Aula 11c - Consoli Vendruscolo (ASCE 2003)

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alternative for design is therefore proposed in this work by devis-
ing a system in which a layer of sand, or sand-fiber, treated with
Portland cement, is built over a residual soil stratum; shallow
foundations could then be placed on this layer. The use of com-
pacted layers made up of either soil only ~Consoli et al. 1997! or
soil mixed with cementing agents such as Portland cement ~Ste-
fanoff et al. 1983; Vendruscolo 1996; Sales 1998; Tessari 1998!
and lime ~Thome´ 1999! has been increasingly investigated in the
Layered System and Site Characterization
Sand-cement and sand-cement-fiber layers were built on the top
of a residual soil stratum. The characteristics of the residual soil
site and the improved upper layers are presented in the next sec-
tions.
Residual Soil Stratum
The residual soil characteristics at the UFRGS experimental site
have been determined through an extensive testing program,
which comprises laboratory tests, mainly triaxial tests, and in situ
tests ~cone, standard penetration, cross-hole, down-hole, dilatom-
eter, Me´nard pressuremeter at different depths, steel plate, and
concrete footing load tests!. The site investigation has revealed a
homogeneous upper layer ~3.5 m depth! of sandy-silty red clay,
which is classified as low plasticity clay according to the Unified
Soil Classification System. Grain size data indicate that the soil is
6% medium sand, 38% fine sand, 32% silt, and 24% clay. The
average bulk unit weight ranged between 17.7 and 18.2 kN/m3;
the moisture content was typically 24.5–26.0%; the degree of
saturation was around 78%, and the void ratio varied between
0.80 and 0.86. Atterberg limits were: liquid limit of 43% and
plastic limit of 22%, which yield a plasticity index of 20%. Un-
1Associate Professor, Dept. of Civil Engineering, Federal Univ. of Rio
Grande do Sul, Av. Osvaldo Aranha, 99, 3. andar, 90035-190, Porto
Alegre, Rio Grande do Sul, Brazil. E-mail: consoli@vortex.ufrgs.br
2Research Assistant, Dept. of Civil Engineering, Federal Univ. of Rio
Grande do Sul, Av. Osvaldo Aranha, 99, 3. andar, 90035-190, Porto
Alegre, Rio Grande do Sul, Brazil.
3Associate Professor, School of Engineering and Architecture, Catho-
lic Univ. of Pelotas, Rua Fe´lix da Cunha, 412, 96010-000, Pelotas, Rio
Grande do Sul, Brazil.
Note. Discussion open until June 1, 2003. Separate discussions must
be submitted for individual papers. To extend the closing date by one
month, a written request must be filed with the ASCE Managing Editor.
The manuscript for this technical note was submitted for review and
possible publication on November 7, 2000; approved on May 28, 2002.
This technical note is part of the Journal of Geotechnical and Geoenvi-
ronmental Engineering, Vol. 129, No. 1, January 1, 2003. ©ASCE, ISSN
1090-0241/2003/1-96–101/$18.00.
Behavior of Plate Load Tes
with Ceme
Nilo Cesar Consoli1; Ma´rcio Antonio Vendru
Abstract: The load-settlement response from three plate load
homogeneous residual soil stratum, as well as on a layered system
sand-cement fiber—overlaying the residual soil stratum, is discu
increased bearing capacity, reduced displacement at failure, and c
load, the bearing capacity dropped towards approximately the same
The addition of fiber to the cemented top layer maintained roughl
ductile behavior. A punching failure mechanism was observed in
tension cracks being formed from the bottom to the top of the lay
sand-cement-fiber top layer, the failure occurring through the for
allowed the stresses to spread through a larger area over the resid
DOI: 10.1061/~ASCE!1090-0241~2003!129:1~96!
