How do you prepare subgrade?
Construction Methods The subgrade shall be prepared in lengths of not less than 100 metres at any one time, unless otherwise approved by the Engineer. Subgrade material shall be scarified to a depth of 150 mm until the soil is fully loosened. Any lumps or clods shall be removed or broken to pass a 50 mm sieve.
What is a subbase in construction?
In this publication, a subbase is defined as the layer of material that lies immediately below the concrete pavement. Some engineers call this a base course since that term is used to designate the first layer beneath an asphalt surface.
What is subgrade in building construction?
Subgrade is that portion of the earth roadbed which after having been constructed to reasonably close conformance with the lines, grades, and cross-sections indicated on the plans, receives the base or surface material. In a fill section, the subgrade is the top of the embankment or the fill.
How do you make a GSB bed?
The GSB Material is spread with the help of motor grader on the approved layer of Sub-grade in single layer of 200 mm with Grading either IV or V. During spreading and mixing by grader in site, water is sprinkled over the material by water browser mounted on water tanker.
What is the first step involved during the construction of subgrade?
What is the first step involved during the construction of subgrade? Explanation: It is important to remove vegetation and topsoil containing organic content before starting the construction. Excavation of high spots and subsequent levelling is done after the removal of vegetation.
What is sub base material?
Sub-base material is produced by crushing either limestone or granite rock. The sub-base is designed to evenly spread the load on traffic bearing areas such as pavements and roads. Made up of a load-bearing layer of aggregate, the sub-base is laid on the sub-grade layer below.
What is a sub base?
In highway engineering, subbase is the layer of aggregate material laid on the subgrade, on which the base course layer is located. It may be omitted when there will be only foot traffic on the pavement, but it is necessary for surfaces used by vehicles. Subbase is often the main load-bearing layer of the pavement.
What is the function of sub base?
The function of a subbase is to help prevent pumping of fine-grained, subgrade soils. Pumping, which leads to the loss of soil material beneath slab edges and joints, occurs when three factors exist in combination: pumpable soils, excess water under the pavement, and frequent heavy truck loads.
What is sub base used for?
What does sub base include?
The subbase is the layer of aggregate material that lies immediately below the pavement and usually consists of crushed aggregate or gravel or recycled materials (see Section 6C-1 – Pavement Systems for more information).
What is subgrade material?
In transport engineering, subgrade is the native material underneath a constructed road, pavement or railway track (US: railroad track). It is also called formation level. The term can also refer to imported material that has been used to build an embankment.
What is minimum thickness of GSB?
➢The recommended minimum thickness of granular base is 225 mm for traffic upto 2 msa and 250 mm for traffic exceeding 2 msa.