Journal of Applied Geology
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Slope Stability Analysis Using Electrical Resistivity Tomography and Limit Equilibrium Method: A Case Study from Girimulyo, Kulon Progo
Get PDFGirimulyo sub-district is one of the areas with high landslide risk in Kulon Progo Regency. On March 12, 2018, a landslide occurred in the area. Seven families were affected, and landslide material blocked the road. This study aims to determine slope conditions through electrical resistivity tomography (ERT) and slope stability analysis using the limit equilibrium method. Based on the interpretation of the ERT profile, it is known that a layer with a resistivity value of 150 Ωm is bedrock. The sliding surface is thought to be at the boundary between the wet clay and wet silt layers. The interpretation of the ERT profile is confirmed by data from laboratory tests on soil samples. Slope stability analysis was carried out using ERT profile interpretation and soil sample laboratory test data. The slope stability analysis results show that both the slopes that experienced landslides in 2018 and those that did not experience landslides were stable when the water table was 3 meters deep. However, the landslide slopes are in critical condition as the groundwater level rises, while the non-landslide slopes are remains stable
A GEOTECHNICAL-HYDROLOGICAL APPROACH FOR DEFINING CRITICAL RAINFALL-INDUCED SHALLOW LANDSLIDES AND WARNING SYSTEM AT LARGE SCALE
Get PDFThis study proposes a novel method that combines deterministic slope stability model and hydrological approach for predicting critical rainfall-induced shallow landslides. The method first uses the slope stability model to identify “where” slope instability will occur potentially; the catchment is characterized into stability classes according to critical soil saturation index. The critical saturated soil index is calculated from local topographic components and soil attributes. Then, spatial distribution of critical rainfall is determined based on a hydrological approach under near-steady state condition as a function of local critical saturated soil depth, slope geometric, and upstream contributing drainage areas. The critical rainfall mapping is bounded by theoretically “always stable” and “always unstable” areas. To show how the method works, observed landslides (1985-2008) and a satellite-based rainfall estimates associated with a past new shallow landslide in the Upper Citarum River catchment (Indonesia) were used to validate the model. The proposed study is useful for rainfall triggered shallow landslide disaster warning at large catchment scale.
Keywords: Critical rainfall, slope stability, hydrology, shallow landslide, Citarum River catchmen
CALDERA ACTIVITIES IN NORTH BALI, INDONESIA
Get PDFOne of the most serious natural hazards is largescaled Plinian eruption that forms caldera. Although the probability to have such large-scaled eruption is very low, the result will be catastrophic if it happens. Thus, it is important to clarify features of caldera system including eruption timing, scale of eruption, precursor activity, etc. With enough scientific information, we may be able to mitigate such very rare but extremely large-scaled geohazard. In Bali Island, Indonesia, there are two caldera systems; Batur caldera and Buyan-Bratan caldera. Batur caldera was previously well studied (e.g. Sutawijaya, 2009), whilst Buyan-Bratan caldera’s geological and volcanological features have not been examined at all. The Buyan-Bratan caldera is about 6 km × 11 km in size and contains three caldera lakes. Wellformed several post-caldera cones are covered by thick soil and vegetation and developed from central to southern part of the caldera. BuyanBratan caldera and post-caldera cones are thought to be older than Batur caldera activities. Geothermal manifestation is confirmed within the caldera. Geological features of the Buyan-Bratan caldera and post-caldera cones were clarified by petrographic and petrochemical analyses. Also, KAr ages were obtained for each volcanic edifice in Buyan-Bratan caldera system.
