Quality Control and Assurance of the Deep Mixing Method

The deep mixing (DM) methoddeveloped in Japan and Sweden in the 1970s has gained popularity worldwide. The DM-improved ground is a composite system comprising stiff stabilized soil and unstabilized soft soil, which necessitates geotechnical engineers to fully understand the interaction of stabilized and unstabilized soils and the engineering characteristics of in-situ stabilized soil. The success of the DM project cannot be achieved by the well-determined geotechnical design alone but is guaranteed only when the quality and geometric layout envisaged in the design is realized in the field with an acceptable level of accuracy. The process design, production with careful quality control and quality assurance are the key issues in the DM project. This book is intended to provide the state of the art and practice of quality control and assurance on deep mixing in detail based on the experience and research efforts accumulated in the past 50 years.

PrefaceList of Technical Terms and Symbols1 Overview of Deep Mixing Method and Scope of the Book1.1 DEFINITION OF SOFT GROUND1.2 OUTLINE OF ADMIXTURE STABILIZATION1.2.1 Basic mechanism1.2.2 Type of admixture techniques1.3 DEEP MIXING METHOD1.3.1 Outline of deep mixing method1.3.2 Classification of deep mixing method1.3.2.1 On land works1.3.2.2 Marine works1.3.3 Column/element installation patterns and applications1.4 Scope of bookREFERENCES 2 Quality Control and Assurance of Deep Mixing Method2.1 IMPORTANCE OF QUALITY CONTROL AND QUALITY ASSURANCE2.2 WORK FLOW OF DEEP MIXING PROJECT AND QC/QA2.3 CURRENT PRACTICE OF QC/QA2.3.1 Basic concept of laboratory, field and design standard strengths2.3.2 Process design2.3.2.1 Flow of mixing design and process design2.3.2.2 Mixing condition in laboratory and field2.3.2.3 Tips of laboratory mix test2.3.3 Selection of deep mixing equipment2.3.4 Field trial test2.3.5 Quality control during production2.3.5.1 Construction procedure2.3.5.2 Overlap columns/elements2.3.5.3 Operational parameters2.3.5.4 Example of construction procedure2.3.6 Quality control throughout construction period2.3.6.1 Material management2.3.6.2 Modification of construction control values2.3.6.3 Damage of mixing tool2.3.6.4 Lateral displacement and ground heaving2.3.7 Report2.3.8 Quality verification2.3.8.1 Verification methods2.3.8.2 Position of core boring2.3.8.3 Frequency of core boring2.3.8.4 Quality verification of boring core sample2.3.8.5 Quality verification by laboratory test2.3.8.6 Evaluation of unconfined compressive strength2.3.9 Rectification of non-compliant column/elementREFERENCES 3 Technical Issues on QC/QA of Stabilized Soil3.1 INTRODUCTION3.2 FIELD AND LABORATORY STRENGTHS3.2.1 Prediction of strength3.2.2 Strength ratio of field to laboratory strengths, quf/qul3.2.3 Strength deviation in field strength3.3 LABORATORY MIX TEST3.3.1 Role and basic approach of laboratory mix test3.3.2 Selection of soil for laboratory test and water to binder ratio of binder slurry, w/c3.3.3 Effect of specimen size3.3.3.1 Strength3.3.3.2 Young’s modulus3.3.4 Effect of molding technique3.3.5 Effect of overburden pressure during curing3.3.6 Effect of curing temperature3.3.6.1 Temperature in ground3.3.6.2 Effects of curing temperature and period3.3.6.3 Maturity3.4 SELECTION OF DEEP MIXING EQUIPMENT3.4.1 Factors influencing mixing degree3.4.1.1 Influence of number of mixing shafts3.4.1.2 Influence of type and shape of mixing blade3.4.1.3 Influence of diameter of mixing blade3.4.1.4 Influence of penetration speed of mixing tool3.4.2 Required blade rotation number3.4.2.1 Influence of blade rotation number in laboratory model tests3.4.2.2 Influence of blade rotation number in field test3.4.2.3 Influence of blade rotation number in field actual works3.4.3 Stabilization at shallow depth and influence of ground heaving3.4.3.1 Basic production procedure and effect of sand mat3.4.3.2 Influence of ground heaving3.4.4 Bottom treatment3.4.5 Overlap columns/elements3.5 VERIFICATION TECHNIQUES IN QUALITY ASSURANCE3.5.1 Core boring3.5.1.1 Procedure3.5.1.2 Frequency of boring core sampling and specimen3.5.1.3 Coring boring technique3.5.1.4 Size of boring core3.5.1.5 Macro scopic evaluation of strength of field stabilized soil3.5.2 Applicability of wet grab sampling3.5.2.1 Type of wet grab sampling3.5.2.2 Comparison of sampling type3.5.2.3 Comparison of wet grab sample strength and boring core sample strength3.5.2.4 Applicability of wet grab sampling for QAREFERENCES 4 Problems and Countermeasures Associated with Problematic Soils4.1 PROBLEMATIC SOIL FOR STABILIZATION4.2 COUNTERMEASURES FOR PROBLEMATIC SOILS4.2.1 Water injection4.2.2 Use of new type special cement4.2.3 Use of dispersant4.2.4 Injecting atomized cement slurry4.2.5 SummaryREFERENCES 5 Water to Binder Ratio Concept in QC5.1 INTRODUCTION5.2 DEFINITION OF W/C RATIO5.2.1 Definition of W/C5.2.2 Relationship between W/C ratio and stabilized soil strength5.3 PREDICTION OF FIELD STRENGTH BY PRODUCTION LOG DATA5.3.1 Production log data5.3.2 Analysis of production log data5.3.3 Countermeasure for water injection5.4 SUMMARYREFERENCES Subject Index

Masaki Kitazume graduated from Tokyo Institute of Technology in 1979, and obtained his Master of Engineering in 1981. Then he joined the Port and Harbour Research Institute, Ministry of Transport and has been the head of the Soil Stabilization laboratory and has worked on the interaction of improved ground and soft ground. In 1994, he got a Doctor of Engineering from Tokyo Institute of Technology on the design of stability of Deep Mixing improved ground. In 2011, he was invited to become professor of the Department of Civil and Environmental Engineering, Tokyo Institute of Technology.He has published many papers, mainly on the geotechnical aspects of soil stabilization, ground improvement and centrifuge model testing. He also published three books from Balkema Publishers and Taylor & Francis, on Deep Mixing Method, Sand Compaction Pile Method and Pneumatic Flow Mixing Method. He was awarded the Geotechnical Engineering Development award from the Japanese Society of Soil Mechanics and Foundation Engineering in 1992, the Minister of Transport Award in 2000, and Continuing International Contribution Awards, Japan Society of Civil Engineers in 2006, Geotechnical Engineering Research Achievements Award, the Japanese Society of Soil Mechanics and Foundation Engineering in 2018, and Telford Premium Prize, ICE Awards in2019.