Simangunsong Ganda Marihot, Prassetyo Simon Heru, Pinem Riadi Simka
Mining Engineering Study Program, Institut Teknologi Bandung, Bandung, Indonesia.
PT. Borneo Indo Bara, Tanah Bumbu Regency, South Borneo Province, Indonesia.
Sci Rep. 2024 Dec 2;14(1):29890. doi: 10.1038/s41598-024-81784-2.
Bench blasting is commonly used in open-pit coal mines because it effectively increases coal production and aids in overburden removal. However, uncontrolled blasting can generate significant vibrations and accelerations, which may lead to slope failure if the magnitude of permanent displacement exceeds its critical value. A prevalent method for calculating the dynamic factor of safety (FoS) of a slope due to blasting is the pseudo-static approach; however, this method tends to be overly conservative. In this study, we utilized Newmark's sliding block method and the strength reduction factor (SRF) to assess the dynamic FoS of slopes by evaluating the permanent displacement caused by bench blasting. We based our seismic input on a complete vibration waveform obtained through signature hole analysis of a specific bench blast design. The dynamic FoS was defined as the SRF threshold that resulted in a critical slope displacement of 50 mm. The case study was conducted at Borneo Indo Bara, one of Indonesia's largest open-pit coal mines located in South Borneo Province. We analyzed four sidewall slopes that were subjected to repeated blasting events. The results indicated that the slope's LOM design could tolerate blasting vibrations corresponding to a peak particle acceleration (PPA) of up to 0.41 g, which yielded a dynamic FoS of 1.35. This value is significantly higher than the pseudo-static approach, which indicated a pseudo-static FoS of 1.04 for a PPA of 0.12 g. Furthermore, this study assists mining practitioners in predicting the allowable number of blast events to prevent slope failure and recommends avoiding blast events with a scaled distance of less than 8 m/kg to prevent sudden slope failures. In conclusion, the study highlights the importance of the integrated approach that combines signature hole analysis, Newmark's sliding block method, and the SRF approach for evaluating the dynamic FoS of mine slopes subjected to bench blasting. The results of this study can offer valuable insights for mining engineers engaged in bench blasting to adopt the proposed integrated approach, which is still overlooked in Indonesia's open pit blasting practices.
台阶爆破在露天煤矿中普遍使用，因为它能有效提高煤炭产量并有助于剥离覆盖层。然而，无控制的爆破会产生显著的振动和加速度，如果永久位移量超过其临界值，可能会导致边坡失稳。计算爆破引起的边坡动态安全系数（FoS）的一种常用方法是拟静力法；然而，这种方法往往过于保守。在本研究中，我们利用纽马克滑块法和强度折减系数（SRF），通过评估台阶爆破引起的永久位移来评估边坡的动态FoS。我们的地震输入基于通过对特定台阶爆破设计的特征孔分析获得的完整振动波形。动态FoS定义为导致临界边坡位移为50毫米的SRF阈值。案例研究在位于南婆罗洲省的印度尼西亚最大的露天煤矿之一婆罗洲印多巴拉进行。我们分析了四个遭受重复爆破事件的侧壁边坡。结果表明，边坡的生命周期设计能够承受高达0.41g的峰值颗粒加速度（PPA）对应的爆破振动，其动态FoS为1.35。该值明显高于拟静力法，对于0.12g的PPA，拟静力法得出的拟静力FoS为1.04。此外，本研究有助于采矿从业者预测允许的爆破事件数量以防止边坡失稳，并建议避免采用小于8m/kg的比例距离的爆破事件以防止边坡突然失稳。总之，该研究强调了结合特征孔分析、纽马克滑块法和SRF方法的综合方法对于评估受台阶爆破影响的矿山边坡动态FoS的重要性。本研究结果可为从事台阶爆破的采矿工程师采用所提出的综合方法提供有价值的见解，而该方法在印度尼西亚的露天爆破实践中仍被忽视。
