大断面海底隧道CRD法绝对位移控制基准建立及应用研究

Study of absolute deformation control criterion and its application for large section subsea tunnel with "CRD" method

隧道位移控制基准的建立是确保隧道安全施工的一项重要内容。以厦门-翔安海底隧道陆域浅埋暗挖段CRD法施工为工程背景,陆域浅埋段总长约2525m,主要穿越全、强风化花岗岩地带,含水率高、自稳能力差。依据全站仪非接触量测获得初期支护三维绝对位移分布规律,确定三维绝对位移基准控制指标,同时对86个围岩位移监测断面的监测数据进行变形正常断面和变形异常或险情断面的位移量统计分析,最终确定CRD法(center cross diaphragm method,交叉中隔壁法)三维绝对位移控制基准。研究结果表明,将CRD1、CRD3部拱顶竖直位移和上中隔墙、下中隔墙水平位移作为CRD法位移控制指标;CRD1部和CRD3部拱顶下沉极限位移分别为200mm和130mm;CRD3部拱顶竖直位移约为CRD1部的0.5～1倍;上中隔墙水平极限位移约为100mm,下中隔墙水平极限位移约为15mm。通过现场97个断面应用,共发现58次异常和险情,由于发现及时,处置有力,保证了施工安全。

It is an important content for construction safety in tunnel to establish the deformation criterion.The land shallow-depth-excavation area of the Xiamen subsea tunnel was constructed by CRD method,its total length is 2 525 m and which holds higher water content and lower intensity.The indices about three-dimensional absolute displacement criterion of primary support are put forward according to the distribution rules of three-dimensional displacement by non-contact three dimensional deformation monitoring with total station.In addition,three dimensional absolute displacement criterion was put forward finally by analysis of normal displacement and abnormal or dangerous displacement about eighty six measurement sections.The study results indicate that the deformation indices of tunnel construction with CRD method are vertical displacement of arch crown on CRD1,3 and horizontal displacement of middle wall.The ultimate vertical displacement of arch crown on CRD1,3 is 200 mm,130 mm and the deformation of CRD3,1 is in proportion as 0.5-1.0.The ultimate horizontal displacement of middle wall between CRD1 and CRD3 is 100 mm while it is 15mm between CRD2 and CRD4.Fifty eight abnormal and dangerous things were found by applying this criterion to ninety seven sections in scene and ensure construction safety because of adopting some measures in time.