In-Situ Density Test
Concept
The In-Situ Density Test, also known as the Sand Cone Test or Sand Replacement Test, is a widely used field method for determining the in-situ (on-site) density of compacted soils or uncompacted soils. This test is particularly important in geotechnical investigations and construction projects as it provides valuable information about the compaction quality of soil, which is crucial for ensuring the stability and bearing capacity of foundations, embankments, and other earthworks structures.
Figure 1: In-Situ Density Test Equipment.
Procedure
The test is typically performed in accordance with standards such as ASTM D1556 or BS 1377-9. The following is a general procedure for conducting the In-Situ Density Test:
1.Test Location Preparation:
- Select a representative and level area for the test.
- Remove any loose material or vegetation from the test location.
- Expose a flat, horizontal surface of undisturbed soil.
2.Equipment Setup:
- Assemble the necessary equipment, which typically includes a sand cone apparatus (consisting of a cone-shaped container with a known volume and a detachable valve), a plastic sheet or ground cover, a digging tool (e.g., a shovel or an auger), a balance or scale, and a calibrated container for the sand.
3.Excavation:
- Place the plastic sheet or ground cover around the test location to catch any spilled material.
- Carefully excavate a hole in the soil, ensuring that the hole extends slightly beyond the base of the sand cone container.
- Collect and weigh the excavated soil from the hole to determine its moist mass.
4.Sand Pouring:
- Clean and dry the sand cone apparatus, ensuring no moisture or foreign material is present.
- Place the sand cone apparatus on the excavated hole, ensuring it is level and firmly seated.
- Pour the calibrated sand from the container into the sand cone apparatus until it is filled.
- Carefully remove the sand cone apparatus, allowing the excess sand to fall onto the plastic sheet or ground cover
5.Measurements and Calculations:
- Weigh the mass of the sand that was poured into the hole.
- Calculate the in-situ density of the soil using the following formula:
In-Situ Density = (Mass of Excavated Soil) / (Volume of Sand Cone)
If required, determine the moisture content of the soil by drying a representative sample in an oven and calculating the mass loss due to moisture evaporation.
Correct the in-situ density value for moisture content, if necessary, to obtain the dry density of the soil.
The In-Situ Density Test provides valuable information about the compaction quality of the soil, which is essential for various geotechnical applications, such as:
Evaluating the suitability of compacted soil for construction projects, including foundations, retaining walls, and embankments.
Monitoring and controlling the compaction process during construction to ensure that the desired density and bearing capacity are achieved.
Assessing the settlement potential of the soil, which is critical for the stability and performance of structures.
Determining the strength and deformation characteristics of the soil, which are necessary for geotechnical design calculations.
It is important to note that the In-Situ Density Test should be performed at multiple locations within the site to account for potential variability in soil conditions. Additionally, proper sampling and testing procedures, as specified in the relevant standards, should be followed to ensure accurate and reliable results.