Effectiveness of Various Load Reduction Methods for Deeply Buried Structures under Seismic Loads

Load reduction methods (LRMs) for the deeply buried structure such as a high-filled cut-and-cover tunnels (HFCCTs) under seismic loads are complex when compared with cases under static loads. The soil arching effect (SAE) for load reduction mechanisms is ambiguous. Unfortunately, very limited related research focused on these LRMs subjected to earthquake loads. This paper mainly focused on investigating the SAE induced by different LRMs under dynamic loads. Parametric studies were conducted using FLAC3D to assess the effectiveness of these LRM based on the variations of the SAE in soils under three different seismic waves. Several proven effective LRMs such as the inclusion of expanded polystyrene (EPS) and combined with concrete wedges were analyzed. Considering the variations of vertical soil pressure (VSP) and lateral soil pressure (LSP), the results show that the SAE is significantly related to the height and thickness of the soil arching zone (SAZ) that develops, which in turn affects the soils pressure distribution (SPD) around the CCT’s structures. In addition, the use of EPS above and on both sides of a CCT to reduce both VSP and LSP simultaneously was found to resist seismic loads more effectively.