Abstract: To research the formation and variation mechanism of the additional load, a mathematical model of the additional load is established, and the differential and integral formula of additional load are derived. The main factors which affect the additional load are obtained, such as pressure in adaptive base, horizontal projected area of upper face, and horizontal projected area of touchdown zone. The theoretical formula of additional load is verified by the numerical model. The analytical solution is well consistent with the numerical solution, and the relevant error is less than 1.9%. The relationship between the integral area and the expression form of the additional load is studied according to the integral formula of the additional load. The results indicate that there exists corresponding relationship between the direction of the additional load and the kind of the integral area, and that situation of that the direction is opposite in some areas may happen. When the ground subsidence is small or the shear failure exists in some area, the additional load may stays the same. When the ground subsidence is large, the amplitude and direction of the additional load may change.

Key words: applied mechanics, drape ejection, adaptive base, additional load, variation mechanism