Research On Surface Settlement And Tunneling Parameters Of Shield Construction In Complex Strata Based On Long-term Monitoring Data

With the rapid development of society,the urbanization process is accelerating and subways are under construction.At present,urban subway tunnels mainly use shield excavation method,which improves excavation efficiency and reduces surface settlement to a certain extent compared with traditional methods.In the section with complex ground conditions and many buildings on the surface,surface settlement control has higher requirements,so it is necessary to analyze the surface settlement law of complex ground and its influencing factors.Based on long-term construction monitoring data,this paper investigates the time series pattern of surface settlement and excavation data of shield construction in complex strata and its correlation,and based on this,interval estimation,hypothesis testing and ANOVA are conducted for typical engineering parameters therein,with the following main results and conclusions:(1)Based on long-term monitoring data,the measured surface settlement data of shield construction in complex strata are divided into two major categories and five subcategories according to their curve shapes,among which typical time series data contain three subcategories.The distribution of different types of curves on the geological longitudinal section map is stage-specific,and the complete typical time series curve goes through four stages of the general settlement law.(2)On this basis,the analysis of the relationship between the shield construction excavation parameters and its surface settlement was carried out,and the shield thrust was positively correlated with the soil bin pressure during the excavation process,with obvious changes in stages.By combining the changes of surface settlement before and after the passage of the palm face,it was found that the smaller the shield thrust was before the passage of the palm face,the larger the surface settlement was at the measurement points.(3)Based on the surface settlement monitoring data,parameter estimation and hypothesis testing were performed for the surface settlement of shield construction in complex strata.The mean value of granite surface settlement at the beginning of the interval is the largest,and the confidence interval at 99% confidence level is(-16.22,-13.54)mm.There is no significant difference in surface settlement between muddy siltstone and siltstone.(4)Based on the stratigraphic parameters and surface settlement monitoring data,oneway ANOVA was applied to test the influence of different stratigraphic layers,different rock envelope grades of granite and different weathering degrees on surface settlement under two monitoring types at the significance level α of 0.01,and the test statistics obtained were20.08,9.91 and 3.32,respectively.The results showed that the influence of stratigraphy and rock level on surface settlement was significant,and the influence of weathering degree on surface settlement was not significant.(5)The effects of stratigraphic parameters,surrounding rock grade and degree of weathering on shield thrust and the effect of shield thrust on surface settlement were further analyzed in conjunction with the tunneling parameters.The obtained statistical test statistics were 6.21,0.65 and 43.03,respectively,and all of them were greater than the critical values except for the test statistics of the weathering degree factor,which were less than the critical values.This indicates that the stratum and surrounding rock grade have a significant effect on shield thrust,the degree of weathering has no significant effect on shield thrust,and shield thrust has a significant effect on surface settlement.