Soil Test Service & Soil Investigation
Some ideas about soil test and soil test report.
In fact, many people are being worried about what is written in the soil test Recommendations. They think that is the last word. In fact, it is not the last word, but it does not fall at the level of any word. Report means Information. And a Geo technical Engineer will decide what the Foundation is will be.
What is Soil Test?
The meaning of soil test in engineering language is the investigation of the soil under the ground of an installation or building.
Site visits for Soil Test Service
The site should be inspected before testing the soil. This will give you a good idea of the condition of the soil surface and will help to determine the process of the soil test.
The following data would be collected from the site:
- The geographical location of the area
- Whether there are holes
- Whether the soil has been cut and removed.
- Whether there are signs of landslides.
- The height of the surrounding water (river or pond).
- Drainage system etc.
Purpose of soil test:
- Proper foundation design
- Structural design of the house
- Determining construction costs
- Ensuring the construction security
- Selection of construction method
Find out the condition of the soil by observing the N value of the soil test.
(1) If the value is 2 or less, the is soil very soft should be understood, which has a carrying capacity of only 2 tons per square meter.
(2) If the value is 2-5, soft soil, bearing capacity 2-5 Ton / Sqm.
(3) Medium soil if value is 5-9, bearing capacity 5-10 Ton / Sqm.
(4) If the value is 9-17 then stiff or hard soil, bearing capacity would be 10-20 Ton / Sqm.
(5) If the value is 17-33, very stiff or very hard soil, bearing capacity 20-40 Ton / Sqm.
(6) If the value is above 33, it means Hart or very hard soil with a carrying capacity of more than 40 Ton per square meter.
How many boreholes have to be made for the land?
- 3 boreholes have to be made for land up to 3 Katha’s.
- You have to make 5 boreholes for 3-5 Katha’s
- 8 Borehole is applicable for 5-10 Katha’s
Why it is necessary to take a soil test service from professional?
Soil tests are done to determine the safe bearing capacity of the subsoil. Remember that any type of installation such as residential buildings, commercial buildings, schools-colleges, mosques-temples, hospitals, shopping complexes, bridges-culverts, highways, railways, airports, power plants. Etc. Soil test is essential for design.
However, since the safe carrying capacity of soil in our country is 9-10 tons per square meter, engineers usually do not refer to soil test for light structure (one or two storey building). The foundation of these light buildings does not have more load than this. However, soil testing is essential for more than three storey buildings.
Remember that designing without a soil test is the same as taking medicine without a doctor’s prescription. Without it, it is not possible for anyone to know the characteristics of the subsoil. Just looking at the soil test report, what kind of foundation is needed for an engineer to protect the possible installation.
Importance of soil test for residential buildings
Soil test should be done before the start of construction, especially before the design. Because it is an essential prerequisite for foundation design. The main purpose is to determine the bearing capacity of the soil. Again, ideas about the type of foundation can also be obtained through soil test. That is how we recognize the foundation will be shallow (e.g. footing) or deep (e.g. piling).
This ‘bearing capacity’ and ‘foundation type’ are mentioned in the soil test report. The foundation is designed according to the soil test report. SPT, soil type, stratification, various test results, boring point layout etc. are also included in the report.
Foundation design is impossible without soil test. Without proper foundation design there is a possibility of settling or relocating the installation which may later cause damage or threat to the installation causing cracks or fissures. Again, in areas where the soil is weak, soil testing is required to properly design the piling. Proper piling is required to prevent the effects of earthquakes.
How to do Soil Test?
In our country, soil boring method is usually used for soil investigation. In this method, a 2 inches diameter pipe is hammered into the soil with the help of water. Soil samples and strengths are counted every 5 feet or 1.5 meters.
The value of N has to be recorded when the next 1.5 feet or 16 inches of pipe is inserted into the soil every 5 feet, but the number of slashes for the first 6 inches out of these 16 inches is not taken into account.
Therefore the number of slashes needed to enter the next 12 inches is the value of N. If we need 15 slashes to insert 12 inches, then the value of N will be 15. The value of N varies depending on the soil layer, as the value of N in the first 10-15 feet is very low.
If the value of N is above 15, then it means hard soil layer.
What are the precautions while doing soil test?
- Make sure the hammer weights is 63.5 kg and is dropping from a height of 30 inches?
- In every 5 feet collect the soil sample in different packets.
- Is N Value being counted and recorded accurately
- Even if the soil is good, it is better to collect samples up to at least 60 feet
Methods of soil test on site:
- To inspect and survey the site or plot.
- Select the boring number and location according to the condition of the field and complete the boring work accordingly.
- Determine the boring depth as needed.
- Collect intact and degraded soil samples at each boring site and test in laboratory.
- Determining the S.P.T value of soil at 5 feet intervals by boring or drilling and finding out the safe bearing capacity of the soil.
- Finding results in field tests and lab tests as well.
- Finally make a final report of the soil test and comment on the foundation of the construction accordingly.
Soil tests are usually two types
1. Soil field test
(A) Plate Load Bearing Test: This is a simple machine operation method by which the final bearing capacity and soil compression at any level of soil can be measured or determined. Moreover, the results determined by this test can be compared and verified.
(B) S.P.T Test: S.P.T (S.P.T = Standard Penetration Test) is used to determine the value of soil’s N value as well as the soil collation for the laboratory test. N Value gives direct direction to the bearing capacity of the soil.
Note: The bearing capacity of soil can be determined and tested directly in the field with the help of S.P.T value.
2. Soil Lab Test:
According to the ASTM Soil lab tests are usually as follows:
- Moisture content test
- Plasticity test
- Relative importance test
- Density test
- Consolidation test
- Direct share test, etc.
Who will do Soil Investigation and Provide Soil Test Service?
- Who have their own labs and
- There are experienced soil engineers.