## 2 Pavement Mechanical Properties Test Device  
Figure 1 shows the structure of the test device, which mainly includes moving mechanisms, a reaction bearing mechanism, a deflection loading device, a rebound modulus loading device, hydraulic pressure stands, a control system, and a data collection system. The moving mechanisms control the lateral and longitudinal movement of the test device along the road surface; the lifting hydraulic cylinders control the vertical road surface movement of the test device; the reaction force generated during loading is borne by the reaction bearing mechanism; the deflection and rebound modulus loading devices provide the loads required for the deflection and rebound modulus testing, respectively; the hydraulic pressure stands provide hydraulic power; the control system enables movement and loading; the data collection system enables data collection, storage, and analysis; the lateral movement mechanism is installed on the top of the lifting mechanism, which is movably connected to the loading device, and the lifting mechanism is fixed to the lifting hydraulic cylinders, so that the lifting mechanism and loading devices move up or down with the lifting hydraulic cylinders.  
The testing process is as follows: First, the test device is moved above the detection area by the motor-driven longitudinal and lateral moving mechanism. Second, the lifting hydraulic cylinders extend downward via the hydraulic pressure stands to lower the lifting mechanism, the four outriggers on the lifting mechanism are in full contact with the road surface, and the test device is jacked up so that the longitudinal moving mechanism is suspended; then, the movement of the lifting hydraulic cylinders is stopped to prevent the longitudinal movement of the test device during the loading process. Third, the hydraulic pressure stands enable the deflection or rebound modulus loading device to press down to the pavement's mechanical properties testing point. Fourth, two high-precision laser displacement sensors are placed at the testing point. Fifth, the control system controls the loading device to apply a load to the pavement, and the data collection system simultaneously collects sensor data and performs data processing. Sixth, after the loading stops, the control system enables the loading device to retract upward, to prevent it from contacting the road surface, and enables the lifting hydraulic cylinders to retract upward, so that the longitudinal moving mechanism lowers and contacts the road  
Figure 1: Device structure diagram.  
surface; then, the longitudinal moving mechanism travels to the next pavement mechanical properties detection area.  
The test device can apply dynamic and static loads. Moreover, there are various ways to achieve the dynamic loading waveform, and the loading accuracy is high, which makes up for the shortcomings of other load-generating devices for testing pavement's mechanical properties. The loading reaction force generated is borne by the reaction bearing mechanism and is not transmitted to other structures, which ensures smooth loading. High-precision laser displacement sensors are used to measure the displacement signal of the pavement, and the test device is equipped with an automatic collection device and analysis software of the dynamic and static loads and the corresponding deformation during the loading process, with functions such as signal collection and data storage and analysis. The test device enables automated and precise testing of the deflection and rebound moduli, greatly improving the test efficiency and the accuracy of the test results and eliminating the influence of human factors. The test device can move freely along the lateral, longitudinal, and vertical directions of the road surface; hence, it can realize the measurement of testing points for different mechanical properties.