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Correlation between PMT and SPT results for calcareous soil
HBRC Journal (2016) xxx, xxx–xxx
Housing and Building National Research Center
HBRC Journal http://ees.elsevier.com/hbrcj
FULL LENGTH ARTICLE
Correlation between PMT and SPT results for calcareous soil Mona B. Anwar * Associate Professor, Civil Engineering Department, The German University in Cairo, Egypt Associate Professor (on leave), Civil Engineering Department, Faculty of Engineering, Helwan University, Cairo, Egypt Received 26 October 2015; revised 12 February 2016; accepted 1 March 2016
KEYWORDS Pressuremeter; SPT; Calcareous; Elastic modulus
Abstract The simplicity and low cost of the standard penetration test (SPT) have always been the major advantages of this test over other field tests. Despite that other field tests (e.g. PMT, CPT, DMT, . . .) are supposed to provide more reliable results, yet they are still costly and not feasible in every project. Considering that SPT is available in all site investigation programs for all sizes of project, it was tempting to provide correlations between SPT results and other field test results. Through these correlations it will be feasible to estimate the soil parameters and deformation properties from the SPT number of blows. However, it is believed that correlations will differ, if the tested soil is calcareous. Furthermore, adopting local correlations is more favorable as it caters for the geological formation of the site. In this research it is aimed to obtain correlation between the PMT results and the SPT results for calcareous soil. A site investigation comprising boreholes with SPT and PMT was carried out near to the Red sea coast in Jeddah. The study was carried out to develop a local correlation between the results of SPT and PMT considering the effects of soil gradation and carbonate content. Comparison between the obtained correlation and other available correlations is also considered. Ó 2016 Housing and Building National Research Center. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Introduction
* Address: Civil Engineering Department, The German University in Cairo, Egypt. E-mail address: [email protected]. Peer review under responsibility of Housing and Building National Research Center.
Production and hosting by Elsevier
Pressuremeter test (PMT) was developed by Menard, in 1955 to measure the in situ soil deformation properties, Briaud [1]. The pressuremeter consists mainly of a long cylindrical probe that is expanded radially into the surrounding ground. By tracking the amount of volume of fluid and pressure used in inflating the probe, the data can be interpreted to give a complete stress–strain–strength curve. The insertion of the pressuremeter in ground depends on its type, either self-boring or pre-boring. PMT is considered theoretically sound in determining soil parameters and can test larger zone of soil mass than other in situ tests. Yet, PMT requires high level of skill
http://dx.doi.org/10.1016/j.hbrcj.2016.03.001 1687-4048 Ó 2016 Housing and Building National Research Center. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
2
M.B. Anwar
and can easily be damaged, and above all it is relatively expensive, Mayne et al. [2]. Actually this test is not carried out in conventional geotechnical site investigation for typical projects, Charif and ShadiNajjar [3]. On the other hand, there is the Standard Penetration Test (SPT), which is performed during the advance of the boreholes and is already carried out in all site investigation programs in nearly all boreholes due to its simplicity and low cost. Due to the availability of the SPT in every site investigation program, it was tempting to obtain correlations between SPT results (number of blows) and soil properties, namely shear strength parameters and soil deformation characteristic presented by the elastic modulus. Furthermore, correlations were also obtained to relate the results of the SPT to the results of other field tests (e.g. CPT, PMT, DMT). Nevertheless, despite the many available correlations between the SPT and the CPT, there are still limited number of correlations between the SPT and the PMT. The PMT provides a direct measurement of the horizontal modulus of soil. This modulus (EPMT) often is presumed to be roughly equivalent to the Young’s modulus (E), Phoon and Kulhawy [4]. Furthermore, both EH and EV are involved in the response of the vertical loading. Several investigations found that it was at most 5% difference between EH and EV, Briaud [1]. Nevertheless, soil elastic modulus is the most difficult parameter to obtain as it depends on many factors such as stress level, strain level, soil density and stress history, Briaud [5] and Charif and ShadiNajjar [3]. Attempts have been made to correlate the EPMT with the NSPT. Ohya et al. [6] proposed correlations