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The paper presents the method of quantitative detection and evaluation of the corrugated pipes' grouting density. To this purpose many tests were carried out by using the impact-echo method. In the paper, we got the stress propagation paths of impact-echo in the corrugated pipes and established an internal cavity estimation model based on the time curve of the impact-echo. In the experimental model, the defects of the corrugated pipes were set up by artificial means which were divided into 5 levels: the full density, 3/4 density, 1/2 density, 1/4 density and all empty, then using the impact-echo tested the corrugated pipes' grouting densities. The results show that the estimation model of internal cavity estimation model can be used to quantitatively evaluate the degree of density of the corrugated pipes, the curves' correlation of the theoretical value of the model calculation and the experimental data is R=0.9426 which indicate that the two curves fit well.

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The freeze-thaw damage thickness of concrete is very important to assess the damage of structures. Such research at present is relatively small. For quantitative analysis of freezethaw damage thickness of concrete structure, this paper conducted a quick freezing method, entraining concrete test beam is immerged with 3.5% NaCl salt solution to freeze test. Based on ultrasonic detection methods, non-metallic ultrasonic instrument was used to detect concrete test blocks after 300 freeze-thaw cycles using multi-level measurement methods .Four test blocks were tested, each test block was tested 3 times. The formula of derivation of stress wave in the structures. The test data was analyzed and the damage thickness of concrete was achieved. The results show that: The damage thickness of concrete test blocks after 300 times freeze-thaw cycles and this value is less than the protective layer of steels.