Plate load test

PLATE LOAD TEST
PRESUMPTIVE SAFE BEARING CACACITY
PLATE LOAD TEST APPARATUS / EQUIPMENT
PLATE LOAD TEST PROCEDURE
CALCULATION OF BEARING CAPACITY FROM PLATE LOAD TEST�
For vedo link
Https://youtu.be/BUMd7CKcBV8

2. CONTENT
PLATE LOAD TEST
PRESUMPTIVE SAFE BEARING CACACITY
PLATE LOAD TEST APPARATUS / EQUIPMENT
PLATE LOAD TEST PROCEDURE
CALCULATION OF BEARING CAPACITY FROM PLATE LOAD TEST

3. PLATE LOAD TEST
Theplateloadtestisafieldtest,whichisperformedtodeterminethe
ultimatebearingcapacityofthesoil.
Theconductaplateloadtest,pitofsize5�
????????????5�
??????,where�
??????isthesizeof
plate,isexcavatedtoadepthequaltothedepthoffoundation(??????
??????).
Thesizeofplateusually0.3msquare.Itismadeofsteelandis24mm
thick.Occasionallycircularplatesarealsoused.
Sometimes,largeplatesof0.6msquareareused.

5. A central hole of the size �
????????????�
??????is excavated in the pit.
The depth of central hole (??????
??????)is obtained from the following relation:
where�
??????is the width of plate, and �
??????is the size of plate.

6. PLATE LOAD TEST APPARATUS / EQUIPMENT
The following plate load test apparatus is necessary for performing
the test.
1.Test plate
2.Hydraulic jack & pump
3.Reaction beam or reaction truss
4.Dial gauges
5.Pressure gauge
6.Loading columns
7.Necessary equipment for the loading platform.
8.Tripod, Plumb bob, spirit level, etc.

7. PLATE LOAD TEST PROCEDURE
1.Excavatetestpituptothedesireddepth.Thepit
sizeshouldbeatleast5timesthesizeofthetest
plate(B
p).
2.Atthecenterofthepit,asmallholeordepression
iscreated.Thesizeoftheholeisthesameasthe
sizeofthesteelplate.Thebottomlevelofthehole
shouldcorrespondtotheleveloftheactual
foundation.Thedepthoftheholeiscreatedsuch
thattheratioofthedepthtowidthoftheholeis
equaltotheratiooftheactualdepthtotheactual
widthofthefoundation.
3.Theplateisplacedinthecentralholeandthe
loadisappliedbymeansofahydraulicjack.
4.Thereactiontothejackisprovidedbymeansofa
reactionbeam.Sometimes,trussesareused
insteadofareactionbeamtotakeupthereaction.

8. PLATE LOAD TEST PROCEDURE
5.Theloadedplatformcanbeusedtoprovide
reaction.
6.Aseatingloadof7KN∕m
2
isfirstapplied,which
releasedaftersometime.
7.Theloadisthenappliedinincrementsofabout
20%oftheestimatedsafeload.
8.Thesettlementisrecordedafter1,5,10,20,40,
60minutesfurtherafteranintervalofonehour.
9.Thesehourlyobservationsarecontinuedfor
clayeysoilsuntiltherateofsettlementisless
than0.2mmperhour.
10.Thetestisconducteduntilfurtheroratleast
untilthesettlementofabout25mmhas
occurred.

9. CALCULATION OF BEARING CAPACITY
FROM PLATE LOAD TEST
Afterthecollectionoffielddata,theload-
settlementcurveisdrawn.Itisalogarithmic
graphwheretheloadappliedisplottedonX-axis
andsettlementonY-axis.Fromthegraph,the
ultimateloadfortheplateisobtainedwhichis
thecorrespondingloadforsettlementofone-fifth
oftheplatewidth.
Whenthepointsareplottedonthegraph,the
curveisbrokenatonepoint.Thecorresponding
loadtothatbreakpointisconsideredtobethe
ultimateloadontheplate.Theultimatebearing
capacitycanbecalculatedfromtheultimateload
fromtheplate.Theultimatebearingcapacityis
thendividedbyasuitablefactorofsafetyto
determinethesafebearingcapacityofsoilfrom
thefoundation.

10. 1.The ultimate bearing capacity of the proposed foundation q
u(f) can be
obtained from the following relations:
Where �
??????= foundation width.
2.The plate load test can also be used to determine the settlement for a
given intensity of loading ( q
o). The relations between the settlement of
the plate ( s
p) and that of the foundation ( s
f) for the same load intensity
are given below.
Where s
pis obtained from the load intensity settlement curve for q
o.
(a) For clayey soils, q
u(f) = q
u(p) ……(a)
(b) For sandy soils, q
u(f) = q
u(p)??????(ൗ
�
??????
�
??????
)……….(b)
(a) For clayey soils,s
f =s
p??????(ൗ
�??????
�
??????
)……….(a1)
(b) For sandy soils,s
f = s
p
�
??????(�
??????+0.3)
�
??????(�
??????+0.3)
2
…….(b1)

11. In above equation, �
??????is the width of foundation in meters and �
??????is the
width of plate in meters.
3.For designing a shallow foundation for an allowable settlement of s
f , a
trail and error procedure is adopted. First of all, a value of �
??????is assumed
and the value q
oof is obtained as
Where �
??????is the area of footing, Q is the load.
4.The plate load test can also be used for the determination of the influence
factor I.
q
o=ൗ
??????
�
??????
S =
(1−µ
2
)
????????????
????????????????????????