New Concept in Determining the Horizontal Load Capacity from Static Horizontal Loading Test in the Field

Metode Kurva Fit untuk menghitung Kapasitas Dukung Tiang Pancang Vertikal & Miring Akibat Beban Horizontal di Tanah Pasir dan Lempung dari Hasil Uji Beban Statik Horizontal di Lapangan untuk Tiang Pancang Kaku dan Fleksibel (Fitting Method to Determine the Ultimate Bearing Capacity of Vertical and Batter Pile under Horizontal Loads in Sand and Clay from Horizontal Static Loading Test for Rigid and Flexible Pile)

(New Concept by Dr.Fabian J. Manoppo (SamRatulangi University Manado) & Emeritus Prof. T. Koumoto (Saga Unversity Japan)

Kelebihan :

Metode Kurva Fit (Metode Grafis) dibandingkan dengan method grafis lainnya seperti, Chin, Davidson, Mazur Kiwics, P-Y Curve dimana Metode ini mengusulkan pada nilai Kapasitas Dukung Maksimum dari Tiang Pancang bukan pada Nilai Kerusakan dari pada pile (Pile Damage).

Mendapat Winning Price Paper Terbaik dari Jurnal International Jepang JSIDRE (Japan Society Irrigation Dranaige and Reclamation Engineering)

Dapat digunakan untuk variasi kemiringan tiang pancang (batter pile) dan variasi kekakuan tiang pancang rigid/kaku/pendek dan flexible/fleksibel/panjang


Analisa :

Dari hasil uji beban Horizontal statis pada tiang pancang vertical & miring dilapangan akan diperoleh kurva hubungan beban Q – defleksi Y.
Metode Kurva Fit digunakan dengan asumsi awal sebagai sebuah asymptot seperti pada Gambar 2,



Gbr 2. Asumsi metode kurva fitting hubungan beban Q – defleksi Y

Secara matematika dapat di tulis seperti :

Q = Y / (a + b x S)
Y/Q = a + b x Y

dimana, a dan b adalah parameter dari kurva Q ~ Y.
Persamaan 2 dibahagi dengan Y,

1/Q = a/Y + b

Pada saat defleksi Y tak berhingga persamaan 3 akan menjadi seperti :

Q = QY.tak berhingga = 1/b

dimana QY.tak berhingga adalah asumsi daya dukung maksimum saat defleksi Y = tak berhingga.
Nilai Kapasitas Dukung Maksimum (Ultimate Bearing Capacity) Qu dari tiang pancang tunggal vertical dan miring akibat beban horizontal dari hasil uji beban horizontal statis dilapangan (Static horizontal Loading Test) dapat dihitung sbb :

Qu = m * Qut

Nilai m, diperoleh dari perhitungan percobaan di laboratorium dan teori Meyerhof untuk berbagai macam variasi kekakuan Kr (Relative Stiffness Kr of Pile) terdiri dari tiang pancang kaku/rigid pile/tiang pancang pendek dan tiang pancang fleksibel/ flexible pile/tiang pancang panjang. Menggunakan rumus Poulos dan Davis sbb :

Kr = EP.IP / ES. L4 ; Jika Kr ≥ 0.01 (Rigid Pile) ; Kr ≤ 0.01 (Flexible Pile)

Qut untuk tiang pancang vertical dan miring dapat menggunakan rumus Meyerhof & Ranjan,

Untuk pasir,

{( Qut cos E(epsilon) ) / Qa }^2 + {( Qut sin E ) / Qn }^2 = 1

Qa = G(gamma) L Nq At + Ks G L tan d(delta) As/2

Qn = 0.125 G B L^2 Kb

Leu /L= 1.65 Kr^0.12 ≦ 1 (Tiang Pancang Fleksibel gunakan Leu)

Untuk lempung,

{( Qut cos E ) / Qa }^2 + {( Qut sin E ) / Qn }^2 = 1

Qa = 9 Cu Ap + α Cu. As

Qh = 0.4 Cu D d Kc


Perbedaan Tiang Pancang Miring dan Vertikal sbb :



Untuk masing2 jenis tanah dan variasi kemiringan tiang nilai m adalah sbb ;

Sand case (Untuk Tanah Pasir),

mβ=0^o = 0.364 + 0.037 Log (Kr)
mβ=15^o = 0.489 + 0.042 Log (Kr)
mβ=-15^o = 0.306 + 0.028 Log (Kr)
mβ=30^o = 0.585 + 0.035 Log (Kr)
mβ=-30^o = 0.456 + 0.050 Log (Kr)

