Kajian pengaruh faktor batuan terhadap fragmentasi batuan overburden hasil peledakan berdasarkan model Kuz-Ram

Distribusi fragmentasi hasil peledakan dipengaruhi oleh beberapa faktor ialah massa batuan, jenis bahan peledak, jumlah bahan peledak yang digunakan, deskripsi massa batuan didalam faktor batuan pada daerah penelitian yaitu powdery dan blocky. Penelitian ini berfokus pada pengaruh factor batuan terhadap fragmentasi hasil peledakan overburden.Metode yang digunakan pada penelitian ini adalah pengamatan secara langsung dilapangan untuk mendapatkan gambaran mengenai kondisi situasi aktual seperti keterdapatan rock mass description (RMD), joint plane spacing (JPS), joint plane orientation (JPO), specific gravity (SGI), hardness. Pada penelitian faktor batuan hanya nilai RQD yang memiliki pengaruh sangat besar dalam peledakan. Analisis faktor batuan terhadap fragmentasi batuan menggunakan perangkat lunak Split Desktop 2.0 untuk menghitung hasil fragmentasi aktual hasil peledakan sedangkan untuk teoritis menggunakan metode model Kuz-Ram. Berdasarkan kajian nilai rock quality designation terhadap fragmentasi batuan hasil peledakan didapatkan nilai fragmentasi 80 cm ≥ 80% dikatakan ideal, hasil fragmentasi pada 2 lokasi penelitian dengan kegiatan peledakan 6 kali ialah 93,61%, 87,68%, 90,91% (powdery) dan 72,68%, 74.56%, 76.04% (blocky) untuk perhitungan model Kuz-Ram. Jadi pada satu lokasi penelitian masih di jumpai hasil distribusi fragmentasi yang kurang bagus dengan ukuran saringan 80 cm ≤ 80%, yaitu pada deskripsi massa batuan blocky. Kata Kunci: factor batuan, fragmentasi batuan, hasil peledakan, massa batuan

Characteristics Analysis of Generalized Rock Quality Designation (RQD) Based on Degree of Joint Development

Rock quality designation (RQD) is widely adopted as a fundamental tool in characterizing rock masses since it was devised in 1964. Since the conventional RQD calculation is limited due to its dependence on the selected threshold, previous research introduced generalized RQD to adequately reflect the anisotropy and scale effect of RQD. However, the influence of the joint development inside rock mass on generalized RQD remains unclear. The objective of this work is to investigate characteristics of the generalized RQD in view of different development degrees of discontinuities in rock mass, including spacing (density) and trace length. Three-dimensional fracture network modelling is employed to simulate the actual rock mass of open-pit iron mine in China. Virtual scanlines are set to obtain RQD values in different directions. The results primarily show that the generalized RQD should be introduced to calculate the RQD with different thresholds to fully reflect the anisotropy of rock mass. The optimal threshold can be obtained based on an anisotropic coefficient, which is defined by (RQDmax-RQDmin). It is also indicated that the fracture spacing has a great influence on both the anisotropy of RQD and the selection of the optimal threshold. The optimal threshold of the generalized RQD increases with the increase in the fracture spacing. In addition, the scale effect of RQD in different models is discussed by changing the length of the scanlines. The longer the scanlines we set, the more stable RQD value can be obtained in the model. It is recommended to fit much longer scanline to get realistic RQD in heavily fractured rock mass.

Study of Ground Investigation Data along the Brunei Temburong Bridge Alignment

The Brunei Temburong Bridge (BTB) is an iconic project connecting Brunei Muara and Temburong districts in Brunei over a length of 30 km. The bridge crosses from Brunei Muara across Brunei Bay to Temburong. A key aim of the BTB project was the development of Temburong district, being prior the more isolated district, because of not having a direct land link to the other districts. This study reviews the geology of soil materials and sedimentary rocks along the bridge alignment based on 164 boreholes drilled for ground investigation. Standard Penetration Test, Rock Quality Designation and Fracture Index data were evaluated to interpret soil materials and sedimentary rocks along the alignment. Borehole data was used to generate lithological cross sections along the alignment providing an overview of geology. The geology encountered is extremely heterogenous, with low strength sediments encountered at depth of up to 80 m and more e.g., at the Temburong section. Rock quality designation vs. Fracture Index did not show a strong correlation likely due to the extreme heterogeneity in particular for the Brunei Bay and Temburong sections. The study demonstrates the importance of a closely spaced investigative drilling and sampling program for major construction programs which was successfully achieved for this project. Other investigative techniques such as geophysical methods could be highly useful for future projects. Considering economic and environmental reasons these techniques could be very useful to map the top of the bedrock even under highly heterogeneous ground conditions.