PONDASI PANCANG : part1b_Teori & Hitungan Daya Dukung Sondir - Hinawan T. Santoso, ST, MT

Okay, colleagues, we will continue

to the next discussion related

to pile foundations, namely related

to the calculation of the bearing capacity of

piles. Well, here we will convey the

theoretical concept and examples of

calculations. Well, in the previous meeting,

we have discussed in

full regarding pile foundations, both

from the contents, functions, and types of

pile foundations. Well, for

colleagues who have not followed

the video, you can click the link above or

in the description below. Okay, we will try to

explain in more detail regarding the

calculation of the bearing capacity of long piles.

Okay, let's

[Music]

continue so again, I

remind you that in the previous meeting

we have discussed so the equation for supporting

long piles also refers to the

type of pile based on

ee how to transfer the load into the soil.

Well, yesterday we discussed

the types of long piles, there are those

called npiring piles and also friction

files. Well, we will also use this

in

eh, the calculation of the bearing capacity of the piles, so

I repeat here what is meant by

nbiring piles, namely if the hard soil layer

consists of a rock

or hard soil. So later

the bearing capacity of this pile will depend ee

on the strength of the material of the pile.

That is, when the existing loads

are transferred into the hard rock

that It is considered strong enough to carry the load,

then this strength will be limited not

only by the strength of the underlying soil rock

but also by the strength of the

pile material itself. Well, if

the hard soil layer consists of a layer of sand,

then the support day of the pile will

depend greatly on the properties of the

sand layer, especially regarding the

density of this sand layer. Well,

yesterday we also mentioned this type of

sandy soil. When we later install a

pile in a group, yes,

in a group, it will be

compacted due to the influence of

the group. Well, this will have a

different effect from a pile that is

installed in clay, it is not

affected by this density due to the

pressure of the soil due to the group or

group of Ti piles. Well, to be able to

estimate the resistance force of the

hard soil layer against the tip of the pile, a

test can be carried out.

One of them is with a CPT or

sondir tool or you can also use an SPT

or standard penetration test. Well,

friends, you can also see this in

my previous explanation related

to

soil testing in the field for

foundation work. Later, you can see it

by clicking the link above or later I will

present it in the description.

