The specimen is placed in a cell (Casagrande box) consisting of two half-boxes to allow the upper part to slide over the lower part. The test is carried out on at least three specimens belonging to the same soil sample, previously consolidated at three different pressure values. At the end of the consolidation phase we proceed with the cutting phase, under drained conditions, recording the resulting effort. Three different values of shear strength are obtained, proportional to the three different consolidation pressures applied. The values obtained are used to estimate the break envelope in the σn-τ diagram.