Characterisation and modelling of cement treated soil column used as earth retaining structure

CHARACTERIZATION AND MODELING OF CEMENTTREATED SOIL COLUMN USED AS CANTILEVER EARTH RETAINING STRUCTURE SAW AY LEE NATIONAL UNIVERSITY OF SINGAPORE 2014 CHARACTERIZATION AND MODELING OF CEMENTTREATED SOIL COLUMN USED AS CANTILEVER EARTH RETAINING STRUCTURE SAW AY LEE (B. Eng. (Hons.), UTM; M. Sc., NUS) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2014 DECLARATION I hereby declare that the thesis is my original work and it has been written by me in its entirety. I have duly acknowledged all the sources of information which have been used in the thesis. This thesis has also not been submitted for any degree in any university previously. _________________ Saw Ay Lee January 2014 Acknowledgement First of all, I am grateful to The Almighty God for leading me through this research. Without His guidance this dissertation would not have been possible. I would like to express the deepest appreciation to my supervisors, Professor Leung Chun Fai and Associate Professor Tan Siew Ann for their patient guidance, encouragement and useful critiques of this research work. I am extremely blessed by their unconditional support. I also thank the research scholarship as well as facilities provided by the National University of Singapore to make this research a reality. Special thanks to Mr. Ang Beng Oon and Mr. Foo Hee Ann who patiently helped me in my laboratory tasks. I am also grateful to Muhammad Faizal and Dr. Xiao Huawen for their willingness to share the material and equipment during the time I conducted my experimental works. A special thank you is also extended to Mr. Ann Kee Tong and Mr. Edward Lim for their help in offering me the resources. Grateful acknowledgement is expressed to Dr. Namikawa for enlightening me on the tension-softening behavior of cement-treated soil. I would also like to thank the fellow colleagues, in particular Hartono, Kok Shien, Yang Yu, Zongrui, Junhui, Xuguang, Sun Jie, Sandi for their company through this journey. Also, I would like to thank my good friends for their support and continuing belief in me. Last but not the least, an honorable mention goes to my family for always being there for me. i Table of Contents Acknowledgement i Table of Contents …………………………………………………………………………… .ii Summary v List of Tables . vii List of Figures . ix List of Symbols xvii Abbreviations xxi Chapter Introduction 1.1 Background 1.2 Issues Related to the Use of Cement-treated Soil Columns 1.3 Objective and Scope of Study 1.4 Structure of Thesis . Chapter Literature Review 2.1 Introduction . 2.2 General Aspects of Cement-treated Soil 2.2.1 Physical Properties of Cement-Treated Soil 11 2.2.2 Mechanical Properties of Cement-Treated Soil . 13 2.3 Existing design approaches 18 2.4 Numerical Modeling on Behavior of Cement-treated Soil 23 2.4.1 2-D and 3-D Finite Element Analysis 24 2.4.2 Constitutive Models for Cement-treated Soil 26 2.5 Summary 29 Chapter Fracture Behavior of Cement-treated Singapore Marine Clay 3.1 Introduction . 46 3.2 Properties of Base Materials 47 3.2.1 Untreated Marine Clay 47 3.2.2 Ordinary Portland Cement . 48 3.3 Sample Preparation Procedure . 48 3.4 Testing Procedure and Apparatus 50 3.4.1 Uniaxial Compression Test 51 3.4.2 Split Tension Test 51 3.4.3 Three-point Bending Notched Beam Test . 52 3.5 Compressive Fracture Behavior 53 3.6 Tensile Fracture Behavior 55 3.6.1 Split Tensile Strength 56 3.6.2 Fracture Energy, Gf 58 ii 3.6.3 Tension-softening Relationship . 62 3.6.4 Parametric Studies . 67 3.6.5 Outstanding Issues . 70 3.7 Summary 74 Chapter Constitutive Model for Cement-treated Soil 4.1 Introduction . 94 4.2 Finite Element Method 94 4.3 Constitutive Models for Cement-treated Soils . 96 4.3.1 Elastic Perfectly-Plastic Tresca Model 96 4.3.2 Isotropic Model 99 4.3.3 Concrete Damage Plastic Model 100 4.4 Evaluation of Constitutive Model Prediction for Behavior of Cement-treated Toyoura Sand . 105 4.4.1 Drained Triaxial Compression Test by Namikawa (2006) 106 4.4.2 Direct Tension Test by Koseki et al. (2005) 109 4.4.3 Three-point Bending Notched Beam Test by Namikawa (2006) 112 4.5 Evaluation of Constitutive Model Prediction for Behavior of Cement-treated Singapore Marine Clay 116 4.5.1 Uniaxial Compression Test (UCT) 117 4.5.2 Three-point Bending Notched Beam Test . 119 4.6 Conclusions . 121 Chapter Numerical Approaches in Simulating Cemented Soil Mass 5.1 Introduction . 138 5.2 Weighted Average Simulation (WAS) and Real Allocation Simulation (RAS) Approaches 139 5.3 Evaluation of WAS and RAS Approaches in Simulating Cement-treated Soil Mass …………………………………………………………………………………….141 5.3.1 Test description 141 5.3.2 Numerical Analyses . 142 5.3.3 Results and Discussion 147 5.4 Study of Cement-treated Ground Improvement Pattern 151 5.4.1 Hypothetical Cases 153 5.4.2 Numerical Analyses . 155 5.4.3 Results and Discussions . 161 5.5 Conclusion . 167 Chapter Field Studies 6.1 Introduction . 192 iii 6.2 Field Case Study 1: Lateral Load Test by Babasaki et al. (1997) 193 6.2.1 Test Description . 193 6.2.2 Numerical Analyses . 195 6.2.3 Results and Discussions . 198 6.3 Field Case Study 2: Waterway Construction in Northeastern Singapore 201 6.3.1 Characteristics of Site 201 6.3.2 Construction Method . 202 6.3.3 Numerical Analyses . 204 6.3.4 Results and Discussions . 208 6.4 Field Case Study 3: Basement Construction in Central Singapore 210 6.4.1 Characteristics of Site 211 6.4.2 Construction Method . 212 6.4.3 Numerical Analyses . 213 6.4.4 Results and Discussions . 215 6.5 Conclusion . 217 Chapter Conclusions 7.1 Summary of Findings 238 7.2 Recommendations for Further Study . 242 References ………………………………………………………………………… .