Rolling pattern and process, number of rolling passes, speed of roller(Soil compactor and tandem) , precautions During rolling operation of various road layers as per MORTH and Indian standard

This article includes
1-What is Rolling  and why rolling is required in road construction
2- Type of roller (soil compactor and tandem)
3-Process of rolling and speed of roller
4 Required number of rolling passes
and Rolling pattern
5-Precautions during rolling

1-What is Rolling  and why rolling is required in road construction 

Rolling means pressing the particles close to each other.

Air during Rolling is expelled from the void space in the soil mass and, therefore, the mass density is increased.
Rolling of a soil mass is done to improve its engineering properties.

Rolling is an artificial process to achieve compaction in any required road layers.

which is done to increase the density (unit weight) of the soil to improve its properties before it is put to any use.

2- Type of roller 

Roller are generally divided in two

A- Tandem
B- Soil compactor

Rolling is done with the help of roller (soil compactor and tandem).Generally plain roller and vibratory  Rollers are used to compact the required layers of road.Use of roller(plain or vibratory) depends upon the thickness of various road layers or as directed by engineer -incharge.

Generally soil compactor is used to compact the embankment, subgrade, granular sub -base(GSB), WMM/WBM While tandem is used to compact the Dry lean concrete base course and surface course (Generally bituminous surface- "water is used during rolling of bituminous surface to avoid sticking of bitumen to drum").

3-Process of rolling and speed of roller

Rolling should be starred at Lower edge of Road and proceed towards the upper edge longitudinally for portion having unidirectional cross fall and super elevation while in portions having cross fall on both side, rolling should be commenced from outer edge and gradually increases towards crown.

During rolling process the roller should uniformly overlapping each of the preceding track by at least one – third width until entire surface has been rolled.

 Alternate trips of the roller shall be terminated in stops at least 1 met away from any preceding stop.

The speed of roller during rolling should not be more than 5 KM/ hour.

Rolling should be done till the required density achieved.

To get the technical specifications of WMM, kindly visit on below link 🔗 

https://gyanofengineering.blogspot.com/2019/02/wet-mix-macadam-wmm-sub-base-base.html

4- Required number of rolling passes 
and Rolling pattern

In general six "6" roller passes are applied to achieve desired compaction and number of actual rolling passes mainly depends up-to trail stretch(Done before to start the work of carriage way)  for any layer of Road. 

Generally rolling pattern comprises 
of two plain and 4 vibrations (low and high), with pattern of 1Plain+2Low Vibration +2High vibration +1Plain passes  are required for achieving the desired compaction.

 Materials Engineer will update the field staff about the required rolling passes.

To get the technical specifications of WMM, kindly visit on below link 🔗 

https://gyanofengineering.blogspot.com/2019/02/wet-mix-macadam-wmm-sub-base-base.html

5-Precautions during rolling

Rolling should not be done when the sub-grade is soft or yielding or when it causes a wave- like motion in the sub-base/base course or sub- grade.

To get the technical specifications of GSB, kindly visit on below link 🔗

https://gyanofengineering.blogspot.com/2019/02/full-details-about-gsb-including.html

Thank you

Mukesh Kumar
www.gyanofcivilengineering.com