| As a commonly used tunnel construction technology,subway shield tunnels are widely used in urban subway construction,but in the process of shield tunnel construction,ground settlement will inevitably occur due to the destruction of the soil stress state.The water-rich and weak stratum has large water content,low soil strength and is easily disturbed and deformed.If the settlement is not properly controlled,it will affect the road surface and surrounding buildings and cause a significant impact on life and property.Therefore,this article takes the example of shield tunnel project in the section between Shuangta Xijie and Dananmen of Taiyuan Metro Line 2 as the background,based on the basic mechanism of settlement,the measured data is used to fit the Peck settlement formula and the method of numerical simulation to analyze the surface settlement law during shield construction As well as the impact of soil disturbance,for the analysis of the tunnel surface settlement during the synchronous grouting process during the construction process,the reasonable settlement control measures for the water-rich and weak stratum in Taiyuan area are proposed.The main research contents and research results are as follows:(1)Introduce the shield construction and the working principle of the earth pressure balance shield machine,analyze the principle of shield construction on soil disturbance,explain the influencing factors of ground settlement,analyze the time and space effects of ground settlement,and lay the foundation for subsequent research Theoretical basis.(2)Introduce the specific engineering geological conditions of Shuangta Xijie ～ Dananmen of Taiyuan Metro Line 2,select the representative site 5horizontal tunnel surface subsidence measured data to carry out linear regression fitting.Establish a direct connection between the measured data and the Peck formula to quantitatively analyze the maximum settlement of the ground and the coefficient of sink width i.After regression,the Peck formula can play a role in predicting the surface settlement of the same or similar water-rich and weak stratum.(3)The numerical simulation software was used to simulate the shield excavation of the Taiyuan water-rich and weak stratum,and the vertical stressand vertical direction of the soil surrounding the excavation of the 4,8,12,16 th and 20 th ring shield machines were analyzed Displacement and plastic zone change rules and draw horizontal and axial ground settlement curves along the tunnel under different excavation rings.After the tunnel with Y = 0 cross-section is penetrated,the comparison between the tunnel surface subsidence curve and the engineering fitting curve is basically consistent,and the practicality of the numerical simulation method for predicting and analyzing the ground settlement during the excavation of the shield tunnel is verified.(4)Research on the influence of control measures synchronous grouting on surface settlement.The power law-type slurry diffusion pressure annular distribution model and calculation formula are derived theoretically.It is the horizontal and axial settlement changes along the tunnel surface under the four schemes of 1,0.9,0.8 and 0.6.The thickness of the equivalent layer is used to simulate the grouting volume,and the effects of the thickness of the equivalent layer of 12.8,14.4,16,19.2,22.4 cm,and 25.6 cm on the lateral and axial settlement of the ground along the tunnel surface are analyzed.Preliminary reveals the effect of grouting volume on surface settlement in Taiyuan water-rich and weak stratum.(5)Combined with the analysis of the effect of synchronous grouting on ground settlement,reasonable control measures for grouting factors and corresponding grouting schemes are proposed,and reasonable settlement control methods for construction factors are also proposed.It can be used as a reference for shield construction in the same or similar geological conditions. |
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