Centrifuge model study of mixing quality in wet deep mixing

TITLE PAGE  CENTRIFUGE MODEL STUDY OF MIXING  QUALITY IN WET DEEP MIXING  CHEN JIAN  (M.Eng., B.Eng., B.A., HUST) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY DEPARTMENT OF CIVIL AND ENVIRONMENTAL ENGINEERING NATIONAL UNIVERSITY OF SINGAPORE 2012 -ii- Dedicated to my families iii -iv- 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. v -vi- ACKNOLEDGEMENTS  First and foremost, I would like to express my sincerest gratitude and appreciation to my supervisor, Professor Lee Fook Hou, who has supported me with his valuable, patient and endless guidance throughout my Ph.D study. He does not only teach me with knowledge but also how to face difficulties in both research work and daily life. I attribute the level of my doctor’s degree to Prof. Lee’s encouragement and effort and without him, this thesis, too, would not have been able to be completed. The philosophy I learned from Prof. Lee during the past five years will be priceless fortune of mine and influence my career in a life time. During my Ph.D study, I have been aided a lot by the technical and professional staffs in NUS Centrifuge and Geotechnical Laboratory. I would like to thank Mr. Tan Lye Heng, Mr. Wong Chew Yuen, Dr. Shen Ruifu and Mr Loo Leong Huat for their precious help and constructive comments for my centrifuge testing. Moreover, acknowledgements should also be given to Mr. John Choy, Ms. Jamilah, Mr. Foo Hee Ann, Mr. Sit Beng Chiat, Ms. Lee Leng Leng, Mr. Yong Tat Fah, Mr. Ang Beng Oon, Ms. Sandra Martin and Mr. Shaja Khan. Special acknowledgement should also be given to Assistant Professor, Dr. Goh Siang Huat, who gave me helpful comments on my research and paper writing. Moreover, I am also grateful to my fellow colleagues, my seniors and juniors. They vii are Assistant Professor Cheng Yonggang, Dr. Yeo Chong Hun, Dr. Xiao Huawen, Dr. Yi Jiangtao, Mr. Zhao Ben, Mr. Liu Yong, Ms. Li Yuping, Mr. Yang Yu, Mr. Zhang Lei. Special thank is given to Mr. Liu Yong. He undertook the part of numerical simulation in this project of deep mixing method. And the constructive discussions and collaboration between us promoted the completion of this thesis. Moreover, I acknowledge the financial support by Research Scholarship Programme from the National University of Singapore. Without this financial support, I could not accomplish this study. Finally, I would like to express the most grateful acknowledgements to my families, my wife, daughter and parents, who gave me endless support and encouragement to complete my research and writing up. -viii- TABLE OF CONTENTS  TITLE PAGE  .i  ACKNOLEDGEMENTS  . vii  TABLE OF CONTENTS   ix  SUMMARY   xv  LIST OF TABLES  . xvii  LIST OF FITURES   xix  LIST OF SYMBOLS   xxxvii  Chapter 1  Introduction  . 1  1.1  Background on ground improvement . 1  1.2  Deep Mixing Method 1  1.3  Mixing process of DMM 3  1.4  Objectives and significance of this study 5  1.4.1.  Scope and objectives 5  1.4.2.  Significance of this study . 6  1.5  Structure of the thesis 8  Chapter 2  Literature Review  . 15  2.1.  Introduction to literature review . 15  2.2.  Field tests for DMM 15  2.3.  Physical modelling 19  2.3.1.  1-g modelling . 19  ix 2.3.2.  Centrifuge modelling . 22  2.4.  Quality assessment and control for DM columns . 26  2.4.1.  Mixing uniformity 26  2.4.2.  Influencing factors to deep mixing quality 31  2.4.3.  Quality control and assurance 34  2.5.  Mixing process and tools for DMM 34  2.6.  Probabilistic and statistical methods in DM studies . 39  2.6.1.  Statistical methods in lab and field testing 39  2.6.2.  Studies on autocorrelation 42  2.7.  