Research On The Impact Of Shield Tunneling On The Stratum Subsidence And Adjacent Piles

Due to high automation, little interference to the surface buildings and traffic andmany other advantages, shield tunnel is applied more and more extensively. However,the soil will be disturbed inevitably in process of shield construction, which will leadto surface subsidence and building damage, etc. During shield tunneling, developingmonitoring work of deformation of the soil around the tunnel and surface subsidence,studying the impact of shield tunnel on the pile foundation of building andsurrounding environment, and how to reduce project investment is urgent in thepresent research.This thesis based on model test of Shield Tunnel. The dynamic excavationprocess of shield tunnel is simulated with the large-scale finite element softwareMIDAS/GTS. The interface element between the Shield shell and soil, groutingpressure, capsule pressure, jacking force and elastic-plastic are considered by thefinite element simulation. The deformation of pile foundation and ground settlementthat caused by shield construction are studied when there are buildings on one side ofthe tunnel. By comparing the results of numerical simulation and the results of themodel experiment, the reliability of the three dimensional finite element model isverified. Meanwhile on the basis of the simulation of excavation,the distribution ruleof surface subsidence is studied when there are buildings around the tunnel. Thearticle preliminary discussed the role of the structure stiffness and the influences ofshield parameters such as pressures of grouting, soil chamber, jacking force on landsubsidence. The deformation of pile foundation is studied when there is structuraladjustment of the buildings. The main research results are as follows:1.When there are buildings, the distribution curve of surface subsidence isgreatly different to the case that there are no buildings around the tunnel. Thedirection of maximum subsidence deviated from the buildings when there arebuildings around the tunnel, and deviated from the center of the shield tunnel. Thegreater of the structural stiffness of the buildings, the stronger of constraint andregulation on deformation. The settlement curve of the surface becomes flat whenthere are buildings on one side of the tunnel, and the width of the settlement troughbecomes bigger.2.Under the condition that the other parameters don’t change, the closer is thepressure of capsule to the original lateral earth pressure at rest, the smaller is theamount of land subsidence. The subsidence gradually decreased as the driving force of jacks and grouting pressure of the shield machine increased. The influence ofgrouting pressure on surface subsidence is significantly greater than the driving forceof jacks.3.Vertical settlement of the pile increased gradually in the process of shieldexcavation. The influence scope of settlement of pile foundation that induced by theshield construction is in-0.6D to+2.6D range in the direction of tunnel driving.Meanwhile, the influence scope is within+2.0D on the cross section of the shieldconstruction.4.The horizontal displacement of the pile decreased gradually as the distancebetween outer edges of shield tunnel and pile increased. Especially, and the horizontaldisplacement is more obvious when the distance is within+1.8D. The maximum axialforce and moment of the pile are all both near to the springing line of the tunnel.