Ferian Anggara’s research while affiliated with Universitas Gadjah Mada and other places

The stability of tunnel portal slopes is crucial to ensure the safety and continuity of tunnel construction projects. This study evaluates the slope stability at the tunnel inlet portal on Jl. Sultan Alimuddin - Jl. Kakap in Samarinda, East Kalimantan, using the Limit Equilibrium Method (LEM). The geotechnical investigation included interpreting borehole data, sampling soil and rock, and conducting laboratory tests to determine parameters such as cohesion, internal friction angle, and unconfined compressive strength. Slope stability analysis was performed using the Bishop Simplified and Morgenstern-Price methods under static and dynamic conditions with Slide 6 software. The results show that the slopes at this location are generally safe, with safety factors of 1.278 and 1.166 for the Bishop method, and 1.336 and 1.225 for the Morgenstern-Price method under static and dynamic conditions, respectively. Although the obtained safety factors indicate stable slopes, additional reinforcement such as soil nailing, rock bolts, or shotcrete is recommended to meet the higher safety standards suggested by SNI 8460:2017. This study demonstrates that the tunnel portal slopes have a good safety factor but require regular monitoring and maintenance to ensure long-term stability, especially considering the complex geological conditions and climate variability in the area.

With Samarinda serving as a key buffer to the capital city of Nusantara, which grapples with urbanization and congestion challenges, infrastructure development has become a critical focus, particularly the construction of the Sultan Alimuddin - Kakap Tunnel. Planned for Selili Village, this tunnel will be the first road tunnel in East Kalimantan and is strategically important for alleviating traffic congestion, enhancing the distribution of goods and services, and ensuring safety. However, the geological conditions at the construction site pose significant challenges, mainly due to weak rock with a high potential for landslides. By assessing the rock mass utilizing the Japan Society of Civil Engineers (JSCE) evaluation methodologies and the Rock Mass Rating (RMR), this research seeks to identify the most appropriate excavation techniques and tunnel support systems. To characterize the engineering geology, surface geological mapping, core drill analysis, tunnel excavation face mapping, and laboratory testing were performed. The RMR and JSCE assessment methods were compared to assess the rock mass quality and recommend appropriate excavation techniques and support systems. The findings reveal that the tunnel alignment is dominated by interbedded siltstone and sandstone lithologies. The rock mass quality along the tunnel, as reported by RMR, varies from fair to poor. Based on the JSCE method, the tunnel route falls into the DI, CII, and CI rock categories. The top heading and bench excavation method is recommended based on RMR, while the double bench method is suggested by the JSCE assessment. Although there are slight differences in the recommended support systems, both RMR and JSCE consistently advise using rock bolts and shotcrete as the main method of support for the tunnel.

Slope stability is a serious problem that academics are still looking into in terms of human safety, equipment, and structures along the slope. Failure on slopes happens for a variety of reasons, including rock physical and mechanical properties, discontinuity factors, slope geometry, and external variables like as rainfall and seismic activity. The research location was conducted on the Jragung dam diversion tunnel, administratively located in Candirejo village, Pringapus sub-district, Semarang, Central Java Province. The purpose of this study was to use an empirical and numerical method to investigate the impact of rock mass categorisation on slope stability. The RMR (Rock mass rating) method is used to characterize rock mass, and the SMR (Slope mass rating) method is used to measure slope stability. The numerical slope stability analyses were carried out with the help of Phase2 (Rocscience, Inc.). The results showed that the slope at the intake portal was class IV (poor), and that it was unstable utilizing the SMR technique. According to numerical research, the basic design cut slopes with a 51° inclination were found to be unstable even after strengthening. It was suggested that the slope geometry and support measures be adjusted even more. Modified cut slopes were found to be stable after the slope inclinations were changed from 51° to 27° and shotcrete and rock bolt reinforcement were added.

The occurrence of the Tanjung Formation as a coal-bearing formation that has thick coals and is laterally distributed along in Barito Basin causes it to be well-known as one of the biggest coal-producing basins in Indonesia. The genesis of Eocene coal formed in terrestrial depositional environment influenced by freshwater and marine transgression is the uniqueness of this coal and interesting to examine maceral’s characteristic and its microfacies, and the evolution of paleomire seam AGM-B3, AGM-B4, AGM-B5, and AGM-B6 in Kandangan area by organic petrography’s analysis and coal’s chemical analysis. The result of subbituminous coal’s petrography show vitrinite is the most abundant maceral ranging from 56,.6% - 80.36% vol, liptinite (15.27% - 39.45% vol), inertinite (0.55% - 15.18% vol), and mineral matter (0.18% - 4.36% vol) which is dominated by pyrite. Based on maceral’s assemblages, coal’s microfacies divided into four groups are (1) telovitrinite-rich group, (2) detrovitrinite-rich group, (3) telovitrinite-liptinite-rich group, (4) inertinite-rich group. The basal section of seam AGM-B6 is characterized by detrovitrinite-rich group while seam AGM-B3, AGM-B4, and AGM-B5 are characterized by telovitrinite-liptinite-rich group. The middle section only represented the inertinite-rich group in seam AGM-B3, and the top section of the coal seams, except AGM-B6, is typically represented by the telovitrinite-rich group. The vertical profile of paleomire evolution shows a repetition of topogenous mire changing into ombrogenous mire and then back to topogenous mire. The paleomire type developed includes wet forest swamp, forested peatlands, and intermittently dry forested swamp and the environmental conditions are telmatic. The correlation between paleomire’s type and coal maceral’s abundance in the Kandangan area reflects that the type of vegetation from woody plants that underwent high degradation, moderate gelification, and intensive oxidation processes triggered by a short dry season.

