Prediction Of Rockburst Hazard And Its Effection On The Engineering Project Along The Tunnel From Maerqu River To Acehe River

On the basis of sufficient collecting, analyzing, summarizing the past research results,through field geological research, in situ stress measurements, indoor rock physics mechanicsproperties examination, simulative calculation the principal district of tunnel engineering areaby the software Ansys5.6, this paper predicts rockburst hazard in deep-long tunnels at Ma ErQu-Ar Ke River of the Water Diversion from the Upper Yangtze River Into the Upper YellowRiver. By less than two years' study, it gives emphasis to five points as follows:(â…°) Strata, landforms, topography, engineering geology and active faults at the engineeringarea.(â…±) Present in situ stress distributing regulation and its features by hydraulic fracturingcrustal stress measurement in deep-long tunnel engineering area at Ma Er Qu-Ar Ke River.(â…²) Collecting typical rock sample at scene, testing differents typical rock mechanicsproperties and parameters.(â…³) Classifing rock-soil mass, especially mechanics properties of structural faces insandstone mass, slatemass and granite mass.(â…´) Caculating, analyzing present in situ stress field of important district in tunnel area bymaking use of three-dimention finite element.(â…µ) On the basis of that, analyzing and predicting the possibility of rockburst occurrence inthe deep-long tunnel, putting forward prevention and cure measures and constructive opinionsof rockburst disaster during the construction.Through the work done above, the work progress and cognition are obtained as follows:1. In this paper, as the deep-long tunnels at Ma Er Qu-Ar Ke River of the Water Diversionfrom the Upper Yangtze River Into the Upper Yellow River main research object, places andgrade of rockburst occurring are analyzed and predicted during the tunnelexcavation.Furthermore the basis is provided for reasonable excavation designs, construction,scheme of reinforce surrounding rocks and the specific measure of prevention and cure byopen geology investigation, in situ stress measurement, different types of rock mechanics test, 3-D, 2-D finite element numercal simulation and different criterions of rockburst.2. Through the open engineering-geology investigation, the main rocks are defined as shallowmetamorphic sandstone and slate in the tunnel engineering area. The main form constructionin sandstone is of medium thick layer- thick layer.The slate is main for thin layer formconstruction. According to initial return-shoot mensuration results, shallow airslakesandstone's single-axes resist-pressure strength is 41MPa～128MPa and shallower airslakeslate' single-axes resist-pressure strength is 21～95MPa generally along the tunnel. Amajority of slat is middle-hardness and the others is hard or rather soft.3. Through testing in situ stress in tunnel engineering area, a comprehensive cognition aboutin-situ stress field at engineering as follows:The horizontal principal stress is main in in situ stress field at tunnel engineering area. Theratio of horizontal principal stress and vertical principal stress in drillhole is higher(i.e. S_H＞S_h＞S_V). That shows the stress condition in this area is reversed fault state. The in-situ stressconditions at Ba Yan Ka La mountain sides are totally different, the northern side low, in theorientation of north and the southern side high, in the orientation of north-east. The ratio ofsouth-side and north-side is 5～10. The more large the depth value is, the more high the insitu stress value is.The law of stress change with depth according to the principal stressesvalue tested as follow: S_H=-4.13+0.077D S_h=-2.62+0.057DD——depth of drillhole(m); S_H——the max horizontal principal stress(MPa); S_h——the minhorizontal principal stress(MPa).4. Based on the finite element's results of Ma Er Qu-Ar Ke He deep-long tunnel, in generally,at the fault's two sides the horizontal principal stress is high and concentrated in evidencealong the tunnel and the stress values areσ₁ =81 MPa and 49.5 MPa,σ₂=46.1 MPa and 24.3MPa. The stress values become gradually lower at the tunnel's ends and more low in fault.The in-situ stress values are higher at the middle of tunnel. For the vertical principal stressσ_3max is 11.5 MPa, at the fault's sids are the same high.The 2-D finite element section mode's results that is vertical to the tunnel's axis show as follows:The vertical principal stressσ₂ is high at tunnel's top and floor. The maximum principalstress value isσ₂=34.7 MPa at the tunnel's top. The vertical principal stressσ₂ is low attunnel's middle,σ₃ is the horizontal principal stress,σ₃ is low at the section's sides and ishigh at the section's top. The minimum is 0.8MPa. The maximum is 132.6MPa. This is aphenomena of in-situ stress re-distribution and stress concentration to some extent aftertunnel's excavation.5. Through analyzing the relation of stress state and rock's strength adoption Lu Sheng's,Zen-yu TAO's, Fa-liang HOU's and Russenes's rockburst criterions, the in-situ stresscondition that rockburst occurs is made and the rockburst that will occur at tunnel's section insandrock body is predicted as high strengthâ…£degree during the tunnel's excavation.In this paper, the innovations as follows:1. The predecessors almost did nothing about wether is a foundation geology work or theconcrete engineering disaster studies for the deep-long tunnels project at Ma Er Qu-Ar KeRiver of the Water Diversion from the Upper Yangtze River Into the Upper Yellow River,especially predicting geology disaster for concrete work projects, so this job done in thispaper in itself is a work of filling in the gaps in this fields.2. Based on open geology survey, in situ stress measurement, rock mechanics examination indifferent type, finite element numercal simulation and inversion the present in situ stress inthe tunnel engineering area by the software Ansys, the in situ stress's distribution rules alongthe tunnel engineering area are analyzed and estimated in a comprehensive way, places andgrade of rockburst occurring are analyzed and predicted by different criterions of rockburst athome and abroad during the tunnel excavation. Furthermore the basis is provided forreasonable excavation designs, construction, scheme of reinforce wall rock and the specificmeasure of prevention and cure.3. In the course of study of rockburst disaster prediction in tunnel, the scientific basis forengineering application is provided from traditional qualitative analysis to quantitativeanalysis.4. Through Simulating, calculating, analysizing and contrasting the tunnel's in situ stress state before excavation with the state after excavation by current finite element software Ansys, theweak link of engineering is put forward. The scientific basis for the important prevention andcure district of tunnel and further work is provided.