Re-examination of Undrained Strength at Atterberg Limits Water Contents
H. B. Nagaraj, A. Sridharan & H. M. Mallikarjuna
Geotechnical and Geological Engineering An International Journal ISSN 0960-3182 Volume 30 Number 4 Geotech Geol Eng (2012) 30:727-736 DOI 10.1007/s10706-011-9489-7
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Author's personal copy Geotech Geol Eng (2012) 30:727–736 DOI 10.1007/s10706-011-9489-7
ORIGINAL PAPER
Re-examination of Undrained Strength at Atterberg Limits Water Contents H. B. Nagaraj • A. Sridharan H. M. Mallikarjuna
•
Received: 12 August 2011 / Accepted: 27 December 2011 / Published online: 7 January 2012 Ó Springer Science+Business Media B.V. 2012
Abstract Most of the testing procedures to determine liquid limit and plastic limit are strength based with the assumption that, irrespective of the soil type, the strengths at these limiting water contents are considered to be unique, being equal to 1.7 and 170 kN/ m2, respectively. Based on this, the plastic limit has been redefined as the water content at which there is a 100-fold increase in undrained strength as compared to that of liquid limit water content, and the range of water contents producing this strength variation as the plasticity index. However, published data from the various literature sources clearly show that the variation of undrained shear strength at the liquid limit water content is observed to be nearly sixty times, and that at plastic limit is more than seventeen times, and hence, no unique value of undrained strength can be assigned either at the liquid limit or plastic limit of soils. The
H. B. Nagaraj (&) Department of Civil Engineering, BMS College of Engineering, Bangalore 560 019, India e-mail:
[email protected] A. Sridharan Indian National Science Academy and Formerly Professor of Civil Engineering, Indian Institute of Science, Bangalore 560 012, India e-mail:
[email protected] H. M. Mallikarjuna Department of Civil Engineering, R.Y.M.E.C, Bellary 583 104, India e-mail:
[email protected]
variation of undrained strength with water content has been well documented in literature. Thus, uniqueness of strength at liquid limit or plastic limit, which is nothing but water holding capacity of soils at different state of consistencies, is not tenable. Keywords Clays Fine-grained soils Atterberg limits Plasticity Undrained shear strength
1 Introduction In 1911, Atterberg proposed the limits of consistency for agricultural purposes to get a clear concept of the range of water contents of a soil in the plastic state (Casagrande 1932). These limits of consistency namely liquid limit (wL) and plastic limit (wP), well known as Atterberg limits (Casagrande 1932, 1958), were standardized by Casagrande (1932, 1958) and adopted for classification of fine-grained soils. These limits are determined using simple tests, which are essentially strength based. Attempts have been made from 1911 onwards to understand Atterberg limits better and develop improved methods of determining the same. Research contribution continues to be made on Atterberg limits (very recently by Sridharan and Prakash 1998; Sridharan and Nagaraj 1999; Sridharan et al. 2000; Prakash and Sridharan 2006; Nagaraj and Sridharan 2010). Because of the various limitations of the rolling thread method of determining plastic limit, especially the
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personal errors, attempts have also been made to find the same from cone method (e.g. Hansbo 1957; Towner 1973; Campbell 1976, 1983; Wood and Wroth 1978; Belviso et al. 1985; Sampson and Netterberg 1985; Wasti and Bezirci 1986; Rao 1987; Harison 1988; Feng 2004; Al-Dahlaki and Al-Sharify 2008; Rashid et al. 2008; Lee and Freeman 2009; Sivakumar et al. 2009). Wroth and Wood (1978) have tried to redefine plastic limit in terms of strength as that water content that gives a 100-fold increase in shear strength over that at the liquid limit. Based on this concept attempts have been made to develop an instrumented cone penetrometer to determine the plastic limit (Stone and Phan 1995). Recently Sridharan et al. (1999) have proposed a method to determine plastic limit through the correlation developed between plasticity index and flow index. In most of the attempts to develop the testing procedures to determine liquid limit and plastic limit, researchers have tried to define liquid limit and plastic limit as strength based water content, and hence, the testing procedures to determine them. However, this way of defining Atterberg limits deviates from the basic physical meaning, which is the water holding capacity of the soil at those states of consistency. Lambe and Whitman (1979) related Atterberg limits for a soil to the amount of water attracted to the surface of the soil particles. It is well brought out by Sridharan and Venkatappa Rao (1979), Sridharan et al. (1986, 1988), Sridharan and Prakash (1999) that the mechanisms controlling undrained shear strength and liquid limit for kaolinitic soils is different from that of montmorillonitic soils. This being the fact, it cannot be expected that the strength at the liquid limit water content to be unique for all soils. This aspect has been confirmed by the results reported by Kenney (1963) and Youseff et al. (1965). Atterberg limits are very important from understanding the behaviour of fine-grained soils, but correlations of the same with the undrained shear strength are to be reexamined. In this paper, an attempt has been made to understand better on the shear strength at liquid limit and plastic limit water contents from the data available in the literature.
