GPGPU 가속 3D FDEM 해석을 활용한 전자지연식 발파의 최적 기폭시차 선정에 관한 연구 = A Study on the Selection of Optimal Initiation Delay in Electronic Blasting Using GPGPU-Accelerated 3D FDEM

다국어 초록 (Multilingual Abstract)

With the widespread adoption of electronic detonators and strengthened safety regulations, millisecond level delay design has become feasible. Nevertheless, field practice still relies largely on empirical settings, and traditional formulas such as the Langefors equation, which were developed under the large timing scatter of legacy detonators, do not adequately reflect the timing precision of modern electronic initiation or the mechanisms governing stress wave interference and crack connectivity in rock. Consequently, it remains difficult to achieve a consistent balance between fragmentation quality and environmental performance across varying rock conditions and scales, and the physical basis for selecting delay times is often unclear. This study treats inter-hole delay as a controllable variable in the fracture process and proposes a mechanistic framework for interpreting and predicting fragmentation responses through the coupled interaction among stress waves, cracks, and blast gas pressure. In addition, fragmentation trends are analyzed as a function of delay time normalized by burden, Δt/B (ms/m), and reference criteria for field application are discussed.
A two-hole PMMA model experiment was first conducted to characterize the time history and representative time scale of crack development, and these observations were used to validate the time scale and crack reproduction of the numerical model. A bench scale three dimensional FDEM model was then developed and coupled with a gas zone model so that gas pressure acts selectively only on crack surfaces that are open and connected to the charge hole. Using this coupled framework, the analysis clarifies how inter-hole delay changes the development of connected and opened fracture paths between holes and the effectiveness of gas pressure action along those paths, and how these changes translate into differences in fragmentation metrics. In the three-hole comparison, simultaneous initiation produced dispersed crack trajectories and distributed gas pressure action, leading to coarser and more heterogeneous fragmentation, with Xmax =1.48 m, D50 =302.6 mm, and a uniformity index n =1.24. With a 5 ms delay, alignment between the growth of cracks formed by the leading hole and the arrival of the shock wave from the subsequent hole promoted early establishment of connected and open pathways, yielding Xmax =1.10 m, D50 =160 mm, and n =2.28, indicating suppression of oversize fragments and improved uniformity. A 10 ms delay showed the most pronounced improvement, with Xmax =0.55 m, D50 =146.4 mm, and n =2.43. As delay time increased, both Xmax and D50 decreased sharply over an initial range and then more gradually, implying that fragmentation enhancement is most strongly expressed within a specific range of Δt/B, beyond which sensitivity to further increases in delay diminishes.

국문 초록 (Abstract)

전자뇌관의 보급과 안전 규제 강화로 지연시차를 ms 단위에서 정밀 설계할 수 있게 되었지만, 현장에서는 여전히 경험적 설정이 지배적이며, Langefors식 등 전통식은 현대 전자기폭의 시간 정밀도와 암반 내 응력파 간섭·균열 연결 메커니즘을 충분히 설명하지 못해 조건·스케일 변화 시 품질·환경의 일관된 균형이 어렵다. 본 연구는 지연시차를 파괴 메커니즘의 제어변수로 재정의하고 응력파, 균열, 가스압 상호작용을 통해 파쇄입도 응답을 해석·예측하는 메커니즘 기반 기준을 제시하고자 하며, 저항선 대비 지연시차 변화에 따른 파쇄 응답 경향을 분석해 현장 적용을 위한 참고 기준을 논의한다.
먼저 PMMA 2공 모형 실험을 통해 균열 전개의 시계열과 스케일을 계측·정리하고, 이를 기준으로 수치모델의 시간 스케일과 균열 재현성을 검증하였다. 이어 벤치발파 규모의 3차원 FDEM을 구축하고 가스존 모델을 결합하여, 장약공과 연결된 개구 균열면에만 가스압이 선택적으로 작용하도록 구성하였다. 이러한 해석을 통해 인접 장약공 간 지연시차가 공 사이 방향의 균열 연결·개구 경로와 가스압 작용의 유효성을 어떻게 바꾸며, 그 결과가 파쇄입도 지표 차이로 이어지는지를 규명하였다. 3공 기폭 비교 결과, 동시기폭은 균열 경로와 가스압 작용이 분산되어 파쇄가 거칠고 불균일했으며 최대입도 1.48 m, 중앙입도 302.6 mm, 균일계수 1.24로 나타났다. 5 ms 지연은 선행 균열 성장과 후행 충격파 도달의 정합으로 연결·개구 경로가 조기 확보되었고, 최대입도 1.10 m, 중앙입도 160 mm, 균일계수 2.28로 대괴 억제와 균일성 향상이 확인되었다. 10 ms 지연은 개선 효과가 가장 두드러져 최대입도 0.55 m, 중앙입도 146.4 mm, 균일계수 2.43을 보였다. 지연시차가 증가함에 따라 중앙입도와 최대입도는 초기 급감 후 완만해지는 경향을 보여 특정 지연시차에서 효과가 두드러지게 발현됨을 확인하였다.

목차 (Table of Contents)

• 1. Introduction 1
• 1.1. Research Background and Motivation 1
• 1.2. Research Objectives and Scope 7
• 2. Theoretical Background and Literature Review 9
• 2.1 Electronic-Delay Blasting and Initiation Delay Theory 10
• 2.1.1 Concept of Delay Blasting and Characteristics of Electronic-Delay Blasting 10
• 2.1.2 Definition and Classification of Initiation Delays 12
• 2.1.3 Mechanisms of delay-time effects on rock fragmentation 13
• 2.2 GPGPU-Based Parallel FDEM Analysis Method 19
• 2.2.1 Overview of Numerical Analysis 19
• 2.2.2 Fundamentals of FDEM and Governing Equations 21
• 2.2.3 3D FDEM Analysis Procedure and Definition of Crack States 26
• 3. Crack-Control Simulation of Laboratory-Scale Blasting Using a Dynamic FDEM Method 28
• 3.1 Research Overview 28
• 3.2 Laboratory-Scale Blasting Experiments with Precise Delay Control 29
• 3.2.1 Experimental Setup and Instrumentation System 29
• 3.2.2 Analysis of Crack-Propagation Behavior Under Different Delay Conditions 32
• 3.3 3D FDEM Numerical Methodology 35
• 3.3.1 3D FDEM Analysis Framework 35
• 3.3.2 Constitutive Model and Failure Model Settings 35
• 3.3.3 Blast Loading and Numerical Analysis Settings 37
• 3.4 Experimental Validation of In-Hole Wave-Propagation Timing and Crack Velocity 40
• 3.5 Transition in Stress-Wave Interferen ce and Crack-Propagation Behavior with Delay Time 45
• 4. Three-Hole Delay Bench-Blasting Analysis Using an In-Crack Gas-Zone Model 53
• 4.1 Analysis Overview and Research Workflow 53
• 4.2 Configuration of a 3D FDEM Model Coupled with a Gas-Zone Model 54
• 4.3 Comparison of Pressure Profiles for Verification of the Gas-Pressure Algorithm 63
• 4.4 Comparison of Crack Development and Failure Behavior Under Three-Hole Delay Conditions 71
• 4.5 Evaluation of Fragmentation by Delay Condition and Analysis of Delay-Ratio Trends 80
• 5. Discussion 85
• 6. Conclusions 89
• References 93
• Acknowledgment 97