The main purpose of this test is to determine the unconfined compressive strength, qu, by subjecting a cylindrical soil specimen to rapid compressive loading so that no drainage takes place during the shear. In this test method, the unconfined compressive strength is defined as the maximum load attained per unit area, or the load per unit area at 15% axial strain, whichever occurs first during the test. The unconfined compressive strength, qu, is then used to calculate the undrained shear strength, cu=qu/2, of the fine-grained soil.
To determine the undrained shear strength (cu) of fine-grained soil.
British Standard 1377 – Part 7: Shear strength tests (total stress) ASTM D 2166 - Standard Test Method for Unconfined Compressive Strength Of Cohesive Soil
1) Compression device with proving ring
2) Dial gauges
3) Sampling moulds and trimming equipments
1) Prepare a specimen with 38mm diameter and 76mm height from the sampling moulds.
2) Carefully place the specimen in the compression device and center it on the bottom plate.
3) Adjust the device so that the upper plate just makes contact with the specimen and set the load and deformation dials to zero.
4) Apply the load so that the device produces an axial strain at a rate of 0.5% to 2% per minute, and then record the load and deformation dial readings on the data sheet at every 20 divisions on deformation dial.
5) Keep applying the load until i) the load decreases significantly, or ii) the load holds constant for four continuous readings, or iii) the deformation exceeds 15% strain.
6) Draw a sketch to depict the sample failure.
7) Repeat the test procedures (2) to (6) for the second soil specimen.
Results and Calculations
Sample | A |
Container (g) | 35 |
Container + wet soil (g) | 212 |
Container + dry soil (g) | 186.7 |
Dry soil (g) | 151.7 |
Wet soil (g) | 177 |
Water (g) | 25.3 |...