2 Liquid Limit Atterberg defined liquid limit as the arbitrary limiting water content at which the soil is liquid enough to flow
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i.e., the water content above which the soil behaves as a viscous liquid (i.e., a soil–water mixture with little measurable shear strength). 2.1 Discussion on Strength at Liquid Limit Water Content Casagrande (1932, 1958) deduced that the liquid limit corresponds approximately to a water content at which the soil has shear strength of about 2.5 kPa. Norman (1958) reported shear strength at liquid limit water content ranging from 0.8 to 1.6 kPa for B.S Standard rubber base Casagrande’s apparatus (percussion cup) and 1.1–2.3 kPa for ASTM Standard rubber base Casagrande’s apparatus. Skopek and Ter-stepanian (1975) have reported shear strength values in the range of 1 and 3 kPa at the liquid limit water content in the percussion cup method. Skempton and Northey (1953) reported shear strength values in the range of 0.7–1.75 kPa. Though both the percussion cup method and the cone method are basically strength tests, the undrained shear strengths at liquid limit water contents obtained by either of the two methods are quite varied (Houlsby 1982). The undrained shear strengths observed at liquid limit water contents by the percussion cup method vary between 0.5 and 5.6 kPa with the same or different base material (e.g. Whyte 1982; Wasti and Bezirci 1986); and in the case of cone method, this variation is observed to be between 0.8 and 4.8 kPa (Wasti and Bezirci 1986). Houlsby (1982, 1983) has shown theoretically that the shear strength at the liquid limit water content determined by the cone method varies from 2.75 to 5.24 kPa. Youseff et al. (1965) tested a large number of remolded clays, measuring the shear strength with a laboratory vane as the water content was varied in the neighbourhood of the liquid limit. They observed a clear trend of decreasing shear strength with increasing value of the liquid limit. Over the range of liquid limit of 30–200% the range of shear strength observed was 1.3–2.7 kPa. They also reportedly stated that: ‘‘although the strength at liquid limit is essentially small, a big relative difference is to be noted’’. Earlier, Kenney (1963) has also reported variation of shear strengths observed for different soils at their liquid limit water contents. Recently, Kayabali and Tufenkci (2010) have reported a variation of undrained strength at liquid limit ranging from 1.2 to 12 kPa. Table 1
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Table 1 Variation of undrained strength at liquid limit water content as reported in the literature Sl. No.
Range of undrained strength at liquid limit water content (kPa)
Range of liquid limit
Test adopted to determine undrained strength
Remarks
Reference and Year
1
0.8–1.6 (B.S Standards)
41–72
Miniature vane shear apparatus
Percussion cup method.
