Research On Quality Nondestructive Testing Technology Of Plastic Concrete Cutoff Wall

Impervious wall engineering is an important part of the anti-seepage system for water conservancy and hydropower projects,and it is the basic facility and barrier to resist floods and ensure the safety of people's lives and properties.The quality of cutoff wall projects is of great significance for the sustainable and healthy development of water conservancy projects.The integrity of the wall(whether there are holes,cracks,and mud-filled sand,etc.)and impermeability are important indicators for the quality test and evaluation of the plastic concrete cutoff wall.The reliability of the test results is directly related to whether the project is safe and normal.Operation,and whether the choice of detection method is reasonable directly affects the correctness of the conclusion.Wall integrity testing currently uses nondestructive testing methods(electrical,electromagnetic,surface wave,elastic wave CT,etc.).Due to the variety of detection methods,complex procedures,and multiple solutions,it is difficult to master the technology.In addition,the cutoff wall has a certain depth,thin wall thickness,and long axis characteristics,which is different from the semi-infinite space objects that are applied to conventional non-destructive testing methods.The impermeability of the wall is mainly reflected by the index of permeability coefficient.The in-situ test for measuring the permeability coefficient of the wall is of great significance for evaluating the impermeability of the plastic concrete cutoff wall.Combining with previous engineering practice,the following problems are encountered in the in-situ test process: the drilling verticality is difficult to ensure,the permeability coefficient calculation formula is not applicable,the water injection process is cumbersome and the accuracy is low.The article works on the quality defects and permeability of the plastic concrete cutoff wall and the elastic wave nondestructive testing technology theory,and it also uses the Matlab numerical simulation test to verify the feasibility of the elastic wave CT method.In the velocity models,one simulates a normal cutoff wall,one simulates the presence of a low-velocity body inside the cutoff wall(the low-velocity body with sand or voids),and the other is the existence of a high-velocity body inside the cutoff wall(the internal concrete condenses well and the density is large).The shortest path algorithm is used for forward modeling,the SIRT method is used for inversion,and then Surfer software is used for graphic processing.Through these three models,it is feasible to demonstrate the quality of cutoff wall by elastic wave CT method,and well verified the effectiveness of the elastic wave CT method.This paper analyzes the limitations of the existing concrete permeability testing methods applied to the plastic concrete cutoff wall.Through the improvement of the algorithm,a new water injection test method is proposed,and an automatic working device for the water injection experiment site is developed,as well as data post-processing software.A new set of water injection test methods has been developed for permeability testing of seepage walls.Through a set of examples,the full set of technical solutions for testing and evaluating the integrity and impermeability of plastic concrete cutoff walls using elastic wave CT and water injection tests was introduced.The borehole excavation verification results confirmed the effectiveness and practicality of the method.In this paper,the quality inspection methods for plastic concrete cutoff walls are systematically studied and studied.According to the wall integrity tests and permeability tests,a set of effective technical solutions are summarized.As a typical subterranean concealment project,the engineering characteristics of the plastic concrete cutoff wall determine that the existing geophysical methods and the application of the on-site permeability coefficient test method have certain limitations.It is still necessary to carry out more in-depth research in combination with the characteristics of the project.