the subject of this paper, is a 1.6-mile tunnel known as the Pennsylvania Avenue Extension (PAX), which is currently in the pre-environmental planning stage, with alternative alignments under evaluation including single bore versus twin bore options. This paper discusses project challenges, including highly variable tunneling conditions in soil and rock, a congested urban project site with limited space for construction staging, alignment crossings of large existing buried infrastructure, and complicated interfaces with future and existing rail operations.

Dec 1, 2022

By Steven R. Wardwell, Gerald G. Stokes

INTRODUCTION A compaction grouting program to control ground loss, and to minimize surface settlement, was developed for the West Tunnel of the Phoenix Storm Drain Tunnels. The West Tunnel was 4,200 m long, 7.56 m in excavated diameter, and was excavated with shallow cover through the central Phoenix business district. The tunnel could not have been successfully excavated without the compaction grouting program. HISTORY After heated political debate over a ten year period, the Arizona Department of Transportation (ADOT) was granted approval to build the Papago Freeway, an extension of Interstate 10, through central Phoenix. To comply with environmental constraints, a portion of the Freeway was depressed, requiring an excavation 10 meters in depth, thus intersecting surface run-off from the northern section of Phoenix. This required that ADOT and Project Design Consultant, Howard, Needles, Tammen & Bergendoff (HNTB) design a drain system to collect run-off and transport it approximately 4 kilometers to the Salt River through the City of Phoenix. Tunnels were chosen for the main discharge conduits because depth and location of the system made cut and cover construction impractical. A contract for construction of the tunnels was awarded to Shank-Artukovich-Ohbayashi (S-A-O) on May 24, 1984.

Jan 1, 1987

By J. C. Keenan

Company-community agreements are widely considered to be a practical mechanism for recognising the rights, needs and priorities of peoples impacted by mining, for managing impacts and ensuring that miningderived benefits are shared. The use and application of company?community agreements is increasing globally. Notwithstanding the utility of agreements, the gender dimensions of agreement processes in mining have rarely been studied. Prior research on women and mining, however, does show that women are often more adversely impacted by mining than men, and face greater challenges in accessing development opportunities that mining can bring, however there is currently little to no guidance for companies, government or communities in terms of bringing a gender perspective to the fore in mining and agreement processes. While it is undisputed in human development literature that investment in women and sensitivity to gender delivers long-term health, education and local development outcomes, a number of key factors remain unexplored in debates about mining and development. These include: women?s participation in agreement processes, the gendered distribution of agreement benefits, and the extent to which impacts and benefits influence (either positively or negatively) women?s development and economic inclusion. This paper presents the results of an applied research project undertaken by the Centre for Social Responsibility in Mining (CSRM) at The University of Queensland and funded by a partnership between the Minerals Council of Australia (MCA) and the Australian Agency for International Development (AusAID). The project sought to connect with practitioners who had been directly involved in agreement processes to hear grounded perspectives on the interaction of gender dynamics and agreements, and connect those experiences with the broader literature. Findings from this study have implications for the role of companies and governments in promoting gender equality and empowerment as part of their commitments to sustainable development. A key challenge for companies will be navigating the territory of cultural norms and gender equality. The authors argue that without consideration of the gender perspective, and appropriate responses, mining agreements may not be inclusive or representative and may exacerbate gender inequalities and fail to contribute to long-term sustainable development.

