ASSESSMENT OF GEOTECHNICAL PARAMETERS FOR SOILS OS SAO PAULO BASIN BY OF IN SITU TEST

Prévia do material em texto

Assessment of Geotechnical Parameters for Soils of Sao Paulo 
Basin by means of in-situ tests 
 
Mariana Kozlowski Caldo 
Escola Politécnica da USP, São Paulo, Brasil, marianakozc@hotmail.com 
 
Faiçal Massad 
Escola Politécnica da USP, São Paulo, Brasil, faical.massad@poli.usp.br 
 
Hugo Cássio Rocha 
Companhia do Metropolitano de São Paulo, São Paulo, Brasil, hcrocha@metrosp.com.br 
 
ABSTRACT: A detailed geological and geotechnical investigation was carried out during the basic 
design of the Green Line expansion for the Metrô – SP, Brazil. This subway extension will connect 
Vila Prudente Station to the future Dutra Station, on the eastern Sao Paulo city. This paper presents 
results of dilatometer tests (DMT) in variegated soils from Sao Paulo’s Sedimentary Basin, which 
was formed during the Paleogene Period. Soil parameters, such as earth pressure coefficients at rest 
(K0), over consolidation ratio (OCR), preconsolidation pressure ( ’p), undrained shear strength (su) 
and initial tangent module (Ei) obtained from DMT data are presented. Comparisons of the results 
with a previous study for a clay of the Resende Formation were made. The definition of these 
parameters by means of in-situ testing provides an improvement on knowledge regarding soil 
properties. It represents an important tool for future projects, decreasing geological and geotechnical 
uncertainties, thus enhancing the geotechnical work reliability and reducing its risks. 
 
KEYWORDS: Site investigation, Dilatometer Test, Soil properties. 
 
 
1 INTRODUCTION 
 
Engineering presents a dilemma between safety 
and economy, especially in geotechnics. 
Therefore, in-situ tests have great importance 
for gathering site information, in order to 
decrease uncertainty with greater safety and 
economy. 
 The tunnel construction for the Companhia 
do Metropolitano de São Paulo (Metrô – SP), 
the subway state company, provided the 
opportunity to execute a comprehensive 
programme of in-situ tests, such as dilatometer 
test (DMT), still not frequently used in Brazil, 
especially in soils from Sao Paulo’s 
Sedimentary Basin. 
 Nevertheless, some examples and data from 
geological and geotechnical investigations 
carried out by Metro are presented in Monteiro 
et al. (2012). 
 Soils from Sao Paulo’s Sedimentary Basin 
comprise mostly the Sao Paulo and Resende 
Formations. While many studies about Resende 
Formation have been made, there is still a lack 
of information about the soils from Sao Paulo’s 
Sedimentary Basin. A comprehensive and 
critical synthesis of knowledge on the soil 
properties of Sao Paulo’s Sedimentary Basin are 
present in Massad (2012). 
 For the expansion of the Green Line, Metrô – 
SP invested in in-situ tests to obtain 
geotechnical parameters of variegated soils 
from the Sao Paulo Formation. 
 Soil parameters, such as earth pressure 
coefficients at rest (K0), over consolidation ratio 
(OCR), preconsolidation pressure ( ’p), 
undrained shear strength (su) and initial tangent 
module (Ei) obtained from DMT data is figured 
out. 
 In order to validate the data obtained from 
this investigation, a comparison is made with 
the results of previous studies for the Sao Paulo 
and the Resende Formations. 
 Therefore, these paper objectives are: 
describing the testing and analysis procedures 
for the DMT in-situ tests, determining the 
mentioned above soil parameters and 
comparing and discussing the results with 
others laboratory and in-situ tests. 
 
