Emperical Correlations of Compressibility Of

IGC 2009, Guntur, INDIA Emperical Correlations of Compressibility of Marine Clays—A Review

EMPERICAL CORRELATIONS OF COMPRESSIBILITY OF MARINE CLAYS—A REVIEW

Balla Satyanarayana Research Scholar, Department of Civil Engineering, Andhra University, Visakhapatnam–530 003, India. E-mail: [email protected] C.N.V. Satyanarayana Reddy Professor, Department of Civil Engineering, Andhra University, Visakhapatnam–530 003, India. E-mail: [email protected]

ABSTRACT: The study of engineering behavior, compressibility and strength characteristics of marine clay are gaining importance due to the special problems created to stability and settlement of the structures resting on them as ports and oil exploration platforms. This paper presents a detailed study of consolidation characteristics of Visakhapatnam marine clay. There are different correlations proposed by different researchers for compression index in terms of index properties. The existing empirical correlations of compression index with index properties such as initial void ratio, natural moisture content and liquid limit have been reviewed in the present work and they have been evaluated for validity in soft marine clays using experimental data of marine clays of Visakhapatnam region. It has been observed that the existing empirical correlations failed in reasonable estimation of compression index of marine clays under study. This paper highlights the need for establishing more reliable correlation of compression index to key influencing factors of compressibility.

1. INTRODUCTION change behavior. As a consequence, the soils are bound to exhibit different compressibility behavior even though the Marine clay deposits are encountered in the coastal regions liquid limit is the same (Sridharan A. & Nagaraj H.B. 2000). of the world. Marine clay is soft in consistency and is Several empirical and semi empirical correlations relating characterized by high compressibility and low shear strength. compression index with easily determinable soil index They are fine grained soils with moderate to high clay properties such as initial void ratio, natural moisture content, fraction and are highly plastic in nature. Generally marine plasticity index, clay content, specific gravity etc in addition clay deposits vary from 10 to 30 m in thickness along the to liquid limit were developed based on investigations on coast line. Calcareous material is expected to be present in different soils. The existing empirical correlations based on these soils in the form of small sized shells. The properties of liquid limit (W ), natural moisture content (W ) and initial these deposits are complex and diverse and they mainly depend L n void ratio (e ) are presented in Tables 1–3 respectively. on the minerals present and micro structural arrangement of o the constituent particles. The engineering properties like high compressibility, low shear strength and low permeability of 2. MATERIALS AND METHODS marine clays pose serious challenges to geotechnical engineers The Visakhapatnam marine clay sediments are mostly high in the various construction activities. Compressibility of soils plasticity clays containing small size particles of shells, sand is represented by compression index (CC) which is obtained and organic silt. One dimensional consolidation tests were from the e-log p curve of a consolidation test. Compression conducted on twelve undisturbed marine clay samples collected index is widely used in geotechnical engineering practice for at different depths from different bore holes at HPCL and calculation of settlement of foundations on clayey soils. NTPC locations of Visakhapatnam. The undisturbed clay Compression index is determined by conducting consolidation samples were collected using 100 mm diameter thin walled tests in laboratory on undisturbed samples collected from samplers satisfying the requirements of IS:2132-1986. field. Conducting laboratory consolidation tests are time Atterberg limits, Grain size distribution characteristics and consuming and expensive. Hence compression index values one dimensional consolidation were conducted in accordance based on index properties are generally in use to reduce the with relevant IS Codes of practice IS: 2720 part V-1985, IS: time and expensiveness in a soil investigation program. The 2720 part IV-1985 and IS: 2720 part XV-1986. The collected first well-known correlation of compression index based on soils are classified as CH soils as per IS: 1498–1970. The liquid limit for remoulded clays was presented by Skempton soils were tested in standard fixed ring consolidometers using (1944). Terzaghi & Peck (1967) presented a modified brass rings, 60 mm in diameter and 20 mm high. The inside equation for normally consolidated clays. Soils with the same of the rings was lubricated with silicone grease to minimize liquid limit may have different plastic limits and shrinkage side friction between the ring and the soil specimen. The limits, thereby exhibiting different shrinkage or volume geotechnical properties of clay samples under study are summarized in Tables 4 and 5.

