#1INTERNATIONAL CONFERENCE ON EARTH Slope Movement Characteristics and Models based on Engineering- geological Properties of the Menoreh Hills, Purworejo Regency, Central Java, Indonesia SCIENCE, MINERAL ENERGY Sari Bahagiarti Kusumayudha¹, Ayu Narwastu Ciptahening¹, Heru Sigit Purwanto¹, Wisnu Aji Kristanto¹, Nandra Eko Nugroho¹ Universitas Pembangunan Nasional Veteran Yogyakarta Yogyakarta, 3 October 2019 ICEMINE 2019.#2INTRODUCTION • The Menoreh Hills belong to three regencies, Purworejo District, and Magelang District in Central Java province, and Kulonprogo Regency of Yogyakarta Special Region. There are mass movement occurrences almost in every rainy season, that may involve either soil, rocks, or debris, frequently result in losses, both material, infrastructure, and life. The last disaster occurred in December 2018, in the village of Tlogorejo, Kaligesing district, as many as 4 (four) families/16 peopel were affected. Landslides also caused access to the village road Tlogorejo - the village of Sudimoro was covered by avalanches and could not be passed by 4 wheels-vehicle. • In order for prevention and anticipation of further landslides, it is necessary to identify the characteristics of common mass movement occurrence in Menoreh hills. Therefore, the purpose of this study is to identify and analyze, investigate the causes or influencing factors, learn their characters, and draw a conceptual model of mass movements of Menoreh Indslides. CONFERENCE INTERNATIONAL EARTH • The study area is located in the Purworejo Regency, including Kaligesing, Purworejo ONE Bener, Gebang and Bagelen districts, Central Java province, and small portion is s in Kulonprogo Regency, Yogyakarta Special Region. Yogyakarta, 3 October 2019 SCIENCE ICEMINE 2019 MINERAL AND ENERGY 6#3Location Map of the Study Area Jawa Sea INDONESIA JAWA TENGAH PROVINSI (PROVINCE) MAP Jepara Pati Rembang Kudus Kota Tegal Kota Pekalongan Semarang Demak Brebes Jawa Barat Tegal Batang Kendal Pekalongan Kota Semarang Blora Grobogan Pemalang INDONESIA Semarang Purbalingga Temanggung Salatiga Wonosobo Sragen Banjamegara Banyumass Kata Mangelang Jawa Tenga Mangelang Boyolali Surakarta Jawa Timur Karanganyar Cilacap Kebumen Purworejo Klaten Sukoharjo IHALLAND APPINES Yogyakarta Wonogiri The Study Area 0 0.2 0.4 0.6 0.8 OCEAN Meters AUSI RALIA Copyright ©2014 www.mapsofworld.com INDIAN Legend Coastline Provinsi Boundary Provinsi Capital EARTH INTERNATIONAL CONFERENCE ON Yogyakarta, 3 October 2019 SCIENCE, MINERAL AND ENERGY 6 ICEMINE 2019#4The Physiographic Map of Central Java (Van Bemmelen, 1949) Java Sea SEMARANG REMBANG MILLS NORTH SERAYU MOUNTAINS SOUTH SERAYU MOUNTA Indian Ocean PHYSIOGRAPHIC SKETCHMAP OF CENTRAL JAVA Modified from R. W. Van Bemmelen (1970) KENDENG RIDGE Legend Kulonprogo SOUTHERN MOUNTS OF EAST JAVA N Aluvial plains of Northern Java Bogor, North Serayu, Kendeng Anticlinarium Central Depression Zone of Java and Randublatung Zone Domes & ridges in the Central Depression Quartenary Volcanoes Rembang Madura Anticlinarium Southern Mountains Zone EARTH INTERNATIONAL CONFERENCE ON Yogyakarta, 3 October 2019 SCIENCE, MINERAL AND ENERGY 6 ICEMINE 2019#5METHOD OF STUDY ● • Approach method applied in the study was field surveying, surface geologic and geomorphologic mapping, topographic interpretation, remote sensing, petrologic analysis, rock/soil properties analysis, and geologic structure assessment. Survey and mapping were done to identify the variation of physical characteristics and distribution of the lithology. Geologic structure assessment and measurements were held for recording the strike and dip of the joint or fault planes, and also for identifying the morphology such as hills, ridges, and valleys. Topographic and image interpretation were utilized for determining pattern and orientation of fracture system (joint, fractures, fault) also hills and valleys lineaments. • ON INTERERENCE To do mass movement analysis especially that involving soil, it is supported by the use of slide v.6 software. The parameters used include physical properties and mechanical properties of rock/soil samples taken from several slopes in the sty area. Determination of safety factors of the slopes is based on the principle b Bowles (1991) Yogyakarta, 3 October 2019 EARTH SCIENCE, ICEMINE 2019 MINERAL AND ENERGY 6#6Geological Map of the Study Area N DIU ROCK UNIT Unconformity Alluvial Deposits Merapi Deposits