Foundation Engineering Design And Construction In Tropical Soils

This paper presents the back-analyses of field loading tests carried out with bored pile and drilled shaft founded in a tropical soil executed in the University of Brasília experimental research site. For this, a numerical simulation was carried via existing commercial application software denominated GEO4. This software computes the load-displacement curve of the pile's head plus, distribution of normal and shear forces along the pile's shaft. The Shear behavior of pile-soil interface is described using the elastic-plastic material model with Mohr-Coulomb yield condition. The complete response of any foundations is represented by determination of shaft and toe resistance plus settlement analyses. Hence, this paper focused in the determination of components of resistance (angle friction and cohesion) and settlement (Young Modulus) for this type of foundation, and explains and presents, in details, the software GEO4 from Fine Inc. Ltd. for foundation design. In relation to the cohesion, it was verified the important effect that this parameter have in the determination of shaft resistance. Moreover, few research topics nowadays deal with the determination of this particular parameter for bored piles. The assessment of geotechnical parameter is a vital component of geotechnical design and some formulation are also presented for this evaluation.

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III European Conference on Computational Mechanics

Solids, Structures and Coupled Problems in Engineering

C.A. Mota Soares et.al. (eds.)

Lisbon, Portugal, 5–8 June 2006

Numerical evaluation of bored piles in tropical soils by means of the geo-

technical engineering "GEO4" Fine Software

Anjos, G.J.M.

, Cunha, R.P.

†

, Kuklik, P.

‡

, Miroslav, B.

‡

Federal University of Pará, Belém, Brazil

anjosmiranda@pop.com.br

†

University of Brasília, Brasília, Brazil

rpcunha@unb.br

‡

Czech Technical University, Prague, Czech Republic

kuklikpa@mat.fsv.cvut.cz; broucekm @mat.fsv.cvut.cz

Keywords: Back-analysis, Bored Pile, Drilled Shaft, Geo4 (Pile), Mohr-Coulomb failure cri-

terion.

Abstract:

This paper presents backanalysis of field loading tests in bored pile and drilled shaft per-

formed on the tropical soil at the experimental research site of the University of Brasilia. The

numerical simulation was carried out using the commercial software GEO4 from FINE Inc.

This software computes the load-displacement curve on the pile head and the distribution of

normal and shear forces along the shaft. The shear behavior of the pile -soil interface is de-

scribed according to a modified Mohr-Coulomb's theory. This paper also focuses on the de-

termination of parameters of strength (angle friction and cohesion) and settlement (Young

modulus) for deep foundation. The use of GEO4 for foundation design is explained in details

herein. Cohesion was verified to be of important effect when calculating the shaft strength.

Moreover, few research topics nowadays deal with the determination of this parameter for

bored piles. The assessment of geotechnical parameters is a vital component of geotechnical

design and some formulations are also presented for this evaluation.

Anjos G.J.M., Cunha R.P., and Kuklik P.

1 INTRODUCTION

Foundation and in situ testing are two demanding research topics at the Brazilian capital,

Brasilia. This city was pre-designed and built in the early 60's to house the main Governmen-

tal administrative institutions and its public employees. Brasilia has increased and is still ex-

panding more than initially forecasted, thus enhancing the need of engineering solutions for

the local deep foundation problems. These problems are associated with some particular char-

acteristics of the predominant subsoil of the Fede ral District, i.e. the Brasilia "porous" clay.

This paper presents experimental results of field loading tests carri ed out on deep founda-

tions performed on the tropical soil of our experimental field at the University of Brasilia

(UnB). Two types of foundations were selected for this particular analysis, namely, a me-

chanically bored pile and a drilled shaft. Moreover, a numerical analysis is carried out in order

to simulate to response obtained on site.

The numerical analysis was done by means of a semi analytical procedure, coded in GEO4

software from FINE Inc. Ltd. This software computes the settlement and distribution of nor-

mal forces on the pile and also the actual shear resistance at any depth along the shaft. The

values of shear force are limited to that of pile-soil interface skin resistance. The values of

normal stress on this interface are a function of the user inputted geostatic earth pressure. Be-

sides that, the shear forces strongly depend on the friction behavior of the soil-pile interface,

which on the other hand is affected by fiel d construction techniques (displacement, non dis-

placement, etc).

In this particular case, the known analytical solutions for the shear response of layered sub-

soils are herein adopted (see [2, 3]). These solutions are related to the Young's modulus and

Poisson's ratio of the soil and the depth of influence zone around the pile. This zone ranges

from one to two and a half diameters around the pile, being variable during the analysis, i.e. it

increases with load increase.

In summary, the laboratory data is used together with in situ tests results to numerically as-

sess the response of two piles performed on our research site at the University of Brasilia.

