Due to high seismicity and high annual rainfall, there are numerous landslides triggered in Taiwan every year, which in turn lead to rapid change in landform. Pre-disaster and post-disaster high-resolution and high-precision digital terrain models are essential for hazard mitigation and monitoring. The Unmanned Aircraft System (UAS) LiDAR technology can exactly provide such data. In this research, relevant technologies are introduced and integrated for use in Taiwan. Based on the capacity of multiple echoes, the system acquires dense point clouds with effective ground points, which allows the filtering of vegetation and non-ground points in densely vegetated area. The digital elevation models (DEMs) are the end-products obtained from the system. Compared with the field survey data, the overall elevation error of the UAS LiDAR geoinformatical data is less than 5 cm. This study illustrates that the system can efficiently meet the geoinformatical data demand for practical applications.
The rock mass excavation and construction industries rely heavily on accurate geospatial data to control the position, location, alignment and orientation of the planned excavations. Recent advancements in the measurement survey technique, through the use of LiDAR laser scanning, can now provide engineering industry with three-dimensional (3D) data in unprecedented details via geo-referenced point clouds. Furthermore, hand-held scanner equipment can now provide fully mobile automated mapping solutions by utilizing Simultaneous Localization and Mapping (SLAM), which is independent of satellite positioning. This paper evaluates the surveying capability of the mobile hand-held scanners and presents the preliminary geological analysis results derived from the automated mapping for the sea cave of Lungdung. This study illustrates that hand-held automated mapping solutions have the potential to provide quicker data collection and processing time, as well as the required surveying accuracy when the subject site is a closed underground space.
Monitoring is a part of a modern infrastructure project that provides information on construction safety and structural maintenance and management during the operation period after the completion of the structure. Using the abandoned old Hoping Tunnel and its neighboring slope as an example, this paper presents the Digital Surface Models (DSM) for the slope using the images taken by an Unmanned Aerial Vehicle (UAV), as well as the tunnel surface models obtained using the close-range photogrammetry and the ground-based Light Detection And Ranging (LiDAR). Various DSMs and tunnel surface models obtained at different periods reveal the monitored collapse of a nearby slope, propagation of lining cracks and falling down of rock wedges along the tunnel vault. Furthermore, the DSMs and tunnel surface models are fitted and integrated into a digital reality environment for an overall visual display of the monitoring results. The historical evolution of the physical scenes can be observed with precise spatial positions and coloring, and the changes in the tunnel and slope can be visually and continuously studied. This case study illustrates that the exquisite surveying and mapping combined with digital reality can be the next-generation geotechnical monitoring technique.
The performance of an offshore foundation is directly related to the engineering properties of the supporting seabed soil. Thus, geotechnical investigation of the seabed at the project sites is essential to obtain the stratigraphy and characteristics of soil for the foundation design of offshore wind turbines. Because of the uniqueness of the offshore site and the characteristics of the wind turbine operation and the supporting structures, procedure and criteria for offshore geotechnical investigation are somewhat different from those for the onshore one. In this paper, requirements and recommendations for geotechnical investigation of offshore wind farms from several representative international design guidelines for wind turbines were reviewed. The review includes discussions on the objectives, methodologies, extent and range of the investigation, number of borings, methods and amount of sampling, requirements for laboratory tests and special concerns about foundations subjected to cyclic loads such as wind, wave, flow and earthquake. A brief summary of the geotechnical investigation for two offshore wind farms in Europe is also presented. Based on the review, localized suggestions for the geotechnical investigation of offshore wind farms to meet the local needs of Taiwan are proposed. It is hoped that these suggestions will serve as the references for planning and implementation of offshore site investigation by the engineering practitioners in Taiwan.
In order to realize the localization of domestic offshore wind power industry in Taiwan, a lot of local construction companies and vendors have begun making a large amount of investments in introducing new technology and equipment. When an offshore windfarm is developed, extensive and detailed site investigation is required to provide the reference information for determining the windfarm siting, the arrangement and distribution of wind turbines, the types and design methodology of the turbine foundation.
The information gained from offshore windfarm site investigation includes sea states, current changes, littoral drift conditions, seabed topography and formation, sub-bottom profile, distribution of buried objects, and geological substructure and characteristics under the seabed. The investigation is often divided into four parts: sea state and hydrological survey, geophysical survey, geotechnical investigation and laboratory testing, and ROV exploration.
