Erran, Muhammad Amroedhia Dzulfiqar (2023) Analisis Pola Distribusi Arah Stress dan Perubahan Stress di Area Kali Pillar-Grasberg Block Caving PT Freeport Indonesia menggunakan Metode Seismic Moment Tensor Inversion, Stress Inversion, dan Coulomb Stress Changes. Other thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Aktivitas penambangan bawah tanah merupakan aktivitas yang mengubah kondisi bawah permukaan sehingga menyebabkan adanya perubahan kondisi seperti tekanan pada batuan dan tanah yang dapat menyebabkan timbulnya potensi bahaya-bahaya seismik dan geoteknik seperti keruntuhan tambang bawah tanah. Oleh karena itu, diperlukan adanya analisis untuk mengetahui distribusi stress dan perubahan stress yang diakibatkan adanya aktivitas tektonik ataupun aktivitas penambangan sekitar area tambang bawah tanah. Analisis stress dari data perekaman mikroseismik digunakan melalui pendekatan inversi tensor momen seismik. Metode inversi tensor momen seismik digunakan untuk mendapatkan informasi mekanisme fokus serta informasi bidang patahan yang berkaitan dengan event seismik. Berdasarkan hasil inversi tersebut, parameter-parameter seperti strike, dip, dan rake dari suatu bidang patahan digunakan untuk inversi stress untuk selanjutnya didapatkan arah stress utama berupa σ_1, σ_2,〖 σ〗_3 dan rasio R serta pengolahan stress change untuk mengetahui distribusi pola perubahan stress dari setiap kejadian seismik. Sehingga berdasarkan analisis kedua metode tersebut dapat diketahui potensi bahaya seismik berdasarkan arah stress utama yang memicu kejadian seismik serta pola perubahan stress akibat terjadinya kejadian-kejadian seismik tersebut. Metode analisis tersebut diterapkan pada data perekaman gempa mikro yang direkam oleh microseismic monitoring system pada area Kali Pillar-Middle Access tambang bawah tanah Grasberg Block Cave-PT Freeport Indonesia yang diambil pada rentang 01 Juni 2021 hingga 31 Maret 2023. Hasil pengolahan dan analisis pada data terkait arah stress utama, analisis rezim stress, serta pola perubahan stress dari Coulomb stress changes menunjukkan adanya kesesuaian antara stress utama penyebab event seismik dan pola kenaikan stress dan area akumulasi stress terhadap lokasi kemunculan event-event seismik signifikan di area Kali-Pillar. Sedangkan pada area yang mengalami penurunan stress menunjukkan kurangnya kemunculan event seismik pada lokasi tersebut akibat menurunnya stress sehingga tidak terjadi failure pada tubuh batuan. Analisis tersebut menunjukan korelasi kuat antara perubahan arah stress utama dan pola kenaikan stress terhadap munculnya event-event seismik subsekuen pada periode bulan selanjutnya dan kaitannya dengan pengembangan caving. Hasil pengolahan dan analisis diharapkan dapat digunakan sebagai analisis tambahan dalam mengidentifikasi area akumulasi stress yang berpotensi menimbulkan bahaya seismik di area produksi terutama area Kali Pillar-Middle Access tambang bawah tanah Grasberg Block Cave-PT Freeport Indonesia.
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Underground mining activities are activities that change subsurface conditions, causing changes in conditions such as pressure on rocks and soil which can cause potential seismic and geotechnical hazards such as underground mine collapse. Therefore, an analysis is needed to determine the stress distribution and stress changes caused by tectonic activities or mining activities around the underground mining area. Stress analysis of the micro seismic recording data is used through the seismic moment tensor inversion approach. The seismic moment tensor inversion method is used to obtain focal mechanisms information and fault plane information related to seismic events. Based on the results of the inversion, parameters such as strike, dip, and rake of a fault plane are used for stress inversion to further obtain the main stress directions in the form of σ_1, σ_2,〖 σ〗_3 and R ratio as well as stress change processing to determine the distribution of stress change patterns from any seismic event. So based on the analysis of the two methods, it can be identified the seismic hazard potential based on the direction of the main stress that triggers the seismic event and the pattern of stress changes due to the occurrence of these seismic events. This analysis method is applied to micro seismic recording data recorded by the micro seismic monitoring system in the Kali Pillar-Middle Access area of Grasberg Block Cave underground mine-PT Freeport Indonesia taken from 01 June 2021 to 31 March 2023. The results of processing and analysis of the data related to the main stress direction, stress regime analysis, and stress change patterns from Coulomb stress changes indicate that there is a match between the main stress causing seismic events and the pattern of stress increase and the area of stress accumulation to the location of occurrence of significant seismic events in the Kali-Pillar area. Whereas in areas that experience a decrease in stress, it shows a lack of occurrence of seismic events at that location due to reduced stress so that failure does not occur in the rock body. The analysis shows a strong correlation between changes in the direction of the main stress and the pattern of increasing stress on the emergence of subsequent seismic events in the following month period and its relation to caving development. The processing and analysis results are expected to be used as additional analysis in identifying areas of accumulated stress that have the potential to cause seismic hazards in the production area, especially the Kali Pillar-Middle Access area of the Grasberg Block Cave underground mine-PT Freeport Indonesia.
| Item Type: | Thesis (Other) |
|---|---|
| Uncontrolled Keywords: | Seismic Moment Tensor Inversion, Focal Mechanisms, Stress Inversion, Stress Change, Inversi Tensor Momen Seismik, Mekanisme Fokus, Inversi Stress |
| Subjects: | T Technology > T Technology (General) |
| Divisions: | Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Geophysics Engineering > 33201-(S1) Undergraduate Thesis |
| Depositing User: | Muhammad Amroedhia Dzulfiqar Erran |
| Date Deposited: | 10 Oct 2023 01:52 |
| Last Modified: | 10 Oct 2023 01:52 |
| URI: | http://repository.its.ac.id/id/eprint/103549 |
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