Progressive Development of Two-Dimensional Soil Arching with Displacement

Soil arching is a phenomenon describing stress redistribution due to relative movement between adjoining portions. It commonly exists when soil interacts with structure elements, such as tunnels, retaining walls, buried structures, and piles in pile-supported embankments. A yielding or ultimate state of soil (i.e., the shear stress in soil is equal to its shear strength) is mostly assumed in analytical models for soil arching. In reality, the level of shear stress and the shape of the slip surface in the soil depend on the magnitude of relative movement of the soil. In this study, a custom-made trapdoor test box was used to investigate the progressive development of soil arching with the trapdoor displacement. The dimensions of the test box was 1.76 m long, 0.46 m wide, and 1.48 m high, whereas the trapdoor had dimensions of 0.36 m wide and 0.46 m long. Earth pressures were installed on the top and sides of the trapdoor to monitor the development of soil arching with the displacement of the trapdoor. Furthermore, data from five references available in the literature were adopted to evaluate the progressive development of soil arching with the displacement for different geotechnical applications. Terzaghi's method was used to calculate the two-dimensional soil arching ratios (i.e., the measured earth pressure divided by the overburden pressure) in all cases in this study using three different values of lateral earth-pressure coefficient (K), and the results were compared with the measured results. Terzaghi's method calculated the soil-arching ratios reasonably well when the trapdoor displacement was equal to or larger than 10% of the trapdoor width. To facilitate the application of progressive development of soil arching with displacement in engineering practice, a simplified ground reaction curve (GRC) was proposed as three straight lines to represent the progressive development of two-dimensional soil arching with relative displacement. The methods for determining four required parameters were provided, and the proposed method was verified using three trapdoor test results from both this study and the literature.