Aug 1, 2013

By H. A. D. Kirsten

The structural competence of mesh- and fibre-reinforced shotcrete was investigated in two series of tests on full-scale panels. It was found that uniformly distributed loading was marginally less demanding than point loading, mesh reinforcement was superior to fibre reinforcement, Dramix fibre and Melt Extract fibre were similar in reinforcing characteristics, and 30 mm to 35 mm was an optimum fibre length. Furthermore, the consistency of the fibre content could not be assured on practical mining sites, and an average fibre content of about 1,5 per cent was the maximum that could be obtained for fibre lengths not exceeding 35 mm. Also, owing to its greater flexibility, shotcrete reinforced with diamond mesh was preferable to fibre-reinforced shotcrete in mining excavations subject to squeezing conditions. In view of the difficulties associated with assuring the consistency of the fibre content in mining applications, it appears that the sophisticated attributes of fibre-reinforced shotcrete can be effectively exploited only in civil-engineering applications in which quality assurance is subject to explicit contractual control. Load-deflection curves, together with measurements of compressive stresses in the surfaces of some of the panels, enabled the ultimate flexural strength of reinforced shotcrete to be rigorously formulated, and rigorous design procedures for shotcrete subject to bending and direct thrust to be developed. The application of the procedures is demonstrated in a practical design case in which the moments and thrusts in a tunnel lining are determined in a numerical analysis of the interaction between the lining, the surrounding rock, and the rock-reinforcing system.

Jan 1, 1992

By Jason Saldanha, Andrew Evans, Jonathan Baber

"INTRODUCTION The need for a new road crossing at Silvertown is the result of three key drivers:- •,Severe congestion and delay at the Blackwall Tunnel and surrounding road network; •,A lack of network resilience and reliability resulting from a lack of alternative road crossings in east London and the impacts of unplanned closures; and •,The need to support substantial economic development in east and south-east London (jobs and homes) These drivers directly informed the main objectives for a road-based river-crossing solution. The traffic-related problems at Blackwall Tunnel are long-standing and before Transport for London (TfL) assumed control for the strategic road network in London in 2000 the Department for Transport (formerly Dept of Transport) had investigated various relief options including a third tunnel bore and new bridge. This resulted in a new crossing alignment being safeguarded (by direction of the Secretary of State for Transport) and this was refreshed in 2001 in favor of TfL. In recent years (since 2009) TfL as part of the East London River Crossings Programme has undertaken detailed optioneering and feasibility work to address the above ‘need’. This led to the conclusion that a new road tunnel would offer the best solution in preference to bridge, ferry or demand management options. In 2012, in response to a formal request by the Mayor of London, the Secretary of State for Transport confirmed a new road crossing at Silvertown as a Nationally Significant Infrastructure Project (NSIP) by Section 35 direction under the Planning Act 2008. This NSIP designation meant that TfL as scheme promoter must comply with the National Rail and Road Networks National Policy Statement (NNNPS) and must seek the necessary powers to build and operate the crossing by means of a Development Consent Order (DCO) under the Planning Act 2008."

Jan 1, 2016

By Ehsan Alavi, Brian Hagan, Colin LaVassar, Glen Frank, Derek Dugan, Rick Capka, Lisa Mori

"Tunnel face instability is one of the most common issues in EPB tunneling. The evaluation of an ideal face support pressure is a critical element in the design and construction phases of EPB tunneling. In this study, measured tunnel face pressures in three EPB tunneling projects (University Link U230 and U220 projects and the Northgate Link Extension N125 Project) for Sound Transit in Seattle, WA are compared with the calculated analytical methods. This comparison shows that the analytical methods generally overestimate the required tunnel face support. The best practice for managing the face pressure in EPB tunneling operation is discussed based on the experience gained through these projects. Furthermore, the algorithm that is developed for identifying ground loss in these projects is addressed. INTRODUCTION Earth pressure balanced tunneling relies on using muck within the chamber to support the face. Muck is pressurized by controlling the advance rate of the tunnel boring machine and the speed of the screw conveyor. Target face pressure is typically calculated by using the geotechnical assumptions in the geotechnical baseline report. The concept behind EPB tunneling is that the application of sufficient face support pressure will prevent tunnel face instability and the resultant over excavation. Tunnel face instabilities caused by a lack of sufficient face support can lead to ground loss and surface settlement (Anagnostou & Kovári 1996, Kirsch 2010). A certain support pressure must be achieved to counteract water and earth pressure with an adequate factor of safety. While the water pressure can be predicted accurately, the determination of the resultant earth pressure on the face is less precise. This becomes manifested in the relatively high partial safety factors on the earth pressure."

