Abstract：Research purposes: It is the first time for China to construct tunnel in karst strata with shield method. In the course of shield tunnelling, shield machine probably fall down and the tunnel structure is probably damaged because of losing much water, collapse and bad differential settlements of strata. The deep researches are done on three fields, namely distribution , sizes and filling of karst caves，treatment of karst caves and technical measures for shield tunnelling for the purposes of making fine design and construction and guaranteeing the safety of construction and operation.
Research methods : The analysis is made for karst strata by adopting many integrated survey ways and the construction program is optimised through making comparison of the programs according to the characteristics of shield machine and shield construction.
Research results : The successful construction of shield tunnel in karat strata verified the feasibility of the survey and reinforcement programs，which fills the blank in China.
Research conclusions: It is an effective way to detect the distribution of karat caves by adopting integrated survey method. All of the strata reinforcing program made with the characteristics of shield construction, the innovation of shield machine and the technical measures taken for tunnelling are suitable.
2007, Vol. 24 
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