An Efficient Reliability-Based Approach for Evaluating Safe Scaled Distance of Steel Columns under Dynamic Blast Loads

Damage to building load-bearing members (especially columns) under explosions and impact are critical issues for structures, given that they may cause a progressive collapse and remarkably increase the number of potential victims. One of the best ways to deal with this issue is to provide values of safe protective distance (SPD) for the structural members to verify, so that the amount of damage (probability of exceedance low damage) cannot exceed a specified target. Such an approach takes the form of the so-called safe scaled distance (SSD), which can be calculated for general structural members but requires dedicated and expensive studies. This paper presents an improved calculation method, based on structural reliability analysis, to evaluate the minimum SSD for steel columns under dynamic blast loads. An explicit finite element (FE) approach is used with the Monte Carlo simulation (MCS) method to obtain the SSD, as a result of damage probability. The uncertainties associated with blast and material properties are considered using statistical distributions. A parametric study is thus carried out to obtain curves of probability of low damage for a range of H-shaped steel columns with different size and boundaries. Finally, SSD values are detected and used as an extensive databank to propose a practical empirical formulation for evaluating the SSD of blast loaded steel columns with good level of accuracy and high calculation efficiency.

A Re-Look Into Modified Scaled Distance Regression for Prediction of Blast-Induced Ground Vibration

Underground blasts are conducted for deep excavations, tunneling, or mining activities. Scaled distance regression analysis is performed in industry to estimate peak particle velocity from charge weight and distance. For addressing the uncertainties in estimating safe charge weight for controlled blasting, 95% confidence expression is generally used. For addressing inaccuracies arising from superimposition of blast waves in multi-hole blasting when using attenuation equation developed from single-hole blast data, a modified approach was proposed in literature. This article presents comparisons to establish that industrial practice of scaled distance regression would be as satisfactory as the proposed modified approach, when various performance measures (including parsimony) are considered together. Furthermore, industrial practice of using 95% confidence expression generated from sufficient data (say, 40 numbers) would result in safe charge weight estimation, whereas modified scaled distance approach (mean expression) could still result in few non-conservative values.

ANALISIS GROUND VIBRATION AKIBAT LEDAKAN PADA TAMBANG NIKEL DI PT. VALE INDONESIA, TBK

Ground vibration adalah gelombang yang bergerak di dalam tanah yang bersumber dari suatu energi yang berasal dari alam dan adanya aktivitas peledakan yang dilakukan oleh manusia. Selama ini ground vibration dianggap sebagai waste energy yang dapat merusak dan menjadi isu terhadap lingkungan di sekitar area tambang. Tujuan dari penelitian adalah untuk mengetahui pengaruh jumah bahan peledak yang digunakan terhadap ground vibration yang dihasilkan dan perbandingan akurasi ground vibration aktual dan prediksi. Metode penelitian yang digunakan adalah metode kuantitatif dengan pengambilan data langsung dari lapangan berupa pengukuran burden, spacing, ke dalam lubang ledak kemudian dihitung berdasarkan persamaan R.L. Ash sehimgga memperoleh nilai powder factor (PF), banyaknya penggunaan bahan peledak dan berat isian bahan peledak. Pengambilan data jarak lokasi, perhitungan scaled distance (SD), kostanta (K) dan perhitungan peak particle velocity (PPV) menggunakan rumus USBM Oriard ' sehingga memperoleh nilai PPV prediksi. Hasil penelitian menunjukkan bahwa ground vibration sangat dipengaruhi oleh jumlah bahan peledak yang digunakan untuk PF 0,11 dengan jumlah muatan 933 kg nilai PPV yang dihasilkan 1,28 mm/s sedangkan untuk PF 0,28 dengan jumlah muatan 2182 kg nilai PPV yang dihasilkan 4,62 mm/s, Jadi semakin besar jumlah bahan peledak yang digunakan maka intensitas ground vibration yang dihasilkan akan semakin meningkat. Perbandingan akurasi ground vibration aktual dan prediksi diperoleh persentase rata – rata 1,32%.