 
2 SITE DESCRIPTION 
 
Soils from Sao Paulo’s Sedimentary Basin, 
which was formed by the Brazilian Southeast 
Continental Rift during the Paleogene Period, 
comprise mostly the Resende and Sao Paulo 
Formations. The former is characterized by 
distinct packs of sand (known as basal sands) 
and stiff overconsolidated clays (locally known 
as “taguá”) and the latter is characterized by 
porous clays and layers of variegated soils. 
 Resende Formation is widely distributed in 
the basin, with layers achieving more than 250 
meters of depth. Sediments consisting of 
diamictite, sand and clay were deposited by 
alluvial fan deltas, associated to braided rivers. 
The “taguá” clays belong to this formation, 
showing a fraction of fines greater than 60 %, 
activity index values in the range of 0.6 to 1.1 
and a hard consistency; moreover, they are 
strongly overconsolidated due to a still 
uncertain reason. 
 Sao Paulo Formation is distributed in 
elevations usually between 735 and 740 meters. 
Its depositional environments are associated 
with fluvial meanders. According to Massad 
(2012), the variegated soils are highly 
weathered sediments deposited in alternating 
layers of sand and clay, very heterogeneous. 
Their engineering properties vary widely due to 
the occurrence of very different types of soils, 
such as sands, clayey fine sands and sandy clays 
with silts. It seems that there is one universe 
with the sand fraction ranging from 10 to 90 %. 
The activity index is approximately 0.65. In 
general, these soils are overconsolidated, but the 
preconsolidation pressure is not correlated with 
the weight of current or past eroded overburden. 
One can speculate that successive sedimentation 
cycles, associated with the drying of the soil, 
has affected the preconsolidation pressures 
through capillary tensions, which are greater are 
the finer the soil particles, or that there was a 
chemical cementation of the soil particles, a 
result of pedological evolution. 
 
 
3 DMT TESTS OF SOILS FROM SAO 
PAULO FORMATION 
 
The dilatometer test was primarily developed to 
investigate the values of soil modulus for 
laterally loaded driven piles, where horizontal 
movements are also preceded by penetration 
(Marchetti, 1975). 
 This test is regularized by the international 
standard such as “Standard Test Method for 
Performing the Flat Plate Dilatometer Test” – D 
6635-01 (ASTM, 1986) and Eurocode 7 – 
Geotechnical Design – Part 3 – “Design 
Assisted by Field Testing – Section 9 – Flat 
Dilatometer Test (DMT)” (Eurocode 7, 1997). 
 The dilatometer consists of a steel blade with 
a flexible membrane for a lateral expansion 
under gas pressure. Three expansion phases are 
registered by control unit, A, B and C pressures: 
• A pressure – the gage gas pressure against 
the inside of the membrane when the center of 
the membrane has lifted above its support and 
moved laterally 0.05 mm into the soil 
surrounding the blade; 
• B pressure – the gage gas pressure against 
the inside of the membrane when the center of 
the membrane has lifted above its support and 
moved laterally 1.10 mm into the soil 
surrounding the blade; and 
• C pressure – the gage gas pressure against 
the inside of the membrane when the center of 
the membrane returns to the A pressure position 
during a controlled, gradual deflation following 
the B pressure. 
 Imprecision, mainly caused by steel blade 
rigidity, must be corrected, originating the 
pressures p0, p1 e p2. Data is processed by a 
computer program and the following index 
parameters are obtained: 
 
ID = (p1-p0)/(p0-u0) (1) 
 
ED = 34.7(p1-p0) (2) 
 
KD = (p0-u0)/σ’vo (3) 
 
 where ID is the material Index; ED is 
Dilatometer modulus; KD is the Horizontal 
stress index; u0 is the in-situ porepressure and 
σ’vo is the in-situ vertical effective stress. 
 The DMT tests were executed in three 
different locations, sites 5221, 5249 e 5252. The 
Figure 1 shows the locations in a geologic map. 
 
Figure 1.Location of DMT tests. 
 
The Figure 2 shows a typical result of DMT 
tests. 
 
0,00
5,00
10,00
15,00
20,00
0 500
PR
O
FU
N
D
ID
A
D
E 
(m
) 
su (kPa)
0,00
5,00
10,00
15,00
20,00
0 10 20 30
PR
O
FU
N
D
ID
A
D
E 
(m
) 
OCR
0,00
5,00
10,00
15,00
20,00
0 2 4 6
PR
O
FU
N
D
ID
A
D
E 
(m
) 
K0
0
5
10
15
20
D
ep
th
 (m
) 
DMT 5221
W.L. = 4,28
Slightly sandy silty 
clay, stiff to hard, 
variegated
Slightly silty sandy 
clay, medium to hard, 
variegated
Fine to coarse sand with 
gravel, medium to dense, 
red
Slightly sandy silty clay, 
stiff to hard, variegated
Slightly silty sandy clay, medium 
to hard, variegated
Fine to medium sand, medium 
to dense, yellow and red
 
Figure 2. Parameters (K0, OCR and su) in function of 
depth, resultant from 5221 - DMT test. 
 
