Geotechnical Engineering Circular No. 9 Design, Analysis, and Testing of Laterally Loaded Deep Foundations that Support Transportation Facilities


Figure A P-y curve in stiff clay with free water - static loading (after Reese et al. 1975)



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Soldier Rev B
Figure A P-y curve in stiff clay with free water - static loading (after Reese et al. 1975).
Figure A P-y curve in stiff clay with free water - cyclic loads (after Reese et al. 1975).


221
Figure A Normalized p-y curve for stiff clay with free water – static loads (after Dunnavant and
O’Neill 1989).
Figure A Normalized p-y curve for stiff clay with free water – cyclic loads (after Dunnavant and
O’Neill 1989).
The following steps can be followed to construct the p-y curve in stiff clays with free water at depth z. Static Loading For static loading, follow the steps indicated below to construct the p-y curve as shown in Figure A
1. Obtain the profiles of undrained shear strength (C
u
) and effective unit weight (γ′).
2. Select pile/shaft diameter D.


222 3. Compute the average undrained shear strength (C
a
) over the depth z.
4. Compute the ultimate resistance (p
u
) of soil per unit length of pile. Depending on the type of failure mechanisms that is formed (near ground surface or well below ground surface, two values can be calculated for the ultimate resistance, p
ct
and p
cd
, respectively. Use the smaller of these values, which are computed as
𝑝𝑝
𝑐𝑐𝑡𝑡
= 2𝐶𝐶
𝑚𝑚
𝐷𝐷 + 𝛾𝛾

𝐷𝐷𝑘𝑘 + 2.83𝐶𝐶
𝑚𝑚
𝑘𝑘 Equation A)
𝑝𝑝
𝑐𝑐𝑑𝑑
= 11𝐶𝐶
𝑢𝑢
𝐷𝐷 Equation A)
5. Construct the initial linear portion of the p-y curve as follows
𝑝𝑝 = (𝑘𝑘𝑘𝑘)𝑦𝑦 Equation A) where k is a proportionality coefficient with units of FL. This coefficient can be assigned to be k
s
(static loading) or k
c
(cyclic loading. Values for k
s
or k
c
can be selected from the recommended values presented in Table Ab Table A Representative values of k for stiff clays (Reese et al. 1975).


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