Experimental And Application Researches On Internal Grout Condition Evaluation Of Tendon Ducts

As the fast development of road constructions in China, the post-tensioned concrete structures were used widely, whose grout condition inside tendon ducts attracts people'attentions. In order to guarantee the durability of bridges, and prevent water entering the tendons resulting in corrosion of tendons, the cable ducts should be grouted fully. During the actual injection, there are voids existing in tendon ducts due to the block of ducts, unreasonable injection method, and human carelessness, which will decrease the durability and load-carrying capacity of concrete bridges badly. In 2001, poorly grouted tendon duct was classified as one of the top ten quality defects in construction of roads and bridges by Ministry of Communications of the People's Republic of China.There are no mature technologies for internal grout condition evaluation of tendon ducts in China. At present, the main methods adopted in projects are core sampling and ultrasonic technology. Core detection has low speed and high cost, and will damage the steel cables easily, by this way, a big area of detection can not be made. The ultrasonic technology is disturbed by reinforcement, corrugated shell, testing surface and other factors. This method has long testing time, the size of holds can not be inspected. It has been proved difficult to be widely used. In this paper, a series of in-depth theoretical and experimental researches on nondestructive testing technology for internal grout condition evaluation of post tensioned ducts are carried out. The main works have been finished as follows:1. The necessity and urgency of researches on nondestructive testing technology for internal grout condition evaluation of tendon ducts was expounded. The author summed up the current inspection methods and existing problems, focused on the basic principles of Impact-Echo technology and status. On these bases, an antinoise nondestructive testing method for qualitative and quantitative evaluation of grout quality in tendon ducts was put forward.2. A series of indoor model testing were carried out to verify the feasibility of this method. Firstly, the IE signals were collected, some pretreatments, such as denoising and feature extraction were taken with wavelet analysis technology to form the reasonable training and testing samples.3. A complete single-hidden layer BP neural network was created to diagnose the internal grout condition of post tensioned ducts. Results show that the comprehensive evaluation method has good noise resistance, and does not seen to be affected at the presence of 5db measurement noise, simultaneously the flaw were identified exactly with a small error.4. The research methods were applied to the inspection and assessment of internal grout quality of Xiamen Dong'an bridge and Yichang-Wanzhou railway bridge. The corresponding grouting quality assessment programs were made according to the characteristics of actual projects to establish the diagnosis neural network models, good results had been achieved. Through the core sample comparison, the adaptability and reliability of this non-destructive testing method was verified further, which was benefit to the similar effective implementation.5. A comprehensive summary of the experimental investigations and application fruits of IE technology was conducted. The existing problem, focus and direction for future researches were discussed.