for both clay soil and cohesionless soil in Japan, Fig. 1. The correlations are well known, yet they are fairly weak, Phoon and Kulhawy [4]. Briaud et al. [7] presented a database of preboring pressuremeter test data and other field tests data (i.e. CPT and SPT). The sites were located in USA, 36 of them were sand formation sites and 44 were clay formation sites. Best fit regressions were performed for the entire database. Eq. (1) presents the correlation proposed for the EPMT with NSPT in sand. However, the scatter in the correlations was found very large. This drastic scatter made these correlations useless in design, Briaud [1], Fig. 2a. blows blows Eo ðkPaÞ ¼ 383N ; Eo ðtsfÞ ¼ 4N ð1Þ 30 cm ft In 2008, Yagiz et al. [8] proposed correlations between NSPT and EPMT results for sandy silty clayey soil based on 15 boreholes in Turkey. The borehole depths were 5–8 m, and the tests were carried out at depth 1.5–2 m only. Regression analysis was undertaken and best fit regression between the parameters in a linear combination with 95% confidence level. The correlation is presented by Eq. (2). Fig. 2b presents the correlation, based on only 15 results. Em ¼ 388 Ncor þ 4554
ð2Þ
In 2010, Bozbey and Togrol [9], proposed a correlation based on case study of 182 tests in Turkey as given in Eqs. (3.a) and (3.b): For Sandy soil : EPMT ðMPaÞ ¼ 1:33ðN60 Þ0:77
ðr2 ¼ 0:82Þ ð3:aÞ
For Clayey soil : EPMT ðMPaÞ ¼ 1:61ðN60 Þ
0:71
ðr ¼ 0:72Þ 2
ð3:bÞ
Another correlation was given by Kenmogne et al. [10] based on site investigation data in Cameroon. The correlation was linear and is given in Eq. (4). Em ¼ b N
ð4Þ
where b = 2–8 for gravely sand. =2–20 for clayey sand. Cheshomi and Ghodrati [11] presented correlations for silty sand and silty clay soil based on case study in Iran (38 tests for silty clay soil and 16 tests for silty sand soil) given by Eqs. (5.a) and (5.b). These correlations are valid only for the range of NSPT measured in site (i.e. 9–50 number of blows). For silty sand : EPMT =Pa ¼ 9:8N60 94:3 ðr ¼ 0:79Þ
ð5:aÞ
For silty clay : EPMT =Pa ¼ 10N60 26:7 ðr ¼ 0:85Þ
ð5:bÞ
As presented above, the available correlations between the EPMT and the NSPT are either highly scattered (i.e. small correlation factor) or based on limited number of results. Yet they are representing local correlations that are developed within specific geologic setting. Reference to Phoon and Kulhawy [4] local correlations is preferable to generalized global correlations, but they need to be accurate, which leads to the need of more studies and data to develop these correlations into more mature state. However, all cases using empirical correlations should be with caution as it is linking two items together that are not directly related, Kulhawy [12]. Another factor needs to be considered when adopting those correlations. This factor is that these correlations are based on tests carried out in siliceous soil. Many references such as SPT, ElKateb and Ali [13], Kulhawy and Mayne [14], Ahmed et al. [15], Vafeian et al. [16], Schneider and Lehane [17] are discussing the difference in behavior between calcareous or carbonate soil and siliceous soil under field tests especially destructive tests. It is very likely that destructive testing as SPT can possibly break cementation of calcareous sand and may crush the actual sand particles resulting in change in the physical properties of the soil matrix, Charif and ShadiNajjar [3], which implies the need for specific correlations for this type of soil. The aim of this research was to provide correlation between the PMT and SPT results to be able to obtain the soil moduli taking into consideration the soil gradation and its calcareous nature. Site characterization The soil under study is located in Jeddah area, relatively near to the Red Sea coast. The soil formation comprised of interbedded layers of silty/clayey sand with silty/clayey gravel and sandy gravel, which is known as Wadi deposits. Cementation was observed at some depths. Such layers continued from ground surface down to 20 m depth. The in-situ compactness of these layers was found generally to be medium dense to very dense. Layers of the cohesive soil were encountered at shallow depths of 1.5 m in some boreholes and as deep as 18 m in others. The thickness of the sandy lean clay layer ranged from 1.5 to 3 m or more. The carried out site investigation comprised of many boreholes with depths ranging from 20 to 50 m. PMT was carried out in 17 BHs and SPT was also carried out at depth interval of 1.5 m. Groundwater was
Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
Correlation between PMT and SPT results
Fig. 1
3
Relationship between EPMT and NSPT value. Source: Ohya et al. [6].
Fig. 2b Relationship between measured and predicted Em. Source: Yagiz et al. [8].
Fig. 2a Example of correlations in sand from PMT data base. Source: Briaud et al. [7].
