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Through the experiment, the deflection detection methods of the falling-ball instrument and the falling weight deflect meter (FWD) were compared, and their correlations were analyzed. The results show that the test depth and range of FWD are larger than the falling-ball instrument, and there is a good linear relationship between the road surface de...
Context in source publication
Context 1
... the falling ball, the falling ball test is a circular area with a diameter of 60 cm. The center point is tested once, facing the direction of the large mileage, and the left, top, right, and bottom points 40cm away from the center point are tested in sequence. The point distance of 40cm is chosen to avoid the influence between points, as shown in Fig. 1. In the drop weight test, we adopt the standard specified force value of 50KN and take 9 deflection sensors. Only the deflection value in the center point is used. During the test, a hammer is pre-hit at the center of the circle, and then the two hammers are tested with 50KN. When calculating, the average value of the two hammers is ...
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Citations
... e FWD detection is used more widely because of its established technique and easy implementation. FWD detection is based on the principle that, under the same impact load, the deflection of the void area increases significantly [7][8][9][10][11][12]. Because of the influence of climatic factors, such as solar radiation and ambient temperature, cement pavement panels experience temperature warping at different degrees [13][14][15], which affect the accuracy of actual pavement detection results. ...
The use of the falling weight deflectometer (FWD) for detecting pavement voids is based on the principle that, under the same impact load, the deflection of pavements with voids increases significantly. Under the effect of temperature, the cement pavement becomes warped, which affects the deflection detection accuracy. In order to improve the accuracy of FWD detection of cement pavement voids, a three-dimensional numerical model of cement pavement on a multilayered elastic foundation under the coupled action of temperature and load is established in this paper. In addition, under different pavement void, climatic, and load conditions, the influence of temperature difference between top and bottom of the plate on the deflection of the center point of plate angle load is studied. Considering the temperature difference between top and bottom, the temperature correction coefficient is established and experimentally verified the accuracy of the temperature correction coefficient. The results showed that, within the ranges of positive and negative temperature differences, the fitting degree of the temperature correction coefficient for the cement pavement exceeded 0.99, which was consistent with the variation trend of the temperature correction coefficient obtained through field tests. The error was lower than 7%, which verified the applicability of the temperature correction coefficient for the dynamic deflection of cement pavements based on FWD. The accuracy of the FWD method in detecting cement pavement voids was improved, and this study demonstrated theoretical reference value and practical engineering significance.
