Analysis on Subsidence Monitoring and Influence Factors at Intersection of Expressway 78 and High Speed Rail of Taiwan

• Main Authors: HUANG,I-NING, 黃奕寧
• Other Authors: Muhsiung Chang
• Format: Others
• Language: zh-TW
• Published: 2019
• Online Access: http://ndltd.ncl.edu.tw/handle/93ux5x

碩士 === 國立雲林科技大學 === 營建工程系 === 107 === Yunlin County is one of the major agriculture regions in Taiwan. Due to shortages in rainfall and water storage, however, agriculture activities in the county relay upon a significant amount of groundwater. As a result of prolonged groundwater extraction, the ground subsidence thus becomes a serious problem in Yunlin. According to Water Resources Agency (WRA) of Taiwan, the most severe subsiding areas of Yunlin are in the townships of Tuku, Huwei, Yuanchang, Baochung, Erhlung and Luenbai. The area of current study is located at the intersection of Taiwan High Speed Rail (THSR) and Expressway 78 (Expwy 78), in the vicinity of Tuku Junior High School. In view of the two major transportation arteries crossing the serious subsiding area, the safety of THSR and Expwy 78 has become a great concern to the general public, signifying the importance of ground subsidence to this area. A five-year on-site monitoring data is collected and analyzed to better understand the behavior and causes of ground subsidence in the study area. By comparing the monitoring data, we found the groundwater tables generally fluctuate in response to the rainfall, namely, groundwater level rises in wet seasons and lowers in dry seasons, indicating the rainfall would be beneficial to the groundwater storage of the site. During the wet seasons, however, we noticed the groundwater levels may sometimes be lowered, which could be attributed to the additional groundwater pumping in planting periods when the rainfall is still insufficient. The comparison of soil layer compressions and groundwater fluctuations is performed based on the monitoring data from STA-1 and STA-9. Monitoring Station STA-1 is located at the junction of THSR and Expwy 78, and the ground subsidence at this station will be affected by the structural loading of the transportation structures. Monitoring Station STA-9 is away from the intersection and the ground subsidence at this location would hence have little influence due to the structural loading of THSR and Expwy 78. Results of monitoring indicate the fluctuation patterns of various groundwater levels of the site are similar. The relations between soil compression and groundwater fluctuation for STA-1 and STA-9 are also about the same. The groundwater fluctuation has an intimate relation with the soil compression and would be the key factor on the ground subsidence of the site. In addition, the long-term declining in deeper groundwater levels appears to be more obvious than that in the shallower groundwater levels, implying the compressibility of deeper soil layers would be greater than that of the shallow soil layers.