62 research outputs found
VARIATIONS OF PORE-WATER PRESSURE RESPONSES IN A VOLCANIC SOIL SLOPE TO RAINFALL INFILTRATION
Get PDFABSTRACT A field monitoring of hydrological response and slope movement in an active landslide area, comprising of volcanic soil, was conducted to have a better understanding of the mechanism of landslide reactivation during a rainfall period. Monitoring instruments consisted of jet-fill tensiometers, inclinometers, open stand-pipe piezometers, and a tipping-bucket rain-gauge. The records of pore-water pressure show that the hydrological responses exhibited some spatial variability, and were mainly influenced by antecedent soil moisture conditions and rainfall patterns. The ingress of wetting front was confined up to the depths of 3 m, and a transient positive pore pressure could develop at a depth of 1 m during a heavy rainfall. More sustained increase in pore-water pressure could develop at deeper soil. Meanwhile, the piezometer records show that the response of groundwater table occur more significantly in the middle and lower portions of the slope, associated with the subsurface topographical features. The analysis of antecedent moisture conditions based on the pore-water pressure measurement data indicates that simplified model of slope hydrology cannot fully explain the spatial and temporal development of the pore-water pressures observed in the soil slop
Seismic microzonation of soil amplification and liquefaction for Padang City
Get PDFThe magnitude 7.6 MW earthquake that occurred on 30 September 2009 in West Sumatera caused significant damages to buildings in the city of Padang related to the phenomenon of amplification and liquefaction. This paper presents the results of the assessment and mapping of amplification and liquefaction, carried out in the coastal area of Padang City. Mapping of soil amplification was carried out in 250 locations using the HVSR microtremor method. Meanwhile, evaluation of the potential for liquefaction was carried out in 95 locations using a cone penetration test-based method. Based on the analysis, Padang City has five seismic susceptibility zonations. Coastal areas, including the sub-districts of Koto Tangah, North Padang, West Padang, and South Padang, are located in high to very high susceptibility to soil amplification and liquefaction. These results are in agreement with the phenomenon of building damage due to amplification and liquefaction during the 2009 earthquake
IN SITU MEASUREMENT OF THE SOIL MOISTURE CONTENT PROFILE AT A DECOMPOSED GRANITE CUT-SLOPE
Get PDFABSTRACT Two selected sites at a decomposed granite cut-slope were instrumented with a rain gauge and a series of ThetaProbes installed at depths up to 90 cm from the slope surface. The objective of this study was to evaluate the significance of antecedent soil moisture conditions in controlling the hydrologic responses of the soils at each site. The antecedent moisture content of the soil in Site #1, in general, increases with depth. The response of the soil to saturation process is more or less confined to the shallow depth. On the other hand, the measurement data of the soil in Site #2 showed that the near surface soil exhibits higher antecedent moisture condition than the deeper soil. The ingress of the wetting front could reach more than 90 cm depth during long period of rainfall. Thus, these results suggest that the hydrological response of the soils is spatially variable and is influenced by the antecedent soil moisture conditions within the soil profile. The presence of soil layers, the distribution of macro cracks within the soil profile, and additional lateral source of moisture may also have significant influences on soil response to saturation process
MIKROZONASI SEISMIK WILAYAH KOTA PADANG BERDASARKAN PENGUKURAN MIKROTREMOR
Get PDFPeristiwa gempa bumi pada tanggal 30 September 2009, dengan skala intensitas VII-VIII, mengindikasikan bahwa wilayah Kota Padang rentan terhadap amplifikasi tanah. Makalah ini menyajikan hasil analisis rasio spektra H/V untuk menghasilkan mikrozonasi kerentanan amplifikasi berdasarkan pengukuran mikrotremor. Hasil analisis menunjukkan variasi nilai periode predominan dan faktor amplifikasi yang dipengaruhi oleh jenis lapisan tanah dan struktur bawah permukaan. Berdasarkan variasi nilai faktor amplifikasi, wilayah Kota Padang dapat diklasifikasikan menjadi 5 (lima) zonasi kerentanan amplifikasi. Kawasan perumahan kepadatan tinggi, perdagangan dan perkantoran di wilayah kecamatan Nanggalo, Padang Utara, Padang Barat dan Padang Selatan berada di zona kerentanan tinggi hingga sangat tinggi terhadap bahaya amplifikasi. Hasil zonasi ini sesuai dengan fakta-fakta kerusakan bangunan akibat fenomena amplifikasi yang terjadi pada gempa bumi 30 September 2009.The 30 September 2009 earthquake event with intensity VII to VIII (MMI scale) indicated that Padang City region is prone to soil amplification. This paper presents the results of H/V spectral ratio analysis to produce a microzonation map of amplification for Padang City based on microtremor measurement. The analysis of microtremor data shows that the predominant period and amplification factor of the soils are spatially varied and influenced by soil types and subsurface structure. On the basis of amplification factor, Padang City is classified into 5 (five) zones. High and very high susceptible zones are mainly concentrated in the very dense residential areas, trade and office areas, including the districts of Nanggalo, Padang Utara, Padang Barat, and Padang Selatan. The predicted amplification susceptibility zones are in a good agreement with the phenomena of building damages due to amplification during the 2009 earthquake
