真空堆载联合预压软土地基加固机理研究

论文题目: 真空堆载联合预压软土地基加固机理研究

论文类型: 博士论文

论文专业: 岩土工程

作者: 阿里哈桑

导师: 刘汉龙

关键词: 软土,改善,真空预压,超载,机理,固结,三轴仪,渗透性,孔隙比,孔压,理论,蠕变,偏应变,微观结构,变形

文献来源: 河海大学

发表年度: 2005

论文摘要: 预压，有时也称预压缩，是一种常用的软土改善技术。在实践中，预载最常见古老的形式是通过堆积砂填料产生超载机理。近年来，作为一种新技术方法的真空预压法，是一种常见的软土改善处理方法。真空预压是另一种形式的预压，它不需要填料，因为荷载是通过密封的橡皮膜系统以真空的形式作用于土体表面。真空使得土体中的孔隙水流出，并产生负孔压。真空预压法，除了通过增加总应力来增加有效应力外，它还依赖通过减小孔压来增加有效应力。因此，真空—堆载联合预压法可缩短固结时间，对那些需要相当长时间的固结特别适合，而且不危及试验路堤的稳定性。用填土超载的方法来快速预载是行不通的，因为很难在软土上迅速建筑一个数米高的填土路堤。真空预压中，砂井和近年来使用得很多的预制竖向排水板PVDs是用来传递真空以及消散孔压的。预知次固结，对地上建筑物，如建于软土上的高速公路路堤的维护是重要的，因为它们会导致不可忽视的沉降。关于一维，二维以及三维情况下的次固结有很多论文资料，但所有这些都没有研究真空预压法情况下的蠕变固结。本文主要内容包括： (1) 本文研究了真空预压下级配良好土体的蠕变特性和微观结构。 (2) 研制了一种新的三轴固结仪，并试验研究了中国浙江的温州软粘土随时间变化的特性。 (3) 因为水流的竖向及水平的流动改变了边界和初始条件，所以本文在太沙基的竖向固结理论竖向和巴隆的水平固结理论的基础上，还研究了真空预压、堆载预压和真空—堆载联合预压下的竖向固结的解析解。 (4) 流变学是研究真实材料的应力应变状态随时间改变的一门科学。本文考虑了土体体积变化的流变特性，即弹性，塑性，粘滞性。当粘土受恒载，在时间间隔内，粘土的变形会有粘滞性。土体随时间变形的大小取决于粘土的性质。真实体取决于时间的变形由粘土的所有性质：弹性，塑性，粘滞性决定。因为其性质可能以不同的组合出现，对真实体变形的描述是很困难的。因而，真实体的变形是通过考虑了简化了的特性或理想体的特性的模型来解释的。这类模型就是流变模型。在本文中，考虑了于粘滞性有关的主要现象，即蠕变。在恒载下，与时间有关的变形叫做蠕变。在土体中，能区分出两种取决于时间的现象类型：一种是由于超孔压的消散；另一种是由土体框架的内在粘滞性，如蠕变，应力松弛以及应变速率引起。在本文中，由于粘滞性将研究土的时效性。因而，下文中的时间效应，实效变形、时效性等，它们都是由土框架的粘滞性而引发的土的性质。 (5) 对经过真空预压、堆载预压、真空联合堆载预压后的土样进行电子显微镜扫描，通过使用扫描电微和电脑图象处理系统GEOIMAGE，作为微观结构的量化技术，就能得到土骨料的调整以及它的空隙。用参数来反映各向异性并分析了扫描电微图象的平均信息里旦。本文的机理研究表明真空联合堆载预压法是一种有效的软基加固方法。今后可对蠕变中的体积应变、应变速率及EVP模型在真空预压下细粒土的蠕变分析做进一步研究。关键词:软土，改善，真空预压，超载，机理，固结，三轴仪，渗透性，孔隙比，孔压，理论，蠕变，偏应变，微观结构，变形。

论文目录:

