Research On Real-time Identification Method Of Surrounding Rock Based On Tbm Excavation Characteristic Parameters

With the rapid development of our economy,large-scale infrastructure needs to be built,and the application of TBM is becoming more and more extensive.Compared with the traditional drilling and blasting method,the TBM construction method has the advantages of high efficiency,high quality,safety,environmental protection and a high degree of automation,and is the most advanced hard rock tunnel construction method in the world at present.But,because the surrounding rock condition in front of the tunnel face can not be directly observed by TBM operator during the excavation,it is vulnerable to the threat of bad geology.Based on the on-site construction data from Xinjiang EH project,a characteristic parameter that would reflect the change of excavating rock is presented in this paper,which can be displayed visually in the operating cabin.Based on the excavation data collected at the site and the surrounding rock statistics,this paper analyzes the law between the surrounding rock parameters and the excavation parameters,and finds that there is a strong correlation between them.The average of the excavation parameters under the different surrounding rock categories is calculated,and the law between the excavation parameters and the penetration under the different surrounding rock categories is analyzed.The linear correlation between the cutterhead thrust and torque and the penetration is obtained,and the penetration increases with the increase of the thrust or the torque.Thus,it is proposed to use the excavation characteristic parameter FPI to reflect the change of surrounding rock,and the FPI calculation method is given.The range and average of the FPI of the excavation feature parameters are calculated according to different types of surrounding rock,and it shows the decreasing trend of FPI from class II to V surrounding rock,and therefore it is feasible to reflect the change of excavating rock with the change trend of the excavation feature parameter FPI.The value of FPI is larger when the rock is hard and complete,and is smaller when the rock is weak and broken.Further,because bad geology can seriously affect the construction efficiency of TBM,and introduce a great threat to the safty of the equipment and operators,a bad geological early warning method based on the excavation characteristic parameter FPI is proposed,and the early warning limit values of FPI are given.Firstly,under very hard rock conditions,the upper limit of secondary-level warning is set to 70 and the upper first-level warning is 140 according to the rock compression strength and the corresponding penetration.Exceeding the warning value reminds the operator that the rock in front of the tunnel face is very hard or extremely hard and requires attention to adjust the operational parameters and check the cutters timely.Secondly,in the case of weak or broken surrounding rock or when encountering a fault zone,the downward trend of FPI changes and the average value of FPI in the period before the occurrence of geological disasters,such as a collapse cavity or landslide,the lower limit of the weak rock secondary-level warning is set to 15,and the lower limit of the weak rock first-level warning is 10.Exceeding the warning value reminds the operator that the rock in front of the tunnel face is very weak or fractured and requires attention to adjust the operational parameters and check the face rock condition,and prepare proper rock support.Finally,the real-time rock recognition software system is designed and developed.The value of the FPI and its change trend are directly displayed at the TBM operation cabin,and a bad geological warning is added at the same time.When the value of the FPI exceeds different warning values,the alarm indicator will flash in different colors.In this way,the operator can be reminded to pay attention to the changing trend of surrounding rocks,adjust the driving parameters and check the cutters and the extremely bad geology,and make timely rock support decisions.The method of identifying and warning the surrounding rock of TBM tunneling proposed in this paper is reliable and practical,which is of great value to TBM's safe and efficient tunneling and preventing TBM from being stuck.