The calculation for ultimate surrounding earth pressure on deep-buried tunnels in aeolian sand stratum to prevent surface collapse

Aeolian sand is characterized by low shear strength and poor self-stabilization, making the construction of tunnels in this stratum highly susceptible to collapse and instability, as well as causing surface subsidence and sand leakage, causing significant impacts on the local geology and environment. Tunnel linings that can provide adequate support are vital to the safety of construction. Firstly, the engineering and mechanical properties of aeolian sand were analyzed. Next, a combination of model tests, PFC modeling, and elastoplastic theory was applied to compare the extent of collapsed arches in deeply buried aeolian sand tunnels with and without support. Finally, a Newtonian iterative method was applied to derive the calculation of the soil pressure around the sand tunnel, and the applicability of the method was verified utilizing arithmetic examples. The results indicate the following: Tunnel collapsed arch cannot be formed during the aeolian sand tunnel excavation without support, but can be formed with support, and the range of this is by the Kastner (1949) formula. The extent of the collapsed arch in supported tunnels is related to the original earth stress, the support reaction force, and the tunnel radius, and is a half times the distance of the tunnel diameter outside the tunnel boundary when the burial depth is four times the diameter of the tunnel.