2 METHOD OF ANALYSIS

The methodology was developed for layered subsoil. The pile is discretized into finite

number of cylindrical bar elements and the soil-pile interface is concentrated at nodal points.

For each pile element we determine the limit value of shear force transmitted by the pile skin.

To proceed, we first calculate the geostatic stress at a given depth using the following equa-

tion:

∑ (1)

where h

is the thickness and γ is the soil bulk modulus on the i

layer.

The ultimate shear force in the k

node T

k,lim

is obtained from Equations (2) and (3):

,lim

(tan)

σφ

′

+⋅

(2)

,lim ,lim

kkk

Trl

(3)

where τ

k,lim

is the ultimate shear strength (skin friction) proportional to the lateral earth pres-

sure on the soil-pile interface; σ is the normal stress on the i

layer; c' is the effective cohe-

sion; K is the coefficient of earth pressure;

' is the internal friction angle; r

is the pile radius

at the k

node and l

is the shear influence length around the k

node.

Anjos G.J.M., Cunha R.P. and Kuklik P.

The shear zone influence around the k

node is assumed as a spring [1]. The spring stiffness

is calculated from the known analytical formula given in Equation (4) (see [2]).

kkkk

krCC

⎛⎞

⎜⎟

⎝

⎛

⎜⎟

⎝⎠

⎠

⎞

(4)

where r

is the pile current radius; C

and C

are current Winkler-Pasternak parameters

around the k

node; and K and K are modified Bessel functions.

0 1

The spring stiffness at the base of the pile is given by Equation (5):

(5)

1 bb

krC

is the pile radius and C

where r

b 1b

is the Winkler-Pasternak parameter at the base of the pile.

Both Winkler-Pasternak parameters depend on the load level. An increase of that load level

corresponds to an increase of the influenced region around the pile. The soil strength is ex-

pressed in terms of its deformation and resistant values. The ideas presented above are incor-

porated into GEO4 and are further detailed and explored in [3].

During a standard analysis of a vertically loaded pile immersed in a layered soil, the fol-

lowing steps are performed:

a) The pile is subdivided into several elements. The number of elements is based on the ra-

tio length to diameter (ℓ/d ) of the pile, for which the program derives the solution of the soil

shear stiffness surrounding the pile. The length of each element must be at least 2.5 times

smaller than the pile diameter. The program nevertheless automatically assumes a minimum

ten elements to avoid spurious results. The soil shear stiffness is however still based on a ℓ/d

ratio of 2.5;

b) Each element is supported by a spring at the bottom end. The spring stiffness is derived

using the parameters C , C and modified Bessel's functions (Winkler-Pasternak model). C

1 2 1

and C

are functions of the Young modulus and Poisson's ratio of the soil. The depth of influ-

ence zone that affects the values of C

and C

1 2

is variable and changes with pile deformation

(settlement). For zero settlement, the depth of in fluence zone is set equal to one time the pile

diameter, whereas at the onset of geotechnical pile failure, it is set to 2.5 times the pile diame-

ter. The reliability of C

and C depends on a good assessment of soil deformation parameters;

1 2

c) For each pile element, the program determ ines the maximum value of shear force trans-

mitted to the shaft via skin friction. This is done by using a modification of Mohr Coulomb

failure criterion, as shown on Equation (2). The lateral stress is equal to the geostatic stress

times the coefficient of lateral earth pressure K , a user input value dependent on the pile con-

struction methodology;

d) Using both spring stiffness and limit force values (by means of maximum shear force),

the program starts to incrementally load the pile head. Forces developed on individual springs

of all elements are computed at each increment. These forces are then compared with the

maximum shear force (T

lim

) estimated on the previous step for each element. If the spring

force exceeds T

lim

, then the spring stiffness is reduced so that the force acting on the spring

equals T

lim

. The exceeding force for this particular load increment is redistributed into the re-

maining springs. Each load increment is iterated until the force developed in every spring is

Anjos G.J.M., Cunha R.P., and Kuklik P.

less than T

lim

. The gradual softening of individual springs leads to a final nonlinear

load-displacement curve for the loaded pile if geotechnical failure starts to take place during

the simulation, i.e. if pile, soil and loading conditions are such that soil plasticizes. Evidently,

at high load levels all springs can no more bear load increase and the pile starts to penetrate

into the soil. At that level, support is solely given by the base (heel) spring. It is worthy to

mention that there is no restriction with respect to the force magnitude on the base spring as

assumed by GEO4. This does not hold true for actual pile foundations cases though;

e) Eventually the program gives the load-displacement curve. By default, that curve is de-

rived for the maximum allowable displacement of 25 mm. The user, however, may change

this default value. Apart from that curve, the program also presents the distribution of normal

shear forces along the pile at each loading level. The program enables you to visualize the re-

lationship between skin friction and displacement at any pile element as well.