CE Database keywords: Fiber reinforced materials; Cements;
Introduction
Thick residual soil strata with reduced bearing capacities are
found to cover extensive areas in tropical and subtropical regions,
including densely populated and industrial areas in southern Bra-
zil. Current solutions for foundation design employing spread
footings bearing directly on such soils might lead to low admis-
sible pressures associated with significant settlements ~e.g., Con-
soli et al. 1998!. On the other hand, in many cases, the use of
deep foundations gives rise to an excessive increase in cost. An
96 / JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGIN
ts on Soil Layers Improved
t and Fiber
colo2; and Pedro Domingos Marques Prietto3
sts ~300 mm diameter, 25.4 mm thick! carried out directly on a
rmed by two different top layers ~300 mm thick!—sand-cement and
ed in this technical note. The utilization of a cemented top layer
nged soil behavior to a noticeable brittle behavior. After maximum
value found for the plate test carried out directly on the residual soil.
the same bearing capacity but changed the postfailure behavior to a
e field for the load test bearing on the sand-cement top layer, with
r. A completely distinct mechanism was observed in the case of the
ation of a thick shear band around the border of the plate, which
l soil stratum.
situ tests; Laboratory tests; Plates; Loads.
last few years. Such studies have shown a noteworthy increase in
the bearing capacity of spread foundations when placed on im-
proved layers.
The results presented herein are part of a comprehensive test-
ing program being run at the experimental site of the Federal
University of Rio Grande do Sul ~UFRGS!, located in the city of
Cachoeirinha, in southern Brazil, whose main purpose is the over-
all understanding of the different mechanisms of load transfer for
shallow foundations bearing on layered systems overlaying re-
sidual soil strata.
EERING / JANUARY 2003
2
soil layer, once they have shown a noticeable reduction in soil
NIC
sures of 20, 60, and 100 kN/m , are concisely presented in Figs. 1
and 2 and Table 1. Such results give a clear indication of the
existence of the mentioned bonded structure in the upper residual
Fig. 2. Peak and residual strength envelopes
JOURNAL OF GEOTECH
stiffness with increasing confining stresses, clearly evidencing the
breakage of soil structure. Further information on laboratory and
in situ residual soil characterization can be found in previous
work by Consoli et al. ~1998!.
Sand-Cement and Sand-Cement-Fiber Top Layers
Before the construction of the sand-cement and the sand-cement-
fiber top layers, a 1.2-m-thick layer of the upper residual soil,
described in the previous section, was removed throughout the
testing area. After removal, two improved soil layers, 300 mm
thick and 2.25 m2 each (1.5 m31.5 m), were built over the re-
sidual soil in three consecutive layers, each 100 mm thick, by
using a vibratory plate to reach the specified relative density of
70% ~established as a reference value for comparison among the
mixtures!, and then allowed to cure for 28 days before being
tested. The improved soils were prepared in a rotating drum
mixer, by mixing air-dried sand, Portland cement ~7% by weight
of dry sand!, water ~10% moisture content!, and polypropylene
fiber ~0.5% by weight of dry sand plus cement! when appropriate.
The source, the physical/mechanical properties, as well as the
amounts of the materials used to build the improved top layers are
as follows: The sand used, borrowed from a coastal region near
the city of Osorio, in southern Brazil, is classified as nonplastic,
uniform fine sand according to the Unified Soil Classification
System; the specific gravity of solids is 2.62 and the grain size
distribution is 100% fine sand with an effective diameter of 0.16
mm; the uniformity and curvature coefficients are, respectively,
1.9 and 1.2; the minimum and maximum void ratios are, respec-
tively, 0.57 (gd max516.7 kN/m3) and 0.85 (gd min
514.2 kN/m3). At this point, it is important to mention that the
use of the local residual soil instead of the uniform sand in the
improved top layers was not considered, given that it had a cer-
tainplasticity that might bring difficulties in the mixing process
and make it impossible to ensure an uniform soil-fiber-cement
mixture. Rapid-hardening Portland cement, potable water, and
chopped polypropylene fibers were used throughout this investi-
gation. The average characteristics of the fiber were: 24 mm
length, 0.023 mm diameter, specific gravity of 0.91, tensile
strength and elastic modulus of 120 and 3,000 MN/m2, respec-
tively, and linear strain at failure of 80%.