Okay, let's

continue. Well,

we will discuss the

previous pile that must be attention is

we check or we control the

strength of the

pile material So what we have to check

So we can provide the

following formulation, namely the strength of

this pile material which is permitted we call it

P pile P pile is

the multiplication of the allowable stress of the

pile material that we use, we

multiply it by the cross-sectional area of ​​the

pile, so the strength of the pile material

will depend greatly on

these two parameters, so the allowable stress of the

pile material and also the cross-sectional area

Well for the materials commonly

used, namely steel and concrete,

I present the allowable stress that is

permitted to occur in steel, which is

around

0.35 to 0.5 multiplied by the fy

or the yield strength Like that Then

for the concrete permit, it is around 0.25 to

0.33

FC prime or the compressive strength of the concrete

at the age of 28 days Well as an explanation to make it

clearer, I have an example of a

brochure from Wika Beton, okay Well later,

colleagues, if the piles that

will be used are

manufactured or from a fabricator's product,

we can just refer to

this table But later, if friends, the

long piles are

our own production, this is mandatory to be

calculated by friends use the

existing formula, well this is presented

in this case Because this is from the fabricator,

namely from Wika, here there is a

triangular shaped pile, prestressed concrete, so it is prestressed, yes,

precast, prestressed, the

shape is triangular, here we

have concrete, the compressive strength

is fc42 or e, if in the form of a

cube, it is 500 kg / cm²

okay, well, if we buy it through a

fabricator, well, this is usually

presented in full by the fabricator

with a specification table of the

piles offered, well, this starts

from the size, then the area,

then the moment of

inertia, how much is the weight per meter,

then it goes into the class, well, this is

offered, there are two classes, class A and

class B, including the

test results for the bending moment

when it cracks, how much is the ultimate, it is

also presented Well, if in

the strength of the pile material, what means we are

punching it, what I gave

this red circle is the allowable

compression, well, this is what is

allowed for this pile to receive a compressive load

when later if we design it

in a

plate, one pile, ee, can be up to 40

tons, yes, the type size 280 and eh

even 55 to 57 tons for the 320

including the length of the

file if for example we want to order

well we can provide an explanation of

this allowable compression yes

we also use this formula later

friends try to calculate for example there is 500

kg / cm² Well we use If I'm not

mistaken in Wika this is used the

concrete permit is around

0.267 Well then multiply the area to

find what is meant by the strength

of the pile material in this case

Presented here is the allowable

compression yes friends how

to calculate it

Okay I continue besides checking the

strength of the pile material because this

is the nature of p is npiring then

we have to cross the strength of the

base soil or hard soil which

will be supported by the tip of the

pile well here we present here this is

with two field investigation data

namely The first is based on the

results of the sondir data or the cone value

and the second will be based on the

nspt data Well we try to review one

by one if we base it on the

sondir data well this is the formula that is commonly

used is like this so qp

pile qp The pole is the end bearing capacity of

the pole, which is the

cross-sectional area of ​​the end of the pole multiplied

by the average cone value of the

sounding Hosil divided by a safety factor.

This safety factor is usually taken.

If the end bearing capacity

