In order to investigate the frost-heaving characteristics of wintering foundation pits in the seasonal frozen ground area, an outdoor in-situ test of wintering foundation pits was carried out to study the changing rules of horizontal frost heave forces, vertical frost heave forces, vertical displacement, and horizontal displacement of the tops of the supporting piles under the effect of groundwater and natural winterization. Based on the monitoring condition data of the in-situ test and the data, a coupled numerical model integrating hydrothermal and mechanical interactions of the foundation pit, considering the groundwater level and phase change, was established and verified by numerical simulation. The research results show that in the silty clay-sandy soil strata with water replenishment conditions and the all-silty clay strata without water replenishment conditions, the horizontal frost heave force presents a distribution feature of being larger in the middle and smaller on both sides in the early stage of overwintering. With the extension of freezing time, the horizontal frost heave force distribution of silty clay-sand strata gradually changes from the initial form to the Z shape, while the all-silty clay strata maintain the original distribution characteristics unchanged. Meanwhile, the peak point of the horizontal frost heave force in the all-silty clay stratum will gradually shift downward during the overwintering process. This phenomenon corresponds to the stage when the horizontal displacement of the pile top enters a stable and fluctuating phase. Based on the monitoring conditions of the in-situ test, a numerical model of the hydro-thermo-mechanical coupling in the overwintering foundation pit was established, considering the effects of the groundwater level and ice-water phase change. The accuracy and reliability of the model were verified by comparison with the monitoring data of the in-situ test using FLAC3D finite element analysis software. The evolution of the horizontal frost heaving force of the overwintering foundation pit and the change rule of its distribution pattern under different groundwater level conditions are revealed. This research can provide a reference for the prevention of frost heave damage and safety design of foundation pit engineering in seasonal frozen soil areas.

This study comprises the design of rectangular underground water tanks under different ground conditions and the strength analysis of slab floor, walls, and foundation of rectangular underground water tanks. The importance and sustainability of water storage and management for humans is a very important and detailed issue. In this research, the design and analysis of rectangular water tanks to be constructed in ZA and ZE ground classes classified according to the Turkish earthquake regulation (TBDY 2018) were made using the IdeCAD program. The results of the stress, moment and deformation analyzes according to the design made with the design parameters used in this research showed that the rectangular water tanks to be built in the ZA ground class have structural strength against the stresses arising from soil, water and earthquake loads without suffering any significant deformation. The design values obtained using stress, deformation, and structure overturning moment analyses were found to be with in the limits of structural safety confirming the reliability of the design parameters. On the other hand, it has been found that underground water tanks to be built in the ZE soil class could also successfully resist to the lateral overburden and earthquake loads. However, it was determined that the deformations in the tank structure in ZE class soil were found higher than in the ZA class soil due to th e loose, weathered, and low bearing strength of the ZE class soils. This study also emphasizes the importance of using raft foundations under underground water tanks to be built on ZE class grounds to increase safety and prevent increasing deformations over time, such as creep.