Norman (1958)
1.1–2.3 (ASTM Standards)
Effect of different rubber bases used on the undrained strength
2
0.7–1.75
30–97
Vane shear test
Percussion cup method
Skempton and Northey (1953)
3
1.3–2.7
32–190
Vane shear test
Percussion cup method
Youseff et al. (1965)
4
1–3
17–382
Vane shear test
Percussion cup method
5
Mean value of 1.7
26–190
Vane shear test
Percussion cup method
Skopek and Ter-Stepanian (1975) Wroth and Wood (1978)
6
2.75–5.24
–
–
Theoretical Analysis
Houlsby (1982, 1983)
7
1.7–2.8
36–159
Vane shear test
Cone method
Federico (1983)
Vane shear test
Percussion cup method and Cone method
Wasti and Bezirci (1986)
8
0.5–5.6
27–526
0.8–4.8
30–328
9
0.2–2.04
27.4–62.8
Viscometer
Cone method
Locat and Demers (1988)
10
0.66–1.35
29.8–100.8
Viscometer
–
Sridharan and Prakash (1998)
11
1.2–12.0
26.4–83.6
Vane shear test
Percussion cup method
Kayabali and Tufenkci (2010)
summarizes the undrained strength at liquid limit water as reported by various researchers in the literature. From the above it can be observed that the undrained shear strength values at liquid limit water content is quite variable and are both test dependent and on the soil type. The variation of the shear strength with soil type being important, which is observed to vary nearly sixty times i.e., from as low as 0.2 kPa to as high as 12 kPa, suggesting that the shear strength of soils at liquid limit water content is not a unique value and the definition of liquid limit based on shear strength is to be re-examined.
3 Plastic Limit Atterberg defined plastic limit as the water content at which the clay paste cannot be rolled into a thread (Casagrande 1932). Casagrande developed a method popularly known as the rolling thread method to determine plastic limit of soils. In this method, a mass of soil is rolled into a
thread by hand with a sufficient pressure and at a specified rate. The moisture content, expressed as a percentage of the weight of oven dried soil at which the soil mass will just begin to crumble when rolled into a thread of about 3 mm is considered as the plastic limit. Thus, the plastic limit of a soil is a measure of cohesion of the soil particles to cracking when the sample is worked (Yong and Warkentin 1976). The cohesion between particles or units of particles must be sufficiently low to allow the particles to maintain the new molded position. At this water content, the particles will slide past one another on application of force, but there is sufficient cohesion to allow them to retain shape. However, reliable estimation of plastic limit from this test is dependent on the personal judgement of the operator. 3.1 Discussion on Strength at Plastic Limit Water Content Schofield and Wroth (1968) proposed that the failure mechanism in the plastic limit test is analogous to the Brazilian split cylinder test used to establish the tensile
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strength of concrete. However, unlike the cone penetrometer test, the rolling thread method of determining plastic limit does not provide a direct strength index. Therefore, based on two considerations, firstly that the rolling thread method of determining plastic limit is subjected to personal errors, and secondly, that it was desirable to evaluate the plastic limit as a measure of strength in a similar manner as liquid limit is determined using cone penetrometer, attempts were made to use the same to determine plastic limit (e.g. Hansbo 1957, Towner 1973; Campbell 1976, 1983; Belviso et al. 1985; Sampson and Netterberg 1985, Wasti and Bezirci 1986; Rao 1987; Harison 1988; Stone and Phan 1995; Rashid et al. 2008). Towner (1973) and Harison (1988) suggested that the moisture content corresponding to 2-mm penetration might be taken as the plastic limit. Campbell (1976) felt that the moisture content corresponding to minimum of the moisture content versus cone penetration curve (which on an average corresponded to 1.36-mm depth of penetration) could be taken as the plastic limit. Sampson and Netterberg (1985) suggested that the moisture content corresponding to 5-mm depth of penetration should be taken as the plastic limit. Though many attempts have been made to obtain plastic limit from the cone penetrometer itself, there is lot of ambiguity about the depth of penetration at which the plastic limit can be taken. A school of thought from Cambridge group was working parallelly using critical state concept to develop a correlation between the strength of soils at plastic limit in terms of the strength at the liquid limit. Wroth and Wood (1978) tried to redefine plastic limit in