Upper Bound Solutions Of Earth Pressure Of Underground Cavity With Nonlinear Baker Failure Criterion

The stability of the surrounding rock of the underground chamber is highly concerned in the geotechnical engineering field.How to better support the underground chamber is one of the most concerned issues for geotechnical engineers.The surrounding rock pressure in underground chambers must be taken into consideration in the design of support.How to get the real pressure,is the difficulty faced in underground engineering.At present,there are mainly limit equilibrium and finite element method to study the stability of surrounding rock of underground cavern,and the upper bound method of limit analysis is a hotspot in geotechnical engineering,because of its simplicity.Numerous studies have shown that the properties exhibited by the rock are non-linear,and the linearity is only a special case.Therefore,according to the surrounding rock stability of underground cavern,surrounding rock as the research object,based on the limit analysis upper bound method of nonlinear Baker failure criterion,researched the surrounding rock pressure.The work and conclusions obtained in this paper are as follows:Firstly,according to the nonlinear characteristics of rock mass,combined the nonlinear Baker failure criterion and the limit analysis method,derived the formulas of pressure,which is based on the failure mechanism—wedge+single circle arc block+translational triangle block.Secondly,the Mohr-Coulomb failure criterion,Hoek-Brown failure criterion and Baker's failure criterion are used to calculate the upper limit solution of the underground chamber pressure in the same failure mode.The results are compared with the pressure calculated by Platts theory.It is shown that the upper limit of the surrounding rock pressure of the roadway under the Baker failure criterion is consistent with the pressure of the underground chamber through the other three theories,which indicates that the upper limit method of the underground chamber is calculated by the limit analysis upper limit method based on the nonlinear Baker failure criterion pressure is feasible.Thirdly,the influence of different parameters on roadway surrounding rock pressure is studied.It includes the influence of dimensionless parameters n,A,T,internal friction angle?_t,roadway section size l and h,side pressure coefficient K.And the influence of simultaneous change of several parameters on the upper bound solution q of roadway surrounding rock pressure is studied.Fourthly,the influence of different parameters on the pressure of underground chamber is studied.Including the parameters n,A,T,the internal friction angle_t?,the section size l and h,the side pressure coefficient K and the previous parameters on the upper limit of the pressure of the underground chamber.Fifthly,in calculated the upper limit solution of the pressure q,the angle of the complete failure mode can be obtained.The damage pattern corresponding to the angle is the optimized failure mode.Through the optimization of the upper limit solution,the failure modes corresponding to the three parameters n,A and T are obtained.Finaly,the surrounding rock pressure obtained by this method is compared with the surrounding rock pressure by numerical simulation and actual monitoring.It is show that the limit analysis upper bound method based on the nonlinear Baker failure criterion is reliable for calculating the surrounding rock pressure.