The Influence Of Subway Shield Construction On Adjacent Ancient Buildings

In recent years,with the continuous deepening of China’s economic system reform,the pace of urbanization has become faster and faster,hence the land resource is becoming more insufficient.Thus,the backward urban plan can not meet the travel needs of contemporary people already.In the coastal areas and the better developed areas of the central and western regions in China,urban subway track projects are all being under active construction to develop underground space to meet the growing travel demand of the city.At present,the most commonly used construction method in the construction of urban subways for underground excavation is the shield method which has the advant.ages of me.chanization,safety and high speed,which has been widely used.Meanwhile it is inevitable for the subway shield construction to influence the surrounding.Therefore,the relevant impact research of subway tunnel shield construction is of great significance.This paper takes the Xi’an subway engineering standard section that is under the ancient building as the research object,studying several influencing factors of the surface settlement phenomenon caused by the construction process,and researches the pattern of surface settlement caused by tunnel construction,as a result the related reasons of surface settlement caused by shield construction are summarized.Due to the geological environment and the particularity of the cultural environment of Xi’an,this paper analyzes the stratigraphic disturbance and the corresponding stratum displacement and surface settlement caused by tunnel shield construction from Xi’an’s geological point of view.With relevant survey data,the large-scale finite ele:ment general software ABAQUS was used to simulate the construction process of the section passing through the north gate wall of Xi’an Metro Line 2 after the actual reinforcement The main research results are as follows:(1)The settlement curve is obtained by the simulation calculation results,which shows that the disturbance of the soil is diffusive,and the degree of disturbance is attenuated with the increase of the distance between the soil and the tunnel.At the same time,the main increase of the surface settling trough is within the range of 20 meters before and after the shield passing section,which accounts for about 75%to 90%of the total settlement.(2)The left and right asymmetry of the tunnel axis leads to the settlement of the left side being 5%to 9%larger than the right side due to the influence of the city.Because of the reinforcement measures,there is no big difference between the maximum settlement of the second and third sections and the values of the first section in the inner and outer edges of the wall.For the displacement of the longitudinal stratum,the settlement effect of the stratum gradually increases with the advancement of the shield,where the maximum settlement occurs within about 5 meters of the top of the tunnel lining.Because the central part of the axis is affected by the wall of the ground structure,the displacement of the stratum is large relatively,but it is obviously reduced owing to the reinforcement measures.At the same time,the vertical surface settlement is not uniform,which the settlement under the city wall is about 1.7 times larger than the surface settlement 20 meters away from the city wall.(3)Special reinforcement methods for the city wall and surrounding strata have been carried out within this proj ect section,and the calculation results also verify the rationality and necessity of the scheme.