Numerical analysis of hydrological response in loess excavation and filling area under multi-year precipitation infiltration

In order to study the evolution of the hydrological environment in loess excavation and filling project under multi-year precipitation infiltration, the hydrological responses of the excavation and filling area in Yan’an New District are simulated, based on the actual precipitation data of several years and field monitoring results. In addition, the drainage rate of the blind ditch is defined to characterize the drainage state of the blind ditch. Considering the variation of the drainage state and multi-year precipitation infiltration, different simulated cases are established. The results show that the proposed model is verified by the field monitoring results, which could reliably reflect the evolution of the pore water pressure (PWP) and the groundwater table (GWT). The transient saturated zone is formed near the excavation and filling interface due to the multi-year precipitation infiltration. And the formation and development of the transient saturated zone are closely related to the hydrological response of the loess excavation and filling area. The spatial and temporal variations of PWP and GWT are mainly affected by the changes in precipitation infiltration and drainage capacity of the blind ditch. Moreover, the hydrological response has a certain hysteresis to precipitation and is controlled by the topography and stratum difference of the undisturbed foundation. The research results should be helpful for the stability evaluation of loess excavation and filling project and the design of drainage facilities.