Using Test Pits for Soil Exploration

Using Test Pits for Soil Exploration

Surface exploration can provide you with many clues about the stability of the ground. However, it doesn’t provide you with the full picture. For that reason, many contractors and engineers will utilize test pits for soil exploration.   

Just as the name would imply, a test pit is a hole dug into the ground that allows you to test the soil. They often aren’t very deep, but they provide great insight into the composition of the soil and its layers. Not to mention, a soil pit is one of the most affordable options for soil exploration.

That’s not all!

In this article, we’ll cover the purpose of soil testing so that you can better understand how a test pit is used. We also cover some of the different options for soil exploration methods so that you can compare them to test pits and trenches.

Purpose of Soil Exploration

Geotechnical engineers and contractors in New Jersey often want to explore the soil for safety reasons. They give you the opportunity to:

  • Look for Soil Properties That Could Impact Construction: When you explore soil, it’s important to look for any soft matter, such as clay or sand. These materials create instability. You should also look for sandy loam soil as it exhibits great drainage properties. 
  • Determine Materials for Construction: More often than not, you won’t find the perfect soil composition in your test pit. That’s okay, however. There are many ways you can adjust the type of construction materials to fit your land’s soil. Soil exploration allows you to see which materials will work best and the extent of adaptations you will need to make.
  • Locate and Check Groundwater Conditions: Groundwater can be a blessing when it’s in the right place and a curse when it’s in the wrong place. If you are building a home in an area with a high water table, you will have to be cautious of foundational issues and basement flooding. On the other hand, a water table can be great if you need to put in a well! 
  • Diagnose Cause of Existing Structural Failures: In some cases, soil exploration might be done after construction. If an existing structure shows signs of structural issues, including shifting or cracked foundation, you might need to examine the ground beneath it.

Soil Exploration Methods

When you are testing ground conditions, there are several factors you must consider. These factors can help you determine which tests to perform. They can also aid in making predictions about your soil and its stability. To make sure you get the most out of your soil tests, you should consider: 

Excavated Test Pits

Test pits are one of the most common methods of soil exploration. They are perfect for looking at shallow depths as they are simple and fast to dig. You can do so manually with the help of local labor. When done by hand, a test pit is one of the most economical soil exploration methods. In some cases, you may prefer to hire contractors to use heavy equipment excavation tools.

We also find this method especially useful because it allows you to observe the soil profile up close. You can easily see the variation in each layer, and you can examine the different materials. This view can help you diagnose any fill material that may pose a threat to the stability of the ground.

Auger Boring

If you need to reach more depth, auger boring is another option. It is a method used for shallow or deep collections. It is done by using an auger to drill into the soil. As it makes its way down into the ground, the auger fills with soil, and it brings the samples to the surface where soil experts can examine them.

While this method allows you to reach greater depths, it is more costly. Not to mention, the process causes a lot of disturbance while collecting the samples. That means that it can be challenging to see changes in the soil strata. Using this equipment can also be much more expensive than manually digging a pit.

Wash Boring

When dealing with softer materials like clay and sand, wash boring is the better option for soil exploration. The name comes from the jet stream of water sprayed through a hollow drilling rod. The fragments then separate from the water and collect in soil samplers attached to the bottom of the drill rod. 

This quick and straightforward method is relatively inexpensive. It’s perfect for gathering undisturbed soil samplings. You can even use it in areas with limited accessibility. For example, it’s ideal for testing in swamps or on water.

Percussion Drilling

The percussion drilling method is also known as cable tool drilling. It is often used to dig wells. However, it is also a popular method for examining soil in areas with boulders and rocks. You can even locate cavities and weaknesses in the rocks by comparing drill rate changes. It’s important to keep in mind that the blows of the chisel in percussion drilling cause disturbances to the soil at the bottom.

Rotary Boring

Lastly, you can use rotary boring. It is one of the fastest methods. Despite its speed, it doesn’t disturb the soil as much as some of the other methods. Unfortunately, the cost and bulkiness of the equipment deter contractors and engineers from using it. The drill also doesn’t do well with soil that contains large pieces of gravel.

Use a Test Pit to Explore Soil at Your NJ Construction Site

If you would like assistance with digging a test pit or trench, Mikula is happy to help. Our contracting company has over 75 years of experience with excavation services. Therefore, you can count on our experts to dig a safe test pit for you and your geotechnical engineering crew.  

To get started with your soil test pit excavation, give us a call. We are happy to schedule a consultation before we dig to discuss your soil testing needs. You can also reach out to our service representatives by submitting our online quote form.

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