3 GENERAL SITE CHARACTERISTICS

The Federal District has a total area of 5814 km

and is limited in the north by the 15°30'

parallel and in the south by the 16° 03' parallel. In Figure 1, the dot on the small Brazilian map

represents the Federal District. The zoomed area in same figure shows Brasilia and the small

star corresponds to UnB, where the studied site is located.

Brasília

(1)

10 km

(1) UnB

Figure 1. Localization of the area of study.

The site has been extensively studied: (a) pile foundations have been constructed and ver-

tically and horizontally loaded; (b) advanced in situ tests, such as cone and dilatometer pene-

tration tests, standard penetration tests with torque measurements have been performed; (c)

soil suction has been measured; and (d) conventional triaxial, oedometer, direct shear and

standard characterization tests have been carried out. Some of those data can be found else-

where [4, 5]. Table 1 presents a summary of geotechnical parameters of our site.

More than 80 % of the Federal District is covered by a weathered laterite from terti-

ary-quaternary age. This soil, called "latosol", has been subjected to an intense leaching proc-

ess and presents variable thickness, ranging from a few centimeters to around 40 meters. The

Anjos G.J.M., Cunha R.P. and Kuklik P.

leaching process basically removes the silica and leaves the oxides and hydroxides of iron and

aluminum hydroxides in the soil [6, 7].

Table 1 General Geotechnical parameters from UnB.

a- Triaxial CK0D tests-Inundated Soil and at natural moisture content; b- Tr iaxial CK0D tests: Soil at natural humidity-50%

failure deviator stress; c- Triaxial K

tests: Soil at natural moisture content.

The superficial latosol has dark reddish coloration and displays much lower strength and

higher permeability than the bottom saprolitic-residual soil from slate, as it can observed in

many areas of D.F. Figure 2 shows the DMT lift off (p

) and 1.1 mm membrane expansion

) from the second DMT logging. The DMT logging was performed down to 12 m, close to

the top of the saprolitic slate. It followed the standard procedure with tests at 0.2 m interval

approximately. Figure 2 also presents average values of N

SPT

(Standard Penetration Test) for

our site.

4 INSTRUMENTATION AND FIELD LOAD TESTS

The slow maintained field loading tests were done in accordance with recommendations

put forward by the Brazilian NBR 12131 [8]. Those tests were performed using loading inter-

vals of 40 and 150 kN for the bored pile and the drilled shaft were, respectively.

Both top of foundation block and reaction frame were monitored for tilting and vertical

displacements, using six 0.01 mm precision dial gauges. A 1000 and 2000 kN hydraulic jack

were used together with a 100 N precision load cell to load the piles till failure condition. The

loading tests were carried out with the soil under natural moisture content conditions.

The field load test was performed on a mechanically bored, cast-in-place pile, with 0.3 m

in diameter and 8 m in length. This pile was excavated using a continuous hollow flight auger,

which was introduced into the soil by rotation. The hydraulic mechanical auger was assem-

bled on the back part of a truck especially devised for this type of work. The soil was removed

during continuous auger introduction and withdrawn. After reaching the required depth, the

auger was withdrawn leaving a freshly excavated hole, which was subsequently filled with

concrete. The drilled shaft has 0.7 m shaft diameter, 1.65 m bell diameter and 8 m length.

Figure 3 (a, b) shows the results from the load tests performed on these foundations.

Parameter Unit Range

Sand percentage % 12-27

Silt percentage % 8-36

Clay percentage % 80-37

Dry unit weight kN/m

10-17

Natural unit weight kN/m

17-19

Moisture content % 20-34

Degree of saturation % 50-86

Void ratio -- 1.0-2.0

Liquid limit % 25-78

Plastic limit % 20-34

Plasticity index % 5-44

Drained cohesion

kPa 10-34

Drained Friction angle

degrees 26-34

Young's Modulus

MPa 1-8

Coefficient of Collapse % 0-12

Coeff. Earth Press (K0)

-- 0.44-0.54

Coeff.Permeability cm/s 10

-6

-10

-3

)

m/s 10

-8

-10

-5

Anjos G.J.M., Cunha R.P., and Kuklik P.

Figure 2. DMT and SPT results for the site [3].

0 50 100 150 200 250 300 350

Load (kN)

Displacements (mm

(a)

0 250 500 750 1000 1250 1500 1750 2000

Load (kN)

Displacements (mm

(b)

Figure 3. Results of load tests in (a) Bored Pile and (b) Drilled Shaft at UnB site.

