(1), unconfined compressive strength is the ultimate strength of the specimen to resist axial pressure without lateral pressure.
(2) This test is suitable for determining the unconfined compressive strength and sensitivity of saturated soft clay.
2. Test principle
Unconfined compressive strength test is a special case of triaxial test, that is, soil samples are subjected to pressure test without lateral constraints. At this time, the small principal stress of the soil sample is 0, and the limit value of the large principal stress is the unconfined compressive strength.
3. Instruments and equipment
(1) Strain-controlled unconfined compressor: It consists of dynamometer, pressurizing frame and lifting equipment.
(2) Axial displacement meter: a dial indicator with a measuring range of10mm and a dividing value of 0.0 1 mm. ..
(3) Balance: weigh 500g, and the dividing value is 0.1g..
4, operation steps
(1) Prepare undisturbed soil samples according to triaxial compression test procedures. The diameter of the sample is 39. 1 mm and the height is 80mm.
(2) Coat a thin layer of vaseline on both ends of the sample. When the climate is dry, apply a thin layer of vaseline around the sample to prevent water from evaporating.
(3) Put the sample on the base, turn the handwheel to make the base rise slowly, and the sample just touches the pressure plate, and adjust the dynamometer reading to zero. Choose dynamometer with different ranges according to the hardness of the sample.
(4) The axial strain rate should be 65438 0% ~ 3% per minute. Turn the handle to raise the lifting equipment for testing. When the axial strain is less than 3%, read it every 0.5% strain (or 0.4mm). When the axial strain is equal to or greater than 3%, read it every 1% strain (or 0.8mm). The test should be completed within 8 ~ 10 minutes.
(5) When the dynamometer reading reaches a peak, continue to apply 3% ~ 5% strain, and then stop the test; When there is no peak reading, the test shall be carried out until the strain reaches 20%.
(6) After the test, take down the sample and describe its damaged shape.
(7) When it is necessary to determine the sensitivity, immediately remove the surface coated with vaseline from the damaged sample. Add a little residual soil, wrap it with plastic film and knead it by hand, destroy its structure, reshape it into a cylinder, put it into a remodeling cylinder, and squeeze the sample into a sample with the same size and density as the original sample with a metal pad. Conduct the test according to the steps in this article 1 ~ 5.