GEOMATE Journal

MODEL EXPERIMENTS ON FAILURE MECHANISM OF VOLCANIC SLOPES DURING SEISMIC LOADING AND RAINFALL

Ryuta Komatsu — 2025-12-29

This study aims to clarify the mechanical behavior until failure of slopes formed from pyroclastic fall deposits (Tarumae volcanic soil: Ta-d) in Atsuma Town, Hokkaido, Japan, under seismic loading and rainfall conditions. Experiments utilized highly fragile Ta-d PR layer samples for the model slopes. The experiment used a model soil container with a one-dimensional cyclic loading apparatus for seismic loading tests and a spray nozzle system to make it rain artificially. Instrumentation consisted of pore water pressure gauges, dielectric soil moisture sensors, and accelerometers. Particle breakage of soils was quantified by measuring the fine content increase rate (ΔFc) via sieve analysis of samples before and after testing. Shaking table tests revealed that strong seismic loading caused an increase in pore water pressure, resulting in slope failure, even at low saturation. Crushing of soil particles was confirmed under seismic loading, indicating that cyclic shearing in volcanic coarse-grained soils can induce particle breakage and lead to earthquake-induced slope instability. Rainfall tests showed that slopes failed due to infiltration, with pore water pressure and moisture changes varying by initial water content. Particle crushing of soils was also observed during rainfall, more so in wetter conditions. A unique relationship was found between initial and failure-time water content, consistent with other volcanic soils in Hokkaido. These findings offer fundamental data for predicting slope collapse and suggest practical stability assessment via field measurements.

INFLUENCE OF COARSE AGGREGATE CONTENT IN RECYCLED ASPHALT MIXTURES ON RUTTING AND RESILIENT MODULUS

Hermon Frederik Tambunan — 2025-12-29

The use of recycled asphalt (RAP) as a road maintenance material has been widely applied. The use of RAP is expected to reduce maintenance costs and have a positive impact on the environment. This study assesses the performance of recycled asphalt mixtures that undergo changes in gradation within the coarse aggregate (CA) fraction and the asphalt aging process, resulting from traffic loads and weather fluctuations. Four mixture variations were designed using different coarse aggregate (CA) contents of 39%, 35%, 27%, and 23%, representing progressive material degradation levels corresponding to field aging conditions. Each mixture was tested for rutting and resilient modulus under controlled temperature and loading cycle to evaluate performance degradation. Tests included Marshall tests, resilient modulus (MR), and wheel tracking tests. Results indicate that susceptibility increases with higher temperatures and lower CA, while the resilient modulus decreases linearly (r = 0.995, R² = 0.88). A 16-22% increase in rut depth and a 35-42% reduction in MR were observed when CA decreased from 39% to 23% at 50 °C. Rutting behavior and deformation rates, influenced by temperature and decreasing CA content, were found to be strongly correlated in each mixture variation. These conditions provide information on the tendency of recycled mixtures to undergo degradation and asphalt aging processes, serving as a guide for determining the optimal time to carry out the recycling process. Economic calculations optimize the use of new materials in road maintenance through recycling.

LANDSLIDE HAZARD INVESTIGATION AND SLOPE STABILITY ASSESSMENT OF INDRAPURI HOUSING PEKANBARU, INDONESIA

Merley Misriani — 2025-12-29

Housing development in Indrapuri, Pekanbaru, located in a hilly area with steep terrain, presents potential landslide hazards due to soil cutting and filling activities. This research is essential to determine whether the housing development at this location is stable from landslide hazards, necessitating a scientific slope stability analysis. The study aims to evaluate the safety factor of cut slopes, analyse landslide hazards based on soil characteristics, and assess the impact of slope height on landslide potential. The research methodology involves slope investigations, soil characteristic testing in field and laboratory settings, and slope stability evaluation using the Fellenius Method. Field investigation results indicate that slope heights vary from 2 m to 5 m, with a slope angle (α) of 68°. The soil shear strength parameter (ø) varies between 21.25° and 64.85°, while cohesion (c) ranges from 43.97 kN/m² to 84.56 kN/m². These parameters can affect slope stability. At the Indrapuri site, variations in soil shear strength and cohesion are likely influenced by geological and environmental factors. Slope stability analysis reveals that the current slope conditions are stable from landslide hazards, with safety factor values ranging from 2.42 to 5.20. These values exceed the minimum threshold for slope stability (SF ≥ 1.25), indicating stable conditions. However, under extreme rainfall conditions or additional loading, the safety factor may decrease significantly and approach the critical limit (SF≤ 1.07), potentially leading to slope failure.

