To tackle the response problem of existing tunnel induced by adjacent excavation in soil-rock mixtures

numerical simulation tests based on discrete element method were utilized for investigation. By using the particle flow code software PFC2D

the micro structure of the soil-rock mixture

the tunnel lining structure

and the pit retaining structure were finely modeled

and the construction process was simulated. The influences of the rock content (w) on the responses of tunnel lining due to excavation nearby in the cases of different tunnel locations were systematically investigated. Results show that when the tunnel was located in the active earth pressure zone

with the value of w exceeded 60%

the increase in w resulted in the formation of rock skeleton around the tunnel segment

which decreased the tunnel responses induced by lateral excavation. When the tunnel was located in the passive earth pressure zone

as the value of w was lower than 75%

the excavation-induced tunnel responses started to decrease with the increase in the value of w; when the value of w exceeded 75%

such effect on tunnel responses induced by excavation above the tunnel would lose efficacy.