5 NUMERICAL SOFTWARE

The numerical backanalysis of the pile behavior was carried out using the commercial

software GEO4 from FINE Inc. Ltd., headquarters in Prague, Czech Republic. Although sim-

ple to use, this software has a high potential for application in practical civil engineering pro-

jects, not only for pile foundation design but also for retaining walls, shallow foundations,

embankments, pavements, diaphragm walls, slope stability. There are personalized modules

for each aforementioned technical area.

The whole GEO4 software package was donated to the Geotechnical Post-Graduation Pro-

gram at the University of Brasilia to be evaluated and tested, as well as to be used in our geo-

technical researches. The module Pile can derive the full load-displacement curve of a

Saprolitic

Slate

Reddish

Sandy

Clay

lateritic

transition

p0 (MPa)

p1 (MPa)

N x 10.0

0 0.2 0.4 0.6 0.8 1 1.2 1.4

, p

(DMT) e N (SPT)

Anjos G.J.M., Cunha R.P. and Kuklik P.

vertically loaded pile, as well as its load transfer mechanism (structural load along pile depth

for each test load level). The horizontal behavior of the pile can also be simulated on this

module. Unfortunately this latter characteristic was not tested herein due to difficulties in-

volved with lateral load tests.

The module Pile can be used to determine the vertical bearing capacity of a pile from the

load-displacement curve. A database of parameters, such as internal friction angle, cohesion,

bulk weight and Young modulus, for various types of soil and rock is also available in this

module. As a result, the program gives the load-displacement curve till a pre-specified limit

deflection or failure. The pile vertical bearing capacity is related to this limit deflection.

6 RESULTS AND DISCUSSION

A comparison between backanalyzed geotechnical parameters and experimental data in

terms of load transfer curves and numerical predictions of average skin friction and pressure

at the bottom of the pile will be presented and discussed as follows.

6.1 Geotechnical Parameters

The backanalysis consisted of selecting by trial and error input geotechnical parameters for

the GEO4 module Pile . The software derived the load-displacement curves of the pile that

later were compared with those obtained from experiment (Figures 4 and 5).

In order to obtain those curves some criteria were put in mind:

a) Be reasonably representative of the geological nature of soil deposits herein studied, i.e.

be in the range of known values gathered from other sources, such as laboratory, in situ test-

ing, or backanalyzed parameters obtained from other programs [11];

b) Be considered as approximate values, or "estimated guess" of real values, due to simpli-

fications built in the numerical and experimental analyses;

c) Take the deposit natural spatial variability into consideration, in special with respect to

ground level differences and geology between the sites;

d) Take the deposit natural special variability into consideration, given its tropical and re-

sidual origin. This latter aspect has already been exemplified for our site, via dilatometer test

results [12].

Table 2 presents the backanalyzed geotechnical parameters for the three testing sites. Al-

though more research is required, those parameters can already be used to carry out simula-

tion of piles performed on similar deposits to thos e herein studied. It is worthy to mention that

a parametric and simulation analysis was already presented in [13].

It is important to mention that similar load -displacement curves can be obtained by slight

different combinations of geotechnical parameters input. Indeed, it has been demonstrated us-

ing the software PLAXIS that, before pursuing the back-analysis, the magnitude order of pa-

rameter, such as cohesion and friction angle, must be known a priori [16]. This order of

magnitude can be obtained from several sources, namely, in situ and laboratory tests, or re-

gional experience. In our case, the friction angle has low seasonal variation and, from our ex-

perience, it ranges from 27º to 30º. Cohesion, on the other hand, has great variability, in

particular due to changes of matric suction. In this paper, it is obtained according to the for-

mulation presented in [15]. The value of K was set around that of K

. The Young modulus

was left to vary above the one shown in Table 1. This latter assumption is based on a backana-

lysis carried out in [18].

Anjos G.J.M., Cunha R.P., and Kuklik P.

0 50 100 150 200 250 300 350

Load (kN)

Displacements (mm

Load Test

Geo4 ( k=0.65)

Figure 4. Load-displacement curve for the bored pile.

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Load (kN)

Displacements (mm)

Load Test

Geo4 (k = 0,65)

Figure 5. Load-displacement curve for the drilled shaft.

Depth (m)

c' (kPa) E (MPa) Observations

(º) γ

(kN/m³)

0 a 2 36.6 4 13.5 0.29 23

2 a 6 29.8 10 14.4 0.33 20

6 a 8 31.4 9 15.0 0.32 22

8 a 9 (Base) 33.1 7 18.0 0.31 23

9 a 12 33.2 7 17.8 0.31 24

12 a15 37.1 3 18.5 0.28 35

concrete

= 24 kN/m³

= 16 GPa

ρ = 27 mm

E = 18.6 + 1.7q

→ MPa →E MPa) k = 0.65 (q

Table 2 Backanalyzed geotechnical parameters from UnB via GEO4.

