pile design for sandy soil

"angle of repose" or "land mass density ratio" or "cohesion", maybe?

http://en.wikipedia.org/wiki/Cohesion_(geology)

Ok, ok... Take a two meters long sample of that material which will be used when creating the pile. Count how much is the maximum weight where the pile brakes, then minus 500 in kg if the pile is under a surface where big trucks or cars are running on thye road, and the pile is under that road.Or count Nm..

(You know only when you know the strainght of those materials which are used when the pile is in the making, because the quality is not always the same.)

DYNAMIC STATIC LOAD TEST

Dynamic Static Load Tests
For pile tests based on the dynamic load principle, the load applied to the pile
is dynamic (that is, moving).
There are many pile tests based on the dynamic load principle. Some of these
are:
the dynamic formula test,
the Case - Goble test, and
the steady state dynamic response test.

Dynamic Formula Test
In the dynamic formula test, the pile is driven into the ground using any of the
hammers. The set (that is , the penetration per blow of hammer) is measured. The
load - bearing capacity of the pile is then calculated by substituting the
measurement of the final set and the known energy of the hammer into a formula.
There are many pile driving formulae, a number of which are based on the
principle of the conservation of energy. The ideal complete dynamic pile driving
formula should be of the form:
Applied energy = Useful work + Loss in impact + Loss in pile cap + Loss in pile
+ Loss in soil
However, not all piling formulae take into account every cause of energy loss.
Some simple formulae neglect the weight of the pile, and therefore give
misleading values of the resistance when the applied driving energy is very
small. Other formulae do not take into account the energy absorbed by the pile.
Thus, on a heavy pile driven with a light hammer, the penetration per blow is
very small and the calculated value of the load - bearing resistance may be
false.
Some common dynamic pile driving formulae are listed below:
Ru = efWrh(Wr + e2Wp) / [s+1/2(C1+C2+C3)](Wr+Wp)

Hiley formula
Ru = -sAE / L + (2WrhAE / L + sAE2 / L)1/2

Weisbach formula
Ru = 2AEs(1+WrhL / s2EA)1/2 / L - 1

Rankine formula
where
Ru = ultimate bearing capacity of the pile
Wr = weight of ram of pile driver
Wp = weight of pile
s = set (penetration per blow of hammer)
h = height through which hammer falls
L = length of pile
C1 = elastic compression of pile cap
C2 = elastic compression of pile
C3 = elastic compression of soil
e = coefficient of restitution
ef = efficiency of hammer
E = Young's modulus of elasticity of the pile
A = cross - sectional area of pile
In general, one of these pile driving formulae is used to obtain the results.
The most commonly used formula is the Hiley formula.
The results of these theoretical tests are highly unreliable and should be used
only in conjunction with the results of the actual load - bearing tests.

Back to the Top

Case-Goble Test
The Case - Goble test is based on the principle of measuring the stress wave at
the top of the pile during pile driving. The stress is measured by the pile
driving analyser, and the ultimate pile bearing capacity is then automatically
computed.
The pile driving analyser has three important areas of practical application. It
can be used to determine:
the bearing capacity of the pile,
the pile integrity, and
the hammer performance.

Fig. pt11
Fig. pt12

The test is carried out by attaching the instrumentation from the analyser to
the head or body of the pile as shown in Fig. pt11. Two reusable strain gauges
and two accelerometers are securely bolted near the top or body of the pile. The
pile is then driven into the ground using any of the hammers described before.
The electrical signals from each hammer blow are fed into the programmed pile
driving analyser, and the measured strain and acceleration are converted into
force and velocity parameters as a function of time. The ultimate bearing
capacities Ru are automatically computed by substituting all the measured
parameters into a formula.
Ru = P - d
where
P = (F1 + F2) / 2 + (MC/L)(V1 - V2) / 2
F1 = force at impact (tonnes)
F2 = force at 2L/C sec. after impact (tonnes)
M = mass of pile in tonnes/9.81 m/sec2
C = velocity of longitudinal wave propagation,
= 5122 m/sec for steel
L = pile length below gauges (m)
V1 = velocity at impact (m/sec)
V2 = velocity at 2L/C sec. after impact (m/sec)

d = damping force = Jc(2 F1 - P - Fstat)
Jc = damping factor, depending on soil type and penetration resistance
Fstat = precompressing force of hammer
= 20 tonnes for diesel hammerIn addition, the analyser measures the impact and the maximum forces, the
developed energies and the hammer blow rates. The force and velocity wave traces
are continually observed on an oscilloscope and their analogue signals are
recorded on magnetic tape by an FM instrumentation tape recorder.

Back to the Top

Steady State Dynamic Response Test
Another method of testing piles, based on the dynamic load principle, is the
steady state dynamic response test.

Fig. pt13
Fig. pt14

Fig. pt13 shows a schematic diagram of this method. The test is carried out by
placing an electro - dynamic vibrator on the centre of the prepared head of the
pile as shown in Fig. pt14. The vibrator imposes a sinusoidal force of constant
amplitude to the pile. A velocity transducer records the movement of the head of
the pile caused by the induced vibration. An X-Y recorder plots the mechanical
admittance | V/F | against frequency, as shown in Fig. pt15. The integrity of
the pile is then measured from the geometry of the curve.

