Browsing by Author "Ho, Yen-Te"

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Characterization of reservoir sediment under water with differential pressure-sensored flat dilatometer and piezo-penetrometer
(2013-08-01)
Lee, Jui-Ting
;
Wang, Chien-Chih
;
Ho, Yen-Te
;
Huang, An-Bin
;
土木工程學系
The unusually strong typhoons and heavy rainfalls occurred recently in Taiwan have caused major landslides in many reservoir catch basins. The debris from these landslides eventually settled in the reservoir and turned into mud. From soil mechanics point of view, the mud immediately in front of the dam where the reservoir is usually the deepest is a very young, normally consolidated or under-consolidated fine-grained soil. The engineering properties of the reservoir mud are important parameters in the planning and design of schemes to remove the mud. Yet, our knowledge in this regard is very limited. For some of the major reservoirs in Taiwan, the mud is often under more than 40 m of water. How to conduct effective geotechnical site characterization under these circumstances is a challenge. The authors developed techniques to incorporate differential pressure measurements in flat dilatometer (Delta DMT) and piezo-penetrometer (Delta Pu) tests to facilitate in situ measurements under water in a reservoir. A series of field Delta DMT and Delta Pu tests along with representative soil sampling were conducted at Tsengwen Reservoir in southern Taiwan. The paper describes the techniques of Delta DMT and Delta Pu tests, interpretation of available test data to obtain the engineering properties of the reservoir mud, and discusses implications in the future site characterization of reservoir mud.
Development of a chirped/differential optical fiber Bragg grating pressure sensor
(2008-04-01)
Ho, Yen-Te
;
Huang, An-Bin
;
Lee, Jui-ting
;
土木工程學系
;
Department of Civil Engineering
With its unique capabilities, the optical fiber Bragg grating has been used as a key component in the development of many sensors. Incorporating the theory of thin plates, the authors have developed an FBG-based pressure sensor by strategically attaching FBGs on the surface of a thin circular plate. The flexural strain in the circular plate induced by pressure applied to the circular plate is sensed by either a single FBG placed radially crossing a neutral point, or two FBGs placed respectively in zones where the strains are of opposite signs. When one FBG is used (i.e., the chirped FBG design), the applied pressure relates to the change in the chirped bandwidth of the FBG reflected waveform. When two FBGs are used (i.e., the differential FBG design), the pressure experienced by the circular plate is correlated to the difference in central wavelength from the two FBGs. In either case the sensing mechanism is immune to temperature fluctuation. The same configuration can potentially be applied for other purposes such as a load cell or displacement transducer. This paper describes the design principles of the FBG pressure sensor and demonstrates its capabilities through laboratory calibrations over a wide range of temperatures.
Fiber bragg grating sensored segmented deflectometer for ground displacement monitoring
(2007-03-29)
Huang, An-Bin
;
Ho, Yen-Te
The invention provides a monitoring device mainly for sensing ground displacement, including the fiber Bragg grating sensored deflectometer and the signal interrogator/computer system. The device uses a segmented design that consists of a flexible tube (referred to as the flexible segment) and two rigid segments and thus referred to as the FBG segmented deflectometer (FBG-SD). For field installation, multiple FBG-SD units are connected together to form a string as it is inserted into a grouted-in-place inclinometer casing. The distortion of the inclinometer casing induced by ground movement causes relative rotation of the inserted FBG-SD. All of the FBG-SD units are connected to an FBG interrogator/computer system situated on ground surface. The FBG signals are recorded and analyzed by the interrogator/computer system.
Stability monitoring of rainfall-induced deep landslides through pore pressure profile measurements
(2012-08-01)
Huang, An-Bin
;
Lee, Jui-Ting
;
Ho, Yen-Te
;
Chiu, Yun-Fang
;
Cheng, Shyr-Yuan
It has long been recognized that field hydrological and geomechanical properties/conditions are the key elements controlling the stability of a slope under the influence of rainfall. Warning systems based on rainfall or ground displacement measurements are popular methods currently being used to minimize the hazards of landslides. When field hydrological monitoring is used, it usually involves a limited number of sensors for either positive or negative pore-water pressure measurements. The available numerical schemes that couple pore-water pressure with a geomechanical analysis are the most suitable for shallow slope failures. Due to the variable and transient nature of the hydrological conditions in earth slopes, field measurements that reflect the pore-water pressure profile on a realtime basis would be highly desirable. Thus, the authors have developed a piezometer system that is based on optical fiber Bragg grating (FBG) pressure sensors. With this system, an array of nine sensors was installed in a single, 60-m-deep borehole to monitor the pore-water pressure profile in a highway slope in Southern Taiwan. This paper describes the details of the FBG sensor array installation in the field and the data obtained throughout three typhoons from 2008 to 2010. The results demonstrate that the field readings can be readily incorporated into the existing mechanics-based analytical framework and can predict the potential of an upcoming slope failure. (C) 2012 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.