|題名||105年度臺北、嘉義、高雄及屏東地區地層下陷監測及分析Monitoring and Analyzing Subsidence of Taipei,Chiayi, Kaohsiung, and Pingtung Area in 2016
|英文摘要||The working items of land subsidence monitoring project Taipei, Chiayi, Kaohsiung and Pingtung areas including the leveling survey, precise GPS positioning, the measurement of land subsidence monitoring wells, development of GPS continuous stations and the purchase of GPS instruments have been conducted and accomplished. The comprehensive results are as follows.
(1)The results of leveling survey
The areas of leveling survey include Taipei (270km), Chiayi (360km), Kaohsiung (250km) and Pingtung (430km). The total length of surveyed routes is about 1,170 km. The results of the leveling survey are as follows:
(a)There is no significant land subsidence situation occurred in Taipei City in recent years. The magnitudes of subsidence for the survey points are distributed between plus or minus one centimeter per year. The maximum subsidence rate is 0.5 cm/yr, and the obvious subsidence area is zero km2.
(b)In Chiayi County, the maximum subsidence rate is about 2.6 cm/yr in Budai Township and the continuously subsiding area (the area of subsidence rate over 3 cm/yr) is about zero km2. Dongshi and Budai Townships are the mainly subsidence areas in Chiayi County on 2016.
(c)In Kaohsiung City, the maximum subsidence rate is about 1.6 cm/yr in Mituo District and the continuously subsiding area is about zero km2. And the magnitudes of subsidence for most of survey points are distributed between plus or minus one centimeter per year.
(d)In Pingtung County, the maximum subsidence rate is about 3.1 cm/yr in Jiadong Township and the continuously subsiding area is about 0.1 km2.
(2)Maintenance and measurement of the existed land subsidence monitoring wells and GPS continuous stations
(a)At present, there are 19 multilevel compression monitoring wells and 3 GPS continuous stations distributed in Yilan, Taoyuan, Chiayi, Tainan, Kaohsiung and Pingtung areas. All monitoring instruments are with good status of all systems facilities.
(b)According to the data quality indexes for the GPS stations, the received GPS signals from the GPS receiver are quite stable and normal.
(3)Development of GPS continuous stations and the purchase of GPS instruments
(a)New GPS continuous stations were built up smoothly in Linbian Junior High School and Dingliao Inspection Office in Pingtung County on 29 April 2016. All instruments were installed completely and with good status of all systems facilities and internet.
(4)Analysis by the integration of the monitoring data in land subsidence area
(a)For Zhuangwei Township in Yilan County, the situation of subsidence is still happened slightly. The average of long-term and short-term rate of compression are all smaller than 1 cm/yr, and the range for the compression is not obvious.
(b)In Taoyuan County, according to the results from the only one monitoring well, the average of long-term and short-term rate of compression are all smaller than 1 cm per year. And there is no obvious relationship between compression situation and the change of groundwater.
(c)In recent years the subsidence tendency was gradually mitigating in Chiayi County, however, the subsidence tendency was slightly increasing in 2015 which attributed to the fall of rainfall and groundwater level in the dry season.
(d)Comparing the results from leveling, monitoring well and groundwater, two townships, Liujiao snd Xingang, nearby Taiwan High Speed Rail in the Chiayi present the range for the compression is from underground 49 to 126 m. The maximum magnitude of groundwater drawdown in the second aquifer is measured in this area. The change of ground water and amount of compression for the shallow layer need to be focused in the future.
(e)In Tainan area, most of monitoring wells show unobvious land subsidence situation except two monitoring wells located at Xiaying elementary school and Shiuejia junior high school areas. And the subsidence situations present the long-term and short-term compression rate are larger than 0.6 cm per year. Therefore, the taking notice of compression situations in these areas are needed in the future.
(f)According to the leveling survey from 2006 to 2016, the maximum accumulated settlement is about 6.0 cm in Gangshan, Alian, Cieding and Sanmin Districts. Owing to the THSR passes through Gangshan and Alian areas, these areas should be focused on monitoring continuously for the safety issue in the future.
(g)In Kaohsiung area, the average of long-term and short-term rate of compression are all smaller than 1 cm per year; hence, there is no significant subsidence happened in this area.
(h)The subsidence tendency in Pingtung County was more mitigating than last year which attributed to the rise of rainfall and groundwater level in the dry season in 2016.