Quality Control and Assurance of the Deep Mixing Method

Description

The deep mixing method (DM) 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 un-stabilized soft soil, which necessitates geotechnical engineers to fully understand the interaction of stabilized and un-stabilized 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. Cover Half Title Title Page Copyright Page Table of Contents Preface Author List of technical terms and symbols List of 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 the 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, q[sub(uf)] /q[sub(ul)] 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 Macroscopic 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 Index