IIT Gandhinagar  ajanta@iitgn.ac.in  ap@iitgn.ac.in
Soil Testing Lab
 
Previous
Next

Introduction Experimental Setup Data Analysis Results Theory

Consolidation Test

Need and Scope:

From consolidation test, the following information can be determined:
• Amount of settlement experienced by a soil-structure after load application
• Rate of consolidation of soil under a normal load
• Degree of consolidation at any time
• Pressure void ratio relationship
• Coefficient of consolidation at various successively increasing pressure
• Permeability of soil at various stages of loading
• Compression index of soil
The above information can be used to predict the time rate and extent of settlement of structures founded on fine-grained soils. It is also helpful in analyzing the stress history of soil.

Concept:

The gradual process which involves, simultaneously, a slow escape of water and a gradual compression, and which will be shown later to involve also a gradual pressure adjustment, is called consolidation. It is merely compression under a steady static pressure where the soil particles attain a closer packing due to sliding and rolling of particles as water escapes from the voids.


When a compressive load is applied to soil mass, a decrease in its volume takes place, the decease in volume of soil mass under stress is known as compression and the property of soil mass pertaining to its tendency to decrease in volume under pressure is known as compressibility. In a saturated soil mass having its void filled with incompressible water, decrease in volume or compression can take place when water is expelled out of the voids. Such a compression resulting from a long time static load and the consequent escape of pore water is termed as consolidation. Then the load is applied on the saturated soil mass, the entire load is carried by pore water in the beginning. As the water begins escaping from the voids, the hydrostatic pressure in water gets gradually dissipated and the load is shifted to the soil particles which increases effective stress on them, as a result the soil mass decrease in volume. The rate of escape of water depends on the permeability of the soil.

1. From the sample tube, eject the sample into the consolidation ring. The sample should project about one cm from outer ring. Trim the sample smooth and flush with top and bottom of the ring by using wire saw. Clean the ring from outside and keep it ready for weighing.
2. Remoulded sample :
    a. Choose the density and water content at which sample has to be compacted from the moisture-density curve, and calculate the quantity of soil and water required to mix and compact.
    b. Compact the specimen in compaction mould in three layers using the standard rammers.
    c. Eject the specimen from the mould using the sample extractor.


 
 
Copyright © IIT Gandhinagar All Rights Reserved