| The effect of the stratum caused by the construction of the overpass tunnel and the mechanical behavior of the supporting structure are complex.Especially when the new tunnel “zero distance” is over the existing tunnel,this effect is more obvious,and even when it is severe,it may even cause the tunnel support below.Structural damage and collapse of surrounding rock.Therefore,it is important to study the deformation characteristics of the existing tunnel supporting structures during the excavation process of new tunnels and the optimization of excavation methods.In this paper,relying on the Wenma Expressway Ganyanggou smoke tunnel cross-hole intersection project,using monitoring and measurement combined with three-dimensional finite element numerical simulation method,the stress deformation characteristics of the main tunnel support structure,the optimization of the method of exhaust smoke hole and The impact of earth-moving vehicles on the main tunnel was studied.The main research work and achievements are as follows:(1)Introduce the mechanics of tunnel excavation and the stress and strain laws during the excavation of overlapping tunnels above and below.(2)The engineering geological conditions and hydrogeological conditions of the cross-section of the cross-drift at the cross section of the Ganyanggou tunnel are introduced systemly,combines the force characteristics of the upper and lower cross-tunnels,formulates a site monitoring measurement plan,and analyzes the measured data.(3)The three-dimensional numerical simulation of the excavation process of the cross hole of the smoke exhaust was carried out,and the change law of the vertical deformation,lateral deformation and the maximum principal stress of the inner and outer side of the main line secondary lining were analyzed.The results show that the deformation of the main line is the uplifting of the dome and the arching of the outer drum.Determine the impact area on the exhaust from the stepped transverse tunnel face from the center of the intersection hole-10 m and ends at 18 m.(4)By simulating different construction conditions,comparing the deformation of the transverse tunnel,the maximum principal stress and the maximum shear stress in the inner and outer sides of the initial support,the optimum excavation footage and the height of the lower step of the smoke tunnel were obtained.The results show that the use of 1.8m footage and step height of 2.5m is more conducive to the construction.The horizontal plane on the horizontal cross hole of the smoke exhaust is from the cross center(coordinate 0m)to 20 m before excavation footage is taken 3m,and from-20 to 10 m is taken 2.4 m,take 1.8m within 10~18m,take 2.4m after 18 m.(5)The characteristics of the earth-moving vehicle were summarized by means of field investigation,the contact pressure between the wheel and the ground at the time of full-loading of the earth-moving vehicle was calculated,the dynamic load coefficient was determined,and the driving process of the vehicle was simulated by simulating different positions of the wheel.The effect of vehicle load on the secondary lining of the main line was analyzed.The results showed that the maximum increase of the stress of the secondary lining of the main line by the vehicle load was 13.41%,and the overall influence was not significant.It was the key to control the static pressure around the secondary lining of the main line after excavation.It is advisable to take appropriate measures to control the impact of the soil-moving vehicle within 3m from the intersection. |
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