Empirical strength functions of stabilized soil 44  2.8.  Limitations of the previous studies . 48  2.8.1.  Field testing and physical modelling . 49  2.8.2.  Influencing factors to the mixing uniformity . 50  Chapter 3  Experimental Setup and Procedures  . 79  3.1.  Introduction to experimental work 79  3.2.  Centrifuge model 79  3.2.1.  Model container . 79  3.2.2.  Model DM installers 80  3.2.3.  Model binder 81  3.2.4.  Design of single-shaft DM system . 82  3.2.5.  Design of multi-shaft deep mixer 82  -x- Appendix-A Figure Appendix-A.27 Raw measurements in percentage for model test DMC30 -283- Appendix-B Figure Appendix-A.28 -284- Raw measurements in percentage for model test DMC31 Appendix-A Figure Appendix-A.29 Raw measurements in percentage for model test DMC32 -285- Appendix-B Figure Appendix-A.30 -286- Raw measurements in percentage for model test DMC32B Appendix-A Figure Appendix-A.31 Raw measurements in percentage for model test DMC32C -287- Appendix-B Figure Appendix-A.32 -288- Raw measurements in percentage for model test DMC33 Appendix-A Figure Appendix-A.33 Raw measurements in percentage for model test DMC33B -289- Appendix-B Figure Appendix-A.34 -290- Raw measurements in percentage for model test DMC34B Appendix-A Figure Appendix-A.35 Raw measurements in percentage for model test DMC36 -291- Appendix-B Figure Appendix-A.36 -292- Raw measurements in percentage for model test DMC37 Appendix-A Figure Appendix-A.37 Raw measurements in percentage for model test DMC38 -293- Appendix-B Figure Appendix-A.38 -294- Raw measurements in percentage for model test DMC39 Appendix-A Figure Appendix-A.39 Raw measurements in percentage for model test DMC40 -295- Appendix-B -296- Appendix-B Appendix­B.   Relevant publications  [01] Chen, J., Lee, F.H. and Ng, C.C. (2011). "Statistical analysis for strength variation of deep cement mixing columns in Singapore." ASCE Geotechnical Special Publication: GeoFrontiers 2011: Advances in Geotechnical Engineering (GSP 211), J. Han and D. E. Alzamora, eds., Geo-Institute, ASCE, Dallas: 576-584. [02] Chen, J., Sheng, H., Cheng, Y.G. and Goh, S.H. (2011). "Field Monitoring of Excavation Supported by Deep Mixing Columns." Proceedings of the 24th KKCNN Symposium on Civil Engineering. Awaji Island, Hyogo, Japan, 14-16 December: 415-418. [03] Chen, J. and Lee, F.H. (2012). "Development of a deep mixing model system on centrifuge platform." ASCE Geotechnical Special Publication: GeoCongress 2012: Geotechnical Engineering State of the Art and Practice (GSP 225), K. Rollins and D. Zekkos eds., Geo-Institute, ASCE, Oakland: 930-939. [04] Chen, Elton J., and Lee, F.H. (2014). "A dual-shaft deep soil mixing Apparatus for Centrifuge Modeling." The 8th International Conference on Physical Modelling in Geotechnics 2014, Perth, Australia, 14-17 January, 2014. (Accepted) Several journal manuscripts are under review. -297- Appendix-B -298- [...]... feasibility of using centrifuge to model the wet DM process and initiated the parametric studies on various factors affecting the uniformity of the mixing In this study, a new centrifuge model, which can be used to simulate the in- flight deep mixing process of both single and multi-shaft, was developed Moreover, a post-processing procedure for faster sample measuring was proposed Based on a series of centrifuge. .. uniformity of the strength distribution of DM columns depends on the degree of mixing in the DM installation process However, due to the lack of research on the mixing process, the highly variable strength of the DMM improved soil, which indicates poor mixing quality, remains a problem in construction Larsson (2003) theoretically analyzed the mechanism of the mixing process and