Study and application of support pressure in shallow buried hard rock tunnels considering laminated arch transfer effect
In shallow buried hard rock tunnels,the ground arching effect has a significant impact on tunnel stability.It is of great significance to clarify the interaction mechanism between the ground arching effect and tunnel support for determining the tunnel support pressure.In this study,a mechanical model has been constructed that can be applied to the laminated arch transfer effect in shallow buried tunnels based on the ground arch transfer effect.By analyzing the principal stress deflection and lateral limiting force of single-layer arches,the method for calculating the stress transfer in laminated arches is derived,and combined with the distribution characteristics of the principal stresses on the differential rock strips in the loosening zone,the formula for calculating the support pressure of shallow buried hard rock tunnels in stable state is obtained by using the limit equilibrium analysis method.Modelling tests and field monitoring are carried out to verify the applicability of the calculation method in the Qingdao Metro Line 6 project.The results show that:(1)The parametric sensitivity analysis indicate that the support pressure gradually decreases with the angle of internal friction.When the tunnel depth does not exceed the thickness of the maximum load transfer zone(namely H≤2.4B),the support pressure gradually increases with the tunnel depth,and the sensitivity of the support pressure decreases with the layers of laminated arches n.(2)The implementation of active support enhances the constrain effect of the surrounding rock,which further improves the critical instability load rating of the tunnel on the basis of significantly enhancing the mechanical properties of the tunnel's surrounding rock.Compared with passive support,the stress transfer effect of the enhanced laminated arch increases the load carrying capacity of the surrounding rock by 11.9％.(3)The average relative errors between the predicted and measured tunnel support pressure under different modes are within 20.9％,which indicates that the predicted tunnel support pressure is in good agreement with the measured value when considering the laminated arch transfer effect,thus verifying the accuracy and applicability of the support pressure calculation method.The results have a significant reference for the safety design and evaluation of shallow buried hard rock tunnel.
tunneling engineeringshallow buried hard rockmodel testtheoretical analysisarching effectsupport pressure
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维普
