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Jayantha Kodikara - Highlights of Research

(1) MPK (Monash-Peradeniya-Kodikara) Framework

The soil compaction is one of the most common activities of civil construction. It is applicable to construction of fills, dams, roads and embankments. The compacted soils can be subjected to various external and environmental loading after construction. The external loading can arise from superstructure loading, moving traffic and overburden soils. The environmental loading can come from the interaction of surficial soils with the atmosphere in forms such as wetting and drying. Under the combination of these loadings, the compacted soils display complex patterns of behaviour such as swelling, collapse, tensile cracking and swelling pressure development against buried non-yielding bodies. The current approaches for predicting the behaviour of compacted soils during subsequent external and environmental loading are, on one hand, are very complex, and on the other hand, are not entirely satisfactory. Professor Kodikara has developed a new framework for predicting the behaviour of compacted soils under these loadings, referred to as MPK (Monash-Peradeniya-Kodikara) Framework (Kodikara, 2012). (Also see MPK Framework)

The MPK framework uses well-known Proctor's (1933) compaction curve as the building block for compacted soil constitutive behaviour for the first time, unravelling valuable information that was hidden all this time.

Reference:

Kodikara, J (2012). New framework for volumetric constitutive behaviour of compacted unsaturated soils, Canadian Geotechnical Journal, 49: 1227-1243 (Selected as Editor's Choice; listed as one of the most read articles in Canadian Geotechnical Journal)

Available to download freely from:
New framework for volumetric constitutive behaviour of compacted unsaturated soils (pdf 2.4MB)

The following images show MPK framework as a plot of void ratio, moisture ratio and pressure (Figure 1)

Kaolin NY MPK curves in compression and tension — Figure 1: Tensile and compressive strength plots using MPK framework for Kaolin NY clay

(2) Measurement and modelling of desiccation and load induced cracking in clay

Soil desiccation cracking can influence many geo-engineering applications, in many cases adversely. For instance, cracking in landfill clayey barriers and covers, embankments and dams, road pavement shoulders, slopes etc are detrimental to their effective function. On the other hand, in some cases, extensive cracking is beneficial, for instance in gaining strength in soft mine tailings. Furthermore, surficial layer of soil, which provides the interface for atmosphere-ground interaction, normally contains desiccation cracks to relieve suction induced lateral stresses. The severity of this cracking can significantly influence how the ground moisture changes depending on the climate. (Also see Cracking in Clay Soils)

Desiccation cracking area (due to soil tension) is normally considered a complex topic in geotechnical engineering, and was less advanced in comparison soil compression behaviour. Professor Kodikara has made significant advances in this topic both in experimental measurement, scientific explanation of desiccation process and analytical modelling.

Some key advances include:

Explanation of the importance of restraints on soil desiccation cracking

Kodikara, J.K., Barbour, S.L. and Fredlund, D.G. (2002). Structure development in surficial heavy clay soils: A synthesis of mechanisms, Australian Geomechanics, Vol. 37, No.3, pp. 25-40.

Introduction of long moulds for testing where parallel cracks would occur and development of analytical explanations.

Nahlawi, H. (2004). Behaviour of reactive soil during desiccation. Masters Thesis, Monash University, Australia.

Nahlawi, H., Kodikara, J.K. (2006). Laboratory experiments on desiccation cracking of thin soil layers. Geotechnical and Geological Engineering 24, 1641-1664.

Kodikara, J.K. and Choi, X. (2006). Simplified analytical model for desiccation cracking of clay layers in laboratory tests, Edited by G. A. Miller, C.E. Zapata, S.L. Houston and D.G. Fredlund, ASCE Geotechnical Special Publication, Unsaturated Soils Vol. 2, pp. 2558-2567.

Amarasiri, A., Kodikara, J. and Costa, S. (2011). Numerical Modelling of Desiccation Cracking, International Journal for Numerical and Analytical Methods in Geomechanics, 35, Issue 1, pp. 82-96.

Figure 3: Long mould desiccation test on Werribee clay

Introduction of Particle Image Velocimetry (PIV) in desiccation cracking tests

Costa, S., Kodikara, J., Thusyanthan, N.I. (2008). Modelling of desiccation crack development in clay soils. In: Proc. 12th International Conference of IACMAG, Goa, India, pp. 1099-1107.

Introduction of the evaluation of J integral in restrained ring test in soil desiccation using PIV

Costa, S. and Kodikara, J. (2012). Evaluation of J-Integral for clay soils using a new ring test, Goetechnical Testing Journal, Vol. 35, No. 6, pp. 1-9.

