Supporting Pressure for Tunnel Face in Water-rich Weathered Rock Masses Based on a Multi-log Spiral Failure Mechanism

To avoid introducing the generalized Hoek-Brown (GHB) strength criterion into the stability analysis of tunnel face directly by any linearization of Hoek-Brown strength criterion, this paper constructed a multi-log spiral failure mechanism for shallow buried tunnel excavation face in water-rich strata based on the limit analysis theory. Considering the existence of pore water pressure, the expression of the critical supporting force was derived from the tunnel face energy balance equation, and the optimal upper bound solution of the supporting pressure can be obtained through the optimization. Consequently, the influence of the GHB strength parameter, pore water pressure, rock mass unit weight, and the tunnel depth ratio on the stability of tunnel face were analyzed. Finally, a series of stability charts of the most critical supporting pressure of the tunnel face were presented to obtain the supporting pressure of tunnel face conveniently. This work provides a theoretical basis for the preliminary design of shield tunnel in water-rich stratum.