…….243 iv Summary Owing to presence of soft soil which covers at least one quarter of land area of Singapore, it is often necessary to improve the soft soil for various construction purposes particularly for excavation works. One such ground improvement technique is to improve the soft soil with cement to increase the in-situ strength and stiffness. The treatment may be conducted at great depth as embedded struts to support deep excavation or at shallower depth not far below ground level to support an open excavation work. However, relatively little studies had been performed to study the behavior of cement-treated wall in an open excavation. This research covers experimental studies to investigate behavior of cement-treated marine clay and numerical studies to examine the behavior of cement-treated soil columns used as a retaining system in an open cut excavation. The first objective of this study is to understand the material properties of cement-treated Singapore marine clay in terms of compression and tension behavior. A series of samples with different mix proportions and curing periods was tested by different means in the laboratory. The experimental results show that the material strength increases rapidly to a peak value and then decreases abruptly to a small value upon further straining. The tensile strength of this material is found to be 11% of its unconfined compressive strength in the cement content tested in the present study. This material becomes brittle when 20% of cement content is added and cured for 14 days. The post-peak softening of the treated clay was derived based on fracture mechanics concept. Numerical calibration analyses were carried out to evaluate the appropriateness of three available constitutive models based on laboratory test results and published data. The calibration results show that the concrete damage plasticity (CDP) model is superior to Tresca and isotropic models in simulating the behaviors of cement-treated soil in compression, tension and bending. v This thesis further examines the significance of modeling the cement-treated soil column configurations in finite element analysis. This is of importance to account for the localized overlap areas of treated soil columns and the interaction between treated and untreated soil. In practice, cement-treated soil mass with certain columnar shaped treated soil are often analyzed using weighted average simulation (WAS) approach with properties that are averaged over the treated area. In this thesis, the limitations of generalizing the properties based on comparison with the results of a published laboratory test were discussed. The analysis results show that the shortcomings of this approach can be overcome by the real allocation simulation (RAS) approach with CDP model. The established numerical approach was then adopted to study hypothetical cases of a vertical cut with three different ground improvement geometrical patterns. The study demonstrates that tensile damage in the cement-treated soil columns is the trigger for failure. The ability of this recommended numerical simulation method – RAS with CDP model is examined by back-analyzing three field case studies on cement-treated soil columns failure. The numerical approach provides a fair prediction of the ground response and failure pattern compared to field observations. vi List of Tables Table 2.1 Summary of selected E-qu relationships for cement-treated clay. Table 2.2 Summary of some Table 3.1 Basic properties of Singapore marine clay from Marine Bouvelard site. Table 3.2 Chemical composition and physical properties of Ordinary Portland Cement t – qu relationships of cemented soil. provided by supplier. Table 3.3 Mixture proportions and tests conducted for cement-treated Singapore marine clay in the present study. Table 3.4 Summary of fracture energies, Gf from BNT tests. Table 3.5 Nominal size for materials used in the present study. Table 3.6 Mixture proportions and experimental tests with addition of filter sand in clay. Table 3.7 Chemical compositions of filter sand provided by supplier. Table 3.8 Summary fracture energy Gf for cemented clay and cemented clay+sand. Table 4.1 Mixing proportions of cement-treated Toyoura sand. Table 4.2 Design parameters for Tresca model. Table 4.3 Design parameters for Isotropic model. Table 4.4 Design parameters for CDP model. Table 4.5 Summary results of three-point bending notched beam test by Namikawa (2006). Table 4.6 Tensile design parameters for CDP model in Case T2. Table 4.7 Mixing proportions of cement-treated Singapore marine clay. Table 4.8 Calibration parameters for cemented Singapore marine clay using CDP model. Table 4.9 Damage variables used in CDP model for cemented Singapore marine clay Test B1. Table 5.1 Tresca design parameters for WAS approach in Test 2. Table 5.2 CDP design parameters of lime-cement-treated soil columns for RAS approach in Test 2. Table 5.3 CDP damage variables for lime-cement-treated soil columns in Test 2. Table 5.4 Summary table of hypothetical cases. Table 5.5 Design parameters for Mohr Coulomb and Tresca models in hypothetical cases. Table 5.6 CDP model design parameters for cement-treated soil columns used in hypothetical cases. Table 5.7 CDP model damage variables for cement-treated soil columns used in hypothetical cases. Table 6.1 Model parameters for steel plate, concrete cap and untreated soil (reproduced from Namikawa et al., 2008). vii Chapter Conclusions 7.1 Summary of Findings The studies presented in preceding chapters aim to provide a better understanding of the behavior of cement-treated soil columns used as earth retaining structure in an open excavation. The findings of this study are summarized as follows. 1) Through experiments, the behaviors of cement-treated Singapore marine clay are established as follows. a) The compressive strength increases rapidly up to the peak value and then decreases abruptly to a small value upon further straining. At cement content = 20% with 14 days curing period, the treated material manifests brittle behavior with shear and cone failure observed in the test sample. The strength associated with brittleness increases with cement content and curing period. For higher cement content and longer curing period, vertical compressive crushing is dominant and columnar fracture is observed. b) Tensile strength is measured by split tension test which can be well correlated with the unconfined compressive strength as st = 0.11qu for the cement content tested in the present study. The tensile post-peak behavior is presented by a relation between stress and fracture zone deformation. Three-point bending notched beam test was employed to derive the tension-softening relation based on fracture mechanics concept. For the mix proportion used in the present study, Gf falls within a range of 2.6 N/m to 4.4 N/m. A bilinear relation is observed in the tensile stress-crack opening displacement relationship, but the relation becomes linear when the material brittleness increases. 