Utjecaj geoloških i oborinskih uvjeta na analizu stabilnosti padina u modeliranju plitkih klizišta korištenjem TRIGRS modela
Get PDFWest Java Province has a high potential for susceptibility to landslides. West Bandung Regency is one of the regions in West Java which has high occurrences of landslides triggered by rainfalls. Rainfall-induced landslides in this region have occurred 165 times during rainfall in the last ten (10) years. An effort to predict the landslide occurrences in this region requires the knowledge of factors affecting the hillslope stability. This paper aims to (1) evaluate the parameters affecting slope stability, (2) determine rainfall characteristics affecting slope, and (3) evaluate the performance of TRIGRS modelling. This study applies a deterministic method using the model of TRIGRS to analyze the effect of one-day antecedent rainfall intensity on the instability of hillslopes. The parameters used in this study are based on field investigation, geological and topographical maps, soil engineering properties, and historical rainfall data. The effect of one-day antecedent rainfall intensity was considered in two scenarios, i.e. 6 hours and 12 hours of antecedent rainfall. Modelling results show that hillslope instability in the study areas is affected by many factors, such as hilly morphology, steep slopes, low shear strength parameters, weathering of volcanic rocks, and the lineament density of geological structures. The modelling simulation also indicates that landslide occurrences in this study area are initiated by a long antecedent rainfall period. Based on ROC analysis, the TRIGRS model shows that the model performance evaluation is in good agreement for modelling slope stability against actual landslide events.Provincija Zapadna Java ima visok potencijal za podložnost klizanju. Regija West Bandung u Zapadnoj Javi područje je s čestom pojavom klizišta koja su izazvana oborinskim događajima. Klizišta inicirana oborinom u istraživanome području dogodila su se 165 puta tijekom posljednjih 10 godina. Predviđanje pojave klizišta u ovoj regiji zahtijeva poznavanje faktora koji utječu na stabilnost padine. Ciljevi su ovoga rada: (1) procijeniti parametre koji utječu na stabilnost padine, (2) odrediti oborinske uvjete koji utječu na stabilnost padine i (3) procijeniti učinkovitost TRIGRS modeliranja. U okviru ovoga istraživanja primijenjena je deterministička metoda korištenjem TRIGRS modela u svrhu analize utjecaja intenziteta jednodnevne oborine koja je prethodila pojavi nestabilnosti na padini. Parametri korišteni u ovome istraživanju temelje se na terenskim istraživanjima, geološkim i topografskim kartama, inženjerskim svojstvima tla te povijesnim podatcima o oborinama. Učinak intenziteta jednodnevne prethodne oborine razmatran je u dvama scenarijima, tj. da je oborina trajala 6 sati i 12 sati. Rezultati modeliranja pokazali su da na stabilnost padina u istraživanome području utječu mnogi čimbenici poput brežuljkaste morfologije, strmih padina, niske posmične čvrstoće materijala, trošenja vulkanskih stijena i gustoće lineamenata geoloških struktura. Rezultati modeliranja također pokazuju da su pojave klizišta u istraživanome području inicirane dugotrajnim prethodnim oborinama. Na temelju ROC analize može se zaključiti kako rezultati TRIGRS modela korišteni u svrhu modeliranja stabilnosti padine dobro koreliraju sa stvarnim pojavama klizišta
Analisis Potensi Likuifaksi Akibat Gempa Bumi Menggunakan Metode SPT (Standar Penetration Test) Dan Cpt (Cone Penetration Test) Di Kabupaten Bantul, Yogyakarta
No full textGempa bumi yang terjadi di daerah Bantul, Yogyakarta pada 27 Mei 2006 dengan magnitudo gempa bumi sebesar 6.3 SR dapat menyebabkan terjadinya bahaya likuifaksi yang dapat merusak bangunan khususnya di wilayah Bantul Yogyakarta. Investigasi geoteknik yang telah dilakukan di Bantul, Yogyakarta dapat memberikan gambaran lapisan tanah yang berpotensi terjadinya likuifaksi. Analisis potensi likuifaksi dilakukan berdasarkan data SPT (Standard Penetration Test) dan CPT (Cone Penetration Test) dengan percepatan maksimum tanah menurut Gutenberg Richter di daerah penelitian rata-rata bernilai sebesar 2.93 m/s2 dan menurut Donovan sebesar 2.88 m/s2. Hasil analisis penelitian menunjukan bahwa lapisan tanah yang berpotensi likuifaksi didominasi oleh jenis tanah pasir lanauan da lanau pasiran yang berada pada kedalaman 0.2 – 3 m, 0.4 m, 2.4 m, 3.6 m, 7.6 – 7.8 m dan 8.2 m. Pengaruh percepatan maksimum tanah menurut Gutenberg Richter lebih besar terhadap terjadinya likuifaksi daripada menurut Donovan. Perbandingan hasil analisis potensi likuifaksi antara data SPT (Standard Penetration Test ) dan CPT (Cone Penetration Test) pada daerah penelitian menunjukan adanya kesamaan potensi likuifaksi pada lapisan tanah dengan kedalaman yang sama diantaranya pada kedalaman 0.2 m-4 m, dengan nilai Cyclic Strees Ratio (CSR) rata-rata sebesar 0.2, sedangkan berdasarkan nilai Cyclic Resistance Ratio (CRR) terdapat perbedaan nlai. Analisis berdasarkan data CPT lebih baik daripada data SPT karena data CPT lebih rapat daripada data SPT.
