One of the main factors that influence the analytic results of slope stability is the determining of mechanical parameters. When the least square method is adopted as the method for determining the rock shear strength parameters, its precondition that the observation errors exist only in one observation variable is always being neglected. By analysis, the calculating of shear strength parameters is divided into three kind of situations, and a new approach to calculate the shear strength parameters is obtained according to the fact that the quadratic sum of distance between line and points in minimum, and the calculating formulae and applying scopes of three different calculating methods are also put forward. A calculating case shows that there are obvious differences among different calculating methods for determining the strength parameters, and it is necessary to select the calculating method based on the observation errors.
Reconciling soil-water retention properties and shear strength parameters of compacted clayey soils via suction-controlled ring shear testing