To determine the relative density of soil sample by Vibrating Table

OBJECT : To determine the relative density of soil sample by Vibrating Table.

OBJECTIVE AND SCOPE

To familiarize the students with a simple method of obtaining a compaction control density for cohesionless soil. In this test, we determine the state of density of cohesionless soil with respect to its maximum and minimum densities.

STANDARDS

AASHTO T210-90

ASTM D4253-83

BIS1377:part 4

EQUIPMENTS

1. Vibrating table
   
2. Mould
   
3. Surcharge weight
   
4. Surcharge plate
   
5. Screws
   
6. Balance
   
7. Straight edge
   
8. Weight balance.
   

THEORY

The term relative density density index or degree of density is used to express the relative compactness of a natural soil deposit. It indicates the in situ denseness or looseness of granular soil. The density index is defined as the ratio of the difference between the void ratio of the soil in its loosest state “emax” & it’s natural void ratio “e” to the difference between the void ratio in the loosest & densest state.

I_D=

Where:

e_max.= void ratio in the loosest state.

e_min.= void ratio in the densest state.

e_.= natural void ratio of the deposit.

This term is used for cohesionless soils only. When the natural sand of the cohesionless is in its loosest form, e =e_max& I_D= 0. When the natural deposit it is in its densest state, e=e_min& hence I_D=1. For any intermediate state, the density index varies between zero and one.

Relative Density can also be calculated from the following formula:

I_D=

PROCEDURE

1. first of all field density of the soil is determined by any suitable methods mentioned previously.
   
2. Then mould is taken and its dimensions are measured in order to determine its volume.
   
3. Sand is then poured in it from the least possible height so as to cause minimum compaction while pouring.
   
4. The surface of the mould is levelled with a straight edge any excess sand is removed. Its weight is then determined to calculate the dry density in the loosest state.
   
5. Now the mould is fitted to the vibrating table with the help of screws. It is then attached with a collar. More sand is poured into it. Then place the surcharge plate and surcharge weights above it. We used a smaller surcharge weighing 24.9kg.
   
6. The vibrating table is then allowed to vibrate at 60Hz for 8 minutes.
   
7. The collar is then detached from the mould and any excess sand is removed and the surface is levelled with the help of a straightedge. The sides are also made clean by applying a brush on the sides.
   
8. The mould is then detached from the vibrating table by unfastening the screws and the weight is determined so as to calculate the dry density of the soil in the densest state.
   

OBSERVATION

Moisture Content:

Heiht of mould= ___________ (cm)

Diameter of the mould=____________ (cm)

Volume of the mould (V)=____________ (c.c)

Wt. of empty mould=____________ (gm)

Wt. of mould + sand in loose state=____________ (gm)

Wt. of sand in loose state (W_min)

_(min)= =____________ (gm/c.c)

Wt. of mould + sand in densest state(W_max) =____________ (gm)

_(max)= =____________ (gm/c.c)

Field density, _(field)=____________ (gm/c.c)

Relative Density, I_D=____________

RESULT

The relative density of given soil sample is____________

Review Questions

1. What is Relative Density?
   
2. What is the unit of Relative Density?
   
3. What is the range of the values of relative density?