1st Edition
Assessing Loads on Silos and Other Bulk Storage Structures Research Applied to Practice
This comprehensive and unique work considers the various aspects involved in the behaviour of bulk storage structures. It is the accumulation of over 30 years of study, experiments and field measurements by the author, covering design, examination and evaluation of bulk storage structures. The subjects treated in this volume range from design, through operational behaviour, to failure and its prevention. The following areas are considered: theories of stresses and strains in particulate materials; material testing and evaluation for the prediction of a structure's loads and behaviour; methods for calculating loads and safety assessment; comparisons of field measurements with theoretical predictions; effects of non-ideal behaviour of stored materials; use of silo-related theories in geotechnical applications; measuring strains, deformations and pressure in operating structures; and case histories of silo problems, their causes and solutions. This title is highly valuable in informing professional engineers and researchers working in the fields of design, examination and evaluation of silos and bulk storage structures.
Foreword
Acknowledgement
1. The Objectives of This Book – Introduction References
2. The Effects of Stress on Particulate Materials, Measuring Stress-Related Materials Properties, and Typical Values of These Properties
2.1 Stress Equilibrium
2.2 Principal Stresses
2.3 The Mohr Stress Diagram
2.4 The Principle of Effective Stress
2.5 Direct Strains, Shear Strains and Principal Strains
2.6 The Unit Weight and Water Content of Particulate Materials
2.7 The Compression of Particulate Materials
2.8 Apparatus for Measuring Compression and Compressive Strains and the Stress Ratio Ko for Particulate Material Typical Results of Measurements
2.9 The Shear Strength and Shear Strain Behaviour of Particulate Materials
2.10 Typical Results of Shear Tests
2.11 Some Effects of Water Content, Temperature and Time Under Load on the Properties of Particulate Materials 2.11.1 Swelling Pressure in Grain
2.11.2 The Effects of Water Content on Properties of Grain and Similar Materials
2.11.3 The Effect of Temperature and Time of Loading on Ko
2.11.4 The Effects of Water Content, Temperature and Time Under Load on the Shear Strength Characteristics of Grain and Similar Materials
2.12 The Relationship Between the Angle of Repose and the Angle of Shearing Resistance
2.13 References
3. Simple Theories for Calculating Loads on Bulk Particulate Materials Storage Structures, Including Considerations of Safety
3.1 The Rankine Active, at Rest and Passive States and Corresponding Lateral Strains
3.2 The Coulomb Wedge Theory of Pressure on Retaining Walls
3.3 Frictional Transfer of Load from the Fill to the Silo Wall in a Cylindrical Silo
3.4 Frictional Transfer of Load to the Walls of a Conical Hopper
3.5 The Theoretical Value of K at the Walls of a Silo or Retaining Wall and the Condition for Sliding of Fill on an Inclined Hopper Wall
3.6 Theoretical Pressures on Reclaim Tunnels
3.7 Pressures During Rapid Filling of a Silo with a Fine Powder
3.7.1 The Effects of Rapid Filling
3.7.2 Empirical Approach
3.7.3 Theoretical Approach
3.8 Assessment of the Risk of Failure of a Silo
3.8.1 Definitions
3.8.2 A Hypothetical Example
3.8.3 An Acceptable Probability of Failure
3.8.4 Calculating the Probability of Failure
3.8.5 Assessing Demand D and Capacity C
3.8.5.1 Assessing the Demand D
3.8.5.2 Assessing the Capacity C
3.8.6 A Simple Example of Calculating pf
3.8.7 Conclusions
3.9 References
4. Correspondence Between Theory and Reality Illustrated by Measurements on Full Size Structures in Service
4.1 The Actual Value of K Behind a Bulk Materials Retaining Wall and in a Silo
4.2 Flow Patterns in Silos
4.3 Examples of Pressure Versus Depth Profiles in Silos Storing Coarse Materials, Including Pressures in Bottom Hoppers
4.3.1 Pressures on the Barrel and Hopper of a Reinforced Concrete Coal Silo
4.3.2 Pressures on the Hopper of a Small Bolted Steel Silo
4.3.3 Pressures at the Base of a Coal Staithe
4.3.4 Conclusions for Silos and Hoppers Filled with Coarse Materials
4.4 Examples of Pressure Versus Depth Profiles in Silos Storing Fine Powders, Including Pressures on Bottom Hoppers
4.4.1 Pressures on the Outer Wall of a Duocell Ring Silo Storing Cement Powder
4.4.2 Pressures on the Outer Wall of a Multi-Cell Silo Storing Pulverized Fuel Ash (Fly Ash)
4.4.3 Pressures on the Conical Hopper of a Steel Silo Storing Maize Starch
4.4.4 Pressures on the Inverted Conical Hopper of a Reinforced Concrete Silo Storing Cement Powder
4.4.5 Conclusions Regarding Pressures in Silos and Hoppers Storing Fine Powders
4.5 Measured Pressures on Reclaim Tunnels
4.6 Measured Strains During Rapid Filling of a Silo with a Fine Powder
4.7 Pressures Close to a Silo Outlet at Start of Emptying