The earthquake that occurred in Bantul, Yogyakarta on May 27, 2006 with the magnitudo of the earthquake of 6.3 SR can caused liquefaction hazard which could damage to teh building in the municipals of Bantul, Yogyakarta. Geotechnical investigation was carried in Bantul Yogyakarta, can give information about liquefaction hazard in soil layer. The liquefaction potential lanalysis was conducted using SPT and CPT methods, with Gutenberg-Richter’s maximum ground acceleration is 2.93 m/s2 and Donovan’s maximum ground acceleration is 2.88 m/s2. Result of liquefaction analysis indicate that the soil layer domination of silty sand dan sandy silt at the depth of 0.2 – 3 m, 3.6 m, 4 m 7.6 – 7.8 m and 8.2 m. Gutenberg-Richter’s maximum ground acceleration having influential for liquefaction potential better than Donovan’s maximum ground acceleration. Ratio result of liquefaction was conducted using SPT same as soil layer with CPT in resech location at the depth 0.2 m-4 m, with value Cyclic Strees Ratio (CSR) is 0.2. Even value Cyclic Resistances Ratio (CSR) have different value. The liquefaction potential lanalysis was conducted using CPT method better than SPT methods
Surface Rupture and Geotechnical Features of The July 2, 2013 Tanah Gayo Earthquake
Get PDFDOI:10.17014/ijog.3.2.95-105An assessment of surface rupture and collateral ground failures can help to evaluate the impact of future earthquakes. This paper presents the results of a field survey conducted to map the surface rupture and geotechnical phenomena associated with the ground shaking during the July 2, 2013 earthquakes in Tanah Gayo Highland. The objectives of this survey are to document and to characterize the surface ruptures as well as to identify types of earthquake-induced ground failures. Results of the survey identified four best sites of possible surface rupture. Two locations are obvious surface ruptures that can be traced on primary topographic feature of the active fault segment from the north to the south, crossing Pantan Terong Hill. The fault segment has a total mapped length of 19 km, with WNW trending zone and a dextral rupture offset. The ground shaking also resulted in landslides and liquefaction in areas underlain by very fine-grained tuffaceous sands. Based on the field survey, it can be concluded that the newly defined active fault segment, the Pantan Terong segment, is likely the segment that ruptured at the July 2, 2013 Tanah Gayo earthquake. Due to the soil types and unstable rocky slopes in the hilly Central Aceh region, large-scale landslides are primary risks during an earthquake event in this region.</p
Rain-Induced Failure of Railway Embankment at Double Track Lane at Bogor and Its Countermeasure
No full textEvaluation of liquefaction potential in flow liquefaction area in Palu City after the 28
No full textThe occurrence of flow liquefaction phenomena, locally termed Nalodo, during the Donggala-Palu earthquake on 28 September 2018 destroyed some residential areas and infrastructures in Palu City and Sigi Regency. Evaluation of liquefaction potential in the flow liquefaction areas is required to assess the liquefaction susceptibility of the area to future earthquakes. This paper presents the results of liquefaction potential analysis in the Balaroa, and Petobo areas based on the SPT method. A calculated peak ground acceleration was used for each location. Based on the analysis, all the liquefied soil layers are still liquefiable, especially in the Balaroa area, causing a significant ground settlement. These results imply that flow liquefaction areas are still susceptible to liquefaction during a big earthquake event. Thus, restriction of re-inhabitants in the liquefaction areas is necessary, and the infrastructure development in the areas requires a proper engineering design to mitigate earthquake-induced liquefaction hazards in the future
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