The rubber balloon test method is a widely used in-situ test for measuring the field density of compacted soils. This method involves the use of certain apparatus, a specific test procedure, and calculations to determine the density of the soil in question.
To conduct the rubber balloon test, the necessary apparatus must be gathered beforehand. This includes a rubber balloon, a measuring tape, a stopwatch, a balance, and a cylindrical metal calibrating container. The test procedure involves filling the metal container with the soil sample, compacting it in three layers, and weighing the container with the compacted soil. The next step is to measure the volume of the metal container and calculate the bulk density of the compacted soil. Then, a small portion of the compacted soil is taken out and placed into the rubber balloon, which is then inflated until it bursts. The volume of the balloon at the point of bursting is then measured and the density of the soil is calculated using this measurement.
In conclusion, the rubber balloon test method is an effective way of determining the field density of compacted soils. By following the necessary test procedure and calculations, accurate measurements can be obtained using the required apparatus.
Field Density of Soil by Rubber Balloon Method
The rubber balloon test is a fast and precise in-situ method that is commonly used to determine the volume of excavated soil holes. By employing rubber balloons, this method is able to yield more accurate results than other similar techniques. However, the suitability of the rubber balloon test is dependent on the type of soil being tested. Specifically, the test is most appropriate for well-compacted soils. In contrast, for soils that are very soft and prone to deformation, the rubber balloon method is not recommended.
Apparatus Required
The balloon density meter is a device used to measure the density of soil. It consists of several components, including a rubber bulb pump, a density plate with fasteners, rubber balloons, a soil augur or trowel, a moisture tight container, a weight balance, and a drying oven.
The rubber bulb pump is used to inflate the rubber balloons, which are attached to the density plate with fasteners. The density plate is then inserted into the soil using a soil augur or trowel, ensuring that it is tightly secured in place. The rubber balloons are inflated to a predetermined pressure, and the density of the soil is calculated based on the volume of the balloons and the pressure inside them.
To obtain accurate measurements, the soil sample needs to be placed in a moisture tight container to prevent any moisture loss or gain during the testing process. The weight balance is used to measure the mass of the soil sample, density plate, and balloons before and after the test. The drying oven is used to dry the soil sample to a consistent moisture content, as the moisture content of the soil can affect its density.
Overall, the balloon density meter is a useful tool in geotechnical engineering and soil science for determining the density of soil in various field and laboratory testing applications.
Fig 1: Rubber Balloon Apparatus
The balloon density meter is designed in a cylindrical shape and features graduations on its wall for measurement. At the bottom of the density meter, a thin membrane made of rubber is attached. This membrane acts as a balloon that expands when water is pumped into it using a control valve and rubber bulb arrangement. The rubber bulb pump, also known as a pressure and vacuum pump, is used to apply pressure or relieve pressure from the rubber balloon, allowing for precise control of the water pressure inside the density meter.
Rubber Balloon Test Procedure
The rubber balloon method is used to determine the field density of soil. The test procedure involves several steps, beginning with preparing a flat and smooth surface on the field where the density needs to be found. Once the surface is ready, a density plate is placed on it and fixed in place using fasteners. The plate should remain stable during the test.
Next, the balloon density meter is positioned exactly on the hole provided in the density plate. A rubber bulb pump is then used to pump water into the balloon at the bottom of the density meter until the water level reaches its lowest position. The reading at this point is recorded as the initial volume (V1).
After the initial volume is recorded, the rubber bulb pump is inverted, and the water is pumped back into its original position. The density meter is then removed, and a hole is dug using an auger or trowel. The excavated soil is collected completely in a moisture-tight container, and its weight (W) is noted. This weight is also used to determine the water content of the soil.
The balloon density meter is then placed over the excavated hole, and water is pumped into the balloon using a rubber bulb pump. The water level is noted when it reaches its lowest position, and this reading is recorded as the final volume (V2). Finally, the water is pumped back into its original level using a rubber bulb pump with the vacuum side connected to the control valve.
Observations and Calculations
To calculate the dry density of the excavated soil, we need to first determine the weight of the soil excavated, which is represented by the variable W. We also need to calculate the volume of the hole excavated, which can be found by subtracting the final volume reading (V2) of the balloon density meter from the initial volume reading (V1), resulting in a value represented by the variable V.
Next, we need to determine the field density or wet density of the soil, which can be calculated by dividing the weight of the excavated soil (W) by the volume of the hole excavated (V). This will give us the wet density of the soil.
In addition to the wet density, we also need to know the water content of the excavated soil, represented by the variable w. Once we have this information, we can use it to calculate the dry density of the soil, which is given by the formula:
Dry density = wet density / (1 + w)
Therefore, by using the weight of the soil excavated, the volume of the hole excavated, the field density or wet density of the soil, and the water content of the excavated soil, we can calculate the dry density of the soil using the above formula.
Result
Field Density of soil is = _________ N/m3.