Numerical spring-based trapdoor test on soil arching in pile-supported embankment

As an important load transfer mechanism within the pile-supported embankment, soil arching is frequently investigated by trapdoor tests. The traditional trapdoor test is usually conducted by actively lowering an intact rigid plate to predesignated elevation and the coupled effect among the pile, overlying embankment fill, and the soft soil on the soil arching is oversimplified. To include the coupled effect, a numerical feasibility study of spring-based trapdoor test using particle flow code (PFC) was conducted, where the displacement of the trapdoor is dependent on the rigidity of the trapdoor and the upper load. A single spring-based trapdoor (SS-TD) model and multiple spring-based trapdoor (MS-TD) model were validated by comparing with an existing study and the comparison indicates that the tendency of all results is generally consistent. To offer guidance for practice engineering, the stiffness of springs is further correlated with the realistic modulus of subgrade reaction, ks. Then, the performances of the two spring-based models and the traditional trapdoor model in predicting the soil arching were compared in terms of soil arch height, soil arching ratio (SAR), and settlement. Interestingly, settlement distribution within the region above the height of the soil arch of the SS-TD model is found different from that of the traditional trapdoor model. The inner soil arches are monitored in the MS-TD model when displacing the trapdoor and they can transfer the load toward two ends of the trapdoor resulting in a more uniform stress distribution on the trapdoor.