Ground reaction curve for tunnels with jet grouting umbrellas considering jet grouting hardening

• We calculate the ground reaction curve for tunnels with jet grouting umbrellas.
• We propose a new method to calculate the curve considering jet grouting hardening.
• We provide a lower bound for convergence and a upper bound for pressure in tunnels.
• Ignoring the hardening can lead to underestimation of the pressure on supports.
• Our method can be extended to tunnels in ground with time-dependent behavior.

In the calculation of the reaction curve for grounds reinforced with jet grouting umbrellas in tunnels, the jet grouting progressive hardening is ignored by assuming mean values for the jet grouting properties. In this paper, we present a new procedure that calculates the reaction curve for these grounds, considering jet grouting hardening. Tunnel excavation is represented in the ground plane-strain analysis by increasing the tunnel convergence at a rate obtained from the tunnel longitudinal deformation profile. This novelty allows us to perform the analysis at an accurate rate, which is critical for jet grouted tunnels. Using this new approach, one can estimate a lower bound for convergence of supported tunnels and hence an upper bound for pressure on the tunnel supports. Using a finite element model, we calculate the ground reaction curves for a case study tunnel with and without considering jet grouting hardening. The resulting curves illustrate that ignoring the jet grouting hardening can lead to an unsafe design of these tunnels. We use the ground reaction curve to also estimate the savings in tunnel supports due to jet grouting and the efficiency of jet grouting at different tunnel advance rates.

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