Journal of Applied Geology
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Geo-mechanics and Hydraulic Conductivity Study of Claystone in Boyolali, Central Java, Indonesia
Get PDFClaystone middle Miocene age were found in Wonosegoro sub-district, Boyolali region, Central Java, Indonesia. The purpose of the paper is to examine and discuss the geology and typical behavor of this claystone and its micro-level mechanism. The hydraulic conductivity was assessed using consilidated apparatuses; 150 mm diameter column mound using aggregated sample and 60 mm oedometer mould using slurry sample as a reference. Claystone materials used were treated under various conditions. In long term test under constand vertical stress and hydraulic gradient, the hydraulic conductvity decreases with time although the volume of void volume of the sample increased by swelling. Water contens of the individul aggregated increased by swelling, by which strength of particles decreases with and aggregate breakdown was enchanced. As a result, large void created by large particles could be redused in its size, leading the reduction of hydraulic conductuvity. The hydralic conductivities (K values) obtained from the aggregated sample varied in a broad range compared with those from slurry sample. In the test using the higher percentage of gravel-sized aggregate (up until couarse gravel-sized; retained in 26.5 mm sieve), K values changed from 10-5 to 10-7 m/s under vertical stresses from 5 up to 245 kPa. The test was repeated using smaller percentage of gravel-sized aggregate (up until fine gravel-sized, retained in 4.75 mm sieve) and the observed K values changed from 10-5 to 10-10 m/s. While the K values obtained in the specimen made from surry under same vertical stresses was 10-9 to 10-11 m/s. All of the extruded aggregate samples had higher water content than the initial ones, which suggest the alteration mechanism of soled consolidation phase to more deformable plastic phase, whice enables thesample to decrease the void size. These results conclude that using coarse gravel-sized aggregated, which is a reasonable scenario of a practically feasible aggregate size in a field, may noy produce the aimed hydraulic conductivity by the regulated standard. Therefore, breakdown of the aggrgate size and enchament of swelling are crucial factors for the application of the clay stones as a barrier material
Stratigraphy and Foraminiferal Biostratigraphy of Sentolo Formation in Sedayu Area: Local Unconformity Identification in Early Pliocene
Get PDFThe study area is located in Sedayu District, Bantul Regency, Special Region of Yogyakarta Province which belongs to the Sentolo Formation. This area is an interesting place to study because there are erosional boundaries that indicate an unconformity in the Sentolo Formation. In this study, stratigraphic measurements and sampling were carried out in the field, then the samples were prepared and analyzed for the content of planktic and benthic foraminifera fossil. The results of the analysis are the determination of biozonation, paleobathimetry, and identification of sedimentation rates and unconformity. From the data analysis, ware known that the Sentolo Formation in Sedayu area can be divided into three lithofacies, namely thickening upward calcareous sandstone – calcareous siltstone facies, channel calcareous sandstone – calcareous siltstone facies andthinning upward limestone facies. Based on the biostratigraphy analysis, can be divided into four biozonations, namely the PL1A, PL1B, PL1C, and PL2 zones which are included in the Early Pliocene age. There is an unconformity in the facies boundary of the channel calcareous sandstone – calcareous siltstone facies with thinning upward limestone facies, identified by the presence of an erosional boundary at that interval and also supported by sudden changes in paleobatimetry from Upper Bathyal to Middle Neritic. The sedimentation rate identified in this area has a value of 15.5 m / Ma which identified in the lower facies. The extrapolation results of age and sedimentation rates concluded that the unconformity occurred at 4.46–4.20 Ma, and eroded 4.03 m thick of sedimentary rock
Correlation of P-wave Velocity with Rock Quality Designation (RQD) in Volcanic Rocks
