A Study on Cut Blasting with Large Diameter Charges in Hard Rock Roadways

To overcome the problems of poor cutting effects in hard rock roadways, a cut blasting technique with large diameter charges was developed; that is, the cut holes employ 50 mm diameter blast holes and 45 mm diameter explosive sticks, while the other holes adopt 42 mm diameter blast holes and 35 mm diameter explosive sticks. First, the effect of charge diameter on damage range and cut cavity formation was analyzed. Next, simulation of wedge cut for different charge diameters was conducted to reveal the stress wave developments and compare the stress field intensities. Finally, field tests were conducted to verify the viability of this technique. The results indicate that large diameter charges can increase the damage range around cut holes to improve the fragmentation degree of the rock mass in the cut cavity and significantly enhance the cavity formation power to better expel the rock mass fragments. The stress wave evolution of wedge cut was visualized using numerical simulations, which confirmed that the use of large diameter charges in cut holes increases the stress field intensity in the cut cavity and hence increases the damage degree of the rock mass. In this study, the use of a large diameter charge for cut blasting increased the average footage by 0.30 m, and the average utilization rate of blast holes increased by 12.5%. Therefore, the cutting effects in hard rock roadways can be improved by using large diameter charges, which increase the blasting footage and the utilization rate of blast holes.

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Comparison Among Wave Velocities from Seismic Observation Waves and Field Tests for Hard Rock Mass.

Doboku Gakkai Ronbunshu ◽

10.2208/jscej.1997.568_161 ◽

1997 ◽

pp. 161-173

Author(s):

Masatoshi Sato ◽

Minoru Ueda ◽

Norio Hasebe ◽

Hiromichi Kondo

Keyword(s):

Rock Mass ◽

Hard Rock ◽

Field Tests ◽

Seismic Observation ◽

Wave Velocities

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Analysis of the Cavity Formation Mechanism of Wedge Cut Blasting in Hard Rock

Shock and Vibration ◽

10.1155/2019/1828313 ◽

2019 ◽

Vol 2019 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Zhongkang Wang ◽

Xiaowei Gu ◽

Wenlong Zhang ◽

Qiankun Xie ◽

Xiaochuan Xu ◽

...

Keyword(s):

Theoretical Model ◽

Formation Mechanism ◽

Hard Rock ◽

Field Tests ◽

Stress Waves ◽

Cylindrical Charge ◽

Cavity Formation ◽

Failure Zone ◽

Break Rock ◽

Total Resistance

The basic process of cut blasting is to break rock, throw fragments, and form a cavity. Based on the characteristics of cut blasting and the combined effect of stress waves and detonation gas, the evolution process of wedge cut blasting is divided into two stages, and a theoretical model is proposed to investigate the cavity formation mechanism by theoretical analysis and field tests. In phase one, rock breaking is caused by stress waves. By considering the dynamic strength of the rock, a computational model is built for the rock failure zone derived from the coupled cylindrical charge explosion. In phase two, the driving force of the detonation gas overcomes the total resistance of the surrounding rock mass, accelerates fragments, and then throws fragments to form a cavity. The criterion of cavity formation is established on the basis of the quasi-static loading of the detonation gas. The theoretical model provides an overall interpretation of the cavity formation mechanism, in which stress waves break rock and detonation gas throws fragments. A specific case indicates that the range of the failure zone is approximately 18 times the borehole radius in granite and that the hole-bottom spacing of the wedge cut can be designed as 50 cm; in addition, detonation gas is sufficient to overcome the total resistance, accelerate rock fragments, throw fragments, and form a cavity. Field tests present favourable blasting results, with a high utilization rate of boreholes and uniform fragment sizes. Therefore, the model could provide theoretical support and technical guidance for wedge cut blasting in hard rock.

