Ansys Blast

9th International Conference on Fracture & Strength of Solids June 9-13, 2013, Jeju, Korea

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Rock Roadway Parallel Cut Blasting Parameters Optimization Jinzhao Zhuang1,*, Linmei Feng1, Jun Yuan1

College of Water Resources & Civil Engineering, China Agricultural University, Beijing, China

Abstract: Parallel cut is often adopted in rapid excavation construction of rock roadway blasting, blast-effect of cutting holes affects tunnel construction speed directly. In order to get an ideal cut blasting effect, finite element program ANSYS/LS-DYNA is used in this simulation to establish a parallel cut model, analyzing how hole spacing and charge coefficient affect rock roadway parallel cut blasting. The result shows that, when the hole spacing is 165mm and value of charge coefficient is 0.6, the most ideal blast-effect can be obtained. In other words, the ideal parameters of rock roadway parallel cut blasting are 165mm hole spacing and 0.6 charge coefficient. Keywords: parallel cut, numerical simulation, blasting parameters optimization 1. Introduction The main tunnel excavation methods in China are drill-blasting method, new Austria tunneling method (NATM) , shield driven method and so on [1]. More than 85 percent projects in mine tunnel excavation adopt drill-blasting method [2]. Smooth blasting is one of standard methods to control the surrounding over break and under break in tunnel excavation, smooth blasting technique is widely used in tunnel drilling and blasting method construction. Cutting is an important stage of smooth blasting, its the main influencing factor to blasting efficiency, affecting the tunnel excavation footage cycle and the utilization ratio of blast holes. Oblique cut has the drawbacks which itself cannot overcome, parallel cut has the following advantages. In parallel cut , the hole axe is vertical to the working face, when hole depth changes, arrangement of cutting holes can be the same, so its easy to control for operating personnel, several drill machines work simultaneously and mechanization on drilling can be achieved at the same time. Cutting holes are vertical to heading face, hole depth can extend for a long distance along the tunneling direction without the limitation of excavated section. Throw-distance of rock pieces is small and broken stone can centralize in a certain scope, equipment and support in tunnel are not so easy to be smashed [3]. Basing on the above advantages, parallel cut has been more and more widely used in tunnel middle and deep-hole blasting. China University of Mining &Technology[6], the former Xi'an College of Mining & Technology[4~5], Central South University [2], the former Xian college of Science & Technology [7]and other units have conducted researches on the related contents of cylinder cut blasting, they have drawn some conclusions. Many blasting parameters affect parallel cut blast-effect, including the hole depth, the pitch, diameter of hollow hole, charge coefficient, cutting shape and so on. The parameters influence and interact on each other. However, there are less related studies on the optimization of parallel cut blasting parameters. Three-dimension nonlinear dynamic finite element software ANSYS/LS-DYNA is used in this paper to establish a model of cylinder diamond cutting shape with single hollow hole for simulation , discussing effects of hole spacing and charge coefficient on rock roadway parallel cut blasting and obtaining ideal rock roadway parallel cut blasting parameters. 2. Numerical Calculation Model Parameters The parameter selection is the key work for the establishment of cylinder cut blasting model, it affects accuracy of the simulation. Material model in finite element software ANSYS/LS-DYNA can satisfy the requirement of the simulation. 2.1 Rock Parameters Single rock material is used in this model, plastic dynamic model is selected in this paper, and the material model can describe the plasticity property of isotropic, kinematic and mixed hardening. *MAT_PLASTIC_KINEMATIC material is selected to simulate mechanical characteristics of rock .Rock material characteristics are shown in table 1.

Table1 Rock material parameters /kg.m-3 E /Pa Yield strength/Pa Tensile Strength /Pa 2600.0 0.551011 0.27 1.17108 1.2107

*Corresponding author: E-mail: [email protected]; Tel: 86-136-6110-6096


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2.2 Explosive Parameters High energy combustion model is selected to represent explosive. *MAT_HIGH_EXPLOSIVE_BURN is selected to simulate explosive. Explosive performance parameters are shown in table 2.

Table2 Explosive performance parameters /kgm-3 D/ms-1 A/Pa B/Pa R1 R2 E0/Pa PCJ/Pa

1631.0 5600.0 5.4091011 0.941010 4.5 1.1 0.81010 0.35 1.851010 JWL state equation is used to simulate the relationship between pressure and volume strain of explosion during the detonation simulation process. Eq.(1) is JWL state equation.

