Arun Soil Lab Pvt.Ltd.
Geotech and Material Consultants
Ensure and Assure safety of the structures for a better
And safe place to live and work with strong foundation

Quality Consiousness is Our Core Concept

Certificate No. : TC-5382
NABL Accredited as per
ISO/IEC: 17025 - 2005

Other Investigations
  • Basic Principle the Performance of flexible pavements is closely related to the elastic deflection of pavement under the wheel loads. The deformation or elastic deflection under a given load depends upon subgrade soil type, its moisture content and compaction, the thickness and quality of the pavement courses, drainage conditions, pavement surface temperature, etc.
  • The deflection survey essentially consists of two operations
    (i) Condition survey for collecting the basic information of the road structure and based on this, the demarcation of the road into sections of more or less equal performance.
    (ii) Actual deflection measurements.
  • The stiffness of bituminous layers changes with temperature of the binder and sequently the surface deflections of a given pavement vary depending on temperature of the constituent bituminous layers. For purpose of design, therefore, it is necessary that the measured deflections be corrected to a common standard temprature. For areas in the country having a tropical climate, the standard temprature is recommended to be 35oC. Correction for temprature is not applicable in the case of roads with thin bituminous surfacing.
  • Correction for seasonal variation depend on type of subgrade soil, its field moisture content (at the time of deflection survey) and average annual rainfall in the area. For this purpose, subgrade soils have been divided into three broad categories, namely sandy/gravelly, clayey with low plasticity (PI ≤ 15) and clayey with high plasticity (PI > 15). Similarly, rainfall has been divided into two categories, namely low rainfall (annual rainfall ≤ 1300mm) and high rainfall (anual rainfall > 1300mm).
  • Traffic in terms of million standard axle is considered for the design of overlay. If sufficient data are available at the stretch with respect to the wheel load distribution of commercial vehicles or the vehicle damage fector and their transverse placement, the cummulative standard axles may be worked out based on actual data, otherwise design traffic may be calculated as per the procedure given in IRC : 37 and para 5.4 of IRC : 81 - 1997.
  • An average traffic growth rate of 7.5% is adopted for the roads usually.
  • It is recommended that the design life for strengthening of major roads should be atleast 10 years. Less important roads may, however, be designed for a shorter design period but not less than 5 years in any case.
  • Design of commercial traffic over the carriage way width is decided based on whether the road is single lane or two lane single carriage way or four lane single carriage way or dual carriage way.
  • The vehicle damage factor is also arrived at from axle load survey on typical road section so as to cover various influencing factors such as traffic mix, type of transportation, type of commodities carried, time of the year, tarrain, road condition and degree of enforcement.
  • Finally the overlay design is decided based on all the above parameters and guidelines given in IRC : 81-1997