2) The use of three-point bending notched beam test to study the tension-softening relation of cement-treated clay is a relatively new approach although it has been widely used in concrete and cement-treated sand by Namikawa (2006). Therefore, parametric studies 238 were conducted to evaluate the influences of test parameters, i.e. notch width and sample size. Test results show that there is no difference between notch width 0.7 mm and 2.5 mm due to a uniform particle size distribution around the notch tip. On the other hand, there is also no difference in the test results for 50 mm and 40 mm sample sizes. The 10 mm difference in size is insignificant compared to the overall stress transition zone which usually involved hundreds of mm according to literatures. The stability problem in the tests is closely related to the stiffness of the testing machine comparing to the brittleness of the cement-treated clay. It is observed that the stability problem is more pronounced for a more brittle specimen. 3) The comparison between Tresca, isotropic and concrete damage plasticity (CDP) models based on calibration of laboratory tests in the present study and published data shows that the third model is far superior to others in simulating the behavior of cement-treated soil: a) Classical Tresca model assumes single stiffness and perfectly-plastic failure so it cannot capture the strain hardening and softening behaviors of cement-treated soil. Although the model can be improved with a built-in tension cutoff function to limit the tensile strength, it is still incapable of modeling the strain softening part. b) Isotropic model predicts close to the uniaxial compression test measurements but not the tension failure as the yield criterion in this model allows the development of any value of tensile stress. c) In CDP model, the user-input uniaxial stress-strain relations can be employed to determine the current state of the yield surface to analyze multiaxial load cases. As a result, this model can well capture the hardening and softening behaviors of cementtreated clay and sand. The model assumes a linear loss of strength after initial cracking which is fitted well to the behavior of cement-treated clay observed in the present study. Moreover, the post-failure stress can also be defined as a tabled function of crack displacement which is demonstrated to predict the bilinear relation of cement-treated Toyoura sand well. 239 4) When weighted average simulation (WAS) approach is employed to model the cementtreated soil columns used in an open excavation, several errors can occur. These errors are identified with real allocation simulation (RAS) approach using CDP model with comparisons made to laboratory test and field cases. a) Homogenizing the mass properties only allows for a single constitutive model thus violates the underlying mechanism for treated soil and untreated soil with very different characteristics. It is shown in this study that the commonly used Tresca model fails to capture the tensile damage developed in the cement-treated soil columns as shear failure of the treated mass is predicted. b) The front columns that form along the intended line of proposed excavation are subjected to lateral load and results in a “pulling away action” at overlap areas between front columns and other tangential columns. Cracks initiate when the induced tensile stress exceeds the capacity. Therefore, regarding the treated mass as a composite material will not allow failure to happen within the mass is incorrect. c) Perfect bonding between treated soil and untreated soil assumed in WAS approach is not appropriate as the analysis result shows that untreated soil moves relatively apart from the cement-treated soil columns. 5) Hypothetical studies of a vertical cut improved by three types of ground improvement geometrical patterns (namely Grid, Tangential buttress and Double wall) show that the vulnerable part of this retaining system is the front row columns. The rear parallel row columns in Grid pattern not contribute much resistance for the retaining system. A thicker front wall (i.e. double-overlapping rows or bigger diameter of cement-treated soil column) is more effective than other ground improvement geometrical patterns as the cracks consume more energy to propagate through a longer path to cause failure. This finding is not possible to be observed in the WAS approach as it does not take the column configuration into consideration. 240 6) Back-analyses of field case studies confirmed that tensile damage is the trigger for failure initiation of cement-treated soil columns used as retaining structure in an open excavation. The horizontal tensile crack positions that appear in the front columns depend on the cantilever span and may also appear at the middle span or at the excavation level. Addition of steel members in the cement-treated soil column will shift the horizontal tensile crack positions. Nevertheless, the contribution of the steel member to the retaining wall performance highly depends on the member size. 7) The damage patterns obtained by the proposed numerical method, RAS approach with CDP model are generally consistent with the trend observed from field case studies. In this proposed numerical method, each individual treated soil column is modeled individually with assigned properties described by CDP model. CDP model captures the tensionsoftening behavior to provide a realistic simulation of failure response of cement-treated soil columns. It shows in detail the propagation of correct damage locations, stress distribution and the interaction mechanism of cement-treated soil columns and untreated soil. This is significantly meaningful as it provides a fundamentally concept for the analysis of cement-treated soil columns used as earth retaining system in an open excavation. 8) There are some design implications that can be learnt from the present study. For retaining structure with cement-treated soil columns in certain configuration, the weakest part is at the overlap area between front row columns and others. This can be improved by constructing a capping beam overtop the columns to tie them together as recommended by VERT. However, for long span cantilever front row columns, tensile crack may occur at the cantilever span. This can be overcome with a sizable column diameter to resist the induced stresses which is superior to other column configurations design. Reinforcing the front row columns with steel beam members is only effective when a considerable member size is embedded in every column. 