This document is downloaded from DR‑NTU (https://dr.ntu.edu.sg) Nanyang Technological University, Singapore. Geotechnical properties of biocement treated sand and clay Li, Bing 2015 Li, B. (2015). Geotechnical properties of biocement treated sand and clay. Doctoral thesis, Nanyang Technological University, Singapore. https://hdl.handle.net/10356/62560 https://doi.org/10.32657/10356/62560 Downloaded on 07 Oct 2021 07:43:27 SGT GEOTECHNICAL PROPERTIES OF BIOCEMENT TREATED SAND AND CLAY LI BING SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING 2015 GEOTECHNICAL PROPERTIES OF BIOCEMENT TREATED SAND AND CLAY LI BING School of Civil and Environmental Engineering A thesis submitted to the Nanyang Technological University in partial fulfillment of the requirement for the degree of Doctor of Philosophy 2015 Acknowledgements This project would not have been possible and successful without the continuous guidance from my supervisor Prof Chu Jian. I would like to express the most sincere gratitude for his inspiration, patience and guidance. His endlessly support and invaluable experience came handy throughout all these years. His close monitoring and encouragement are especially appreciated. I would also like to express my special thanks to Prof Andrew Whittle and Dr Volodymyr Ivanov as co-supervisors. I sincerely thank them for the wonderful opportunity to be part of this project, and their patience, guidance and invaluable knowledge sharing. I wish to acknowledge the help provided by Mr. Heng Hiang Kim Vincent, Mr. Tan Hiap Guan Eugene, Ms Lim-Ding Susie and Mr. Koh Sun Weng Andy from the Geotechnical Laboratory, and Mr. Ong Chee Yung, Mr. Tan Han Khiang, Ms See Shen Yen, Pearlyn, Ms Maria Chong Ai Shing and the rest of the staff from the Environmental Laboratory for rendering the help on equipment, chemicals and laboratory testing. The appreciation extends to Dr. Guo Wei, Dr. Maryam Naiemi, Mr Wu Shifan, Dr. He Jia and Mr Wang Yue for their invaluable friendships, helps and advices throughout this project. Abstract The application of microbial technologies to improve the mechanical properties of soils is a new and fast developing research area in geotechnical engineering. Microbially induced calcium carbonate precipitation (MICP) is the most commonly employed biocementation method. Application of MICP for sand has been studied by many researchers. However, few studies had been carried out for fine-grained soils such as clay or other types of low permeability materials. In this research project, optimization of biocementation in sand and feasibility of using biocement to improve the mechanical properties of clayey soil were studied. Element tests using small cylindrical samples as well as model tests using soil of up to one cubic meter in volume were carried out. Different chemical compositions and types of bacteria were tested for both sand and clay. The properties of the MICP treated soil were assessed by unconfined compression tests, triaxial tests, direct simple shear tests, and flexible wall permeability tests using a triaxial cell. The results show that biocementation using urease producing bacteria (UPB) with low activity is effective for both small samples and relatively large samples in the model tests. Results of consolidated drained (CD) triaxial tests on sand with different degrees of biocementation treatment indicate that the strength gained through bio-treatment is related mainly to the increase in cohesion provided by the biocementation effect. In addition to increasing the shear strength, the permeability of sand is also reduced by bioclogging. One method is to form a calcite crust of 2 to 3 mm thick on the top surface of sand. This method can reduce the coefficient of permeability of sand from 10-4 m/s to 10-8 m/s. The possible applications of MICP to fine grained soils including kaolin, marine clay and bentonite were explored. The experiments show that a higher shear strength was observed for clayey soil mixed with UPB and cementation reagents compared to pure soil under the same water content. However, excess calcium cation used for the MICP process may impede the strength improvement. Another possible method is to make clay balls through premixing with bacteria and cementation reagents. Table of Contents Table of Contents ACKNOWLEDGEMENTS ......................................................................................................... I ABSTRACT ................................................................................................................................. I TABLE OF CONTENTS ............................................................................................................. I CHAPTER 1 INTRODUTION ................................................................................................... 1 1.1 BACKGROUND ........................................................................................................................... 1 1.2 OBJECTIVES .............................................................................................................................. 2 1.3 OUTLINE OF THESIS ................................................................................................................... 3 CHAPTER 2 LITERRATURE REVIEW .................................................................................. 4 2.1 INTRODUCTION.......................................................................................................................... 4 2.2 OVERVIEW OF BIOLOGICAL APPROACHES IN SOIL IMPROVEMENT ............................................. 4 2.2.1 Effects of bacteria on soil shear stress in nature .............................................................. 4 2.2.2 Overview of bio-mediated soil improvement methods ...................................................... 6 2.2.3 Biocementation ................................................................................................................. 8 2.2.4 Bioclogging ..................................................................................................................... 16 2.2.5 Bioremediation ................................................................................................................ 17 2.2.6 Negative effects of microbial activities ........................................................................... 19 2.3 FACTORS INFLUENCING MICP PROCESS MEDIATED BY UPB ................................................... 19 2.3.1 Urease activity of UPB ................................................................................................... 20 2.3.2 Effect of chemical concentration in cementation solutions ............................................. 27 2.3.3 UPB distribution and fixation ......................................................................................... 31 2.3.4 Flow rate and direction .................................................................................................. 33 2.3.5 Large-scale biocementation experiment in sand ............................................................. 36 2.3.6 Summary of calcite content vs. UC strength relationship in sand .................................. 36 2.3.7 Summary of calcium content vs. permeability in sand .................................................... 40 2.3.8 MICP application on residual soil .................................................................................. 41 2.4 ENGINEERING PROPERTIES OF SOIL .......................................................................................... 43 2.4.1 Critical state soil mechanics ........................................................................................... 43 2.4.2 Dilatancy and failure envelope in cemented granular materials .................................... 45 2.5 PROPERTIES OF CLAY .............................................................................................................. 48 2.5.1 Structure of clay minerals ............................................................................................... 48 2.5.2 Surface chemistry of clay particles ................................................................................. 49 2.5.3 Influence of water content in shear strength of clay ....................................................... 57 2.5.4 Atterberg limits presented engineering parameters ........................................................ 59 2.5.5 Clay cementation ............................................................................................................ 60 2.6 SUMMARY ............................................................................................................................... 63 CHAPTER 3 METHODS AND MATERIALS ........................................................................ 66 3.1 INTRODUCTION........................................................................................................................ 66 i Table of Contents 3.2 CULTIVATION OF BACTERIA .................................................................................................... 67 3.2.1 Cultivation of urease-producing bacteria (UPB) ............................................................ 67 3.2.2 Centrifuging and re-suspension of UPB ......................................................................... 69 3.3 CALCIUM/UREA CONTENT MONITORING .................................................................................. 70 3.3.1 Calcium content determination ......................................................................................