Presence of underation or unevenness of pavement surface.
The unevenness result in:
Increase fuel consumption
Increase wear & tear of wheels
Increase chance of accidents
The unevenness of pavement is measured with the help of equipment BUMP INTEGRATOR (BI) in terms of unevenness index which is the cumulative measure of vertical modulator of pavement surface recorded per unit design of the road.
The different value of unevenness on indian roads and corresponding serviceability is as follow:
NOTE- Internationally the riding quality of pavement surface qualified in terms of roughness & is expressed as “INTERNATIONAL ROUGHNESS INDEX” (IRI) having unit of (m/km) it can also be selected with unevenness index as follow
Bump Integrator (BI) Bump Integrators or Rough meters are superior to that of conventional feeler gauges or wedges because of the following reasons:
Quick measuring process
Ideal for long stretches It is available in the form of single wheeled trailer, these recorders give quantitative integrated evaluation of surface irregularities on an electronic counter.
The features of this are mentioned below:
Trailer of single wheel with a pneumatic tires mounted on a chassis
Penal board fitted with 2 sets of electronic counters (for counting the unevenness index value) Specifications:
Operating speed: 30 ±½ Km/Hr
Towing operation: By a vehicle, usually a jeep Maintaining the speed of 32 km/hr is a difficult task in using and working with a bump integrator, especially for small stretches. In order to overcome this limitation alternative approaches are needed to save time, money and reduce the laborious work. As a result the following relations are used. The empirical relationship between BI and IRI is given below:
By CRRI IRI=(BI/720)
By M.A Cundill IRI=(1+1.05(BI/1000)
For semi dense bituminous concrete, the conditions are Good<2500, (95km/hr) Average (2500-3000), (65km/hr-95km/hr) Poor>3500, (<65km/hr)
Unevenness Depends on Following Factors
Use of improper compaction method
Use of inferior quality material
Improper surface of subsurface drainage
Poor maintenance of pavement surface