φ→ [14]; c' → [15]; γ

→ [16]; ν→ [17]

is a average value of point resistance in CPT Test for each layer

E is a empirical formulation derived by local experience.

Anjos G.J.M., Cunha R.P. and Kuklik P.

Site investigation and field load testing are fundamental to safely design deep foundations,

and, whenever possible, they should be included in the budgetary analysis of any foundation

work. As presented in [13], once the field load-displacement curve of a pile can be forecasted,

we believe that GEO4 is also able to simulate other piles in the same site but under distinct

geometric conditions. Of course, more research is required to fully prove that.

Pile construction method is another issue driving differences on backanalysis parameters,

for instance, for the same geology, distinct values of Young moduli and coefficients of earth

pressure are obtained. Actually, the latter is believed to be the most affected by construction

method. Different boring techniques certainly influence the surrounding excavated soil; how-

ever, such influence is difficult to be distinguished from that caused by geology variability.

Although construction technique influence is readily recognized, its quantification was not

possible in this work due to lack of more data.

7 CONCLUSION

This paper emphasized the application of a numerical methodology to derive backanalyzed

geotechnical parameters, useful for design of projects in the civil engineering foundation

field. After being calibrated, this methodology can be further used in parametric analysis of

other different pile geometries performed on the site of study, therefore, optimizing the foun-

dation design.

The mathematical model was based on a well-established solution coded on the software

GEO4. Simulations of instrumented field loaded, large scale, bored foundations have vali-

dated the versatility and potential of this program for practical use. This also holds when ana-

lyzing non classical case histories as those ones herein considered, i.e. foundations performed

on tropical and stratified soils of the Federal District, Brazil.

From the previous discussion, the following conclusions are addressed:

1. For the same pile construction technique and numerical methodology, the values pre-

sented on Table 2 are reasonable description of average magnitude values to be used in practi-

cal applications and parametric analyses for sites under similar conditions. However, a more

refined analysis might be desirable to lessen differences;

2. The software has proven to well represent the response of vertically piles performed on

tropical stratified deposits of the Federal District. Some dispersion on the results may be ac-

counted for distinct geological, topographical and pile construction conditions;

3. An initial calibration of the software using large-scale field load testing results is sug-

gested before using the software on a real design. This pre-backanalysis will account for the

geology and pile construction method used on site;

It is finally pointed out that, due to reduced number of foundations and limited spatial size

of the area of study, it is evident that more investigation is necessary. Nevertheless, the meth-

odology for data interpretation, the gained experience and the presented results can be seen of

practical interest for those involved with foundation design in Brasilia and elsewhere in Brazil.

REFERENCES

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[2] Kuklík, P. (1983): Computation of displacements and stresses in layered sub soils, PhD

thesis, Czech Technical University, Prague, Czech Republic, May 1983.

[3] FINE LTd.: Software product GEO 4 (www.fine.cz).

Anjos G.J.M., Cunha R.P., and Kuklik P.

[4] Cunha, R.P., Jardim, N.A. and Pereira, J.H.F. (1999). In situ characterization of a tropi-

cal porous clay via dilatometer tests. Geo-Congress 99 on Behavioral Characteristics of

Residual Soils, ASCE Pub. 92, Charlotte, pp.113-122.

[5] Cunha, R.P., Pereira, J.H.F., Soares, J.M., Mota, N.M.B. and Poulos, H.G. (2001).

Backanalyses of field loading tests on deep foundations in a tropical clay. XV ICSMGE ,

Istanbul, Vol. 2,.pp. 869-872.

[6] US Bureau of Mines. (1996). Dictionary of mining, mineral, and related terms. Second

Edition, U.S. Department of the interior.

[7] Cunha, RP and Camapum de Carvalho, J. (1997). Analysis of the behavior of a drilled

pier foundation in a weathered, foliated and folded slate. XIV ICSMGE , Hamburg, pp.

785-786.

[8] NBR 12131 (1996). Loading tests of deep foundations. Brazili an Association of Tech-

nical Norms.

[9] Bittar, Z and Sejnoha, J. (1996). Numerical methods in structural mechanics . ASCE

Press, Thomas Telford, New York, 422 p.

[10] Kuklík, P. and Masopust, J. (2000). Shear skin transfer of concrete drilled piles testing

and modelling. Our World in Concrete and Structures . Singapore. CI-Premier, pp. 373-

380.

[11] Cunha, R.P., Pereira, J.H.F., Soares, J.M., Mota, N.M.B. and Poulos, H.G. (2001).

Backanalyses of field loading tests on deep foundations in a tropical clay. XV ICSMGE ,

Istanbul, Vol.2,.pp. 869-872.

