Optimization of discharge circuit model based on electro pulse boring experiment

https://doi.org/10.1016/j.jngse.2020.103730Get rights and content

Highlights

  • The optimized discharge circuit model of EPB was established.

  • An experimental EPB system and electrode bit of 25 mm spacing were developed.

  • The process and law of rock-breaking by EPB in different rocks were obtained.

  • The identification method of unconstrained nonlinear optimization least square was developed.

  • The accuracy of the optimized model and parameter identification was proved.

Abstract

High-voltage electro pulse rock-breaking is a green breaking technology, which can achieve high efficiency of rock-breaking. It has a wide application prospect in deep and ultra-deep well drilling and tunnel driving in the future. Pursuant to the time delay characteristics of the gas discharge switch in the electro pulse boring (EPB) system, the equivalent model of the discharge circuit is established based on the time-varying resistance model. With this model, the real-time parameters such as voltage, current and discharge energy can be predicted in the EPB process of different rocks. In line with the arrangement of coaxial cylindrical electrodes, a 25 mm electrode drill bit is designed, and an EPB experiment system is developed based on the transformer step-up pulse power supply. The electro pulse breaking of red sandstone, yellow sandstone, concrete and granite, and the complete drilling of 60 mm diameter in red sandstone and concrete are realized, and EPB rules of different rocks are obtained. The real-time curves of electrical parameters in different rocks are collected by electrical parameter tester. The model parameters are identified based on the least square method of unconstrained nonlinear optimization. The current curve fitted by the identification parameters and the current curve obtained from the experiment are featured in high coincidence and good follow-up, which proves the accuracy of the optimized model and parameter identification. The optimization of the discharge circuit model and the identification of the model parameters based on EPB experiment are of great significance to guide the selection of the technological parameters of EPB, improve the efficiency of rock-breaking and reduce the energy loss in the drilling process.

Section snippets

Credit author statement

Changping Li: Conceptualization, Data curation, Methodology, Software, Writing – original draft; Longchen Duan: Conceptualization, Project administration; Laijie Wu: Data curation, Investigation; Songcheng Tan: Formal analysis, Data curation; Jun Zheng: Investigation; Victor Chikhotkin:Conceptualization

Discharge circuit model of EPB based on time-varying resistance model

The pulse power supply in EPB generally adopts the capacitance as the energy storage component. The equivalent discharge circuit of EPB is shown in Fig. 1 when the transformer-type pulse power supply is used. It mainly includes electrical circuit time-varying resistance Rt, energy storage capacity C, inductive inductance L, discharge switch S and rock discharge channel resistance Rtd. The inductive inductor includes the inductor generated by the capacitor, the connecting wire and the discharge

Model parameter identification method of least squares for unconstrained nonlinear optimization

The off-line parameter identification method of the discharge circuit model of EPB adopts the voltage and current data, and obtains the parameters of the circuit model through the centralized processing. Among them, the off-line parameter identification methods of the discharge circuit model of EPB can be divided into maximum likelihood estimation, exponential fitting in continuous time domain and recursive least square fitting (Sun et al., 2007; Guo et al., 2016).The traditional parameter

EPB rock-breaking experiments

In order to carry out EPB experiments on different rocks and collect the current parameters in the circuit during the process of EPB, an EPB experiment system is built, as shown in Fig. 3. It mainly includes EPB experiment platform, electrical parameter detection device and transformer step-up type high-voltage pulse power supply. The pulse power supply in the system is developed by He et al. (2013).The system can be used to test EPB effect and electrical parameters when drilling in different

EPB effects and electrical parameter curves of different rock samples

The effect diagrams of EPB in different rocks are shown in Fig. 7. The process and effect parameters of EPB in different rocks are shown in Table 1. It can be concluded that concrete and red sandstone have achieved the drilling of 60 mm full hole diameter under the same discharge parameter setting, when discharging times are 120 times. However, yellow sandstone and red sandstone have not yet completed the drilling of 60 mm full hole diameter. The breaking volume of concrete is 113.04 cm3 and

Conclusions

The equivalent discharge circuit model of EPB based on the variable resistance model is established. EPB experiments on different rocks are made, and EPB rules of different rocks are obtained. Combined with the electrical parameter curve collected in EPB experiment, the parameter identification of the model is carried out based on the least square method of unconstrained nonlinear optimization, the correctness of the optimized model is verified, and the following conclusions are drawn:

  • (1)

    Based on

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (42002310; 41972327; 41672364) and External Cooperation Program of Science and Technology Department of Hubei Province (2019AHB051). Thanks to professor He Mengbing in Huazhong University of Science and Technology for providing the high-voltage pulse power supply in the process of EPB experiment.

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