Study On Settlement Control Technology Of Ultra-Small Radius Curved Shield Tunneling Through Antique Buildings In Water-Rich Fine Sand Stratum

In the construction of ultra small radius curved shield tunnel,continuous deviation correction is required,and the overdigging inside the curve is large,and the thrust pressure is quite different from that of straight or large radius tunnels.The disturbance law of construction parameters on antique buildings and the ground surface in the construction of ultra small radius curved shield tunnel need to be further studied.At present,the relevant regulations and research rarely pay attention to the safety control of antique buildings in shield tunnel construction.The mechanical properties and stability of the fine sand stratum are poor,and the construction is difficult.Based on the above considerations,in order to protect the safety of the antique building on the ground during the construction of the ultra small radius curved shield tunnel with 200 m in the water-rich fine sand stratum,this thesis,based on the Taiyuan Metro Line 1-2connection line project,starts from the aspects of synchronous grouting,settlement control standard of antique building,uneven settlement law,reinforcement measures,etc.and the research contents and results are as follows:（1）The consistency,stone rate,compressive strength and other grout ratio tests were carried out by the double slurry scheme combined with the admixture.The single factor method for determining the admixture,according to the characteristics of the admixture,defined the admixture in water glass and melt fusion into the segment gap method.Orthogonal testing was used to determine the ratio of the new composite group suitable for the water-rich fine sand stratum.Compared with the traditional grout,the initial setting time of the new grout was reduced by 23.14%,the consistency was reduced by 22.18%,the stone rate was 99.40%,the water dispersion resistance was better,and the gel time was controllable.Through unconfined compression tests,the mechanical properties of the composite group and the change of stress-strain relationship with time were obtained.（2）According to the disturbance range of the shield tunnel construction on the stratum,the relative position of the tunnel and the antique building and the importance of the building,Yingzege is determined as the key protection object.Based on the structural characteristics and damaged forms of Yingze pavilion,the evaluation criteria are determined.Based on Peck formula,the maximum settlement of the building was determined by 11.29 mm,and the early warning value and alarm value of the building settlement were established.The standard value of the differential settlement of the building was 0.10%,and the safety control standard of the antique building determined.（3）Finite difference software FLAC^3D was used to establish a three-dimensional numerical model to analyze the non-uniform settlement law of an ultra-small radius curved shield tunnel under the building.The selection range of key construction parameters was determined,and reasonable construction parameters were determined according to the influence law of construction parameters on the settlement of the surface and the building combined with the laboratory test:soil tank pressure of 200k Pa,grouting pressure of 0.25 MPa,elastic modulus of the slurry consolidation body of400 MPa,and applied in the subsequent relevant numerical simulation research.（4）Guijuxuan,a building directly above the tunnel,and Yingzege,a building outside the tunnel,were selected for simulation analysis according to the location and importance of the buildings.During shield construction,Guijuxuan is inclined to the inner side of the tunnel,and the maximum settlement is located inside the tunnel curve.Yingze Pavilion is generally inclined to the tunnel side,away from the slightly elevated tunnel side.The differential settlement of bearing columns in the construction process is analyzed.When the shield is excavated near the building,the differential settlement of bearing columns increases sharply and slows down after it is far away.The maximum differential settlement occurs in the bearing column perpendicular to Yingzege’s excavation direction and close to the tunnel,and the differential settlement is 0.099%,which should be paid special attention to.（5）Take deep hole grouting reinforcement measures for Guijuxuan;Active protective measures should be taken to strengthen Yingzege by deep hole grouting combined with isolation pile.The effect of reinforcement measures on uneven settlement was analyzed by numerical simulation.By analyzing the field monitoring data and comparing it with the numerical simulation results,it is concluded that the maximum settlement of the building obtained from the numerical simulation is slightly larger than that obtained from the field monitoring data,but both meet the relevant control standards.