published_or_final_version / Applied Geosciences / Master / Master of Science

published_or_final_version / Applied Geosciences / Master / Master of Science

This thesis investigates the mechanism of a slow moving landslide through a case study based on a full-scale field monitoring conducted in a slow moving natural slope. The slope is gentle and located within a southwest-trending valley which is about 500 meters long with an average slope angle of 17°. The slope is mainly consisted of a thin colluvium top layer and a thick completely decomposed andesite layer underneath. The slope was intersected by a natural drainage channel at its toe. Previous records indicate that the slope moved slowly during or after rainfall but there is still lack of sufficient information allowing one to fully understand the mechanism. To characterize soil properties of the slope, a detailed site investigation and laboratory tests were carried out prior to the instrumentation. The full-scale comprehensive field instrumentation had been completed at the end of 2007. The real-time monitoring system was consisted of a rain gauge, vibrating wire piezometers, moisture probes, WTDRs (water time-domain reflectometry), jet-fill tensiometers, in-place inclinometers and an automatic data acquisition system with wireless transmission ability. Field monitoring of the slope was successfully conducted for two years between 2008 and 2009. With the monitored data, spatial distribution of groundwater levels in two years was obtained. The variations of groundwater levels were analyzed with hourly rainfall; groundwater responses during selected rainfall events were also analyzed. Moisture contents and matric suctions within the shallow soils at the site were monitored and analyzed. Field measured Soil-water Characteristic Curves (SWCCs) were obtained and compared with the laboratory measured SWCCs. Variations of moisture contents measured in deep soils were also analyzed. Based on the monitored results of the hydrogeological responses; a hypothetical conceptual hydrogeological model was proposed. The subsurface deformations recorded by the inclinometers were analyzed and the deformation mode of the site was also discussed. A coupled seepage and deformation analysis was conducted based on the finite element program ABAQUS. Then, the numerical simulation results were compared with field monitored data. Consequently, the simulation results verified the hypothetical conceptual hydrogeological model. It is believed that the deformation of the slope is mainly associated with the quick rise of the groundwater table during or after the heavy rainfalls. Finally, conclusions and recommendations for future research on natural terrain landslide were given. It is hoped that the study of the slow moving slope can provide a useful reference for the future research. / published_or_final_version / Civil Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Geography / Master / Master of Geographic Information System

published_or_final_version / Politics and Public Administration / Master / Master of Philosophy

published_or_final_version / Geography and Geology / Master / Master of Philosophy

published_or_final_version / Geography and Geology / Master / Master of Philosophy

