Design Steps for Overlay Thickness Design Using Bbd Data

We also offer survey services include BBD (Benkelman beam deflection studies) along with the estimation of characteristic deflection calculations based on IRC-81, 1997. We also offer Roughness index (also known as surface evenness or bump Integrator study) studies using a vehicle-mounted bump Integrator instrument as per IRC 16, 2004. The report will comprise of field readings and kilometre wise unevenness.

A Brief note on BBD Survey: This method of test covers a procedure for the determination rebound deflection of pavement under static load on the rear axle of the standard truck. The dual wheels of the truck are centred about the point to be tested. The probe is then inserted between the duals and places on the point. The dial gauge is set 1cm and the initial reading is recorded when the deformation is equal to or less than 0.025mm per minute. The truck is then slowly driven for a distance of 270cm and then stopped. The intermediate reading is recorded when the rate of the recovery of the pavement is equal to or less than 0.025mm per minute. Then the truck is further moved forward to 9m. The final reading is recorded when the recovery rate of the pavement is equal to or less than 0.025mm per minute. During the survey, the pavement and atmospheric temperatures are recorded at frequent intervals. Soil samples are also collected and tested in the lab for moisture content and plasticity Index. All these data are then processed to get the characteristic deflections. IRC-81 is extensively used to determine the calculation parameters. Corrections for moisture and temperature are applied to get the final results. These results further guide in the design of the overlay thickness.

A Brief Note on Surface evenness:

This test method defines the procedure for measuring the road roughness or surface evenness of road pavements, for construction compliance testing.
The roughness is determined from direct measurement of the longitudinal profile in each wheel path using a vehicle-mounted Bump Integrator. The roughness measurement is expressed in terms of the Roughness Index. The standard vehicle is mounted with bump Integrator and then driven on each lane. The instrument keeps recording the unevenness of the road on the longitudinal profile. This test is to be ensured that the section is dry and sufficiently clean and note any abnormal surface conditions that could affect the roughness results. For example, if the test is conducted on a pre-stressed structure, then the results could be abnormal as the values recorded at these locations will show high unevenness and will have a huge impact on the final results. The vehicle speed also plays a very important role in collecting the better results, generally, the vehicle will move at an average speed of about 40kmph to get better results. There are other readings that need to be recorded along with the test. They are the location of construction joints, intersections, cross drainage structures, grade separators, but not limited to these. Any other locations where the readings can pump to get erroneous stretch are to be recorded and are to be eliminated before compiling the final readings. They are generally expressed in mm per km.

We offer these services for BBD and Bump Integrator test for overlay design and compliance for completed roads.

Design Steps for Overlay Thickness Design Using Bbd Data

Source: https://esurveying.net/transportation-engineering-software/bbd-testing-service

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