is 3. Well, for the cone value

or P or commonly

called QC, it is used to determine the end

bearing capacity of the pole, which should be taken as the

average cone value. The

depth parameter is 6d to 10d, that is

for above the

pole, so above the bottom end of the pole and

2D to 4D is below the

bottom end of the pole where d is the diameter of

the pole or the width dimension of the pole. Well,

we can see this together.

This is a collapse pattern. Maybe we

have learned in the previous meeting

regarding the collapse of the foundation.

Well, this is a picture of the collapse of the

foundation due to the Q load at the end of the

pile foundation, so if

we draw it, it turns out that the influence of

this Q load will later be used to get

our bearing capacity. The influence is,

apart from the example of this end of the pole,

here is the end of the pole. Well,

apart from what was said earlier, 2 to EMP 4D

is below the end of the pole, this is the soil. still

influential well this is around 2 to 4D

and also later there will be an influence above from the

tip of this pile as much as previously stated

is 6 to 10d so later the average KC value

To determine the strength of the

soil at the tip of our pile with

the assumption of n plates we still have to

calculate the average QC value 2 to

4D below the tip of this pile yes 2

to 4 and then

later above the tip of the pile we also have to

still calculate that is 6

to 10 well this also we have to

calculate

Okay let's

continue Well for the nspt value well this

formula I took from myhof, namely

the magnitude of the bearing capacity of the tip of the pile

which is

4 times the cross-sectional area of ​​the pile multiplied

by the average nspt value around the

tip of the pile well this is what must be

considered from this formula what

friends, namely is the unit so

this formula is derived Indeed

empirically by myhof where for nspt eh

this we use the cross-sectional area

is in units of Fit quadr so later

if we calculate in grams per

cm² or later the unit is tons per me²

we have to ee convert it into Fit

later after it is finished we can find

where the bearing capacity is

as required well this MP value is

also

based on the average value

which should be taken at

almost the same depth as

for soundir so this is the tip of the

pile here the bottom part is

also still affected by

about 2 to 4D Well later at the

top end this is also still affected

by about 6 to 10d well this is usually

taken the average sometimes the top is 8d

for the bottom usually there are those who

use 2D or those who use 4D please

depend on the assumptions and beliefs

of each planner

Okay let's

continue Well for the second type of pile

which is where earlier n Biring like that

if this pile is designed based on

the adhesion between the pile and the

soil grains due to friction

then it is called fiction pile well

if we find a case like this

maybe we can skip the

first control which is a review of the

strength of the pile material this can be ignored

because we are of course sure that

with this friction all the forces

later eh from the pile material It is likely that it

will not support too much because it

will be transferred directly to the

ground in contrast to the previous nbiring

pile has an influence also because

later he will be pressed by the pole, well

this friction bearing capacity can also be calculated

based on the sondir data or later

with the

nsptah data, yes, if based on the

sondir data, it means we will refer

to the

number of adhesive resistances or can be

called clif Well, if we

do a sounding test Usually if the

system is biconus, later eh one

cone at the end will provide

end resistance while the

secondary cone whose attachment will be

depicted, well,

what is the formula? So what is QS?