The purpose of this paper is to shed light on various investigation works required for offshore windfarm site
investigation, and to explore the suitability of different kinds of adopted working platforms, devices and equipment, and
laboratory test methodology. This paper can serve as a reference for offshore engineering planning, as well as the
organization and methods suitable for offshore site investigation.
Located at the boundary between the Luzon arc and the Eurasia plate, Green Island was once an active volcanic island during the eruption period of about 1.54-2.0 Ma.. Different eruption centers cover volcanic breccia and tuff breccia from different geologic periods. Due to arc-continent collision, magma activity had ceased and formed different types of faults on the Green Island. According to the geochemical analysis, the residual heat of the volcanic magma has been brought to the surface through the faults by seawater circulation. It is also speculated that the residual heat had been previously affected by the magma activity. The preliminary survey report (ITRI, 2010) pointed out that Green Island has the potential for geothermal power development. Taipower is looking forward to transforming Green Island's electricity supply into renewable energy. In this research project, exploration and drilling are conducted to evaluate the development possibility and determine the production capacity.
In this research project, high-density magnetotellurics (MT), electrical resistivity tomography(ERT), geochemical investigation and geological data are employed to evaluate the possible geothermal structures and the potentials for renewable energy in the Green Island. According to the three-dimensional electrical structure from the MT and ERT surveys, the geothermal source comes from the deep volcanic heating and the heat can be transported to the shallow layer through the fault systems on the southern side of Green Island. Since there is no obvious volcanic eruption on the surface of Green Island, the geological conceptual model of the geothermal system might be different from that for general volcanic type. More test wells and log data should be collected in the future to validate and revise the geological conceptual model.
Soil pumping phenomenon is a common issue in railway structures. Present mud pumping detection method has to be performed visually during non-operating time. However, spots with soil pumping can be easily missed out using this approach. Also, detection can be difficult and slow to be carried out during rainy season. According to previous studies, compared with regular mud, the mud from soil pumping is quasi-liquefied, dense, and under excess pore-water pressure. Ground penetrating radar, GPR, is a non-destructive geophysical method that uses radar pulses to detect different ground materials. A GPR transmitter emits electromagnetic waves into the ground. When the waves encounter a buried object or a boundary between materials having different permittivity, they may be reflected, refracted or scattered back to the ground surface. In this paper, a new soil pumping detection method based on basic GPR signals is proposed to identify the interface between mud and ballasts in railway structures.
The borehole exploration techniques have been adopted worldwide since 1970s, and have been gradually developing in Taiwan over the last decade. These techniques were applied in various public construction projects, such as landslide mitigation, environmental impact assessment for tunnel and reservoir construction, and safety assessment for nuclear power plant. The relevant applications were also carried out for thermal and water resource exploration, as well as the identification of sensitive area induced by active fault and landslide. The regulations for foundation investigation in Taiwan still stipulate the use of traditional method of borehole drilling, and the engineering assessment and design would solely consider information obtained from such method. Since the coring data is significantly affected by the quality of drilling, deviation from the reality due to poor coring data would lead to wrong decisions for both engineering assessment and design. In addition, the geotechnical investigation is highly related to the borehole condition and drilling method. Pre-planning with clear communication with the drillers is needed prior to the investigation, but in practical application such task is rarely carried out. Therefore, this study aims to discuss the importance of borehole investigation and share the author’s experience with the professionals who are involved in the foundation design and construction projects in Taiwan. The innovative borehole exploration technologies are deemed to be useful and can be incorporated into existing field investigation approach, which in turn can help run the construction projects smoothly
Taipei city government constructed the intermediate soil liquefaction potential map and implemented the supplementary investigation on previous geological drill holes in 2017. Piezocone penetration tests, CPTu, were performed as a part of the supplementary investigation. By cross-referencing the drilling data with the CPTu data, it is found that the precise, fast and nearly continuous results from CPTu are able to recognize the extremely soft soil layer in Taipei city. In addition, the CPTu is also able to reveal the changes in soil properties among different soil layers. Moreover, the results of liquefaction hazard analysis suggest that CPTu data is suitable for identifying soil liquefaction potential.