encountered at depths ranging from 4 m to 10 m. Laboratory tests (e.g. soil gradation, Atterberge limits, chemical analysis) were carried out to determine the index properties of soil which were used in soil classifications. The soil had carbonate content in the form of CaCo3 in average range of 5–20%, with some samples showing higher carbonate content up to 40%. Reference to modified Clark and Walker system, this soil is termed calcareous soil, Peuchen et al. [18]. Based on the gradation tests, soil showed very wide range of fine contents and gravel contents. Accordingly, to be able to study the correlation between NSPT and EPMT results, soil was divided into three groups based on the D50 values which are reflected on the gravel contents as well. Table 1 and Fig. 3 present the three soil groups. Standard penetration tests were carried out in the boreholes following ASTM D1586 [19]. Tests were carried out at 1.5 m
intervals. Fig. 4a presents the results of NSPT with depth for the 17 BHs. The PMT was also carried out at the same depth interval following the ASTM D4719 [20]. The pressuremeter tests were executed using the Prebored, G type Menard pressuremeter. The excavation for the PMT was carried out in the cleaned bottom of the boreholes to drill hole to fit the BX size probe. Fig. 4b presents the change of the obtained EPMT with depth for the 17 BHs. Results and discussion The relation between the NSPT and the corresponding EPMT at same levels was plotted for the three soil groups presented in Table 1. Regression analysis was carried out to calculate the least squares fit for the given points and the R-squared values were calculated to determine the accuracy of the relation. For soil Group 1, the relation between NSPT and EPMT is presented in Fig. 5. Values of the EPMT were normalized by the atmospheric pressure Pa (101 kPa). It is shown from figure that the scatter is relatively accepted relative to the correlations
Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
4
M.B. Anwar Table 1
Soil groups. D50
Fines content
Gravel content
Max. gravel size
Remarks
Group 1 Group 2 Group 3
<0.25 0.25–1 >1
25–50% 15–30% 0–20%
<25% 20–40% 35–70%
610 mm
Fines are silt or clay with low plasticity
Group 1
Up to 100 mm
referred to either refusal under the SPT spoon due to gravel, or crushing of gravel under the impact which, in both cases, will give misleading SPT results
Group 2
Group3
100
% pass
Soil Group 2 : EPMT =Pa ¼ 38:428ðNSPT Þ0:7385
ðR2 ¼ 0:385Þ ð7Þ
The same trend was observed in soil Group 3 as presented in Fig. 7 and by Eq. (8). The higher increase in gravel contents added to its large diameter (up to 100 mm) weakened the relation more and more which is reflected in the calculated R-squared.
50
0 0.001
0.01
0.1
1
10
100
Diameter (mm)
10000
EPMT / Pa
Fig. 3 Ranges of gradation for the 3 groups of soil used in the current study.
proposed in the literature. The obtained correlation is presented in Eq. (6). Soil Group 1 : EPMT =Pa ¼ 33:92ðNSPT Þ0:803
ðR2 ¼ 0:71Þ
100
ð6Þ The same procedures were carried out for soil Group 2 and the results are presented in Fig. 6 and the correlation is given by Eq. (7). The regression analysis for soil Group 2 showed less accuracy for the obtained correlation as the calculated R-squared was found to be only 0.385. This higher scatter can be referred to the higher gravel content which increases the inconsistency of the SPT results. This inconsistency is
Level (MSL - m)
15
0
100
y = 33.927x0.803 R² = 0.7104
Soil Group 1 10
10
200
300
Fig. 5
15
10
10
5
5
0
0
-5
-5
-10
-10
-15
-15
Fig. 4
100
1000
NSPT (blows/30)
Relation between (EPMT/Pa) and (NSPT) for soil Group 1.
(b)
NSPT
(a)
1000
EPMT - (MPa) 0
100
200
300
400
Field test results.
Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
Correlation between PMT and SPT results
5
10000
Predicted by the proposed correlaon Yagiz et al 2008 Sandy silty clayey soil Bozbey & Togrol 2010 Sandy soil
1500
EPMT/ Pa
1000
EPMT /Pa
1000 100
y = 38.428x 0.7385 R² = 0.3851
500
Soil Group 2 10 10
100
1000
NSPT (blows/30)
0 0
Relation between (EPMT/Pa) and (NSPT) for soil Group 2.
Fig. 6
Fig. 8
10000
50
100
N SPT (blows/30cm) Relation between (NSPT) and the predicted (EPMT/Pa).
are preferred than global ones to cater for the site specific formation. 1000
EPMT/ Pa
Conclusions
100
y = 178.14x0.4398 R² = 0.1205
Soil Group 3 10
10
100
1000
NSPT (blows/30)
Fig. 7
Relation between (EPMT/Pa) and (NSPT) for soil Group 3.