241 7.2 Recommendations for Further Study This research studies several fundamental characterizations of cement-treated soil columns used as earth retaining structure in an open excavation. However, some improvements can be done as follows: (a) The knowledge gained from the laboratory work in this study paves the way for further development of an established laboratory test guidelines in determining the tensionsoftening relation of cement-treated clay. The currently adopted test guideline of threepoint bending notched beam test is based on RILEM’s recommendation for concrete. Although concrete and cement-treated clay both behave as quasi-brittle materials; the particle size, strength and brittleness are quite different from each other. Therefore, it would be of interest to conduct a detailed study of laboratory test guidelines in determining the tension-softening relation of cement-treated clay. (b) Since CDP model is proven to be an appropriate constitutive model in simulating the behavior of cement-treated soil, the yielding parameters can thus be studied. So far, the relevant parameters used in the present study are inferred from concrete test data. (c) To better reflect the actual cement-treated soil columns and ground performance in finite element analysis, it is recommended that the excavation be modelled in its proper sequences. (d) In view that cement-treated soil is so brittle and failure would occur very suddenly, it would be of interest to study any measurement (e.g. addition of fiber to increase ductility of the final mixture product or insertion of a comparatively large size of steel member in the cement-treated soil column) that can prevent the collapse failure as reported in field case studies and 3. 242 REFERENCES Abaqus 6.11, A. (2011). Online manual, SIMULIA. Providence, RI, USA. Adams, T. E. (2011) Stability of levees and fllodwalls supported by deep-mixed shear walls. Virgina Polytechnic Institute and State University. Andromalos, K., Hegazy, Y. and Jasperse, B. (2001). "Stabilization of soft soils by soil mixing." Soft Ground Technology,194-205. Antão, A. N., Guerra, N. M., Cardoso, A. S. and Fernandes, M. M. (2007). "Earth pressures of soils in undrained conditions. Application to the stability of flexible retaining walls." 5th International Workshop Applications of Computational Mechanics in Geotechnical Engineering, Portugal,247-256. Arroyo, M., Ciantia, M., Castellanza, R., Gens, A. and Nova, R. (2012). "Simulation of cementimproved clay structures with a bonded elasto-plastic model: A practical approach." Computers and Geotechnics, 45, 140-150. Assarson, K., Broms, B., Granhom, S. and Paus, K. (1974). Deep Stabilization of Soft Cohesive Soils. Sweden, Linden Alimark. Babasaki, R., Suzuki, Y., Nakama, T. and Yamada, K. (1997). "Study for reinforced earth retaining wall by deep mixing method." Proceeding 32th Annual Conference of Japanese Geotechnical Society,1733-1734. Babasaki, R., Terashi, M., Suzuki, T., Maekawa, A., Kawamura, M. and Fukazawa, E. (1996). "Factors influencing the strength of improved soils."JGS Technical Committee Report. Baratta, F. I. and Underwood, J. H. (1992). "Notch dimensions for three-point bend fracture specimens based on compliance analyses."ARL-TR-35, U.S. Army Research Laboratory Bazant, Z. and Kazemi, M. (1991). "Size dependence on concrete fracture determined by rilem workof-fracture method." International Journal of Fracture, 51, 121-128. Brinkgreve, R. B. J. (2005). "Selection of soil models and parameters for geotechnical engineering application." Geotechnical Special Publication, ASCE, 128, 69-98. Broderic, G. P. and Daniel, D. E. (1990). "Stabilizing compacted clays againts chemical attack." Journal of Geotechnical Engineering, 116(10), 1549-1567. Broms, B. B. (2004). Lime and lime/cement columns. Ground Improvement 2nd edition. M. P. M. a. K. Kirsch, Spon Press: 252-330. Broms, B. B. and Boman, P. (1979). "Stabilization of soil with lime columns." Ground Engineering, 12(4), 23-32. 243 CDIT (2002). The Deep Mixing Method:Principle, Design and Construction. The Netherlands, A.A. Balkema. Center, P. W. R. (1999). Deep mixing method design and execution manual for land works, 92-99. Charbit, B. (2009) Numerical analysis of laterally loaded lime/cement columns. MSc, KTH Royal Institute of Technology. Chen, J., Lee, F. H. and Ng, C. C. (2011). "Statistical analysis for strength variation of deep mixing columns in Singapore." Geo-Frontiers, Dallas, TX,576-584. Chen, W. F. and Mizuno, E. (1990). Nonlinear analysis in soil mechanics, theory and implementation, Elsevier. Cherepanov, G. P. (1967). "The propagation of cracks in a continuous medium." Journal of Applied Mathematcis and Mechancis, 31(3), 503-512. Chew, S. H., Lee, F. H. and Lee, Y. (1997). "Jet Grouting in Singapore Marine Clay." Proc. 3rd Asian Young Geotechnical Engineers Conference, Singapore,231-238. Chin, K. G. (2006) Constitutive behavior of cement treated marine clay. Ph.D, National University of Singapore. Chong, P. T. (2002) Characterisation of Singapore Lower Marine Clay. Ph.D, National University of Singapore. Chuah, S. S. and Tan, S. A. (2010). "Numerical study on a new strut-free counterfort embedded wall in Singapore." Earth Retention Conference 3, Bellevue, Washington, US,740-747. Clough, G. W., Sitar, N., Bachus, R. C. and Rad, N. S. (1981). "Gemented sands under static loading." Journal of Geotechnical Engineering Divison, 107(6), 799-817. Consoli, N. C., Schnaid, F., Rohlfes Junior, J. A. and Preitto, P. D. M. (1996). "Engineering properties of residual soil-cement mixtures." Grouting and Deep mixing, The Second International Conference on Ground Improvement Geosystems, Tokyo,25-30. Das, B. M. and Dass, R. N. (1995). "Lightly cemented sand in tension and compression." Geotechnical and Geological Engineering, 13, 169-177. Dawson, E. M., Roth, W. H. and Drescher, A. (1999). "Slope stability analysis by strength reduction." Geotechnique, 49(6), 835-840. Diamond, S. and Kinter, E. B. (1965). "Mechanisms of soil-lime stabilization: an interpretive review. Highway Research Record." 92, 83-102. 244 Fang, T. S. and Yu, F. J. (1998). "Engineering properties of jet-grouted soilcrete and slime." 