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The usage of falling weight deflectometer

Views:1     Author:Site Editor     Publish Time: 2020-07-28      Origin:Site


The falling weight deflectometer is an advanced machine. It has its unique using method. 


Falling Weight Deflectometer FWD


The article mainly includes three parts:


1.Preparation for the falling weight deflectometer

2. Steps of instructions of the falling weight deflectometer

3. Different bending basin radii

 

1. Preparation for the falling weight deflectometer


The following steps should be performed before the tractor is driven to the test site:


Check tire pressure (should be up to 31 LBS/sq. in.), hydraulic pressure, wave surface of battery acid, wheel plate rotation. Hook the falling weight deflectometer trailer onto the tractor's trailer ball coupler and make sure the trailer's tongue coupling is correctly caught by the coupler ball. Install an inertial brake decoupling safety rope to connect it with the hook assembly of the tractor. Lift the tail pin and fix the falling weight deflectometer front support wheel. Insert the falling weight deflectometer taillight cable into the corresponding socket at the rear of the tractor and check whether all lights are functioning properly. Connect the thick and convex plug of the trailer power cable with the corresponding concave power supply input socket at the tail of the tractor.


Make sure the main switch on the trailer terminal is closed. When the drop hammer assembly is still in its highest position, check whether the probe of the central displacement sensor device extends through the bottom of the load plate at least about 10~20mm. Check that the lift/drop rope is on the two guide track wheels correctly.


2. Steps of instructions of the falling weight deflectometer


When the test system is driven to the test site and ready for test, the following steps shall be performed: Master switch. Press the RP button quickly to raise the drop hammer assembly to its highest position and release the two transport fastening supports. Remove the parting pin on the guide rod at the outer end of the lift/drop rod and insert it into the top of the guide rod.


Press the LP/RW button to lower the load to the ground and keep pressing the button until the PL indicator is off. Check that the outer end of the lift/drop rod is properly supported by the guide rod at this time. Insert the parting pin into the hole in the guide rod. This hole is located just above the lift-down rod, so the guide rod can be raised simultaneously with the lift-down rod.


Press the RP button until the straight component reaches its top.


If the falling weight deflectometer has not yet arrived at the test site, flip the transport fastening bracket on either side of the component so that it is in the locking position and lowers the component so that it lands on the bracket and the outer end of the lift/drop rod is also secured by repositioning the split pin on the guide rod.


3. Different bending basin radii


Different bending basin radii were used for different pavement structures. Subgrade or flexible base asphalt pavement, sensor distribution within 2.5m from the load center can be used. For high grade highway with semi-rigid base asphalt pavement, the radius of influence of bending and sinking should be 3 ~ 5m. The sensor shall be arranged within a range of 3 ~ 4m from the load center and automatically measured under computer control. All test data can be displayed on the screen or printed or stored in the computer. Load, sinkage (basin), temperature of road surface, mean value of sinkage, distance between measuring points, standard deviation, coefficient of variation and data representing sinkage value and evaluation result can be output.

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