PREFACE

ABSTRACT

CHINESE ABSTRACT

CONTENTS

List of Figures

List of Tables

NOTATIONS

CHAPTER ONE INTRODUCTION

1．1 GENERAL

1．2 FIELD AND LABORATORY INSTRUMENTAIONS

1．2．1 MONITORING MEASURMENT DATA

1．3 SOIL RHEOLOGY

1．4 IMPORTANCE OF VISCOUS EFFECTS IN ENGINEERING PRACTICE

1．5 THE OBJECTIVE OF THIS STUDY

1．6 LITERATURE REVIEW

1．6．1 Vertical drains

1．6．1．1 Vertical sand drains

1．6．1．2 Prefabricated vertical drains (PVDs)

1．6．2 Vacuum preloading technique

1．6．2．1 Consolidation accelerated by vertical drains

1．6．3 Theory of consolidation

1．6．3．1 Three-Dimensional consolidation theory

1．6．3．2 Simplification of analysis for consolidation by three-dimensional flow

1．6．3．3 Vertical consolidation due to radial flow of water

1．6．3．4 Free strain consolidation with no smear and no well resistance

1．6．3．5 Equal strain consolidation with no smear and no well resistance

1．6．3．6 Comparison of free strain and equal strain solution

1．6．3．7 Effect of peripheral smear

1．6．3．8 Equal strain with smear

1．6．4 Plane-strain modeling of smear effects associated with vertical drains

1．6．4．1 Fundamentals of analytical solution

1．6．4．2 Modeling of Plane-Strain solution

1．6．5 Modeling of vertical drains with smear and well resistance

1．6．5．1 Discharge capacity of drains in modeling well resistance

1．6．6 Theoretical model of clay compressibility

1．6．7 Time-dependent yielding and creep

1．6．7．1 Creep (secondary consolidation)

1．6．7．1．1 Drained creep

1．6．7．1．2 Influence of temperature on viscousity of soil

1．6．7．1．3 Two Hypotheses on creep deformation

1．6．7．2 Creep (secondary consolidation) Model

1．6．7．2．1 Simple isotache model for one-dimensional compression

1．6．8 Effects of loading duration and rate of strain on clay compressibility

1．6．9 Unanticipated pore-water pressures

1．6．10 Consolidation in an elastic visco-plastic soil in one-dimensional straining

