Refer to Figure 11.26b. For the drilled shaft with bell, given:Thickness of active zone, Z = 9 mDead load = 1500 kN Live load = 300 kNDiameter of the shaft, Ds = 1 mZero swell pressure for the clay in the active zone = 600 kN/m2Average angle of plinth-soil friction, Φ'ps = 20°Average undrained cohesion of the clay around the bell = 150 kN/m2. Determine the diameter of the bell, Db. A factor of safety of 3 against uplift is required with the assumption that dead load plus live load is equal to zero. Dead load, DGrade beamGround surfaceUZActivezone, ZDrilled shaftswith bells- Dp(a)(b)Figure 11.26 (a) Construction of drilled shafts with bells and grade beam; (b) definition ofparameters in Eq. (11.14)

Shafts are the hollow pillars which are built inside the ground to support the construction over…

Dead load, D Grade beam Ground surface U Z Active zone, Z Drilled shafts with bells - Dp (a) (b) Figure 11.26 (a) Construction of drilled shafts with bells and grade beam; (b) definition of parameters in Eq. (11.14)

Dead load, D Grade beam Ground surface U Z Active zone, Z Drilled shafts with bells - Dp (a) (b) Figure 11.26 (a) Construction of drilled shafts with bells and grade beam; (b) definition of parameters in Eq. (11.14)

Fundamentals of Geotechnical Engineering (MindTap Course List)

5th Edition

ISBN:9781305635180

Author:Braja M. Das, Nagaratnam Sivakugan

Publisher:Braja M. Das, Nagaratnam Sivakugan

Chapter19: Drilled Shaft

Section: Chapter Questions

Problem 19.1P

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Load and resistance factor design

Load and resistance factors design (LRFD), also known as Limit state design (LSD), refers to the design method used in building engineering. A boundary condition is a condition of a structure where it can no longer meet the relevant design requirements. The condition may refer to the load level or other actions on the structure, while the terms refer to the integrity of the structure, suitability for use, durability, or other design requirements. A structure designed for LRFD is limited to keeping track of all possible actions during its design time and is always ready for use, with the appropriate level of reliability in each boundary condition. LRFD-based construction codes clearly define the appropriate levels of reliability in their instructions.

Question

Refer to Figure 11.26b. For the drilled shaft with bell, given:
Thickness of active zone, Z = 9 m
Dead load = 1500 kN Live load = 300 kN
Diameter of the shaft, D_s = 1 m
Zero swell pressure for the clay in the active zone = 600 kN/m²
Average angle of plinth-soil friction, Φ'_ps = 20°
Average undrained cohesion of the clay around the bell = 150 kN/m². Determine the diameter of the bell, D_b. A factor of safety of 3 against uplift is required with the assumption that dead load plus live load is equal to zero.

Dead load, D
Grade beam
Ground surface
U
Z
Active
zone, Z
Drilled shafts
with bells
- Dp
(a)
(b)
Figure 11.26 (a) Construction of drilled shafts with bells and grade beam; (b) definition of
parameters in Eq. (11.14)

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