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Rock Anchor

The document calculates the pile capacity of a foundation with the following properties: - The pile has a 1m diameter shaft with a 5m long socket into rock. - The rock has a core recovery of 92%, RQD of 31%, and crushing strength of 21MPa. - Using empirical relationships, the ultimate end bearing capacity is calculated to be 1395 tonnes. - The ultimate side socket shear is calculated to be 1620 tonnes. - The allowable capacities are 465 tonnes for end bearing and 539 tonnes for side shear.

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Vijay Kumar
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393 views2 pages

Rock Anchor

The document calculates the pile capacity of a foundation with the following properties: - The pile has a 1m diameter shaft with a 5m long socket into rock. - The rock has a core recovery of 92%, RQD of 31%, and crushing strength of 21MPa. - Using empirical relationships, the ultimate end bearing capacity is calculated to be 1395 tonnes. - The ultimate side socket shear is calculated to be 1620 tonnes. - The allowable capacities are 465 tonnes for end bearing and 539 tonnes for side shear.

Uploaded by

Vijay Kumar
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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1 Calculation of pile capacity

1.1 Properties of foundation rock (As per IRC:78-2014.cl.9)


Core Recovery in percent CR = 92.00 %
Rock quality designation RQD = 31.00 %
Crushing strength of the rock = 21.00 Mpa

Characterstic strength of the concrete fck = 35.00 Mpa

Diameter of the pile shaft = 1.00 m


Socketing length of the pile shaft into the rock = 5.00 m

1.2 Ultimate end bearing (Re) (CR+RQD)/2


Ksp
CR = 92.00 % 30 0.3
RQD = 31.00 % 100 1.2
(CR+RQD)/2 = 61.5
Emperical co-efficient Ksp = 0.705
Avg.unconfined compressive stength
qc = 21.00 Mpa

Socketing length of the pile into the rock = 5000 mm


Diameter of the socket = 1000 mm
Depth factor df = 1.2
2
Cross sectional area of the bease of pile Ab = 785398 mm
Ultimate end bearing Re = 1.4E+07 N
= 1395.34 t
1.3 Ultimate side socket shear(Raf)
2
Surface area of socket As = 1.6E+07 mm
Ultimate shear strength of the rock along socket length
Cus = 1.03 Mpa
Ultimate side socket shear(Raf) Raf = 1.6E+07 N
= 1619.62 t
1.4 Allowable capacity of the pile
Ultimate end bearing Re = 1395.34 t
FOS = 3
Allowable capacity in end bearing Re/3 = 465.113 t

Ultimate side socket shear(Raf) Raf = 1620 t


= 3
Raf/6 = 539.872 t

Allowable shaft resistance in compression = 1004.98 t


Allowable shaft resistance in uplift = 539.872 t

2 Method-2
End bearing component(Re)
Type of rock considered = VERY WEEK
Avg shear strength IN bearing Cu,b = 1 Mpa
Nc = 9
2
Ab = 785398 mm
Re = 4948008 N
Qallowable=Re/3 = 164.934 t
Friction component(Raf)
Avg shear strength along the socket as per N-value
= 1.0 Mpa
Cu,s = 1.0 Mpa
2
As = 1.6E+07 mm
Rf = 15708 kN
Qallowable=Raf/3 = 2617.99 kN

Allowable shaft resistance in compression


Qu=Re+Raf = 2782.93 kN
Allowable shaft resistance in uplift Raf = 2617.99 kN

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