65 Emperical Correlations of Compressibility of Marine Clays—A Review 3. RESULTS with the measured compression indices obtained from the experimental data for Visakhapatnam marine clays collected The predicted compression indices from the existing empirical at HPCL and NTPC locations are given in Tables 6, 7 and 8. equations of compression index based on index properties The percentage errors of compression indices have been determined and the ranges of percentage errors are presented like liquid limit (WL), initial void ratio (eo) and natural water in Table 9. content (Wn) presented by different researchers are compared Table 1: Existing Correlations of Compression Index Based on WL Equation Applicability Reference

CC = 0.007 (wL–10) Remoulded clays Skempton 1944

CC = 0.013 (wL–13.5) All clays Yamagutshi 1959

CC = 0.0046 (wL–9) Brazilian clays Cozzolino 1961

CC = 0.017 (wL–20) All clays Shouka 1964

CC = 0.009 (wL–10) Normally conso-lidated clays Terzaghi and Peck 1967

CC = 0.006 (wL–9) All clays with Azzouz et al. 1976

CC = (wL–13)/109 WL < 100% Mayne 1980

CC = 0.0063 (wL–10) All clays F.M. Abdrabbo & M.A. Mahmoud 1990

Egyptian clays with10%< wL <110% Tsuchida 1991

CC10 = 0.009 (wL–8) Osaka Bay clay Tsuchida 1991

CC10 = 0.009 wL Tokyo Bay clay Shigeyoshi

CC = 0.01wL–0.063 Natural soils (cohesive) Hirata et al. 1990

CC = 0.01 (wL–12) Osaka alluvial clays Murayama et al. 1958

CC = 0.004 (wL–10) Rumoi clay Taniguchi1962

CC = 0.014 (wL–20) Ishikari clay Taniguchi et al. 1960

CC = 0.013 wL Ariake clay Kyushu Branch of JSSMFE1959

Table 2: Existing Correlations of Compression Index Based on Natural Moisture Content (Wn) Equation Applicability Reference

CC = 0.01 (wn–5) All clays Azzouz et al. 1976 CC = 0.01 wn All clays Koppula 1981 CC = 0.01(wn–7.549) All clays Herrero 1983 CC = 0.0115 wn Organic silt and clays Bowles 1989 CC = 0.0066 wn Egyptian clays with 20% < wn < 140% F.M. Abdrabbo and M.A. Mahmoud 1990

Table 3: Existing Correlations of Compression Index Based on Initial Void Ratio (eo) Equation Applicability Reference

CC = 0.54 (e0–0.35) All clays Nishida 1956 CC = 0.29 (e0–0.27) Inorganic clays Hough 1957 CC = 0.35 (e0–0.5) Organic soils Hough 1957 CC = 0.246 + 0.43 (e0–0.25) Motley clays from Sao Paulo, Brazil Cozzolino 1961 CC = 1.21+ 1.055 (e0–1.87) Low lands of Santos, Brazil Cozzolino 1961 CC = 0.50 (e0–0.5) Undisturbed clays Serajuddin 1969 CC = 0.75 (e0–0.5) Soils with low plasticity Sowers 1970 CC = 0.33(e0–0.35) Undisturbed Clays Amin et al. 1987 CC = 0.208e0 + 0.0083 Chicago clays Bowles 1989 CC = 0.156e0 + 0.0107 All clays Bowles 1989 CC = 0.42 (e0–0.5) Egyptian clays with 0.6< e0<2.0 F.M. Abdrabbo and M.A. Mahmoud 1990

66 Emperical Correlations of Compressibility of Marine Clays—A Review Table 4: Properties of Marine Clay at HPCL, Visakhapatnam BH. No. 1 1 2 2 3 4 Depth (m) 5.0 9.0 3.0 7.0 11.0 3.0 Gravel (%) 01 03 01 02 02 01 Sand (%) 12 07 08 13 08 12 Fines (%) 84 88 89 83 89 85 Shells (%) 03 02 02 02 01 02

WL (%) 68 64 65 63 68 62

WP (%) 32 30 32 31 34 31

IP (%) 36 34 33 32 34 31

Wn (%) 64.8 73.4 70.0 74.3 85.2 81.9

GS 2.48 2.54 2.43 2.58 2.40 2.40

eo 1.60 1.89 1.74 1.92 2.06 2.00

CC 0.80 0.80 0.83 0.92 0.94 0.92

Table 5: Properties of Marine Clay at NTPC, Visakhapatnam BH. No. 1 2 3 4 5 6 Depth (m) 1.50 1.50 1.50 3.0 1.50 1.50 Gravel (%) 0 0 0 0 0 01 Sand (%) 04 04 03 06 05 07 Fines (%) 95 96 96 93 94 91 Shells (%) 01 0 01 01 01 01

