Research On Deformation Monitoring Technology Of Anti-slide Pile Based On BOTDA

With the rapid development of the western expressway,a large number of large-scale and large-scale engineering landslides have been induced in the mountainous areas due to the high fill and deep excavation.The difficulty and cost of project management have been increasing year by year.Traditional single or multi-row pile walls can not meet the requirements of many engineering deformations and stability requirements,h-shaped pile wall is proposed due to its spatial structure.Taking the h-shaped pile wall of a large-scale expressway in Guizhou Province as an example,this paper adopts the traditional deep inclinometer,advanced BOTDA monitoring technology,simulation and mechanical theory analysis and other methods combined with engineering examples of h-type anti-slide pile stress analysis to gain a better understanding of the stress-strain and internal force distribution in landslide control.The main achievements are as follows:(1)In this paper,the principle of distributed optical fiber testing technology is briefly introduced and the monitoring system of h-type pile wall is established.Combining the advanced BOTDA optical fiber testing technology and the traditional deep displacement method,h-type anti-slide pile is used in the whole process of landslide control of the deformation test,through the displacement and strain feedback,that h-pile wall in the treatment of extra large landslide effect is significant.(2)By using the optical fiber testing technology to monitor the strain of the rear pile of h-type pile wall,the calculation model of landslide thrust on the back row pile is put forward by using the mechanical theory to calculate the bending moment and shear force.It is used to determine the landslide thrust size and there are great differences between its distribution form and the calculation results and the commonly used forms.(3)The method of calculating bending moment,shearing force and axial stress through fiber-optic strain monitoring is proposed.According to the code of reinforced concrete material,the relationship between strain and stress,the calculation theory of flexural members and so on,it analyzes and evaluates the working status of the pile wall by using the calculation of internal force of pile body carried out by contrasting the internal force of pile body and conducting a comparison between the the calculated axial force of pile wall and the strength standard of reinforced concrete.(4)The finite element software FLAC3D is used to establish the numerical calculation model to optimize the design of the h-shaped pile wall.By analyzing the different length of the tie beam,the anchoring depth of the front and rear row piles,the relative stiffness of the tie beam and the length of the cantilever section,the influence of wall on the optimal design of h-shaped pile wall is put forward.The optimal design of h-shaped pile wall is that the length of tie-beam is 2-3 times the pile width and the stiffness is 2.5 times El.The anchorage depth of the front and rear piles is 1/3 and 1/3.3 of the length of the corresponding pile,and the length of the cantilever section is 1/4 of the length of the pile.