is the friction bearing capacity of the pole,

which is actually the formula, the area of ​​the

pole multiplied by the value of C This C is

the clif or the number of adhesive resistances

divided by a safe number Well, the area of

this pole is the circumference of the pole

multiplied by its length, well,

friends, later it can be calculated with

this formula, well, the safe number here

for friction P is usually taken to be

greater than the n Biring P

earlier If n Biring was three in

this friction file, we use the f

is 5,

okay, let's continue Well, if based on the

friction bearing capacity based on this nspt value

by Mayerhof in 1956 also

given a general formula that is often

used, right, only here it is divided

into two, namely large displacement piles

and small displacement piles, well, in the

previous meeting we have divided

these piles based on the

ee volume of soil displaced, well, this is

divided into large displacement piles,

small displacement piles and also

ee without displacement, yes, for

large displacement piles, these are usually

piles that have a

solid or closed end, usually made

of concrete material, usually the end is

closed or it can also be steel material

but equipped with shoes or

closed ends, Well, we can

use the formula QS, that is, from the

friction support of the pile, it is equal to the

pile area multiplied by the average nspt value

along the pile under review, divided

by the number

50, well, while for small displacement piles, well,

this small displacement pile

means that when it is driven, it only

moves the volume of soil in a

small ee displacement, yes, this is

usually a hollow steel pile

or a habim profile habim

or a concrete pile but it is

not closed at the end, meaning the end is

open, Well, this formula can be used,

namely QS pile

is the area of ​​eh The pile cover

multiplied by the average nspt value divided

by the number 100, well, this must be

Also note the same yes friends,

namely the area of ​​this blanket, the

unit is in Fed square and

the nspt value used is the

average nspt value

along the pole being reviewed, usually

later divided per segment or

layer based on the value

of the soil adhesion, later we will see

in the

calculation example, the third or

last one is if

our assumption is that this long pole

gets two Day supports, namely nbing

and friction file, so eh by looking at

this illustration, besides getting

hard soil, for example here, sandy soil,

yes, he gets the resistance force of the

end bearing capacity, he also

gets the adhesion or friction force

from, for example here, tah lembung If

the case is like this, then we also

need to do the

following calculation So,

we combine What should we

do because there is end resistance

or end virgin, then we have to

know from the strength of the pole,

the formula is the same as the one in front

where P pole is the

allowable stress of the pole material multiplied by the

cross-sectional area of ​​the pole, well,

we also have to pay attention to this after that

if we review it with

the strength of the second pole material, which

is the strength of the soil, well,

coincidentally here, if we get

or we use sondir data then

the formula that we can use is

as follows well this is divided there is a

temporary load if this temporary load

will be different from

other loads for example fixed or static

or Dynamic is the safe number Well

for this temporary load later the

EE Day supports The tip is

divided by two and the envelope is divided by 5

if this permanent load is usually in the

end bearing capacity divided by 3 the envelope

or friction is divided by 5 later

this dynamic load is much larger for example

earthquake yes the end bearing capacity is divided by 5

while in the friction or bond bearing capacity is

divided by 8 Well for

information here friends the value

because it has been divided by the safe number

then what is obtained in front of this is the

allowable or permitted Day bearing value

of the pile so if we can ee

formulate it more briefly so Q

allowable this pile is a combination of the

end bearing capacity of the pile

plus the blanket bearing capacity of the

pile that has been divided by the

SF number earlier

okay that's if sondir data Well

next if this nspt data is also the

same case divided into two

criteria where earlier there were

large displacement piles and small displacement piles

that differentiated earlier Yes,

the formula for the large displacement pile is

divided by 50

for the Day to support the friction for the

end bearing capacity, the formula is

the same as 4 times the pile area multiplied

by the average value of the SPT at the end of

the pile, well, this small displacement is what

differentiates it, this is divided by the

element for the attachment, it is divided by 100,

well, what differentiates it from the previous sondir data is

because here it has not been divided

by a safe number, so what we

get in front of this is the Q Ultimate

of the pile, so later if we

want to know the Day to support the permit

or allowable of the pile, we

have to divide it by a safe number

or safety factor, well, this is usually

used, the safe number for

calculating the foundation is 2 12

to four, well, later this depends

on the condition of the land data at the location in

question, then later, eh, the judgement

of the planner or engineer who

does the planning,

okay, let's

continue, well, this is to clarify the

theoretical explanation that I conveyed.

Previously, we will try to

describe or illustrate

an example of calculating the bearing capacity with a

case study of the question below, well, it is

known that the sondir and Boring data are

as presented in the picture on the side,

so in the picture on the side

friends are the sondir and boring results data

only the boring data we

do not have the nspt data is not

equipped with nspt so later what

we will use is the sounder data

we will use to calculate the bearing

capacity of the pile foundation

okay We can pay attention friends

for those who have not or have

done the results of the e test Sir the results are

like this yes So there are two lines

where this thick line is not

broken yes This is the sondir test result

for the cone tip pressure Well

we can see or read it

with the parameters above, namely the

cone pressure in units of kg / cm² well

while these dots

are the number of adhesive resistance Ji

cumulative yes from a depth of ol0 to

the depth being reviewed this is

the number of adhesive resistance and we can

read the parameters by looking at the

numbers below well this unit is

also kg /

cm² well it is

planned to use a

square pile foundation made of

concrete prikes known the allowable stress of the

concrete earlier yes friends, namely 60

kg /

cm² at a depth of 22 m and the size of the

pile cross section is 40 * 40 cm

so This pile, friends, we

plot it in a graph, yes, this is

approximately if the depth of 22 m is

up to this position so that later we

will make it easier to read the

average cone value at the tip of the pile or later

ee the adhesive resistance.