Keywords: Caldera, Plinian eruption, Buyan, Batur, volcano hazard
Electrical Resistivity Tomography and Boreholes Data to Investigate the Near-Surface Structure under the Campus Area of Çanakkale Onsekiz Mart University, Çanakkale, Turkey (Türkiye)
Get PDFWe study the soil foundation underneath the Çanakkale Onsekiz Mart University (ÇOMU) campus, Çanakkale, Türkiye by employing the electrical resistivity tomography – ERT supported by 27 boreholes data. The studied area taking place in southwest Marmara region was historically affected by large earthquakes () created by the North Anatolian Fault system. The boreholes data show that the near surface structure beneath the ÇOMU campus is made of mostly silty sands and marls. A high sensitivity resistivity instrument is used to collect the field data in which nine ERT profiles reaching lengths as long as 315 m are utilized. The current geoelectrical measurements are simulated by using two numerical models to estimate the inversion depth sensitivity from which it is found satisfactory in the depth range 0-30 m and then somewhat decreasing. The observed electrical resistivity values are in the range 2-160 W m. The geoelectrical structure corresponding to the silty sands are represented by low resistivities (40 W m) depth sections are associated with the marl units. The resistivity structure beneath the ÇOMU campus is complex where both low and high resistivity depth sections reside side by side. The groundwater and clay mineralogy contribute to the broad changes in the subsurface resistivities. The groundwater flow below the steep terrain of the ÇOMU campus causes low resistivities (<10 W m) deeper than 10-m depth. The boreholes data superimposed on the two-dimensional (2-D) ERT profiles show consistency with the resistivity-depth distributions at corresponding depths
Geological Investigation of Clay Minerals (Swelling) Pt. Upb Antam Pongkor Bogor, West Java, Indonesia
No full textRocks containing clay minerals can experience rock deformation when interacting with water, this can also caused by the argillic zone, in the underground tunnel at the Unfoloader 600 and Xc 600 loop 2 ciurug. The argillic process that causes actual material swelling that occurs in field causes rock mass around the mining development area to become weak. The location from tunnel cross cut of Unfoloader 600 and Xc 600 loop 2 contain active clay minerals which high percentage composition of swelling mineral material. The Unfoloader 600 location has a mineral swelling composition of 102.94% with 24 hours, justifying potential very high swelling. The minerals present based on XRD testing 70.8% illite, 25.4% kaolinite, 25.4% kaolinite and 3.8% montmorillonite. Location Xc 600 loop 2 has a mineral swelling composition of 131.25% with 24 hours, justifying potential for very high swelling. The minerals present based on XRD testing illite 49.7%, kaolinite 28.7%, quartz 20.3%, and montmorillonite 1.2%. The values obtained based on laboratory form free swelling tests and XRD that the location experienced of rock deformation, it’s swelling in the mining development area
Flood Disaster Prediction Model Using Long Short-Term Memory (LSTM) in Pekalongan, Central Java.
Get PDFPekalongan is located in the northern part of Java Island, directly adjacent to the sea in the north. Natural disasters that often occur in Pekalongan are floods, especially in the north of the area, which has a height of 0 meters above sea level. In addition, Pekalongan also has a relatively low land slope of around 0 – 5%, which makes it challenging to distribute water and construct drainage. This study aims to be able to perform predictive modeling of flood-prone areas for the next five years. This study used eight parameters: rainfall, elevation, slope, distance to the river, distance to the sea, groundwater table to surface, soil type, and land use. This research used the Long Short-Term Memory (LSTM) method to predict rainfall parameters using the Python programming language with Jupyter Notebook software. Later, the data will be used as training and test data. Training data testing and tests are conducted to find the minimum failure or error value. The weight scoring method is carried out on each parameter to indicate areas with a high flood vulnerability level. The results showed that Pekalongan has a medium to very high vulnerability level, with a dominant high vulnerability level. The very high level of vulnerability is prevalent in the northern part of the research area, which is directly adjacent to the sea or in the North Pekalongan District. Floods that occur in the northern part of the study area are not only due to high levels of rainfall but can also occur due to the inflow of seawater towards the mainland resulting from high tides and high sea waves. The southern region of the study area has a smaller vulnerability level than the northern region, which has a medium to high vulnerability level.Keywords: Flood ∙ Hazard ∙ Precipitation ∙ LSTM ∙ Rainfal
REAL-TIME MONITORING AND EARLY WARNING OF LANDSLIDES AT RELOCATED WUSHAN TOWN, THE THREE GORGE RESERVOIR, CHINA
Get PDFA total of 4200 landslides have been identified in the Three Gorges Reservoir area. It is planned that a total of 3200 landslides (i.e., 75% of the total number of landslides) will be monitored. Since 2003, the authors have carried out a geo-hazard real-time monitoring and early warning project at relocated Wushan town (Wushan new town) in the Three Gorges Reservoir area. Its purpose is to establish monitoring and early warning demonstration station. The station has three main functions: (1) Internet-based, (2) Comprehensive monitoring, and (3) Early warning. Based on the landslide monitoring experience at the Three Gorges Reservoir area, the early warning critical value at Wushan new town is established and presented in this paper. The critical situation is divided into four levels: I level early warning (indicated as blue), II level early warning (indicated as yellow), III level early warning (indicated as orange), and IV level early warning (indicated as red). Judging from the Yuhuangge landslide monitoring data in this area since 2004, the Wushan new town is at the blue early warning level. However, monitoring data of displacement at deep borehole showed that the displacement increased 5 mm in five months with an average velocity 1.0 mm/month. The velocity is 10 times higher than that at the early deformation stage. For this reason, the early warning level is changed from blue to yellow, which means an accelerated deformation period and emphasizes the need for denser monitoring.
