Research On The Degree Of Compaction Of Segment In The Shield And Mine Method Combined With Construction

During urban subway tunnel construction,a combination of mining method and shield method is used for the soil and rock stratum with different rigidity.That is,supports are installed after mining method is employed in the preliminary stage,and then,shield gets through the empty tunnel and assembles the segments.Due to the particularity of the combination method,the assembly and compaction of the segment is a key procedure.That is,the procedure is key to forming a tunnel shape by design.It's also essential to water-proof function of the tunnel.All above explain everything about the practical significance and theoretical value of the degree of segments compaction and its control measures.The segments in transit line section from Wangjiawan to Zongguan station are adopted to conduct compaction degree and its control measures quality study.Details are as follows:(1)By means of theoretical computation and numerical simulation of the segments joints of subway tunnel.Bilinear stiffness model of segment joint is used to fit the curve of bending stiffness and angle of rotation.Theoretical analysis is conduct on the changing law of segment joints stiffness with the assistance of practical project to investigate the development process of the joints' mechanicals and deformation,thus the major factor which influence flexural rigidity most would be found,which are of guiding significance to the circumferential compaction degree of similar projects.(2)Study on the effects of non-uniform longitudinal thrust on the dislocation of the segments.Mechanics principle and mathematical method are used to calculate the longitudinal dislocation,which would accumulate since the non-uniform longitudinal thrust act on the segments when the distance between shield and segments grower larger.Eventually,the cumulant stay stable.Results has showed the distribution of longitudinal thrust have impact on the dislocation,which will be beneficial to the control of the longitudinal dislocation of the segment in construction.(3)The study on the impact of longitudinal thrust on compaction degree of segments by means of numerical simulation.The transfer law of longitudinal thrust ofthe segment has been obtained in four cases which shield tunneling machine is straight,downhill,uphill or making a turn.The farther away is the shield tail from the segment the smaller the thrust and the greater the slope(uphill slope is positive,straight slope is zero,downhill slope is negative)are,so the stress transfer farther away.Turning of shield is not conducive to the transmission of thrust,the greater thrust is the greater the rate of disintegration.Under the combined action of oblique thrust and water pressure,the relation between the deflection and maximum tension stress,different loads is analyzed.Results showed that deflection will increase then diminish as the distance between shield and segments increase,and the maximum tensile stress increases linearly with the increase of the thrust.The results,coupled with practical project,leads to arriving at the thrust and its transmission law which is up to the requirements of compaction degree.(4)Based on the results of the calculation and practical engineering project,the reasonable reaction facilities and the construction quality control measures which meet the degree of compaction requirements have been proposed,and it achieved satisfactory results.(5)Finally,acoustic detection method has been carried out to detect the degree of compaction.Detection data,numerical computation and theoretical analysis Through the comparison of the detection data,results of the numerical calculation and the theoretical analysis,the reasonableness of the thrust interval has been verified,which is of guiding significance for the thrust compaction measures of similar projects.