| Most of Metro tunnel projects are in medium and large cities,where there are many buildings,the construction environment of Metro is very complex and requires high technology,and the construction face is almost underground.Most of them adopt shield method to excavate the tunnel.In the process of subway construction,the continuous excavation of shield machine will disturb the ground and cause ground deformation and surface settlement.Excessive settlement will not only affect the construction progress,it will also cause damage to nearby buildings,traffic roads and underground pipelines.It is of great value for similar metro projects to study how to reduce the disturbance of Metro tunnel construction to surrounding rock and soil,stabilize stratum and reduce surface subsidence.Based on the theory of void transfer in sand-cobble stratum and the related action of shield tunneling in rock and soil mass,this paper studies the main factors of shield tunneling in Metro tunnel and its influence on ground settlement.In this paper,the constitutive model of subway tunnel excavation in the Wanshou Temple-national book section of Beijing Rail Transit Line 16 is established by means of computer numerical simulation,and the model is calculated by FLAC3 D finite difference program,the deformation of surrounding rock and soil mass of tunnel under the influence of different thickness of overburden soil,different grouting strength and different driving pressure is studied,provide reliable experience for similar engineering construction.This paper studies from the following four aspects:1)Through collecting a great deal of measured data and reading relevant documents,the basic working principle and main construction technology of shield machine are expounded in detail,and the causes and deformation mechanism of ground surface settlement caused by tunnel shield construction are expounded according to the deformation theory of sand-pebble special stratum,and the main influencing factors of ground deformation are summarized based on a lot of engineering experience.2)To collate and analyze the hydrogeological conditions and surface monitoring settlement data of the Wanshou Temple-national Library section of Beijing Rail Transit Line 16.Using the collected monitoring data,the Peck formula is regressed.By using the measured settlement data of Engineering Section and Peck formula after regression,the data are compared and analyzed.3)Based on the study of the shield section of the Wanshou Temple National Library Station of Beijing Rail Transit Line 16,using FLAC3 D finite difference software to define the parameters which are difficult to be quantified as the equivalent layers of the same nature,the three-dimensional model of the computer simulation test is established according to the hydrogeological report of the field engineering exploration.According to the construction procedure of shield method in actual project design,the simulation test is carried out on the computer according to the same construction merits to study the influence of shield method construction on the stratum and the law of ground surface settlement.Finally,the results of numerical simulation are compared with the results of actual project monitoring to verify the rationality of the numerical simulation test.4)The numerical simulation program is used to simulate the characteristics of the surface settlement curve under different parameters.The characteristics of ground settlement curve caused by shield excavation of Metro tunnel under different thickness of overburden soil,different driving pressure and different grouting strength are compared to explore the influence of each factor on ground settlement.According to each influence factor proposed the science reasonable effective solution measure provides the certain reference for the similar project.The paper is based on the project "study on settlement and Deformation Law of surrounding rock and soil mass of Metro Shield tunnel"(00104520190028).There are 44 figures,9 tables and 58 references in this paper. |
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