Soil Cone Method

Some of the early theories to determine the net ultimate uplift capacity Q _u were restricted to shallow circular plate anchors. Mors (1959) proposed that the failure surface in soil at ultimate load may be approximated as a truncated cone having an apex angle of ? = 90 + ?/2 as shown in Figure 2-3. The net ultimate uplift capacity may be assumed to be equal to the weight of the soil located inside the failure surface. Thus

Figure 2-3: Mors' theory soil cone method ( Note: ? = 90 + ?/2; h = diameter of anchor plate)

However

Or

It needs to be pointed out that the shearing resistance developed along the failure surface has been neglected in Equation (2-2).

A similar theory was also proposed by Downs and Chieurzzi (1966),who suggested that the apex angle ? be taken as being equal to 60 as shown in Figure 2-4. For this case

Figure 2-4: Downs and Chieurzzi's theory soil cone method ( Note: h = diameter of anchor plate)

Friction Cylinder Method

In many cases in the past, the friction cylinder method was used to estimate the uplift capacity of shallow circular anchor plates. In this type of calculation, the friction surface in the soil was assumed to be cylindrical as shown in Figure 2-5a. For cohesionless soils,...