What Does In-Situ Resistance Mean?
In-situ resistance in the context of in-situ stress for the soil being tested can be defined as the resistance offered by the soil in its current state. The dynamic cone penetration test and static cone penetration test methods give a measure of the in-situ resistance of soil to penetration.
This method can help determine the strength of in-situ soil and depth and thickness of sub-surface soil layers. Geotechnical investigation is an important part of trenchless technology that helps understand soil characteristics important to successful pipeline installation.
Trenchlesspedia Explains In-Situ Resistance
Measuring in-situ resistance in the field is advantageous because it provides information about the soil in its natural or undisturbed condition. The static cone penetration test is best performed in soft clay, silt, medium, and fine sands. The test is performed by pushing the standard cone with a base area of 10 cm2 and an angle of 60°, into the soil at a rate of 10 to 20 mm/sec. After installation, a sounding rod is pushed into the soil at a steady rate of 10 mm/sec in order to advance the cone and readings are noted in the gauge at regular depth intervals.
The dynamic cone penetration test is performed by driving a cone into the ground by repeated blows with a standard weight dropped from a standard height. The penetration of the cone is measured after every blow and recorded.
For harder soil, the reading may be noted after a certain number of hammer blows. The standard cone size is 20 mm diameter and angle of 60°, with the hammer having a weight of 8 kg.