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Archive for September, 2006

Soil Compaction

Posted by Kshitija Nadgouda on September 29, 2006

I talked about total settlement and differential settlement some time back. One of the major reasons for settlement of a structure is the presence of loose soil. So, to avoid such settlement (total or differential), it is essential to compact the soil.

Compaction of soil is the removal of air gaps (voids) from the soil. Soil, in general, is made up of three components: solid particles, air voids and water voids. Expulsion of air voids is called compaction, whereas removal of water voids is called consolidation (squeezing out of water).

Compaction
(Courtsey: Concrete Catalogue)

Compacting the soil, will increase its density and thus improve stiffness and strength of the soil. The degree of compaction will depend on several fators such as: type of soil (clay, silt, sand, organic soil, etc.), characteristics of soil (grading, plasticity, etc.), thickness of soil layer being compacted, weather conditions, amount and method of compactive effort applied, and water content of the soil at the time of compaction.

Four primary methods of applying compactive efforts are:

  • Static weight
  • Kneading action
  • Impact
  • Vibrations

Typically rollers are based on static weight and kneading action for compaction, while compactors use principles of impact and vibration to achieve compaction.

A special form of compacting is dynamic compaction where compaction is achieved by repeated dropping of a weight at a certain location and in a certain pattern over the site. More details here.

Dynamic Compaction

(Courtsey: Geoforum)

Typically Rollers perform compaction by static weight and kneading action whereas the equipment that perform compaction by impact or vibrations are called compactors.

Rollers may be further classified as tampers, smooth-wheeled or pneumatic tyred rollers. Sheepsfoot tamping compactor provides weight and kneading action.

Sheepsfoot Roller
(Courtsey: University of Missouri Extension)

Compactors may be Vibrating Roller compactors, Vibrating plate compactors and rammer compactors.

Vibrating plate compactor

(Courtsey: Haven Group)

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Copyright Kshitija Nadgouda.

Posted in Basics, Information | 4 Comments »

Update

Posted by Kshitija Nadgouda on September 12, 2006

I have accepted the post of a lecturer in my alma mater. Since it is my first attempt at teaching, I find that it is taking up more time than I expected. I am making the utmost efforts in writing articles, but the frequency has gone down dramatically. It is a promise that my next article will be up by the end of this week!

Posted in Basics, Information | 2 Comments »