Get PDFOne important part of rock mass investigation is the geomechanical assessment in terms of rock mass classification systems. Rock mass classification is one of the most efficient methods in rock mechanics to provide a basic understanding of rock mass characterization. Rock mass properties can be determined by a seismic refraction survey as an indirect geophysical assessment. In this study, the P-wave velocity from seismic refraction was compared with the Rock Quality Designation (RQD) from the boreholes. The empirical correlation between the RQD and the P-wave velocity was found by using the linear regression analysis. The RQD value estimated from the P-wave velocity can beapplied for tropical environment study with geological conditions of volcanic rocks. This study helps to estimate and predict the subsurface rock quality, to reduce investigation costs, and to improve understanding of subsurface rock quality
Landslide Risk Assessment for Designing Monitoring and EarlyWarning System
Get PDFLandslide is the most frequent natural disaster in Yogyakarta, Indonesia. In the mid-March 2018, a few cracks appeared in the north of the hill in the Pendoworejo Village, Kulon Progo District, Yogyakarta Special Province. The landslide movement of this area still threatens the residents and makes them evacuated due to their fear upon potential landslide disaster. In order to reduce the risk, landslide investigation and risk assessment were conducted. The stability analysis focused on the relationship of the displacement,the velocity and the fluctuation of groundwater level due to the rainfall intensity. Then, a monitoring and warning system was designed as a non-structural mitigation effort. Based on the preliminary investigation on April 2018, there was no evidence of mass movement on the west and south part of the hill. On the other hand, the north part area was estimated to have risk as indicated by the occurrence of many cracks. Based on the result of analysis, the fluctuation of the groundwater level rose or dropped substantially before and after heavy rainfall. In the rainy season, the velocity and the displacement increased slightly in the first three months and grew rapidly afterward. In fact, the landslide risk increased in every rainy season. Therefore, the risk could be more dangerous in the future
Rock Mass Characterization for Assessment of Safe Cut Slope and Rock Bearing Capacity at Gondang Dam Site, Karanganyar, Indonesia
Get PDFThis paper presents results of surface rock mass characterization for assessment of safe cut slopes and allowable bearing capacity of foundation rocks at the construction area of Gondang Dam. The rock mass characterization involved determination of intact rock engineering properties and rock mass quality based on the Geological Strength Index. The rock mass characterization results showed that the research area consisted of moderately to highly weathered and very weak to weak andesite breccia and andesite tuff breccia. The andesite breccia had very poor to fair rock mass quality, while the andesite tuff breccia had poor to fair rock mass quality. The research area was divided into three zones of safe cut slope and allowable bearing capacity. Landslides occurred at natural slopes having poor to very poor rock mass quality and inclinations greater than the determined safe cut slopes.The foundation rock of the embankment dam had fair rock massquality and 135–280 T/m2 allowable bearing capacit
Determination of Stability During First Impounding in Jatigede Earth Dam
Get PDFThe Jatigede Dam is a multi-purpose rockfill dam located in Sumedang Regency, West Java Province. The construction of the Jatigede Dam started in 2008 and it is the second largest dam in Indonesia after the Jatiluhur Dam. As one of the vital facilities, it is highly necessary to evaluate the stability of the Jatigede Dam to avoid dam collapse. First reservoir filling is one of the factors affecting the dam stability; therefore, this research aims to evaluate the Jatigede Dam stability during impounding. The transient seepage analysis was conducted to evaluate the pore pressure change during impounding. The result of seepage analysis was used to analyze the dam stability using the limit equilibrium method with Rockscience software of Slide2. The results of the seepage analysis shows that the rise of the reservoir water level affects the upstream slope stability. The safety factor of the upstream slope changes during the impounding process. All thesafety factors for the upstream and downstream slopes during impounding still meet theminimum safety factor criteria required.