Soil Group 3 : EPMT =Pa ¼ 178:14ðNSPT Þ0:4398
ðR2 ¼ 0:12Þ ð8Þ
Based on the above regression analysis, it can be concluded that the applicability of correlation between the EPMT and NSPT is eliminated by the increase in gravel content and gravel diameter. To compare the correlation of soil Group 1 with those presented in the literature, the predicted values of E, using Eq. (6) for soil Group 1, were plotted versus the measured NSPT and presented in Fig. 8. Correlations cited from Yagiz et al. [8] and Bozbey and Togrol [9] were also used to predict the E values for the measured NSPT and results are presented in Fig. 8. Other correlations from the literature were limited either to small range of NSPT Cheshomi and Ghodrati [11] or having drastic scatter, Briaud [1] and Ohya et al. [6]. It is noticed from the figure that the results from the proposed correlation is higher than those of the literature. The difference can be attributed to the different soil and geologic formation, calcareous nature and cementation in some depths. Accordingly, as stated above local correlations
The proposed correlation, for soil Group 1, is considered as local correlation for this formation in Jeddah and also can be considered applicable for soils having the same gradation and similar geologic formation. The proposed correlation for soil Group 1 shows good accuracy relative to the published correlations. The increase in gravel content changed the behavior and reduced the coefficient of correlation in soil Groups 2 and 3. The proposed correlation for soil Group 1 provides higher values for the elastic modulus for the same NSPT relative to the correlations found in the literature and this is due to the difference in soil (e.g. gravel content) and geological formation, its calcareous nature and its tendency to break under the SPT which reduces the equivalent NSPT. Conflict of interests The author wish to confirm that there is no known conflicts of interest associated with this publication and there isn’t any financial support for this work that could have influenced its outcome. References [1] J.L. Briaud, The Pressuremeter, first ed., A.A. Balkema, Rotterdam, Netherland, 1992. [2] P. Mayne, B.R. Christopher, J. DeJong, Manual of Subsurface Investigations, FHWA NHI-01-031, 2001. [3] K.H. Charif, A.M. ShadiNajjar, Comparative study of shear modulus in calcareous sand and sabkha soils, ASCE, GeoCongress 2012, Oakland, California, United States, March 25–29, 2012. [4] K. Phoon, F. Kulhawy, Evaluation of geotechnical variability, Can. Geotech. J. 36 (4) (1999) 625–639, http://dx.doi.org/ 10.1139/t99-039.
Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
6 [5] J.L. Briaud, Introduction to Soil Moduli, Geotechnical News, June 2001, BiTech Publishers Ltd, Richmond, B.C., Canada, ([email protected]). [6] S. Ohya, T. Imai, M. Matsubara, Relation between N value by SPT and LLT pressuremeter results, in: Proceeding, 2nd European Symposium on Penetration Testing, Amsterdam, vol. I, 1982, pp. 125–130. [7] J.L. Briaud, A. Noubani, A. Kilgore, L.M. Tucker, Correlation between Pressuremeter data and other parameters, Research Report, Civil Engineering, Texas A&M University, 1985 (Cited from J.L. Briaud, The Pressuremeter, A.A. Balkema, Rotterdam, 1992). [8] S. Yagiz, E. Akyol, G. Sen, Relationship between the standard penetration test and the pressuremeter test on sandy silty clays: a case study from Denizli, Bull. Eng. Geol. Environ. 67 (3) (2008) 405–410. [9] I. Bozbey, E. Togrol, Correlation of standard penetration test and pressuremeter data a case study from Estunbol, Turkey, Bull. Eng. Geol. Environ. 69 (2010) 505–515. [10] E. Kenmogne, J.R. Martin, S.A. Geofor, Correlation studies between SPT and Pressuremeter tests, in: Proceedings of the 15th African Regional Conference on Soil Mechanics and Geotechnical Engineering, 2011. [11] A. Cheshomi, M. Ghodrati, Estimating Menard pressuremeter modulus and limit pressure from SPT in silty sand and silty clay soils. A case study in Mashhad, Iran, Int. J., Geomech. Geoeng. 10 (3) (2014) 194–202. [12] F. Kulhawy, On the evaluation of static soil properties, in: Honoring Fred H. Kulhawy (Ed.), Foundation Engineering in
M.B. Anwar
[13]
[14]
[15]
[16]
[17]
[18]
[19] [20]
the Face of Uncertainty, Geotechnical Special Publication ASCE, 2013, pp. 56–76. T.M. ElKateb, H.E. Ali, CPT-SPT correlations for calcareous sand in Persian Gulf area, in: 2nd International Symposium on Cone Penetration Testing. California, vol. 2, May 2010. F. Kulhawy, P. Mayne, Manual on estimating soil properties for foundation design, in: Report no. EPRI-EL-6800, Electric Power Research Institute, EPRI, 1990. S.M. Ahmed, S.W. Agaiby, A.H. Abdel-Rahman, A unified CPT-SPT correlation for non-crushable and crushable cohesionless soil, Ain Shams Eng. J. 5 (2014) 63–73. M. Vafeian, D.W. Airey, J.P. Carter, M.K. Islam, Analysis of pressuremeter tests in calcareous soils, Engineering for Calcareous Sediments. Proceedings of the Second International Conference on Engineering for Calcareous Sediments, Bahrain, February 1999. J.A. Schneider, B.M. Lehane, Evaluation of cone penetration test data from a calcareous dune sand, in: 2nd International Symposium on Cone Penetration Testing, California, May 2010. J. Peuchen, Ruijter, S. Geodemoed, Commercial characterization of calcareous soils, in: Proceedings of the Second International Conference on Engineering for Calcareous Sediments, Bahrain, 1999. ASTM D1586, Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils. ASTM D4719-07, Standard Test Methods for Prebored Pressuremeter Testing in Soils.
Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
Housing and Building National Research Center
HBRC Journal http://ees.elsevier.com/hbrcj
FULL LENGTH ARTICLE
Correlation between PMT and SPT results for calcareous soil Mona B. Anwar * Associate Professor, Civil Engineering Department, The German University in Cairo, Egypt Associate Professor (on leave), Civil Engineering Department, Faculty of Engineering, Helwan University, Cairo, Egypt Received 26 October 2015; revised 12 February 2016; accepted 1 March 2016
KEYWORDS Pressuremeter; SPT; Calcareous; Elastic modulus
Abstract The simplicity and low cost of the standard penetration test (SPT) have always been the major advantages of this test over other field tests. Despite that other field tests (e.g. PMT, CPT, DMT, . . .) are supposed to provide more reliable results, yet they are still costly and not feasible in every project. Considering that SPT is available in all site investigation programs for all sizes of project, it was tempting to provide correlations between SPT results and other field test results. Through these correlations it will be feasible to estimate the soil parameters and deformation properties from the SPT number of blows. However, it is believed that correlations will differ, if the tested soil is calcareous. Furthermore, adopting local correlations is more favorable as it caters for the geological formation of the site. In this research it is aimed to obtain correlation between the PMT results and the SPT results for calcareous soil. A site investigation comprising boreholes with SPT and PMT was carried out near to the Red sea coast in Jeddah. The study was carried out to develop a local correlation between the results of SPT and PMT considering the effects of soil gradation and carbonate content. Comparison between the obtained correlation and other available correlations is also considered. Ó 2016 Housing and Building National Research Center. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Introduction
* Address: Civil Engineering Department, The German University in Cairo, Egypt. E-mail address: [email protected]. Peer review under responsibility of Housing and Building National Research Center.
Production and hosting by Elsevier
Pressuremeter test (PMT) was developed by Menard, in 1955 to measure the in situ soil deformation properties, Briaud [1]. The pressuremeter consists mainly of a long cylindrical probe that is expanded radially into the surrounding ground. By tracking the amount of volume of fluid and pressure used in inflating the probe, the data can be interpreted to give a complete stress–strain–strength curve. The insertion of the pressuremeter in ground depends on its type, either self-boring or pre-boring. PMT is considered theoretically sound in determining soil parameters and can test larger zone of soil mass than other in situ tests. Yet, PMT requires high level of skill
http://dx.doi.org/10.1016/j.hbrcj.2016.03.001 1687-4048 Ó 2016 Housing and Building National Research Center. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
2
M.B. Anwar
and can easily be damaged, and above all it is relatively expensive, Mayne et al. [2]. Actually this test is not carried out in conventional geotechnical site investigation for typical projects, Charif and ShadiNajjar [3]. On the other hand, there is the Standard Penetration Test (SPT), which is performed during the advance of the boreholes and is already carried out in all site investigation programs in nearly all boreholes due to its simplicity and low cost. Due to the availability of the SPT in every site investigation program, it was tempting to obtain correlations between SPT results (number of blows) and soil properties, namely shear strength parameters and soil deformation characteristic presented by the elastic modulus. Furthermore, correlations were also obtained to relate the results of the SPT to the results of other field tests (e.g. CPT, PMT, DMT). Nevertheless, despite the many available correlations between the SPT and the CPT, there are still limited number of correlations between the SPT and the PMT. The PMT provides a direct measurement of the horizontal modulus of soil. This modulus (EPMT) often is presumed to be roughly equivalent to the Young’s modulus (E), Phoon and Kulhawy [4]. Furthermore, both EH and EV are involved in the response of the vertical loading. Several investigations found that it was at most 5% difference between EH and EV, Briaud [1]. Nevertheless, soil elastic modulus is the most difficult parameter to obtain as it depends on many factors such as stress level, strain level, soil density and stress history, Briaud [5] and Charif and ShadiNajjar [3]. Attempts have been made to correlate the EPMT with the NSPT. Ohya et al. [6] proposed correlations for both clay soil and cohesionless soil