[12] Mota, N.M.B., Cunha, R.P. and Cortopassi, R.S. (2000). Influence of the stratigraphy

and penetration system on the results of dilatometer tests carried out in the porous

Brasília clay. IV Int. Symp. on Structures, Geotechnics and Construction Materials ,

Santa Clara, pp. 80-87. (In Portuguese).

[13] Cunha, R.P., Soares, J.M., Pereira, J.H.F. and Silva, C.M. (2002). Numerical analyses

of a field loading test in deep foundation founded in tropical soil of the Federal District

of Brazil. Argentinean National Congress of Soil Mechanics , Trelew, CD Rom, Session

VII. (In Portuguese).

[14] Kulhawy, F.H., Mayne, P.W. (1990). Manual on Estimating Soil Properties for Founda-

tion Design, Rpt EL-6800, EPRI, Palo Alto.

[15] Owuama, C.O. (2002). Semi-Empirical Method of Interpretation of CPT Data. JKAU:

Eng. Sci., Vol 14, (1), 31-33 (1423 A.H/2002 A.D).

[16] Mota, N.M.B. (2003). Ensaios Avançados de Campo na Argila Porosa Não Saturada de

Brasília: Interpretação e Aplicação em Projetos de Fundação. Tese de Doutorado, Publi-

cação G.TD-013A/03, Departamento de Engenharia Civil e Ambiental, Universidade de

Brasília, Brasília, DF, 336 p.

[17] Duncan, J.M. and Mokwa, R.L. (2001) Passive Earth Pressures: Th eories and Tests J.

Geot. and Geoenv. Engr. ASCE, Vol. 127, No. 3, 248-257.

[18] Perez, E.N.P. (1997). The use of the elasticity theory to determine the Young Modulus of

the soil around vertically loaded piles founded in the Brasília porous clay. M.Sc. Thesis.

Geotechnical Post-Graduation Program, University of Brasília. Publication G.DM-

049A/97, 146 p. (In Portuguese).

... The provided geotechnical parameters were obtained in a comprehensive laboratory and in-situ testing project carried out as a part of the postgraduate research program at UnB. Conventional classification was performed together with more sophisticated laboratory tests such as double oedometer and collapse tests, triaxial K0 and triaxial CK0D tests, permeability tests and direct shear tests with samples under distinct orientations. The subsoil profile of the experimental site has been examined by number of researchers and recently described by Mota [8] and Anjos [2] to name a few. Authors characterize the profile of experimental site and provide material parameters for the Mohr-Coulomb model. ...

... Since the utilization of strain sensor along the pile reinforcement provided the distribution of shear stress acting on the pile shaft it was also possible by this author to identify distinct soil layers and to determine their approximate material properties. Parameters in the soil profile published by Anjos [2] were obtained via back calculation analysis with the results from an isolated bored pile field loaded in the experimental site of the University of Brasilia. This backward analysis was performed with the GEO4 foundation software [7], which is based on semi analytic method as described in Anjos [1]. ...

... Owning to the absence of underground water in the profile at the testing period, no pore pressure was assumed during the analysis. The soil environment was modeled by five horizontal layers when employing laboratory and in situ parameters (Table 2) or by six layers when using the back analyzed parameters published by Anjos [2] ( Table 3). ...

Tomas Janda

The contribution presents a 3D finite element analy sis of a single experimental pile founded in tropic al porous clay. Three subsoil profiles obtained by different approa ch are used in the analysis. The first subsoil prof ile is deduced from a combination of conventional laboratory and in situ tests. The second is found by the means of backward analysis employing semi analytic method. The third set of ma terial parameters is deduced from the load settleme nt curve of single pile analyzed using finite element method. T he comparison of the material parameter is finally provided together with the discussion on the observed differences.

... where ∆ z is the distance between the springs at that depth and k s is the subgrade reaction modulus kN/m 3 , which is calculated from the various methods, such as a linear distribution, constant distribution, the equation provided in CSN 73 1004, the equation given by Matlock and Reese, and the equation given by Vesic [28]. The soil spring stiffness in the vertical direction consists of the end bearing stiffness K vb and skin friction resistance stiffness K v f , as shown in Figure 3. ...

Hyun-Gi Kim
Bum-Joon Kim

Various types of support structures for offshore wind turbine have been developed, and concrete structures have attracted attention due to many advantages. Although many studies have been conducted on the design of the existing steel structures, information and research on the design of concrete support structures are insufficient. Therefore, in this paper, a structural analysis model of conical concrete support structure (CCSS) is established and design optimization is presented. A detailed performance evaluation and the design of prestressed concrete were performed under the marine conditions of Phase 1 test site of southwest offshore wind project in Korea. The fluid–soil–structure interaction (FSI) was applied using the added mass method and soil spring model to represent the effects of water and soil. With the result of quasi-static analysis, a post-tensioning design was implemented by applying prestressing steel, and CCSS showed sufficient rigidity. From the natural frequency analysis, CCSS has a dynamic structural stability, and, in response spectrum and time-history analyses, the CCSS was safe enough under the earthquake loads. The methods and conclusions of this study can provide a theoretical reference for the structural analysis and design of concrete support structures for offshore wind turbines.