Keywords: Landslide, Three Gorges Reservoir, real-time monitoring, early warnin
SEISMIC HAZARD ASSESSMENT OF SCHOOL BUILDINGS IN PENINSULAR MALAYSIA
Get PDFPeninsular Malaysia is located on the southern edge of the Eurasian Plate. However, it is close to a seismically active plate boundary, the inter-plate boundary between the Indo-Australian and Eurasian Plates. Occasionally, tremors can be felt throughout the region even when active faults are located several hundred kilometers away. Lessons learnt from past events, active earthquakes located far from the existing building can cause potential damage. Thus, fragility curves become an essential tool to estimate probability of building damage caused by seismic ground motions. In this study, the response of low-rise and mid-rise RC school buildings located in various soil conditions within Peninsular Malaysia under earthquake excitation was investigated by performing dynamic response spectrum analysis. These buildings were analysed using DIANA 9.3 structural analysis program and subjected to a range of low to high seismic ground motions to determine the performance damage state of each type of building. All structural elements were modeled using solid brick finite-element. Correspondingly, the fragility curves were developed using the log-normal distribution for structural response. The effects of various soil conditions on the response of the buildings were also investigated. The results indicated that the effect of soil parameters had a significant effect on the outcome of the fragility curves. However, the risk of these existing school buildings at a location in the northern part of Peninsular Malaysia showed the highest probability of exceeding each damage state. On the contrary, the risk of the existing school buildings at a location in the central part of Peninsular Malaysia was the lowest.
Keywords: Interaction, fragility curves, soil-structur
Geochemical Characteristic of the Carbonaceous Sediments of the Upper Paleozoic Kuantan Group, Malaysia
Get PDF The geochemical parameters discussed in this paper are based on an average values of twelve outcrop carbonaceous samples, mainly black shales, were determined using X-Ray Fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) techniques, representative of Charu, Sagor, and Permian formations.The aim of this study is to define and discuss their characteristics, the distribution abundance of major and minor elements, investigation the dominant mineralogical composition and reconstruct the depositional environment for these sediments.The bulk chemical result showed that, the average values of the major elements are 65.83%, 64.82 %, 71.4 % SiO2, 18.27 %, 22.2 %, 15.66 % Al2O3, 1.53 %, 0.99 %, 2.49 % Fe2O3. 4.06 %, 6.25 %, 3.66 % K2O , whereas in the case of the miner elements, the results read values of 524.4 ppm, 758.8 ppm, 446.3 ppm Ba , 366 ppm, 399.3 ppm, 257.3 ppm Rb, 88 ppm, 67.3 ppm, 47.3 ppm Sr , 308 ppm, 288.8 ppm, 327ppm Zr for the Charu, Sagor, and Permian formations respectively. The major oxides reflect the dominant mineralogical composition of quartz and other silicate minerals (e.g. illite, kaolinte, smectite) and deficiency in carbonates.The high Rb/K ratio suggests brackish marine environment or rapid depositions that prevent equilibrium between Rb and K in these study shales and marine environment. The high Rb/Sr ratios of 4.16, 5.89 and 5.44 for the Charu, Sagor, and Permian formations respectively possibly attributed to the lowest contents of Sr content due to reducing environment prevailing during deposition of these sediments.
INFLUENCE OF GEOLOGICAL CONDITION TOWARDS SLOPE STABILITY ON LANDSLIDE: CASE STUDY IN TENGKLIK VILLAGE, TAWANGMANGU DISTRICT, KARANGANYAR REGENCY, CENTRAL JAVA PROVINCE, INDONESIA
Get PDFA rain-induced landslide has occured in Guyon Village, Tengklik Tawangmangu District Karanganyar Regency, Central Java Province, Indonesia on February 2009. The movement was initiated by crack occurrence, 30 cm in depth and 2 meter in length. Such crack continuously developed in depth, extention and numbers, until then it resulted in land subsidence up to 260 cm in depth. Accordingly, ten houses were damaged and ten of families must be evacuated. This subsidence is very potential to further grow and create more consequences for human life and houses / land damage. Therefore, this research is carried out to understand the influence of geological factors and rainfall to the landslide phenomena. This research conducted engineering geology investigation such as mapping, drilling, insitu test, XRD test, soil mechanic test and slope stability analysis by limit equilibrium method i.e. Seep/W and Slope/W. By those research activities, the cause and mechanism of landslide can be understood. Rainfall characteristics which triggered such landslide can also be identified.
Based on those investigations, it is found that the landslide occurred in slow rate sliding (creep) due to the control of slope stratigraphy conditions and gentle slope inclination, which is induced by rainfall. Stratigraphy condition that plays important role in landslide mechanism are the permeable layers consisted of sandy silt (shear strength 12 kPa) and silty sandstone (shear strength 18 kPa) overlaid above impermeable andesite breccia (shear strength 104 kPa). Undulating slope may induce landslide in creep rotational type. Based on slope stability simulation, it is known that rainfall triggered landslide is rainfall 20 mm/ day average precipitation in 55 days and rainfall 20 mm/ day average precipitation in 49 days followed by one day with 178 mm/ day average precipitation.
Keywords: Landslides, slope stabilit