Regarding the amounts of materials used in the present study,
for the construction of 1 m3 of compacted sand-cement and/or
sand-cement-fiber layers, it has used approximately 1,485 kg of
dry sand, 104 kg of cement, 159 L of water, and 8 kg of fiber
~when appropriate!.
It is worth pointing out that a moisture control study was pre-
viously performed to determine the target moisture content for the
sand-cement/sand-cement-fiber mixtures. The moisture content
was selected so that small changes in the amount of water did not
significantly change the specimen density. Also, during the field
mixing process, it was found important to pour the water previ-
ously to the fibers, to prevent floating. Visual and microscope
examination of exhumed field specimens proved the mixtures to
be satisfactorily uniform.
Laboratory and Field Testing Program
Triaxial Tests
Static drained conventional triaxial tests were carried out on sand-
cement and sand-cement-fiber specimens ~cylindrical, 50 mm di-
AL AND GEOENVIRONMENTAL ENGINEERING / JANUARY 2003 / 97
like transported soils with similar grain size distribution, this re-
sidual soil is the product of in situ weathering, which decreased
density, increased porosity, and allowed the precipitation of com-
pounds creating inter-particle bonding. Results of drained triaxial
compression tests with internal measurement of deformations,
carried out under full saturation, at the effective confining pres-
Fig. 1. Triaxial test response for residual soil, sand and both sand-
cement and sand-cement-fiber mixtures
Four dial gauges with divisions of 0.01 and 50 mm travel were 10%, the results show that fiber inclusion consistently improved
Table 1. Summary of Triaxial Test Results
used for settlement measurement. The gauges were fixed to a
reference beam and supported on external rods. The load was
applied in cumulative equal increments of not more than one-
tenth of the estimated ultimate bearing capacity. Each increment
was maintained until the following criterion was achieved:
Ln2Ln21<0.05•~Ln2L1! (1)
where Ln5average dial gauge reading at a specified time interval
t; Ln215average dial gauge reading immediately previous to Ln ;
and L15first reading of the stage of loading taken just after stage
loading appliance, with a minimum duration of 30 min, according
to Brazilian standard NBR-12131 ~Foundations 1991!, which is
in accordance with the standard ASTM D1194-94 ~Standard
1998!. As soon as the loading reached the maximum bearing ca-
pacity, the alternative procedure described in the item 4.9, note 5,
of the standard ASTM D1194-94 ~Standard 1998! was adopted to
obtain the postpeak behavior. At this point, the load was applied
postpeak behavior, increasing both the ultimate cohesion intercept
and the friction angle. Adding fibers changed the ultimate cohe-
sion intercept from 59 to about 76 kN/m2 and the ultimate friction
angle from 34 to 47°. This behavior probably reflects microstruc-
tural changes resulting from either the fiber addition by itself or
the interaction between cementation and fiber reinforcement. Un-
doubtedly, one of the main advantages of fiber reinforcement
when applied to cemented soils is the improvement in material
ductility.
Values of secant deformation modulus calculated at 0.1% axial
strain are presented in Table 1. Data clearly show that cementa-
tion strongly increased sand modulus while fiber inclusion re-
duced the initial stiffness of the sand-cement mixture, though it
remained considerably higher than that obtained for either the
sand or the residual soil. Also from Table 1, it is worth noting the
significant reduction in the stiffness of the residual soil with the
increasing confining stress, evidencing that the soil structure was
98 / JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL ENGINEERING / JANUARY 2003
ameter, 100 mm high!, which, to reduce disturbance, were
trimmed from large blocks retrieved from the respective layers in
the field. Tests were run under full saturation at the effective
confining pressures of 20, 60, and 100 kN/m2, which are consis-
tent with realistic assumptions for shallow foundation placed on
improved soil layers. Back pressures of up to 500 kN/m2 ensured
B values of at least 0.9. Axial strain and radial strain were moni-
tored inside the triaxial cell by Hall effect sensors, which enable
accurate estimation of specimen stiffness ~Clayton and Khatrush
1986; Clayton et al. 1989!. Volumetric strain was measured by an
Imperial College electrical transducer ~Maswoswe 1985! con-
nected to the drainage outlet. A sufficiently low axial strain rate
~0.017%/min! ensured full drainage during shear. Membrane and
area correction followed the recommendations proposed by
La Rochelle et al. ~1988!.