Development and Validation of Overpressure Response Model in Steel Tunnels Subjected to External Explosion

This study employed C4 explosives to evaluate the overpressure response in steel tunnels subjected to external explosions. The explosive scaled distance of the C4 charge from 2.15 to 3.26 m/kg1/3 was evaluated by experiments and the hydrodynamic finite element code LS-DYNA. The numerical results are in agreement with the experimental results. A simple way to estimate the overpressure in steel tunnels was proposed in this paper. The proposed methodology is both useful and efficient and can be further developed for designing protection for military structures and other facilities against explosion.

Prediction of Damage Level of Slab-Column Joints under Blast Load

The behavior of a slab-column joint subjected to blast loads was studied by numerical analysis using a general-purpose finite element analysis program, LS-DYNA. Under the explosive load, the joint region known as the stress disturbed zone was defined as a region with a scaled distance of 0.1 m/kg1/3 or less through comparison with ConWep’s empirical formula. Displacement and support rotation according to Trinitrotoluene (TNT) weight and scaled distance were investigated by dividing in and out of the joint region. In addition, fracture volume was newly proposed as an evaluation factor for blast-resistant performance, and it was confirmed that the degree of damage to a member due to blast loads was well represented by the fracture volume. Finally, a prediction equation for the blast-resistant performance of the slab-column joint was proposed, and the reliability and accuracy of the equation were verified through additional numerical analysis.

Study on Pressure Characteristics and Its Evolution Law at the Ellipsoidal End Cover Pole of Cylindrical Explosion Containment Vessels

To explore the postposition of the maximum pressure at the pole of the ellipsoidal end cover of cylindrical explosion containment vessels and to reveal the mechanism of the load evolution, the experimental method was used to measure the pressure curve at the pole under different charges, and the numerical simulation method was used to analyze the evolution law of the explosion flow field within the end cover. The results show that the end cover pole was subjected to three types of pressure: the primary explosion wave, the secondary shock wave and the convergence wave. In addition, the pressure peaks increased in sequence. The evolution of the flow field in the end cover was affected by the amount of charge and the aspect ratio of the vessel. When the scaled distance due to a small charge increased, or when the aspect ratio of the vessel was reduced, the time interval between the convergence wave and the secondary shock wave at the end cover pole decreased gradually. When the scaled distance increased to 4.05 m·kg−1/3, the convergence wave at the pole superimposed on the secondary shock wave. As the aspect ratio of the vessel ranged from 1.75 to 2.50, the time interval between the two peaks was about 150 μs. However, if the aspect ratio was less than 1.40, the convergence wave and the secondary shock wave were fused through complex interaction.

ANALISIS GETARAN PELEDAKAN TERHADAP PABRIK PENGOLAHAN EMAS PT. AGINCOURT RESOURCES, TAPANULI SELATAN, SUMATERA UTARA

ABSTRAK Getaran tanah merupakan salah satu efek peledakan yang harus diperhatikan terutama pada saat aktivitas penambangan berada di dekat bangunan penting dan masyarakat. Penambangan emas PT. Agincourt Resources di Tapanuli Selatan, Sumatera Utara, Indonesia melakukan operasi penambangan di 2 pit yaitu pit Purnama dan pit Barani. Posisi pit Purnama berdekatan dengan processing plant yang digunakan sebagai tempat peleburan dan pemurnian emas dengan jarak sekitar ±30 m, sedangkan Pit Barani yang berjarak sekitar 1200 meter dari perumahan penduduk. Paper ini difokuskan pada penelitian untuk mengantisipasi pengaruh getaran peledakan di pit Purnama terhadap processing plant. Penelitian dilakukan dengan mengukur getaran hasil peledakan menggunakan dua alat ukur Blasmate dan Micromate yang diletakkan di depan freeface dan di belakang freeface. Pengukuran ini bertujuan memprediksi bahan peledak per delay agar getaran hasil peledakan tidak berpengaruh terhadap bangunan. Analisis dilakukan dengan menggunakan persamaan scale distance dan software Shotplus sehingga dapat ditentukan prediksi jumlah bahan peledak per delay di setiap jarak. Dengan mengacu standar perusahaan, dan SNI 7570:2010maka akan dilakukan standarisasi jumlah bahan peledak per delay yang diijinkan Kata Kunci: getaran peledakan, pabrik pengolahan, scaled distance, shotplus, Standar Nasional Indonesia ABSTRACT Ground vibration is blasting effect that must be considered especially when mining activities are located near important buildings and communities. The activities of gold mining of PT. Agincourt Resources in Tapanuli Selatan, North Sumatra, Indonesia conducts mining operations in two pits, namely Purnama Pit and Barani Pit. Purnama Pit which is adjacent to a processing plant which is used as a gold smelting and refining with a distance of about ± 30 m, and Barani Pit which is about 1200 meters from village. This paper focused to anticipate damage to the processing plant. The ground vibration measurements were carried out using 2 measuring instruments that placed in front of the freeface and behind the freeface. This measurement aims to predict charged per delay on each distance so that the ground vibration have no effect on the processing plant. The analysis was carried out by using the scaled distance and Shotplus software. Based on the analysis and referred to Indonesian National Standard for ground vibration, then charge per delay was determined Keyword : ground vibration, processing plant, scaled distance, shotplus, Indonesian National Standard

