Abstract In-situ tests were carried out regarding the mechanical characteristics of the support system of a diversion tunnel in soft rock by using one project as an example, and a calculation method is presented for calculating the bearing capacity and strength safety coefficients of secondary linings in the construction of soft rock tunnels based on the strength reduction theory and numerical simulation analysis. Additionally, the stability of the surrounding rock and secondary lining is estimated and analyzed. The results indicate that: 1) the sidewall rock bolts play an important role in anti-pulling-out capacity, and the plastic zone of weak surrounding rock determined by the neutral point of rock bolts tends to develop and expand continuously; 2) in the primary support, the supporting effect of a steel arch will take effect immediately after it is erected, which plays a major role in surrounding rock support; 3) the secondary lining shall bear 12% of the surrounding rock load released during the construction period; 4) the stress concentrated area at the foot of the wall has the lowest safety coefficient; and 5) the calculation results of the secondary lining bearing characteristics basically agree with the in-situ test conclusions regarding secondary lining contact pressure.
Abstract：
In-situ tests were carried out regarding the mechanical characteristics of the support system of a diversion tunnel in soft rock by using one project as an example, and a calculation method is presented for calculating the bearing capacity and strength safety coefficients of secondary linings in the construction of soft rock tunnels based on the strength reduction theory and numerical simulation analysis. Additionally, the stability of the surrounding rock and secondary lining is estimated and analyzed. The results indicate that: 1) the sidewall rock bolts play an important role in anti-pulling-out capacity, and the plastic zone of weak surrounding rock determined by the neutral point of rock bolts tends to develop and expand continuously; 2) in the primary support, the supporting effect of a steel arch will take effect immediately after it is erected, which plays a major role in surrounding rock support; 3) the secondary lining shall bear 12% of the surrounding rock load released during the construction period; 4) the stress concentrated area at the foot of the wall has the lowest safety coefficient; and 5) the calculation results of the secondary lining bearing characteristics basically agree with the in-situ test conclusions regarding secondary lining contact pressure.
.Study of the Mechanical Characteristics of the Support Structure of a Deeply Buried Diversion Tunnel in Soft Rock[J] MODERN TUNNELLING TECHNOLOGY, 2015,V52(2): 36-43
2015, Vol. 52 