terms of strength as that water content that gives a 100fold increase in shear strength over that at the liquid limit. Using the limited data of four soils from Skempton and Northey (1953), Wroth and Wood (1978) approximated the undrained shear strength at plastic limit water content as 170 kPa, and assumed it nearly 100 times the averaged undrained shear strength of 1.7 kPa at the liquid limit, which they obtained from the work of Youseff et al. (1965). With this assumption in the background, using critical state concepts and a series of cone penetration tests with two different cone mass of m1 (80 g) and m2 (240 g), Wroth and Wood (1978) showed the following relationships to obtain the plasticity index, Ip and hence the plastic limit, wp: Ip ¼ D log10 100= log10 ðm2 =m1 Þ
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ð1Þ
where D is the vertical separation in water content on the linear plots of water content versus logarithm of penetration depth, d for the two cones of mass m1 and m2. Following the approach of Wroth and Wood (1978), Stone and Phan (1995) developed an instrumented cone penetrometer to establish the moisture content of soil with strength 100 times that of the liquid limit which could be defined as the plastic limit. But the method has not got universal acceptance. Recently Sharma and Bora (2003) have furthered this concept of 100-fold increase in shear strength at plastic limit water content over that at the liquid limit with their set of experimental results. Prakash (2003) discussed citing reasons for the fallacy of their support to the above concept. It is understood that the plastic limit of a soil is a measure of cohesion of the soil particles to cracking when the sample is worked (Yong and Warkentin 1976). Recently, Sridharan and Prakash (1999) have summarized the two concepts identified from the literature regarding the development of cohesion in clays. According to the first concept, cohesion is due to the viscosity of double-layer water, a part of which is the adsorbed water surrounding the soil particles. The second concept is that the cohesion is due to the manifestation of net inter particle attractive forces in the clay-electrolyte system. In order to verify the above two concepts, they made a detail study, and came to the following conclusions: 1.
2.
The undrained strength of montmorillonitic soils is primarily due to the viscous shear resistance due to diffuse double-layer water and that of kaolinitic soils is primarily due to the net attractive force and the mode of particle arrangement as dictated by the inter-particle forces. Cohesion is due to inter-particle attraction, which results in increased flocculation and higher shear strength at the particle level in the case of kaolinitic soils and to the viscous resistance of double-layer water in the case of montmorillonitic soils.
4 Variation of Undrained Strength with Water Content The variation of undrained strength of soil with water content has been well documented in literature
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4.1 Discussion on Undrained Strength at Liquid Limit and Plastic Limit Water Contents
(Towner 1973; Federico 1983; Zreik et al. 1997; Lee 2004; Trauner et al. 2005; Hong, et al. 2006). The various forms of relationship of undrained strength with ratio of water content to liquid limit (Federico 1983; Lee 2004; Berilgen et al. 2007); undrained strength (either Cu or Su) with liquidity index (Skempton and Northey 1953; Schofield and Wroth 1968; Whyte 1982; Leroueil 1983; Locat and Demers 1988; Yilmaz 2000; Koumoto and Houlsby 2001; Berilgen et al. 2007, to name a few); Cu with water content (Berilgen et al. 2007); Cu with consistency index (Berilgen et al. 2007) as reported by various researchers has been tabulated in Table 2. The recent work in this direction as reported by Edil and Benson (2009) relating Cu with liquid limit (Eq. 13 in Table 2) is quite revealing. The variation of compressive strength of even rock with water content has been reported in the literature (Romana and Va´sa´rhelyi 2007), bringing out the fact that strength is a function of water content. From above discussion, it is clear that soils cannot have a unique value of strength at different values of water contents. Liquid limit or plastic limit being the water holding capacity of the soil at different states of consistency, it can be inferred that different soils having varied values of liquid limit or plastic cannot be presumed to have unique undrained strength. Table 2 Correlation between undrained strength with physical properties of soil
Eq. No.
