Soil Testing For Construction
Soil testing is a very important part of building and road construction. In fact, no construction project can proceed without first making sure the soil can support the load. Thus, the purpose of soil testing for construction is to determine the suitability of the soil for the type of construction to be done. The test is also done to determine the presence of groundwater.
Types of soil tests for construction
There are several different types of preconstruction soil testing. The type of test depends on the properties of the soil. The design of the foundation is based on the soil test report. Some tests are conducted at the construction site while others are done in the laboratory.
Moisture Content Test
This is a very important test for building construction. 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. The most common method is the oven-drying method, which involves weighing the sample soil, drying it in an oven at a 110 degrees Celsius (+/- 5 degrees), and weighing it again. The difference in the before and after weights is the weight of water in the soil.
Specific Gravity Test
The specific gravity of any substance is the ratio of density to the density of the water. It is determined using one of several methods that include the density bottle method, Pycnometer method, gas jar method, shrinkage limit method, and measuring flask method. Of these, the most commonly used in soil analysis are the density bottle and Pycnometer methods.
Dry Density Test
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. 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. Of these, the sand replacement and core cutter methods are the more widely used.
Atterberg Limits Test
This test is done on the fine-grained soil to measure its critical water content. There are three limits that determine the properties of fine-grained soil under different conditions: liquid limit, plastic limit, and shrinkage limit.
a. In a liquid limit test, a device called a Casagrande’s liquid limit device, which consists of a cup with a mechanism that moves up and down is used to determine the soil’s liquid limit.
b. In a plastic limit test, water is added to the soil sample to make it plastic. It is then shaped into a ball, which is put into a glass plate and rolled into threads that are 3 millimeters in diameter. If the threads do not break, then the procedure is repeated with a new sample and less water. It goes on until the thread breaks. That is the plastic limit of the soil.
c. In a shrinkage limit test, a mathematical formula is used to determine the water content that is just enough to fill the voids of the soil.
Proctor’s Compaction Test
This test is conducted to find out the compaction characteristics of the soil. The soil sample is air dried and then divided into four to six smaller samples. Their water content is adjusted by adding 3 percent to 5 percent water. The samples are then placed in the Proctor compaction mold in three different layers. Each layer is then given 25 blows from a standard 5.5-pound hammer. The samples are removed and dried, and their dry density and water content are determined. A curve is then plotted based on the entire set of results – with the density as a function of water content. This curve gives an accurate picture of the optimum water content needed to reach the maximum dry density.
When taking samples, remember a soil test is only as good as the sample you take. Therefore it is important to hire a professional highly experienced environmental company to handle your soil testing for construction. One that specializes in groundwater and soil testing, investigation, assessment, and remediation. All American Environmental is that company! We are located in Lake Hopatcong, NJ and provide complete soil testing for construction services throughout northern NJ. Contact All American Environmental, NJ