VE

VRB

VRAP

VRVR ee ++= 21 )1()1(

21

(1)

PPressure, N; EInternal energy per unit of volume of detonation products, J; VVolume of detonation products per unit of volume charge, m3; A, B, R1, R2, Explosive performance parameters, as table 2 shows.

2.3 Calculation Model Cylinder diamond cutting shape with single hollow hole is often used in cylinder cutting. Basing on Literature [8] and combining the selected rock material parameters of this numerical calculation, six charge coefficients are selected for simulation in this paper, they are 0.5, 0.55, 0.6, 0.65, 0.7 and 0.75 respectively. Basing on reference literature [9-11], central distance between blast hole and hollow hole in this paper are selected to be165mm, 180mm, 195mm, 210mm, 225mm and 240mm respectively. Fig.1 is a numerical calculation model of cylinder diamond cutting shape with single hollow hole which is established by ANSYS software.

Fig1. Rock roadway parallel cut blasting numerical calculation model of(a) Plane view of the cutting

model and (b) Three-dimensional meshing view of a quarter cutting model All the hole depth of this simulation computation is 1.5m with hole diameter of 36mm and grain diameter of 32mm. Priming method is simultaneously inverse initiation. Multiply calculations are carried out for different hole spacing and charge coefficients. 3. Numerical Results and Analysis The simulation is in order to get the ideal hole spacing and charge coefficient. The two parameters are correlative, so hole spacing remains the same at first, then simulating blast-effect of different charge coefficients in the hole spacing to get the ideal charge coefficient in the hole spacing. 3.1 Blasting cavity analysis of different charge coefficients in hole spacing of 165mm Blast-effect of different charge coefficients in hole spacing of 165mm is simulated, a series of final blasting cavity are obtained. In order to observe the cut blasting effect, the final blasting cavity section drawings are selected to illustrate blast-effect. The final blasting cavity section shape of different charge coefficients in hole spacing of 165mm are shown in Fig.2.

a b


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0.5 0.55 0.6 0.65 0.7 0.75

Fig 2. Blasting cavity section of different charge coefficient in hole spacing of 165mm It can be seen in Fig.2, when hole spacing is 165mm and value of charge coefficient is less than 0.6, an obvious bottleneck exists in the final blasting cavity, the existence of bottleneck is not conducive to the cast of rock pieces. When value of charge coefficient is larger than 0.55, the final blasting cavity shape becomes funnel-shaped gradually, its conducive to the cast of rock pieces to form a hollow cavity, creating favorable conditions for blasting of avalanche holes. Parameters about blasting cavity volume are recorded during the simulation to observe the developing process of the blasting cavity and get the final blasting cavity volume. The development curve charts of the final blasting cavity of different charge coefficients in the hole spacing of 165mm are shown in Fig.3 respectively.

Fig3. Blasting cavity volume development curve charts of different charge coefficient in hole spacing

of 165mm

It can be seen in Fig.3, blasting cavity volume of different charge coefficients increase faster at the beginning phase, the development of blasting cavity in different charge coefficient begin to flatten at 0.4ms, the final blasting cavity volume in different charge coefficients vary. Comparing with each other, the final blasting cavity volume in charge coefficient of 0.60 is the biggest, which in charge coefficient of 0.50 is the smallest. The final blasting cavity volume of different charge coefficients in hole spacing of 165mm are shown in Fig.4.

Fig 4. Final blasting cavity volume of different charge coefficients in hole spacing of 165mm

It can be seen in Fig.4, blasting cavity increases at first and then decreases along with the increase of charge coefficient in hole spacing of 165mm. When charge coefficient changes from 0.5 to 0.55, the final blasting cavity volume increase a little. The final blasting cavity volume in charge coefficient of 0.60 is much bigger than that in charge coefficient of 0.55, its also the biggest one. When charge coefficient is larger than 0.60, blasting cavity volume almost decreases with the increase of the charge coefficient. Basing on the blasting cavity volume, it can be said that the optimal charge coefficient in hole spacing of 165mm is 0.60.

Time(10-3s)

The final blasting cavity volume (m

3)


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3.2 Blasting cavity analysis of different charge coefficients in other hole spacing Taking the same calculation method as the hole spacing of 165mm, the final blasting cavity of different charge coefficients in hole spacing of 180mm, 195mm, 210mm, 225mm and 240mm are simulated. The final blasting cavity section shape of different charge coefficients in hole spacing of 180mm, 195mm, 210mm, 225mm and 240mm are shown respectively in Fig.5 to Fig.9.