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SURVEY OF HARD ROCK MASS FOR THE PURPOSE OF SUSTAINABILITY IN ORDER TO ELIMINATE THE ACCIDENT CONSEQUENCES

Фундаментальные и прикладные вопросы горных наук ◽

10.15372/fpvgn2019060119 ◽

2019 ◽

Vol 6 (1) ◽

Keyword(s):

Rock Mass ◽

Hard Rock

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Evolution Pattern and Matching Mode of Precursor Information about Water Inrush in a Karst Tunnel

Water ◽

10.3390/w13111579 ◽

2021 ◽

Vol 13 (11) ◽

pp. 1579

Author(s):

Jie Song ◽

Diyang Chen ◽

Jing Wang ◽

Yufeng Bi ◽

Shang Liu ◽

...

Keyword(s):

Rock Mass ◽

Stress Field ◽

Displacement Field ◽

Water Inrush ◽

Seepage Field ◽

Karst Tunnel ◽

Rock Mass Structure ◽

Evolution Pattern ◽

Water Blocking ◽

Precursor Information

The water inrush of the Shangjiawan karst tunnel is used to study the evolution pattern of precursor water inrush information in water-filled caves and to further reveal the matching mode of the information. The three-dimensional numerical method FLAC3D was used to simulate the evolution process of water inrush after damage to a water-blocking rock mass structure in a water-filled cave and to obtain the evolution pattern of precursor water-inrush information caused by the damage. The results show that the multifield response to the characteristic precursor information of the water-inrush pattern after the fracture of the water-blocking rock mass follows the order of stress-field displacement-field seepage-field. Further, the matching pattern of the information shows that the stress field increased first and then decreased, the displacement field always increased, and the seepage field increased first and then decreased.

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Examining Feasibility of Developing a Rock Mass Classification for Hard Rock TBM Application Using Non-linear Regression, Regression Tree and Generic Programming

Geotechnical and Geological Engineering ◽

10.1007/s10706-017-0380-z ◽

2017 ◽

Cited By ~ 5

Author(s):

A. Salimi ◽

J. Rostami ◽

C. Moormann ◽

J. Hassanpour

Keyword(s):

Rock Mass ◽

Linear Regression ◽

Hard Rock ◽

Regression Tree ◽

Rock Mass Classification ◽

Generic Programming ◽

Non Linear ◽

Mass Classification ◽

Hard Rock Tbm

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Rockslides on limestone cliffs with subhorizontal bedding in the southwestern calcareous area of China

Natural Hazards and Earth System Science ◽

10.5194/nhess-14-2627-2014 ◽

2014 ◽

Vol 14 (9) ◽

pp. 2627-2635 ◽

Cited By ~ 7

Author(s):

Z. Feng ◽

B. Li ◽

Y. P. Yin ◽

K. He

Keyword(s):

Numerical Modeling ◽

Rock Mass ◽

Hard Rock ◽

Compression Fracture ◽

Field Observations ◽

Mountainous Areas ◽

Hard Rocks ◽

Rupture Plane ◽

Rock Collapse ◽

Cliff Retreat

Abstract. Calcareous mountainous areas are highly prone to geohazards, and rockslides play an important role in cliff retreat. This study presents three examples of failures of limestone cliffs with subhorizontal bedding in the southwestern calcareous area of China. Field observations and numerical modeling of Yudong Escarpment, Zengzi Cliff, and Wangxia Cliff showed that pre-existing vertical joints passing through thick limestone and the alternation of competent and incompetent layers are the most significant features for rockslides. A "hard-on-soft" cliff made of hard rocks superimposed on soft rocks is prone to rock slump, characterized by shearing through the underlying weak strata along a curved surface and backward tilting. When a slope contains weak interlayers rather than a soft basal, a rock collapse could occur from the compression fracture and tensile split of the rock mass near the interfaces. A rockslide might shear through a hard rock mass if no discontinuities are exposed in the cliff slope, and sliding may occur along a moderately inclined rupture plane. The "toe breakout" mechanism mainly depends on the strength characteristics of the rock mass.

