Journal of Irrigation and Drainage Engineering

To realize high-efficiency and precision paddy field leveling, a tractor-attached laser-controlled rotary scraper land leveler for paddy fields was designed. An elevation model for the laser leveler’s scraper was established, and the elevation adjustment error was determined. Computer simulations showed that within the normal operational range of the laser-controlled leveler, the elevation error between the scraper and the laser receiver was 4.37%, and the maximum error was less than 9.5 mm. These results indicate that the laser receiver signal of the laser-controlled rotary scraper land leveler can accurately reflect the scraper’s elevation motion. Tests were carried out to monitor coil current and scraper motion with a data collector. It was found out that the average response time for lifting the rotary scraper decreased by 72 ms and the average response time for lowering it decreased by 10 ms in comparison with a laser-controlled vertical scraper. In addition, the speed of lifting and lowering the rotary scraper was about 5 times that of the vertical scraper. Finally, a leveling verification test was conducted in a 0.36-ha paddy field, and field flatness was measured using a mesh method before and after the operation. It showed that the standard deviation of the relative elevations of the field decreased from 5.97 to 1.59 cm and work efficiency was $8.7\mathrm{mu}/\mathrm{h}$ (1 mu = 0.67 ha.), which that the proposed leveler worked effectively and more efficiently than the rotary leveler.

In this study, a novel backwashing maintenance method for permeable concrete pavements (PCP) was developed, and its performance was evaluated via a 2-year field comparative study at two PCP sites. Results showed that regular maintenance can mitigate clogging and extend the service life of PCPs. After 2 years of regular maintenance via hand sweeping, vacuuming, pressure washing, vacuuming followed by pressure washing, and the proposed novel backwashing maintenance method presented in this study, the average surface infiltration rates (SIRs) at the maintenance points (testing locations) were 1.3-fold, 1.3-fold, 1.7-fold, 1.8-fold, and 2.1-fold those of the corresponding control points at the mildly clogged PCP Site 1, and 2.1-fold, 3.5-fold, 6.1-fold, 14.0-fold, and 18.1-fold those of the corresponding maintenance points at the heavily clogged PCP Site 2, respectively. The proposed novel backwashing maintenance method outperformed conventional maintenance methods, but its recovery rate depended on the clogging conditions and the backwashing pore flow velocity in the PCP layer. Further studies are needed to promote the wide application of this novel backwashing maintenance method and prolong the service life of PCPs.