Results of undrained strength at liquid limit and plastic limit water contents from the literature (Wasti and Bezirci 1986; Kayabali and Tufenkci 2010) are presented here. Figure 1 is a plot of undrained strength at liquid limit water content obtained both from Casagrande’s percussion cup device and cone penetration method. It can be seen from the figure that the strength at liquid limit is not unique and the variation is quite significant (about 60 times). It can be observed that the strength has reduced with the increase in liquid limit, though with scatter. Additionally, the undrained strength of a clayey soil also depends on the dominant clay mineral present and the mechanism that controls the behaviour in the method adopted, and hence the scatter. This aspect has been well brought out by Sridharan and Prakash (2000). The undrained strength at plastic limit water content versus plastic limit obtained by both Casagrande’s rolling thread method, and by Cone method (Wasti and Bezirci 1986; Kayabali and Tufenkci 2010) has been presented in Fig. 2. It can be seen that the undrained strength is quite variable, ranging from as high as 600 kPa to as low as 35 kPa (about seventeen times variation). Figure 3 is a similar plot of undrained strength at plastic limit water content versus
Equation
1 Cu ¼ e
5:25 1:161ww
Author and year
Cu relating w/wL
Federico (1983)
L
2 Cu ¼ 182:93 e 3
2:3714
2:86
Lee (2004)
w wL
Cu ¼ 145 e
Berilgen et al. (2007)
w wL
4
ln ðcu Þ ¼ 11:5 2:2 lnðwÞ
5
Cu ¼ 282:61 lnðwÞ
6
Cu ¼ 1:6 e4:23 ð1IL Þ 2:64 Cu ¼ 19:8 I
7
Remarks
Cu relating w
Berilgen et al. (2007)
Cu relating IL
Whyte (1982) Locat and Demers (1988)
L
Cu or Su as reported in the equations presented in Table 2 are expressed in kPa, except Eq. 2, which is expressed in psf
8
Cu ¼ 28 e 1:33 IL
9
Cu ¼ 8:55 e1:25 IC 1 2 ðIL 0:21Þ
10
Su ¼
11
Su ¼ 170 eð 4:6 IL Þ
Berilgen et al. (2007) Cu relating IC
Berilgen et al. (2007)
Su relating IL
Leroueil et al. (1983) Schofield and Wroth (1968)
ð1:72 IL Þ
12
Su ¼ 144:9 e
13
Su ¼ 191:4 e ð0:03 wL Þ
Edil and Benson (2009) Su relating wL
Edil and Benson (2009)
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Fig. 1 Undrained strength at liquid limit versus liquid limit by both Casagrande’s and cone method (data after Wasti and Bezirci 1986; Kayabali and Tufenkci 2010)
plastic limit obtained from Dennehy (1978). Here also there is a varying trend of the undrained strength (about seven times variation), ranging from as high as 220 kPa to as low as 30 kPa, averaging to a value of about 115 kPa. Most of the undrained strength data at plastic limit presented in Figs. 2 and 3 are quite different from the assumed average value of strength at plastic limit of 170 kPa by various researchers in the literature, for e.g., Wroth and Wood 1978, Stone and Phan 1995 and Sharma and Bora 2003. Here, it is appropriate to present the remoulded undrained strength of natural deposits independently reported in literature (Bell 2002) as given below. Bell (2002) in his study of geotechnical properties of some till deposits occurring along the coastal areas of eastern England has reported the mean values of remoulded undrained strength of soils at natural water content, which are very close to their plastic limits and have shown a decreasing trend with increase in water content and also the values range from 81 to 164 kPa, as tabulated in Table 3 and presented in Fig. 4. From Fig. 4, it is clear that remolded undrained strength is a function of the water content of the soil (very close to the plastic limit) at which the strength is determined.
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Fig. 2 Undrained strength at plastic limit versus plastic limit by both Casagrande’s and cone method (data after Wasti and Bezirci 1986; Kayabali and Tufenkci 2010)
Fig. 3 Undrained strength at plastic limit versus plastic limit by Casagrande’s method (data after Dennehy 1978)
The assumption that there is a 100-fold increase in strength at plastic limit water content as compared to that of liquid limit water content has found a strong
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Table 3 Physical properties and remolded undrained strength of natural soils for literature (Bell 2002) Soil description
Average natural moisture content wn (%)
Average plastic limit wP (%)
Remolded undrained strength at natural moisture content (kN/m2)
Hunstanton till
17.6
18.0
134
Chalky boulder
23.6
20.0
81
Contorted drift
15.6
14.0
136
Cromer till
13.2
17.0
156
Hessle till
22.6
22.0
96
Withernsea till
16.9
18.0
136
Skipsea till
15.5
16.0
164
Basement till
17.0
20.0
156
Fig. 5 Undrained strength ratio at plastic limit to liquid limit versus liquid limit by both Casagrande’s and cone method (data after Wasti and Bezirci 1986; Kayabali and Tufenkci 2010)
Fig. 4 Remoulded undrained strength versus natural water content (data after Bell 2002)
foot hold in geotechnical literature. To verify this fact, plot of ratio of undrained strength at plastic limit to liquid limit (as plotted in Figs. 1 and 2) versus liquid limit by both Casagrande’s method and cone method are presented in Fig. 5. From this figure, it can be seen that the undrained strength ratio at plastic limit to that of liquid limit is quite variable, being as low as 15 to as high as 295. It can also be observed that the strength ratio has an increasing trend with the liquid limit.
