Natural Slope Failure on Weathered Andesitic Breccia in Samigaluh Area, Indonesia

Six events of landslides occurred simultaneously on weathered Andesitic Breccia in Samigaluh Area, following the heavy rainfall. Field investigation, laboratory works and slope stability analysis were carried out to assess the mechanism of the failures, their controlling factor and identify the triggering rainfall characteristics. It was found that the rainfall was the key factor inducing the failure. However, further investigation which incorporates slope hydrodynamic numerical modeling is still required, in order to find the triggering rainfall characteristics. In addition, the role of slope inclination was less significant than the soil and vegetation types covering the slopes. Finally, the landslide susceptibility map could be performed to support the prevention system

Rain-Induced Landslide Problem In est Java

A Land Information System (LIS) needs a software package that has capability to handle both graphical and attribute data. This kind of software should be designed for complicated spatial data handling and analysis. In case of the LIS for cadastral applications, most information is only retrieved and manipulated \u27from the system without any spatial analysis processes. This can be managed by an integration of CAD (Computer Aided Designed) and DBMS (Data Base Management System) software packages. This paper discusses graphical and attribute data linking based on the integration of the Microstation 32 (CAD) and Informix-SQL (DBMS) software packages. It covers the database design and model testing. The model testing used a parcel map and its attribute data. The result showed that the system met to the requirements of the graphical and attribute querie

Prediction of rain-induced landsliding by using slope hydrodynamic numerical model

ABSTRACT An accurate prediction of rain-induced landsliding is still difficult to be performed . This is due to the uncertainty in the slope hydrological conditions believed to be the key factor controlling landsliding, as well as the difficulty in observing such conditions. The incorporation of numerical modelling to simulate and predict slope hydrological behaviour in response to rainfall is suggested. The simulation results show that stability of slope with low permeability and shallow groundwater conditions can change within hours in response to rainstorm. How the rain intensity and duration as well as slope hydrological conditions, such as groundwater table, soil permeability and initial slope saturation, control slope stability also can be observed rigorously

Pengaruh Kondisi Vegetasi dan Geologi Terhadap Gerakan Tanah Dengan Pemicu Hujan

The objective of this study was to analyze the role of vegetations in controlling rain-induced landslides. Slope stability analysis based on limit equilibrium concept was adopt to execute such analysis. Numerical model by applying COMBINED HYDROLOGY AND STABILITY MODEL (CHASM) was applied to simulate the changing of slope stability in response to rain infiltration under the control of specific vegetation types. Three different slope models consisting of bedrock of andesitic breccia overlain by clay with various slope inclinations, 15°, 30° dan 45° were selected to be subjected to the various rain intensity of 20 mm/ day, 50 mm/ day, 100 mm/ day dan 160 mm/day. The simulation results showed that bamboo, cassava, paddy (without irrigation) and vetiver significantly prevented the rain-induced landslides only on the gentle slope (being less steep than 45°). In the slope which was steeper than 45° roles of slope inclination and stratigraphy as well as geotechnical properties of rock/ soil forming the slope were more significant than the role of vegetation in controlling slope stability. It was also apparent that paddy with irrigation significantly reduced the slope stability on gentle slope (15°), despite only low rain intensity (20mm/day) applied. Indeed, the rainfall had no important role in inducing landslide on such gentle slope. Those simulation and analysis results were also evaluated by comparing to the real rain-induced landslide cases occurring in several sites in Indonesia

Soil Moisture Suction Of Allophanic And Halloysitic Soils

Soil moisture-suction relationship of allophanic and halloysitic soils were investigated by conducting laboratory test. In comparison with other soil types which did not contain allophane and halloysite, the residual volumetric water content was high. This was due to the water retained inside the micropores in allophanic soil and the intra lattice water in halloysitic soil. In addition, the high amount of organic content in allophanic soil, which was reflected by its dark colour, was also responsible for the high water holdin

Peningkatan Daya Dukung Lempung Ekspansif Dengan Pondasi Bambu Di Daerah Krebet Dan Sekitarnya, Kabupaten Kulon Progo, Yogyakarta

Krebet area is located in Desa Tuksono, Sentolo, Kulon Progo, Yogyakarta. In this area, a lot of residential buildings were damaged which is caused by expansive days. Many floor slabs constructed on an expansive days area crack and heave which is followed by damaging windows, doors, and wall crackings. In order to study the preventive method for residential building damage, the characteristics of some engineering properties and mineralogical composition of clay was identified by test and observation in the field and laboratory. The uses of each test and observation were emphasized for structural stability analysis. . The observation and considerable detail of fieldwork were takenplace in three locations of test pits. The value of undrained shear strength was low (12 kg/cm2 - 24 kg/cm2). It caused the bearing capacity of day, as withholding force, was smaller then the uplifting force. The analysis of structural stability showed that the bearing capacity of day could be increased by three types of foundations. Two layers of raft foundation can reinforce the bearing capacity of day up to 0.50 - 0.93 meter thick, pile foundation up to 0.50 - 1.54 meter thick, and pile foundation with wings up to 0.50 - 2.36 meter thick. One layer raft foundation was not recommended because its capability was still in the tolerance of uplift movement (0.5 - 0.87). The grandstand is recommended when the foundations can not reinforce all of thickness of clay in the study area. Keywords: bearing capacity, shear strength, withholding force, uplifting force, foundation

