Test Study Of Crack Propagation Law Of Anti-slide Pile By Model Test

As China has a vast territory,there are many natural slopes,With the development of various infrastructures,a large number of artificial slopes have been added.Therefore,the management of slope disasters cannot be delayed.Anti-slide piles are one of the most important retaining structures currently used to control slopes.Anti-sliding piles of cantilever beams are the most widely used anti-sliding piles.They are the earliest and most representative of anti-slide piles.Because the study of pile-soil relations,pile deformation,and internal force of pile body is not sufficient,the design of anti-slide piles is still based on the empirical formula.In the actual design of anti-slide piles,excessive reinforcement tends to be caused,which results in high cost and unnecessary waste.The crack propagation law in anti-slide piles is not only closely related to the deformation of the piles and the internal forces of the piles,but also contributes to subsequent maintenance.Therefore,it is one of the most important topics in the study of anti-slide piles to study the crack propagation law of anti-slide piles.This paper takes the anti-slide pile as the research object,and conducts the test research on the crack propagation.The main research contents are as follows:(1)According to the existing research results combined with field conditions,a test plan was designed and a model test device was made.The corresponding loading and monitoring scheme was designed for the model test.Three model piles were successfully tested according to the scheme,and the test data were recorded.The test data were compared and analyzed,and the process of crack propagation of anti-slide piles was summarized.(2)Introduced the calculation theory of crack width of reinforced concrete members,and analyzed the calculation formulas of the width of anti-slide piles of each standard,and found out the similarities and differences.Based on the data obtained from the test,the width of anti-slide piles was calculated and compared with the width of anti-slide piles obtained by the test and finite element software.(3)The combined model,bonding method and constitutive relation of steel and concrete in finite element software are introduced.Using ABAQUS to model the entireprocess from loading to failure,the fracture propagation characteristics of anti-slide piles were obtained by using the extended finite element method in ABAQUS to simulate cracks in anti-slide piles.Through the above work,we got the following conclusions(1)Anti-slide pile crack propagation lawThe crack change on the pile surface can be divided into three stages: In the first stage,there was no crack in the pile,the pile tensile stress is shared by steel and concrete,and piles also rebound during loading;In the second stage,the surface cracks of the pile began to develop slowly in the earlier this stage,the crisp sound of concrete cracking can be heard,the stress of steel bars,the displacement at the top of the pile,and the surface strain of the pile are less.The crack width increases linearly;later this stage,the rate of change of the steel bar stress,the displacement at the top of the pile,and the surface strain of the pile gradually increased,and the crack width increased rapidly with a nonlinear growth rate;the third stage is the stage of pile failure.At this stage,the stress of the steel bar,the displacement at the top of the pile,and the surface strain of the pile change significantly.The increase of the graph curve greatly exceeds the upper level.The concrete tensile crack is connected with the compression zone of the concrete and the damage of the concrete body.(2)Characteristics of cracks in pilesUnder different pile lengths,the location of the cracks in the pile is mainly related to the length of the anchorage section.Under the simulation of the test and the finite element software,the cracking position of the pile is located around 0.15~0.1m below the sliding surface;when the pile body is destroyed,the horizontal tensile cracks is mainly caused,but due to the different length of the pile,different diagonal cracks will appear;before the pile damage,the maximum height of the crack is 0.6-0.7 times the height.When the steel bar is in elastic deformation,the crack width calculated by each specification is in good agreement with the calculated by ABAQUS.When the pile is closer to the damage,the gap between the crack width and the crack width calculated by the standard and finite element software is greater.The reason for this is that the maximum crack limit of each specification is about 0.02 mm,and beyond this limit,the accuracy of the requested width value is low.Through comparison experiments,it can be k Nown that the ABAQUS calculation results are in good agreement with theexperimental values.Using the extended finite element method can effectively perform the cracking process without the need to divide the grid and local encryption,saving the calculation cost,and providing a new solution to the crack problem of anti-slide piles ideas.