Are you studying civil engineering and intend to do soil analysis? You have come to the right place.
Here we will tell you things that you must do in such study. As we know, the soil is very useful in our life. People use it mainly for growing plants or construction.
The soil itself contains materials like aggregate, minerals, and other organic stuff that have been molding as time goes by. Besides those things, it also has liquid and gas filling the empty space. In order to use soil for activities like farming, gardening, or building, it is important to analyze the soil first. By that, people will understand if there is something wrong with it when they are using it.
Without further ado, here are some processes you can do in soil analysis.
1. Taking a Sample
When you want to take a sample of soil, you need to look for a place where its soil is in good condition, not from the piling. When you have found it, the next thing you must check is the weather. It is better to take a sample during sunny weather. Otherwise, it will affect your sample.
There are some simple steps in doing this first stage. At this point, there are 2 kinds of sample required. One is disturbed soil, and the other is non-disturbed soil.
First, dig the soil in two different areas and take a sample from each.
Second, for the disturbed soil, conduct a drying process to release the water content. You can do it by letting it be exposed to the sun or putting into the oven.
Third, once it is dry, knock it with a hammer so the piled-up particle can break apart and slip through the filtering.
After everything is done, put the disturbed soil into a sack. On the other hand, put the non-disturbed one into a plastic. It aims to prevent it from water evaporation. Then, keep them both in a place where the weather will not affect them.
2. Water Content Testing
We already have a sample for this soil analysis. Now there are several tests we need to perform. The first one is water content test. From this test, we will know the amount of water contained in a certain soil. To do this part, we must prepare a container, scale, oven, desiccator, and non-disturbed soil.
First, insert the sample into the container.
Second, put it into the oven and set the temperature and timer. The temperature must be at 110°C, while the time is at 24 hours.
Third, when the time is over, take the sample out and put it into a desiccator. Last, after 1 hour passed, you may begin to weigh it and then measure the water content.
3. Unit Weight Testing
The second test is unit weight testing. The purpose is to determine the amount of soil weight and compare it all with the weight of the fill inside the soil. The equipment we require for this test is a cylinder ring, calipers, ground blades, scale, spatula, and non-disturbed soil.
First, measure the height of the cylinder ring as well as its diameter. Then, weigh it on a scale. After that, cover the ring with oil on the inside and put the soil into it. Flatten the surface either with a knife or spatula. Last, weigh the ring again with the sample inside.
4. Specific Gravity Testing
The third test is also about weight measurement, but this time we intend to measure specific gravity. It is a ratio between soil particle weight with the volume of solid ground or water weight which have the same content with the solid ground at a certain temperature. Through this test, we will reveal the ratio. For that purpose, we need a container, pycnometer, oven, thermometer, scale, filter number 4, distilled water and aqua dest, rag cloth, and soil that can slip through the filter.
First, put the sample into the oven for 24 hours. When it is done, knock it to make it soft and filter it with the number 4.
Second, weigh the pycnometer without soil inside it.
Third, weigh it again, but this time with the sample inside it.
Fourth, pour enough aqua dest into the pycnometer, put it to the desiccator and turn it on. At this point, you must watch it until the air is completely out of the pycnometer. You may shake it while vacuuming it as needed until there is no more air inside it. Once the process is done, leave it be until the soil sediments.
Fifth, pour more aqua dest carefully and then measure the temperature. Sixth, dry the outside of the pycnometer and weigh it. Seventh, empty it, wash it cleanly, and fill it with aqua dest fully. Last, measure the temperature, weigh it, and done.
5. Liquid Limit and Plastic Limit Testing
In this soil analysis testing, we will do two tests at one time, which are liquid limit and plastic limit. When we shake soil, and it shows some cracks, that means it is in a plastic condition. In contrast, if it does not have cracks, it means it contains much water. Let’s start with a liquid limit test. What we need here is Casagrande, grooving tools, scale, oven, container, softer soil which slips through filter number 4 and dried bigger soil.
First, put 200g of the sample on a glass platform, add a bit water, and stir it well. Second, set the height of the bowl of Casagrande for about 10mm. Put a part of a sample on it until the bowl is even with the tool. Third, push the grooving tool onto the soil and set it upright with the soil. Fourth, twist the handle twice until each sample unites around 13mm and note the number of blows.
If it is more than 10 or 50, stir it again so the water evaporates. Fifth, take some united soil to a container, dry it with an oven, and find the water content. Last, repeat the steps above with the rest of the soil to find different levels of water content with different blow numbers.
For the plastic limit, you can prepare platform glass, spatula, scale, oven, container, straw, distilled water, and same sample with a liquid limit test.
First, put the sample onto platform glass and stir it until the water spread out evenly. Second, put a 1-cm-diameter marble on the glass and scroll it with our palm with speed 80-90 rolls/minute. Roll it until the soil shapes like a 3-mm-diameter stick. If it already breaks before that, unites the sample, add more water, and stir it again. Last, once it has that shape with thin cracks, take the sample, put it into a container and count the water content.
These are only a few processes you can perform in soil analysis. You may also do some more of them like sieve and hydrometer analysis, compaction test, and also California Bearing Ratio (CBR). By studying this, you can teach other civil engineering students to learn how to do soil analysis properly. In addition, you can also help people whose jobs are related to the soil (e.g. farmer, contractor, or gardener).