BALANCING DAMPING GAINS AND STRENGTH LOSSES IN RUBBER-MODIFIED CEMENT ASPHALT MORTAR

Aditya Wahyu Erlangga — 2025-12-29

Cement asphalt mortar (CAM) serves as a damping layer on non-ballasted tracks. The development of the damping characteristics of the CAM suggests using rubber powder as a substitute for fine aggregate to improve the damping properties. Rubber powder problems stem from potential significant decreases in mechanical properties. Meanwhile, the rubber content must be limited to achieve optimal mechanical and dumping properties. This study aims to systematically investigate the mechanical and damping characteristics of rubber powder-modified CAM to balance damping gains and strength losses. Mechanical properties are determined by compressive strength characteristics. Damping properties are determined by the damping ratio. Results showed that the rubber powder-modified CAM at 0%, 10%, 15%, and 20% exhibited that at 10% slightly decreased the compressive strength of CAM compared to 0%, while 15% and 20% significantly decreased it. The rubber powder-modified CAM at 10% exhibits better performance in terms of increasing the damping ratio, which has a relatively slight influence on the compressive strength loss of CAM. The rubber powder-modified CAM at 10% with a low asphalt content of 0.2 shows an increase in ductility, whereas at a high asphalt content of 0.6, it decreases compared to the rubber powder-modified CAM at 0%. The elastic modulus and dynamic modulus decrease with the rubber powder-modified CAM and significantly decrease with increasing asphalt content. The damping properties increased with the rubber powder-modified CAM and rose considerably with increasing asphalt content. The natural frequency decreases with the rubber powder-modified CAM and significantly decreases with increasing asphalt content.

CHARACTERISATION OF RAW AND TREATED DE-OILED BLEACHING EARTH FOR SUPPLEMENTARY CEMENTITIOUS MATERIAL

Basyid Hamid — 2025-12-29

This study assessed the potential of raw and treated De-Oiled Bleaching Earth (DOBE) as a supplementary cementitious material (SCM) by analysing its characteristics. DOBE, originating from Spent Bleaching Earth (SBE), is a waste of the palm oil refining industry, often discarded in landfills, hence presenting environmental hazards. Study on DOBE for its potential as an SCM is still limited, particularly on how its characterisation impacts its reactivity, which in this study was evaluated through the Strength Activity Index (SAI) test. Apart from examining its general properties, raw and treated DOBE were also analysed using X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and laser diffraction. The treatment at 700°C for one hour improved its pozzolanic reactivity by raising its amorphous silica content from 56.7% to 64.7% and removing residual oil and volatile contaminants. The Strength Activity Index (SAI) tests indicated that the treated DOBE achieved 98% (20.71 MPa) of the control mix strength at 7 days and 107% (29.05 MPa) at 28 days, exceeding that of ordinary Portland cement (OPC). The findings validate that treated DOBE complies with ASTM C618 criteria for Class N pozzolans, establishing it as a suitable SCM. Nevertheless, issues such as loss on ignition, moisture content, and oil content must be resolved to enhance its performance. This study emphasises DOBE's capacity to improve cement sustainability by reducing its dependency on cement and mitigating environmental concerns. Future studies need to include the assessment on its durability, shrinkage, and ideal replacement ratios in concrete mixes.

