In-situ measurement and analysis of drilling shaft lining concrete strain during sinking

Abstract：The scheme based on the Fiber Bragg Grating（FBG） for measuring the concrete strains of the drilling shaft lining during sinking of Wenjiazhuang Iron Ore Mine auxiliary shaft was introduced,and the variation of the measured strains was discussed.The results show that the concrete bear compressive strain during drilling sinking,the tangent compressive strain is greater than the vertical and the strain variation phases is corresponding to the sinking phases.In the floating and dropping phase the strain curves presented ＂bilinear＂ feature and the measured value is in agreement with the calculated value of the derived formula;in the adding water phase the tangent compressive strains reduce while the vertical increase;in the first grouting phase the compressive strains reduce significantly,and some even become tensile.In the sequent three grouting phases the compressive strains increase first,then partially recover;in the drainage phase the tangent compressive strains increase and the vertical strains change a little;in the additional grouting phase the compressive strains increase first,then partially recover a less part as comparing to the preceding grouting.