The ultimate static pile capacity can be combated as follows: Where Ap = Area of pile point effective in bearing. c = Cohesion (or undrained shear strength Su) B = Base width of pile. = Bearing capacity factor for cohesion adjusted N′c for shape and and Nc is often depth. When Φ=0, we have c=Su taken as 9. = Bearing capacity factor for overburden effect N′q and include shape and depth effects. = Bearing capacity factor for base width. N′r = Effective vertical stress (overburden pressure) at pile point. The is usually neglected as the pile base width B is not large. It may not be N’r term neglected where an enlarge pile base is used. Neglecting the N'r tern, the pile capacity can be computed as: ) This equation gives for c=Su and the = 1 and ultimate point capacity is: Φ=0, N′q The allowable pile capacity is obtained by dividing the ultimate capacity by a suitable safety factor which usually varies between 2.5 and 4. Meyerhof (1951, 1976) has proposed bearing capacity factors and as shown in N′c N′q Figure 7-2. The factor incorporate the effect of shape and depth effect (e.g., from Nq to and N′q Nc to Meyerhof used a critical depth ratio Lc/B which basically means that if the N′c). embedment depth exceeds the critical depth ratio, the bearing capacity reaches a limiting value. The limiting point bearing in cohesionless soil is given for L/B > Lc/B as: Meyerhof also uses 9Su as the limiting resistance for clay (ϕ=o). To determine Meyerhof N factors from Figure 7-2, proceed as follows: Compute R1 =L/B and obtain R2 =Lc/B from the critical depth curves at the given angle of figure 7-2. ϕ
The ultimate static pile capacity can be combated as follows: Where Ap = Area of pile point effective in bearing. c = Cohesion (or undrained shear strength Su) B = Base width of pile. N′c = Bearing capacity factor for cohesion adjusted for shape and depth. When Φ=0, we have c=Su and Nc is often taken as 9. N′q = Bearing capacity factor for overburden effect and include shape and depth effects. N′r = Bearing capacity factor for base width. = Effective vertical stress (overburden pressure) at pile point. The N’r term is usually neglected as the pile base width B is not large. It may not be neglected where an enlarge pile base is used. Neglecting the N'r tern, the pile capacity can be computed as: ) This equation gives for c=Su and Φ=0, the N′q = 1 and ultimate point capacity is: The allowable pile capacity is obtained by dividing the ultimate capacity by a suitable safety factor which usually varies between 2.5 and 4. Meyerhof (1951, 1976) has proposed bearing capacity factors N′c and N′q as shown in Figure 7-2. The factor incorporate the effect of shape and depth effect (e.g., from Nq to N′q and Nc to N′c). Meyerhof used a critical depth ratio Lc/B which basically means that if the embedment depth exceeds the critical depth ratio, the bearing capacity reaches a limiting value. The limiting point bearing in cohesionless soil is given for L/B > Lc/B as: Meyerhof also uses 9Su as the limiting resistance for clay (ϕ=o). To determine Meyerhof N factors from Figure 7-2, proceed as follows: Compute R1 =L/B and obtain R2 =Lc/B from the critical depth curves at the given ϕ angle of figure 7-2.
7introduction_to_deep_fnd.docx