以多元測地技術探討光電場建置與地下工程對聚落地表變形之影響

Analysis of Settlement Surface Deformation Induced by Photovoltaic Farm Construction and Underground Engineering Using Multi-Source Geodetic Techniques

不當的地下潛鑽工程常是造成地層下陷的其中一個原因，然而嘉義縣義竹鄉北華村自民國112年3月起，在聚落內道路與建物陸續出現的裂縫與傾斜，以及部分受損嚴重的結構物，卻暗示複雜的地表變形成因與機制。為釐清此成因，本研究整合透地雷達、RTK-GNSS測量、連續傾斜計及干涉式合成孔徑雷達等多元測地資料，分析不同時期人為活動對地盤穩定之影響。在第一期聚落周邊光電場與聚落內潛鑽的施工中（112年1月至3月），Sentinel-1A升軌InSAR影像（111年12月至112年4月）之視衛星方向（LOS）速度場顯示，光電場區的變形梯度最大，LOS速度達-9.5 cm/yr，較場區周邊高出約-2 cm/yr。然而，透地雷達顯示地下潛鑽路段無外擴掏空現象，因此推測聚落地表出現拉張裂縫與傾斜變形之破壞成因，可能來自於光電場淺層抽水所造成之地層壓密。在第二期光電場之建置期間（112年11月至113年1月），為驗證施工對地盤穩定之影響，本研究結合InSAR以及7個RTK-GNSS測點與1部連續傾斜計的資料來進行分析，RTK-GNSS結果顯示光電場中心累積下陷量約6 cm，邊緣則下陷約3至5 cm，傾斜計在光電場施工前（112年5月至12月），向南累積傾度約90”，於施工抽水後兩週內，增幅約21.6”。InSAR結果（112年11月至113年2月）顯示光電場範圍LOS速度達-8 cm/yr，較周圍高約-2 cm/yr，下陷中心與光電場施工區一致，證實光電場施工期間發生顯著淺層壓密。綜合兩期成果可知，光電場抽水造成淺層含水層孔壓驟降與地層壓密，潛鑽工程引發近場解壓與剪切破壞，兩者在時間與空間上產生疊加效應，最終導致聚落結構物裂損與傾斜。本研究建議未來於軟弱地層推動再生能源設施時，應同步考量地盤穩定性評估、抽水控制與即時監測系統之建置，以確保綠能開發與聚落安全能並行。

Improper underground horizontal directional drilling (HDD) is often one of the causes of land subsidence. However, since March 2023, cracks and tilting have appeared in roads and buildings within Beihua Village, Yizhu Township, Chiayi County. Some structures have suffered severe damage, indicating that the surface deformation may involve more complex mechanisms. To clarify the causes, this study integrates multiple geodetic datasets, including ground-penetrating radar (GPR), RTK-GNSS surveys, continuous tiltmeters, and interferometric synthetic aperture radar (InSAR), to analyze the influence of anthropogenic activities on ground stability at different periods.
During the first phase of solar farm and HDD construction around the settlement (January–March 2023), Sentinel-1A ascending-track InSAR (December 2022–April 2023) revealed that the deformation gradient was greatest within the solar farm, with line-of-sight (LOS) velocities reaching -9.5 cm/yr, about -2 cm/yr greater than the surrounding area. GPR profiles showed no evidence of subsurface voids along the HDD route, suggesting that tensile cracks and surface tilting in the settlement were likely caused by shallow pumping-induced compaction beneath the solar farm.
During the second construction phase of the solar farm (November 2023–January 2024), InSAR, seven RTK-GNSS stations, and one continuous tiltmeter were used to evaluate the effects of construction on ground stability. The RTK-GNSS data indicated cumulative subsidence of approximately 6 cm at the center of the solar farm and 3–5 cm along its margins. The tiltmeter recorded a cumulative southward tilt of about 90”from May to December 2023, which increased by 21.6”within two weeks after pumping began. InSAR results (November 2023–February 2024) showed LOS velocities of up to -8 cm/yr within the solar farm, about -2 cm/yr higher than nearby areas with the maximum subsidence coinciding with the construction zone, confirming significant shallow compaction during the construction period.
Synthesizing results from both phases, the study concludes that pumping at the solar farm induced a rapid drop in pore pressure and shallow compaction, while HDD activities triggered local stress release and shear failure. The temporal and spatial superposition of these effects ultimately led to cracking and tilting of settlement structures. This study recommends that future renewable energy developments in soft-sediment areas should incorporate ground-stability assessments, pumping control, and real-time monitoring systems to ensure the coexistence of sustainable green energy development and community safety.