Clay case (Untuk Tanah Lempung) ,

mβ=0^o = 1.138 + 0.278 Log (Kr)
mβ=15^o = 0.946 + 0.229 Log (Kr)
mβ=-15^o= 1.153 + 0.283 Log (Kr)
mβ=30^o = 0.740 + 0.149 Log (Kr)
mβ=-30^o= 0.861 + 0.094 Log (Kr)

New Concept by Dr.Fabian J. Manoppo (Fitting Method to Determine the Ultimate Bearing Capacity of Vertical Pile Loading Test in the Field)

To : Whom it may concern,

Metode Kurva Fit untuk menghitung Kapasitas Dukung Tiang Pancang Vertikal Akibat Beban Vertikal dari Hasil Uji Beban Statis di Lapangan (Fitting Method to Determine the Ultimate Bearing Capacity of Vertical Pile under Vertical Loads from Static Vertical Loading Test in the Field)

Kelebihan :
Metode Kurva Fit (Metode Grafis) dibandingkan dengan method grafis lainnya seperti, Chin, Davidson, Mazur Kiwics, P-Y Curve dimana Metode ini mengusulkan pada nilai Kapasitas Dukung Maksimum dari Tiang Pancang bukan pada Nilai Kerusakan dari pada pile (Pile Damage)

Analisa Metode Kurva Fit sbb :
Dari hasil uji beban vertikal statis pada tiang pancang vertikal dilapangan akan diperoleh kurva hubungan beban Q – penurunan S.
Metode Kurva Fit digunakan dengan asumsi awal sebagai sebuah asymptot seperti pada Gambar 2,


Gbr 2. Asumsi metode kurva fitting hubungan beban Q – penurunan S

Secara matematika dapat di tulis seperti :

Q = S / (a + b x S)
S/Q = a + b x S

dimana, a dan b adalah parameter dari kurva Q ~S.
Persamaan 2 dibahagi dengan S,

1/Q = a/S + b

Pada saat penurunan S tak berhingga persamaan 3 akan menjadi seperti :

Q = QS.tak berhingga = 1/ b

dimana QS.tak berhingga adalah asumsi daya dukung maksimum saat penurunan S = tak berhingga. Nilai Kapasitas Dukung Maksimum (Ultimate Bearing Capacity) Qu dari tiang pancang tunggal vertikal akibat beban vertical dari hasil uji beban vertikal statis dilapangan (Static Vertical Loading Test) dapat dihitung sbb :

Qu = m * Q

Dimana Qut dapat menggunakan teori dari Meyerhof menggunakan data laboratorium ataupun data SPT sbb :

Qut = 0.5* γ *D*Ks*Tan δ+ Ap* q’ *Nq (pasir)
Qut = 9*Cu*Ap + α*Cu*As (lempung)
Qut SPT = (4 * Np * Ap) + (Ns rata-rata * As /50)


Nilai m, diperoleh dengan melakukan pengujian dilapangan , perhitungan dan membandingkan seperti PDA Test, O’Cell Test, data SPT, Teori Meyerhof, Teori Chin, Teori Mazur Kiewich, Teori P-Y Curve dan Davidson diperoleh nilai sbb :

Untuk lapisan tanah keras (Hard / Stiff Soil) Nilai m = 0.5 – 0.97
Untuk lapisan tanah lembek (Soft / weak Soil) Nilai m = 0.2 – 0.4

Teori Baru Dr.F.J. Manoppo, Cara menghitung Bending Momen Tiang Pancang

Re: [forum-geoteknik-indonesia] Cara mencari kapasitas momen tiang
From: Fabian J Manoppo
View Contact
To: forum-geoteknik-indonesia@yahoogroups.com
Cc: alumnifatek@yahoogroups.com

Sedikit menjawab pertanyaannya mungkin bermanfaat :

Ada beberapa metode baik numerik bisa dengan bantuan software pile dll, juga bisa dianalisa dengan cara statik menggunakan rumus Brom's, Meyerhof, Manoppo et.al, dll untuk buku bisa Poulos & Davis dll

Kalau mau menggunakan Metode saya Manoppo et.al. (Manoppo, Koumoto and Sastry), dari hasil penelitian yg telah dan sedang dilakukan di laboratorium rumusnya adalah sebagai berikut :