published_or_final_version / Earth Sciences / Doctoral / Doctor of Philosophy

by Wong, Tak-yee Tammy. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves 170-178). / ABSTRACT --- p.i-iii / ACKNOWLEDGEMENTS --- p.iv-v / TABLE OF CONTENTS --- p.vi-x / LIST OF FIGURES --- p.xi-xii - / LIST OF PLATES --- p.xiii-ix / LIST OF TABLES --- p.x-xii / Chapter CHAPTER I: --- INTRODUCTION --- p.1 / Chapter 1.1 --- Introduction --- p.1 / Chapter 1.2 --- Research Questions --- p.5 / Chapter 1.3 --- Study Significance --- p.7 / Chapter 1.4 --- Organization of the Thesis --- p.8 / Chapter CHAPTER II: --- LITERATURE REVIEW --- p.10 / Chapter 2.1 --- Introduction --- p.10 / Chapter 2.2 --- Nature of Landslides --- p.10 / Chapter 2.2.1 --- Landslide Classification --- p.10 / Chapter 2.2.2 --- Morphometry of Landslides --- p.12 / Chapter 2.2.3 --- Factors Affecting Landslide Occurrence --- p.16 / Chapter 2.2.3.1 --- Gradient --- p.19 / Chapter 2.2.3.2 --- Slope Shape --- p.21 / Chapter 2.2.3.3 --- Aspect --- p.22 / Chapter 2.2.3.4 --- Vegetation --- p.24 / Chapter 2.2.3.5 --- Drainage --- p.26 / Chapter 2.2.3.6 --- Precipitation/Seismicity --- p.26 / Chapter 2.2.3.7 --- Lithology and Geological Influences --- p.28 / Chapter 2.2.3.8 --- Regolith --- p.29 / Chapter 2.2.3.8.1 --- Hydrological Properties of Soils --- p.29 / Chapter 2.2.3.8.2 --- Engineering Properties of Soils --- p.30 / Chapter 2.3 --- Data Sources for Landslide Studies --- p.31 / Chapter 2.3.1 --- Aerial Photo Interpretation (API) --- p.32 / Chapter 2.3.2 --- Remote Sensing --- p.34 / Chapter 2.3.3 --- Field Survey --- p.35 / Chapter 2.3.4 --- Subsurface Investigation --- p.36 / Chapter 2.4 --- Landslide Studies in Hong Kong --- p.36 / Chapter 2.5 --- Applications of GIS on Landslide Studies --- p.38 / Chapter 2.5.1 --- Major Data in GIS for Landslide Studies --- p.39 / Chapter 2.5.1.1 --- Triangulated Irregular Network (TIN) as a Representation of Surface --- p.39 / Chapter 2.5.2 --- Applications --- p.42 / Chapter 2.5.2.1 --- Inventory --- p.43 / Chapter 2.5.2.2 --- Landslide Hazard Assessment --- p.43 / Chapter 2.5.2.2.1 --- Statistical Modeling --- p.46 / Chapter 2.5.2.2.2 --- Physical Processes or Three- Dimensional Modeling --- p.50 / Chapter 2.6 --- Suggestions for Future Research Directions --- p.51 / Chapter CHAPTER III: --- STUDY AREA --- p.54 / Chapter 3.1 --- Location and Choice of Study Area --- p.54 / Chapter 3.2 --- Climatic Aspects --- p.56 / Chapter 3.3 --- Geological Aspects --- p.62 / Chapter 3.3.1 --- General Information of GASP V --- p.62 / Chapter 3.3.2 --- Rock Types Specific to the Two Sites Chosen --- p.63 / Chapter 3.3.2.1 --- Volcanic Units - Repulse Bay Formation --- p.65 / Chapter 3.3.2.2 --- Sedimentary Units - Port Island Formation (PI) --- p.65 / Chapter 3.4 --- Geomorphological Aspects --- p.66 / Chapter 3.4.1 --- General Information of GASP V --- p.66 / Chapter 3.5 --- Erosion and Stability --- p.67 / Chapter 3.6 --- Vegetation --- p.67 / Chapter 3.7 --- Summary --- p.70 / Chapter CHAPTER IV: --- DATABASE CONSTRUCTION AND MANIPULATION --- p.71 / Chapter 4.1 --- Data Collection --- p.73 / Chapter 4.1.1 --- Aerial Photo Interpretation (API) --- p.73 / Chapter 4.1.1.1 --- Landslip Inventory --- p.75 / Chapter 4.1.2 --- Field Techniques --- p.78 / Chapter 4.1.2.1 --- Slope Failure/Deposit Field Survey sheet --- p.78 / Chapter 4.1.2.2 --- Collection of Landslide Data --- p.79 / Chapter 4.1.3 --- Collection of Existing Data --- p.80 / Chapter 4.1.3.1 --- 1:5000 Topographic Maps --- p.80 / Chapter 4.1.3.2 --- Terrain Classification --- p.81 / Chapter 