1．6．10．1 Magnitude of primary settlement

1．6．10．2 Magnitude of secondary settlement

1．6．11 Viscous stress-strain behaviour and pore-water pressure increase

CHAPTER TWO FIELD APPLICATIONS OF VACUUM PRELOADING TECHNIQUE

2．1 GENERAL

2．2 SEEDING OF THE PREFABRICATED VERTICAL DRAINS PVDs

2．3 FULL SCALE TEST EMBANKMENT

2．4 FIELD INSTRUMENTATIONS

2．5 COMBINED VACUUM AND SURCHARGE PRELOADING

2．6 PROJECT OF GUANG ZHOU - ZHU HAI EXPRESSWAY,GUAN DONG - CHINA

2．6．1 Vacuum consolidation technique

2．6．2 Soil profile of the proposed area

2．6．3 Full scale test embankment

2．6．4 Ground treatment work

2．6．5 Field instrumentations

2．6．6 Monitoring measurement data

2．6．7 Pore-water pressures

2．6．8 Statistical analysis

2．7 PROJECT OF SEA EMBANKMENT AT WENZHOU DISTRICT COAST OF CHINA

2．7．1 Technique of Vacuum Preloading

2．7．2 Soil investigation for the proposed area

2．7．3 Full scale test embankment

2．7．4 Ground treatment work

2．7．5 Field instrumentations

2．7．6 Measurement data

2．7．7 Pore water pressure

2．8 DETERIORATIONS OF SURROUNDING ENVIRONMENTS DUE TO USING VACUUM PRELOADING METHOD

2．8．1 General

2．8．2 Project of Wei-ba Road, Nanjing-China

2．8．2．1 Principles vacuum preloading method

2．8．2．2 Consolidation settlement

2．8．3 Project of Hang Jin Qu expressway, Xiao Shan city, Zhe Jiang-China

2．8．3．1 Soil profile

2．8．3．2 Ground treatment

2．8．3．3 Monitoring of lateral displacement

2．8．3．4 Fluctuation of water table level

2．9 CONCLUSIONS

CHAPTER THREE METHODOLOGY OF CONSOLIDATION

3．1 INTRODUCTION

3．2 PHYSICAL AND MECHANICAL PROPERTIES OF THE SOIL SAMPLES

3．3 PRINCIPLES OF VACUUM PRELOADING IN THREE-DIMENSIONAL CONSOLIDATION

3．4 CONSOLIDATION DUE TO VERTICAL AND RADIAL FLOW OF PORE WATER

3．5 METHODOLOGY

3．6 EXPERIMENTAL WORK

3．6．1 Sample preparation

3．6．2 Testing method

3．6．2．1 Undisturbed soil sample

3．6．2．2 Excess pore-water pressure

3．7 EFFECTS OF VACUUM PRELOADING ON THE PHYSICAL AND MECHANICAL PROPERTIES OF THE SOIL

3．7．1 Settlement and volumetric strain

3．7．2 Permeability anisotropy

3．7．3 Void ratio and the coefficient of secondary consolidation (creep)

3．7．4 Void ratio and effective stresses

3．8 CONCLUSIONS

CHAPTER FOUR CREEP BEHAVIOUR IN TRIAXIAL TESTS

4．1 GENERAL

4．2 PROGRAM OF DRAINED CREEP TESTS

4．3 DRAINED CREEP TESTS

4．3．1 Test results

4．3．1．1 Axial strain

4．3．1．2 Axial strain rate

4．3．1．3 volumetric strain

4．3．1．4 volumetric strain rate

4．3．2 Development of deviatoric strain with time

4．3．2．1 Empirical equation for deviatoric strain with time

4．3．2．2 Validation of the empirical equation

4．3．3 Development of volumetric strain with time

4．4 SUMMARIES AND CONCLUSIONS

CHAPTER FIVE MICROSTRUCTURE DEFORMATION MECHANISM OF FINE GRAINED SOILS

5．1 GENERAL

5．2 NATURE OF DAMAGE IN CLAYEY SOILS

5．3 ORIENTATION OF FINE-GRAINED SOIL

5．4 SOIL VOLUMETRIC VARIABLES

5．5 COMPUTER IMAGE PROCESSING SYSTEM (CIPS)

5．6 QUANTITATIVE INDICES

5．6．1 The order index: alignment entropy

5．6．2 Frequency distribution function of orientation of clay aggregates

5．7 APPLICATIONS

5．7．1 Assessment of the orientation of the soft clayey soil

5．8 QUANTITATIVE ANALYASIS OF MICROSTRUCTURE

5．8．1 Distribution of orientation angle

5．9 SUMMARIES AND CONCLUSSIONS

CHAPTER SIX CONCLUSIONS

6．1 SUMMARIES

6．2 CONCLUSSIONS

REFERENCES

APPENDIX (A)

APPENDIX (B)

APPENDIX (C)

APPENDIX (D)

ACKNOWLEDGEMENTS

PUBLICATIONS

发布时间: 2005-04-25

参考文献

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[2].潮差带区域水下真空预压技术研究[D]. 刘爱民.天津大学2013
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[4].水下真空预压中真空产生机制、预压加固机理及其应用技术研究[D]. 张敬.天津大学2007
[5].真空预压下塑料排水板有效影响范围的研究分析[D]. 高会强.华南理工大学2017
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[7].市政污泥的化学调理和真空预压联合作用固结机理及应用[D]. 占鑫杰.浙江大学2015

真空堆载联合预压软土地基加固机理研究

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