MATERIAL CHARACTERIZATION FOR GEOTECHNICAL MODELING AND ASSESSMENT
Akbar Aprian, S.T.
On Going Jr Geotech Engineer, Graduate Mining Engineering at Institut Teknologi Sumatera, Jl. Terusan Ryacudu, Way Huwi, Kec. Jati Agung, Kabupaten Lampung Selatan, lampung, 35365
akbaraprian04@gmail.com
Discussing about geotechnics closely related to material characterization in either rock or soil based on litology, alteration, and regional geology. There are several engineering properties both mechanical and physical, that are necessary to define characterization and geotechnics models : density, strength of rock intact (sig. ci), generalized hoek-brown parameters (Mb, s, a), modulus young (Em), mi of rocks, poisson ration (v), shear strength (Sig. t), and Disturbance factor (D). Some of the material characterization parameters were obtained by lab-test scale.
Picture 1. Define rock. Sources : Wyllie et al. (2004)
GSI value ilustrated in the equation above is the value of rock mass clasification (Marinos, 2005) whicsh has been discussed in others blogs. Mi value and disturbance faktor refers to type of rock and blasting in tunnel for underground mining or slope for surface mining ilsutrated in Pict 2. The strength of intact rock is not affected by joint/Intact rock (Sig.Ci) can be obtained from several test : UCS (Uniaxial Compressive Strength), PLI (Point Load Index), Schmidt Hammer, etc. Ilustrated PLI and UCS can be reach in Pict 3 and Pict 4. FYI 1 kilonewton/meter² (kN/m²) = 0,001 megapascal (MPa).
Picture 2. Sources : Hoek et al. (2002)
PLI testing is refers to ISRM (International Society for Rock Mechanics), SNI 03-3695-1995, BS 812: Part 111, ASTM D5731.
Picture 3. PLI Testing
UCS testing is refers to ASTM D7012, ISRM Suggested Methods (1981 and 2007), SNI 2810:2012.
Picture 4. UCS Testing
The different treatment/engineering between of soft materials (soil) and hard materials (rock). If hard materials closely to GHB failure criterion and UCS/PLI testing, soft materials is closely to MC failure criterion and triaxial testing (Sig.1 and Sig.3) to obtain cohesion (c) and friction angle (phi). Triaxial testing ilustrated in Pict 5.
Picture 5. Triaxial testing
Picture 8. The correlation of maximum stress & minimum stress of GHB dan MC criterion
Terdapat juga parameter fisik material yaitu permeabilitas (kemampuan meloloskan air) & porositas (tingkat kepadatan material atau pori), density, kadar air. Based on eksperience, porosity and permeability have a similar/liniear progressive ilustrated in Pict 8. Sebagai contoh pasir memiliki porositas tinggi dan permeabilitas tinggi, sedangkan granit memiliki porositas rendah dengan permeabilitas rendah juga. contoh lainnya lempung memiliki porositas tinggi namun dengan permeabilitas rendah.
Picture . Linier of Porosity and Permeability
REFERENCES
Aprian, A. (2025). Analisis Perkuatan Tunnel menggunakan Metode RMR, Q-System, dan Finite Element Method pada TD XC-2 CG 460. Jurnal Riset Teknik Pertambangan, 91-106.
Broch, E., & Franklin, J. A. (1972). The Point-Load Strength Test. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, 669-697.
E. Hoek, C. C. (2002).
Hoek-Brown Failure Criterion. Hoek-Brown Failure Criterion – 2002 Edition,
1-2.
E. Hoek, M. P. (2005).
Characterization and engineering properties of tectonically undisturbed but
lithologically varied sedimentary rock masses. International Journal of Rock
Mechanics and Mining Sciences.
Hoek, E. (2000). Big Tunnels in Bad Rock. ASCE Journal of Geotechnical and Geoenvironmental Engineering Vol. 127, 2-15.
Wyllie, D. C., Mah, C. W., & Hoek, E. (2004). Rock slope engineering: civil and mining (Vol. 4th). New York; London: Spon Press
ISRM. (1985). Commision on Testing Methods. International Journal Rock Mech. Min, Sci. & Geomech. Abstr. Vol. 22, No. 2, 51-60.
Rai, M. A., Kramadibrata, S., & Wattimena, R. K. (2014). Mekanika Batuan. bandung: ITB.
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