The Mechanism Research Of Distributed Optical Fiber Monitoring For The Deformation Of Frozen Wall

The freezing pipe of the freezing engineering site practical use was Selected, combined use the point type monitoring technology and the BOTDA monitoring technology, the freezing pipe mechanical properties test was take. The results showed that under the vertical concentrated loads, in the length direction of the tube along the central deflection of freezing pipes generally shows a bilaterally symmetrical distribution trend, the deflection of both ends were small, and the center part was large. The maximum deflection of BOTDA monitoring method is about1.6mm, and the maximum deflection of point type method is2.4mm; the stress curve and the deflection curve of the pipe have the same change tendency, middle big and end small. In the last stage of loading, the tube central strain reaches the maximum value, under BOTDA monitoring method the value is about691με, strain gauge value is736με, a difference of about45με, the results of two methods were close to each other.The on-site monitoring using BOTDR monitoring technology, experimental results show that with the increase of the depth of excavation, the radial deformation of the frozen wall was also gradually increased, the upper position of high deformation value is small, and the segment the lower position deformation value is large. When the depth of excavation was2.7m, the deformation of frozen wall in the tunneling process of value is not very high, only part of the deformation value were more than50mm, the maximum value was about110mm. When the depth of excavation was4.0m, the displacement value of frozen wall is bigger than the depth of excavation was2.7m, most displacement value were more than the allowable value50mm, the maximum value can be reached230mm.It can be concluded from the results of the numerical simulation, the deformation of freezing wall is mainly concentrated in the middle part of the excavation section.The maximum horizontal total displacement of freezing wall can reach80mm, The maximum horizontal displacement of frozen wall is in accord with the high1/3of the excavation section.