TSUNAMI HAZARD ASSESSMENT DUE TO POTENTIAL EARTHQUAKE ALONG THE FLORES BACK ARC THRUST IN BULELENG REGENCY

Lestari Naomi Lydia Pandiangan — 2025-12-29

Buleleng Regency in North Bali was considered to be widely prone to tsunamis, as it is in close vicinity to the active tectonic zone of the Flores Back-Arc Thrust that can lead to massive earthquakes. Flood area, maximum run-up height, and wave arrival time are the three critical seismic parameters analyzed in this research to assess tsunami risk in the studied region. This study used the COMCOT v1.7 software to perform numerical simulations for a hypothetical Mw 7.5 earthquake, incorporating both all-land and all-water data. The result shows that Gerokgak sub-district, which had the most inundated area, about 8.87 km², and the other sub-districts, such as Buleleng, Banjar, and Sawan, also faced inundation. At moderate water depths (0.5–3 m), the most extensive inundated areas overlap frequently with high-density populated coastal areas, particularly at the river outlets and lowlands. From the arrival time analysis, it is found that the eastern coast has the shortest warning time, e.g., the tsunami arrives at Ponjok Batu Beach 1 min 46 s after the triggering event, while the highest tsunami run-up value occurs at Bukti Beach (Kubu Tambahan), which is 9.86 m. Conversely, areas in the west, such as Gilimanuk, experience a tsunami arrival time exceeding 20 minutes. According to the results, the improvement of tsunami preparedness that includes early warning, evacuation planning, and coastal land use planning is necessary. The results of this study provide critical information for risk reduction strategies in Buleleng and similar coastal places.

HEAT ACCUMULATION REDUCTION IN CONDOMINIUM BUILDINGS USING MULTI-TYPOLOGY ROOFTOP LANDSCAPES

Anon Anan-archa — 2025-12-29

This report presents the findings of the heat reduction performance of rooftop garden designs tailored to suit the activities of residents in four condominium buildings (Buildings A to D). The study applied four rooftop garden design types (Types 01 to 04), comprising open walkways, lawn areas, vegetative coverage, and swimming pools, respectively. Each design was installed on a concrete rooftop surface with a thickness of 0.15 meters. The rooftop area covered by Type 01 design elements was set at 80%, 60%, 40%, and 20% for Buildings A, B, C, and D, respectively. Temperature data collected from rooms and corridors beneath the rooftop gardens revealed that Building D had the lowest average indoor temperature, which was up to 2°C lower than that of Building A and up to 0.74°C below the average ambient temperature. In addition, heat flux measurements indicated a maximum reduction of 46% compared to baseline conditions prior to installation. This study underscores the influence of rooftop garden design principles, which collectively shape rooftop thermal behavior, and highlights the importance of ecological design strategies in enhancing indoor comfort and mitigating urban heat accumulation.

COMPRESSIVE STRENGTH OF CONFINED REINFORCED RECYCLED COARSE AGGREGATE CONCRETE COLUMNS

Thanh-Tung Pham — 2025-12-29

This study examines the compressive behavior of confined concrete incorporating recycled coarse aggregate (RCA) and reinforced with spiral stirrups, aiming to assess its structural viability. Thirty-six cylindrical specimens (150 mm diameter × 300 mm height) were prepared with two RCA replacement levels (0% and 30%) and different spiral stirrup spacings (20, 25, 30, 50, and 100 mm). All specimens were tested under monotonic axial compression at 28 days, and experimental results were compared with theoretical predictions based on Mander’s confinement model. The incorporation of 30% RCA led to a moderate reduction in compressive strength, ranging from 2.85% to 9.72% compared to natural aggregate specimens. However, reducing stirrup spacing increased confinement and significantly improved strength and ductility, effectively compensating for the strength loss associated with RCA. Especially, specimens with 30% RCA and a 20 mm stirrup spacing achieved compressive strengths comparable to those of conventional concrete. Mander’s model consistently underestimated the compressive strength of confined RCA concrete, indicating that it provides conservative predictions when RCA is used. These results support the structural application of RCA in reinforced concrete, particularly when adequate confinement is provided.

