Figure 6-3 Schematic Diagram of Test Device
The test was carried out on the side of the field railway, and the test site was selected on the side of chengdu-kunming railway line. The height of railway embankment is 1m, and the test device is shown in Figure 6-3. The device consists of a sealed pressure box and a piezometer tube. The pressure box is a closed container filled with pure water. When the railway vibration comes, the pressure is transmitted to the container through the soil layer (hard plastic clay). Vibration waves make the pressure box press and transmit the pressure to the water body. The increase or decrease of pressure in the water body can drive the water column in the upper piezometer to vibrate up and down. The pressure box filled with water is buried in the corresponding soil, and the stress wave makes the water column vibrate synchronously through the pressure box. Record its amplitude, frequency, time and train type (including passenger cars and trucks), and use the camera as an auxiliary means to test.
The test time was May 2002. On cloudy days, the vibration source comes from the welded joint of seamless rail. The test is divided into five points for sampling. The distances between the five points and the vibration source are 1.5m, 2.0m, 3.8m, 4.5m and 6. 1m respectively. The point 1 is located in the gravel of the embankment slope, the second point is located outside the embankment buffer ditch, the third point is located in the newly exposed undisturbed hard plastic clay, and the soil quality of the fourth and fifth points is the same as that of the third point. The result chart is mainly drawn according to 3, 4 and 5 points. Data acquisition adopts the method of computer capture after camera shooting, and the amplitude values at 0. 1s and 0.2s…… ... are collected respectively, and curves are drawn with these values.
The test results are shown in Figure 6-4. The experimental observation results show that:
Figure 6-4 Measured Vibration Wave Process Curve
The closer (1) is to the vibration source in the soil, the greater the vibration amplitude. The maximum height of the water column can reach 13mm (truck) when it is 3.8m away from the vibration source, and it can be reduced to 2mm (truck) when it is 6. 1m away from the vibration source.
(2) The vibration of passenger cars is uniform and stable, while the vibration of freight cars is extremely uneven, and its amplitude is about twice that of passenger cars.
(3) The truck sometimes stops vibrating, that is, the amplitude fluctuates within a small level, but sometimes it can jump to a very high level.
(4) The maximum vibration of the bus appears at the first vibration, which is related to the heavy nose of the bus (the static load of the wheel reaches 20t), while the maximum vibration of the truck appears randomly.
(5) The vibration frequency of passenger cars is obviously equal to the number of train sections; This law is obvious when the amplitude of freight car is large, but not obvious when the amplitude is small.