Jan 1, 2016

By Eleanor Kentish, Nathan Bond, Edward Batty, Simon Webber, Alan Skarda

"Crossrail is Europe’s largest construction project — a new 100km rail route running through central London. A joint venture of BAM, Ferrovial and Kier (BFK) has constructed the tunnels and escalator shafts at the new Bond Street and Farringdon Stations. The recent trend in the UK industry towards sprayed secondary linings is driven by the potential for significant savings in cost and time. BFK is unique within Crossrail by constructing both sprayed and cast secondary linings. This paper presents a direct comparison between sprayed and traditional cast in situ secondary linings at Bond Street and Farringdon Crossrail Stations. An objective comparison is drawn between procurement and mobilisation periods, production rates, flexibility, tolerances and logistics in the tunnels. The technical challenges surrounding cast and sprayed secondary linings are explored, and recommendations are made of how each method could be improved for future use. INTRODUCTION It is well established that sprayed concrete offers a fast and effective method to seal the face of an excavation. In a relatively short space of time, sprayed concrete can be applied to an open face to support the short term ground loading on the tunnels during construction. Advances in sprayed concrete lining (SCL) technology — such as the use of wet mix processes, improved accelerators, fiber reinforcement, remotely controlled spraying robots, innovative surveying equipment and nozzleman competency schemes — have greatly increased the speed and safety of tunnel excavations using this technique. As a result, design engineers have become increasingly confident to use SCL primary linings as part of the permanent structural lining (Su 2014). Historically, long term ground and water pressure loads have been considered to be carried by the main structural or secondary lining, constructed using cast in situ concrete (Pickett 2014). However, the advances described above have made sprayed secondary linings a viable option, which has already been proven on the A3 Hindhead Tunnel (Arnold 2012). Sprayed concrete secondary linings offer potentially significant savings in cost and time during the construction process. The contractor does not need to procure a bespoke formwork system for each different sized tunnel — the SCL plant required is already on site for the primary lining. Each bay is sprayed with accelerated concrete, becoming self-supporting almost immediately — compared to moving and resetting the shutter, pumping concrete and waiting for it to cure. With sprayed concrete, working sequences and cross sections can easily be changed."

Jan 1, 2016

By N. Naude, L. S. Leal Filho, M. P. Tshazi

In this paper, the authors performed experiments in the Denver and Leeds laboratory flotation devices at the University of Pretoria at various particle sizes to evaluate the performance of the devices. Quartz was used in a single mineral system at discrete sizes fractions, -25 μm, +25- 45 μm, +45-75 μm, and +75-106 μm. Hydrodynamic analysis, based on dimensionless power and Reynolds numbers, indicated that the Leeds cell required higher power input to achieve comparable flow conditions. Specifically, the Leeds cell exhibited an average power number of 1.03, whereas the Denver cell averaged 0.77 within the same impeller speed range of 1000 rpm–1500 rpm. For comparative flotation performance, impeller speeds were calibrated, resulting in operating speeds of 1200 rpm for the Denver cell and 1400 rpm for the Leeds cell. The cells performed similarly at two coarser-sized fractions. However, some deviations were observed in the finer particle size range. The -25 μm (fine) fraction initially achieved a recovery of only 15%. An additional reagent dosage was required to enhance the recovery of this fraction significantly. These findings highlighted the influence of particle size on flotation recovery. For all experiments, the Denver laboratory flotation cell outperformed (defined by higher recovery) the Leeds device, while still operating at a lower impeller speed. This advantage can be attributed to its impeller-stator design and air dispersion features, effectively overcoming slurry resistance and resulting in superior flotation performance compared to the Leeds cell.

May 27, 2025

By Roozbeh Afzali

Designing an appropriate tunnel blasting pattern reduces the cost of rock breakage and subsequent operations such as loading, haulage and support of tunnels. For that reason, we developed a software that designs tunnel blasting patterns. Using this software, three different tunnel blast design models based on parallel hole cut, namely, Swedish, Konya and Energy Balance, were investigated and compared for a virtual tunnel. Accordingly, blasting patterns were designed, for different cross sections. The trend of parameters such as specific charge and specific drilling as functions of tunnel cross-section was determined for each model. Our results show that, in general, The Swedish model gives lower specific charge and specific drilling compared to other models.

