圖書典藏及影音數位平台

為有效監測地層下陷行為，及時掌握地層下陷之發生趨勢，依據地下水保育管理暨地層下陷防治第2期計畫（104～109年度）持續辦理臺北、嘉義、臺南及屏東地區地層下陷監測，並維護相關監測設備（包含5站GPS固定式監測站、20口地層下陷監測井及1支深層水準樁），同時蒐集相關監測資料進行分析探討，釐清下陷發生機制，據以研擬因應對策，有效達成地層下陷之防治目標。

The objectives of project are to monitor the land subsidence and to explore the subsidence mechanisms in Taipei, Chiayi, Tainan and Pingtung, Taiwan. Consequently, these results will provide precaution for the potential areas of land subsidence and develop the conceptual strategy for the mitigation of serious land subsidence. This project contains following tasks including: 915 kilometers leveling survey in subsidence area, constructed 1 continuous GPS stations and 2 land subsidence monitoring well, and maintained the existed GPS stations, monitoring wells and deep benchmarks in the area, and integrated analysis of monitoring data obtained from the land subsidence areas. The main results are summarized as follows: 1. The results of leveling survey The areas of leveling survey include Taipei(120 km), Chiayi(360 km), Tainan(250 km) and Pingtung(185 km), total length of surveyed routes is about 915 km. The results of the leveling survey are as follows: (1) In Taipei City, 2019, the maximum subsidence rate is about 1.0 cm/yr and the obviously subsiding area is about 0.0 km2. (2) In Chiayi County, 2019, the maximum subsidence rate is about 3.1 cm/yr and the obviously subsiding area is about 0.2 km2. (3) In Tainan City, 2019, the maximum subsidence rate is about 3.3 cm/yr and the obviously subsiding area is about 0.9 km2. (4) In 2019, the maximum subsidence rate in Pingtung County is about 3.1 cm/yr and the obviously subsiding area is about 0.9 km2. The subsidence rate and subsidence area obviously decreased. 2. Maintenance and measurement of the land subsidence monitoring wells, continuous GPS stations and deep benchmarks (1) The maintenance of 21 land subsidence monitoring wells, 6 continuous GPS stations and 1 deep benchmarks have been accomplished. All of the survey stations and instruments are with good status of all systems facilities. 3. Construction of 2 land subsidence monitoring wells and a continuous GPS station (1) The New land subsidence monitoring well has been built up in Budai Elementary School and Jinhu Elementary School on August 2019. All instruments were installed completely and with good status of all systems facilities. And the accuracy of the uncertainty analysis of monitoring well were ±0.080 and ±0.060 cm, respectively. (2) The new continuous GPS stations have been built up in Jinhu Elementary School in Tainan City on May 2019. All instruments were installed completely and with good status of all systems facilities and internet. Data acquisition was more than 40000 per day, with cycle slip index between 1 and 2, and MP1 and MP2 values between 0.2 and 0.4. 4. Analysis of the integrated monitoring data in land subsidence area (1) Taipei area：No obviously subsiding area in Taipei. (2) Chiayi area：Liujiao, Xingang and coastal areas were the main subsiding area in Chiayi and the subsidence rates were between 2~3cm per year. The main compression depth in coastal area was deeper than 127 meter but shallow depth at Liujiao and Xingang area. (3) Tainan area：The main subsiding District in Tainan City were Beimen and Xuejia. The subsidence in Beimen was seriously than Xuejia, the subsidence rates was about 3cm per year and 2cm per year, respectively. (4) Pingtung area：The main subsiding area in Pingtung were Linbian, Jiadong and Fangliao. The subsidence rates were between 2~3cm per year in the area which attributed to the rise of rainfall and groundwater level in the dry season in 2019. (5) There are obvious subsidence situations occurred around the Taiwan high speed rail in Chiayi County. In the future, this area should be focused on monitoring continuously for the safety issue.