MANAJEMEN GETARAN UNTUK KESETABILAN LERENG DENGAN METODE “SIGNATURE HOLE ANALISYS” DALAM KEGIATAN PELEDAKAN TAMBANG TERBUKA

ABSTRAK Pit 10 merupakan wilayah operasional PT. Alamjaya Bara Pratama dalam kegiatan peledakan bekerjasama dengan PT. Multi Nitrotama Kimia sebagai penyedia bahan peledak dan jasa peledakan. Salah satu dampak yang ditimbulkan dari kegiatan peledakan adalah Ground Vibration yang akan mempengaruhi kestabilan lereng pada area pit 10. Desain akhir lereng pada pit 10 menunjukan batas maksimal Peak Particle Acceleration (amax) yang dapat diterima lereng akibat hasil peledakan sebesar 0,07g, sehingga perlu adanya manajemen getaran agar getaran yang dihasilkan oleh kegiatan peledakan tidak mempengaruhi kestabilan lereng di area Pit 10. Penelitian dan percobaan dilakukan menggunakan metode Signature Hole Analysis (SHA) untuk pemetaan terhadap perambatan gelombang di setiap range blok – strip tertentu untuk kemudian digunakan untuk memodelkan dan memprediksi getaran yang diakibatkan oleh kegiatan peledakan pada setiap blok – strip. Metode Signature Hole Analysis yang dikombinasikan dengan pendekatan Scaled Distance, berhasil menjadi solusi dalam tata kelola getaran peledakan di Pit 10. Hasilnya, sepanjang tahun 2019 berjalan, tidak ada isu berkenaan dengan bagian geoteknik dari lereng-lereng di seputaran area operasional Pit 10. Pendekatan Signature Hole Analysis dan kontrol bersama tim Geoteknik menghasilkan kerjasama yang baik serta tata kelola kestabilan lereng menjadi lebih aman. Kaca Kunci : Kestabilan Lereng, Peledakan, Signature Hole Analysis ABSTRACT Pit 10 is operational area of PT. Alamjaya Bara Pratama the blasting activity carried out with PT. Multi Nitrotama Kimia as provider of explosive and blasting service. One of the impact blasting activity is Ground Vibration which will affect the stability of the slope in the area pit 10. The final slope design in pit 10 shows the maximum limit of peak particle acceleration (amax) that can’t be exceed by 0,07g. its very necessary to manage the ground vibration so the vibration produced by blasting activity do not affect the stability of the slope in pit 10. Research and experiment conducted using Signature Hole Analysis (SHA) for monitoring wave propagation in each block-strip used to model and predict vibration which caused by the blasting activity. Signature Hole Analysis combined with Scaled Distance has succeeded in becoming the solution of ground vibration management in pit 10. Throughout 2019 there was no problem with geotechnical issues of slopes around the pit 10. Signature Hole Analysis Method and Geotechnical approachment result good impact of a slope stability on pit