 
4 INTERPRETATION OF THE RESULTS 
 
From the DMT tests, geotechnical parameters 
were obtained through empirical equations 
proposed by some researchers and 
recommended by ASTM International 
Technical Standard (ASTM, 1986). 
Schmertmann (1988) found out that these 
correlations generally provide reasonable 
accuracy, except in very sensitive clays, 
weathered clay crusts and aged/cemented clays, 
as in the present case. 
 To obtain the values of K0 in variegated soils 
(ancient deposits) it was used the equation 
proposed by Lunne et al. (1990): 
 
K0 = 0.68KD
0.54
 (4) 
 
 For OCR values, it was used the equation of 
Kamei and Iwasaki (1995): 
 
OCR = 0.34KD
1.43
 (5) 
 
And to obtain su, it was used the equation of 
Marchetti (1980): 
 
su = 0.22σ’vo(0.5.KD)
1.25
 (6) 
 
 In order, to correlate K0 and OCR, the Figure 
3 was prepared with data interpreted from DMT 
tests. The K0 value varies from 0.6 to 3.5 and 
OCR from 1 up to 30. 
 To validate the equations used, Figure 3 
shows a point with a Camkometer test made in 
the same clay in another site, which was 
presented by Pinto and Abramento (1998). The 
proximity between the point and the curve 
denotes that these correlations are valid. 
 
0,0
0,5
1,0
1,5
2,0
2,5
3,0
3,5
4,0
0 10 20 30 40 50
K
0
OCR 
DMT 5221
DMT 5249
DMT 5252
Camkometer
 
Figure 3. Correlations between K0 and OCR. 
 
 Figure 4 shows a plot of su as a function of 
’p for the variegated soils. The values of the 
preconsolidation pressure ( ’p) were determined 
using the calculated values of OCR. 
 To estimate σ’vo, the natural density was 
determined based on DMT parameters ED and 
ID, resulting values in the interval 14.0 to 
20.6 kN/m
3
, close to the laboratory range of 
15.5 to 21.4 kN/m
3
. As observed in Figure 4, 
the ratio su/ ’p varies in the range 0.125 to 
0.150. 
 In order to validate this result, Figure 4 
includes data from Massad (1980) which shows 
the ratio su/ ’p = 0.1 for the variegated soils, 
obtained from triaxial tests also presents in 
Massad (2012). The smaller value may be 
attributed to some inevitable laboratory 
disturbance in the soil samples. 
 
0
50
100
150
200
250
300
350
400
0 500 1000 1500 2000
s u
(k
Pa
)
'p (kPa)
DMT 5221
DMT 5249
DMT 5252
CU Triaxial Tests 
(10%)
su=0.10. ´p
su=0.125. ´p
su=0.15. ´p
 
Figure 4. Correlations between su and OCR. 
 
 The Figure 5 presents the correlation 
between Ei and su. The initial tangent modulus 
(Ei) was estimated based on DMT data and 
using the equation: 
 
Ei = F.ED (7) 
 
where ED is the dilatometer modulus and F is an 
empirical coefficient. According to Robertson et 
al. (1989), F = 10 for cohesive soils, and F = 2 
for sands; for silty soils a mean value (F = 6) 
was taken. 
 The correlation obtained for the variegated 
soils is Ei = 0.727su + 35.26 which is similar to 
the one obtained by Massad (2012) for the 
“taguá”, plotted with dotted line. The values 
from “taguá” are greater due to its higher over 
consolidation ratios (OCR) and age. 
 
0
100
200
300
400
500
600
700
800
900
0 200 400 600 800 1000
E i
(M
Pa
)
su (kPa)
DMT tests
Camkometer & 
DMT 1 - Taguá
Ei = 0.96su + 72 
Ei = 0.727su + 35.26 
 
Figure 5. Correlations between Ei and su. 
 
 Figure 6 compares the values for Ei and ’p 
obtained from DMT tests, which resulted in the 
correlation Ei = 0.077 ’p + 56.56. 
 To validate it, results of Camkometer tests in 
“taguá” were plotted in dotted lines in the 
graphic, showing the same trend of variation but 
with higher values than the variegated soil due 
to the same reason mentioned above, related to 
Figure 5. 
 
0
200
400
600
800
1000
1200
0 2000 4000 6000 8000 10000
E i
(M
P
a)
'p (kPa)
DMT tests
Camkometer & 
DMT 1 - Taguá
Ei = 0.077. 'p+56.56
Ei = 0.102. 'p+83
 
Figure 6. Correlations between Ei and ’p. 
 
