How do you create a subgrade?

Other Subgrade Preparation Practices

  1. Ensure the compacted subgrade is able to support construction traffic.
  2. Remove all debris, large rocks, vegetation and topsoil from the area to be paved.
  3. Treat the subgrade under the area to be paved with an approved herbicide.

What is subgrade preparation in construction?

Preparation of the subgrade for construction usually involves digging, in order to remove surface vegetation, topsoil and other unwanted material, and to create space for the upper layer of the pavement. This process is known as “subgrade formation” or “reduction to level”.

What are the basic requirements for subgrade layer?

A subgrade’s performance generally depends on three of its basic characteristics (all of which are interrelated) as under:

  • Load bearing capacity.
  • Moisture content.
  • Stabilization with cement or asphaltic binder.
  • Additional base layers.
  • Strength & Stiffness of Subgrade Soil.
  • Construction Works.

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 the minimum thickness of subgrade?

5. What is the minimum thickness of compacted sub grade? Explanation: The minimum thickness of sub grade required is 300mm and in highways it is 500 mm as they are provided with the maximum best facilities.

What is difference between subgrade and subbase?

A subgrade is made up of native soil that has been compacted to withstand the loads above it. There is no consistency in regards to the terms of subbase and subgrade, but normally the subgrade is the native soil while the subbase is the layer of soil or aggregate on top of the subgrade.

What is the function of subgrade?

The sub grade soil and its properties are important in the design of pavement structure. The main function of the sub grade is to give adequate support to the pavement and for this the sub grade should possess sufficient stability under adverse climatic and loading conditions.

What is the minimum subgrade CBR for a road construction?

CBR value for subgrade in road construction in India : CBR value is taken at 2.5mm & 5 mm penitration. in subgrade material CBR value should be nearly 15-19% .

What is the maximum limit of subgrade thickness?

What is the maximum limit of sub grade thickness? Explanation: The prepared sub grade is limited to a maximum of 300 mm, in any case it must not exceed 300 mm. Explanation: The base course is laid for a thickness of 100 mm, it may exceed in some cases, in some cases it may be 80 mm and even 40 mm in unimportant roads.

What is the minimum CBR value for subgrade?

What are the layers in road construction?

The road pavement structure layers are as follows.

  • Subgrade or road bed.
  • Sub base course.
  • Base Course.
  • Surface coarse or wearing course.

What are the function of base course?

Under rigid pavements, the base course is used to: (1) provide uniform and stable support, (2) minimize damaging effects of frost action, (3) provide drainage, (4) prevent pumping of fine-grained soils at joints, (5) prevent volume change of the subgrade, (5) increase structural capacity of the pavement, and (6) …

Which is the best description of subgrade construction?

CHAPTER SEVEN: SUBGRADE 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 is the sub grade treatment carried out?

The Embankment top shall be levelled to facilitate placement of first layer of Sub-grade, scarified, mixed with water and then compacted by rolling so as to achieve minimum dry density as specified in the modified Technical specification. Sub-grade treatment specified for Sub-grade shall be carried out as per approved drawing.

What do you mean by preparation of subgrade?

The foundation of the pavement structure is known as subgrade. Preparation of subgrade consists of all operations before the pavement structure could be placed over it and compacted. The subgrade may be situated on an embankment or excavation or at the existing ground surface.

What should I use to treat subgrade under my pavement?

Treat the subgrade under the area to be paved with an approved herbicide. This will prevent or at least retard future vegetation growth, which could affect subgrade support or lead directly to pavement failure.