The soil has to take the weight of the structures. The soil testing before construction is the first step and important step for pre-construction. Soil testing is primarily done to test the bearing capacity of the soil. It also shows the physical and chemical composition of the coil. These characteristics may vary from layer to layer of the same soil. The characteristics of the soil can change within a small area due to weather, climate change and the management of the site can also change the bearing capacity of the soil. Failure to test site soils adequately and correctly can cause critical levels of financial and safety risks. It is therefore very important to understand the soil properties and make use of the acquired information in the planning and designing of the project phases. The soil must be able to withstand the weight of the building otherwise the loss of property and life can occur. The soil investigations or analysis determines not only the bearing capacity of the soil but also the rate of settlement of the soil. This rate determines the rate of the structure stabilization on the soil.
What does Pre-Construction soil testing determine?
- The depth and length of the pillars that will be inserted into the soil to lay the building’s foundation
- The selection of suitable construction techniques and knowing the possible foundation problems all are based on the results of the soil testing
- The choice of construction material may also be affected by the chemical and mineral composition of the soil
- The water level of the soil only can be determined from soil testing. Based on the soil testing reports quality of material can be decided.
- The likelihood of foundation problems and the best construction methods to use
- Indicates potential issues with the level of humidity inside the foundation and the foundation of the building
- Specifies the Soil reactivity that is how the soil reacts to certain conditions on-site, such as whether it expands, contracts, or moves.
- The height of the building and the use of materials are decided by the engineers based on soil testing reports
- The requirement of soil stabilization is determined
- Identify soil liquefaction
Different types of pre-construction soil testing
There are several different types of pre-construction soil testing. The type of test depends on the properties of the soil. Some tests are conducted at the construction site while others are done in the laboratory.
Moisture Content Test
The moisture content of the soil is determined using several methods, including the oven-drying method, calcium carbide method, torsion balance method, Pycnometer method, sand bath method, radiation method, and alcohol method.
Specific Gravity Test
It is the ratio of the unit weight of soil solids to that of the water. It is determined by many methods such as the Density bottle method, Pycnometer method, Gas jar method, Shrinkage limit method and Measuring flask method. The dry density of soil is the weight of soil particles in a given volume of a sample. Its value depends on the void ratio and the soil’s specific gravity.
Dry Density Test
It is the weight of soil particles in a given volume of a sample. Its value depends on the void ratio and the soil’s specific gravity. This value is used to classify soil as dense, medium dense, or loose. The dry density test is done using one of three methods: sand replacement, core cutter, or water displacement.
Dry Density Test in Soil is performed with two methods, Core Cutter Method and Sand Replacement MethodCore Cutter Method is carried with the help of cylindrical core cutter of standard dimension is used to cut the soil from ground and the sample is tested by weighing it. Water content from that sample is determined and the dry density is calculated. Sand Replacement Method is done by excavation a hole is created and the soil dry density to be measured with it. The hole is filled with uniform sand of known dry density. Dividing the mass of sand poured into the hole with the dry density of sand gives the volume of hole.
Proctor’s Compaction Test
The Proctor compaction test is a laboratory method of experimentally determining the optimal moisture content at which a given soil type will become most dense and achieve its maximum dry density. These laboratory tests generally consist of compacting soil at known moisture content into a cylindrical mold with a collar of standard dimensions of height and diameter using a compactive effort of controlled magnitude. The soil is usually compacted into the mold to a certain amount of equal layers, each receiving several blows from a standard weighted hammer at a specified height. This process is then repeated for various moisture contents and the dry densities are determined for each.
Atterberg Limits Test
The Atterberg limits are a basic measure of the critical water contents of a fine-grained soil: its shrinkage limit, plastic limit, and liquid limit. Depending on its water content, soil may appear in one of four states: solid, semi-solid, plastic and liquid. In each state, the consistency and behavior of a soil are different and consequently so are its engineering properties. Thus, the boundary between each state can be defined based on a change in the soil’s behavior. The Atterberg limits can be used to distinguish between silt and clay, and to distinguish between different types of silts and clays. The component for testing is done with fine-grained soil and if any critical component from water is present then it can be determined with it. The three limits that are evaluated are Liquid Limit, Plastic Limit and Shrinkage Limit.
Liquid limit is measured by placing a clay sample in a standard cup and making a separation (groove) using a spatula. The cup is dropped till the separation vanishes. The water content of the soil is obtained from this sample. The test is performed again by increasing the water content.
In this test, small balls need to be created by adding some water to them. After resting it for some time the small balls are put into a glass plate and rolled to 3mm diameter. Until the threads break when it rolled into a diameter that is less than 3mm water content is to be reduced. It is to determine the water content of resultant soil whose value is nothing but plastic limit.
A shrinkage limit test gives a quantitative indication of how much moisture can change before any significant volume change and also an indication of volume change. The shrinkage limit is useful in areas where soils undergo large volume changes when going through wet and dry cycles
Discussed above are different types of pre-construction soil tests that can help you save a lot in the cost of laying the foundation and ensure a safe, stable, and strong base for your construction project. Soil testing must be done by experts and methods must be selected based upon analysis of experts. Thus, before beginning any construction work, investing in soil testing for a safer future.