0.5 0.55 0.6 0.65 0.7 0.75

Fig 5. Blasting cavity section of different charge coefficient in hole spacing of 180mm

0.5 0.55 0.6 0.65 0.7 0.75


0.5 0.55 0.6 0.65 0.7 0.75


0.5 0.55 0.6 0.65 0.7 0.75


0.5 0.55 0.6 0.65 0.7 0.75


It can be seen in Fig.5 to Fig.9, when charge coefficient is small, an obvious bottleneck exists in the final blasting cavity in different hole spacing. In hole spacing of 180mm, when value of charge coefficient is smaller than 0.7, an obvious bottleneck exists in the final blasting cavity. When the value of charge coefficient is larger than 0.7, the final blasting cavity shape become ideal funnel-shaped gradually. When hole spacing is 195mm to 240mm and charge coefficient is 0.5 to 0.75, the final


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blasting cavities are always along with bottleneck, its not conducive to the cast of rock pieces to form a hollow cavity. It also can be seen that the bigger hole spacing and the smaller the charge coefficient is, the more serious the bottleneck is. Size of the cut blasting cavity has direct influence on blasting-effect of the follow-up blast holes. Recording the parameters about blasting cavity during the simulation, blasting cavity volume in different hole spacing and charge coefficients can be obtained. The final blasting cavity volume of different charge coefficients in hole spacing of 180mm, 195mm, 210mm, 225mm and 240mm are shown respectively in Fig.10 to Fig.14.

Fig10. Blasting cavity volume of different charge Fig11. Blasting cavity volume of different charge

coefficients in hole spacing of 180mm coefficients in hole spacing of 195mm

Fig 12. Blasting cavity volume of different charge Fig 13. Blasting cavity volume of different charge

coefficients in hole spacing of 210mm coefficients in hole spacing of 225mm

Fig14. Blasting cavity volume of different charge coefficients in hole spacing of 240mm

It can be seen in Fig.10 to Fig.14, in the selected hole spacing, when charge coefficient is small, blasting cavity volume increase with the increase of charge coefficient. When charge coefficient increase to a certain value, increase of blasting cavity volume is not obvious with the increase of charge coefficient. It indicates that charge coefficient and blasting cavity volume are not in a linear relationship, its not uneconomical to get preferable cut blasting effect by increase explosive charge (charge coefficient).Because hole spacing and charge coefficient are correlative, taking the final blasting cavity section drawings (as Fig.6 to Fig.9 shows) of different hole spacing and charge coefficient into consideration, optimal charge coefficient in every selected hole spacing are obtained. The ideal charge coefficient in hole spacing of 180mm, 195mm, 210mm, 225mm and 240mm are 0.7,


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0.7, 0.7, 0.75 and 0.75 respectively. The ideal charge coefficient increase with the increase of hole spacing. 3.3 Result Analysis The purpose of cut blasting is to form ideal blasting cavity and provide favorable condition for the follow-up hole blasting. Using corresponding ideal charge coefficient in different hole spacing can form ideal blasting cavity. In addition to ideal blasting-effect, economic factor is also under consideration in the tunneling blasting engineering, that is taking minimum unit powder consumption into consideration. Calculating explosive charge and the corresponding blasting cavity volume according to the ideal charge coefficient in different hole spacing, the unit powder consumption in ideal charge coefficient of different hole spacing can be obtained. The ideal charge coefficient and the corresponding blasting cavity volume and unit powder consumption in different hole spacing are shown in table3.

Table 3 ideal charge coefficients and corresponding cavity volume and unit powder consumption

of different hole spacing Hole

Spacing/mm Optimal Charge

Coefficient Blasting Cavity

Volume/m3 Unit Powder

Consumption/Kg.m-3 165 0.6 2.112318 2.23556345 180 0.7 1.930445 2.85387996 195 0.7 2.112963 2.60736144 210 0.7 1.765547 3.12042577 225 0.75 1.637266 3.605264 240 0.75 1.451412 4.066919

