| With the rapid development of the city,the number of people pouring into the city has gradually increased,resulting in a multiplication of urban population.Although the huge population has contributed to the urban economic construction,it has also made the city very congested,which has brought difficulties to people's travel.In order to cope with such contradictions,the climax of building subways has been staged in major cities across the country.Since the construction of the subway needs to cross the central area of the city,and the urban construction environment is also very complicated,the subway shield construction often crosses the bridge pile foundation construction;because the shield construction will cause a large disturbance to the surrounding soil,the movement of the soil layer It will inevitably affect the nearby pile foundation,which will endanger the stability of the pile foundation.Therefore,it is of great practical significance to study the influence of subway shield construction on the stratum and adjacent pile foundation.This paper will take the construction example of the tunnel from Guangzhou South Railway Station to Baiyun Airport section of Guangfo Loop Line as the research background.According to the actual site geological exploration data,the threedimensional numerical model was established by using the finite element software ANSYS.The influence of shield construction on the stratum was studied.The influence of the change of construction factors on the surface was analyzed.The construction of the shield was studied.There is the influence of a single pile and the influence of the piles under the Dongxin Expressway.The main work and research results are as follows:(1)Through the establishment of a three-dimensional model of tunnel and soil,analyze the deformation of the tunnel and the surface of the tunnel;then change the construction conditions(digging surface size,tunnel depth,thrust of the face and grouting pressure)To study the variation law of shield construction on soil;the results show that the larger the size of the excavation surface,the wider the disturbance range of the soil,and the larger the width of the surface settlement trough,the larger the surface settlement will be;The deeper the burial,the wider the disturbance to the soil,and the width of the settlement trough will also increase,but the settlement value of the surface will decrease;the change of grouting pressure It has a great influence on the surface settlement.Effective control of the grouting pressure will reduce the impact of tunnel excavation on the ground surface.(2)The influence of shield excavation on existing single piles is studied,and the deformation characteristics of single piles during excavation are analyzed.The influence law of grouting pressure and thrust of the face on the pile foundation is analyzed by single factor control method.The results show that the change of the thrust of the face has a great influence on the longitudinal deformation of the pile,and the lateral deformation is not obvious;the change of grouting pressure The lateral deformation of the pile body is large and the longitudinal influence is small.(3)In accordance with the above research methods.With the example of the Guangfo ring line project,the cloud map and the node displacement change characteristics are adopted.The deformation characteristics of the stratum and the variation of the stress and displacement of the segment under the action of the pile group and the cap are analyzed.The influence of the shield construction on the pile group is further discussed,and the variation characteristics of pile group displacement during tunnel excavation are analyzed. |
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