Most medium- to large-scale landslide disasters in Taiwan are due to dip-slope failures in sandstone and shale formations in the foothill region of western and northern Taiwan. The Tsao-Ling landslide, the Juo-Feng-Err-Shan landslide, the the Lincoln Villa landslide, the Pa-Du landslide, the Shi-Tz landslide, and the Mt Tiger landslide, have been the most noted dip-slope failures in Taiwan. Each of the landslides caused loss of tenth of human lives or interruption of transportation. The great destruction and loss of 1909 human lives caused by the Vajont Slide on 9th October 1963, in Longarone of Italy, has been the most disastrous dip-slope failure in the world.
Exposure (or daylighting) of the potential slip-plane is often but not always a necessary condition for the occurrence of dip-slope failures. A failure surface can be hybrid, which is originally made up of pre-existing natural weak plane and intact rock material before being sheared through.
For many large-scale dip-slope failures, their potential slip-plane had opened up or slipped before failure. It is therefore that only residual shear strength is used for most dip-slope stability analysis, and that residual cohesion is taken to be zero.
The Shi-Tz dip-slope failure has been reanalyzed to illustrate that the water pressure in the vertical open joint and on the potential slip-plane is very sensitive to the stability of a dip-slope.
According to the investigations performed by Soil and Water Conservation Bureau, Council of Agriculture, Executive Yuan in 2002, there totally 1,420 streams were categorized as potentially hazardous stream of debris-flow. The frequency of debris-flow occurrence increases with large-scale in the restoration area of central part of Taiwan after chichi earthquake in 1999. Consequently, debris-flow hazards and the associated prevention countermeasures have now become a major concern in disastrous remedies. However, due to the distinct characteristics of debris-flow, which is significantly different from the mountain flooding, the planning and design of prevention works against debris-flow need to be carried out with great care.
This paper presents the design of prevention countermeasures such as consolidation-type sabo dam, open-type sabo dam and debris retention basin on the basis of the factors and conditions controlling the occurrence of debris-flow and the principles of overall planning of debris-flow prevention. In addition, the main causes of the damage of structures and facilities used to prevent debris-flow hazards in the past were also analyzed and discussed. It is of great advantage to the engineers to take the case histories and lessons depicted as a reference in their planning and design works without encountering difficulties.
The mudstone stratum in Taiwan is mainly exposed in the southwestern foothills, the southern area of Coastal Range at eastern Taiwan, and the Hengchun peninsula. Among them, the most widespread area of exposed mudstone is the southwestern foothill with about 1,400 square kilometers. This mudstone formation is deposited from the late Tertiary to the early Quaternary. Due to the shorter digenetic period, it has some unfavorable properties such as lower strength, swelling and slaking behaviors, lower resistance of weathering, etc. Recently, several important transportation constructions, e.g. the southern part of the 2nd national highway and the east-west high speed highway, were built through these areas and caused extensive excavations of the mudstone slopes. Serious geologic hazards, such as collapses of retaining walls, failures and erosion of slope, mudflow, exposed vegetation slope, were frequently found after a torrential rain. Hence, how to establish a suitable technical treatment to protect the mudstone slopes becomes an important issue in Taiwan. This paper presents an evaluation results of the protecting methods in use for mudstone slopes and discusses the mechanism of some failure slopes. It may be a helpful reference for the technical treatments of mudstone slope stabilization in the future.
The stability analysis of waste slopes is very important in landfill plan and design. This paper introduces some subjects for waste slopes including failure types, strength properties, methods of stability analysis, and special considerations. Additionally, in order to show how to choose related parameters in stability analysis, two cases of failure landfill sites are analyzed. Some influence factors on waste-landfills stability are discussed as well. It is hoped that this content will aid the stability analysis of waste slope during all stages of design, operation and closure of landfill sites.
Conventional slope engineering is made up in form of concrete structures in which the quite smooth surface will result in the difficult living condition for other live form. To avoid the impact of traditional concrete slope engineering on the environmental care, the ecological engineering method presents promising meaning.
To achieve the multiple goals of the ecological conservation, safety precaution and recreation center, five fundamental principles, such as small openings of surface, lowing the higher dam, decreasing the angle of slope, adopting natural material and permeable interface, shall be taken into account in planning and design to raise the additional value and economic benefits. Also, this paper describes the ecological engineering method in the treatments of debris flow, the source of slumps and the slope stability in lateritic terrace and mud stone.
Taiwan is located at the convergent boundary of Euroasian plate and the Philippine Sea plate. 70% of Taiwan area is mountainous. Various hazards are mainly caused by steep topography, complicated folding and faulting geology, heavy rainfalls and inappropriate development of slope.
The feasibility of slope protection measures should consider inherent factors of site, especially geological factors and surrounding environments. It is expected that the geological investigation principles and methods described in this paper would be helpful for engineers in gaining the ability of protection method selection, design, construction and maintenance.
Based on the failed and not failed slope cases collected from the public roads or the residential communities, this study will propose a method to select adequate slope stabilization method for specific slope in terms of failure probabilities. This method is established by integrating the canonical discriminant analysis, statistic software SPSS, and slope cases from the field. The influencing factors on the stability of slope are quantified using an evaluation table and substituted to the SPSS analysis. Totally, six factors with significant discriminating ability were identified, namely the structure of bedrock, surface drainage condition, slope cutting, toe excavation, weathering of slope surface, and slope maintenance. These factors are used to establish the discriminant functions for various slope stabilization methods. Using these discriminant functions, the failure probability of a slope protected by certain slope stabilization method can be estimated. In addition, the optimum slope stabilization method can also be selected based on the position of calculated result in the discriminant coordinates. This method can provide a useful means to guide the engineers chossing a suitable slope stabilization method according to the geological condition, drainage condition, and human activity factor of a particular slope.
There are lots of potential hazardous landslide areas in Taiwan due to mountainous terrain and high-density land-use. Such situation is causing serious problem of unstable construction buildings that are built beside land-slope region. Therefore, landslide disasters claim hundreds of lives and cause millions of dollars of property damage throughout island-wide in each year. EPS is the abbreviation of Expandable Polystyrene. A block of EPS is made from the particle of Polystyrene with expanded and melted process in a specific mold by adding steam gas. The EPS light-weight construction method refers to employ large EPS blocks with unit weight between 12kgf/m3 and 30 kgf/m3 in civil engineering, architecture engineering, disaster prevention and garden engineering. This paper introd relative information of EPS and describes the investigation of EPS production and practice application projects of slop stability. The purpose of this paper’s presentation is trying to motivate more and more people involved to the research and development (R&D) domain of EPS construction method in Taiwan.
Anchors are often used as part of the stabilization measure for cut slopes which are high or natural slopes which have high potential of sliding. In the past, this method is used and recognized widely by Taiwan engineering fields. However, due to lack of right understanding, the design and quality of popularly used ground anchors are not controlled effectively. Since the Lincon Community disaster that led to 28 persons died occurred in 1997, many people and some engineers have claimed against using anchors to stabilize slopes. To counter balance the view points, this paper discusses the suitability of anchors, and the key problems encountered during design and construction stages. In addition, some suggestions from system and management aspects are given to correct the wrong concepts and prevent ground anchor failure. And, wish engineers could have open mind and careful attitude to understand the suitability of ground anchor. Utilizing the strong point of ground anchor and well-controlled design and quality to prevent the failure. Don’t give up this kind of well-developed method. On the contrary, engineers should look for better solution to improve ground anchor more aggressively. Then, to promote the technology in slope stability and to acquire appropriate thoughts in avoiding slope failure and calamity.