Settlement Analysis And Settlement Control Treatment Of Large Deep Buried Immerse Tunnel

In conventional understanding,immersed tube tunnels mainly consider structural anti-floating problems,and problems such as settlement and foundation bearing capacity are not prominent.However,monitoring data of many immersed tube tunnels in recent years show that actual measured values of settlement during operation period are far greater than theoretical predictions,while tunnel structure cracks.Diseases such as leakage and seepage are closely related to excessive settlement;excessive absolute settlement and longitudinal uneven settlement will cause damage to the structure and joints of the pipe joints that exceed the allowable values.Especially in recent years,the immersed long-earth immersed tunnel tunnel project has gradually increased,its upper silting load is large,and the weak foundation of the lower foundation has increased people’s attention to the settlement problem.How to reasonably calculate the predicted structural settlement,formulate reasonable control standards for settlement,adopt effective measures to control the settlement of structures,and avoid tunnel diseases,have become problems that need to be carefully studied and solved in the construction of immersed tunnels.In the preliminary design stage of the submarine immersed tunnel at the Hong Kong-Zhuhai-Macao Bridge,a longitudinal foundation design plan for the supporting pile-sinking-piling-paving method was put forward.The design stage of the construction plan was optimized as a rigid pile composite foundation-high pressure jet grouting pile.-Compact foundation pile composite foundation-block stone vibration +gravel cushion natural foundation foundation program.No matter what kind of scheme,it is necessary to solve the problems of settlement control and stiffness transition along the longitudinal direction of the mixed foundation.To solve the above problems,it is necessary to first determine the control standard for subsidence from the joints of immersed tube tunnels,determine the basic subsidence control standards,and grasp the maximum absolute subsidence and maximum uneven subsidence that are acceptable to the foundation.This is the basis for the basic type selection and settlement analysis calculation.The goal.This paper analyzes the mechanism of settlement and the influencing factors of settlement in immersed tube tunnels,studies the index of joint shear force and the amount of joint opening settlement control,and proposes analysis methods of the load influencing line and stiffness influence line of joint shearing force,and establishes a system based on the structural system.The longitudinal differential settlement control standard simplifies the calculation formula and determines the total settlement and longitudinal differential settlement control standards for different foundation schemes.The subsidence of the immersed tube is mainly composed of three parts:the compression of the foundation cushion,the recompression settlement of the soil,and the secondary consolidation.The rebound recompression settlement of soil is the most important part of the total settlement.The settlement of this part is the core of the accurate analysis of settlement.Based on JANBU tangent modulus method,this paper analyzes the basic rebound recompression calculation method,analyzes the calculation formula of the method,and analyzes the calculation parameter determination method based on indoor test and high-precision in-situ CPTU test.The method for calculating the settling settlement and the method for numerical simulation are compared and verified.The method for determining the settlement calculation parameters of the numerical simulation method is given.The foundation design of the Hong Kong-Zhuhai-Macao immersed tunnel adopted the first paving of gravel cushions.There are few engineering cases for this foundation project,especially the piles of piles are set between the pile caps and the immersed pipes.Cushion and gravel cushion have little practical engineering experience as force transmission structure between pile foundation and immersed tube structure;in addition,the mechanism and theoretical analysis of the force transfer of pile foundation using gravel cushion are rare,and at the same time the immersed tunnel is broken.There are many uncertainties that need to be analyzed when the stone cushion and pile foundation are operating in the water,such as mud silt,flatness,inclination,eccentricity,and weak underlying stratum.In this paper,the physical and mechanical properties of rockfill ditch under different working conditions were studied through the physical model test of gravel cushion.The deformation and deformation characteristics of gravel cushion and pile foundation when operating in water were analyzed.The calculation parameters of reasonable gradation and compression modulus of gravel were determined,and the ultimate bearing capacity of gravel was analyzed to provide parameter basis for the calculation of gravel layer settlement and to determine the rationality of gravel cushion for deep buried large load immersed tunnel.Based on the calculation and analysis of the natural foundation settlement of the full-line tunnel,this paper studies the foundation stiffness variation mode of the immersed tunnel,proposes the control principles and common control techniques for the transition of the mixed foundation stiffness,and analyzes the influencing factors,basic principles and specific procedures of the foundation selection based on the SWOT analysis.Investigate settlement calculation methods for settlement control technology of composite foundations such as compacted sand piles,PHC piles,high pressure jet grouting piles,and gravel piles.The immersed tube tunnel needs to carry out relatively complete immersed tube settlement observation during the construction period and the operation period,so as to objectively grasp the settlement development of the tube section,grasp the deformation and stability of the immersed tube tunnel foundation,and predict the future settlement development.Potentially unacceptable risks are raised for early warning so that all parties can take measures in advance to avoid accidents.The paper combined with on-site settlement monitoring,statistical analysis of monitoring data,using the hyperbolic method to calculate the final settlement and the current degree of consolidation,and compared with the theoretical calculation of settlement to obtain the measured and theoretically calculated settlement ratio η for each soil layer.The settlement calculation formula is revised.In general,the paper calculated the settlement control standards,the mechanism of settlement generation,the high accuracy of the soil mechanics parameters,the calculation method of the soil re-compression settlement,the study of the mechanical properties of the gravel cushion,the settlement control measures and the calculation of the site settlement to the theoretical calculation.In the revision and other aspects,a systematic study was made on the settlement analysis and settlement control of deep-buried immersed tunnels.The research results have been successfully applied in the immersed tunnels in Hong Kong-Zhuhai-Macao,The research results have good theoretical and practical value.For the construction of similar immersed tube tunnels in the future has a good guiding significance.