... The commercial software Geo4 from FINE Inc. Ltd. is a simple to use software with a high potential for application in practical civil engineering projects, not only for pile founda- tion design but also for retaining walls, shallow foundations, embankments, pavements, dia- phragm walls, and slope stability. There are personalized modules for each aforementioned technical area ( Anjos et al. 2006). This software was donated to the post-graduation program in geotechnical engineering of the University of Brasilia to be evaluated and used in related geotechnical investigations. ...

Numerical simulations of field loading tests carried out on bored pile and drilled pier founded in the tropical collapsible soil of the experimental site at the University of Brasilia were analyzed herein with commercial software packages. These packages compute the load-displacement curve of the pile head plus the distribution of normal and shear forces along the pile shaft. An elastic-plastic material model with Mohr-Coulomb yield condition was applied to describe the shear behavior of the pile-soil interface. The shaft and toe resistances plus settlement curve were used to represent the overall mechanical response of the foundations. The comparative analyses allowed a better understanding of the advantages and shortcomings in applying such techniques to numerically simulate excavated foundations in this site.

... The commercial software Geo4 from FINE Inc. Ltd. is a simple to use software with a high potential for application in practical civil engineering projects, not only for pile foundation design but also for retaining walls, shallow foundations, embankments, pavements, diaphragm walls, and slope stability. There are personalized modules for each aforementioned technical area (Anjos et al. 2006). This software was donated to the post-graduation program in geotechnical engineering of the University of Brasilia to be evaluated and used in related geotechnical investigations. ...

... Parameters in the soil profile published by Anjos (2006) were obtained via back calculation analysis with the results from an isolated bored pile field loaded in the experimental site of the University of Brasília. This backward analysis was performed with the Geo4 foundation software (Fine, 2007), which is based on semi analytic method as described in Anjos et al. (2006). The resulting profile is shown in Table 3, based on a layering sequence defined with local experience plus the results of cone penetration tests in this same site. ...

This paper deals with Plaxis 3D finite element simulations of the mechanical response of deep foundations founded in a collapsible tropical soil. Main attention is initially paid to differences between single continuous flight auger (CFA) pile behavior and the behavior of CFA piles in standard groups. The numerically computed load-settlement curves are compared to field load test data obtained at the experimental research site of the University of Brasilia (UnB), leading to conclusions about the appropriateness of adopting laboratory, in situ or back calculated parameters as input of numerical programs that simulate 3D foundation systems. Further, the contribution of the contact surficial soil/top raft is numerically examined by simulating the behavior of identical "piled raft" systems founded in the same site. The numerical simulated results of "piled raft" and standard pile group systems are then compared in terms of load capacity, system stiffness, load share between pile tip, shaft and raft, and mean developed lateral pile shaft friction. Having the results at distinct loading stages, as at working and failure levels, the analyses show the differential behavior, and design obtained responses, one may expect from conventional pile groups and "piled rafts" of CFA floating piles when founded in tropical soils. It is a mixed theoretical/experimental paper with practical interest for foundation designers and constructors.

Fred H. Kulhawy
Paul W. Mayne

This manual focuses on the needs of engineers involved in the geotechnical design of foundations for transmission line structures. It also will serve as a useful reference for other geotechnical problems. In all foundation design, it is necessary to know the pertinent parameters controlling the soil behavior. When it is not feasible to measure the necessary soil parameters directly, estimates will have to be made from other available data, such as the results of laboratory index tests and in-situ tests. Numerous correlations between these types of tests and the necessary soil parameters exist in the literature, but they have not been synthesized previously into readily form in a collective work. This manual summarizes the most pertinent of these available correlations for estimating soil parameters. In many cases, the existing correlations have been updated with new data, and new correlations have been developed where sufficient data have been available. For each soil parameter, representative correlations commonly are presented in chronological order to illustrate the evolutionary development of the particular correlation. The emphasis is on relatively common laboratory and in-situ tests and correlations, including those tests that are seeing increased use in practice.

J. Ortún-Terrazas

This teaching book is titled "METHODS OF ANALYSIS FOR STRUCTURAL MECHANICS". It aims to be a tool for learning and for consulting the phases involved in the development of a computational calculation. This book explains in a practical way the principles that govern the method of finite elements, the methods of models scanning, advice in meshing, characterization of materials, computational methods and how to interpretate results. It is a theoretical-practical book since it incorporates practical examples of some software used in the industry. The examples are about problems that can be found in engineering sectors such as product design, mechanical analysis or biomechanical study.

