Whether small and simple or large and spectacular, bridges are a fascinating sight and an essential junction point that expands the transportation network and supply chain. Depending on the locations and uses, the bridges may be subjected to various types of loads that necessitate solid foundations for their stability and durability. This makes soil testing critical for bridge construction
What is a Soil Test for Bridge Construction?
Testing of Soil is all about examining the soil quality and bearing capacity to justify the structure of the bridge, the materials used, and the expected traffic load on it.
Soil testing is performed by a geotechnical expert who checks soil samples to determine the characteristics, nature, and reactivity of soil. Soil type and quality vary greatly from area to area. They can be sandy and porous, rocky, or waterlogged. Not all soil types are suitable or maybe even dangerous for construction.
The test of soil clarifies which types of structure and how much load of structure can be constructed on the given types of soil. If the soil isn’t fit to hold the type of structure you’re planning to build, it won’t only affect its stability. It can also lead to costly repairs, or worse, fatal accidents.
Why is Soil Testing Necessary for Construction?
To test the soil’s ability to sustain the expected maximum load of the proposed bridge, dam or building, The chemical and physical composition of the soil is also analyzed by using some chemicals in the lab. For numerous reasons, soil testing is essential prior to the construction of any infrastructure:
To learn the characteristics of the soil:
Soil testing assists in determining the type and qualities of soil present at the construction site. This covers its composition, strength, density, water content, and other factors that can affect the construction process and infrastructure stability.
To determine the appropriateness of the soil:
Soil testing can be used to determine whether the soil is acceptable for the proposed construction. For example, if the soil is too weak, unstable, or compressible, it may be unable to hold the weight of the infrastructure or may cause settlement, resulting in structural damage.
To optimally design the foundations:
Soil testing assists engineers in designing acceptable infrastructure foundations. Engineers can identify the sort of foundation necessary, its depth, size, and shape, as well as the materials that should be used, based on the soil parameters.
To ensure safety:
Soil testing is critical for ensuring the safety of infrastructure and those who utilize it. If the soil is not examined, structural failure might occur, resulting in injury, loss of life, and property damage.
To prevent cost overrun:
Soil testing can also help you save money by eliminating needless excavation or foundation work, as well as costly repairs or adjustments in the future.
Overall, soil testing is an important phase in the construction process that ensures the safety, stability, and longevity of the constructed structure.
Who performs Soil Testing?
Soil engineers or geotechnical engineers are the people who are eligible to do soil testing. A geotechnical engineer is a professional who investigates the surface and subsurface state of the earth using fundamental concepts of soil and rock mechanics.
This enables them to evaluate, design, analyze, and examine factors like stability of natural slopes, man-made soil deposits, earthworks with cuts and fills, shallow and deep foundations, dams, retaining walls, tunnels, bridges, underground structures, and a variety of other works that interact directly with subsoil and water.
You can hire them privately or ask your architect for recommendations. Soil testing is also provided as a separate service by some construction businesses.
Types of Soil Test for Bridge Construction
The soil engineer must examine a number of aspects when determining soil quality for the construction. Therefore, depending on the geological features of the location, they frequently undertake different types of soil tests. The most important soil tests are as follows:
1. Atterberg Limit Test
Atterberg limit test determines at what moisture level the fine-grained soil transitions take place between different states, such as solid, semi-solid, plastic, and liquid. It was named after Albert Atterberg, a Swedish chemist and scientist. He found that when a soil’s moisture level increases, so does its consistency.
The test measures three different kinds of limits: plastic limits, liquid limits, and shrinkage limits. Soil engineers use the test results to predict how the soil will behave as the moisture level changes.
2. Specific Gravity Test
The specific gravity of soil is defined as the ratio of solid particles to water content. It is calculated by dividing the weight in air of a certain volume of soil particles by the weight in air of an equal volume of distilled water at the same temperature.
The findings of this test can assist engineers in determining the mineral composition and weathering of the soil. It can also be used to determine the porosity, degree of saturation, and dry and saturated density of the soil.
3. Moisture Content Test
Besides solid particles, soils in different areas contain different amounts of water. The moisture content test determines how much water is present in the soil, which can have an impact on its stability.
There are several methods for testing soil moisture content. The Oven-Dry Method is the most prevalent. The raw dirt is weighed before being placed in the oven to dry. After all of the water has evaporated, the dirt is removed and reweighed. The moisture content is then estimated by subtracting the weight of the wet soil from the weight of the dry soil.
4. Dry Density Test
A dry density test is performed to calculate the quantity of moisture required for maximum compaction of the soil. Soil compaction is required to increase the bearing capacity and stiffness of naturally occurring or chemically changed soils. Compaction increases soil shear strength by increasing friction caused by particle interlocking.
The degree of compaction necessary for the soil in the relevant area varies. Compaction tests are performed in the laboratory on soil from the site to establish the amount of compaction required by the soil and the appropriate water content for compaction.
The Standard Proctor Compaction Test and the Modified or AASHTO Proctor Test are the two methods for determining a soil’s maximum density.