Plate Load Tests
The field testing program was carried out at the experimental site
previously described. The tests were conducted using 300-mm-
diam, 25.4-mm-thick, rigid circular steel plates. The setup used
for conducting the plate load tests was in accordance with the
standard ASTM D1194-94 ~Standard 1998!. The load was applied
through a system comprising a hydraulic jack, a reaction beam,
and a load platform, and measured using a calibrated load cell.
Material tested in triaxial
compression
Void
ratio
Initial mean
effective stress
~kN/m2!
Peak cohesion
intercept
~kN/m2!
Residual soil ~Consoli et al. 1998! 0.86 20
0.86 60 17
0.86 100
Sand 0.69 20
0.69 60 0
0.69 100
Sand17% cement 0.68 20
0.72 60 170
0.70 100
Sand17% cement10.5% fiber 0.71 20
0.72 60 180
0.72 100
to the soil according to settlement increments. After each settle-
ment increment, the load was measured at some fixed time inter-
vals until the variation ceased.
Test Results and Analysis
Triaxial Strength and Stiffness
Typical stress-strain curves obtained in the triaxial compression
tests, for the confining pressure of 20 kN/m2, are shown in Fig. 1
for both the sand-cement and the sand-cement-fiber specimens.
The sand-cement specimen showed a marked brittle failure
whereas the sand-cement-fiber specimen demonstrated a some-
what ductile behavior.
Peak and ultimate strength envelopes for both the sand-cement
and the sand-cement-fiber specimens are presented in Fig. 2 along
with the sand ~at a similar relative density! and the residual soil
peak envelopes. The respective strength parameters are presented
in Table 1. The data show that the peak friction angle increased
from 37 to 52 or 43°, respectively, by adding cement only or
cement and fiber to the sand. The cohesion intercept increased
from 0 to 170 kN/m2 due to cement addition and to 180 kN/m2 by
adding cement and fiber. About the ultimate strength envelopes
and parameters, which were determined for an axial strain of
Peak friction
angle ~degrees!
Ultimate cohesion
intercept ~kN/m2!
Ultimate friction
angle ~degrees!
Secant Young’s
modulus for
«a50.1% ~MN/m2!
49
26 10 29 21
14
38
37 0 36 68
132
1007
52 59 34 1297
1600
704
43 76 47 731
613
Plate Load-Settlement Response and Failure
4~a!. Such pattern is corroborated by the load-settlement curves
presented in Fig. 3, where the bearing capacity of the plate on the
e!
failu
!
an
NIC
Mechanism
Fig. 3 and Table 2 show, respectively, the load-settlement curves
and the summary of the three plate load tests carried out. The
Table 2. Summary of Plate LoadTest Results ~300 mm Circular Plat
Treated soil layer
Thickness
~mm!
Curing
period
~days!
Load at
~kN
None—plate directly on the residual soil
~Consoli et al. 1998!
None None Larger th
Sand17% cement layer 300 28 98
Sand17% cement10.5% fiber 300 28 91
JOURNAL OF GEOTECH
sand-cement layer approaches the value obtained for the plate
placed directly on the residual soil. The abrupt decrease in the
bearing capacity of the plate on the sand-cement layer, after
reaching the maximum load, is attributed to the loss of strength
observed in some regions of the sand-cement layer, in which peak
strength is reached at small strains, overstressing nearby regions
and leading to the formation of continuous gaps.