Renato P. Cunha
N.A. Jardim
J. H. F. Pereira

This paper presents the interpretation of several Marchetti dilatometer tests carried out in the University of Brasilia experimental research site. This site is comprised by an approximate 8 to 10 m thick deposit of the typical unsaturated clay of Brasilia, found in large areas of the brazilian Central Plateau. The Brasilia porous clay is collapsible under saturation and has been extensively studied in the laboratory by means of traditional CK0D and triaxial K0 tests, as well as standard characterization, permeability, X-ray, direct shear and double oedometer tests. The dilatometer testing data was interpreted according to traditional methodologies developed for saturated soils. These results were then compared to the referential laboratory ones, leading to conclusions of practical and academic interest for those who need geotechnical parameters for the engineering design.

Chukwunonye Ozioma Owuama

Cone penetration test (CPT) is a reliable technique for measuring subsurface soil properties. In most CPT measurements the mobilized cone tip resistance is representative of the formation conditions. A Semi-empirical method of interpretation of such data is presented. The method was developed from a theoretical concept. Angle of internal friction, cohesion and ultimate bearing capacity of soils can be directly obtained from observed tip resistance. The results of the interpretations are in good agreement with observed conditions. The method is particularly suitable in cases where the accuracy of the measured skin friction is in doubt.

K. S. Wong
Ci Teh

A simplified numerical procedure for the analysis of negative skin friction on piles in a layered soil deposit is proposed. Pile-soil interface behavior is modeled by nonlinear soil springs. A framework for determining the model parameters from conventional soil tests data has been established. This procedure is used in the back-analysis of seven well-documented test piles in different soil deposits. The good agreement between the computed and the measured values for all seven piles confirmed the validity of the proposed approach.

I. F. Obraztsov

The papers contained in this volume focus on numerical, numerical-analytical, and theoretical methods for dealing with strength, stability, and dynamics problems in the design of the structural elements of flight vehicles. Topics discussed include the solution of homogeneous boundary value problems for systems of ordinary differential equations modified by a difference factorization method, a study of the rupture strength of a welded joint between plates, singular solutions in mixed problems for a wedge and a half-strip, and a thermoelasticity problem for an open-profile cylindrical shell with a localized temperature field.

J. Michael Duncan
Robert L. Mokwa

The magnitude of the passive earth pressure that resists the movement of a structure is controlled by the amount the structure moves and the direction in which it moves, strength and stiffness of the soil that resists its movement, friction or adhesion on the interface between the structure and soil, and shape of the structure. The Log Spiral Theory, corrected for 3D effects, provides an accurate means of computing ultimate passive pressures. A hyperbolic expression, together with estimated values of soil modulus and ultimate resistance, provides a means of estimating the relationship between structural movement and passive resistance. It is essential that the soil strength and stiffness used in making these estimates should be appropriate for the soil and the drainage conditions involved. The results of an undrained passive pressure load test in stiff sandy silt and a drained passive pressure load test in well-graded gravel are compared with passive pressures computed using the methods discussed. Reasonable agreement between the calculated and measured values shows that the Log Spiral Theory, corrected for 3D effects, and the hyperbolic load-deflection relationship provide an adequate means of estimating passive resistance for a wide range of conditions.

Thrush, Paul W., Comp

This dictionary contains about 55,000 terms with approximately 150,000 definitions. These terms are of both a technical and local nature and apply to metal mining, coal mining, quarrying, geology, metallurgy, ceramics and clays, glassmaking, minerals and mineralogy, and general terminology. Petroleum, natural gas, and legal mining terminology, unless of a general nature, has been excluded, as has been foreign terminology where there is an English equivalent. Those Spanish-American and Mexican terms still used in the Southwestern United States have been retained. Many terms are identified by the country or area of origin. Others can be identified by examining the source following each definition. These sources are completely identified, with full bibliographical information, in the list of authorities and sources in the back of the dictionary. A consultation of this list can also aid in establishing the recency of the definition. (Author/PR)

Software product GEO 4 (www.fine.cz)

Fine Ltd

FINE LTd.: Software product GEO 4 (www.fine.cz).

Shear skin transfer of concrete drilled piles testing and modelling. Our World in Concrete and Structures

P Kuklík
J Masopust

Kuklík, P. and Masopust, J. (2000). Shear skin transfer of concrete drilled piles testing and modelling. Our World in Concrete and Structures. Singapore. CI-Premier, pp. 373-380.

Source: https://www.researchgate.net/publication/251160944_Numerical_evaluation_of_bored_piles_in_tropical_soils_by_means_of_the_geotechnical_engineering_GEO4_Fine_Software

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Foundation Engineering Design And Construction In Tropical Soils

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