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Jun 4, 2020

Erratum for “Settlement Estimation of Piled Rafts for Initial Design” by Priyanka Bhartiya, Tanusree Chakraborty, and Dipanjan Basu

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Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 146, Issue 8
The following corrections should be made to the original paper:
1.
In the section “Unpiled Raft Stiffness,” there is a typographical error in Eq. (3). The correct form of Eq. (3) is
krs=1.73Cs×{log(LrTr)}0.5×(1μs21μr2)×{1(TrBr)3}×e(30(Es/Er))
2.
There are multiple typographical errors in the calculation steps in the section “Numerical Examples.” Therefore, the calculation steps of both the numerical examples with correct equations and numerical values are given as follows:

Example 1: Case Study of Rectangular PRF

1.
Given Es=40  MPa, μs=0.3, and Ar=83×46.5=3859.5  m2, Ks is calculated as
Ks=Es(1μs)(1+μs)(12μs)Ar={40,000×(10.3)}/{(1+0.3)(12×0.3)3,859.5}=866.74  kN/m3
Noting Cs=(Br/Lr)0.25=(46.5/83)0.25=0.865, krs is calculated as
krs=1.73Cs×{log(LrTr)}0.5×(1μs21μr2)×{1(TrBr)3}×e(30(Es/Er))=1.73×0.865×{log(83/1)}0.5×{(10.32)/(10.22)×{1(1/46.5)3}×e{30×(40)/30,000}=1.89
This gives the raft stiffness Kr=Kskrs=866.74×1.89=1638.14  kN/m3.
2.
Considering the pile group, Ap=π×1.52/4=1.767  m2; Agp=π×1.52/4×40=70.686  m2
Ips=0.0084×{e0.001(Ep/Es)·(Lp/Dp)0.034}×(μpμs)×(LpDp)=0.0084×{e0.001(30,000/40)·(27.5/1.5)0.034}×(0.20.3)×(27.51.5)=0.045
Therefore, Kp1=ApEpIps/Lp=1.767×30,000×1,000×0.045/27.5=86,743.64  kN/m. Now, η=10.4log(1Agp/ArDp/(2sr))=10.4×log{1(70.686/3,859.5)(1.5/18)}=1.019. This gives Kp=Kp1np(eη2)/Agp=86,743.64×40×(e1.0192)/70.686=37,817.55  kN/m3.
3.
Now rm=2.5+Lp{2.5(1μp)0.25}=2.5+27.5×{2.5×(10.2)0.25}=50.625 and rr=Ar/(πnp)=[3,859.5/(π×40)]=5.542, so
αpr=1ln(rr/rp)ln(rm/rp)=1ln(5.542/0.75)ln(50.625/0.75)=0.525and0.38e2.4(Agp/Ar)=0.38e2.4(70.686/3,859.5)=0.397
This gives
Kpr=0.38e(2.4(Agp/Ar))Kp+Kr(12αpr)1+αpr2Kr/Kp=0.397×37,817.55+1,638.14×(12×0.525)1+0.5252×1,638.14/37,817.55=14,755.49  kN/m3
4.
Based on the estimated Kpr, the average PRF settlement Spr,av=(P/Ar)/Kpr=181/14,755.49=0.0123  m=12.3  mm. Therefore, the expected maximum PRF settlement 1.2×12.3=14.75  mm. The maximum settlement reported in the literature (Yamashita et al. 2011) is 18 mm.

Example 2: Circular PRF

1.
Given Es=20  MPa, μs=0.3, and Ar=π×4.372=60  m2
Ks=Es(1μs)(1+μs)(12μs)Ar={20,000×(10.3)}/{(1+0.3)(12×0.3)60}=3,475.75  kN/m3
For a circular PRF, Cs=0.85; therefore
krs=1.73Cs×{log(LrTr)}0.5×(1μs21μr2)×{1(TrBr)3}×e(30(Es/Er))=1.73×0.85×{log(8.740.5)}0.5×(10.3210.22)×{1(0.58.74)3}×e(30(20/30,000))=1.52
This gives Kr=Kskrs=3,475.75×1.52=5,283.14  kN/m3.
2.
With Ap=π×0.52/4=0.196  m2 and Agp=π×0.52/4×9=1.764  m2
Ips=0.0084×{e0.001(Ep/Es)·(Lp/Dp)0.034}×(μpμs)×(LpDp)=0.0084×{e0.001(30,000/20)·(10/0.5)0.034}×(0.20.3)×(100.5)=0.021
Thus, Kp1=ApEpIps/Lp=0.196×30,000×1,000×0.021/10=12,348  kN/m. Now
η=10.4log(1AgpArDpsr)=10.4×log{1(1.764/60)(0.5/3)}=1.038
Thus, Kp=Kp1np(eη2)/Agp=12,348×9×(e1.0382)/1.764=51,884.55  kN/m3.
3.
Now rm=2.5+Lp{2.5(1μp)0.25}=2.5+10×{2.5×(10.2)0.25}=20, rr=Ar/(πnp)=[60/(π×9)]=1.457
αpr=1ln(rr/rp)ln(rm/rp)=1ln(1.457/0.25)ln(20/0.25)=0.60,and0.038e(2.4(Agp/Ar))=0.038×e(2.4×(1.764/60))=0.04078
This results in the PRF stiffness
Kpr=0.038e(2.4(Agp/Ar))Kp+Kr(1+2αpr)1+αpr2Kr/Kp=0.04078×51,884.55+5,283.14×(1+2×0.6)1+0.62×5,283.14/51,884.55=13,252.9  kN/m3
4.
The estimated average PRF settlement Spr,av(equation)=12×1,000/(13,252.9×60)=15  mm. The average elastic settlement Spr,av(FEM) obtained directly from FE analysis is 19.5 mm. The expected maximum PRF settlement 1.2×15=18  mm. The maximum PRF settlement Spr,max(FEM) obtained directly from FE analysis is 20.4 mm.
The authors regret these errors.

References

Yamashita, K., T. Yamada, and J. Hamada. 2011. “Investigation of settlement and load sharing on piled rafts by monitoring full scale structures.” Soils Found. 51 (3): 513–532.

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Journal of Geotechnical and Geoenvironmental Engineering
Volume 146Issue 8August 2020

History

Received: Mar 13, 2020
Accepted: Mar 16, 2020
Published online: Jun 4, 2020
Published in print: Aug 1, 2020
Discussion open until: Nov 4, 2020

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Priyanka Bhartiya [email protected]
Project Scientist, Dept. of Civil Engineering, Indian Institute of Technology, New Delhi 110016, India. Email: [email protected]
Tanusree Chakraborty [email protected]
Associate Professor, Dept. of Civil Engineering, Indian Institute of Technology, New Delhi 110016, India. Email: [email protected]
Dipanjan Basu, Ph.D., M.ASCE [email protected]
Associate Professor, Dept. of Civil and Environmental Engineering, Univ. of Waterloo, Waterloo, ON, Canada N2L 3G1 (corresponding author). Email: [email protected]

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