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A comprehensive framework of TDR landslide monitoring and early warning substantiated by field examples
(2019-11-28)
Chung, Chih-Chung
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Lin, Chih-Ping
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土木工程學系
;
Department of Civil Engineering
Due to the climate change and hazardous geological environment in Taiwan, real-time landslide monitoring for safety of adjacent tribes or infrastructures is much conspicuous. Time domain reflectometry (TDR) is considered as valuable technology for continuously capturing dynamics and locations of shear deformations with high temporal and spatial coverages. In this study, a comprehensive framework was proposed by integrating up-to-date procedure of installation guide, data acquisition, sliding deformation identification, and early warning processing. The advantages of the proposed framework were then examined and substantiated via field cases. The first case is at a large colluvium slope in Lushan, central Taiwan. The colluvium is still active after heavy rainfall events, but limited evidence of sliding characteristic was collected previously by manual inclinometer logging. Therefore, the TDR framework was deployed and multiple landslide surfaces at great depths were timely observed. Movement of colluvium mass was thereby interpreted as a buckling fold. Additionally, creep occurred among the colluvium layer during the monsoon season because of strength weakening influenced by pore pressure fluctuations. Monitoring results of the second landslide case in Jufan, northern Taiwan, reported the dynamics of a thin sliding plane captured with TDR high temporal resolution. This unique behavior was further applied for devising of a novel early-warning strategy in terms of time-variation of TDR response, validating that the comprehensive framework of TDR landslide can effectively contribute to early warning.
Investigation of non-unique relationship between soil electrical conductivity and water content due to drying-wetting rate using TDR
(2019-03-26)
Chung, Chih-Chung
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Lin, Chih-Ping
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Yang, Shi-Hui
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Lin, Jhe-Yi
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Lin, Chun-Hung
The characterization of the relationship between volumetric soil water content (theta) and bulk electrical conductivity (EC) (or electrical resistivity) is of high interest in fields of engineering, fundamental petrophysical, hydrological model parameterization, and quantitative hydrogeophysical interpretations. Based on the relationship, for instance, the broad-area image using electrical resistivity tomography (ERT) can be transformed into theta tomograms as initial/boundary conditions of the slope stability analysis. However, the relationship is affected by the hysteresis, leading the inconsistency in drying-wetting circles. Therefore, this study focused on the factor of soil drying-wetting rate using the proposed time domain reflectometry (TDR) method and related sensors for such characterization. A modified pressure plate apparatus enhanced by TDR was first employed with a relatively low rate in which EC and theta were measured simultaneously, without evident non-unique relationship. A TDR penetrometer was then designed for acquiring the temporal variations of theta and EC in the field. On the basis of certain assumptions, observations showed an apparent dependency of the slope of the theta-EC rating curve on rates, but no hysteresis pattern. Finally, a laboratory controlled fast wetting drying cell was used to increase the response time, proving that both the hysteresis and slopes of the theta-EC rating curves were obviously affected by the soil drying-wetting rate, as a significant finding to the related topics.
Pad Characterization for CMOS Technology Using Time Domain Reflectometry
(2008)
Chiu, C. S.
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Chen, W. L.
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Liao, K. H.
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Chen, B. Y.
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Teng, Y. M.
The pad structure of CMOS technology is characterized by way of time domain reflectometry measurement. Using the on-wafer TDR measurement system, the capacitance of the pad in the CMOS process was extracted and estimated. Measured and Simulated TDR data are also presented in this study. The capacitance is estimated when the curve is fitted by mathematical tool. This method is simple to use, and furthermore the results agree with data extracted from vector network analyzer.
Improved TDR Method for Quality Control of Soil-Nailing Works
(2016-01-01)
Chung, Chih-Chung
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Lin, Chih-Ping
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Wang, Kai
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Lin, Chih-Sheng
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Ngui, Yin Jeh
Time domain reflectometry (TDR) has become an effective nondestructive testing method for soil-nailing inspection. Previous studies utilized a preinstalled, single-core, electric wire alongside the rebar within the soil nail. Measurements may be affected by possible grout defects and excessively overestimate the rebar length if the wire is coiled around the rebar. An improved TDR waveguide and a corresponding decoupled data reduction method (for both soil-nail length determination and grout condition inspection) are proposed herein. The feasibility and advantages of the new approach were experimentally verified with two types of TDR device. The proposed methodology makes it possible to use a portable, low-cost, and low-speed TDR device as a quick and economical tool for quality control of soil nailing.