in Japan, Fig. 1. The correlations are well known, yet they are fairly weak, Phoon and Kulhawy [4]. Briaud et al. [7] presented a database of preboring pressuremeter test data and other field tests data (i.e. CPT and SPT). The sites were located in USA, 36 of them were sand formation sites and 44 were clay formation sites. Best fit regressions were performed for the entire database. Eq. (1) presents the correlation proposed for the EPMT with NSPT in sand. However, the scatter in the correlations was found very large. This drastic scatter made these correlations useless in design, Briaud [1], Fig. 2a. blows blows Eo ðkPaÞ ¼ 383N ; Eo ðtsfÞ ¼ 4N ð1Þ 30 cm ft In 2008, Yagiz et al. [8] proposed correlations between NSPT and EPMT results for sandy silty clayey soil based on 15 boreholes in Turkey. The borehole depths were 5–8 m, and the tests were carried out at depth 1.5–2 m only. Regression analysis was undertaken and best fit regression between the parameters in a linear combination with 95% confidence level. The correlation is presented by Eq. (2). Fig. 2b presents the correlation, based on only 15 results. Em ¼ 388 Ncor þ 4554
ð2Þ
In 2010, Bozbey and Togrol [9], proposed a correlation based on case study of 182 tests in Turkey as given in Eqs. (3.a) and (3.b): For Sandy soil : EPMT ðMPaÞ ¼ 1:33ðN60 Þ0:77
ðr2 ¼ 0:82Þ ð3:aÞ
For Clayey soil : EPMT ðMPaÞ ¼ 1:61ðN60 Þ
0:71
ðr ¼ 0:72Þ 2
ð3:bÞ
Another correlation was given by Kenmogne et al. [10] based on site investigation data in Cameroon. The correlation was linear and is given in Eq. (4). Em ¼ b N
ð4Þ
where b = 2–8 for gravely sand. =2–20 for clayey sand. Cheshomi and Ghodrati [11] presented correlations for silty sand and silty clay soil based on case study in Iran (38 tests for silty clay soil and 16 tests for silty sand soil) given by Eqs. (5.a) and (5.b). These correlations are valid only for the range of NSPT measured in site (i.e. 9–50 number of blows). For silty sand : EPMT =Pa ¼ 9:8N60 94:3 ðr ¼ 0:79Þ
ð5:aÞ
For silty clay : EPMT =Pa ¼ 10N60 26:7 ðr ¼ 0:85Þ
ð5:bÞ
As presented above, the available correlations between the EPMT and the NSPT are either highly scattered (i.e. small correlation factor) or based on limited number of results. Yet they are representing local correlations that are developed within specific geologic setting. Reference to Phoon and Kulhawy [4] local correlations is preferable to generalized global correlations, but they need to be accurate, which leads to the need of more studies and data to develop these correlations into more mature state. However, all cases using empirical correlations should be with caution as it is linking two items together that are not directly related, Kulhawy [12]. Another factor needs to be considered when adopting those correlations. This factor is that these correlations are based on tests carried out in siliceous soil. Many references such as SPT, ElKateb and Ali [13], Kulhawy and Mayne [14], Ahmed et al. [15], Vafeian et al. [16], Schneider and Lehane [17] are discussing the difference in behavior between calcareous or carbonate soil and siliceous soil under field tests especially destructive tests. It is very likely that destructive testing as SPT can possibly break cementation of calcareous sand and may crush the actual sand particles resulting in change in the physical properties of the soil matrix, Charif and ShadiNajjar [3], which implies the need for specific correlations for this type of soil. The aim of this research was to provide correlation between the PMT and SPT results to be able to obtain the soil moduli taking into consideration the soil gradation and its calcareous nature. Site characterization The soil under study is located in Jeddah area, relatively near to the Red Sea coast. The soil formation comprised of interbedded layers of silty/clayey sand with silty/clayey gravel and sandy gravel, which is known as Wadi deposits. Cementation was observed at some depths. Such layers continued from ground surface down to 20 m depth. The in-situ compactness of these layers was found generally to be medium dense to very dense. Layers of the cohesive soil were encountered at shallow depths of 1.5 m in some boreholes and as deep as 18 m in others. The thickness of the sandy lean clay layer ranged from 1.5 to 3 m or more. The carried out site investigation comprised of many boreholes with depths ranging from 20 to 50 m. PMT was carried out in 17 BHs and SPT was also carried out at depth interval of 1.5 m. Groundwater was
Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
Correlation between PMT and SPT results
Fig. 1
3
Relationship between EPMT and NSPT value. Source: Ohya et al. [6].
Fig. 2b Relationship between measured and predicted Em. Source: Yagiz et al. [8].
Fig. 2a Example of correlations in sand from PMT data base. Source: Briaud et al. [7].