re Settlement
at failure ~mm! Failure mode
40 Larger than 50 Punching
8 Tension fissures initiating on the bottom
of the sand-cement layer followed by punching
22 Formation of a shear band around the plate border,
transferring a higher load to a larger area of the
residual soil underlying the fiber reinforced layer
AL AND GEOENVIRONMENTAL ENGINEERING / JANUARY 2003 / 99
largely damaged during compression for a confining stress of less
than 60 kN/m2. Bonding damage was also observed by Thome´
~1999! in isotropic compression tests carried out on the same
residual soil studied herein. The author reported a large volume
change occurring for the isotropic pressure of 50 kPa. To further
explain the reduction in stiffness with increasing confining
stresses, Consoli et al. ~1998! carried out triaxial tests on two
specimens sheared to different confining stresses. The first speci-
men was isotropically compressed to 20 kPa, which is around the
field mean effective stress. The second specimen was isotropi-
cally compressed up to 100 kPa ~five times the field mean effec-
tive stress! and then unloaded to 20 kPa. After shearing both
specimens, the experimental evidence arising from the compari-
son of the tests is that the application of isotropic pressures higher
than the field mean effective stress produced substantial damage
to the bonded structure with considerable reduction in the initial
soil stiffness during shear. It is important to point out that such
results on bonded specimens contrast to the ordinary patterns pro-
duced by overconsolidation, in which soil stiffness is expected to
increase with increasing overconsolidation stress. Additional in-
formation on the structure damage of the studied residual soil can
be found in previous work by Consoli et al. ~1998!.
Fig. 3. Plate load test ~300 mm diameter! response directly on
residual soil and on top of both sand-cement layer and sand-cement-
fiber layer
benefit of using a sand-cement top layer over a residual soil stra-
tum with low bearing capacity is clearly observed in Fig. 3. It is
shown, for a displacement of about 8 mm, that the bearing capac-
ity of the plate on the sand-cement layer was 98 kN, around five
times the value obtained for the same plate on the residual soil
only ~20 kN!. However, at larger settlements there was a strong
reduction in the bearing capacity of the plate on the sand-cement
layer. The mechanisms of failure for both plate tests are schemati-
cally represented in Figs. 4~a and b!, respectively, and were ob-
served in the field through vertical boreholes excavated just below
the plates. In Fig. 4~a!, tension cracks spreading from bottom to
top of the sand-cement layer are noticed. At large displacements,
however, the load transfer at the interface between the improved
top layer and the residual soil stratum seems to be restricted to the
area of the plate only, as indicated by the large gaps shown in Fig.
Fig. 4. Failure mode for both ~a! sand-cement layer and ~b! sand-
cement-fiber layer
For the plate bearing on the sand-cement-fiber top layer, the son between the two plate load tests carried out, it is reasonable to
GIN
maximum bearing capacity is about 91 kN ~similar to the value
obtained for the sand-cement layer!, at a displacement of about 20
mm ~Fig. 3!, which is twice as much the displacement at failure
for the sand-cement layer.
The failure mechanism observed through a vertical borehole
excavated just below the plate on the sand-cement-fiber layer is
depicted in Fig. 4~b!. In this case, there is no tension crack for-
mation as the fiber seems to inhibit fissure propagation and allow
the distribution of stresses in a broader area, acting similarly to
plant roots and leading to the formation, at failure, of a thick
shear band all around the border of the plate. The load is trans-
ferred over a larger area at the interface between the sand-cement-
fiber layer and the residual soil stratum. As a result, postpeak
bearing capacity is considerably improved when compared to the
values obtained for the plates bearing on either the sand-cement
top layer or directly on the residual soil stratum.
Bearing Capacity Analysis
As seen previously, the overall response of shallow foundations
placed on weak residual soil can be significantly improved by
building a top layer of compacted fiber reinforced cemented soil.
In that case, an analytical solution for layered cohesive-frictional
soils, such as the methods proposed by Ve´sic ~1975! and Meyer-
hof and Hanna ~1978!, which consider punching failure along
straight lines following the foundation perimeter, might be effec-
tively employed to predict the system ultimate bearing capacity.
