Research On Low Strain Integrity Testing And Quality Evaluation Of Pile Foundation In Complex Karst Area

Pile foundation is an important form of deep foundation,and its quality has great influence on the whole project.However,as a concealed engineering,the quality of pile foundation is not easy to grasp,especially in karst areas,the defect rate of pile foundation is higher.Therefore,it is of great significance to strengthen quality control and post-construction quality inspection in the whole project.Relying on the pile foundation engineering inspection work in a work area of NanchangGanzhou Railway project,this paper selects the No.7 pile(defective pile)of a super-large bridge in this bid section as the research object,and uses ABAQUS software to simulate its defects such as concrete discontinuity,segregation,voids and the like at a certain depth,and obtains admittance curves in frequency domain and time domain,and analyzes the wave propagation law and characteristics at the location of the disease through wave theory.According to the measured waveform of the pile,according to the parameters obtained from the test and theoretical deduction,the defect analysis and judgment of the typical pile are made,and the theoretical calculation value of the defect location is given.Comparing the measured curve of low strain with the ABAQUS numerical simulation curve of the fourth part defective pile foundation,the difference between the calculated results of the two defects is within the allowable range,and the numerical simulation value is consistent with the theoretical analysis value and the measured calculation value.Combining with the results of on-site core drilling method,the types and locations of defects on the pile body are confirmed.Finally,aiming at this problem,through grouting reinforcement,coring it again,carrying out compressive strength experiment,and passing the recheck.And using the detection data of this section,we trace back the construction record,analyze the causes of pile founda tion defects,and give targeted treatment scheme.It has been used in the treatment of pile foundations in other karst areas in this section,and achieved good results,ensured the engineering quality and improved the construction progress.The research results provide beneficial exploration for integrity detection and defect treatment of pile foundation in karst areas.