where T is the shear force along the shear plane; N is the true normal force on the shear plane; P is the externally applied force on the top plate in the normal direction (usually recorded during the test); F is the shear force measured with the load cell; W is the dead weight of the specimen inside the shearing frame, and are the dead weights of the shearing frame and the loading plate, respectively; and 1W2W1F1P are the frictional and vertically supportive forces on the contact plane between the shearing frame and the specimen, respectively; A is the area of the shear plane (shearing frame); and σ and τ are the normal and shear stresses on the shear plane, respectively. In the above equations, P, W, , , A and F are measurable, while 1W2W1P and are close to zero and may be neglected since the vertical force is not applied directly to the ribs of the shearing frame and the shearing frame nearly floats above the shear plane when the sample dilates. As a result, the true stresses 1Fσ and τ on the shear plane are more accurately measured in this