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General concept of determining the parameters of non-mining walls of ultra-deep diamond deposits development open pits

Gornyi Zhurnal ◽

10.17580/gzh.2021.02.05 ◽

2021 ◽

pp. 48-53

Author(s):

I. V. Zyryanov ◽

A. N. Akishev ◽

I. B. Bokiy ◽

N. M. Sherstyuk

Keyword(s):

Rock Mass ◽

Structural Relaxation ◽

Slope Angle ◽

Field Tests ◽

Friction Angle ◽

Strength Properties ◽

Strength Characteristics ◽

Open Pit ◽

Open Pit Mining ◽

Relaxation Coefficient

A specific feature of open pit mining of diamond deposits in Western Yakutia is the construction of the open pits in the zone of negative ambient temperatures, which includes thick permafrost rock mass, and which is at the same time complicated by the influence of cryogenic processes on deformation of pit wall benches. The paper presents the comparative analysis of strength characteristics in frozen and thawed rocks, stability of benches during mining, the general geomechanical approach to the determination of parameters of non-mining walls of the ultra-deep open pit diamond mines, and the parameters of nonmining walls and benches. Optimization of open pit wall configuration should primarily be based on the maximum utilization of the strength properties of frozen rocks in combination with the development of new approaches, calculation schemes and methods for assessing stability of open pit walls and benches of unconventional design, including the non-mining vertical benches. The main design characteristic that determines the parameters of open pit walls is the structural tectonic relaxation coefficient, which specifies the calculated value of cohesion in rock mass. For the diamond deposits, the values of the structural relaxation coefficient were obtained in a series of field tests and back calculations. Full-scale tests were carried out both during exploration operations in underground mines and in open pits. The accuracy of determining the values of the structural relaxation coefficient in the range of 0.085–0.11 is confirmed by the parameters of non-mining walls in an open pit mine 385–640 m deep, with overall slope angles of 38–55° and a steeper H 0.35–0.5 lower part having the slope angle of up to 70° with average strength characteristics of 7.85–11.84 MPa and the internal friction angle of 28.1–37.4°. Using the natural load-bearing capacity of rock mass to the full advantage, which the values of the structural relaxation coefficient of deposits show, allows optimization of open pit wall slope design and minimization of stripping operations.

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Photoelastic simulation of the stress wave field around a tunnel in an anisotropic rock mass subject to shock load

International Applied Mechanics ◽

10.1007/s10778-006-0164-2 ◽

2006 ◽

Vol 42 (8) ◽

pp. 948-950 ◽

Cited By ~ 7

Author(s):

M. P. Malezhik ◽

I. S. Chernyshenko ◽

G. P. Sheremet

Keyword(s):

Rock Mass ◽

Wave Field ◽

Stress Wave ◽

Shock Load ◽

Anisotropic Rock ◽

Anisotropic Rock Mass

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Study on Failure of Rock Mass around Deep Tunnel

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.99-100.370 ◽

2011 ◽

Vol 99-100 ◽

pp. 370-374 ◽

Cited By ~ 1

Author(s):

Yue Hong Qian ◽

Ting Ting Cheng ◽

Xiang Ming Cao ◽

Chun Ming Song

Keyword(s):

Rock Mass ◽

Stress Field ◽

Failure Modes ◽

Shear Failure ◽

Simple Function ◽

Tensile Failure ◽

Deep Tunnel ◽

Main Mode

During excavating the problem of unloading is a dynamic one essentially. Assuming the unloading ruled by a simple function and based on the Hamilton principal, the distribution of the stress field nearby the tunnel is obtained. The characteristics of the failure nearby the tunnel are analyzed considering the shear failure and tensile failure. The results show that the main mode of the shear failure, intact and tensile failure occurs from the tunnel. The characteristic of the shear failure, intact and tensile failure are one of the likely failure modes.

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