2nd International Conference on Ground Improvement Techniques, Singapore,589-596. Fang, Y. S., Liao, J. J. and Lin, T. K. (1994). "Mechanical properties of jet grouted soilcrete." Quarterly Journal of Engineering Geological, 27(3), 257-265. Frocht, M. M. (1948). Photoelasticity. New York, John Wiley. Gaba, A. R. (1990). "Jet grouting at newton station, Singapore." Tenth Southeast Asian Geotechnical Conference, Taipei,77-79. Goh, T. L. (2003) Stabilisation of an embedded improved soil berm. Ph.D, National University of Singapore. Goto, S., Tatsuoka, F., Shibuya, S., Kim, Y. S. and Sato, T. (1991). "A simple gauge for local small strain measurements in the laboratory." Soils and Foundations, 31(1), 169-180. Griffiths, D. V. and Lane, P. A. (1999). "Slope stability analysis by finite elements." Geotechnique, 49(3), 387-403. Haque, M. A. and Bryant, J. T. (2011). "Failure of VERT wall system: forensic evaluation and lessons learned." Geo-Frontiers 2011: Advances in Geotechnical Engineering, Dallas, Texas, US Hashizume, H., Okochi, Y., Dong, J., Horii, N., Toyosawa, Y. and Tamate, S. (1998). "Study on the behavior of soft ground improved using deep mixing method." Proc. of the International Conference on Centrifuge 98, 851-856. Heilmann, H. G., Hilsdorf, H. H. and Finsterwalder, K. (1969). "Festigkeit und Verformung von Beton unter Zugspannungen." Deutscher Ausschuss fur Stahlbeton, (Heft 203 (in German)). Hillerborg, A. (1985). "The theoretical basis of a method to determine the fracture energy GF of concrete." Materials and Structures, 18, 291-296. Hillerborg, A. (1989). "Stability problems in fracture mechanics testing." International Conference on Recent Developments in the Fracture of Concrete and Rock, University of Wales, UK,369-378. Hillerborg, A., Modeer, M. and Petersson, P.-E. (1976). "Analysis of crack formation and crack growth in concrete by means of fracture mechanics and finite elements." Cement and Concrete Research, 6, 773-782. Horpibulsuk, S., Liu, M. D., Liyanapathirana, D. S. and Suebsuk, J. (2010). "Behaviour of cemented clay simulated via the theoretical framework of the structured cam clay model." Computers and Geotechnics, 37(1), 1-9. Hosoya, Y., Ogino, T., Nasu, T., Kohata, Y., Hibi, Y. and Makihara, Y. (1997). "JGS TC Report: An evaluation of the strength of soils improved by DMM." Grouting and Deep mixing, The Second International Conference on Ground Improvement Geosystems, Tokyo,919-924. 245 Hsi, J. P. and Yu, J. B. Y. (2005). "Jet grout application for excavation in soft marine clay." Proceedings of the 16th International Conference on Soil Mechanics and Geotechnical Engineering, Osaka, Balkema,1485-1488. Hsieh, H. S., Wang, C. C. and Ou, C. Y. (2003). "Use of Jet Grouting to Limit Diaphragm Wall Displacement of a Deep Excavation." Journal of Geotechnical and Geoenviromental Engineering, 129, 146-157. Hwang, R. N. and Moh, Z. C. (2008). "Evaluating effectiveness of buttresses and cross walls by reference envelopes." Journal of GeoEngineering, 3(1), 1-11. Issa, M. A., Issa, M. A., Islam, M. S. and Chudnovsky, A. (2000b). "Size effects in concrete fracture Part II: Analysis of test results." International Journal of Fracture, 102(1), 25-42. Jankowiak, I., Kakol., W. and Madaj, A. (2005). "Identification of a continuous composite beam numerical model, based on experimental tests." 7th Conference on Composite Structures, Zielona Gora,163-178. Jardine, R. J., Symes, N. J. and Burland, J. B. (1984). "The measurement of soil stiffness in triaxial apparatus." Geotechnique, 34(3), 323-340. Josephine, V. C. (2011) Material modelling of reinforced concrete at evelated temperatures. MSc, Technical University of Denmark. Kamruzzaman, A. H. M. (2002) Physico-chemical and engineering behaviour of cement treated Singapore marine clay. Ph.D, National University of Singapore. Karastanev., D., Kitazume, M., Miyajima, S. and Ikeda, T. (1997). "Bearing capacity of shallow foundation on column type DMM improved ground." Proc. of the 14th International Conference on Soil Mechanics and Foundations Engineering, 3, 1621-1624. Kasama, K., Ochiai, H. and Yasufuku, N. (2000). "On the stress-strain behaviour of lightly cemented clay based on an extended critical state concept." Soils and Foundations, 40(5), 37-47. Kawasaki, T., Niina, A., Saitoh, S. and Babasaki, R. (1978). Takenaka Technical Research Report. Studies on engineering characteristics of cement-base stabilized soil. 19: 144-165. Kawasaki, T., Niina, A., Saitoh, S., Suzuki, Y. and Honjyo, Y. (1981a). "Deep mixing method using cement hardening agent." Proceedings of the 10th International Conference on Soil Mechanics and Foundation Engineering, Stockholm,721-724. Khoo, K. S., Orihara, K., Egi, F., Arii, T. and Yamamoto, K. (1997). "Excavation with soil berm improved by jet grout piles." Proceedings of 3YGEC, Singapore,189-196. Kitazume, M. (2008). "Stability of ground column type DM improved ground under embankment loading behavior of sheet pile quay wall."Report of the Port and Airport Research Institute. Nagase, Yokosuka, Japan, Port and Airport Research Institute 246 Kitazume, M., Ikeda, T., Miyajima, S. and Karastanev., D. (1996). "Bearing capacity of improved ground with column type DMM." Proc. of the 2nd International Conference on Ground Improvement Geosystems, 1, 503-508. Kitazume, M. and Maruyama, K. (2007). "Internal stability of group column type deep mixing improved ground under embankment loading." Soils and Foundations, 47(3), 437-455. Kitazume, M., Okano, K. and Miyajima, S. (2000). "Centrifuge model tests on failure envelope of column type deep mixing method improved ground." Soils and Foundations, 40(4), 43-55. Kivelo, M. (1998) Stabilization of embankments on soft soil with lime/cement columns. Ph.D, Royal Institute of Technology. Kmiecik, P. and Kaminski, M. (2011). "Modelling of reinforced concrete structures and composite structures with concrete strength degradation taken into consideration." Archives of Civil and Mechanical Engineering, 11(3), 623-636. Kohata, Y., Muramoto, K., Maekawa, H., Yajima, J. and Babasaki, R. (1997). "JGS TC Report: Deformation and strength properties of DM cement-treated soils." Grouting and Deep mixing, The Second International Conference on Ground Improvement Geosystems, Tokyo,905-911. Koseki, J., Sato, T. and Nishimoto, T. (2005). "Anisotropy in strength characteristics of