| With the rapid development of China's urbanization process,the pressure of urban ground transportation is becoming more and more serious.Subway construction is an important means to effectively alleviate the pressure of ground transportation.However,the intricate aboveground and underground structures in urban areas have caused many inconveniences to the design of subway straight lines.The application of small radius curve tunnel provides a direction for solving this problem.The construction of small-radius curved shields is different from that of straight shields.It is affected by factors such as turning correction of the curved section,overcutting of the cutter head,posture adjustment of the shield machine,and unbalanced thrust of the jack.The deformation law is quite different,so it is of great significance to study the influence law of small radius curve shield construction on the surrounding soil displacement.In this paper,based on the summary of previous studies,combined with actual engineering,comprehensively using on-site measurement,theoretical analysis and numerical simulation,this paper studied the influence law of the shield construction of small and medium radius curves on the clay soil layer in Zhengzhou on the displacement of surrounding soil,mainly The research content and conclusions are as follows:(1)The on-site measurement is used to analyze the change law of the surrounding soil displacement caused by the construction of the small radius curve shield.The construction of a small radius curve shield will cause the maximum position of the lateral surface settlement to shift to the inside of the curve,and the surface settlement groove is asymmetric;as the turning of the shield machine has an squeezing effect on the outer soil,the outer side of the curve is closer to the tunnel.The settlement of the layer is small,even causing uplift;unlike the straight shield tunnel,the horizontal displacement deformation curves of the left and right sides of the curved tunnel are asymmetric,and the soil outside the curve is squeezed by the shield shell and moves away from the tunnel.The soil is unloaded due to over-excavation of the cutter head,and the displacement is towards the direction of the tunnel.(2)Based on the inverse displacement algorithm,comprehensively considering the factors such as lining stiffness reduction,tunnel curvature radius,grouting layer solidification process,jack unbalanced thrust,etc.,the whole process of small radius curve shield construction is simulated and compared with the measured data to verify Its reliability.(3)Based on the single factor analysis method,study the influence of different curvature radius,jack unbalanced thrust and grouting pressure on the soil displacement around the tunnel.In the range of 250-500 m radius of curvature,the maximum surface settlement and its offset increase with the decrease of the radius of curvature;in the range of 1 to 2.5 times the jack thrust ratio on the left and right,the maximum surface settlement and its offset It is positively correlated with the increase of thrust ratio;the increase of grouting pressure has a significant effect on the suppression of surface settlement.The grouting pressure increases from 0.10 Mpa to 0.25 Mpa,and the maximum surface settlement decreases by about 30%.(4)Comparing the prediction results of the modified Peck formula with numerical simulation and on-site monitoring data,it shows that it has good applicability in the construction of curved shields and the calculation results are more accurate.(5)Based on the engineering experience and research results of this paper,control measures for the construction of shields with small radius curves are proposed,in order to play a guiding role in the design and construction of similar projects. |
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