Figure 4: Ring desiccation test for J integral

Introduction of cohesive crack modelling to desiccation fracture analysis

Amarasiri, A. L., Costa, S. and Kodikara, J. (2011). Determination of cohesive properties of Mode I fracture from compacted clay beams, Canadian Geotechnical Journal, 48, Issue 8, pp. 1163-1173

Amarasiri, A.L. and Kodikara, J.K. (accepted for publication on 5 November 2011, posted ahead of print 8 November 2011). Numerical modelling of desiccation cracking using the cohesive crack method, International Journal of Geomechanics, GM.1943-5622.0000192

Use of desiccation hypothesis in Martian feature interpretation

El Maarry, M.R., Kodikara, J., Wijesooriya, S., Markiewicz, W.J. and Thomas, N. (2012). Desiccation mechanism for formation of giant polygons on earth and intermediate-sized polygons on Mars: Results from a pre-fracture model, Earth Planetary Science Letters, 323-Vol. 324, pp. 19-26.

Introduced the modelling of curling phenomena in desiccating clay

Kodikara, J.K., Nahlawi, H. and Bouazza, A. (2004). Modelling of curling in desiccating clay, Canadian Geotechnical Journal, Vol. 41, pp. 560-566.

Werribee clay soil curling — Figure 5: Clay soil curling

(3) Development of original analytical solutions for tapered piles and introduction of tapered piles in soft rock

Introduced an analytical model for tapered piles using cavity expansion theory.

Kodikara, J.K. and Moore, I.D. (1993). Axial response of tapered piles in cohesive frictional ground, Journal of Geotechnical Engineering, ASCE, Vol. 119, No. 4, pp. 675-693. See A Half Century of Tapered-Pile Usage at the John F. Kennedy Airport (pdf 235KB) (This landmark breakthrough of Tapered-Pile Usage was based on the work of Kodikara and Moore)

Kodikara, J.K., Kong, K.H. and Haque, A. (2006). Numerical modelling of side resistance of tapered piles in mudstone, Geotechnique, Vol. 56, No.7, pp. 505-510.

(4) New equation to represent soil water characteristic (water retention) curve

This equation is different from other currently used equations (such as Van Genucheten, Fredlund and Xing) since it uses physical landmarks (saturated porosity, air entry value, residual water content) directly to represent the SWCC mathematically.

Gould, S., Rajeev, P., Kodikara, J., Zhao, X-L, Burn, S. and Marlow, D. (2012). A new method for developing equations applied to the water retention curve, Soil Science Society of America Journal, Vol.76 No.3, p. 806-814 doi:10.2136/sssaj2011.0260.

(5) Development of a more rational approach to chemical compatible testing

Professor Kodikara (with other researchers) highlighted that both rigid wall and flexible wall permeameters may not correctly simulate the right boundary conditions for chemical compatibility testing.

Kodikara, J.K., Rahman, F. and Barbour, S.L. (2002). Towards a more rational approach to chemical compatibility testing, Canadian Geotechnical Journal, Vol. 39, No. 3, pp. 597-607.

(6) Rock-concrete joint behaviour using direct consideration of joint roughness

Professor Kodikara, during his PhD at Monash 1985 to 1989, participated in pioneering Monash research effort on soft rock technology led by Professor Ian W Johnston (his then supervisor). A particular area of contribution was rock-concrete joint behaviour and its application to side resistance of development of piles socketed in soft rock such as mudstone. This overall effort has led Dr Julian Seidel and Dr Chris Haberfield developing ROCKET computer program for rock-socketed pile design

Figure 7: Direct shear test on rock-concrete joint behaviour

Kodikara, J.K. and Johnston, I.W. (1994). Shear behaviour of irregular triangular rock-concrete joints. International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts, Vol. 31, No. 4, pp. 313-322.

Johnston, I.W., Haberfield, C.M. and Kodikara, J.K. (1993). Predicting the side resistance of piles in soft rock, Proceedings of International Symposium of Hard Soils - Soft Rocks", Athens, Greece, pp. 969-976.

(7) Introduction of log(d)-log(w) method of determination of plastic limit using cone penetrometer

Kodikara, J.K., Seneviratne, H.N. and Wijayakulasooriya, C.V. (1986). Evaluation of plastic limit and plasticity index by cone penetrometer, Proceedings of the Asian Regional Symposium on Geotechnical Problems and Practices in Foundation Engineering., Vol. 1, Colombo, Sri Lanka, pp. 229-233.

This publication introduced, for the first time, the use of log(d)-log(w) method of determination of plastic limit using the laboratory cone penetrometer. However, it did not receive much attention since it was published in a secluded conference. Later the method was used by other researchers to extend it further, as explained in the following Discussion to ASCE.

Kodikara, J.K., Seneviratne, N. and Wijekulasuriya, W., (2006). Discussion on using a small ring and fall-cone to determine the plastic limit by Tao-Wei Wang, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 132, No. 2, pp. 276-278.