| The stability evaluation of tunnel surrounding rock is an important part of highway tunnel construction.The BQ method is used for surrounding rock quality classification for Xieyuan Tunnel in Fujian,based on the field survey,statistical data,engineering experience and predecessor achievement.Hydrodynamic method and precipitation infiltration method were used to analyze the water inflow.According to the method of hydraulic fracturing and acoustic wave test,the characteristics of ground stress distribution and the rock burst discrimination in tunnel area were carried out.Furthermore,the stability of the surrounding rock is evaluated comprehensively and the following results are obtained.The surrounding rock of the tunnel trunk is given priority to with ?~ level.And ?the surrounding rock of the tunnel entrance and exit section,lithologic contact zone,influence belt of faults,Geophysical low resistivity zone and concentrated joint band is belonged to V~ ?level.It shows that the surrounding rock field investigation grading is basically consistent with the BQ classification According to the hydraulic fracturing test,the water yield for the borehole of SK16-2 is small with the poor rock permeability and the good supply condition,because the borehole is in the dese zone.And the SK-3 has the large water yield with the good rock permeability and supply condition.CK1046 has a relatively stable structure with poor permeability,poor supply and small water yield.But for the CK1047,CK1048,CK1049,the permeability though is poor,the supply condition and the water yield are all good.These hydraulic characteristics of the holes are unfavorable to the stability of surrounding rock.Base on the analysis of groundwater dynamic experiment and precipitation infiltration method,the maximum total water inflow of the single hole of the tunnel is proposed to be 4289.7m3/d,and the normal water inflow was 3388.8m3/d.Where the measured amount of water inflow is 4100m3/d,basically the same as the predicted results.With the result of the crustal stress analysis,when buried depth is >417m,the tunnel surrounded by the weak weathered biotite granite is belonged to the high stress area.While when buried depth is >394m,the weak rock burst may occur for the tunnel.The possibility of the occurrence of the rock burst for the other tunnel section is not high.According to the acoustic test data,if Rc=95MPa is used in the xie yuan tunnel,no rock burst will be produced.The new tectonic movement is not active in the tunnel area and the surrounding area,so the stability of the site is good.The slope of the entrance is overall stable.But the slope body is mainly derived soil and complete strong weathering rock,it is easy to collapse after excavation,so the protection should be strengthened.The side slope of the outlet is overall stable.The side slope of the outlet is block,medium-slightly weathered rock,better stability after excavation,so the grade of the rock is V level.For the whole tunnel,the body of the tunnel is in class II-III according to the surrounding rock classification.Some individual joints,lithologic contact zones and influence belt of faults are in the V-IV level.In general,the surrounding rock of the Xieyuan Tunnel is in a relatively stable state.In the construction process,there is no large-scale collapse,which is basically consistent with the evaluation results of the study. |
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