What is Soil Test? | How much soil test is needed to build a house or take the load of any structure?

What is Soil Test? 

Soil is a type of soil that we cannot easily understand by looking at it even if we want to. It is not possible for us to know what is under the soil and where is soft soil, where is sandy soil and where is hard soil. Therefore, when constructing a high-rise building, soil test is mainly done to see whether the condition of the soil below is suitable for building or not. The Bengali meaning of ‘soil test’ is soil test, but in engineering language, testing the soil below the structure or building is called ‘soil test’ or ‘sub-soil investigation’.

Why is Soil Test done? 

Soil test is done to determine the safe bearing capacity of the soil underground. Remember that soil test is essential for designing any type of establishment such as residential buildings, commercial buildings, schools-colleges, mosques-temple, hospitals, shopping complexes, bridges-culverts, roads-highways, railway lines, airports, power plants, etc.

However, since the safe bearing capacity of soil in our country is 9-10 tons per square meter, engineers generally do not refer soil test for Light Structure (one or two-story building), the foundation of these light buildings does not receive more load than this. However, soil test is definitely necessary for buildings with more than three floors.

Remember, designing without a soil test is the same as taking medicine without a doctor's prescription. Without this, it is not possible for anyone to know the properties of the underground soil, only by looking at the soil test report can an engineer say what kind of foundation is needed to protect the establishment. The reason why we do soil or soil tests is to test the bearing capacity of the soil. Soil testing or soil testing is done. The first step and most important task when constructing a building is soil testing. The building or building is covered for the construction of a factory, residential building, mosque, madrasa, market, power plant, etc. Then the structure of the structure is made based on the results of the digital soil test through soil condition or testing. Therefore, it can be said that soil testing is the main pillar of the building. Without which, building design fails. Building without a soil test is the same as taking medicine without a doctor's prescription. Therefore, the role of soil testing is essential for building construction.

The materials required for a soil test are given below:

 

1-Tepaya 2-Cello machine 3-Boring pipe 4-Caging pipe 5-Hammer 63.5 kg 6-Iron pulley 7-Drill pipe 8-Chisel 9-Hose pipe of the machine. For water discharge. 10-Guide pipe for determining the value of penetration N. 11-Split spoon sampler 12-Rope More other materials are required. 

 

Those materials that are more work have been listed.

Soil test is usually done in 2 ways 

 

1-Through the WAS Boring method. 

2-With the help of hydraulic machine. Since WAS Boring is more common in Bangladesh. So I will talk about WAS Boring method. And I will highlight the working method.

 

Soil testing is generally done in two types: 1. Field test 2. Laboratory test Field

Soil testing is generally done in 2 ways: 1. Field test 2. Laboratory test field

What is a plate load bearing test? 

The bearing capacity of any soil layer can be accurately determined and the compressibility of the soil can be measured or determined.

 

What is S.P.T. Test? 

Just as the N value of soil can be determined, soil can be collected and tested in a laboratory.

 

Laboratory Test: Steps of Laboratory Test as per ASTM:

 

1.Moisture content test. 

2.Density test. 

3.Relative weight test. 

4.Plasticity test. 

5.Consolidation test. 

6.Direct shear test. etc. 

standard penetration test n value. 

standard penetration test astm.  

It is not known in advance how much space is bored. According to the source (BNCC) code:

 

1. For one to three kathas of land, 3 boreholes will be required. 

2. For three to five kathas of land, 5 boreholes will be required.   

3. For five to 10 kathas of land, 8 boreholes will be required.

 

The soil test procedure is given below:-

 

 

To test the soil, first clean and level the area where the soil will be tested. If the area is muddy or watery, fill it with sand. Once the sand filling work is complete, the T-pillars should be installed. A hole for the soil test will be made along the middle of the 3 heads on the T-pillar. An iron pulley should be installed below the 3 heads of the T-pillar. A handle is inserted through the pulley, one end of which is a hammer and the other end is open, which is pulled by hand and lifted above the hammer. A caging pipe should be installed along the hole for testing the soil. Since the upper part of the soil is a little soft.

 

The caving pipe is 5-10 feet long. The caving pipe is inserted by hammering. Now a boring pipe is inserted through the caving pipe with the chisel head. Now the guide line pipe is inserted through the hole in the middle of the hammer. A mark is cut 30" from the bottom of the guide pipe. The reason for this is that the hammer is raised to that point and then released. To determine the number of strokes of the boring, first an 18" mark is cut on the boring pipe, for which no stroke is taken for 6". Now when the hammer is raised to 30" by means of a rope and released.

 

The number of holes in one foot is calculated. After this, the number of holes is recorded in the log by cutting 6 "sequential marks without boring. To collect soil samples, samples are collected every 5 feet. Depending on the N value, it can be understood how many holes are to be bored. In this way, the work is completed step by step with the contractor. Later, all the samples are collected and sent for laboratory tests. Depending on that, the structure of the building is designed.

 

Find out the condition of the soil by looking at the N value of the Soil Test. 

 

✓If the value is 2 or less, it means Very Soft soil, whose load-bearing capacity is only 2 tons per square meter. 

✓If the value is 2-5, it means Soft soil, whose load-bearing capacity is 2-5 Ton/ Sqm. 

✓If the value is 5-9, it means Medium soil, whose load-bearing capacity is 5-10 T/ Sqm 

✓If the value is 9-17, it means Stiff or hard soil, whose load-bearing capacity is 10-20T/ Sqm 

✓If the value is 17-33, it means Very Stiff or very hard soil, whose load-bearing capacity is 20-40 T/ Sqm 

✓If the value is above 33, it means Hard or very hard soil, whose load-bearing capacity is above 40 Ton per square meter.

The precautions to be followed while performing a soil test are given below:-

 

1. Check whether the chisel has the correct diameter. 

2. Check whether the holes on the 2 ends of the chisel are working properly. 

3. Note the number of strokes correctly. 

4. Check whether the hammer is 63.5 kg. 

5. Check whether the split spoon used to collect the soil sample is working properly by filling it with water. Its importance is a little more in getting the sample correctly. Otherwise, the sample can enter the water and destroy the soil. Therefore, it is necessary to work with caution. 

6. Mark and write on each sample so that it is easy to understand. Therefore, if you follow these guidelines, it is possible to get an accurate soil test report.