1.Menghitung Bending Momen (Statik)
a. Untuk jenis tanah Pasir
Mmax. = 0.32. Quh . L (Rigid Pile/Tiang Kaku)
Mmax = 0.32. Quh . Leu (Flexible Pile/Tiang Fleksibel)

Rigid atau flexible dapat dibedakan pada Relatives Stiffness of Pile (kekakuan tiang) by Poulos & Davis sbb:
Kr = Ep.Ip / Es.L^4 untuk Rigid Pile Kr >= 0.01 dan Flexible Pile Kr <= 0.01

Leu = Length Efefctive Ultimate of Flexible pile by Sastry and Meyerhof (1994)
Leu / L = 1.65 Kr^0.12 <= 1

Quh = Ultimate Horizontal Load
L = Length of Pile

b. Untuk jenis tanah lempung
Mmax = 0.17. Qu. L (Rigid Pile)
Mmax = 0.17. Qu. Leu (Flexible Pile)
Leu / L = 1.5 Kr^0.12 <= 1

Untuk mengukur jarak maksimum bending moment (Lm) bisa menggunakan Metode,(Koumoto, Sastry and Manoppo) sbb :
Utk Pasir dan Clay :

Lm/L = 1.414 Kr^(1/4) tan^-1 [1/{1+1.414(e/l)Lr^(-1/4)}]

Teori yg sedang saya dkk kembangkan ini masih terbatas pada pembuktian percobaan loading test dilaboratorium dengan menggunakan beberapa variasi kekakuan tiang yg dipasang wire strain gauge dan dibaca dengan LVDT (Linear Voltage Differential Transducer)

Selamat mencoba dan membandingkan, kalau dapat hasilnya apalagi hasil dari pengukuran langsung di lapangan mohon informasi balik untuk saling menambah referensi

Hormat saya,
Fabian J Manoppo
Laboratory of Soil Mechanics and Geotechnical Enginering
Civil Department Faculty of Engineering
Sam Ratulangi University
Manado-Indonesia
http://fabianmanoppo.blogspot.com/
http://www.facebook.com/fmanoppo
http://www.kompasiana.com/fabianjm

From: Indra
To: forum-geoteknik-indonesia@yahoogroups.com
Sent: Tue, December 14, 2010 2:15:40 PM
Subject: [forum-geoteknik-indonesia] Cara mencari kapasitas momen tiang

Saya sedang mencari buku tentang cara mencari kapasitas momen tiang terutama tiang pancang beton maupun tiang bor. Kapasitas momen tiang ini dipakai untuk mencari kapasitas lateral suatu tiang khusus tiang jenis long pile dengan metode Broom. Apa cara mencari kapasitas momen tiang tersebut sama seperti halnya mencari kapasitas momen beton biasa khususnya bagian kolom ? Mohon bantuan para praktisi ataupun dosen di bidang geoteknik.

Terima kasih
Indra

pelelo (Geotechnical)
6 Dec 10 16:32
Hello,
I am analysing an excavation using SLOPE-W.
About 1 m off the top of the 10 m excavation there is a 4 story building.
According to the results i get from Slope W, I need to use any kind of earth retaining system (FS<1) on the excavation in order to make is stable (e.g anchors, nails, etc).
My question is, how could i obtain the design anchor force from SLOPE W? Is there any way to do so? Or will I need to enter several anchor force values until I get the Factor of safety i am looking for?
Please let me know.

althi (Geotechnical)
6 Dec 10 17:26
There must be a way in Slope/W. I use Slide and it has an option 'show support forces' to get this data.
On another note, if you use grout anchors in the upper strata, there is a potential that the adjacent building could move up by inches.

PEinc (Geotechnical)
6 Dec 10 18:44
Be careful using a flexible sheeting system to support a 4 story building. I would not do that. It would probably be more appropriate to use conventional concrete underpinning piers, a secant pile wall, jet grouting, or a slurry wall (in increasing order of cost). Soil nailing is not appropriate for supporting a building, big or small. Soil nail walls require significant open cuts along and below the existing building in order to install the nails and shotcrete. A building can fall down before you drill the first nail or spray the first load of shotcrete. A soil nail wall needs movement to transfer load to the passive nail tendons. Movement means settlement of the building. Building settlement can mean injury, damage, and a lawsuit. A combination of tiedback or braced sheeting with micropiles to support the existing foundations may also be economical.



pelelo (Geotechnical)
7 Dec 10 20:12
Thanks for you reply.