Monitoring of Sediment Transport in a Reservoir using Time Domain Reflectometry
(2013-01-01)
Chung, Chih-Chung
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Lin, Chih-Ping
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Wu, Po-Lin
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Hsieh, Sheau-Ling
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Wu, Ching-Hsien
Due to geological weathering and climate change, soil erosion in watershed is becoming a serious problem in Taiwan. Large amount of sediment transports to reservoirs during typhoon events and affects the water quality. Density currents in reservoirs have high sediment concentration. The accumulated sediments have significantly reduced the reservoir capacity. Monitoring of sediment transport in a reservoir plays an important role in reservoir management. The existing techniques for suspended sediment concentration (SSC) monitoring, such as optical and acoustic methods, are sensitive to particle size or limited in measurement range. Furthermore, these techniques may not be cost effective for field monitoring due to the required maintenance and spatial coverage. A new technique based on time domain reflectometry (TDR) was recently introduced. It possesses several advantages including particle-size independence, low-cost transducers, durability, and cost-effective multiplexing. This study modified the TDR technique for better field applicability and demonstrated how it can be deployed as a full monitoring program for reservoir management through a case study in the Shihmen reservoir, Taiwan. Monitoring stations at upstream riverbank and outflow channels were installed with fixed protective structures to provide inflow and outflow sediment-discharge records. To capture the characteristics of density currents, multi-depth monitoring stations were designed and deployed on floats in the reservoir. Some of the data collected during Typhoon Fung-Wong are presented as an example to demonstrate the effectiveness and benefits of the monitoring station.
時域反射法於太陽能版檢測技術研發
(2011)
鐘志忠
;
Chung Chih-Chung
;
國立交通大學防災與水環境研究中心
目前世界各國已積極發展太陽光電發電以取代部分能源需求，然而相關太陽光電發電研究發展，多數以模組製程改善與提升模組發電效率為主要導向，較缺乏實務安裝與後續維護檢測與品管部分。本研究鑑於提升太陽光電產品應用週期與回饋產業發展需求，回顧現有相關太陽能版檢測方法，評估以時域反射(Time domain reflectometry, TDR)技術最具有可行性。因此本研究針對TDR於太陽能模組實體線路檢測相關限制，擬定提供TDR分析模式改良以及率定方法，並配合對應儀控軟體規劃與建置，藉以提升TDR技術於太陽能模組實體線路與材料品管檢測應用，包含量測準確度、量測效率、量測標準化，以及第一線工程人員使用者操作便利性。
New TDR waveguides and data reduction method for monitoring of stream and drainage stage
(2013-11-15)
Chung, Chih-Chung
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Lin, Chih-Ping
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Wu, I. -Ling
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Chen, Ping-Hung
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Tsay, Ting-Kuei
Less known in the field of hydrological measurements in civil engineering, time domain reflectometry (TDR) has been developed as a new solution to some of the more difficult level measurement problems. This study applied TDR methodology to provide two new designs for a water level sensing waveguide that can be applied in difficult field conditions such as in an underpass, tunnel, culvert, or sewer, etc. Two types of water level sensing waveguides are presented, including a rigid assembled coaxial pipe and a flexible adhered parallel wire. The corresponding data reduction procedure is also proposed to account for uncertainty of travel time analysis and calibrate the velocity of pulse propagation along the waveguides. The satisfactory performance of both the proposed TDR waveguides and data reduction method was experimentally validated. A field case study further demonstrated the feasibility of the TDR technique for water level measurements under typical urban drainage conditions. (C) 2013 Elsevier B.V. All rights reserved.
High concentration suspended sediment measurements using time domain reflectometry
(2011-04-20)
Chung, Chih-Chung
;
Lin, Chih-Ping
;
土木工程學系
;
防災與水環境研究中心
;
Department of Civil Engineering
The existing methods of suspended sediment concentration (SSC) monitoring provide a measurement accuracy significantly influenced by the particle size of suspended sediments, function only under limited measurement range and are not cost effective for field maintenance as well as wide spatial coverage. The paper introduces an innovative SSC monitoring methodology based upon time domain reflectometry (TDR), especially emphasizing on optimum TDR measurement accuracy investigated theoretically and experimentally. Pertinent probe design, probe calibration, as well as data reduction procedures were proposed. Ultimately, the approach can achieve the measurement accuracy to adapt the derived hardware resolution and beyond. In addition, the performance evaluation was carried out considering possible influence factors including water salinity, sediment types and particle sizes, and leading cable lengths. TDR SSC measurements indicate insensitive to sediment particle sizes. After proper calibration, the measurements are also insensitive to water electrical conductivity and not affected by leading cable resistances. There are further advantages of the TDR method including high measurement range from 2 to at least 300 g L(-1), easy calibration, robustness, maintainability, and cost-effective multiplexing. (C) 2011 Elsevier B.V. All rights reserved.

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