CSIR - Central Road Research Institute
Shoulders for Rural Roads
U.K.Guruvittal Chief Scientist, CRRI Road Shoulders Roadway portion bordering travelled way for accommodating stopped vehicles and for lateral support of base and surface courses (FHWA, USA) Unpaved edges of the roadway, between the edge of carriageway and the shoulder break point (NRIDA) Space for pedestrians, slow moving traffic, bus stops,
installation of road signs, overtaking or halting U.K.Guruvittal Helps to drain out surface run-off, improves sight distance in hill roads (cut sections) Materials – Earth , Local / marginal material, bricks, concrete paver blocks 2 Road Shoulders
MORD Specifications, Section 407 – Construction (Earth/ granular material) MORD Specifications, Section 1903 – Maintenance of Earthen Shoulders
U.K.Guruvittal 3 Shoulder Geometrics
Minimum shoulder width – 0.6 m if ADT is less than 40, otherwise 1.2 m (www.pmgsy.nic.in/op48.htm) Hard shoulders of 1 m width on either side if soft soil is used for embankments (PMGSY Operations Manual) Shoulder width for rural roads – 1.5 m to 1.875 m
(IRC SP:20 ) U.K.Guruvittal Camber – Earthen shoulder 4%, Gravel shoulder 4 to 6.25%, Turfed shoulder 8.33% (www.pmgsy.nic.in/op48.htm)
100 ADT – 19,400 ESAL, Corresponds to T1 Category 10,000 to 30000 ESAL for design life of 10 Years
4 Materials / Construction IRC SP:20 – Density criteria (soil) similar to subgrade 3 (16.5 kN/m ). Ambiguity in MORD Specifications (Selected earth where specified shall conform to requirements of section 300 and shall be less than 10 percent) LL and PI limits – PI should be less than 10 Shoulder construction – Simultaneously with adjoining pavement layer, matching its thickness Earth and granular shoulder to be compacted to at
least 100% of its standard proctor density U.K.Guruvittal Box cutting not allowed for shoulder construction Shoulder Problems – Due to Shortcomings and Neglect during construction or maintenance 5 Materials / Construction
U.K.Guruvittal 6 Shoulder Problems
Erosion, Rutting, Camber irregularities, Edge drop off Shoulders can become hazard spot, affect road safety Hills – Shoulders affect stability of valley side slope
U.K.Guruvittal 7 Maintenance
Earthen/ Gravel shoulders to be maintained in a manner similar to earth / gravel roads Edge drop – Erosion from run-off and traffic abrasion, acute problem in case of concrete pavements Reverse camber – Avoided by proper blading Rain cuts to be filled and compacted – Smaller rollers Repairs to be done with same quality of material used for shoulder construction U.K.Guruvittal Turfing can be a good solution to solve many of shoulder problems 8 Smaller Rollers
9 Solutions Improved specifications , Proper construction practices, Excluding highly plastic soil usage Periodicity of inspection and maintenance operations should be higher than black top or concrete roads (Dressing of berms – Once a year (Routine Maintenance, IRC SP:20) Local materials, soft stones, Cell filled concrete, Quarry/ Mining waste, ICBP, Geosynthetic, Fal-G Industrial waste (Fly ash, slag, foundry sand, quarry waste, etc) + 3 to 5% cement can be another option (0.6 m wide, 0.15 m thick, 7 days compressive strength of 1.7 MPa) U.K.Guruvittal Technology demonstration projects for better shoulders 10 11