| With the rapid development of China's modernization, the level of construction of tunnel engineering is also rising. Due to the limit of the engineering geological conditions and environment outside the tunnels, more complex tunnel project cases are arisen,such as, ultra-shallow, large-section, close distance twin tunnels.The stability of surrounding rock of such tunnels are difficult to control, its construction is highly difficult. Furthermore, when the important buildings (structures) around the construction site, the problems of the ground disturbance and land subsidence caused by the construction of tunnels will also affect the safety and long-term of the surrounding buildings.Thus, with the boundary conditions of overlaying buildings(structures),the construction of the ultra-shallow, large-section, close distance twin tunnels is highly difficult and riskly. The mechanism of the land subsidence and the distribution patterns of the land subsidence caused by the construction are very complex.Researches are rare reported both at home and abroad in this field.The improvement of the theory is out of keeping with the rapid development of such projects. Thus, the study on the influence of deformation of the surrounding buildings(structures) under the construction of the tunnels that ensures the safety use and running of surrounding buildings have important directive function.This paper based on summarization of the achievement of previous researches and closely connected with the significant project of QiLin Mountain Tunnel in Shenzhen, using the finite element software MIDAS/GTS to build the two-dimensional and three-dimensional models to simulate the influence on the deformation of the overlying high-voltage tower under the construction of the tunnel on the actual complex conditions of stratums, to analyze the deformation laws of the land and foundation surface of the overlying high-voltage tower.A system of the mechanical response that from the determination of the simulate parameters,build the two-dimensional and the three-dimensional construction dynamic simulation models to deformation law of the surface is set up. Main contents and results are as follows: 1. The constitutive relation and strength theory of surrounding rock used in the numerical analysis are discussed. The factors of the stability of surrounding rock are discussed.The basic methods of the analysis of rock stability are briefly summarized.2. The select methods and determination of the parameters of numerical analysis in the geotechnical engineering are discussed.3. The finite element software MIDAS/GTS is used to build the two-dimensional mo dels. Different construction methods and actual construction method (two-side wall drift heading multistep method) are built to dynamically simulate the deformation of the surrounding rock and the overlaying high-voltage tower.4. The finite element software MIDAS/GTS is used to build the three-dimensional models with the two-side wall drift heading multistep method, the characteristics and laws of the surface deformation and the surface foundations of the tower are gotten on the bias state.The results were compared with the on-site monitoring datas in order to get a wider laws of implications,the conclusions are as follows:(1)The nephogram of the three-dimensional simulation in the section of the construction process and two-dimensional simulation have the laws of similitude. And in the same calculate conditions, the three-dimensional simulation of deformation is less than the deformation of the two-dimensional simulation, which is much closer to the actual deformation. The two-dimensional simulation showed that the surface settlement curve is a normal distribution curve.The land settlement tends to 0 in the far distance of the axi of the tunnel. Although the tunnel is under the bias state, the settlement curve is basically consistent with Peck settlement curve. Horizontal displacement curve is approximate to a sinusoidal curve.The horizontal displacement of the position of the near aix is approximate to O. The horizontal displacement of the right side surface of the axi tends to left,and the displacement increases within a certain distance to a far distance tends to 0. Two-dimensional simulation results have the similar laws with the three-dimensional simulation.(2) The three-dimensional models are build to simulate the construction of the tunnel on the actual complex conditions of stratums,the construction of the tunnel greatly affects the land subsidence and upthrust. The land subsidence of the section of the tower is large when the construction of the tunnel beneath the tower,but the land subsidence occurred mainly after the section excavation.(3) Comparing Y=35m section (section of the overlaying high-voltage tower) subsidence curve with Y=90m Section (exit section) subsidence curve shows that Y=35m section subsidence curve is approximate to normal distribution curve,at which two-dimensional simulation of the section of the overlaying high-voltage tower are similar.Y=0m section subsidence curve is approximate to'W'-shaped curve.The main reason is the influence of the depth.The Y=0m section is at shallow depth, the subsidence curve is similar to the subsidence curve of two single tunnels superposed.TheY= 35m section is at relatively deep depth, the subsidence curve is similar to the subsidence curve of a single tunnel that the radius is slightly larger than the single tunnel's. This is basically consistent with Peck settlement Theory.(4) Through the deformation curves of the Y=35m section (section of the overlaying high-voltage tower) shows that the deformation curves of the foundation surface of the tower is approximate to linear distribution.The closer to the tunnel, the greater the land settlement. The horizontal displacement curves of the foundation surface of the tower approximate straight line, the horizontal displacement of the tower is fairly close. The results have the similar conclusions with the two-dimensional simulation of the section of the overlaying high-voltage tower...
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