4.1.3.3 --- WWF Vegetation Database --- p.85 / Chapter 4.2 --- Data Input and Conversion --- p.86 / Chapter 4.2.1 --- Digitizing of Data --- p.87 / Chapter 4.2.1.1 --- Landslip Capture in Stereocord --- p.87 / Chapter 4.2.1.2 --- Data Conversion --- p.94 / Chapter 4.2.1.2.1 --- Topographic Maps - Scanning and Vectorization --- p.94 / Chapter 4.3 --- Data Editing --- p.94 / Chapter 4.3.1 --- Line Cleaning for Landslide Coverage --- p.96 / Chapter 4.3.2 --- Line Cleaning and Height Tagging for Topographic Map --- p.96 / Chapter 4.3.3 --- Editing on Terrain Classification Map --- p.97 / Chapter 4.4 --- Database Construction --- p.97 / Chapter 4.4.1 --- Data Base Design --- p.97 / Chapter 4.4.1.1 --- Graphical Data Base --- p.98 / Chapter 4.4.1.2 --- Attribute Data Base --- p.99 / Chapter 4.4.2 --- Creation of a Triangulated Irregular Network (TIN) --- p.104 / Chapter 4.5 --- Data Preparation and Pre-analysis Manipulation --- p.105 / Chapter 4.5.1 --- Extraction of Terrain Variables from TIN --- p.105 / Chapter 4.5.1.1 --- TIN'S Derived Variable - Elevation --- p.105 / Chapter 4.5.1.2 --- TIN'S Derived Variable - Gradient --- p.107 / Chapter 4.5.1.3 --- TIN'S Derived Variable - Orientation --- p.109 / Chapter 4.5.1.4 --- TIN's Derived Variable - Dimensions (surface distance) of Landslides --- p.109 / Chapter 4.5.1.5 --- Micro-DEM and Profile --- p.109 / Chapter 4.5.1.6 --- Weighting Method Adopted in Calculating the Gradient and Orientation of Primary Depletion Scar --- p.110 / Chapter 4.5.2 --- Data Preprocessing --- p.110 / Chapter 4.6 --- Summary --- p.114 / Chapter CHAPTER V: --- STATISTICAL ANALYSIS OF LANDSLIDE DISTRIBUTION --- p.115 / Chapter 5.1 --- Sampling --- p.116 / Chapter 5.1.1 --- Sampling Frame --- p.116 / Chapter 5.1.1.1 --- Simple Random Point Sampling --- p.117 / Chapter 5.1.1.2 --- Stratified Random Point Sampling --- p.117 / Chapter 5.2 --- Comparison of the Two Study Areas --- p.119 / Chapter 5.3 --- Statistical Analyses of Landslip Variables --- p.123 / Chapter 5.3.1 --- Gradient (TIN) and Elevation --- p.124 / Chapter 5.3.2 --- "Aspect, Geological Materials, Gradient, Terrain Component, Erosion & Instability, and Vegetation" --- p.126 / Chapter 5.3.2.1 --- Aspect --- p.127 / Chapter 5.3.2.2 --- Geological Materials --- p.130 / Chapter 5.3.2.3 --- Gradient --- p.132 / Chapter 5.3.2.4 --- Terrain Component --- p.137 / Chapter 5.3.2.5 --- Erosion and Instability --- p.140 / Chapter 5.3.2.6 --- WWF Vegetation --- p.140 / Chapter 5.3.3 --- Result of the Partial Model --- p.145 / Chapter 5.4 --- Logistic Regression Model --- p.147 / Chapter 5.4.1 --- Landslide Probability Mapping --- p.154 / Chapter 5.4.2 --- Testing the Model Output --- p.157 / Chapter 5.5 --- Summary --- p.161 / Chapter CHAPTER VI: --- CONCLUSIONS --- p.162 / Chapter 6.1 --- Summary of Findings --- p.162 / Chapter 6.2 --- Limitations of the Study --- p.163 / Chapter 6.3 --- Recommendations for Further Studies --- p.166 / BIBLOGRAPHY --- p.167 / APPENDICES / "APPENDIX I Draft 3.3 slope failure/deposit field survey sheet (King, 1994a)" / "APPENDIX II Landslide/deposit field description sheet (King, 1994b)" / "APPENDIX III Hourly rainfall (mm) record at N05 in September 26-27，1993 (Source: Special Projects Division, Geotechnical Engineering Office, Civil Engineering Department)" / "APPENDIX IV Hourly rainfall (mm) record at R23 in September 1993 (Source: Hydrometeorology Section, Royal Observatory, Hong Kong,1993)" / "APPENDIX V Hourly rainfall (mm) record at R31 in September 1993 (Source: Hydrometeorology Section, Royal Observatory, Hong Kong,1993)"