It can be seen in table3, the unit powder consumption increase with the increase of hole spacing, but blasting cavity volume decrease with the increase of hole spacing. When the hole spacing is 165mm and the charge coefficient is 0.6, the unit powder consumption is the smallest, but blasting cavity volume in the condition is the biggest. So it can be concluded that in the current rock properties, the ideal hole spacing is 165mm and ideal charge coefficient is 0.6 in cylinder cut blasting. 4. Conclusion Using three-dimension nonlinear dynamic finite element software ANSYS/LS-DYNA to establish a model of cylinder diamond cutting shape with single hollow hole for simulation , discussing effects of hole spacing and charge coefficient on rock roadway parallel cut blasting , the following conclusions are obtained: When charge coefficient is small, the final blasting cavity in different hole spacing exist obvious bottleneck. When hole spacing is small but charge coefficient is big, theres no bottleneck in final blasting cavity. Bottleneck become more and more serious with the increase of hole spacing and the decrease of the charge coefficient. When hole spacing is constant, charge coefficient and blasting cavity volume are not in a linear relationship. When charge coefficient is small, the blasting cavity volume increases with the increase of explosive charge. After explosive charge increase to a certain value, the increase of blasting cavity volume is not obvious along with the increase of explosive charge. Ideal charge coefficients in different hole spacing are different, ideal charge coefficients increase with the increase of hole spacing. Synthesizing the blasting cavity shape and volume and unit powder consumption, comparing the blasting cavity of each model, we can draw the conclusion that in the current rock properties, the ideal hole spacing is 165mm and the ideal charge coefficient is 0.6.

Acknowledgement Support for this research by National Science Foundation of China (51279206), and Chinese Doctoral Fund (20100008110010).

References [1] Wu DF. Application of smooth blasting and stemming blocking technology in W u Dao Ling

tunnel drill-blasting method. Highway Tunnel 2011;75(3):58-60. [2] Liu PY, Chen SHR. Design of parallel cut blasting parameter. Mining technology 2005;5(3):65-66. [3] Shan RL, Huang BL, Gao WJ, Zhu Y, Hao XY. Case studies of new technology application of

quasi-parallel cut blasting in rock roadway drivage. Chinese Journal of Rock Mechanics and Engineering 2011;30(2):224-232.


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[4] Zhang Q. From blasting mechanism to see reasonable undercutting way. Hebei Coal 1986;02(014):42-45

[5] Zhang Q, Zhang YM, Luo KL. Parameter calculation for multi-stage blasting with vertical borehole cutting. Rock and Soil Mechanics 1997; 18(2):51-56

[6] Zhang Q, Yang YQ, Jin QK, Yang RS. Study of some aspects of mechanism in straight cut blasting . Journal of China Coal Society 1997;22(03):284-287

[7] Zhang Q, Yang YQ ,Yuan Y F, Wang X L, Lin D C. Study on the factors affecting parallel hole cut blasting. Rock and Soil Mechanics 2001;22(2):144-147.

[8] Zhang Q. Technics research on demolishing technology of improving speed of rock roadway driving. Coal Technology 2008;27(07):61-63.

[9] Fu J G, Xu Y, Hao F, Zhuang XL. Middle-deep bore blasting experimental study on hard rock tunnel heading. Journal of Anhui University of Science and Technology (Nature Science) 2004;24(4):24-27.

[10] Fang XY, Wang Ch. Numerical simulation research of charging optimization in spiral cutting blasting in medium deep bore. Coal Mining Technology 2006;11(4):57-59.

Rock Roadway Parallel Cut Blasting Parameters Optimization2. Numerical Calculation Model Parameters2.1 Rock Parameters2.2 Explosive ParametersTable2 Explosive performance parameters2.3 Calculation Model3. Numerical Results and Analysis3.1 Blasting cavity analysis of different charge coefficients in hole spacing of 165mmFig 2. Blasting cavity section of different charge coefficient in hole spacing of 165mmFig 4. Final blasting cavity volume of different charge coefficients in hole spacing of 165mm3.2 Blasting cavity analysis of different charge coefficients in other hole spacingFig 5. Blasting cavity section of different charge coefficient in hole spacing of 180mmFig 6. Blasting cavity section of different charge coefficient in hole spacing of 195mmFig 7. Blasting cavity section of different charge coefficient in hole spacing of 210mmFig 8. Blasting cavity section of different charge coefficient in hole spacing of 225mmFig 9. Blasting cavity section of different charge coefficient in hole spacing of 240mmFig14. Blasting cavity volume of different charge coefficients in hole spacing of 240mm3.3 Result Analysis4. ConclusionReferences

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