Tuffaceous calcareous sst Sentolo Formation GEOLOGIC TIME Quaternary Late Miocene - Pliocene G. Ijo Dacite intrusion Miocene Andesite lava Kaligesing Dukuh Formation Andesite breccia % Fault Oligocene Pressumed Fault Strike & dip of stratification River/flows EARTH INTERNATIONAL CONFERENCE ON Yogyakarta, 3 October 2019 SCIENCE, MINERAL AND ENERGY 6 ICEMINE 2019#7Stratigraphy of the Study Area Tertiary Quaternary Rock Geological Time Symbol Holocene Pleistocene Pliocene Dioritic Intrusion Rock Unit Description Alluvial & Merapi Deposits Unconsolidated materials: clay, sand, gravel, couble, boulder, Layered limestone, Sentolo tuffaceous-calcareous- Late Formation Miocene Middle Oligocene Early Eocene Dukuh Formation sandstone, marl Andesitic breccia, sand- stone with calcareous matrix of marine environment Andesitic volcanic, pyro- Kaligesing clastic, laharic breccia, Formation Nanggulan Formation sandstone, lava of terrestrial environment Quatrz sandstone, marl, claystone, lignite intercalations EARTH INTERNATIONAL CONFERENCE ON Yogyakarta, 3 October 2019 SCIENCE, MINERAL AND ENERGY 6 ICEMINE 2019#8Typical Landslides involving thin soil (left), and involving thick soil (right) found at the main road of Kaligesing District EARTH INTERNATIONAL CONFERENCE ON Yogyakarta, 3 October 2019 SCIENCE, MINERAL AND ENERGY 6 ICEMINE 2019#9No Location Lithology Morphology & topography Result of Soil Slope Stability Analyses in the Study Area Factor of Safety & Soil/Rock Properties Remarks Type of Failure On the top of the Soil of Kalijambe, 1 andesite Village, breccia Moderately steep to steep slope (14%-55%), Structural Hills H = 11.7 m W = 20 m, L = 12.2 m slope = 73°, c = 8.2 kg/cm² f = 5º, g = 10.04 rotational slope there are debris slide 0.448 (unstable) some houses and farming. Soil of Kertosari 2 andesite Village slope, 20%), Moderately steep (14%- H=19,1 m, W = 20 m, = 26.5 m, L debris slide slope rotational breccia Structural Hills = 46° kg/cm² c = 8.9 0.62 (unstable), Terracing for footpath. This slope is located near to the main road Purworejo- Magelang, On Bowles (1991) the top of the f = 12°, g = 11.83 slope, there are perrenials Yogyakarta, 3 October 2019 NI E, MINERAL AND ENERGY CIENCE, ICEMINE 2019#10Result of Soil Slope Stability Analyses in the Study Area No Location Lithology Morphology & topography Soil/Rock Properties Factor of Safety & Type of Failure Remarks The slope is located near to main road in ter connecting Soil of 4 Sukowuwuh Village andesite breccia Moderately steep slope (14%-20%), Structural Hills H = 12 m, W = 16.2 m, 17.7 m, c = 4.1 kg/cm² f = 3º, g = 11.8 L = debris slide villages. The slope = 41° rotational 0.36 (unstable), slope has ever slided, but already overcome by drainage system The location of the slope is near the villager Wadas 5 Soil andesite Village lava Steep slope (21%-55%), Lava Hills H = 7.2 m, W = 19.3 m, L = 8.8 m, slope = 52° c = 2.5 kg/cm2 f = 21°, g = 20.23 debris slide rotational 0.54 (unstable), houses MINERAL AND EN#11No Location Lithology Morphology & topography Soil/Rock Properties Factor of Safety & Type of Failure Remarks H = 5.4 m, W = 21.9 m, L The location of 6 Kamijoro Village Soil of andesite breccia Steep slope (21%-55%), debris slide = 5.6 m, slope = 67° Structural Hills Moderately steep c = 7.8 kg/cm² f = 9%, g = 14.54 H = 7.5 m, W = 18.5 m, rotational 0.73 (unstable), the slope is near the villager houses L The location of Soil of debris slide 7 Jati andesite breccia slope 20%), (14%- = 7.8 m, slope = the slope is near 68° C = 2.5 Structural Hills kg/cm² rotational 0.44 (unstable), the villager houses Moderately steep Soil of 8 Mayungsari Village andesite breccia slope 20%), (14- f = 21°, g = 15.01 H = 6.2 m, W = 22.1 m, L debris slide = 6.8 m, rotational On the top of the slope, there are slope = 62° C 0.54 (unstable), perrenials Structural Hills = 2.5 kg/cm² f =23º, g =16.77#12Result of Rock Slope Stability Analyses in the Study Area No. Name of Slope Lithology Location 1 Wadas Andesite Lava Rock Properties & Class c = 39.1 kPa, f = 47°, g= 2.08 g/cm3, s = 6.62 MPa, RMR = 48 c = 21.8 kPa, f = 40°, 2 Kaliwader A Volcanic Breccia g = 1.81 g/cm3, 3 Kaliwader B Weathered Andesite Lava s = 12.41 MPa., RMR = 45 c = 15 kPa, f = 32°, g = 2.07 g/cm3, s = 6.62 MPa, RMR = 48 Type of Rock Slope Failure Potential Planar slide, sliding direction N254ºE Wedge, sliding direction: N271ºE Wedge, sliding direction: