Modified Proctor Test is performed to know the characteristics of soil through compaction with change in water content ultimately giving us the relation between dry density and moisture content. It is a modified version of the Standard Proctor Test.
Modified Proctor Test is generally performed in the circumstances of heavy consolidation hence also known as Consolidation Test. Bearing capacity and shear stress are the properties of interest for performing the Modified Proctor Test.
Need For Modified Proctor Test:
Following are the various necessities for performing Modified Proctor Test;
- The bearing capacity of the soil is one of the most important factors that must be considered during the construction of any structure or building.
- Before starting construction, it is necessary that the bearing capacity of the soil at the site should be investigated.
- In this article, you will be able to know about the difference between the revised proctor test and modified proctor test, and standard proctor test.
- If the soil bearing capacity available on site is not as per requirement, there are only two solutions. The first step is to build the foundation at a greater depth so that the total load is transmitted to the deeper underground level of the soil.
- The second measure is to improve the bearing capacity of the soil using various methods. Soil compaction is one of the most widely used methods to improve soil efficiency.
- The compaction of soil is increasing the density of soil by the use of mechanical energy. In the compaction process, soil density is increased by reducing the air deflection in the soil. The condensation principle was first developed by R. Proctor when constructing a dam in the United States.
- Modified Proctor tests are widely used to determine the condensation of their properties with changes in different types of soil and water content.
- The modified Proctor condensation test also determines the relationship between dry density and soil water content.
- One of the main objectives of the condensation process is to increase the shear stress of the soil by reducing its permeability and compressibility.
- Modified Proctor test is also known as heavy condensation test and is widely used in situations where heavy condensation is required.
Apparatus For Modified Proctor Compaction Test:
Various tools are necessary to perform the modified Proctor condensation test, which is as follows;
- Cylindrical metal mould which is either 100 mm diameter and 1000 cubic cm volume or 150 mm diameter and mm 2250 cubic cm
- Thermostatically controlled oven with the interior of noncoding materials to maintain temperatures between 105° C and 110° C.
- A sample extruder containing a compacted sample extruded from the mould.
- 75 mm, 19 mm, 37.5 mm sieves of IS.
- Capacity balance of 15 kg and sensitivity of 1 gram.
- Metal Rammer and Mixing Tools
Modified Proctor Test Procedure:
The stepwise procedure for the revised Proctor test is as follows;
Step 1. Take a representative sample of about 5 kg of dry soil.
Step 2. Sieve the sample properly through a 19 mm sieve.
Step 3. Add appropriate amount of water to the soil and mix well.
Step 4. Approximately 3% to 5% in the case of sandy or gravel soil in water and 12% to 15% percent water in soil like soil for soil.
Step 5. The weight of the mold with the base plate is attached to the nearest one gram. Record the weight as W1.
Step 6. Attach the extension collar to the mold.
Step 7. Take the amount of soil in the mold in each layer, such that its compact height is one third of the total height of the mold.
Step 8. Separate the moist soil into molds that separate five layers which should be approximately equal.
Step 9. Each player should hit 25 numbers with the help of 9 kg rammer.
Step 10. The rammer should have a drop of minimum 450 mm height from the soil so that it is compacted properly.
Step 11. After the completion of the condensation process, remove the extension collar and level the top of the mold properly with the help of straightening.
Step 12. With compacted soil take the weight of the mold to the nearest 1 gram and note it as W2.
Step 13. Remove the deposited soil from the mold and place it on a tray.
Step 14. Now take a sample from that sample to determine the amount of water in that soil.
Step 15. Take a number of results by adding an increase of water to the soil sample such as adding 1% to 2% of water for gravel and sandy soils.
Step 16. Kosovo and clayey add about 2% to 4% to the soil for water.
Step 17. A minimum of 5 readings should be taken, then the graph is plotted between the dry density of soil and moisture.
Step 18. The graph will give the value of optimum moisture content at maximum dry density.
Calculation of The Modified Proctor Test Procedure:
The calculation of the bulk density Yw in g / cm3 of each compact sample from the equation is as follows;
Yw = (m2 – m1) / Vm
m1 = Weight of mold with the base plate.
m2 = Weight of mould with the compacted soil.
Vm = Volume of mould in cm3
Calculate the dry density Yd in g/cm3 from the equation are as follows,
Yd = Yw / (1+W/100)
W = % of moisture content
Difference Between Modified proctor Test and Standard proctor Test:
Difference is as follows:
- In Standard Proctor test soil sample is compacted in 3 layers whereas in the Modified Proctor Test soil sample is compacted in 5 layers.
- In Modified Proctor Test 4.6 kg rammer is used with a free fall of 450mm while a lighter rammer of 2.5 kg is used in the Standard Proctor Test with a free fall of 300mm.
- A higher value of dry density is obtained in the Modified Proctor test as compared to the Standard Proctor test.
- Heavy consolidation requirement is fulfilled in Modified Proctor Test however in Standard Proctor test low consolidation is obtained.
- Modified Proctor Test is best suited for structures with high dynamic and static loadings like skyscrapers and runways, on the other hand, Standard Proctor Test is suitable for the soil with nonheavy loadings.
- OMC (Optimum Moisture Content) obtained in Standard Proctor Test is higher compared to Modified Proctor Test.
The percentage of soil moisture content corresponding to the maximum dry density will be stated as the optimum moisture content.
The optimum moisture content of the soil is defined as the water content at which the soil can be compacted to the maximum dense state.
Image courtesy: Image1
FAQs: Modified Proctor Test
Que.1: What is the difference between standard and modified Proctor tests?
1. In Standard Proctor test soil sample is compacted in 3 layers whereas in Modified Proctor Test soil sample is compacted in 5 layers.
2. In Modified Proctor Test 4.6 kg rammer is used with a free fall of 450mm while a lighter rammer of 2.5 kg is used in Standard Proctor Test with free fall of 300mm.
Que.2: Is code for Modified Proctor test?
IS 2720-8 (1983) is used to follow the procedure of Modified Proctor Test taking standard values for the accuracy of result to be otained.
Watch Video: Modified Proctor Test
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