Study On Standard Of The Ground Surface Settlement And Structures Deformation Induced By Shield Tunnelling Construction In Beijing Subway

The shield tunnel has been great developed and used in Beijing. But some of the technology still exist many limitations. the forth line,the tenth line and the line for airport have used shield tunnel to practice and check this technology. In the thesis ,we have collected lots of files about the engineering geology condition,plane-vertical section,condition of nearby,advance parameter,ground surface settlement and structure deformation which were caused by excavation, we have made systemic studied on the ground surface settlement and structure deformation standard, the research results primarily reflected in the following:First, we made a classification about the geology of underground shield tunnel, one general geological conditions; the other is difficult geological conditions.Secondly, studying on the pushing parameter of common geology condition,difficult geology condition and nearby -through structure.1. The advance parameter for General geological conditions and difficult conditions1) General geological conditions. the average speed is 30 mm / min, the greatest speed is not more than 50 mm / min.the turntable rotation speed for motion is 1.5～2.0 rpm, the common speed is about 1.7 rpm. The coordinates of before shield point and after point should be controlled to within 30 mm .the maximum should not exceed 50 mm.2) Difficult geological conditions. The speed keeps in 15-20 mm / min. the turntable rotation speed for motion is 0.7～1.2 rpm, the lowest is about 1.0 rpm.2. The shield advance parameters for nearby -through structure1) Nearby the bridge piling. Reasonable positions pressure in the soil is around 1.0-1.5 bar, tunneling thrust should be controlled in the 800～1000 t; the turntable rotation speed for motion is 1.5～2.0 rpm; bubble dosage should be kept for 20～25 L, ring to each ballast Control of the vehicle within 3 to 3.5 the volume is not less than 4.5 m3 to ensure full filling the gap, to minimize the pier around the pile of soil disturbance.2) Shield construction across the river. Earth pressure is 1.0～1.5 bar; average tunneling speed control within 30mm/min; with an average speed of excavation should be controlled within 10～15mm/min; tunneling thrust should be controlled in the 700～1000t; the turntable rotation speed for motion is 1.5～2.0 rpm.3) Excavation through the base of railway. Normal speed should control in the 40～50mm/min, the crossing speed should be controlled at around 20～30 mm/min, the speed should be controlled even at 15-25 mm/min; we should strictly control the volume within 40m3～45m3; tunneling thrust should be controlled in the 2500~3000t; knife-torque control in the general 3000～3500 (kNm) range. The pressure on the soil strata is 0.1～0.2MPa.4) Through the base of ground structures. The normal speed is the 30～40mm/min, the max should be controlled within 50mm/min. The advance speed through the base is the10～15mm/min. Driving thrust be controlled in 800～1000t; the turntable rotation speed for motion is 1.5～2.0 rpm.Third, in the general geological conditions or the difficult geological, the reasonable control standard value of the ground surface settlement was caused by shield tunnel construction:1. General geological conditions.in the general geological conditions, the surface deformation control values should be in the range of-15～+5mm.2. Difficult geological conditions.According to difficult geological conditions, we set a more reasonable control of the value of surface settlement should be -20～+10 mm.Fourth, the proposed subway shield tunnel in close-up through the tunnel under construction shield caused by the building (structure) to build the value of deformation control standards:1. across the base of bridge piling1) the settlement value of Bridge piles should be controlled in the range of 0～3mm; simple girder settlement be controlled in the range of 20 mm (vertical); the value of landscape orientation settlement should be 2mm to ensure that the tilt of the bridge. The side of river surface and bridge pole's settlement value should be less than 20mm.2) through the base of railway. the overall settlement should be controlled to within 10 mm; track differences in the settlement should be controlled within 5mm; track of the overall structure of the settlement in the control of 10～15mm within the scope; track structure differential settlement should be less than 5 mm.3) through the structures. The largest surface settlement value should not exceed 10mm.In short, the results were reflected in this thesis, which will provide reference for subway design and congstraction.