N138°E Wedge, sliding direction: N128°E Yogyakarta, 3 October 2019 INTERNATIONAL ICEMINE 2019 RAL AND ENERGY#13Result of Rock Slope Stability Analyses in the Study Area No. Name of Slope Location Lithology 4 Kaliwader C Andesite Lava 5 Kaliwader D Andesite Lava Rock Properties & Class c = 39 kPa, f = 51°, g = 2.08 g/cm3, s = 6.62 MPa., RMR = 48 c = 39 kPa, f = 51°, g = 2.08 g/cm3, s = 6.62 MPa., RMR = 47 c = 39 kPa, f = 35°, 6 Argosari Weathered Andesite Lava g = 2.07 g/cm3, s = 6.62 MPa., RMR = 48 Type of Rock Slope Failure Potential Unpotential Planar slide, sliding direction: N340°E Wedge, sliding direction: N002°E Wedge, sliding direction: N225°E INTERNATIONAL Yogyakarta, 3 October 2019 • ICEMINE 2019 RAL AND ENERGY#14Typology of slope movements involving soil of Kaligesing Formation in the Menoreh Hills Tensional Crack Volcanic Rocks: breccia, lava, Kaligesing Formation 50 m Soil Joints Volcanic Rocks:. breccia, lava,- Kaligesing Formation 50m Exposed bedrock EARTH INTERNATIONAL CONFERENCE ON Yogyakarta, 3 October 2019 SCIENCE, MINERAL AND ENERGY 6 ICEMINE 2019#15Lava with columnar joint structure, exposed after landslide occurence 2016 in Sidamulya village, Purworejo District EARTH INTERNATIONAL CONFERENCE ON Yogyakarta, 3 October 2019 SCIENCE, MINERAL AND ENERGY 6 ICEMINE 2019#16Based on characteristics and slope movements analyses, the conceptual model of soil and rock slope failures of Menoreh Hill can be established as the following: Type of Rock Involving Materials Geologic Structures Model Figure Soil, weathered Joints, faults rocks, debris Thick to very Soil thick soil, highly weathered rocks (> 3m) Type: Landslide, Sliding Plane: boundary between soil and fresh rock Translational movement Joints, faults Type: Complex soil & debris slide Sliding Plane: Combination of circular and the boundary between soil and the bed rock, complex movement X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Yogyakarta, 3 October 2019 INTERNAT ICEMINE 2019 D ENERGY#17Based on characteristics and slope movements analyses, the conceptual model of soil and rock slope failures of Menoreh Hill can be established as the following: Type of Rock Involving Materials Geologic Structures Model Figure Fresh volcanic Joints, Faults Type: Wedge rocks, breccia, lava Rock Fresh volcanic rocks, breccia, lava Joints, sheeting joint, faults Sliding Plane: intersection of 2 joint planes Type: Block glide Sliding Plane: joint plane, planar shape, translational movement x X X X X x X X X X x X X x x X X X X x X X X X X X X X X X X X X X x x x X X •INTERNATIONAL CONFERENCE ON ICEMINE 2019 ENERGY 6 ON EARTH SCIENCE, MINERAL AND Yogyakarta, 3 October 2019#18CONCLUSIONS • The Menoreh Hills are a dome-shaped physiographic zone, stratigraphy from the oldest to the youngest is Nanggulan Formations, Kaligesing-Dukuh Formation, Jonggrangan Formation, Sentolo Formation, and Quaternary Deposits. • Because the morphology and topography generally display steep to very steep slopes, composed of rocks with quite high weathering rates, controlled by geological structures in the form of joints and faults, and added by high average rainfall, then the area is prone to landslides. CONFERENCE ON EARTH The most common type of mass movement in the Menoreh Hills is landslide. The specific characteristics of landslide in the study area are generally showing the sliding plane which is not an ideal circular shape, but is a plane that is the boundary between soil and fresh rock, or combinati of circular plane and boundary between soil and fresh rocks. Yogyakarta, 3 October 2019 INTERNAL SCIENCE, ICEMINE 2019 MINERAL AND ENERGY 6#19• CONCLUSIONS The conceptual model of mass movements in Menoreh Hills can be grouped into 4 (four), namely landslide with sliding plane in the form of boundary between soil and fresh rocks, landslides with sliding plane as the combination of circular and the boundary between soil and fresh rock, rock planar slides, and rock wedge failure. • This conceptual model is expected able to be used as a reference and guidence for slope stability analysis studies in other locations, especially that is controlled by volcanic (magmatic) arc tectonic environment. EARTH INTERNATIONAL CONFERENCE ON Yogyakarta, 3 October 2019 SCIENCE, ICEMINE 2019 MINERAL AND ENERGY 6#20THANK YOU FOR YOUR ATTENTION EARTH INTERNATIONAL CONFERENCE ON Yogyakarta, 3 October 2019 SCIENCE, MINERAL AND ENERGY 6 ICEMINE 2019