Alternant active and passive trapdoor problem: from experimental investigation to mathematical modeling

Abstract

In the classical conception of the arching mechanism, the well-known trapdoor problem assumes distinctive modes (e.g., either active or passive mode) in the original geostatic overburden pressure. However, in various geotechnical applications, underground inclusions or structures may experience alternant upward and downward movements induced by construction activities or environmental changes, leading the ground to be initial loss or compaction state. If the initial disturbed state occurs, the estimation of vertical load on structures is improper based on classical trapdoor mechanism. In this study, a new conception, alternant active and passive trapdoor problem was introduced. Using a comprehensive measured system, such as particle image velocity technique and various sensors, alternant active and passive trapdoor tests were conducted to explore the mechanical behavior and kinematic mechanism of the backfill subjected to continuous loading and unloading. The development of arching with trapdoor displacement was visualized and quantified in different modes and states. Then, this problem was treated in a statical analysis based upon the visualized kinematic mechanisms. Solutions for the trapdoor load in the typical development states of arching were calculated by limit equilibrium method. Finally, two simplified ground reaction curves representing the progressive development of arching were proposed to facilitate in engineering applications. The simplified method was verified by the trapdoor test results.