cement-treated sand prepared by compaction." Proc. Symp. Cement-treated Soils, JGS,365-368. Kupfer, H., Hilsdorf, H. K. and Rusch, H. (1969). "Behavior of concrete under biaxial stresses." ACI Journal, 66(8), 656-666. Larsson, S. (1999). "Shear box apparatus for modeling chemical stabilized soil - Introductory tests." Proceedings of the International Conference on Deep Mixing, Best Practice and Recent Advances, Stockholm,732-785. Larsson, S., Dahlstrom, M. and Nilsson, B. (2005a). "Uniformity of lime-cement columns for deep mixing: a field study." Ground Improvement, 9(1), 1-15. Larsson, S., Dahlstrom, M. and Nilsson, B. (2005b). "A complementary field study on the uniformity of lime-cement columns for deep mixing." Ground Improvement, 9(2), 67-77. Larsson, S., Malm, R., Charbit, B. and Ansell, A. (2012). "Finite element modelling of laterally loaded lime-cement columns using a damage plasticity model." Computers and Geotechnics, 44, 48-57. Lee, F. H. (2008). "How useful is numerical analysis in geotechnical engineering?" International Conference on Deep Excavations (ICDE), Singapore Lee, F. H., Lee, Y., Chew, S. H. and Yong, K. Y. (2005). "Strength and modulus of marine claycement mixes." Journal of Geotechnical and Geoenviromental Engineering, 131(2), 178-186. 247 Lee, J. and Fenves, G. L. (1998). "Plastic-damage model for cyclic loading of concrete structures." Journal of Engineering Mechanics, 124(8), 892-900. Lee, K. H., Chan, D. and Lam, K. C. (2004). "Consitutive model for cement treated clay in a critical state frame work." Soils and Foundations, 44(3), 69-77. Lee, Y., Yogarajah, I. and Lee, F. H. (1998). "Engineering properties of grouted Marine Clay." 2nd International Conference on Ground Improvement Techniques, Singapore,267-275. Li, V. C., Chan, C.-M. and Leung, C. K. Y. (1987). "Experimental determination of the tensionsoftening relations for cementitious composites." Cement and Concrete Research, 17, 441-452. Li, V. C. and Ward, R. J. (1989). "A novel testing technique for post-peak tensile behavior of cementitious materials." Fracture Toughness and Fracture Energy,183-195. Liao, H. J. and Tsai, T. L. (1993). "Passive resistance of partially improved soft clayey soil." 11th Southeast Asian Geotechnical Conference, Singapore,751-756. Liu, M. D. and Carter, J. P. (2002). "A structured cam clay model." Canadian Geotechnical Journal, 39, 1313-1332. Lorenzo, G. A. and Bergado, D. T. (2006). "Fundamental characteristics of cement-admixed clay in deep mixing." Journal of Material in Civil Engineering ASCE, 18(2), 161-174. Low, H. E. (2004) Compressibility and Undrained Behavior of Natural Singapore Marine Clay: Effect of Soil Structure. M.Eng, National University of Singapore. Lubliner, J., Oliver, J., Oller, S. and Onate, E. (1989). "A plastic-damage model for concrete." International Journal of Solids and Structures, 229-326. Matsui, T. and San, K. C. (1992). "Finite element slope stability analysis by shear strength reduction technique." Soils and Foundations, 32(1), 59-70. Miyake, M., Akamoto, H. and Wada, M. (1991). "Deformation characteristics of ground improved by a group of treated soil." Proc. of the International Conference on Centrifuge 91, 295-302. Morley, A. (1944). Strength of materials. London, Longman. Namikawa, T. (2006) Study on tensile and shear failure characteristics of cement-treated sand. Ph.D, University of Tokyo. Namikawa, T. and Koseki, J. (2006). "Experimental determination of softening relations for cementtreated sand." Soils and Foundations, 46(4), 491-504. Namikawa, T. and Koseki, J. (2007). "Evaluation of tensile strength of cement-treated sand based on several types of laboratory tests." Soils and Foundations, 47(4), 657-674. 248 Namikawa, T., Koseki, J. and Suzuki, Y. (2008). "Finite element analysis of a full scale bending test of cement treated soil column." The 12th International Conference of IACMAG, Goa, India,3635-3641. Namikawa, T. and Mihira, S. (2007). "Elasto-plastic model for cement-treated sand." International Journal for Numerical and Analytical Methods in Geomechanics, 31, 71-107. Navin, M. P. (2005) Stability of Embankments Founded on Soft Soil Improved with Deep-MixingMethod Columns. Ph.D, Virginia Polytechnic Institute and State University. Nayak, G. C. and Zienkiewicz, O. C. (1972). "Convenient form of stress invariants for plasticity." Journal of the Structural Division. ASCE, 98, 949-954. Ni, Q. (2005) Engineering Properties of Singapore Old Alluvium. Ph.D, National University of Singapore. Nicholson, P. J., Mitchell, J. K., Bahner, E. W. and Moriwaki, Y. (1998). "Design of a soil mixed composite gravity wall." Soil Improvement for Big Digs, Geotechnical Special Publication, ASCE, Boston, ASCE,27-40. Niwa, J., Sumranwanich, T. and Tangtermsirikul, S. (1998b). "New method to determine tension softening curve of concrete." Proceedings FRAMCOS-3, 347-356. O'Rourke, T. D. and O'Donnell, C. J. (1997). "Field behavior of excavation stabilized by deep soil mixing." Journal of Geotehnical and Geoenvironmental Engineering, 123(6), 516-524. Omine, K., Ochiai, H. and Bolton, M. D. (1999). "Homogenization method for numerical analysis of improved ground with cement-treated soil columns." Proceedings of International Conference on Dry Mix Methods for Deep Soil Stabilization, Stockholm, Balkema,161-168. Ou, C. Y. and Wu, T. S. (1996). "Evaluation of material properties for soil improvement in excavation." Grouting and Deep Mixing, Rotterdam,545-550. Ou, C. Y., Wu, T. S. and Hsieh, H. S. (1996). "Analysis of deep excavation with column type of ground improvement in soft clay." Journal of Geotechnical Engineering, 122(9), 709-716. Pankaj, P. (1990) Finite element analysis in strain softening and localisation problems. Ph.D, University of Roorkee. Petersson, P.-E. (1981). "Crack growth and development of fracture zones in plain concrete and similar materials."Report TVBM-1006. Division of Building Materials, Lund Institute of Technology, Lund, Sweden Pitts, J. (1992). Landforms and Geomorphic Evolution of the Islands during the Quaternary. Singapore, Singapore University Press. 