A CALIBRATION OF AN AIR PLUVIATION SYSTEM USED TO RECONSTITUTE LARGE SPECIMENS OF SAND

Ihsan Al-abboodi — 2025-12-29

In physical modeling of geotechnical problems, the difficulty in preparing uniform deposits of granular soil or simulating the in-situ soil conditions increases as the size of the testing box increases. Special care should be provided to the soil preparation process in order to maintain trusted results in a repeated manner. In addition to striving to obtain reliable results, the method used, including the time spent and human effort expended, must be taken into consideration. In this study, a carefully designed and fabricated air pluviation apparatus is used to rain the sand uniformly and homogeneously over the area of the box. Many distinctive features were adopted in the design of the apparatus, such as emptying the box and restoring the sand automatically and getting rid of the dust outside the testing room, which both contribute positively to the health and productivity of the workers and to the quality of the job. In order to prepare a calibration database for a specific type of sand, a series of calibration tests was carried out to measure the density of sand with respect to the height of drop (HD) and the opening size of the perforated plate. It is found that the value of critical HD that achieves the maximum density depends on the porosity of the perforated plate, with a direct relationship between them. The porosity is also the critical factor that determines the density of sand at a certain value of HD. The obtained density can be increased by reducing the opening sieve size for a specific drop height.

STAGE ANALYSIS OF FOUNDATION SETTLEMENT IN RETAINED EXCAVATIONS USING PLAXIS 2D

Assilkhan Z. Abu — 2025-12-29

The relevance of the topic is due to the need to design and construct foundations in conditions of dense urban development and weak soils. The aim of this work is to study the features of pile foundation design, taking into account the stability of the excavation and the effect of phased loading on foundation settlement. The novelty of the research lies in the numerical modeling of phased construction using a wall in the ground, as well as the analysis of changes in the stress-strain state of the foundation, taking into account the stages of pile installation. Calculations performed in the Plaxis 2D software environment showed that when a five-story building is fully loaded, the foundation settlement does not exceed 1 cm, which is within the maximum permissible values according to the standards. The maximum horizontal displacement of the enclosing wall was 0.45 cm, which also indicates its stability at an excavation depth of up to 3 m and the presence of anchors. The results confirm the effectiveness of the combined system—walls in the ground, anchors, and pile foundations—when building on weak soils in confined conditions. The work is of practical value for the engineering and geotechnical justification of construction solutions in densely built-up areas.

INTEGRATING SONO-PHOTO-FENTON-LIKE AND NANO ZERO-VALENT IRON (NZVI) IN TNT YELLOW WATER TREATMENT

Son Tung Pham — 2025-12-29

Yellow water (YW) generated from the 2,4,6-Trinitrotoluene (TNT) production contains high concentrations of nitroaromatic compounds that pose serious risks to human health, ecosystems, and the environment. In this study, the removal of nitrotoluene compounds in yellow water treatment using the Sono-Photo-Fenton-like process combined with zero-valent iron nanoparticles (nZVI) was evaluated. The parameters of hydrogen peroxide dosage, nZVI dosage, ultraviolet power, and ultrasonic power on TNT degradation in yellow water treatment were investigated using the response surface methodology (RSM) to determine the optimal conditions. The findings demonstrated that at a pH of 3.0, with an initial TNT concentration of 80.8 mg L^-1, an nZVI dosage of 2 mM, a hydrogen peroxide concentration of 80 mM, an ultrasonic power of 60 W, and an ultraviolet power of 30 W, a TNT removal efficiency of 88.19% was attained after a reaction duration of 60 minutes.

EVALUATION OF RETAINING WALL COLLAPSE RISK UTILIZING VIBRATION CHARACTERISTICS

Yudai Harima — 2025-12-29

Since 1955, Japan has experienced a period of rapid economic growth, during which various social infrastructure facilities were constructed. Recently, however, the aging of these infrastructures has become a significant issue. Inspection and maintenance are essential for the upkeep of these infrastructure facilities. Currently, visual inspections are the mainstream method, making it challenging to quantitatively identify damage. In this study, vibration sensors were installed at the base and top sections of retaining walls, and vibrations from adjacent trains were utilized to evaluate the collapse risk of the retaining walls based on their vibration characteristics. The vibration characteristics were quantitatively assessed by calculating the primary natural frequency from the transfer function and observing temporal changes in the natural frequency to determine the degree of deterioration of the retaining walls. The analysis results showed no significant changes in the vibration characteristics of the retaining walls, indicating no collapse risk. By understanding the inherent vibration characteristics of the retaining walls, it is possible to perform quantitative evaluations, which may be applicable in determining the presence of damage and the necessity of countermeasures in the event of a disaster.

