Abstract
In the blasting construction of underground engineering in layered rock mass, the mechanism of cut blasting and the propagation law of blasting vibration waves are very complex. In this paper, a new method for predicting the blasting vibration velocity of layered rock mass under multihole cut blasting is proposed. The key steps include determining the equivalent elastic boundary and load, establishing the multidegree freedom model of blasting vibration and its motion differential equation, and solving the motion differential equation by time-history analysis method. Two multihole cut blasting tests of different schemes were carried out in the construction site of layered rock mass, and the measured results of blasting vibration waves were obtained. By comparing the time-history curves of the predicted and measured blasting vibration velocity, it can be seen that the time-history curves predicted by the proposed method can reflect the characteristics and attenuation law of blasting vibration waves, and the predicted waveforms are similar to the measured waveforms. By using the proposed method, the prediction accuracy for the peak velocity of blasting vibration in the two tests is 93% and 94%, respectively, and the prediction accuracy for the dominant frequency of blasting vibration in the two tests is 86% and 94%, respectively. The prediction accuracy of the main characteristic parameters of blasting vibration waves is high. So it can be proved that the prediction method proposed in this paper is feasible in effectiveness and accuracy, which can provide important theoretical guidance for the optimization of blasting design and the control of blasting vibration in underground engineering in layered rock mass.
Highlights
Most underground projects are related to layered rock mass. e mechanism of cut blasting and the propagation law of blasting vibration waves in layered rock mass with different physical and mechanical properties are very complex. e above research results are generally put forward on the assumption that the propagation medium is simplified as the same type of rock mass, which have great limitations when directly applied to blasting engineering in layered rock mass of different types and thicknesses. e existing models of blasting vibration caused by cut blasting have large prediction errors in practical underground engineering applications, so they cannot effectively optimize blasting parameters and control blasting vibration
A new method for predicting the vibration velocity caused by multihole cut blasting in layered rock mass is proposed. e key steps of the method include determining the equivalent elastic boundary and load, establishing the multidegree freedom model of blasting vibration and its motion differential equation, and solving the motion differential equation by time-history analysis method. e effectiveness and accuracy of the proposed method are proved by the field test results. is paper is organized as follows: In Section 2, the equivalent elastic boundary and load of single-hole and multihole cut blasting are determined, respectively
Compared with the existing models based on simplifying layered rock mass to single rock mass, the method proposed in this paper, which is based on simplifying layered rock mass to multilayer rock mass of different types and thicknesses, is closer to the actual model
Summary
Where p(t) is the blasting load acting on the hole wall; r0 is the radius of the cut hole; r1 is the radius of the crushed zone; r2 is the radius of the fracture zone; μ is Poisson’s ratio of rock mass. Each rock layer is regarded as a particle, and its gravity load is concentrated on the mass centre Where rL0 is the distance from the interface of rock layers L0 and L1 to the centre of the equivalent elastic boundary of multihole cut blasting. Where rLi is the distance from the interface of rock layers Li and Li+1 to the centre of the equivalent elastic boundary of multihole cut blasting; and ρi is the density of rock layer Li. 3.2. According to D’Alembert’s principle [30, 31], the following motion differential equation for the multidegree freedom model of layered rock mass under multihole cut blasting is established: hn hi h2 h1. Test 1. ree cut holes are arranged in an equilateral triangle, the hole distance is 35 cm, the hole diameter is 40 mm, the charge diameter is 32 mm, the hole depth is
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