We are planning to deal with anchors as due to the site restrictions a small anchor drilling machine will be more accesible than any slurry wall drill rig, or secant piles drill rig.

I don't see very clearly the required anchor force from SLOPE W. I see the free body diagram force from each slice, but no information is given regarding any additional force required to stabilize the slope. Or maybe slope W doesn't show any information at all.
What I think is there should be an easier way instead of assigning an anchor forces and trying to chase the FS you are looking for. Mayeb it would be easier if I try another software, any ideas?
The adjacent building is 1 m off the slope, consolidation is not necessary as the soil profile is silty sand (SM), with n values between 10 and 20.



PEinc (Geotechnical)
7 Dec 10 23:28
For the few slope stability programs I have seen, you enter in a tieback force, by trial and error, and then see if the safety factor is OK. The programs do not calculate the required tieback force. For a program that calculates the tieback force, you need a wall design program such as CivilTech Software's Shoring Suite. However, the wall programs will not do a global slope stability analysis, as far as I have seen.

Bearing Capacity in Granural Soil

http://www.eng-tips.com/viewthread.cfm?qid=286567&page=1

New PostSMetcalfe (Geotechnical)
25 Nov 10 3:39
Hello, I am having a bit of trouble with a basic bearing capacity calculation;
Looking at a 14m dia. foundation founded at 1mbgl on loose granular deposits (N-value of 6, phi of 29degrees).
Based on the Brinch Hansen calculation, ignoring shape and depth factors and using a factor of safety of 3 I am obtaining a bearing capacity of around 1000kN/m2. This seems very excessive and when I compare this to other literature sources such as Tomlinson (7th edition) Fig 2.4, Pg 57, I should be looking at a value of around 50-150kN/m2.
Parameters I am using are a unit weight of 19kN/m3, bearing capacity factors; Nq - 16 and Ny - 18.

Can anyone correct me on where I am going wrong?
My shortened calc (Brinch Hansen) ignoring shape / depth factors is;

qn = (Po x Nq + 0.5 x yB x Ny) / 3
qn = ( ((19 x 1) x 18) x + 0.5 x ((19 x 12) x 18)) / 3
qn - bearing capacity
Po - Overburden pressure (Depth x unit weight)
Nq - factor (16)
Ny - factor (18)
yB - (Unit weight of soil x Breadth of structure)

New PostBigH (Geotechnical)
25 Nov 10 7:23
You are basically correct - you have a very large footing which gives a huge "gamma" term. Just think what it would show if the footing was a more normal width - say 5 m. Day's Fdn Engr HB (published by McGraw Hill and sponsored by ASCE shows a Ngamma value of about 15. This would push your value down a bit - so, in any event, you are showing an allowable bearing capacity of about 800 kPa (fudging a bit without calculating for the lower Ngamma (how did you get the greek symbols?). Anyway, as far as you go, you are correct.

However, this shows the point that shear seldom governs the permissible (allowable) bearing pressure. Settlement does. If one uses 25 mm of settlement for your size footing you would estimate an allowable bearing pressure of about 50 kPa (Terzaghi and Peck) - or perhaps as much as 75 kPa if one uses Bowles suggestion of adding 50%. For 50 mm of settlement (typical for mat foundation) one would say that the allowable bearing pressure (settlement based) would be in the order of 100 to 150 kPa - a far cry from the bearing pressure based on shear. One can draw curves of various allowable settlements vs footing width. See the attached chart. This is for a situation where the "N" value (corresponding Ngamma) is in the order of: 0 to 6m: 25 (35); 6 to 18m: 42 (95); 18 to 23m: 18 (23) and >23m: 49 (135). But it shows how to do it.

It has been my opinion that far too much effort is made on bearing capacity - and you see this even in the LRFD approach - you spend a lot of time analyzing the bearing capacity under many load variations - and in the end, it is the serviceability that will govern the permissible (allowable) bearing pressure.

