Research On TBM Tunneling Performance And Its Brittleness Effect Of Extremely Hard Fused Tuff

There are few cases of long-distance fused tuff tunneling in TBM projects in China,and there is no relevant research report on its tunneling performance.Therefore,this paper takes the water conveyance tunnel of Zhuxi Reservoir in Taizhou City,Zhejiang Province as the engineering background to research on TBM tunneling performance in surrounding rock with high hardness and toughness,Includes TBM penetration,tunneling speed,construction speed,tunneling operation utilization,equipment intact rate,hob wear,rock brittleness and other aspects,which has reference significance for TBM Construction of other similar projects in the future.First,this article redefines and references the concept of normalized specific energy,According to the engineering data of Nabang Hydropower station,seven kinds of rock brittleness index methods based on stress-strain curve definition are analyzed and evaluated.The results show that the brittleness indexes B3 and B5 are more suitable for evaluating the brittleness of extremely hard rock.At the same compressive strength,the brittleness index of fused tuff is much lower than that of biotite hornblende plagiogneiss.Through the comparative analysis of tunneling data under the condition of the same compressive strength range of two projects,When the compressive strength is 130～200 MPa,the rock brittleness reduces the penetration of fused tuff to 0.84 times of gneiss,increases its specific energy consumption to 1.29 times of gneiss,and increases the average wear of each type of hob per 10000 cubic meters to 1.39 times of gneiss.Therefore,when predicting the tunneling performance,selecting the main technical parameters of TBM and designing the hob performance,if the rock compressive strength is higher than 130 MPa,the influence of rock brittleness should be comprehensively considered.Secondly,through the collection and analysis of TBM site tunneling data and cutter wear data,the tunneling performance of fused tuff TBM is studied,Including different surrounding rock types,lithology,various unfavorable geological TBM tunneling footage,tunneling operation utilization rate,equipment intact rate and various types of hob wear loss law etc.The results show that under the condition of type II fused tuff,the average daily footage is 20.5 m,the utilization rate is 55%,the average penetration is 4.2 mm/r,and the tunneling speed is 31 mm/min;Under the condition of type III fused tuff,the average daily footage is 19.6 m,the utilization rate is 50%,the average penetration is 5 mm/r,and the tunneling speed is 32 mm/min.Referring to the integrity rate of the overall equipment between 80% and 94%,it is concluded that the TBM can adapt to the extremely hard lava tuff geology and show high tunneling performance.In addition,Comparison with hob attrition data etc of Nabang Hydropower Station Project,the reasons for the rapid normal wear rate of the hob relying on the project and the multiple abnormal wear of the central hob are explored.Finally,this article aiming at the phenomenon that the normal wear speed of the on-site hob is faster,On the basis of applying tribology theory to predict hob wear,the actual contour curve of the cutter ring is introduced,and the formula for solving the comprehensive wear coefficient of the cutter ring is given again,which is used to predict the tunneling distance of the hob at each cutter location in the later stage.At the same time,compared with other models,the results show that the average error is6 % and the maximum error is 9 % when the model in this paper is used to predict the tunneling distance of the central hob.The average error of predicting the tunneling distance of other hobs is 6 %,and the overall error is 0～9 %.It is known that Whether it is the installed new knife,old knife or central hob etc,The average error of this model in this paper is relatively small,and the prediction results are more reliable.