Table of Contents
Why GSB is used in road construction?
GSB or granular sub-base prevents capillary water from rising; its particle size is so designed that the capillary action stops and cant go beyond GSB layer. Secondly, it works like a drainage layer where water can pass without damaging other road layers.
What is the purpose of GSB?
INTORDUCTION The Granular Sub Base (GSB) layers are used in the flexible pavements to provide a stress-transmitting medium to spread the surface wheel load to a large area so as to prevent the shear and consolidation deformations.
What are the functions of granular base course?
It acts as a drainage layer for the pavement to avoid excessive wetting and weakening of subgrade.
- Permeability requirements of Granular Sub-base (GSB) is 300m/day as per IRC 37:2012 Flexible Pavement.
- Strength wise GSB is more superior as compared to the subgrade.
What is GSB road work?
After the Earth Work the Sub-Base of the road is constructed with Granular material. Granular sub-base (GSB) is constructed with well graded Granular Soil, maintaining suitable moisture content and compacted in layers not exceeding 200 mm.
What is the size of GSB?
Granular Sub Base (GSB) Road Material, Packaging Size: 50 kg
| Usage/Application | For Construction |
|---|---|
| Packaging Size | 50 Kg |
| Density | 2.1 g/cc |
What is the grade of GSB?
Out of six GSB grades Grade III, Grade IV, Grade V and Grade VI obtained permeability values are more than predicted values. AASHTO-57 Grade obtained permeability is around 17\%less than predicted value, for Grade I & Grade II no flow of water is observed so values are less than predicted value.
What is a good CBR?
What are the typical CBR values? The harder the material, the higher the CBR value. A CBR value of 2\% is usually found for clay, high-quality sub-base will have CBR values between 80\% and 100\%, and some sands may have values around 10\%. The CBR testing can be applied to soils with a maximum particle size of 20 mm.
What is the compaction factor of GSB?
Specified compaction for GSB – 98 \% of MDD (MDD by IS 2720 Part – 8). There is a possibility of getting a higher compaction which results normally upto 104\% due to the presence of coarse crushed material.
What is a good CBR value?
A clayey soil generally has a low CBR value (less than 8). Sands are more granular and drain better and will generally have CBR values between 15 and 35. Gravel will have the best CBR values, generally 25 and up. That is why it is suggested to save the best material to cap the subgrade.
What is the function of GSB in road construction?
GSB or granular sub base is typically a material which prevents capillary water to rise to top road layers as its particle size is planned in such a way that the capillary action stops and cant go beyond GSB. Secondly it has to act as a medium where water can pass through without damaging other road layers.
What is GSB layer in concrete?
Granular Sub-base (GSB) consists of laying and compacting well graded material on prepared sub-grade in accordance with the specifications.: GSB layer is intermediate layer in between Sub-grade and Wet mix macadam.
What is GSB (granular sub base)?
Granular Sub Base is a layer in road foundation just above the compacted sub-grade layer. GSB or granular sub-base prevents capillary water from rising; its particle size is so designed that the capillary action stops and cant go beyond GSB layer. Secondly, it works like a drainage layer where water can pass without damaging other road layers. 1.0
What are the requirements of GSB?
Granular Sub-base (GSB) materials shall be free from organic or other deleterious constituents It shall confirm the grading requirements as per MORTH V Table 400-1 The toe line/fixing of pegs to mark the limits of Granular Sub Base (GSB) shall be done before the commencement of work.