Application Research About Dynamic Stiffness Method In The Existing Cap-pile Testing

In our country, the commonly used pile foundation testing methods including static load testing, high strain dynamic testing, low strain dynamic testing, Core drilling method, acoustic method and so on. The low strain dynamic testing method including the reflected wave method and the mechanical impedance method. Low strain dynamic testing is based on the dynamics of single pile, if this method be used directly for detection of the existing piers, due to the upper part of the pile foundation piers, columns, bridges and other structures of the panel, the kinetics of response characteristic features of the dynamics are inconsistent with the single pile. Therefore, there will be a large error and prone to false positives if directly applied this method on the existing pier pile to testing and assessment.Mechanical impedance method is through applying incentives at the top of the pile, the determination of the dynamic response of the pile under the incentive to dynamic characteristics of the pile. Based on the relationship between the dynamic characteristics and the bearing capacity, pile integrity to judge and assess the integrity of the pile, the defect type, the defect location and carrying capacity. Depending on the method of applying incentives, mechanical impedance method can be divided into two types, namely, transient mechanical impedance method and steady-state mechanical impedance method. Because of high detection efficiency, the instrument is simple, easy to operate,transient mechanical impedance method has been widely used in engineering practice.Dynamic stiffness is an important parameter to determine the integrity and pile bearing capacity, the impact of factors including the quality of the pile, the distribution side of the soil and pile tip pile of soil and pile bottom sediment and so on. Through field tests and numerical simulation method, the mechanical impedance method in determining the application of the existing cap on the integrity and pile bearing capacity were studied. First, by comparing the results of the field test without pile caps and numerical simulations to verify the feasibility of ABAQUS software and simulation methods, followed by discussion of the many factors that influence the dynamic stiffness of the numerical simulation method, the final scene with a combination of static pile caps load test results, test results mechanical impedance method, proposed mechanical impedance applications in both the pile cap detection.