METHODOLOGY OF BUMP INTEGRATOR TO FIND OUT ROUGHNESS INDEX.

                    BUMP INTEGRATOR TO FIND OUT ROUGHNESS INDEX.

It is generally an accepted principle that all pavement surfaces should be as even as possible, not only to afford a comfortable ride to users, but also to minimize stresses in both pavement structure and vehicles, and to minimize fatigue to users in the interest of safety. Roughness also determines the vehicle’s speed, road safety and vehicle operating costs. The quality of construction and maintenance of a road is reflected in the riding quality. A periodic measurement of roughness is, therefore, of vital importance to a highway engineer. 

The disturbance to which road users are subjected, though influenced to some extent the characteristics of the vehicle concerned, is essentially a function of road surface irregularity and it is essential to evaluate the same for necessary correction.

The conventional method of measuring unevenness of pavement surface is by means of feeler gauge or wedge, to measure the depression beneath a 3-meter straight edge. This is a very slow measuring process, cumbersome and costly and, therefore, it cannot be employed for long stretches.

An overall evaluation can be obtained much more quickly and                economically

From measurement of an effect which is a direct consequence of surface irregularity, viz. The relative vertical movement induced by it between the axle and chassis of a vehicle.

It is obviously essential that measurements of this kind should be made with a vehicle of standardized and unvarying characteristics. The Automatic Road Unevenness Recorder, developed at the Central Road Research Institute, New Delhi, furnishes such a vehicle in the form of a single wheeled trailer.

BUMP INTEGRATOR OR ROUGHOMETER Model gives speedily a quantitative integrated evaluation of surface irregularities on a digital counter. It comprises of a trailer of single wheel with a pneumatic tyre mounted on a chassis over which an integrating device is fitted. The operating speed of the machine is 30+1/2 km/hr. A vehicle, usually a jeep, tows the machine.

Its wheel runs on the pavement surface and the vertical reciprocating motion of the axle is converted into unidirectional rotary motion by the integration unit. The accumulation of this unidirectional motion is recorded by operating Sensor inserted in the circuit of six-digit digital counter, once for every 1 CM of accumulated unevenness.

Length of Path is indicated directly on another Six Digit Digital counter through Micro-Switch actuated by the cam fitted on the hub of the wheel with least count of 1 Meter. The two sets of counter readings give the unevenness index value in terms of cm /km.

               The vehicle is to drive over the test section at a speed of 30+1/2km./hr keeping to a steady position in the testing track, and avoiding swerving.

     Procedure  for Testing

Choose Minimum length of path of section before starting testing With Model  we can set the length of section from 50 Meter to 1000 Meters as per requirement of testing. Suppose we choose length of section as 200 Meters, Set the Four Digit Thumb Wheel counter to 200 Meters.                                                                                                   

a)     Switch ON the Main switch.

b)    Direct / Pre Set Switch to Direct Position

c)     Press Zero setting switch to make both counters reading as zero.

d)    Switch off the Main switch.

e)     Bring the Direct / Pre set Switch to Pre Set Position.

Start the Vehicle and run it at a speed of 30 Km/Hr and switch ON the Main switch from the starting point of testing site. The Panel Board will start displaying readings at pre set 200 Meter length. The buzzer sound will followed by the change of reading at both counters. Start noting the reading as under. 

          If we require reading at some reference point say K.M. stones or some other reference mark. Bring the toggle switch to direct mode position. Press zero setting push Button and start taking down the reading by pressing Reference Length push Button. These are direct readings of each section. Make sure reference length should be less than the preset length otherwise you get the reading at pre set length automatically.

Calculation for first reading

                                     

                   Unevenness Index = Bumps in cm            

                                                  Length of Section in Km

 

= 41     = 205 cm/Km

                                0.200

 

 

          CALIBRATIONS AND ESSENTIAL CHECKS

 

1.                 The distance traveled per wheel revolution should be determined by traversing an accurately known distance, say 1 km.

 

2.                 Uniformity of working radius of the wheel is important and must be checked at intervals.

 

3.                 Over the years due to slow but appreciable increase in the stiffness of the tyre the general level of the index value will change slightly. For the purpose of accuracy the tyre should be replaced at the end of 15,000 kms. And could be used on pother vehicle if required

As per CRRI, New Delhi.                       

Roughness standards                            

Road Section:

Vehicle No:

Condition of

Road Surface     :        RI in cm/Km

Good                             :        Below 250

Fair                      :        251 to 350

Poor                     :        351 to 450

Bad                      :        Above 450             

 Safety:

1. One flagman will guide the traffic from rear side of the jeep or utility
2.   All the personnel shall wear the PPE.
3. Only trained personnel shall be Deployed.