Direct shear instrument with linear guidway

The utility model relates to a direct shear apparatus to measure the shearing strength of the soil sample. The direct shear apparatus with a straight line rack comprises an upper case (6) and a removable lower case (10); the lower case is fixed to the base (2), and the base is fixed to the straight line rack (12). Owing to the fact that the lower case is fixed to the straight line rolling guide and the rolling guide is a new-fashioned machine element with a high precision and a low friction, the precision of the shearing force test is guaranteed in terms of structure.