Using nonlinear stochastic poroelastic theory to evaluate the quantity of discharge and subsidence

Subsidence in Yunlin area is a serious and continuous problem. Taiwan High Speed Rail passes through this area and has been affected by subsidence. It is very important to understand the mechanism of subsidence and the pumping impact on the subsidence area for land and groundwater management. This study uses the nonlinear stochastic poroelastic theory to construct numerical models for four observation wells in subsidence areas. Laboratory test data from drilling well is adopted in the subsidence models. The quantities of excess loading and discharge based on the datum year are evaluated by fitting the subsidence historic data. The results show that the excess loading is 0~1.78 kN/m ², and the excess discharge is 33~291 t/day. The excess discharge quantity is about 1.3~1.7% ofthe total pumping quantity per year. Calculated subsidence shows an underestimated. This might be due to an increased pumping around this area. The quantity of discharge can be used to evaluate the pumping quantity in the vicinity area around the observation wells. Then, the prediction of subsidence and the uncertainty analyses in the four observation wells are evaluated. The results show that subsidence in Yuanchang well is the largest. If the situation does not be improved, the subsidence quantity around Yuanchang well will be 0.41 ± 0.83 m. However, the uncertainty of the result is relatively large; it can be diminished by acquiring more data or using a data-conditioned model. This study provides a method to evaluate the discharge and settlement with uncertainties in subsidence areas. The results are useful for land and groundwater management.