The Barito Basin is one of the basins in South Kalimantan and serves as a coal-producing region. One of the coal-bearing formations present in the Barito Basin is the Miocene Warukin Formation. The purpose of this research is to understand the characteristics of coal macerals, including the dominance of macerals and their microfacies, as well as the type and development of the mire where coal is deposited. This information is crucial for the coal geological study in the Kandangan region, South Kalimantan. The methods employed include organic petrography analysis, proximate and ultimate analysis on seams L8, L5, L5B, M16, and MS02 collected using the ply-by-ply method.The results of the subbituminous coal petrography examination in this formation show the dominance of vitrinite ranging between 41.34-74.04% vol, liptinite between 11.61-38.24% vol, inertinite between 2.21-32.32% vol, and mineral matter ranging from 0.17-1.98% vol, predominantly composed of pyrite. The ash content data ranges from 1.36-15.45 (% wt, adb). The sulfur content data ranges from 0.1-0.45 (% wt, daf). Based on the distribution of maceral abundance, coal microfacies can be categorized into five groups: (1) gelovitrinite-rich group, (2) telovitrinite-rich group, (3) liptinite-telovitrinite-rich group, (4) inertinite-rich group, and (5) telovitrinite-inertinite-rich group. The lower section is predominantly characterized by the telovitrinite-inertinite-rich group. In the middle section, the inertinite-rich group takes precedence, alternating with the liptinite-telovitrinite-rich group. The upper segment is primarily marked by the gelovitrinite-rich and telovitrinite-rich groups. The developed paleomire includes repetitions of topogenous mire and ombrogenous mire. The paleomire type is a wet forest swamp under limnic and telmatic conditions. The dominant original vegetation consists of woody plants, although shrubby plants are also found in significant amounts. Moderate to high gelification levels indicate that the peat was constantly inundated with water.

River flow diversion is one of the most critical factors that must be considered for the success of dam construction. Soil and rock can support and load; therefore, understanding their strength and properties before tunnel construction is essential. Tunnel excavation and support depend totally on rock mass quality. Surface geological mapping, drill core analysis, and laboratory testing characterized the engineering geology conditions. Rock Mass Rating (RMR) and Japan Society of Civil Engineers (JSCE) methods were compared to determine rock mass quality and recommend excavation and support systems. Results showed that slightly weathered andesite lava and tuff lapilli lithologies dominate the tunnel alignment. Based on RMR, the rock masses quality along the tunnel alignment consists of poor and fair, and based on JSCE, the tunnel alignment consists of D I and C II rock categories with L and M massive rock types. Top heading and bench are recommended for tunnel excavation based on RMR, and the double bench and full-face method with an auxiliary bench cut are recommended for tunnel excavation based on JSCE. Although the characteristics of other support systems vary marginally, support systems based on RMR and JSCE recommend rock bolts and shotcrete as the primary tunnel support systems.

Peat is a combustible material, and peat fire may be initiated by self-heating that triggers spontaneous combustion in some conditions. Therefore, peat type and volume are expected to correlate with the Critical Self-Ignition Temperature (CSIT) value. Eight samples used in this experiment represent hemic and sapric peats. This study uses a 5 cm wire-mesh basket to examine the CSIT value for each sample. Peat was heated at a constant ambient temperature (TE) using a designated oven. Different TE values were used to find the subcritical and supercritical conditions. Once these two conditions are obtained, the CSIT value is interpolated from the value between these two TE. The results of the experiments show all of the samples start to self-ignite at 170 °C, and we can conclude that there is no significant correlation between the type of peat and its CSIT value. To up-scale the calculation into the larger peat volume, a trend on the book versus CSIT diagram was used to interpolate the CSIT value for thicker peat layers and conclude that 8 m of peat thickness with 10% of inorganic content and <50% of moisture may be ignited at a temperature less than 50 °C. The result of this study could be used as preliminary data on the surface temperature that may induce spontaneous combustion.

In this decade, coal fly ash (CFA) is considered a potential secondary source of rare earth elements (REEs). However, most REEs in coal fly ash are encapsulated in aluminosilicate glass, making it challenging to recover them through acid leaching. In this study, a sequential alkaline–organic acid leaching was developed for the recovery of REEs from CFA. The effect of alkaline leaching using NaOH solution on the destructive ability of aluminosilicate glass, as well as the mineralogy and morphology changes of the resulting coal fly ash, was first studied. Furthermore, the effectiveness of alkaline leaching on the recovery ability of REEs through organic acid leaching was evaluated. The results show that the maximum leaching efficiency for Si and Al, which was obtained at the optimum alkaline leaching conditions, namely NaOH concentration of 10 mol/L, reaction temperature of 65 °C, liquid/solid (L/S) ratio of 10 mL/g, and reaction time of 90 min, is 28% and 32%, respectively. The digestion reaction with NaOH lixiviants also causes coal fly ash to become more porous, making it advantageous in the organic acid-leaching process at the REEs recovery stage. The utilization of the desilicated residue produced from the digestion process in acid leaching effectively increases the overall REEs recovery from 32.2% to 77.6%.