What are the instructions like? Calculate the load

that is allowed to work on the

single long pile,

how do you do it, friends? Well, at a

glance, let's

look at this pile, if we

plot it in the results of the sounding, it

turns out that at the tip it has touched

the number in the cone resistance at the tip, the

value is around

50 to 60 55, but by

deepening it again, it is around

130, well, this indicates that the tip

is approaching hard soil, usually

what is called hard soil if the

ser value is more than 150 and the

indication is that it will enter

hard soil. However, because maybe the limitations of the

data tool only reach a depth of

23 m. Well, here we also have

adhesive resistance, it turns out this also

works, so later we will calculate

here using the assumption that

this pile is designed for nbing and

friction files, let's see,

friends. Well, the assumption is that I

said the pile earlier This pile will

experience nbing and friction file

so we need to check this first

because later nbing influence we have to

check the strength of the pile material

so friends we calculated earlier we

already have the allowable stress of the material we

multiply the area of ​​the pile so

we get the value here is 96

tons for the strength of the pile material

then next we check the

strength of the soil well

there are two soil strengths namely the resistance of the tip n plate and

friction or adhesion Well we calculate

first for the resistance of the tip well this is the method is that

earlier the average cone value was required

from the depth of the pile at 22

m which could be 6 to 10 yes and

below is around 2 to 4 well

here we just take the maximum 10d

upwards from the tip of the pile and 4D downwards

From the tip of the pile n we go back to

the problem well this is around if earlier 40 cm

multiply 10 yes we are around 4 M will

review ee for us to take the average from

the soundir and if earlier m 4D downwards

it is around 1.6 M well or we take

around 2 m here well this value

We can see the average of each of these soundings in this graph,

perhaps it is not very detailed, we only have 1

M a well, we read at 18 how much 19 how much

20 how much k 21 22 ber what and

then later also at 23 and 24 well, this is

likely because at 24 there is no more

data Well, we just equate it with

the depth at 23 m so this is

the number or the average we

add up we divide by the depth

so that later we will get the

average of the resistance value of the tip of

the sondir well, we add up earlier

we read around 37 37 40 there is a value of

8 10 125 125 Well, we divide the depth

earlier by about 7 m well, we get

the value of 54.5 well, this is the value of the

resistance of the tip or qc or p well,

we put this into the formula earlier

Q the tip of the pile is the area of ​​the

cross-section of the tip of the pile multiply the value of P

or cone earlier divided by the safe number

we take three here well, we

enter the number we get it turns out the

magnitude of the resistance of the tip of the pile Day

support from n Biring yes that's 29 tons

Okay, let's continue Well, we also need to

calculate because the second assumption of nbing and

friction is the result of

friction

itself how to do it that is we have to

calculate the average klif value or the

average value of the amount of adhesive resistance

along the pole well the length of

this pole we divide into five parts

well this division we usually

base on the soundir property that we

get so if friends can

Pay attention yes here we have

soundir data for the amount of adhesive resistance like that

Well this value we usually

divide it based on the slope because

this slope determines the type of

soil that usually has an effect well in

this case for example this for the

first adhesive resistance we have

this value the slope later the second

is this this later we

have this slope

again then we have this slope again we have this

slope again the last so

we divide this into five parts well here

we see

our friends have divided earlier

based on the value here we

have five layers 0 to 3 m here we

calculate the c value That means we

read around the value 135 we subtract the

initial right Zero earlier yes we

divide it by the depth of 3 m we

get the value

0.45 kg/cm² and so on until the

last depth we have 20

to 22 now the average value

is 0.4

kg/cm² now these values

we will use to calculate the

bearing capacity due to friction Now we enter it

in the formula yes QS earlier is the

blanket area or perimeter multiplied by the length

multiplied by the average clif value

or average adhesion divided by a

safety factor number now in this case

we take 5 Now we enter

the perimeter, this is 40 * 4 earlier

because the square is

160 now this is the length per each

layer section we multiply by the

clif value now we

all enter the existing values

we divide the sf by 5 we get

17.18 tons so if we want to

calculate the bearing capacity of the pole,

this is actually not the Ultimate

Dar support allowabel because

we have divided SF which is 29 + 17.18

which is 46.18 tons Now in the question asked

for the permissible net load now

we need to reduce it by the weight

of the pole itself, which is

0.4 0.4 times the length 22 times the specific

gravity of this reinforced concrete is around

2,400 so that is equal to

8.45 tons So later if asked for the

load that is allowed to

work is n equal to the previous weight yes This is the allele bearing capacity minus the weight of the pole so that we get 37.73 tons now we cross check the strength of the pole material so we get 96 tons so that we get this value is Okay because it is still below it Well later friends who are allowed to work

is

37.73 tons Well if for example friends

Later in designing for example

a bridge pillar like that, it turns out that

the load on the bridge pillar is

for example there are 120 tons so that means

we just divide this 120

by the value of 37 Well approximately yes we

get the number is yes around 4

or 3.5 Well we round it

up to 4 meaning later the piles

needed are four pieces

for one pillar well Well

maybe that's the calculation well

later we will detail the calculation

more also related to the efficiency of the

piles if they work in

a group, well in this case, this is

just a Day pile supporting a single pile.

Well, what will the group piles be like?

We will learn in the next meeting.

Well, maybe that's enough of

our discussion related to Day

pile support, both theory and

calculation. Well, we will continue

again in the next meeting

by discussing

pile groups and also later related to the

implementation and supervision methods of

this pile foundation work. Okay,

friends, thank you for

your attention. Don't forget to continue

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see you on the next video, bye.