17:15 〜 18:45
[AHW17-P10] Analysis of multi-layered groundwater level changes and soil consolidation
キーワード： Land subsidence, Pumping tests, Terzaghi's consolidation theory, multi-layered groundwater level changes
Land subsidence in the southwestern coastal plains of Taiwan is a prevalent geological hazard, primarily stemming from the rapid expansion of activities such as agriculture, industry, and aquaculture, leading to an urgent demand for water resources. This demand has turned groundwater into a relatively easily accessible and cost-effective water source. However, it has also triggered the issue of excessive groundwater extraction in many flatland areas, resulting in a continuous decline in the groundwater table and ultimately causing severe and irreversible land subsidence.
This study conducted pumping tests at Yuanchang Elementary School (YC), situated in the central part of the Choushui alluvial fan. The tests involved pumping at five different depths. Simultaneously, changes in water levels in 15 stratified wells were recorded, along with variations in the depth of multi-level compaction monitoring well . The objective was to gain comprehensive insights into the intricate relationship between water level drawdown and subsidence behavior. In order to analyze the relationship between water level changes and soil compaction, this study applied Terzaghi's one-dimensional consolidation theory to the calculate stress changes and soil compaction which induced by changes in hydraulic head. Finally, the calculated values were compared and validated against the observed changes in the multi-level compaction monitoring well.
Taking YC No. 1 as an example, the thickness of the soil layer is 22 m between NO.5 and NO.7 magnetic rings, and its main composition is sand. The results show that the difference between the theoretical value and the measured value is approximately 7.24 mm. This difference reflects the effect of expansion in adjacent soil layers and the hysteresis effect of pumping. This outcome underscores the complexity of subsidence in the geological strata, particularly emphasizing the significance of accounting for the characteristics of each layers.
This study conducted pumping tests at Yuanchang Elementary School (YC), situated in the central part of the Choushui alluvial fan. The tests involved pumping at five different depths. Simultaneously, changes in water levels in 15 stratified wells were recorded, along with variations in the depth of multi-level compaction monitoring well . The objective was to gain comprehensive insights into the intricate relationship between water level drawdown and subsidence behavior. In order to analyze the relationship between water level changes and soil compaction, this study applied Terzaghi's one-dimensional consolidation theory to the calculate stress changes and soil compaction which induced by changes in hydraulic head. Finally, the calculated values were compared and validated against the observed changes in the multi-level compaction monitoring well.
Taking YC No. 1 as an example, the thickness of the soil layer is 22 m between NO.5 and NO.7 magnetic rings, and its main composition is sand. The results show that the difference between the theoretical value and the measured value is approximately 7.24 mm. This difference reflects the effect of expansion in adjacent soil layers and the hysteresis effect of pumping. This outcome underscores the complexity of subsidence in the geological strata, particularly emphasizing the significance of accounting for the characteristics of each layers.