| The scale of urban subway is becoming larger and larger,and the construction technology of urban tunnel is becoming more and more mature,but it does not completely eliminate the impact on the strata and surrounding environment during tunnel boring.Ensuring the safety of the tunnel and the surrounding building structures during construction is a key aspect of tunnel construction.Tunnels form a synergistic system with the surrounding strata and building structures during construction.The disturbances caused by tunnel construction propagate through the strata to the buildings and cause deformation,cracking,and even structural damage to the building structures.How to quickly and effectively predict the tunnel disturbance to the surrounding environment during tunnel construction has become a key element of urban tunnel research today.This paper takes the synergistic system of tunnel-strata-buildings as the research object,and adopts the research methods of literature research,theoretical analysis,and numerical simulation to conduct a systematic research on the three-dimensional stratigraphic response caused by urban tunnel construction,the mechanical response of buildings caused by tunnel underpass construction,the damage of building structures caused by tunnel underpass construction,and the control methods of building response under the influence of tunnel construction,and has achieved the following results.(1)A deformation prediction method for three-dimensional strata under the influence of tunnel construction is established.On the basis of the soil movement model,the boundary conditions of the vertical deformation influence zone of the strata and the composite stratigraphic condition of the strata are modified to derive the analytical solution of the two-dimensional stratum deformation.After that,the two-dimensional stratigraphic deformation formula is extended to three-dimensional form by using spatial deformation factor.The ground settlement and lateral deformation characteristics of three-dimensional strata in different horizontal and vertical planes are studied.The influence of typical factors on the ground deformation during the tunnel excavation was analyzed by the controlled variable method,and the main conclusions were: the transverse surface settlement caused by tunnel excavation had larger values in H/tan(45°+ φ/2)+R range on both sides of the tunnel axis,and the longitudinal surface settlement varied more in ±H range.The maximum lateral horizontal displacement always occurs near the tunnel camber line,independent of the variation of the typical factors.(2)A method for predicting the mechanical response of buildings under the influence of tunnel underpass construction is proposed.Using a two-stage analysis method,the equation for the mechanical response of shallow foundation buildings caused by the tunnel boring process is derived by combining the three-dimensional ground deformation equation in this paper.The method can consider the angle between the tunnel axis and the building axis as well as the tunnel boring process.The deformation and internal force response of the building structure during the tunnel construction process can be calculated.Using the building settlement data of Hangzhou Metro Line 1 passing through a plant and the building settlement data of the numerical model,the effectiveness of the building mechanical response prediction formula in this paper is verified.The deformation response characteristics of the building at different relative positions of the tunnel and the building structure are also studied based on the building structure response equation in this paper.(3)A process for predicting building damage during tunnel construction was established and building damage characteristics were analyzed.Based on the calculation method of ultimate tensile strain and the deformation prediction formula of stratum and building deduced in this paper,the damage prediction process of building under the influence of tunnel construction is established.The validity of the building damage prediction procedure in this chapter was verified using the damage monitoring data of the surrounding buildings during the construction of Ramsgate Harbour Tunnel and Sofia Railway Tunnel.It was found that the ultimate tensile curve with a stiffness ratio of 2.6 was always above the ultimate tensile curve with a stiffness ratio of 12.5,and the ultimate tensile curve with a long side b of 10 m was also always greater than the ultimate tensile curve with b of 100 m.This indicates that frame structures are less prone to cracking than masonry buildings under the working conditions in this paper,and slender buildings are also less prone to cracking.At the same time,the damage characteristics of buildings are studied combined with an example,the variation law of main tensile strain and the relationship between main tensile strain and cracks during tunnel excavation are analyzed,which shows the rationality of using main tensile strain in building damage assessment.(4)The control method of building response during tunnel underpass construction is studied.The control effect of horizontal grouting reinforcement on the mechanical response of the building was studied by using numerical simulation method,and the change law of the ground and building response was investigated by changing the parameters of the horizontal grouting reinforcement layer in the numerical model.The calculation method of the control efficiency of horizontal grouting reinforcement on building settlement and main tensile strain is proposed,which is a comprehensive representation of the control effect on the building mechanical response.It is found that the control efficiency increases gradually with the increase of the thickness and elastic modulus of the grouting reinforcement layer,and the distance between the reinforcement layer and the tunnel has little effect on the control efficiency.Finally,considering the economy and effectiveness of grouting reinforcement,a method to determine the optimal parameters of horizontal grouting reinforcement is proposed. |
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