Research On The Method Of Recognition Boulder With Shield Tunneling Parameters

Shield tunneling technology has been widely used in metro construction for its advantages of high safety,reliability and wide application.However,some special geological conditions will be encountered in the construction process,which will cause difficulties in construction.In Beijing,Guangzhou,Shenzhen,Chengdu and other places of our country,there have been orphan stones encountered in tunnel construction,which often cause difficulties in shield tunneling,increased ground disturbance,aggravated surface settlement and other problems,and even cause engineering accidents in serious cases.Therefore,how to effectively predict,discover and treat the solitary stones is a difficult problem to be solved urgently in shield tunneling construction.Based on the construction project of Hengqin Tunnel and the geological data obtained from the project,the origin and distribution characteristics of the solitary stones are analyzed.The components of total thrust and cutter head torque of shield machine are systematically analyzed and studied.A mathematical calculation model of total thrust and cutter head torque of shield machine with solitary rocks is established.The influence of solitary rocks on shield tunneling parameters is studied.Statistical analysis of a large number of data collected by shield tunneling machine in the process of tunneling,determine the main tunneling parameters such as cutter head torque,shield total thrust and propulsion speed when encountering solitary stones.The correlation between tunneling parameters is studied.It is concluded that there is a very strong linear correlation between the driving speed and penetration,total thrust and penetration,and between the driving speed and the speed of screw conveyor.The concept of transition state of tunneling parameters and the method of predicting solitary stones by studying the characteristics of transition state of tunneling parameters are put forward.A BP neural network prediction model with input layer as tunneling parameters and output layer as ratio of total thrust of shield to cutter head torque and whether or not there are orphans in stratum is established.The model is verified and the error analysis of the prediction results is carried out.The results show that the recognition effect of orphans meets the requirements.The development of orphan stone prediction software is basically completed by using C# programming language.The application of the orphan stone recognition software greatly facilitates the prediction of the orphan stone in the process of shield tunneling,and protects the normal tunneling of the shield machine,thus improving the tunneling efficiency of the shield machine...