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1

Experimental study of the effect of rock blasting with various cutting forms for tunnel excavation using physical model tests

An Huaming, Song Yushan, Yang Deqiang

Archives of Civil Engineering

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2021

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Vol. 67, nr 3

599--618

EN

Cutting blasting has been widely used for tunnel excavation. The cutting forms significantly influence the blasting effect. This research focuses on the study of the relationship between cutting forms and blasting effects. Similarity theory is proposed for the experimental study of the rock blasting using small models. Then four experimental modes with different cutting forms are used to study the blasting effect due to the cutting forms. The cutting depth, borehole utilization rate, fragments volume, and average fragment size are analysed. The blasting effects with various cutting forms are compared. The influences of the borehole space and the blasting delay are discussed. It is concluded that the spiral cutting form can produce more fragments and is recommend for the small section tunnel excavation.

2

Experimental study on radial decoupling charge blasting with air and water

Yang Deqiang, An Huaming, Lei Zhen

Mining Science

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2020

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Vol. 27

265--281

EN

In order to investigate the effects of the different medium on the initial impact pressure and fragmentation of the hole wall under radial decoupling charge, this paper analyzes and compares the initial impact pressure of hole wall and the size of blasting lumpiness theoretically when air and water are used as a coupling medium. Combined with blasting model test, strain datas are collected by high-speed multi-channel dynamic stress testing system, and the lumpiness of the model test is sieved and measured. The blasting lumpiness is analyzed by G–G–S distribution function. The results show that compared with the air radial decoupling charge, the water radial decoupling charge has higher blasting peak pressure and more uniform lumpiness. According to the relation between peak strain pressure and decoupling coefficient, the optimal decoupling coefficients of air and water are 1.71 and 1.67, respectively. The results show that the best blasting effect can be achieved by using a small hole diameter of water-decoupling charge compared with air-decoupling charge. When the decoupling coefficient is 1.50, the average lumpiness size, distribution of large block and boulder yield of blasting lumpiness in water-decoupling medium are minimum, and only the average lumpiness size and distribution of large block are minimum in airdecoupling medium. Applying the test results to the smooth blasting of cutting has certain guiding significance for improving the blasting effect.

3

Analysis of explosion stress field of air radial decoupling charge

Yang Deqiang, Lei Zhen, An Huaming

Mining Science

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2020

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Vol. 27

19--38

EN

In order to study the effect of air radial decoupling charge on blasting excavation effect of slope, the effect of radial decoupling coefficient on explosive stress field in rock mass is analyzed theoretically. ANSYS/LS-DYNA software is used to establish a numerical model for stress monitoring of monitoring points. At the same time, the concrete model is poured, the explosion stress field around the blast hole is measured by means of the high-speed multi-channel dynamic stress testing system, and the monitoring results of the two methods are compared with the theoretical analysis results. The results show that with the increase of the radial decoupling coefficient of blasting, the peak value of explosive stress at the same side point decreases obviously, and with the increase of the distance, the stress attenuation becomes slower. Applying the test results to the blasting of slope, it is found that the blasting effect is the best when the aperture decoupling coefficient is 2.75 and the hole spacing is 1.0 m, and the larger the hole spacing is, the less obvious the blasting crack is, which has certain guiding significance for improving the blasting effect.