encountered at depths ranging from 4 m to 10 m. Laboratory tests (e.g. soil gradation, Atterberge limits, chemical analysis) were carried out to determine the index properties of soil which were used in soil classifications. The soil had carbonate content in the form of CaCo3 in average range of 5–20%, with some samples showing higher carbonate content up to 40%. Reference to modified Clark and Walker system, this soil is termed calcareous soil, Peuchen et al. [18]. Based on the gradation tests, soil showed very wide range of fine contents and gravel contents. Accordingly, to be able to study the correlation between NSPT and EPMT results, soil was divided into three groups based on the D50 values which are reflected on the gravel contents as well. Table 1 and Fig. 3 present the three soil groups. Standard penetration tests were carried out in the boreholes following ASTM D1586 [19]. Tests were carried out at 1.5 m
intervals. Fig. 4a presents the results of NSPT with depth for the 17 BHs. The PMT was also carried out at the same depth interval following the ASTM D4719 [20]. The pressuremeter tests were executed using the Prebored, G type Menard pressuremeter. The excavation for the PMT was carried out in the cleaned bottom of the boreholes to drill hole to fit the BX size probe. Fig. 4b presents the change of the obtained EPMT with depth for the 17 BHs. Results and discussion The relation between the NSPT and the corresponding EPMT at same levels was plotted for the three soil groups presented in Table 1. Regression analysis was carried out to calculate the least squares fit for the given points and the R-squared values were calculated to determine the accuracy of the relation. For soil Group 1, the relation between NSPT and EPMT is presented in Fig. 5. Values of the EPMT were normalized by the atmospheric pressure Pa (101 kPa). It is shown from figure that the scatter is relatively accepted relative to the correlations
Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
4
M.B. Anwar Table 1
Soil groups. D50
Fines content
Gravel content
Max. gravel size
Remarks
Group 1 Group 2 Group 3
<0.25 0.25–1 >1
25–50% 15–30% 0–20%
<25% 20–40% 35–70%
610 mm
Fines are silt or clay with low plasticity
Group 1
Up to 100 mm
referred to either refusal under the SPT spoon due to gravel, or crushing of gravel under the impact which, in both cases, will give misleading SPT results
Group 2
Group3
100
% pass
Soil Group 2 : EPMT =Pa ¼ 38:428ðNSPT Þ0:7385
ðR2 ¼ 0:385Þ ð7Þ
The same trend was observed in soil Group 3 as presented in Fig. 7 and by Eq. (8). The higher increase in gravel contents added to its large diameter (up to 100 mm) weakened the relation more and more which is reflected in the calculated R-squared.
50
0 0.001
0.01
0.1
1
10
100
Diameter (mm)
10000
EPMT / Pa
Fig. 3 Ranges of gradation for the 3 groups of soil used in the current study.
proposed in the literature. The obtained correlation is presented in Eq. (6). Soil Group 1 : EPMT =Pa ¼ 33:92ðNSPT Þ0:803
ðR2 ¼ 0:71Þ
100
ð6Þ The same procedures were carried out for soil Group 2 and the results are presented in Fig. 6 and the correlation is given by Eq. (7). The regression analysis for soil Group 2 showed less accuracy for the obtained correlation as the calculated R-squared was found to be only 0.385. This higher scatter can be referred to the higher gravel content which increases the inconsistency of the SPT results. This inconsistency is
Level (MSL - m)
15
0
100
y = 33.927x0.803 R² = 0.7104
Soil Group 1 10
10
200
300
Fig. 5
15
10
10
5
5
0
0
-5
-5
-10
-10
-15
-15
Fig. 4
100
1000
NSPT (blows/30)
Relation between (EPMT/Pa) and (NSPT) for soil Group 1.
(b)
NSPT
(a)
1000
EPMT - (MPa) 0
100
200
300
400
Field test results.
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Correlation between PMT and SPT results
5
10000
Predicted by the proposed correlaon Yagiz et al 2008 Sandy silty clayey soil Bozbey & Togrol 2010 Sandy soil
1500
EPMT/ Pa
1000
EPMT /Pa
1000 100
y = 38.428x 0.7385 R² = 0.3851
500
Soil Group 2 10 10
100
1000
NSPT (blows/30)
0 0
Relation between (EPMT/Pa) and (NSPT) for soil Group 2.
Fig. 6
Fig. 8
10000
50
100
N SPT (blows/30cm) Relation between (NSPT) and the predicted (EPMT/Pa).
are preferred than global ones to cater for the site specific formation. 1000
EPMT/ Pa
Conclusions
100
y = 178.14x0.4398 R² = 0.1205
Soil Group 3 10
10
100
1000
NSPT (blows/30)
Fig. 7
Relation between (EPMT/Pa) and (NSPT) for soil Group 3.
Soil Group 3 : EPMT =Pa ¼ 178:14ðNSPT Þ0:4398
ðR2 ¼ 0:12Þ ð8Þ
Based on the above regression analysis, it can be concluded that the applicability of correlation between the EPMT and NSPT is eliminated by the increase in gravel content and gravel diameter. To compare the correlation of soil Group 1 with those presented in the literature, the predicted values of E, using Eq. (6) for soil Group 1, were plotted versus the measured NSPT and presented in Fig. 8. Correlations cited from Yagiz et al. [8] and Bozbey and Togrol [9] were also used to predict the E values for the measured NSPT and results are presented in Fig. 8. Other correlations from the literature were limited either to small range of NSPT Cheshomi and Ghodrati [11] or having drastic scatter, Briaud [1] and Ohya et al. [6]. It is noticed from the figure that the results from the proposed correlation is higher than those of the literature. The difference can be attributed to the different soil and geologic formation, calcareous nature and cementation in some depths. Accordingly, as stated above local correlations
The proposed correlation, for soil Group 1, is considered as local correlation for this formation in Jeddah and also can be considered applicable for soils having the same gradation and similar geologic formation. The proposed correlation for soil Group 1 shows good accuracy relative to the published correlations. The increase in gravel content changed the behavior and reduced the coefficient of correlation in soil Groups 2 and 3. The proposed correlation for soil Group 1 provides higher values for the elastic modulus for the same NSPT relative to the correlations found in the literature and this is due to the difference in soil (e.g. gravel content) and geological formation, its calcareous nature and its tendency to break under the SPT which reduces the equivalent NSPT. Conflict of interests The author wish to confirm that there is no known conflicts of interest associated with this publication and there isn’t any financial support for this work that could have influenced its outcome. References [1] J.L. Briaud, The Pressuremeter, first ed., A.A. Balkema, Rotterdam, Netherland, 1992. [2] P. Mayne, B.R. Christopher, J. DeJong, Manual of Subsurface Investigations, FHWA NHI-01-031, 2001. [3] K.H. Charif, A.M. ShadiNajjar, Comparative study of shear modulus in calcareous sand and sabkha soils, ASCE, GeoCongress 2012, Oakland, California, United States, March 25–29, 2012. [4] K. Phoon, F. Kulhawy, Evaluation of geotechnical variability, Can. Geotech. J. 36 (4) (1999) 625–639, http://dx.doi.org/ 10.1139/t99-039.
Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001
6 [5] J.L. Briaud, Introduction to Soil Moduli, Geotechnical News, June 2001, BiTech Publishers Ltd, Richmond, B.C., Canada, ([email protected]). [6] S. Ohya, T. Imai, M. Matsubara, Relation between N value by SPT and LLT pressuremeter results, in: Proceeding, 2nd European Symposium on Penetration Testing, Amsterdam, vol. I, 1982, pp. 125–130. [7] J.L. Briaud, A. Noubani, A. Kilgore, L.M. Tucker, Correlation between Pressuremeter data and other parameters, Research Report, Civil Engineering, Texas A&M University, 1985 (Cited from J.L. Briaud, The Pressuremeter, A.A. Balkema, Rotterdam, 1992). [8] S. Yagiz, E. Akyol, G. Sen, Relationship between the standard penetration test and the pressuremeter test on sandy silty clays: a case study from Denizli, Bull. Eng. Geol. Environ. 67 (3) (2008) 405–410. [9] I. Bozbey, E. Togrol, Correlation of standard penetration test and pressuremeter data a case study from Estunbol, Turkey, Bull. Eng. Geol. Environ. 69 (2010) 505–515. [10] E. Kenmogne, J.R. Martin, S.A. Geofor, Correlation studies between SPT and Pressuremeter tests, in: Proceedings of the 15th African Regional Conference on Soil Mechanics and Geotechnical Engineering, 2011. [11] A. Cheshomi, M. Ghodrati, Estimating Menard pressuremeter modulus and limit pressure from SPT in silty sand and silty clay soils. A case study in Mashhad, Iran, Int. J., Geomech. Geoeng. 10 (3) (2014) 194–202. [12] F. Kulhawy, On the evaluation of static soil properties, in: Honoring Fred H. Kulhawy (Ed.), Foundation Engineering in
M.B. Anwar
[13]
[14]
[15]
[16]
[17]
[18]
[19] [20]
the Face of Uncertainty, Geotechnical Special Publication ASCE, 2013, pp. 56–76. T.M. ElKateb, H.E. Ali, CPT-SPT correlations for calcareous sand in Persian Gulf area, in: 2nd International Symposium on Cone Penetration Testing. California, vol. 2, May 2010. F. Kulhawy, P. Mayne, Manual on estimating soil properties for foundation design, in: Report no. EPRI-EL-6800, Electric Power Research Institute, EPRI, 1990. S.M. Ahmed, S.W. Agaiby, A.H. Abdel-Rahman, A unified CPT-SPT correlation for non-crushable and crushable cohesionless soil, Ain Shams Eng. J. 5 (2014) 63–73. M. Vafeian, D.W. Airey, J.P. Carter, M.K. Islam, Analysis of pressuremeter tests in calcareous soils, Engineering for Calcareous Sediments. Proceedings of the Second International Conference on Engineering for Calcareous Sediments, Bahrain, February 1999. J.A. Schneider, B.M. Lehane, Evaluation of cone penetration test data from a calcareous dune sand, in: 2nd International Symposium on Cone Penetration Testing, California, May 2010. J. Peuchen, Ruijter, S. Geodemoed, Commercial characterization of calcareous soils, in: Proceedings of the Second International Conference on Engineering for Calcareous Sediments, Bahrain, 1999. ASTM D1586, Standard Test Method for Penetration Test and Split-Barrel Sampling of Soils. ASTM D4719-07, Standard Test Methods for Prebored Pressuremeter Testing in Soils.
Please cite this article in press as: M.B. Anwar, Correlation between PMT and SPT results for calcareous soil, HBRC Journal (2016), http://dx.doi.org/10.1016/j. hbrcj.2016.03.001