Face destressing blast design for hard rock tunnelling at great depth

2018 ◽  
Vol 80 ◽  
pp. 257-268 ◽  
Author(s):  
Christopher Drover ◽  
Ernesto Villaescusa ◽  
Italo Onederra
Keyword(s):  
Hard Rock ◽  
Great Depth ◽  
Blast Design

scholarly journals An in situ monitoring campaign of a hard rock pillar at great depth within a Canadian mine

2020 ◽  
Vol 12 (3) ◽  
pp. 427-448
Author(s):  
Bradley Forbes ◽  
Nicholas Vlachopoulos ◽  
Mark S. Diederichs ◽  
Andrew J. Hyett ◽  
Allan Punkkinen
Keyword(s):  
Hard Rock ◽  
Great Depth ◽  
In Situ Monitoring ◽  
Monitoring Campaign ◽  
Rock Pillar

Rockburst response in hard rock owing to excavation unloading of twin tunnels at great depth

2021 ◽  
Author(s):  
Fan Feng ◽  
Xibing Li ◽  
Lin Luo ◽  
Xingdong Zhao ◽  
Shaojie Chen ◽  
...  
Keyword(s):  
Hard Rock ◽  
Great Depth ◽  
Twin Tunnels

Damage threat to sensitive structures of a thermal power plant from hard rock blasting operations in track hopper area: A case study

2019 ◽  
Vol 11 (1) ◽  
pp. 3-22 ◽  
Author(s):  
Rakesh Kumar Singh ◽  
Chhangte Sawmliana ◽  
Panchanan Hembram
Keyword(s):  
Power Plant ◽  
Thermal Power Plant ◽  
Design Patterns ◽  
Hard Rock ◽  
Thermal Power ◽  
Ground Vibration ◽  
Dominant Frequency ◽  
Frequency Content ◽  
Blast Design ◽  
Excavation Work

The article deals with the development of controlled blast design patterns and methodologies for excavation of hard rock for foundation work of a track hopper in a running thermal power plant in close proximity of many sensitive structures. Test blasts were conducted with different blast geometries and charge loading patterns at selected locations. The results of the test blasts were analysed to evolve safe controlled blast design patterns and methodologies for completing the total excavation work. The threshold value of vibration for the safety of various structures/foundations present has been taken as 25 mm/s based on the dominant frequency content as well as guidelines from the regulatory authority. The dominant frequency content of the ground vibration waves was in the range of 10–40 Hz. Controlled blast design parameters, namely maximum explosive per delay, size of the blasts and blast geometry were formulated based on established ground vibration predictor equation and nearness of structures concerned from the blasting point. Two blasting zones were classified for safe excavation work. For the first zone within 20 m from the structures, controlled blasting using 32-mm diameter blast holes with small blast geometry was suggested, whereas for the second zone beyond 20 m, controlled blasting with 100-mm diameter holes with lesser hole depth and limited number of holes was suggested. The whole excavation work in the track hopper area was completed safely without causing any damage to the nearby sensitive structures of the running thermal power plant.

Investigations on Impact of Blasting in Tunnels

2010 ◽  
Vol 1 (2) ◽  
pp. 59-71 ◽  
Author(s):  
Kaushik Dey ◽  
V. M. S. R. Murthy
Keyword(s):  
Hard Rock ◽  
Vibration Monitoring ◽  
Multivariate Statistical ◽  
Engineering Controls ◽  
Blast Design ◽  
Metal Mines ◽  
Multivariate Statistical Model ◽  
Selection For ◽  
Smooth Blasting ◽  
First Time

Blasting with longer advance per round leaves an impact both visible (in the form of overbreak) and invisible (cracks) in the surrounding rockmass, however, a number of controlled-blasting techniques, that is line drilling, pre-splitting, and smooth blasting, have been developed to minimise this problem. These techniques require additional drilling, controlled charging, and detonation, and thus, are not preferred in regular development activities. Investigations have been carried out in five different horizontal development drivages of metal mines to assess the blasting impact using burn cut and arrive at the blast-induced rock damage (BIRD) model. Vibration monitoring close to the blast was carried out using accelerometers for the first time in India to develop vibration predictors and overbreak threshold levels for individual sites. This paper reports the development of the overbreak predictive model (BIRD) for burn cut blasting in hard rock drivages by combining the relevant rock, blast design, and explosive parameters. A multivariate statistical model has been developed and validated and the same can find ready application in tunnels and mines for exercising suitable engineering controls both in blast design and explosive selection for reduced basting impacts.

The Broad Applications of the Scanning Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 20-21
Author(s):  
C. T. Nightingale ◽  
S. E. Summers ◽  
T. P. Turnbull
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Light Microscopy ◽  
Surface Topography ◽  
Great Depth ◽  
Resolving Power ◽  
Depth Of Field ◽  
Pictorial Representations ◽  
Scanning Electron

The ease of operation of the scanning electron microscope has insured its wide application in medicine and industry. The micrographs are pictorial representations of surface topography obtained directly from the specimen. The need to replicate is eliminated. The great depth of field and the high resolving power provide far more information than light microscopy.

