The uniaxial compressive strength (UCS) is one of the most common mechanical parameters required in geotechnical engineering to characterize the compressive strength of rock material. Measurements of UCS are expensive, time consuming, destructive and thus, not favorable in the presence of limited samples. Therefore, a simple yet practical application is needed for the estimation of UCS. This research presents two correlations to predict UCS values for granite and schist by using ultrasonic velocity travel time (tp) from ultrasonic tests. The validity of the practical approach presented in this research is confirmed based on the strong correlations developed from the experimental tests conducted. For the entire data set, the correlation between UCS and ultrasonic velocity travel time was expressed as UCS = 217.2 e-0.016(tp) for granite and UCS = 1110.6 e-0.037(tp) for schist and the coefficient of determination (R2) value for both granite and schist is 0.93. These correlations may be useful for applications related to geotechnical engineering designs.
The peak friction angle (φpeak) roughness of discontinuity surfaces is a value that is fundamental to the understanding of shear strength of geological discontinuities, considering its importance in determining the mechanical properties of the discontinuity surface. It is however, both time and cost demanding to determine the peak friction angle as it requires an extensive series of laboratory tests. This paper presents an approach in the form of an experimentally determined polynomial equation to estimate peak friction angle of limestone discontinuity surfaces by measuring the Joint Roughness Coefficient (JRC) values in a field survey study, and applying the fore mentioned empirical correlation. A total of 1967 tilt tests and JRC measurements were conducted in the laboratory to determine the peak friction angles of rough limestone discontinuity surfaces. The experimental results were analyzed and correlated to establish a polynomial equation of φpeak = -0.0635JRC2 + 3.95JRC + 25.2 with coefficient of determination (R2) of 0.99. The laboratory results were also compared with theoretical results calculated from Barton's linear equation. The results shown that estimation of peak friction angles were more accurate using the newly proposed polynomial equation since the percentage differences between measured and calculated peak friction angles is less than 6% compared to estimation from Barton's linear equation where the percentage of differences is less than 11%. The proposed correlation offers a practical method for estimation of peak friction angles of discontinuity surfaces of limestone from measurement of JRC in the field.
The ultimate bearing capacity is an essential requirement in design quantification for shallow foundations especially
for structures built on large rock masses. In many engineering projects, structures built on foundation of heavily jointed
rock masses may face issues such as instability and sudden catastrophic rock slope failure. Determination of the ultimate
bearing capacity (Qult) of foundations resting on rock mass has traditionally been determined by employing several
strength criterions. One of the accepted and widely implemented methods is to use the Hoek-Brown failure criterion 2002,
where the required parameters are determined from a rock mass classification system, Geological Strength Index (GSI).
This paper defines an assessment for ultimate bearing capacity (Qult) based on the Hoek-Brown failure criterion 2002
for a granitic rock slope beneath a 20 m diameter concrete water tank at Bandar Mahkota Cheras, Kajang, Selangor.
Based on the Hoek-Brown failure criterion 2002, the ultimate bearing capacity (Qult) of rock mass was 7.91 MPa. The
actual stress acting on the rock mass was 0.32 MPa. The assessment showed that the rock mass is safe since the ultimate
bearing capacity (Qult) is 24.7 times higher than the actual stress acting on the rock mass.
The uniaxial compressive strength test is a destructive and time consuming test. A number of non-destructive methods using portable testing equipment are more applicable and easier to conduct. This paper presents the results of a systematic approach to determine the uniaxial compressive strength of rock material using the Schmidt hammer rebound test. A total of five distinct locations (Graham Coast, Davis Coast, Nanson Island, Danco Coast and Trinity Island) were tested using the Schmidt rebound hammer test. Peninsula Antarctic located at northwest of Antarctic region comprising of igneous and metamorphic rocks. Statistical analysis of the results at 95% confidence level showed the Schmidt rebound value of the Graham Coast ranges from 40±1.7 to 41±1.3 with standard deviation of 8.2 to 6.4. The rebound value for Davis Coast was 39±1.6 with standard deviation of 7.7. Rocks from Nanson Island and Danco Coast have the Schmidt rebound value of 54±1.7 with standard deviation of 8.0 and 36±1.3 with standard deviation of 6.2, respectively. The Schmidt rebound value of rocks at Trinity Island ranges from 29±1.4 to 32±1.7 with standard deviation of 6.8 to 8.1. Thus, the respective uniaxial compressive strengths of rock materials from Graham Coast, Davis Coast, Danco Coast, Nanson Island and Trinity Island were 73-108, 50, 59, 164 and 45-59 MPa. The respective ISRM strength classification of rock materials of Graham Coast, Davis Coast, Danco Coast, Nanson Island and Trinity Island were strong (R4) to very strong rock (R5), medium strong rock (R3), strong rock (R4), very strong rock (R5) and medium strong (R3) to strong rock (R4). The results showed a mean of quantification of rock material strength based on the Schmidt Hammer rebound test in Antarctic Peninsula.
The stability of the limestone cliff at Gunung Kandu, Gopeng, Perak, Malaysia was assessed based on the Slope Mass
Rating (SMR) system on 53 cross sections of the Gunung Kandu hill slopes. The slopes of Gunung Kandu were identified
as class I (very good) to IV (poor). The kinematic analysis showed that 12 out of 53 hill slopes of Gunung Kandu were
identified as having potential wedge, planar and toppling failures. The assessment showed that the stability of the western
flanks can be classified as stable to unstable with the probability of failure from 0.2 to 0.6. The stability of the eastern and
southern flanks range from very stable to partially stable with the probability of failure from 0.0 to 0.4. While the stability
of northern flanks are from very stable to stable with the probability of failure of 0.0 - 0.2. This systematic approach
offers a practical method especially for large area of rock slope stability assessment and the results from probability of
failure values will help engineers to design adequate mitigation measures.
The limestone hill of Batu Caves is slowly being turned into a recreation park for slope climbing, base jumping and cave exploring. Quantitative assessment on the stability of the cave is essential to ensure the safety of tourists and visitors. The aim of this study was to quantitatively assess the stability of Gua Damai, Batu Caves, Selangor, Malaysia by using the Q system for rock mass classification, together with other factors such as cave width and thickness of the cave roof. The stability of the limestone cave wall was evaluated using Slope Mass Rating (SMR). A discontinuity survey conducted along the slopes beneath the opening of the cave showed that the rock mass comprised of four major joint sets labeled as J1, J2, J3, and J4 with the dip directions and angles of 110˚/73˚, 325˚/87˚, 243˚/39˚ and 054˚/30˚, respectively. The result of kinematic analysis showed that the dip direction/dip angle of a potential wedge failure was 051˚/59˚. By referring to the ratio of cave roof thickness with cave width, the results showed that the cave is stable. Based on the relationship between Q system and the cave width, the stabilities of Section 4 of Gua Damai is stable while Section 1, 2, 3, 5, 6, 7 and 8 require supports. Based on SMR, the cave walls stability at Portion c, d, and f were not stable while Portion a, b, e and g were stable. Overall, the most stable part of the cave is Section 4 followed by Sections 5 and 2. Sections 1, 3 and 8 are moderately stable while Sections 6 and 7 have poor stability.