In the present study, the solutions proposed by Ve´sic ~1975! and
Meyerhof and Hanna ~1978! for layered soils with the stronger
layer on the top, considering reduced shear strength parameters
for the weak residual soil ~lower layer!, as suggested by Consoli
et al. ~1998! after Terzaghi’s recommendations for punching fail-
ure, unsatisfactorily estimated the ultimate loads for the 300-mm-
diam circular steel plate bearing on both the sand-cement and the
sand-cement-fiber top layers. For the plate bearing on the sand-
cement layer, the ultimate load capacity predicted by Ve´sic
~1975! and Meyerhof and Hanna ~1978! were 151.6 and 52.2 kN
~against 98 kN measured in the plate load test!, with predicted/
measured ratios of 1.55 and 0.53, respectively. So, in the case of
a cemented top layer, Ve´sic’s solution overestimated it around
55% the actual bearing capacity, while Meyerhof and Hanna’s
solution underestimated it by about 47%. For the plate placed on
the sand-cement-fiber top layer, the predicted ultimate load ca-
pacities were 177.8 and 51.4 kN, respectively ~against 91 kN
measured in the plate load test!. Once again, the Ve´sic ~1975! and
Meyerhof and Hanna ~1978! analytical solutions presented a poor
estimation of the field results, showing predicted/measured ratios
of 1.95 and 0.57, respectively. Therefore, in the case of a fiber-
reinforced cemented top layer, Ve´sic’s solution overestimated in
about 95% the actual bearing capacity, while Meyerhof and Han-
na’s underestimated it in about 45%.
Advantages of Using Soil Layers Improved
with Cement and Fiber
From the results reported in the foregoing sections, it can be
stated that even though the sand-cement layer conducts to a
higher bearing capacity, when compared to the sand-cement-fiber
layer, the latter, in terms of postpeak behavior, leads to a more
reliable solution and possibly to a reduction in the design safety
factor, since the fiber inclusion reduced dramatically the brittle
response of the soil-foundation system. Also, from the compari-
100 / JOURNAL OF GEOTECHNICAL AND GEOENVIRONMENTAL EN
presume that, by using a sand-cement-fiber treated top layer,
settlements might be drastically reduced and bearing capacity in-
creased from 3 to 10 times, depending on the settlement allow-
ance ~restricting maximum settlements to 25 mm!. Finally, it is
worthwhile to compare the improved top layer solution studied
with the conventional pile foundation design. Ramires ~1993!tested small diameter bored piles ~0.2 m diameter, 3 m length! on
the same experimental site described in the present work, finding
an ultimate load of 28 kN ~considering a maximum displacement
of 25 mm!, being 10 kN point resistance and 6 kN/m shaft resis-
tance. To reach the ultimate load found for the layered system
comprising a cement-sand-fiber top layer overlaying a weak re-
sidual soil stratum, which was around 91 kN, it would be neces-
sary to execute on the residual soil stratum, considered homoge-
neous in depth, at least two 0.2-m-diam bored piles with 6 m of
length or three with 3.5 m, plus the reinforced concrete pile cap.
Therefore, the alternative solution proposed herein, besides being
technically feasible for light to moderate foundation loads, might
also be economically competitive if compared to the conventional
deep foundation design or the shallow foundation bearing directly
on the weak residual soil, depending mainly on the local labor
cost, which varies from country to country. However, there will
be some cases where the construction of embankments previous
to the foundations, to reach a specified ground level, is necessary.
In such cases, the use of cement and fiber to improve the top layer
of the embankment, on the top of which a shallow foundation is
built, is probably the best solution, technically and economically,
for light to moderate loads.
Summary and Conclusions
The following observations and conclusions are made regarding
the results of three plate loading tests ~300 mm diameter, 25.4
mm thick! carried out directly on a residual homogeneous soil
stratum, as well as on a layered system formed by two different
top layers ~300 mm thick!—sand-cement and sand-cement-
fiber—overlaying a residual soil stratum.
1. The utilization of a layered system made up of a top sand-
cement layer overlaying a residual soil stratum has proved to
markedly increase the bearing capacity obtained from a plate
loading test, reducing displacement at failure and changing
soil behavior into a noticeable brittle behavior. After failure,
the bearing capacity is reduced towards the value obtained
for the plate placed directly on the residual soil stratum. The
failure mechanism of the sand-cement layer is triggered by
the formation of tension cracks from the bottom to the top of
the layer, especially under the border of the plate, resulting
in a subsequent punching of the layered system and the re-
sidual soil stratum. Ve´sic ~1975! and Meyerhof and Hanna
~1978! bearing capacity solutions for layered soils with the
firm layer on the top of a weak layer, respectively, overesti-
mated ~more than 55%! and underestimated ~around 45%!
the field results obtained in the present work, considering
both the sand-cement and the sand-cement-fiber top layers
overlaying a weak soil stratum, evidencing that a specific
bearing capacity method has still to be developed for shallow
foundations placed on cemented and fiber-reinforced ce-
mented top layers overlaying a weak soil stratum.
