Calculation method of supporting pressure of shield tunnel excavation face in sand considering friction between cutter and soil
The determination of the face limit supporting pressure is one of the key problems in tunnelling engineering.The friction between cutter and soil is generally ignored,and the calculation results of supporting pressure are conservative.In order to solve the problem,firstly,by considering the influences of the vertical friction between the shield cutter and the cut soil,the horizontal friction between the wedge and the upper soil,and the tunnel depth on the limit supporting pressure,a formula to calculate the limit supporting pressure in sand strata was deduced via trapezoidal wedge model.Secondly,the rationality of the proposed method was verified by comparing with other theoretical results and experimental results.Finally,the influence of friction between cutter and soil on the face limit supporting pressure under different conditions was discussed by parameter analysis.The results show that when other parameters remain unchanged,the face limit supporting pressure decreases almost linearly with the increase of the friction angle between cutter and soil.The friction between cutter and soil has positive influence on the face stability,and the influence on the limit supporting pressure can not be ignored.The stability of the excavation face can be effectively enhanced by properly increasing the friction angle between cutter and soil.The influence of soil-cutter friction on the limit supporting pressure in shallow tunnels is obviously greater than that in deep tunnels,which should be considered in cutter selection of the shield tunnelling.