WL (%) 65 76 71 65 68 61

WP (%) 32 34 34 31 33 30

IP (%) 33 42 37 34 35 31

Wn (%) 70.0 83.6 82.3 71.9 80.7 60.5

GS 2.53 2.57 2.55 2.45 2.40 2.59

eo 1.73 2.32 2.10 1.74 2.06 1.58

CC 0.81 0.97 0.91 0.76 0.92 0.72

67 Emperical Correlations of Compressibility of Marine Clays—A Review

Table 6: Predicted Compression Indices (CC) based on Liquid Limit (WL) for Marine Clay Samples at HPCL and NTPC Locations Location HPCL NTPC

BH. No. 1 1 2 2 3 4 1 2 3 4 5 6

Depth 5.0 9.0 3.0 7.0 11.0 3.0 1.50 1.50 1.50 3.0 1.50 1.50

Liquid limit (WL) 68 64 65 63 68 62 65 76 71 65 68 61

Measured CC 0.80 0.80 0.83 0.92 0.94 0.92 0.81 0.97 0.91 0.76 0.92 0.72

↓ Equation ↓ ↓ Predicted compression indices ↓

CC = 0.007 (wL–10) 0.41 0.38 0.38 0.37 0.41 0.36 0.38 0.46 0.43 0.38 0.41 0.36

CC = 0.013 (wL–13.5) 0.71 0.66 0.67 0.64 0.71 0.63 0.67 0.81 0.75 0.67 0.71 0.62

CC = 0.0046 (wL–9) 0.27 0.25 0.26 0.25 0.27 0.24 0.26 0.31 0.29 0.26 0.27 0.24

CC = 0.017 (wL–20) 0.82 0.75 0.76 0.73 0.82 0.71 0.76 0.95 0.87 0.76 0.82 0.70

CC = 0.009 (wL–10) 0.52 0.49 0.49 0.48 0.52 0.47 0.49 0.59 0.55 0.49 0.52 0.46

CC = 0.006 (wL–9) 0.35 0.33 0.34 0.32 0.35 0.32 0.34 0.40 0.37 0.34 0.35 0.31

CC = (wL–13)/109 0.50 0.47 0.48 0.46 0.50 0.45 0.48 0.58 0.53 0.48 0.50 0.44

CC = 0.0063 (wL–10) 0.36 0.34 0.35 0.33 0.36 0.33 0.35 0.42 0.38 0.35 0.36 0.32

CC10 = 0.009 (wL–8) 0.54 0.50 0.51 0.49 0.54 0.49 0.51 0.61 0.57 0.51 0.54 0.48

CC10 = 0.009 wL 0.61 0.58 0.59 0.57 0.61 0.56 0.59 0.68 0.64 0.59 0.61 0.55

CC = 0.01wL–0.063 0.62 0.58 0.59 0.57 0.62 0.58 0.59 0.70 0.65 0.59 0.62 0.55

CC = 0.01 (wL–12) 0.56 0.52 0.53 0.51 0.56 0.50 0.53 0.64 0.59 0.53 0.56 0.49

CC = 0.004 (wL–10) 0.23 0.22 0.22 0.21 0.23 0.21 0.22 0.26 0.24 0.22 0.23 0.20

CC = 0.014 (wL–20) 0.67 0.62 0.63 0.60 0.67 0.59 0.63 0.78 0.71 0.63 0.67 0.57

CC = 0.013 wL 0.88 0.83 0.85 0.82 0.88 0.81 0.85 0.99 0.92 0.85 0.88 0.79

68 Emperical Correlations of Compressibility of Marine Clays—A Review

Table 7: Predicted Compression Indices (CC) Based on Initial Void Ratio (eo) for Samples at HPCL and NTPC Locations Location HPCL NTPC

BH. No. 1 1 2 2 3 4 1 2 3 4 5 6

Depth 5.0 9.0 3.0 7.0 11.0 3.0 1.50 1.50 1.50 3.0 1.50 1.50

Initial void ratio (eo) 1.60 1.89 1.74 1.92 2.06 2.00 1.73 2.32 2.10 1.74 2.06 1.58

Measured CC 0.80 0.80 0.83 0.92 0.94 0.92 0.81 0.97 0.91 0.76 0.92 0.72

↓ Equation ↓ ↓ Predicted compression indices (CC) ↓

CC = 0.54 (e0–0.35) 0.68 0.90 0.75 0.85 0.93 0.89 0.74 1.06 0.94 0.75 0.92 0.66

CC = 0.29 (e0–0.27) 0.39 0.50 0.43 0.48 0.52 0.50 0.42 0.59 0.53 0.43 0.52 0.38

CC = 0.35 (e0–0.5) 0.39 0.53 0.43 0.50 0.55 0.53 0.43 0.64 0.56 0.43 0.55 0.38

CC = 0.246 + 0.43 (e0–0.25) 0.83 1.00 0.89 0.96 1.03 1.00 0.88 1.14 1.04 0.89 1.02 0.82