studied the uniformity of binder... Comparison of strength achieved using 1-shaft and 4-shaft model mixers (Nishibayashi et al 1985) 69  Figure 2.35 Open-type mixing blade (Abe et al 1997) 70  Figure 2.36 Comparison of quality with and without free blade (Enami et al 1985) 70  Figure 2.37 Influence of rotation speed of mixing blade (Nishibayashi et al 1985) 71  Figure 2.38 Influence of penetration speed of mixing. .. Typical section of Deep Mixing 215  Figure 6.5 Typical soil borehole log of the construction site 216  Figure 6.6 Design drawing of mixing rod and bit (a) and field equipment at Marina Bay construction site (b, c) 217  Figure 6.7 Drilling and injection route of DM construction in MBFC Project 217  Figure 6.8 Comparison of model predicted PDF and the histograms of field strength... observed in centrifuge tests (Kitazume et al 1996a; Kitazume and Maruyama 2007a) 63  Figure 2.22 (a) Centrifuge model for DM retaining wall, (b) reinforcement ratio of 0.08%, (c) reinforcement ratio of 0.4% (Babasaki and Suzuki 1998) 64  Figure 2.23 Plan and side view of the in- situ retaining wall tests (Babasaki and Suzuki 1998) 65  Figure 2.24 (a) Model ground (b) deformation of. ..3.3.  Scaling relations 83  3.4.  Test preparations 84  3.4.1.  Preparation of the model soil bed 84  3.4.2.  Assembly of the DM model system 85  3.4.3.  Determination of the binder density 85  3.4.4.  Control and monitoring of the soil properties 86  3.5.  Deep mixing process 87  3.6.  Post-processing of the tests 87  3.6.1.  Sampling procedure... Prototype auger and installed test DM columns (Al-Tabbaa et al 1998) 58  Figure 2.10 (a) Double mixing machine (b) model equipment (Horpibulsuk et al 2004) 58  Figure 2.11 (A) Mixing tool employed in the field; (B) Cement stabilized specimen mixed in lab and field (Van Impe and Verastegui Flores 2006) 58  Figure 2.12 (A) 1-g model for in- situ mixing (B) types of mixing blades (Dong... empirical formula -xvi- LIST OF TABLES  Table 1.1 Terminology of the DM family (After Porbaha 1998) 9  Table 1.2 Development of deep mixing method (From Terashi and Juran 2000) 9  Table 2.1 Factors affecting the strength increase (After Terashi 1997) 53  Table 3.1 Scaling implications of centrifuge model tests (After Lee et al 2008) 93  Table 3.2 Physical properties of Kaolin Clay (After Ong 2004)... of centrifuge model tests for DMM, a detailed parametric study on the various factors affecting deep mixing quality has been carried out The factors include: blade rotation number, over-consolidation ratio, blade angle, binder density, mixing rotational speed, radial distance, soil depth and multi-shaft mixing Besides these factors, the autocorrelation structure in radial distance within the DM column... (a) Model setup (b) typical failure pattern (Kitazume et al 1996b) 59  Figure 2.14 (a) Model mixing machine (b) sampling location (Matsuo et al 1996) 60  Figure 2.15 Model column making device (a, b) and installed model column (c) (Shen and Saga Daigaku 1998) 60  Figure 2.16 Prototype and modelled DM system by Al-Tabbaa et al (1999) 61  Figure 2.17 Schematic of the installation of model . TITLEPAGE CENTRIFUGE MODEL STUDY OF MIXING QUALITY IN WET DEEP MIXING CHENJIAN (M.Eng., B.Eng., B.A., HUST) A THESIS SUBMITTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY. 1-g modelling 19 -x- 2.3.2. Centrifuge modelling 22 2.4. Quality assessment and control for DM columns 26 2.4.1. Mixing uniformity 26 2.4.2. Influencing factors to deep mixing quality. feasibility of using centrifuge to model the wet DM process and initiated the parametric studies on various factors affecting the uniformity of the mixing. In this study, a new centrifuge model,