 
5 CONCLUSIONS 
 
Based in the DMT data, it was found out that 
for the variegated soils the K0 is well correlated 
with the OCR; the values of K0 (0.6 to 3.5) and 
OCR (1 to 30) are consistent with previous 
knowledge: such these soils are, in general, 
erratically overconsolidated due to phenomenas 
as drying under successive sedimentation cycles 
and chemical cementation of soil particles, a 
result of its pedological evolution. These 
assumptions, added to the aging process of 
these soils, were determi-nant in the choice of 
the analysis procedure for the DMT data. 
 Moreover, the following useful correlations 
were determined: 
 
su = 0.125 to 0.15 ’p (8) 
 
Ei = 0,727su + 35.26 (9) 
 
Ei = 0.077 ’p + 56.56 (10) 
 
 Finally, comparisons were made with: 
 a) laboratory data on undisturbed samples of 
the variegated soils, revealing comparable 
results; and 
 b) in-situ DMT and the Camkometer tests on 
the “taguá” clay, showing the same trends of 
variation, but with greater values for the latter, 
due to its higher OCR and age. 
 
 
ACKNOWLEDGMENTS 
 
The in-situ testing programme was sponsored 
by the Companhia do Metro-politano de São 
Paulo (Metrô – SP) and Bureau de Projetos e 
Consultoria Ltda. The study was carried out at 
Escola Politécnica of Sao Paulo University, 
within the Civil Engineering Postgraduate 
Program. 
 
 
REFERENCES 
 
Monteiro, M. D., Gurgueira, D. D., Rocha, H. C. (2012). 
Geologia da Região Metropolitana de São Paulo. In: 
TWIN CITIES – Solos de São Paulo e Curitiba, 2012, 
v.1, p. 15-44. 
Massad, F. (2012). Resistência ao Cisalhamento e 
Deformabilidade de Solos Sedimentares. In: TWIN 
CITIES – Solos de São Paulo e Curitiba, 2012, v.1, p. 
107-133. 
Marchetti, S. (1975). A new in-situ test for the 
measurements of horizontal soil deformability. 
Proceedings of the ASCE Spec. Conf. on In-situ 
Measurement of Soil Properties, v. 2, p. 255-259, 
1975. 
ASTM Subcommitte D 18.02.10 – Schmertmann, J.H., 
Chairman, (1986). “Suggested Method for Performing 
the Flat Dilatometer Test”. ASTM Geotechnical 
Testing Journal, Vol.9, nº2, June, 93-101. 
Eurocode 7 (1997). Geotechnical design – Part 3: Design 
assisted by field testing, Section 9: Flat dilatometer 
test (DMT). Final Draft, ENV 1997-3, Apr., 66-73. 
CEN – European Committee for Standardization. 
Schmertmann, John H. (1988). “Guidelines for Using the 
CPT, CPTU and Marchetti DMT for Geotechnical 
Design,” U.S. Dept. of Transportation, Federal 
Highway Administration,Report No. FHWA-PA-
024+84-24, Vol 3. 
Lunne, T.; Powell, J.J.M.; Hauge, E; Uglow, I.M.; 
Mokkelbost, K.H. (1990). Correlations of 
Dilatometer readings with lateral stress in clays. NGI 
Publ., Oslo, p. 183-193. 
Kamei, T. and Iwasaki, K. (1995). Evaluation of 
undrained shear strength of cohesive soils using a Flat 
Dilatometer. Soils and Foundations, Vol. 35, No. 2, 
June, 111-116. 
Marchetti, S. (1980). In Situ Tests by Flat Dilatometer. 
Journal Geotechnical Engineering, ASCE, Vol. 106: 
299-321. 
Pinto, C. S. and Abramento, M. (1998). Características 
das argilas rijas e duras, cinza-esverdeadas de S. 
Paulo determinadas por pressiômetrro de auto-furação 
Camkometer. In: Congresso Brasileiro de Mecânica 
dos Solos e Engenharia Geotécnica 11, vol 2: 871-
878. 
Massad, F. (1980). Características e propriedades 
geotécnicas de alguns solos do Terciário da Cidade de 
São Paulo. Mesa Redonda Aspectos Geológicos e 
Geotécnicos da Bacia Sedimentar de São Paulo. 
Publicação Especial da ABGE e SBG, S. Paulo, 
Anais, p.53 e s.. 
Robertson, P. K.; Davies, M. P.; Campanella, R.G & Sy. 
A. (1989). An Evaluation of Pile Design in Fraser 
River Delta Using In Situ Tests. Foundations 
Engineering Current Principles and Practices, ASCE, 
Evanston, IL, p. 92-105.