CC = 1.21 + 1.055 (e0–1.87) 0.92 1.36 1.07 1.26 1.42 1.35 1.06 1.69 1.45 1.07 1.41 0.90

CC = 0.50 (e0–0.5) 0.55 0.75 0.62 0.71 0.78 0.75 0.61 0.91 0.80 0.62 0.78 0.54

CC = 0.75 (e0–0.5) 0.82 1.13 0.93 1.06 1.18 1.12 0.92 1.37 1.20 0.93 1.17 0.81

CC = 0.33 (e0–0.35) 0.41 0.55 0.46 0.52 0.57 0.49 0.45 0.65 0.58 0.46 0.56 0.41

CC = 0.208 (e0 + 0.0083) 0.34 0.43 0.37 0.41 0.44 0.42 0.37 0.49 0.44 0.37 0.44 0.34

CC = 0.156 (e0 + 0.0107) 0.26 0.32 0.28 0.31 0.33 0.32 0.28 0.37 0.34 0.28 0.33 0.26

CC = 0.42 (e0–0.5) 0.46 0.63 0.52 0.60 0.66 0.63 0.52 0.76 0.67 0.52 0.66 0.45

Table 8: Predicted Compression Indices (CC) based on Wn for Marine Clay Samples at HPCL and NTPC Locations Location HPCL NTPC

BH. No. 1 1 2 2 3 4 1 2 3 4 5 6

Depth 5.0 9.0 3.0 7.0 11.0 3.0 1.50 1.50 1.50 3.0 1.50 1.50

NMC (Wn) 64.8 73.4 70.0 74.3 85.2 81.9 70.0 83.4 82.3 71.9 80.7 60.5

Measured CC 0.80 0.80 0.83 0.92 0.94 0.92 0.81 0.97 0.91 0.76 0.92 0.72

↓ Equation ↓ ↓ Predicted compression indices (CC) ↓

CC = 0.01 (wn–5) 0.60 0.72 0.65 0.69 0.80 0.82 0.65 0.79 0.77 0.67 0.76 0.56

CC = 0.01 wn 0.65 0.77 0.70 0.74 0.85 0.82 0.70 0.84 0.82 0.72 0.81 0.61

CC = 0.01 (wn–7.549) 0.57 0.70 0.62 0.67 0.78 0.74 0.62 0.76 0.75 0.64 0.73 0.53

CC = 0.0115 wn 0.75 0.89 0.81 0.85 0.98 0.94 0.80 0.96 0.95 0.83 0.93 0.70

CC = 0.0066 wn 0.43 0.51 0.46 0.49 0.52 0.54 0.46 0.55 0.54 0.47 0.53 0.40

69 Emperical Correlations of Compressibility of Marine Clays—A Review Table 9: Percentage Errors of Compression Indices Range of percentage error Equation HPCL NTPC

