Direct shear testing is a geotechnical laboratory test used to determine what are referred to as soil strength properties – namely the cohesion and angle of internal friction of the soil. From these parameters, an engineer can determine soil bearing capacity, predict how the soil will interact with vertical structures (such as shoring, retaining walls, deep foundations), and estimate frictional resistance to sliding. The test is performed by obtaining a set of intact or compacted soil rings, consolidated to different over-burden pressures. The sample is then placed in a submerged mold that is split horizontally, and the top half of the sample is slowly pushed across the bottom half. The resistance pressure of the soil to this movement is recorded at frequent time intervals to determine the displacement distance at the peak level of resistance.