DETERMINATION OF NUCLEAR POWER PLANT SITE IN WEST BANGKA BASED ON ROCK MASS RATING AND GEOLOGICAL STRENGTH INDEX

Indonesian government through the NationalAtomic Energy Agency has planned to build anuclear power plant. One of the proposed sitesis in West Bangka Regency, Bangka BelitungArchipelago Province. The engineering geologyof this area is, however, not fully understood andrequires further investigations. Engineering geology investigations were carried out by assessing therock mass quality and bearing capacity based onfield observation and drilling data. The assessmentwas conducted using Rock Mass Rating (RMR)and Geological Strength Index (GSI) classifications.The rock masses in the study area were dividedinto four units, namely units of sandstone, granite,mudstone and pebbly sandstone. The RMR andGSI values in the study area were influenced by theparameters of discontinuity space density, the slopeof discontinuity orientation, grade of weatheringand groundwater conditions. The assessment showsthat the granite unit had the best quality which wasshown by a 53 average RMR value and 66 GSIvalue. Based on the average RMR value, the graniteunit was estimated to have cohesion value between0.2 and 0.3 MPa, friction angle between 25° and35°, and allowable bearing pressure between 280and 135 T/m2. Based on the GSI value, the graniteunit was estimated to have uniaxial compressivestrength value between 1.0465 and 183.8 MPa, ten-sile strength between (-0.0122) and (-5.2625) MPa,rock mass strength values between 24.5244 and220.351 MPa, and modulus of deformation withina range of 1.73 - 86.68 GPa. The Granite Unit wasconsidered to be the most appropriate location forthe nuclear power plants

Kondisi Geologi Teknik Daerah Jalur Jalan Cangakan-Sidoladju Kabupaten Ngawi Propinsi Jawa Timur (Studi Kasus : Instabilitas Jalan dan Cara Mengatasinya)

This research is purposed to know the condition of geological engineering along Cangakan Sidoladju road and to study the character of expansive clay as a subgrade of the road that causes road instability. Based on field observation and laboratory work, there are 3 geomorphological units in research area, e.g. a fluvial plain unit, aluvial plain unit, and undulating slope denudational unit. The stratigraphic of the area consists of 6 units, namely marl, limestone , sandstone, breccia, gravel - sand and clay unit. The geological structure which is found, i.e. Gandong dextral strike slip fault. The geological engineering unit of along the road Cangakan - Sidoladju consists of 3 units : black grey/brow clay unit, grey clay unit, dan clay - silt unit. The damaged road was generally resulted from the expansive subgrade of body road in the form of grey-black clay by high plasticity, which has the number of plastic limit (FL) = 60-100, water content (34 -48)%, shrinkage limit (SL) 10 - 16, and clay fraction about (27 - 50)%. The changes of water content which is influenced by rainfall and land used as rice field needs much water, and also the channel of road drainage that did not work properly causes road damage, i.e. crack along the road, undulating of the upper surface, sagging and also sliding in the shoulder of the road. Key words : Geological engineering, Instability, Clay

SUMMARY OF RESEARCH WORK ON THE EVALUATION ON LONG TERM STABILITY OF ARTIFICIAL SLOPE PROTECTION

Application of GPR, RedExplorer1.4 and GeoStudio2004 have been used to evaluate the overall stability condition of a steep slope along Kalibawang irrigation channel km 8.5, Kulon Progo Regency, Yogyakarta Special Province, Indonesia, that this slope slid down in 1990 and was restabilized by cut to be gentler and covered by shotcrete. Topographic map and engineering geological map in scale 1:2000 have been established prior to the detail investigation. Three drilling logs with in-situ test, SPT and CPT, and samplings have been made and sent to soil mechanic laboratory for index properties tests, and a slope profile along the main axe will be also created for stability analysis through GeoStudio2004. Moreover, GPR has been used to run on a full slope surface to detect the distribution of fractures and/or cavities behind the shotcrete and the results have been interpreted by the aid of RedExplorer1.4.Three profiles showing the rate and depth of fractures and/or cavities are established whereas the slope stability analysis through GeoStudio2004 is the next target of the research. The author is expecting the result from the integration of GPR interpretation and GeoStudio2004 to figure out the overall stability with respect to its existing conditions and its own geometry. Keywords: GPR, GeoStudio2004, overall stability, fracture and/or cavities