Mineralogical Characteristics of Hydrothermally-altered Andesite in Kalirejo Village and The Surrounding Areas, Indonesia
Get PDFType and intensity of hydrothermal alterations affect rock engineering properties and slope stability. Identification of mineralogical characteristics of rocks is essential in determination of rock slope failure mechanism in a hydrothermal alteration zone. This research was conducted to identify mineralogical characteristics of hydrothermallyaltered andesite in Kalirejo Village and surrounding areas, Indonesia. The research was conducted by field observation and laboratory analyses involving petrographic and X-ray Powder Diffraction (XRD) analyses. The results showed that the research area was dominated by argillic alteration type and high alteration intensity implying high susceptibility to slope failure
Geology and Petrogenesis of Igneous Rocks from Batur Paleovolcano, Gunungkidul, Yogyakarta: Evidence from their Textures, Mineralogy, and Major Elements Geochemistry
Get PDFBatur paleovolcano is located in Wediombo Beach area, Gunungkidul Regency, Yogyakarta and is being part of Wuni Formation. Several volcanic products including lava flow, autoclastic breccia and volcanic breccia can be found associated with diorite intrusions. This research is aimed to characterize geological, mineralogical andgeochemical variations of igneous rocks from Batur paleovolcano to understand its petrogenesis. Detailed geological mapping with scale of 1:12,500 is conducted to identify geological aspects and delineate igneous rocks distributions. Igneous rocks and selected wall rocks samples were prepared for laboratory analysis including 8 samples for petrography and 5 samples for ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) analysis. Several geochemical data from previous study are also added to investigate the geochemical variations. Geological condition of the research area consists of four rock units including colluvial deposit, limestone, andesite lava and diorite intrusion. Geological structures found are normal fault and shear joint where the main stress direction is north–south. Petrography analysis showed that igneous rocks in this research area consist of diorite intrusion and andesite lava with phorphyritic texture. Plagioclase become the most abundant minerals found both as phenocryst phase and groundmass. Hornblende only occur as phenocryst phase in minor amounts as accesory mineral. Major elementsgeochemistry analysis showed the rocks are characterized by intermediate silica with low alkali content. They are can be categorized as calc-alkaline series. However, some samples are fall into tholeiitic series. Major elements variation and textural study also indicate the magma is experienced differentiation process by fractional crystallization mechanism. This study suggests that igneous rocks from Batur paleovolcano is formed by two phases of formation. Earlier phase is the formation of andesite lava in island arc tholeiitic tectonic setting then at the later phase is formation of diorite intrusion in the calc-alkaline basalts tectonic setting
The Quality and Distribution of Andesite Rock for Construction Materials in Kokap and Temon District, Kulon Progo Regency, Yogyakarta–Indonesia
Get PDFThe construction projects that are currently being carried out in Kulon Progo Regency, Yogyakarta Special Province, Indonesia, started on 2018, are large-scale projects. The projects include the construction of airports, seaports, industrial estates, southern crossing lanes and the construction of Menoreh lanes. The large-scale projects require a very large supply of andesite rocks for material construction. In Kulon Progo Regency itself, there is a huge potential of andesite rock relate to two geological formations (Kebo Butak and Andesite Intrusion) exist in the region, which is found mostly in Kokap District and partly in Temon District. One parameter that determines the quality of andesite rock is their compressive strength. Due to weathering, not all of the andesite in both formation can be classified as good quality rocks. According to Indonesian Standard, theminimum compressive strength of natural stone for stakes and curbstone is 500 kg/cm2 , for lightweight building foundation is 800 kg/cm2 , for medium building foundations is 1000 kg/cm 2and for heavy building foundations is 1500 kg/cm 2 . Based on this background, this paper have objectives to know the quality of andesite rock exist in the research area and to determine the zonation of good quality andesite rock for building and road materials in the research area. Field observation were conducted to map the occurrence of andesite rock. Totally 68 rock samples were collected during field observation and tested by point load test method to know its compressive strength value. The distribution of good quality rock in the research area were determine based on spatial analysis procedure in geographical information system. Results show that andesite rocks found in research area have a compressive strength ranging from 167.12 kg/cm 2 to 2783.37 kg/cm 2 . From 53 samples taken from igneous rock intrusion, it showed that 7.55 % had low quality, 13.21 % had medium quality, 30.19 % had good quality and 49.06 % had very good quality. From the 16 samples taken from the Kebobutak Formation, it showed that 12.50 % had low quality, 18.75 % had good quality and 67.75 % had very good quality. The final map of rock quality zonation reveals 28.92 % of research area classify as low quality, 2.52 % medium quality, 37.68 % good quality and 30.88 % very good quality. It can be concluded that almost 70 % of andesite in the Kokap and Temon District can be used for the running large scale projects
Chromium Precipitation Activity and Molecular Characterization of Sulfate-Reducing Bacteria
Get PDFChromium is one of the metals used in many areas of industry., However, chromium is toxic to organisms when present in large quantities in the environment. One of the method for treatment of hazardous waste containing chromium in the aquatic environment can be removed by bioremediation using sulfate-reducing bacteria (SRB). Therefore, the purpose of this research were to analyze the chromium precipitation activity of sulfate-reducing bacteria isolated from sulfate reducing bioreactor and its molecular identification using 16S rRNA gene sequences. The result observed that the isolate of sulfate-reducing bacteria (KGP1 strain) has chromium tolerancy ability up to 5 ppm. It also showed that the strain KGP1 could precipitate chromium up to 0.141 ppm (79 %) on 5 days incubation. Based on 16S rRNA gene sequences, this strain identified as Desulfovibrio aerotolerans