2. The addition of polypropylene fiber to the cemented top
layer kept the maximum bearing capacity virtually un-
changed but increased displacement at maximum load and
improved the ultimate bearing capacity, when compared to
EERING / JANUARY 2003
the plate on the sand-cement top layer. The fiber reinforce-
ment significantly changed the failure mechanism by pre-
venting the formation of tension cracks, as observed for the
sand-cement layer. Instead, the formation of a thick shear
band all around the plate was observed, allowing the load to
spread through a larger area at the interface between the
sand-cement-fiber layer and the residual soil stratum.
Acknowledgments
The writers wish to express their gratitude to CNPq-National
Council of Scientific and Technological Research ~Project Nos.
520610/95-4 and 479804/01-0!, as well as to BRITISH COUN-
CIL and CAPES—Coordination of Training of High Education
Graduate ~Project No. CAPES-BRITISH COUNCIL 088/99! and
FAPERGS—Rio Grande do Sul State Research Foundation
~Project No. 99/1111.0! for the financial support to the research
group.
Notation
Clayton, C. R. I., Khatrush, S. A., Bica, A. V. D., and Siddique, A. ~1989!.
‘‘The use of Hall effect semiconductor in geotechnical instrumenta-
tion.’’ Geotech. Test. J., 12, 69–76.
Consoli, N. C., Schnaid, F., and Milititsky, J. ~1998!. ‘‘Interpretation of
plate load tests on residual soil site.’’ J. Geotech. Geoenviron. Eng.,
124~9!, 857–867.
Consoli, N. C., Schnaid, F., Milititsky, J., and Vendruscolo, M. A. ~1997!.
‘‘Design of shallow foundations on structured and compacted soils
based on plate loading tests and finite element analysis.’’ Proc., 14th
Int. Conf. on Soil Mechanics and Foundation Engineering, Hamburg,
Germany, 783–784.
La Rochelle, P., Leroueil, S., Trak, B., Blais-Leroux, L., and Tavenas, F.
~1988!. ‘‘Observational approach to membrane and area corrections in
triaxial tests.’’ Proc., Symp. on Advanced Triaxial Testing of Soil and
Rock, ASTM, Louisville, Ky., 715–731.
Maswoswe, J. J. ~1985!. ‘‘Stress path method for a compacted soil during
collapse due to wetting.’’ PhD thesis, Univ. of London.
Meyerhof, G. G., and Hanna, A. M. ~1978!. ‘‘Ultimate bearing capacity
of foundations on layered soils under inclined load.’’ Can. Geotech.
J., 15, 565–572.
NBR-12131. ~1991!. ‘‘Foundations—Static loading tests.’’ Brazilian
Standards.
Ramires, M. C. P. ~1993!. ‘‘Study of the behavior of small diameter bored
piles in a homogeneous residual soil layer.’’ MSc dissertation, Federal
Univ. of Rio Grande do Sul, Porto Alegre, Brazil ~in Portuguese!.
NICA
The following symbols are used in this paper:
B 5 pore pressure parameter;
Ln 5 average dial gauge reading at specified time in-
terval t;
Ln21 5 immediately previous average dial gauge reading
to Ln ;
L1 5 first dial gauge reading of the stage of loading;
and
s1 , s3 5 principal stresses.
References
ASTM D1194-94. ~Reapproved 1998!. ‘‘Standard test method for bearing
capacity of soil for static load and spread footings.’’ American Society
for Testing and Materials, Philadelphia.
Clayton, C. R. I., and Khatrush, S. A. ~1986!. ‘‘A new device for mea-
suring local axial strain on triaxial specimens.’’ Geotechnique, 25,
657–670.
JOURNAL OF GEOTECH
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