1st Edition
Quality Control and Assurance of the Deep Mixing Method
The deep mixing (DM) method developed 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.
Preface
List of Technical Terms and Symbols
1 Overview of Deep Mixing Method and Scope of the Book
1.1 DEFINITION OF SOFT GROUND
1.2 OUTLINE OF ADMIXTURE STABILIZATION
1.2.1 Basic mechanism
1.2.2 Type of admixture techniques
1.3 DEEP MIXING METHOD
1.3.1 Outline of deep mixing method
1.3.2 Classification of deep mixing method
1.3.2.1 On land works
1.3.2.2 Marine works
1.3.3 Column/element installation patterns and applications
1.4 Scope of book
REFERENCES
2 Quality Control and Assurance of Deep Mixing Method
2.1 IMPORTANCE OF QUALITY CONTROL AND QUALITY ASSURANCE
2.2 WORK FLOW OF DEEP MIXING PROJECT AND QC/QA
2.3 CURRENT PRACTICE OF QC/QA
2.3.1 Basic concept of laboratory, field and design standard strengths
2.3.2 Process design
2.3.2.1 Flow of mixing design and process design
2.3.2.2 Mixing condition in laboratory and field
2.3.2.3 Tips of laboratory mix test
2.3.3 Selection of deep mixing equipment
2.3.4 Field trial test
2.3.5 Quality control during production
2.3.5.1 Construction procedure
2.3.5.2 Overlap columns/elements
2.3.5.3 Operational parameters
2.3.5.4 Example of construction procedure
2.3.6 Quality control throughout construction period
2.3.6.1 Material management
2.3.6.2 Modification of construction control values
2.3.6.3 Damage of mixing tool
2.3.6.4 Lateral displacement and ground heaving
2.3.7 Report
2.3.8 Quality verification
2.3.8.1 Verification methods
2.3.8.2 Position of core boring
2.3.8.3 Frequency of core boring
2.3.8.4 Quality verification of boring core sample
2.3.8.5 Quality verification by laboratory test
2.3.8.6 Evaluation of unconfined compressive strength
2.3.9 Rectification of non-compliant column/element
REFERENCES
3 Technical Issues on QC/QA of Stabilized Soil
3.1 INTRODUCTION
3.2 FIELD AND LABORATORY STRENGTHS
3.2.1 Prediction of strength
3.2.2 Strength ratio of field to laboratory strengths, quf/qul
3.2.3 Strength deviation in field strength
3.3 LABORATORY MIX TEST
3.3.1 Role and basic approach of laboratory mix test
3.3.2 Selection of soil for laboratory test and water to binder ratio of binder slurry, w/c
3.3.3 Effect of specimen size
3.3.3.1 Strength
3.3.3.2 Young’s modulus
3.3.4 Effect of molding technique
3.3.5 Effect of overburden pressure during curing
3.3.6 Effect of curing temperature
3.3.6.1 Temperature in ground
3.3.6.2 Effects of curing temperature and period
3.3.6.3 Maturity
3.4 SELECTION OF DEEP MIXING EQUIPMENT
3.4.1 Factors influencing mixing degree
3.4.1.1 Influence of number of mixing shafts
3.4.1.2 Influence of type and shape of mixing blade
3.4.1.3 Influence of diameter of mixing blade
3.4.1.4 Influence of penetration speed of mixing tool
3.4.2 Required blade rotation number
3.4.2.1 Influence of blade rotation number in laboratory model tests
3.4.2.2 Influence of blade rotation number in field test
3.4.2.3 Influence of blade rotation number in field actual works
3.4.3 Stabilization at shallow depth and influence of ground heaving
3.4.3.1 Basic production procedure and effect of sand mat
3.4.3.2 Influence of ground heaving
3.4.4 Bottom treatment
3.4.5 Overlap columns/elements
3.5 VERIFICATION TECHNIQUES IN QUALITY ASSURANCE
3.5.1 Core boring
3.5.1.1 Procedure
3.5.1.2 Frequency of boring core sampling and specimen
3.5.1.3 Coring boring technique
3.5.1.4 Size of boring core
3.5.1.5 Macro scopic evaluation of strength of field stabilized soil
3.5.2 Applicability of wet grab sampling
3.5.2.1 Type of wet grab sampling
3.5.2.2 Comparison of sampling type
3.5.2.3 Comparison of wet grab sample strength and boring core sample strength
3.5.2.4 Applicability of wet grab sampling for QA
REFERENCES
4 Problems and Countermeasures Associated with Problematic Soils
4.1 PROBLEMATIC SOIL FOR STABILIZATION
4.2 COUNTERMEASURES FOR PROBLEMATIC SOILS
4.2.1 Water injection
4.2.2 Use of new type special cement
4.2.3 Use of dispersant
4.2.4 Injecting atomized cement slurry
4.2.5 Summary
REFERENCES
5 Water to Binder Ratio Concept in QC
5.1 INTRODUCTION
5.2 DEFINITION OF W/C RATIO
5.2.1 Definition of W/C
5.2.2 Relationship between W/C ratio and stabilized soil strength
5.3 PREDICTION OF FIELD STRENGTH BY PRODUCTION LOG DATA
5.3.1 Production log data
5.3.2 Analysis of production log data
5.3.3 Countermeasure for water injection
5.4 SUMMARY
REFERENCES
Subject Index
Biography
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 in 2019.