Fig. pt15

The pile length can be calculated by measuring the distance between the
resonating peaks f and then substituting into the following formula:
L = VC / 2f
where
L = length of pile (m)
VC = propagation velocity of longitudinal waves in material of pile (m/millisec)
f = distance between resonating peaks (m)
The concrete density, or, conversely, the cross-sectional area of the pile, can
be calculated by measuring the mean height N (see Fig. pt15) of the resonance
part of the curve.
N = 1/PCVCAC
where
N = mean height of the resonance part of the curve
PC = concrete density
VC = propagation velocity of longitudinal waves in concrete
= (4 m/millisec for concrete)
AC = cross - sectional area of pile (m2)
The dynamic pile head stiffness ED (tonnes/mm) is measured at low frequencies
when the pile/soil system is vibrating as a unit. By definition, the dynamic
flexibility is the slope of the initial part of the mechanical
admittance/frequency curve. Referring to Fig. pt15,
flexibility = | V/F |M + 2fM*pi (mm/T)
ThereforeED = 1 / (| V/F |M + 2fM*pi) (T/mm)
ED can be correlated with the elastic stiffness ES from the test.
ES = Load / Settlement (tonnes/mm)
andED/ES = F
The value of F has been found to vary between 1 and 2. On most sites in
Southeast Asia, approximate values of 1.5 and 1.25 have been found on smaller
and large diameter piles respectively.
Good pile soil interaction is indicated by the damping of the curve, that is,
there is little different between N, P and Q. Conversely, a strong resonating
curve with Q tending to zero indicates that very little skin friction is being
developed, or that the pile is broken.

This must be a joke!

Notwithstanding the encyclopedic response that doesn't respond to the question, why don't you at least supply meaningful and realistic data. Yours is so far out of kilter that it is absurd.

Ok I tell you what I would do next if I had that pile.

Found five workers in the nearest pub. Buy three bottles of fine quality whiskey.

Load the pile on a truck, and get a hammer, and some tools. Tell the workers to drink up the whiskey, and send them to work.

"Energy can be transformed from kinetic to potential to electric to chemical and so forth.
We need to nurture intelligence, not bellicosity."

(My robot said all these, not me)

The ultimate bearing capacity of pile is generally represented by the formula :-

Qu= Qb+Qs where Qb is ultimate bearing resistance available and

Qs is ultimate shaft resistance available

Because the problem of obtaining undisturbed samples , the design parameters for piles in granular soil are usually obtained from is situ penetration test. The values for the angle of internal friction thus obtained are suitable for most practical problems of piles in granular soils.

End resistance :

(i) Driven piles

Meyerhoff(1976) proposed that the ultimate end bearing resistance of a pile in granular soil can be obtained from the expression

Qb = fb * Ab

where fb is termed the unit penetration resistance of the soil and is calculated from the expression ; fb = p' * Nq

Nq is a bearing capacity factor ( you can find from any soil mechanic book) which varies with both the angle of friction of the soil and the penetration depth to width (D/B) ratio. Nq increases roughly linearly with increasing D/B ratio until it reaches a maximum and thereafter constant , value at Dc/2B . Dc is known as the critical depth. For depths of penetration > Dc , the bearing resistance of the pile tend towards a constant value known as f limit. The end resistance for a driven pile achieves a maximum value over a penetration depth of between 10B and 20B.

p' is effective overburden pressure at the pile tip

Lets work on load of 200 KN ;

Factor of safety = 3 , Angle of friction , Ø = 15

Assumed as you have not provided

a)(no water table identified) (b) unit weight ,γ= 16 KN/m3

(c)Pile size , B = 0.6 m diameter

For B =0.6 m ; From graph , the Dc /B = 2.2 , hence Dc = 2.2*0.4=0.88m

f limit = 1 MN/m2 ( from another graph)

Qb = flimit*Ab =1*1000*∏ * 0.6² / 4 = 282.8 KN

Qs = fs*As where fs = p'' Ks tan δ (up to 20B )

δ= 0.75 * Ø = 0.75*15 = 11.25 ( refer table for Ks and δ in granular soil- find out yourself)

Depth of penetration = 20 B = 20 *0.4 = 8 m

p'' at 8 m = γ * 8 = 16*8 = 128 KN/m2

Ks = 2(1-sin 15) = 1.48

Hence fs at 8 m = 128 *1.48*tan 11.25=37.7 KN/m2

Qs = 37.7 * (∏ * 0.6²/4) * 8 = 85 KN

Therefore Qu = Qb+Qs= 282.8+ 85 = 367.8 KN

FOS = 367.8/ 200 = 1.84 ( Normally the recommended FOS is from 2 to 3, so you have to upgrade the pile by increasing the diameter or depth )

Find somebody in your office who knows how to do it. Surely you are not the only engineer in the office? This will not only help you to do things in the same way as the rest of the office, it will help to create the team that an office should have. As a graduate you will also be able to help the old hands from time to time. Teamwork.

Find a copy of 'Soil Mechanics' by R.F. Craig, and go to the chapter on bearing capacity. This is a standard text for undergrad civil engineers.

Hello

Send me an email at fareed_siddique@yahoo.com .. i will send you some sample calculations for pile design in MathCad or in PDF ...