249 Porbaha, A., Shibuya, S. and Kishida, T. (2000). "State of the art in deep mixing technology. Part III: geomaterial characterization." Ground Improvement, 4(3), 91-110. Racansky, V., Schweiger, H. F. and Thurner, R. (2008). "FE-Analysis of the Behaviour of Buttressed Jet Grouted Retaining Walls." The 12th International Conference of IACMAG, India,3984-3992. Rice, J. R. (1968). "A path independent integral and the approximate analysis of strain concentration by notches and cracks." journal of Applied Mechanics, 35, 379-386. RILEM (1985). "Determination of the fracture energy of mortar and concrete by means of three-point bend tests on notched beams." Materials and Structures, 18, 285-290. Rocco, C., Guinea, G. V., Planas, J. and Elices, M. (1999). "Mechanisms of rupture in splitting tests." ACI Material Journal, 96(1), 52-60. Rokugo, K., Iwasa, M., Seko, S. and Koyanagi, W. (1989). "Tension softening diagrams of steel fiber reinforced concrete." Fracture of Concrete and Rock,513-522. Ruffing, D. G., Sheleheda, M. J. and Schindler, R. M. (2012). "A case study: unreinforced soil mixing for excavation support and bearing capacity improvement." Grouting and deep mixing: 4th International Conference on Grouting and Deep Mixing, New Orleans, LA Rusinowski, P. (2005) Two-way concrete slabs with openings: experiments, finite element analysis and design. Msc, Lulea University of Technology. Ryan, C. R. and Jasperse, B. H. (1989). "Deep soil mixing at the Jackson lake dam." ASCE Geotechnical and Construction Divisions Special Conference Saitoh, S., Kawasaki, T., Nina, S., Babasaki, R. and Miyata, T. (1980). "Research on DMM using cementitious agents (part 10) - engineering properties of treated soils." Proc. of the 15th National Conference of the JSSMFE, 717-720 (in Japanese). Saitoh, S., Suzuki, Y., Nishioka, S. and Okumura, R. (1996). Required strength of cement improved ground, Balkema. SGF (2000). "Lime and lime cement columns."Guide for design, construction and control. Report 2:2000, Linkoping, Swedish Geotechnical Society.(Swedish) Shen, S. L. (1998) Behaviour of deep mixing columns in soft clay ground. Ph.D, Saga University. Shibuya, S., Tatsuoka, F., Teachavorasinskun, S., J., K. X., Abe, F., Kim, Y. S. and Park, C. S. (1992). "Elastic deformation properties of geomaterials." Soils and Foundations, 32(3), 26-46. Shirlaw, J. N., Tan, T. S. and Wong, K. S. (2005). "Deep excavations in Singapore Marine Clay." Geotechnical Aspects of Underground Construction in Soft Ground, Proceedings of the 5th International Symposium TC28, Amsterdam, the Netherlands,13-28. 250 Snitbhan, N. and Chen, W. F. (1978). "Elastic-plastic large deformation analysis of soil slopes." Computers and Structures, 9, 567-577. Suzuki, K., Nichikawa, T., Hayashi, J. and Ito, S. (1981). "Approach by zeta potential on the surface change of hydration of C3S." Cement and Concrete Research, 11, 759-764. Swan, C. C. and Seo, Y. K. (1999). "Limit state analysis of earthen slopes using dual continuum/FEM approaches." International Journal for Numerical and Analytical Methods in Geomechanics, 23, 13591371. Tan, S. L. (1983). "Geotechnical properties and laboratory testing of soft soils in Singapore." Proc. 1st Int. Seminar on Construction Problems in Soft Soils, Singapore,TSL1-47. Tan, T. S., Goh, T. L. and Yong, K. Y. (2002). "Properties of Singapore marine clays improved by cement mixing." Geotechnical Testing Journal, 25(4), 1-12. Tan, T. S., Phoon, K. K., Lee, F. H., Tanaka, H., Locat, J. and Chong, P. T. (2003). "A characterisation study of Singapore Lower Marine Clay." Characterisation and engineering properies of natural soils,429-454. Tanaka, H. (1994). "Behaviour of braced excavation in soft clay and the undrained shear strength for passive earth pressure." Soils and Foundations, 34(1), 53-64. Tanaka, H. and Terashi, M. (1986). "Engineering properties of treated soil by DMM in field."Report of Port and Harbour Research Institute.(Japanese) Tatsuoka, F. and Kobayashi, A. (1983). "Triaxial strength characteristics of cement treated soft clay." Proc. of the 8th European Regional Conference on Soil Mechanics and Foundation Engineering, 1, 421-426. Tatsuoka, F., Kohata, Y., Uchida, K. and Imai, K. (1996). "Deformation and strength characteristics of cement-treated soils in Trans-Tokyo Bay Highway project." Grouting and Deep mixing, The Second International Conference on Ground Improvement Geosystems, Tokyo,453-459. Tatsuoka, F., Uchida, K., Imai, K., Ouchi, T. and Kohata, Y. (1997). "Properties of cement treated soil in Trans-Tokyo Bay Highway project." Ground Improvement, 1(1), 37-57. Tavenas, F., jean, P., Leblond, P. and Leroueil, S. (1986). "In situ measurement of permeability in soft clays." ASCE Special Conference on Use of In Situ Test in Geotechnical Engineering, Blacksburg,1034-1048. Tjahyono, S. (2011) Experimental and numerical modelling of spudcan penetration in stiff clay overlying soft clay. Ph.D, National University of Singapore. Topolnicki, M. (2004). In situ soil mixing. Ground Improvement 2nd Edition. M. P. M. a. K. Kirsch, Spon Press: 331-428. 251 Tsuzuki, M., Nakajima, J., Takayama, S. and Kanekura, T. (2000). "Behavior of cantilever earth retaining with buttress type stabilisation." Geotechnical Aspects of Underground Construction in Soft Ground,593-598. Uchida, Y., Rokugo, K. and Koyanagi, W. (1991). "Determination of tension softening diagrams of concrete by means of bending tests." Journal of Materials, Concrete Structures and Pavements of JSCE, 426, 203-212. Uchiyama, N. and Kamon, M. (1998). "Deformations of buttress type ground improvement and untreated soil during strutted excavation in clay." 2nd International Conference on Ground Improvement Techniques, Singapore,505-512. Uddin, K., Balasubramaniam, A. S. and Bergado, D. T. (1997). "Engineering behavior of cementtreated Bangkok soft clay." Geotechnical Engineering, SEAGS, 28(1), 89-119. Vogler, U. and Karstunen, M. (2009). Applicaiton of volume averaging technique in numerical modeling of deep mixing. London, Taylor & Francis Group. Wahalathantri, B. L., Thambiratnam, D. P., Chan, T. H. T. and Fawzia, S. (2011). "A material model for flexural crack simulation in reinforced concrete elements using ABAQUS." In Proceedings of the First International Conference on Engineering, Designing and Developing the Built Environment for Sustainable Wellbeing, Brisbane,260-264. Wen, D. (2005). Use of jet grouting in deep excavations, Elsevier. Wong, K. S. and Goh, A. T. C. (2006). "Modelling jgp slab in deep excavation analysis." International Conference on Deep Excavations, Singapore Wong, K. S. and Goh, A. T. C. (2006). "Modelling JGP Slab in Deep Excavation Analysis." International Conference on Deep Excavation, Singapore Xiao, H. W. (2009) Yielding and failure of cement treated soil. Ph.D, National University of Singapore. Yang, H. B. (2009) Mobilised mass properties of embedded improved soil raft in an excavation. Ph.D, National University of Singapore. Yin, J. H. and Lai, C. K. (1998). "Strength and stiffness of Hong Kong marine deposits mixed with cement." Geotechnical Engineering, SEAGS, 29(1), 29-44. Yong, K. Y., Karunaratne, G. P. and Lee, S. L. (1990). "Recent devlopments in soft clay engineering in Singapore." Proc. Kansai Int. Geotech. Forum '90: Comparative Geotechnical Engineering, Osaka, Japan,1-8. Yu, M., Xia, G. and Kolupaev, V. A. (2009). "Basic characteristics and development of yield criteria for geomaterials." Journal of Rock Mechanics and Geotechnial Engineering, 1(1), 71-88. 