SOLVING OPTIMAL RESERVOIR OPERATION PROBLEMS FOR WATER INFRASTRUCTURE USING GENETIC ALGORITHM AND KEPLER OPTIMIZATION ALGORITHM

Rittayut Gonthong — 2025-12-29

Rule curves of reservoirs are necessary guides to operate reservoir in long term operation. This paper proposed an alternative approach of Genetic Algorithm (GA) and Kepler Optimization Algorithm (KOA) to connect with the simulation model for searching optimal reservoir rule curves as the flood control area. The proposed models were applied to determine the optimal flood rule curves of the Nam Oon Reservoir in the Northeast region of Thailand. Minimum average excess water and minimum frequency excess water were used as the objective functions for the searching procedure. The historic inflow, synthetic inflow data of 1,000 events and future inflow were used to evaluate efficiency of the flood control rule curves in showing situations of water shortage and excess water in term of frequency, magnitude and duration. The results showed that obtained rule curves were used to simulate the Nam Oon Reservoir system for reducing flood in long term operation. The results indicated that situations of excess water using the obtained rule curves from the proposed model were smaller than using the current rule curves both for the present and future situations. The new obtained rule curves from the proposed GA and KOA models were better than the existing rule curves in decreasing flood situation.

A NEW OPERATION PRINCIPLE OF SYSTEM THAT COMBINES PHASE-CONTROLLED ACTUATOR WITH DIFFERENT DRIVE FREQUENCIES

Hiroyuki Yaguchi — 2025-12-29

In Japan, the shortage of construction workers and inspectors has become a social problem due to the declining birthrate and aging population. In addition, the slow progress of automation in challenging environments, such as construction sites and bridges, has been pointed out. Although various types of inspection robot have been developed, bridge inspection technology has not been fully established. In this study, the operation of a phase-controlled actuator equipped with vibration components with different drive frequencies is investigated. The phase-controlled actuator, in which a second-harmonic vibration component is coupled to a fundamental-wave vibration component to avoid vibration interference, exhibits excellent propulsive characteristics. To further improve the propulsion characteristics, a prototype actuator system, in which two phase-controlled actuators with different drive frequencies are coupled, is developed. Tests on prototypes show that this system can simultaneously achieve high-speed movement and good traction characteristics. Furthermore, the operation principle of this actuator system is established based on test results. The potential of an inspection device with the proposed actuator for the internal inspection of bridges with a small automatic tapping device is demonstrated.

EVALUATION OF FLASH FLOOD SUSCEPTIBILITY IN RELATION TO LAND USE CHANGES IN CHIANG RAI, THAILAND

Zhaolong Gu — 2025-12-29

Flash floods are among the most destructive natural hazards in mountainous regions, characterized by their rapid onset and severe impact on lives and infrastructure. This study assessed the spatio-temporal evolution of flash flood susceptibility in Chiang Rai Province, Thailand, by integrating remote sensing, Geographic Information Systems (GIS), and hydrological modeling. Using the Flash Flood Potential Index (FFPI), the study analyzed the impact of land use and land cover (LULC) changes on flood risk across three distinct periods: 2007, 2012, and 2018. The model incorporated terrain slope, soil hydrological groups (derived from HYSOGs-250m), land use, and Curve Number (CN) values to generate comprehensive risk susceptibility maps. The results revealed that the entire province falls within Moderate to High-risk categories, with a complete absence of Low-risk zones. A significant shift in susceptibility was observed over the study period, driven primarily by land-use transitions. While the conversion of woodland to agriculture moderately elevated risk levels between 2007 and 2012, the subsequent rapid urbanization of agricultural lands (2012–2018) led to a drastic escalation in vulnerability. Notably, high-risk zones within urban areas increased fivefold (+500%) during this latter period. The FFPI model was validated based on the historical flash flood records from 2019 to 2023, demonstrating a strong spatial correlation between analyzed high-risk areas and actual flash flood occurrences. These findings underscored that anthropogenic land-use changes, particularly uncontrolled urbanization and deforestation, are the primary accelerators of flash flood potential, necessitating rigorous land-use planning and targeted flood-control infrastructure.