For the chart that has been attached and its background, you can go to the following link and click on NCS Policy Memo 1 (they will then ask name etc so you can access their site (free).
http://www.ncsconsultants.com/projects/lrfd_policy_memoranda.php

One should also read Fellenius' papers
http://ww.fellenius.net/papers/219%20Delusion%20of%20Bearing%20Capacity.pdf
http://widener.parameterid.com/docs/courses/senior/F08_SP09/401files/FootingsinSand.pdf

* http://files.engineering.com/getfile.aspx?folder=f222ac63-e8ec-414a-bb03-51

New PostSMetcalfe (Geotechnical)
25 Nov 10 8:05
Thanks BigH that is really helpful. I used the tables within Tomlinson to obtain the greek values.

So which method would you recommend?

I don't really understand your second paragraph regarding settlement governing bearing capacity can you give me some more information on this or point me to a paper?

New PostRon (Structural)
25 Nov 10 9:56
Check your overburden pressure and unit weight...doesn't seem to fit with N=6 and soil description.


New PostBigH (Geotechnical)
25 Nov 10 16:30
I agree Ron that for N=6, a unit weight of 19 might be a bit high - but even if you drop it to 17 or even 16, it is not going to change the "answer" too much - for the big point is the very large (14m) foundation size. It is still the settlement that will govern the load than will be permitted on the foundation; it shows that large mats can carry, in shear, very large loads . . .

@SMetcalf - read the Fellenius paper. Why does settlement govern? Because if you exceed certain settlements (both total and differential) the structure you have might undergo distress (cracking, tilting, etc) that would make the structure unserviceable. Just think - if you have a limit on settlement of 40 mm and it takes only 75 kPa to achieve that - why would an an allowable bearing capacity of 300 kPa be relevant.

Soldier Pile Wall

mjalexan (Civil/Environme)
http://www.eng-tips.com/viewthread.cfm?qid=281487&page=1
16 Sep 10 10:07

Permanent Soldier Pile Wall
Wall height (H) = 12 feet
Using 14x73 H piles with precast concrete lagging
Deflection is limited to H/100 => 1.44 inches
Soil:
Sand = 120 pcf, phi=28 from top of wall to 21 feet
Sand = 120 pcf, phi=32 from 21 feet to 40 feet
I have a traffic surcharge of an additional 2 feet of fill behind the wall and level back fill.
I have a 14x73 H pile in the center of a 30 inch predrilled hole which will be filled with 3,000 psi concrete. I saw a thread about this but my question was not answered.
I want to determine the composite stiffness to use below the dredge line to keep my deflection down. Everything I have found online is the reinforced concrete design example with a row of rebar in the tension side of a beam, no circular shafts or columns.
Using just concrete or just the h pile seems too conservative, especially with the very limited deflection.

PEinc (Geotechnical)
16 Sep 10 12:27
FYI, I assumed that you could use Coulomb earth pressure coefficients and wall friction for both active and passive coefficients. I assumed 10' maximum soldier pile spacing. I ignored the strength of the concrete in the analysis. I assumed a passive resistance width of 3b = 3 x 2.5' = 7.5'. I added a Boussinesq area surcharge of 240 psf (= 2' x 120 pcf) starting 1 foot off the wall and extending 25 feet back. Using an HP14x73, GR50. I get an deflection of 0.99 inches. In my opinion, your 1.44 inch maximum allowable deflection (H/100) is not very limiting. I would design a permanent wall for less deflection than that. I would probaby design for no more than an inch unless specs required less.

Also, if you are using precast lagging, I hope you are building a fill wall where you can stack the lagging from the bottom up. It is hard to install concrete lagging in lifts as the excavation is being made. If you are building a fill wall with drilled soldier beams and concrete lagging, you probably are building an uneconomical wall.

dcarr82775 (Structural)
16 Sep 10 13:42
The only way to reliably get composite action between the H14 and the concrete pier is to use Shear Studs, or some type of shear lug. My experience is that contractor's hate doing this so I assume no composite action and use a beam sized with that in mind.

msquared48 (Structural)
17 Sep 10 22:42
Considering the low strength of the concrete encasing the pile so it can be easily removed to install the lagging, I would not rely on any composite action of the W shape with the 30" concrete pile.

If you are placing a permanent concrete foundation wall next to the W shapes, then composite stud action will work to attach the p[ile to the concrete wall, but, since the W shape is already loaded laterally, the composite action will only affect lateral deflections if the wall is further loaded laterally.

Have you considered using soil arching action to decrease the lateral load to the pile. If not, ask your geotech.
The load reduction may give you the lateral deflections that were recommended.