Visualization of Internal Skin Structures with the Scanning Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 46-47
Author(s):  
Emil Bernstein
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Great Depth ◽  
Hair Follicles ◽  
Depth Of Field ◽  
Pig Skin ◽  
Realistic Picture ◽  
Main Components ◽  
Scanning Electron

An interesting method for examining structures in g. pig skin has been developed. By modifying an existing technique for splitting skin into its two main components—epidermis and dermis—we can in effect create new surfaces which can be examined with the scanning electron microscope (SEM). Although this method is not offered as a complete substitute for sectioning, it provides the investigator with a means for examining certain structures such as hair follicles and glands intact. The great depth of field of the SEM complements the technique so that a very “realistic” picture of the organ is obtained.

Record Wear Studies by Scanning Electron Microscopy

1968 ◽  
Vol 26 ◽  
pp. 364-365
Author(s):  
M.D. Coutts ◽  
E.R. Levin ◽  
J.G. Woodward
Keyword(s):  
Electron Microscopy ◽  
Constant Velocity ◽  
Peak Velocity ◽  
Great Depth ◽  
Depth Of Focus ◽  
Sweep Frequency ◽  
Transmission Electron ◽  
Test Record ◽  
Lateral Mode ◽  
Scanning Electron

While record grooves have been studied by transmission electron microscopy with replica techniques, and by optical microscopy, the former are cumbersome and restricted and the latter limited by lack of depth of focus and resolution at higher magnification. With its great depth of focus and ease in specimen manipulation, the scanning electron microscope is admirably suited for record wear studies.A special RCA sweep frequency test record was used with both lateral and vertical modulation bands. The signal is a repetitive, constant-velocity sweep from 2 to 20 kHz having a duration and repetitive rate of approximately 0.1 sec. and a peak velocity of 5.5 cm/s.A series of different pickups and numbers of plays were used on vinyl records. One centimeter discs were then cut out, mounted and coated with 200 Å of gold to prevent charging during examination. Wear studies were made by taking micrographs of record grooves having 1, 10 and 50 plays with each stylus and comparing with typical “no-play” grooves. Fig. 1 shows unplayed grooves in a vinyl pressing with sweep-frequency modulation in the lateral mode.

AISI 3150

Alloy Digest ◽  
1963 ◽  
Vol 12 (3) ◽  
Keyword(s):  
Fracture Toughness ◽  
Physical Properties ◽  
Tensile Properties ◽  
Nickel Alloy ◽  
Elastic Properties ◽  
Alloy Steel ◽  
Heat Treating ◽  
Great Depth ◽  
Medium Carbon ◽  
Steel Mills

Abstract AISI 3150 is a medium carbon, chromium-nickel alloy steel having great depth hardness, high elastic properties and excellent fatigue resistance and toughness. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on heat treating and machining. Filing Code: SA-143. Producer or source: Alloy steel mills and foundries.

THE LANDSCAPE INVESTIGATIONS AS NECESSARY PART OF BIOLOGICAL STUDY IN THE COASTAL ZONE TO THE QUESTION OF THE IMPACT OF CLIMATE CHANGE ON THE ECOLOGICAL STATE OF ARTIFICAL

2017 ◽  
Author(s):  
Artem Lapenkov ◽  
Artem Lapenkov ◽  
Yury Zuyev ◽  
Yury Zuyev ◽  
Nadezhda Zuyeva ◽  
...  
Keyword(s):  
Coastal Zone ◽  
Benthic Communities ◽  
Great Depth ◽  
Research Strategy ◽  
Biological Study ◽  
Lake Ladoga ◽  
Coastal Zones ◽  
Investigation Methods ◽  
Ground Conditions ◽  
The Impact

Coastal zones have great diversity of resources. The shallow water zones contain the most of plant and benthic communities. A description of relief and type of ground is needed for the rigorous monitoring of biota and environmental condition of coastal zone. Generally, on the basis of these data the investigation methods of the coastal zone are selected. The shallows research strategy has been developed by us for northern part of the Lake Ladoga. If the coastal areas are characterized by great depth and flat topography, then sonar’s can be used to describe them and samples of ground can be taken by bottom grabs. In the Lake Ladoga these methods don’t operate correctly by reason of the compound bottom relief and the fact that a sizeable part of the bottom is occupied by hard ground. Therefore, our investigations base on the diving transect method of Golikov and Skarlato (1965). A diver moves along transects. He registers the depth, length to coastline, water temperature, relief and ground, edificators and records video. In the laboratory all these data are decoded and used for mapping of bays. Studies of plant communities have been performed and strategy for research of benthic communities in complex relief and hard ground conditions has been developed based on the descriptions of shallow waters. Description of the Malay Nikonovskia Bay bottom has given an opportunity to estimate changes in the bottom of the bay under the influence of the trout farm.

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