Fig. 6 Undrained strength ratio at plastic limit to liquid limit versus plastic limit by both Casagrande’s and cone method (data after Wasti and Bezirci 1986; Kayabali and Tufenkci 2010)
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Fig. 7 Undrained strength ratio at plastic limit to liquid limit versus ratio of liquid limit to plastic limit by both Casagrande’s and cone method (data after Wasti and Bezirci 1986; Kayabali and Tufenkci 2010)
Figure 6 is a plot of the same strength ratio versus plastic limit, which is observed to have a decreasing trend with the plastic limit. From Figs. 5 and 6, it is further evident that undrained strength is having a functional dependency of water content. To further verify this fact, the strength ratio is plotted versus the ratio of liquid limit to plastic limit, and strength ratio versus plasticity index as shown in Figs. 7 and 8, respectively. From these figures the strength ratio is found to increase with the ratio of liquid limit to plastic limit or increase in plasticity index. The correlation of strength ratio is better with the ratio of liquid limit to plastic limit. With the above discussion, it can be understood that shear strength is not unique both at liquid limit and plastic limit. This being the fact, it would be misleading to redefine the plastic limit in terms of strength as that water content that gives a 100-fold increase in shear strength over that at the liquid limit. Also, it would be appropriate here to quote from the study of remolded strength of cohesive soils by Dennehy (1978) that: ‘‘Universal limits in terms of a multiplicand of plastic limit are found to be inappropriate’’.
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Fig. 8 Undrained strength ratio at plastic limit to liquid limit versus plasticity index by both Casagrande’s and cone method (data after Wasti and Bezirci 1986; Kayabali and Tufenkci 2010)
Earlier it was seen that though the value of undrained shear strength at the liquid limit water content is less, the variation was observed to be nearly sixty times and that at plastic limit to be as high as seventeen times. The ratio of undrained strength at plastic limit to liquid limit could vary significantly. Hence, any attempt to relate the undrained shear strength at plastic limit water content in terms of that at liquid limit water content leads to incorrect predictions and hence is not tenable.
5 Conclusions Published data from the various literature sources clearly show that there is no unique value of undrained strength that can be assigned either to the liquid limit or plastic limit of soils. Further, critical analysis has revealed that the mechanisms involved in controlling liquid and plastic limits of fine-grained soils are very different dependent on the type of apparatus used and amount of clay minerals with associated cations present in the soils. Hence, any attempt to relate the
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undrained shear strength at plastic limit water content in terms of that at liquid limit water content leads to incorrect predictions. Acknowledgments The first author sincerely thanks his former graduate student Sravan Muguda for his active involvement in the preparation of the paper.
