Full Recyclable And Prefabricated Shafts Supported By A Resilient Support System And Engineering Application

Due to the acceleration of underground space development,the application demand of underground shaft is more and more urgent.Especially in the high-density area of the city,the construction of shafts faces the problem of limited space and strict control of deformation and environmental.The traditional reinforced concrete support technology can no longer meet the construction needs of urban dense areas.The theoretical analysis,numerical simulation and field test were adopted to study the full recyclable and prefabricated shafts supported by a resilient support system in this paper.The main results are as follows:(1)The design concept of resilient support was presented on the basis of summarizing the shortcomings of the available technology,and the urban shaft retained by a full recyclable and prefabricated support system(RPRS)was established.The RPRS is optimized from the aspects of structural plane shape,structural materials selection,component segmentation and node connection.Finally,the design method of RPRS was formed.(2)Based on the analysis of RPRS mechanics characteristic and bearing mechanism,the mechanical calculation model of the prefabricated resilient support structure is established.The internal force distribution characteristics and structural system stability of different support plane shapes are obtained.The design calculation theory of RPRS is established.This study provides a theoretical basis for the selection of structural design parameters.(3)The life cycle construction technology of the RPRS was formed.The key construction process of RPRS applied to the shield cutterhead maintenance is proposed.Comparing applicability of the advanced hole method and the backward hole method.The life cycle construction risk of RPRS was identified.The risk prediction method and control measures were put forward,and an intelligent risk monitoring and early warning system was established.(4)The influencing factors of stratum deformation during the whole process of shaft excavation,shield tunneling and cutterhead maintenance were studied by FLAC3 D.The support structure response of shaft under the influence of shield tunneling was also analyzed.The technical requirements of key construction parameters such as shaft excavation interval,support timing,shield support pressure and strata improvement were proposed,which provides reference for the deformation and construction risk control.(5)Based on the requirements of the shield cutterhead maintenance of Beijing New Airport Line,the field test and engineering application research of RPRS was carried out.The results show that the surface settlement was less than 15 mm in the whole process,and it is mainly induced by shield tunneling.The proportion of settlement caused by shaft excavation and backfilling was less than 20%.This technology can effectively control strata deformation to meet the construction needs of urban highdensity areas.The support system has a reasonable force system,fast construction speed,and it is economical,environmental and recyclable.