| The special complexity of Chengdu sandy pebble stratum brings great difficulties to shield construction.In the process of shield tunneling,problems such as cutter head jamming,mud cake in the center,excessive wear of cutter head and shaft breaking of screw machine are easy to occur.The main reason is that the construction personnel have insufficient understanding of the soil movement law in the process of cutter head tunneling and the setting of shield tunneling parameters is not reasonable.Based on this,this paper obtains the law of soil movement in the process of shield tunneling by simulating the process of shield tunneling in sandy pebble stratum,which provides a reference for the construction company;at the same time,it analyzes the correlation between different parameters of shield tunneling,establishes the prediction model of tunneling parameters,and optimizes the parameters of active adjustment of Shield Based on the small torque of cutter head,the small thrust of shield and the good fluidity of soil Setting of guide tunneling parameters.The specific research work is as follows:1.According to the general situation and geological structure of Shanghong section of Chengdu Metro Line 6 phase I and phase II project,combined with the engineering practice,the stratum characteristics of sandy pebble stratum in this section are analyzed,and the load during shield tunneling is analyzed.2.Based on the theory and analysis method of discrete element,the micro parameter calibration of pebble soil is carried out by using the software of edem.According to the method and steps of the experiment,the simulation experiment model of edem parameter calibration is established,and the experimental design of particle accumulation angle is carried out by using the orthogonal experimental design method.The results of multiple simulation experiments are compared with the actual engineering results The micro parameters of the soil are determined according to the simulation model.3.Based on the composition of cutter head tunneling system,the edem simulation model of cutter head tunneling is established,and the pre-processing parameters and simulation scheme of cutter head tunneling model are determined according to the actual engineering situation.Firstly,through the simulation of the cutterhead excavation process by the edem software,the transportation process of soil particles,the process of ground settlement and the process of excavation parameters change in the process of cutterhead excavation are obtained;then the movement state and stress state of soil particles in the process of cutterhead excavation are analyzed from the three parts of cutterhead face,soil bin and screw conveyor respectively,and the process of shield excavation is obtained Finally,the finite element analysis of cutter head and screw machine is carried out through edem workbench joint simulation,and the stress distribution of cutter head and screw conveyor in the process of shield tunneling is obtained.4.Through the analysis of the change of parameters in the process of shield tunneling,the parameters of active adjustment and passive feedback are determined,and the effect of tunneling parameters in the actual project is analyzed.Based on the simulation model of cutterhead driving,different active adjustment parameters are changed,and multiple groups of simulation results are obtained.The results are compared and analyzed,and the correlation between driving parameters is obtained.Through the Latin hypercube experiment design method to design multiple groups of experimental samples,and using the optimized BP neural network program to simulate the sample data,the neural network prediction model of driving parameters is obtained.Based on the neural network prediction model,the key driving parameters are optimized by using the multi-objective optimization algorithm NSGA-2. |