Jan 1, 2008

By F Sandrone, J-P Dudt, J Zhao, E Paltrinieri

Tunnel boring machines (TBMs) excavation is nowadays more and more considered a valuable alternative to conventional tunnelling. As a matter of fact, thanks to its advantages such as greater rate of advance and safer working conditions, the application of TBMs has increased significantly in recent years. Despite the possible excellent performance of TBMs in favourable ground conditions, the advance rates could be significantly slowed down or even obstructed in limiting geological situations. This obviously traduces in potentially longer tunnel construction times and higher costs and, therefore, in a preference for conventional method. One of the major geological hazards encountered during tunnel construction, is related to the presence of fault zones or heavily jointed and fractured rocks. The most common geotechnical problems resulting from tunnelling in these difficult conditions include the instability of the excavation face, instabilities of side-walls producing large overbreaks on the tunnel profile, excessive deformations in case of squeezing grounds, frequently changing stresses in terms of magnitude and direction, high water inflows, etc. The decisions aids for tunnelling (DAT) is a model and a computer code that can be used to evaluate the influence of the uncertainties related to both the geological/geotechnical conditions and the construction process on final tunnel construction time and costs. In this framework, the DAT is used for assessing the effects that challenging ground conditions may have on tunnelling operations in terms of costs and delays. This is done by simulating the tunnel construction considering several geological profiles. The aim of the study is comparing different excavation methods (ie drill and blast versus TBM) in changing ground conditions along the tunnel alignment ranging from good rock, to very poor and fractured formations. The results show the impact, in terms of changing construction time and cost, of the excavation method versus the ground conditions.CITATION:Paltrinieri, E, Dudt, J-P, Sandrone, F and Zhao, J, 2014. Comparison of excavation methods in different ground conditions with the decision aids for tunnelling, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 573–580 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By Klaus Rieker

Over the last 30 years Wayss & Freytag Ingenieurbau AG has gained a lot of experience in mechanized tunnelling on various major projects. During this period most important developments concerning the machine technology for EPB- and Slurry-Shields have taken place. Since the first application of a hydro shield for the Wilhelmsburg Collector project in Hamburg in the early seventies, several stages of development have led to the current state-of-the-art in mechanized tunnelling. The continuous improvement of TBM techniques allows the execution of high quality tunnelling, particularly with regard to maximum safety and efficiency. The practical experience of the construction companies is of essential importance in order to continue further development and improvement.

Jan 1, 2005

By Delon Hampton, Francis K. Mensah-Dwumah

INTRODUCTION The state-of-the art in the area of soil-structure interaction is not sufficiently developed that one can accurately predict the earth load distribution on buried structures. This lack of knowledge has led to the use of high factors of safety in their design and conservative assumptions for the loading diagrams. As a step towards the improvement of the design methodology for buried structures, it is important to be able to apply new analytical techniques and monitor the performance data obtained on full-size buried structures. The performance data should preferably include: 1) the actual stress distribution on the buried structure, 2) stress distribution in the buried structure and surrounding soil media, 3) vertical and lateral movements in the soil adjacent to the buried structure, and 4) deflection of the buried structure. Brown (1967), Davis (1972), Krizek, et al (1974), Krizek and MacQuade (1978), and some few others have compared the performance of full-size culverts with finite element results. Despite all these efforts, a complete understanding of the soil-structure interaction problem has not yet been fully achieved. In an effort to make improvements in the existing design procedures for buried structures constructed in an open-cut, the Department of Environmental Services (DES), Washington, D.C., in conjunction with Howard University, undertook a detailed study of Section II of the Capitol Hill Relief Sewer (CHRS). Inclinometers were used to measure lateral movements of the excavation wall and the total normal interface stresses acting on the concrete sewer were obtained using glotzl total pressure cells. This paper describes the results of the field instrumentation program for acquisition of data, their comparison with the design assumptions, and the results of a series of post-construction finite element analyses of the CHRS project.