References Al-dahlaki H, Al-Sharify GA (2008) A proposed approach for plastic limit determination using the drop-cone penetrometer device. J Eng Dev 12(1):107–117 Bell FG (2002) The geotechnical properties of some till deposits occurring along the coastal areas of eastern England. Eng Geol 63:49–68 Belviso R, Ciampoli S, Cotecchia V, Federico A (1985) Use of the cone penetrometer to determine consistency limits. Ground Eng 18(5):21–22 ¨ zaydın K (2007) Determination of Berilgen SA, Kılıc¸, H, O undrained shear strength for dredged golden horn marine clay with laboratory tests. Proceedings of the Sri Lankan geotechnical society’s first international conference on soil & rock engineering, August 5–11, Colombo, Sri Lanka Campbell DJ (1976) Plastic limit determination using a drop cone penetrometer. Soil Sci 27(3):295–300 Campbell DJ (1983) Discussion. Geˆotechnique 33(1):78–79 Casagrande A (1932) Research on the atterberg limits of soils. Public Roads 13(3):121–130 (136) Casagrande A (1958) Notes on the design of the liquid limit device. Geˆotechnique 8(2):84–91 Dennehy JP (1978) The remoulded undrained shear strength of cohesive soils and its influence on the suitability of embankment fill. In: proceedings of international conference on clay fills. Institution of Engineers, London, pp. 87–94 Edil TB, Benson CH (2009) Comparison of basic laboratory test results with more sophisticated laboratory and in situ tests methods on soils in southeastern Wisconsin. Final report of Wisconsin highway research program #0092-06-05, pp. 11–12 Federico A (1983) Relationships (Cu–w) and (Cu–s) for remolded clayey soils at high water content. Riv Ital Geotech 17(1):38–41 Feng TW (2004) Using a small ring and a fall-cone to determine the plastic limit. J Geotech Geoenvi Eng 130(6):630–635 Hansbo S (1957) A new approach to the determination of the shear strength of clay by fall-cone test. Proceedings of Royal Swedish Geotechnical Institute, vol 14, pp. 7–47 Harison JA (1988) Using the BS cone penetrometer for the determination of the plastic limit of soils. Geˆotechnique 38(3):433–438 Hong Z, Liuz S, Shen S, Negami T (2006) Comparison in Undrained Shear Strength between Undisturbed and Remolded Ariake Clays. J Geotech Geoenv Eng 132(2):272–275 Houlsby GT (1982) Theoretical analysis of the fall cone test. Geotechnique 32(2):111–118 Houlsby GT (1983) Discussion. Geˆotechnique 33(4):463
735 Kayabali K, Tufenkci OO (2010) Shear strength of remolded soils at consistency limits. Can Geotech J 47(3):259–266 Kenney TC (1963) Atterberg limits, correspondence. Geˆotechnique 13(2):159–162 Koumoto T, Houlsby GT (2001) Theory and practice of the fall cone test. Geˆotechnique 51(8):701–712 Lambe TW, Whitman RV (1979) Soil mechanics. John Wiley & Sons, New York, p 31 Lee LT (2004) Predicting geotechnical parameters for dredged materials using the slump test method and index property correlations. DOER Technical Notes collection (ERDC TNDOER-D-1), U.S. Army Engineer Research and Development Center, Vicksburg, Mississippi. http://www.wes.army. mil/el/dots/doer Lee LT, Freeman RB (2009) Dual-weight fall cone method for simultaneous liquid limit determination. J Geotech Geoenvi Eng 135(1):158–161 Leroueil S, Tavenas F, Le Bihan JP (1983) Proprie´te´s caracte´ristiques des argiles de l’est du canada (Characteristic properties of eastern Canada clays). Can Geotech J 20(4):681–705 Locat J, Demers D (1988) Viscosity, yield stress, remolded strength, and liquidity index relationships for sensitive clays. Can Geotech J 25(4):799–806 Nagaraj HB, Sridharan A (2010) An Improved ko-stress method of determining liquid limit of soils. Int J Geotech Eng 4(4):549–555 Norman LEJ (1958) A comparison of values of liquid limit determined with apparatus having bases of different hardness. Geˆotechnique 8(2):79–83 Prakash K (2003) Discussion. J Geotech Geoenvi Eng 129(8):774–779 Prakash K, Sridharan A (2006) Critical appraisal of the cone penetration method of determining soil plasticity. Can Geotech J 43(5):884–888 Rao HY (1987) Determination of Atterberg limits by cone penetrometer. In: Proceedings of 8th asian regional conference on soil mechanics