Jacking Force Prediction for Box Jacking Tunnel Considering the Soil Arching Effect

Abstract

During the construction of box jacking tunnel, stress transfer caused by the soil arching effect is an important factor, affecting the jacking force. This study proposes a jacking force prediction method for box jacking tunnels under the complete and incomplete soil arching effect in sandy soils, which is divided into three soil domains, i.e., an external stable region, an elastic arch, and an internal loosened body. Three‐dimensional numerical analyses for box jacking tunnel at various cover depths are also investigated to show the stress changes in the soil around the tunnel and the evolution of soil arch formation. Finally, through theoretical derivation and case analysis, the ratio between the influence range of soil arching and the width of loosened soil, , is found to increase with increasing the tunnel size and internal friction angle of soil. The coefficient can be preliminarily determined to be approximately 1.4, with a marginal difference of 6.7% compared with the Terzaghi's proposal of 1.5. Results show that in sandy and silty soil strata, the proposed method outperforms the other methods, in terms of accuracy and adaptability. This study can serve as a theoretical reference for the design and construction of box jacking tunnels.