Jan 1, 1979

By S J. Clarke, G Sieders

Double corrosion protection (DCP) rock bolts have evolved to become complicated assemblies comprising numerous components. This complexity is mainly associated with durability considerations including potential exposure to adverse groundwater conditions and ensuring separation of dissimilar metals within the bolt assembly itself.Recent progress in the construction of glass-fibre reinforced polymer (GRP) rock bolts have the potential to provide a viable alternative to conventional steel rock bolts in civil tunnelling applications. The durability of the material results in a much simpler bolt detail and permits the use of resin rather than solely cement based grouts.This paper presents the findings of the comparative structural testing of GRP bolts with conventional DCP steel bolts. The axial load performance, including stiffness, ultimate capacity and ductility of bolts are compared. Shear behaviour of bolts is considered, including durability issues associated with damage to the plastic sleeve used in DCP bolts.The paper also considers other issues which are relevant to the design of temporary and permanent rock bolts used in tunnel support, such as initial tensioning and grouting. Long-term performance, including durability and creep are also reviewed.CITATION:Clarke, S J and Sieders, G, 2014. Comparison of glass-fibre reinforced polymer rock bolts with double corrosion protection steel rock bolts for use in tunnel applications, in Proceedings 15th Australasian Tunnelling Conference 2014 , pp 237–246 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By William Gates, Gabe McClain, Thomas Pallua, Joe Schrank

The Tennessee Capitol Corridor connects the Cordell Hull Building (CHB) to the State Capitol, which isa 232-foot-by-124-foot (71 x 38 m) structure in Nashville that includes porticoes built from local massive limestone. This connection was affected by the Capitol Connector Pedestrian Tunnel (CCPT) project, which is part of the overall Cordell Hull State Office Building and Central Services Demolition, New Construction and Renovation Project (Cordell Hull Renovation Project). To construct this connection, the two existing elevator shafts and a new emergency stairwell in the State Capitol were extended down to anew lobby area—the elevators by about 50 feet (15.2 m) and the stairwell by about 60 feet (18.3 m). This lobby was connected to the CHB by a 435-foot-long (133 m) pedestrian tunnel. It was predicted that most of the tunnel would be excavated in a relatively strong limestone; therefore, considering the project features and constraints, drill-and-blast techniques were selected as the primary excavation method. Because of restrictions on blasting in urban areas and, more importantly, the proximity of this construction to national historic landmarks, blasting operations were extensively monitored to measure and correlate ground vibrations as peak particle velocity (PPV), frequency, and strain—these being the major factors that would impact the surrounding buildings. As a result, copious amounts of data were gathered and interpreted within a short time to estimate blasting parameters and optimize the subsequent blast rounds. To calculate the ground response factor, the scaled distance of each shot was compared to the ground vibration as PPV, generating a subsequent regression curve with an R2value of about 0.7. Using the best fit curve equation, the estimated ground response factor was about 150 for the best fit line. Other than some cases with relatively high (> 2 in./sec [51 mm/sec]) recorded PPV values, the blasting operation was successfully conducted as planned and the observed strain on the monitored buildings was very low, mainly within ±2 με (0.0002% elongation). (In general, the recorded PPV was lower than 2 in./sec at frequencies of more than 50 Hz.). The strain gauges at key locations (cold joints and old fractures) in the Capitol and on other critical structures demonstrated strain was insignificant in relationship to ground vibrations from the blasting operations. The apparently small vibration-induced strains were related to the massive limestone construction of the Capitol and ancillary buildings, as the induced strain plus the existing strain did not exceed the critical strain of the massive structures.

By Gabe McClain, Thomas Pallua, Joe Schrank, William C. Gates

Because of restrictions on blasting in urban areas and, more importantly, the proximity of this construction to national historic landmarks, blasting operations were extensively monitored to measure and correlate ground vibrations as peak particle velocity (PPV), frequency, and strain—these being the major factors that would impact the surrounding buildings. As a result, copious amounts of data were gathered and interpreted within a short time to estimate blasting parameters and optimize the subsequent blast rounds

Feb 1, 2020