CC = 0.007 (wL–10) 48.8–60.9 50.0–55.4

CC = 0.013 (wL–13.5) 11.3–31.5 11.8–22.8

CC = 0.0046 (wL–9) 66.3–73.9 65.8–70.7

CC = 0.017 (wL–20) –2.5–22.8 –1.3–10.9

CC = 0.009 (wL–10) 35.0–48.9 35.5–49.5

CC = 0.006 (wL–9) 56.3–65.2 55.3–62.0

CC = (wL–13)/109 37.5–51.1 36.8–45.7

CC = 0.0063 (wL–10) 55.0–64.1 53.9–60.9

CC10 = 0.009 (wL–8) 32.5–46.7 32.9–41.3

CC10 = 0.009 wL 23.8–45.7 22.4–33.7

CC = 0.01wL–0.063 22.5–38.0 22.4–32.6

CC = 0.01 (wL–12) 30.0–45.7 30.3–39.1

CC = 0.004 (wL–10) 71.3–77.2 71.1–75.0

CC = 0.014 (wL–20) 16.3–35.9 17.1–27.2

CC = 0.013 wL –10.0–12.0 –11.8–04.3

CC = 0.54 (e0–0.35) –12.5–15.0 –9.3–08.6

CC = 0.29 (e0–0.27) 37.5–51.3 39.2–48.1

CC = 0.35 (e0–0.5) 33.8–51.3 34.0–46.9

CC = 0.246 + 0.43 (e0–0.25) –25.0– –03.8 –17.5– –08.6

CC = 1.21+1.055 (e0–1.87) –70.0– –15.0 –74.2– –25.0 CC = 0.50 (e0–0.5) 06.3–31.3 06.2–25.0 CC = 0.75 (e0–0.5) –41.3– –02.5 –41.2– –12.5 CC = 0.33 (e0–0.35) 31.3–48.8 33.0–44.4 CC = 0.208 (e0+ 0.0083) 46.3–57.5 49.5–54.3 CC = 0.156 (e0+ 0.0107) 60.0–67.5 61.2–65.4 CC = 0.42 (e0–0.5) 21.3–42.5 21.6–37.5 CC = 0.01 (wn–5) 10.0–25.0 11.8–22.2 CC = 0.01 wn 03.8–19.6 05.3–15.3 CC = 0.01 (wn–7.549) 12.5–28.8 15.8–26.4 CC = 0.0115 wn –11.3–07.6 –9.21–02.8 CC = 0.0066 wn 36.3–46.7 38.2–44.4

4. DISCUSSION failed in majority of cases except that given by Nishida From Tables 4 and 5, it can be observed that the Visakhapatnam (1956). The equation resulted in error amounting to undere- marine clay has high natural water content nearly equal to or stimation to the extent of 15 percent. From Table 8, it can be greater than the liquid limit. The empirical correlations observed that only the equation given by Bowles (1989) proposed by different researchers have been used to estimate predicted the values of compression indices within an error compression indices of marine clays under study and are of –11.3 to 7.6 percent whereas all other correlations failed compared with measured compression indices from one badly. As the existing empirical correlations failed in dimensional consolidation tests in Tables 6, 7 and 8. From consistent estimation of compression index values, there is Table 6, it can be seen that the correlation given by Kyushu need for establishing more reliable and scientific correlation Branch of JSSMFE only could yield reasonable values for for compression index incorporating Key compressibility compression indices, with percentage deviation of about 4 to parameters so as to yield the value with higher precision. 12 percent (overestimation). Table 7 reveals that the Compressibility of clays is significantly influenced by the predicted compression indices based on initial void ratio parameters namely, Shrinkage Index, Percent Clay Fraction

70 Emperical Correlations of Compressibility of Marine Clays—A Review and Natural Water Content. Correlation equations with Chai, J.C. et al. (2004). “Compression and Consolidation multiple influencing factors are to be developed instead of Characteristics of Structural Natural Clay”, Can. Geotech. basing on single influencing factor for more reliable prediction J. 41: 1250–1258. of C . c Chu, J. et al. (2002). “Consolidation and Permeability Properties of Singapore Marine Clay”, Jl. of Geotechnical 5. CONCLUSIONS and Geoenvironmental Engineering, Vol. 128, No. 9, Majority of existing empirical correlations of compression 724–732. index based on single influencing factors such as liquid limit, Gil Lim, Yoon et al. (2004). “Empirical Correlations of initial void ratio and natural moisture content are not valid Compression Index for Marine Clay from Regression for marine clays under study as the correlations have resulted Analysis”, Can. Geotech. J. 41: 1213–1221. in under/over estimation of the parameter. Hence, it is Matchala, Suneel et al. (2008). “Compressibility essential that a more reliable correlation is to be made for compression index using multiple influencing parameters of Characteristics of Korean Marine Clay”, Jl. of Marine compressibility such as Shrinkage index, Natural moisture Georesources & Geotechnology, 26:2, 111–127. content, percent Clay size fraction. Relevant IS Codes of Practice. Sridharan, A. and Nagaraj, H.B. (2000). “Compressibility REFERENCES Behaviour of Remoulded, Fine Grained Soils and Correlation with Index Properties”, Can. Geotech J ., 37, Ansary, M.A. (1999). “Compressibility and Permeability 712–722. Characteristics of Selected Coastal Soils of Bangladesh”, Indian Geotechnical Journal, 29(2), 162–185. Sridharan, A. et al. (1992). “Physico-Chemical Effect on Bhat, S.T. et al. (1991). “Geotechnical Properties of Karwar Compressibility of Tropical Soils”, Jl. of Japanese Marine Clay”, Indian Geotechnical Journal, 21(3), 249– Society of Soil Mechanics and Foundation Engineering, 255. Vol. 32, No. 4, 156–163.