252 Yu, Y., Pu, J., Ugai, K. and Hara, T. (1999). "A study on the perneability of soil-cement mixture." Soils and Foundations, 39(5), 145-149. Zhang, Y. D. (2004) An embedded improved soil berm in an excavation-mechanisms and capacity. Ph.D, National University of Singapore. Zheng, H., Tham, L. G. and Liu, D. F. (2006). "On two definitions of the factor of safety commonly used in the finite element slope stability analysis." Computers and Geotechnics, 33, 188-195. Zheng, S. Y. and Zhao, Y. R. (2004). "Application of strength reduction FEM in soil and rock slope." Chinese Journal Rock Mech Eng, 23(19), 3381-3388. Ziaie Moayed, R., Tamassoki, S. and Izadi, E. (2012). "Numerical modeling of direct shear tests on sandy clay." International Journal of Civil and Environmental Engineering, 6, 106-110. 253 [...]... 6.2 Summary of case analyses based on the in-situ strength of cemented soil column Table 6.3 Model parameters for CDP model of cemented column Table 6.4 Summary table of analysis cases for case study 2 Table 6.5 Design parameters for Mohr Coulomb and Tresca models used in case study 2 Table 6.6 Design parameters for case study 3 viii List of Figures Figure 1.1 Cement- treated soil columns used in Lexington,... earlier Cement- treated soil columns of diameter 2.4 m and length 8.5 m were constructed to facilitate the 4.9 m deep open excavation The cross section of the retaining wall and site photographs are presented in Figure 1.1 On the other hand, Haque and Bryant (2011) observed substantial soil body movement behind a cement- treated soil retaining wall in Irving-Las Colinas in Texas, USA Failure of cement- treated. .. behavior of this material is not well understood As a result, this study aims to investigate the mechanism of cement- treated soil columns used as earth retaining system in an open excavation The scope of study is as follows: a) To carry out laboratory studies to investigate the compressive and tensile behaviors of cement- treated marine clay including interpretation of post-peak softening of the treated. .. effect of different constitutive models (namely elastic-perfectly plastic Tresca model, isotropic model and concrete damage plasticity model) in simulating the behavior of cement- treated soil The results are calibrated against those data obtained from different types of laboratory tests conducted on cement- treated sand and cementtreated clay c) To simulate the behavior of cement- treated soil columns... (2012) Figure 1.2 Failure case of adopting cement- treated soil columns as a retaining system for an open excavation in Northeastern Singapore Figure 1.3 Examples of soil improvement pattern Figure 2.1 Change of water content by in-situ cement treatment in Tokyo Port (after Kawasaki et al., 1978) Figure 2.2 Effect of curing time and cement content on final water content of treated clay (after Kamruzzaman,... cement- treated soil wall did happen in the field but such cases are rarely published Figure 1.2 shows failure happened in Northeastern Singapore where cement- treated soil columns were adopted as retaining system to facilitate an open excavation The front row of cement- treated soil columns collapsed when excavation reached 7 m depth 1.2 Issues Related to the Use of Cement- treated Soil Columns To optimize... material assumed in the design, as the bonding between cemented soil columns and between cemented soil column (tensile strength) and soil (cohesive strength) might be weaker than the original ground Weak bonding may cause separation of columns especially the front columns along the intended excavation line from the rest of the row resulting in toppling of these columns, making the composite mass assumption... load-displacement relations modeled by classic Tresca and CDP models Figure 6.12 Yielding zone at cemented column observed in classical Tresca model analysis Figure 6.13 Soil profile sketch for case study 2 Figure 6.14 Proposed construction supported by diaphragm wall and cement- treated soil for case study 2 Figure 6.15 On-site excavation profile for case study 2 Figure 6.16 Collapse of front row cement- treated. .. movement (m); Right: Plastic strain Figure 6.22 Ground response for Case C-R2 Left: Ground movement (m); Right: Plastic strain Figure 6.23 Ground movement and tensile damage (dt) at cement- treated soil columns for Case C-R3 Figure 6.24 Soil profile and proposed construction method for case study 3 Figure 6.25 On-site excavation profile and visible cracks at the cement- treated soil columns appeared immediate... 1.4 Structure of Thesis The outline of this thesis after this introductory chapter is presented as follows: a) Chapter 2 reviews the general aspects of cement- treated soil where the changes in physical and mechanical properties are discussed The current design procedures and methods for cement- treated soil columns used in an open excavation are also evaluated Existing numerical studies of cement- treated . CHARACTERIZATION AND MODELING OF CEMENT- TREATED SOIL COLUMN USED AS CANTILEVER EARTH RETAINING STRUCTURE SAW AY LEE NATIONAL UNIVERSITY OF SINGAPORE 2014 CHARACTERIZATION AND. interaction between treated and untreated soil. In practice, cement- treated soil mass with certain columnar shaped treated soil are often analyzed using weighted average simulation (WAS) approach. behavior of cement- treated soil columns used as a retaining system in an open cut excavation. The first objective of this study is to understand the material properties of cement- treated Singapore