and foundation engineering, vol 1. Kyoto, pp. 81–84 Rashid ASA, Kassim KA, Katimon A, Noor NM (2008) Determination of Plastic limit of soil using modified methods. Malays J Civ Eng 20(2):295–305 Romana M, Va´sa´rhelyi B (2007) A discussion on the decrease of unconfined compressive strength between saturated and dry rock samples. Proceedings of 11th congress of the international society for rock mechanics vol 1. Lisbon, pp. 139–142 Sampson LR, Netterberg F (1985) The cone penetration index: a simple new soil index test to replace the plasticity index. In: Proceedings of 11th international conference on soil mechanics and foundation engineering, vo1 2. San Fransisco, pp. 1041–1048 Schofield AN, Wroth CP (1968) Critical state soil mechanics. McGraw Hill, London, p 310 Sharma B, Bora KP (2003) Plastic limit, liquid limit and undrained shear strength of soil-reappraisal. J Geotech Geoenv Eng 129(8):774–777 Sivakumar V, Glynn D, Cairns P, Black JA (2009) A new method of measuring plastic limit of fine materials. Geˆotechnique 59(10):813–823
123
Author's personal copy 736 Skempton AW, Northey RD (1953) The sensitivity of clays. Geˆotechnique 3(1):30–53 Skopek J, Ter-stepanian G (1975) Comparison of liquid limit value determined according to Casagrande and Vasilev. Geotechnique 25(1):135–136 Sridharan A, Nagaraj HB (1999) Absorption water content and liquid limit of soils. Geotech Test J 22(2):127–133 Sridharan A, Prakash K (1998) Characteristic water content of a fine-grained soil-water system. Geˆotechnique 48(3):337–346 Sridharan A, Prakash K (1999) Mechanisms controlling the undrained shear strength behaviour of clays. Can Geotech J 36(6):1030–1038 Sridharan A, Prakash K (2000) Percussion and cone methods of determining the liquid limit of soils: controlling mechanisms. Geotech Test J 23(2):236–244 Sridharan A, Venkatappa Rao G (1979) Shear strength behaviour of saturated clays and the role of effective stress concept. Geˆotechnique 29(2):177–193 Sridharan A, Rao SM, Murthy NS (1986) Liquid limit of montmorillonite soils. Geotech Test J 9(3):156–159 Sridharan A, Rao SM, Murthy NS (1988) Liquid limit of kaolinitic soils. Geˆotechnique 38(2):191–198 Sridharan A, Nagaraj HB, Prakash K (1999) Determination of the plasticity index from flow index. Geotech Test J 22(2):175–181 Sridharan A, Nagaraj HB, Prasad S (2000) Liquid limit of soils from equilibrium water content in one-dimensional normal compression. In: Proceedings of the institution of civil engineers geotecholgy engineering, vol 143, pp. 165–169
123
Geotech Geol Eng (2012) 30:727–736 Stone KJL, Phan KD (1995) Cone penetration tests near the plastic limit. Geˆotechnique 45(1):155–158 Towner GD (1973) An examination of the fall cone method for the determination of some strength properties of remoulded agricultural soils. J Soil Sci 24(4):470–479 Trauner L, Dolinar B, Misˇicˇ M (2005) Relationship between the undrained shear strength, water content, and mineralogical properties of fine-grained soils. Int J Geomech 5(4):350–355 Wasti Y, Bezirci MH (1986) Determination of the consistency limits of soils by the fall cone test. Can Geotech J 23(2):241–246 Whyte IL (1982) Soil plasticity and strength: a new approach using extrusion. Ground Eng 15(1):16–24 Wood DM, Wroth CP (1978) The use of the cone penetrometer to determine the plastic limit of soils. Ground Eng 11(3):37 Wroth CP, Wood DM (1978) The correlation of index properties with some basic engineering properties of soils. Can Geotech J 15(2):137–145 Yilmaz I (2000) Evaluation of shear strength of clayey soils by using their liquidity index. Bull Eng Geol Env 59(3):227–229 Yong RN, Warkentin BP (1976) Introduction to soil behaviour. Macmillan, New York, p 96 Youseff MS, El Ramli AH, El Demery M (1965) Relationships between shear strength, consolidation, liquid limit, and plastic limit for remoulded clays. In Proceedings 6th international conference on soil mechanics and foundation engineering, vol 1. Montreal, pp. 126–129 Zreik DA, Germaine JT, Ladd CC (1997) Undrained strength of ultra-weak cohesive soils: relationship between water content and effective stress. Soils Found 37(3):117–128