4.7.1 Previous Model Tests
4.7.2 Field Strain Measurements
4.7.3 Conclusions
4.8 Overall Conclusion
4.9 References
5. The Influence of Non-Ideal Material Behaviour and Various Secondary Effects on Loading on Containments
5.1 Effects Arising from the Development of Cohesion
5.2 Effects of Eccentric Filling and Emptying
5.3 Effects of Varying Horizontal Pressure
5.3.1 Examples of Observed Non-Uniform Pressures and Their Effect on Bending Stresses
5.3.2 Formalized Horizontal Pressure Distributions
5.4 Loading Induced by External Temperature Changes
5.4.1 Characteristics of Temperature-Induced Loading
5.4.2 Calculating Temperature Surcharge Pressures
5.4.3 Calculation of Thermal Bending Moments
5.4.4 Temperature Surcharge Pressures in Reinforced Concrete Silos
5.4.5 Characteristics of Thermal Bending
5.4.6 Effect of Outside Insulation on Temperature Changes in Silo Walls
5.4.7 Design Pressures and Wall Loads, Including Effects of Loss of Arching and Temperature Changes
5.5 The Effects of Water Content on Silo Loading
5.6 Dynamic Effects, Silo Quaking and Trilling
5.7 Overall Conclusions
5.8 References
6. Application of Janssen-Type Theory to Other Engineering Problems
6.1 Loads on Buried Pipes and Conduits
6.2 Stresses in Narrow Cores and Core-Trenches in Earth and Rockfill Dams
6.3 Underground Ore Passes
6.3.1 The Janssen Equation for an Inclined Ore Pass
6.3.2 Tests on Model Ore Passes
6.3.3 Impact Pressures on the Closure Gate of an Ore Pass
6.3.4 Conclusions
6.4 Stresses in Backfill Placed in Inclined Underground Stopes
6.5 References
7. Methods Used for Instrumenting Full Size Operational Structures
7.1 Temperature Measurements Using Thermocouples
7.2 Measuring Strains in Silos Using Strain Gauges
7.3 Measuring Strains in Reinforced Concrete Silos
7.4 The Performance of Pressure Cells
7.5 Two Simple Designs for Accurate Pressure Cells
7.5.1 The Zero Strain Pressure Cell
7.5.2 The Stiffened Face Pressure Cell
7.6 Calibrating Pressure Cells
7.7 Mounting Pressure Cells in a Retaining Structure
7.8 References
8. Some Instructive Case Histories
8.1 Collapse of a Welded Plane Plate Silo as a Result of Eccentric Emptying
8.1.1 Events Leading to Failure
8.1.2 Analysis of Failure and Comparison with a Different Type of Silo
8.2 Partial Failures of Bolted Corrugated Steel Silos Storing Canola Oil Seed
8.2.1 The Stored Material and Silos
8.2.2. The Problems
8.2.3 Causes of the Problems
8.2.4 The Outcome
8.3 Overloading of Reinforced Concrete Coal Storage Silos
8.3.1 The Overloading
8.3.2 The Investigation of the Effects of Overloading
8.3.3 The Outcome 8.4 Investigation of Cracking of Reinforced Concrete Rail Load-Out Silo for Export Coal 8.4.1 The Cracking and its Assessment
8.4.2 Measurement of Strains
8.4.3 Results of Strain Measurements
8.4.4 Conclusion
8.5 Failure of Reinforced Concrete Multi-Cell Cement Storage Silo
8.5.1 Signs of Imminent Failure
8.5.2 The Silo Design
8.5.3 Construction Faults
8.5.4 The Failure Occurs
8.6 Strengthening of Reinforced Concrete Multi-Cell Cement Storage Silo
8.6.1 Events Leading to Design Review
8.6.2 The Design and the Review
8.6.3 Observations During the Strengthening Process
8.7 Investigation of Poorly Managed Battery of Reinforced Concrete Coal Storage Silos
8.7.1 The Appearance of the Silos
8.7.2 The Investigation of the Silos’ Condition
8.8 References
9. Full List of Research Publications on which This Book is Based
10. List of Symbols
11. List of Figures
12. List of Plates
Biography
Geoffrey Blight completed his Bachelor and Master degrees at the University of the Witwatersrand, Johannesburg, and his PhD at Imperial College, London. There he carried out some of the earliest research on the mechanics of unsaturated soils, under the supervision of the legendary Alan Bishop. His early work, published jointly with Bishop and others in 1960, 1961 and 1963, provided data that is still being used by new generations of researchers on unsaturated soil behaviour. He soon became interested in the application of unsaturated soil mechanics to residual soils and mine waste and has published extensively in these areas. He has also applied unsaturated soil mechanics principles in related fields such as concrete and silo technology. He was a member of the International Society for Soil Mechanics and Foundation Engineering’s Technical Committee on the Properties of Tropical and Residual Soils from 1982 to 1997 and served as Chairman from 1994 to 1997. He edited and co-authored the first (1997) edition of "Mechanics of residual soils", which was produced during his Chairmanship. In addition to the second edition of Mechanics of residual soils (2012), he has also authored or co-authored the books: "Assessing loads on silos and other bulk storage structures" (2006), "Geotechnical engineering for mine waste storage facilities" (2010), and "Alkali-aggregate reaction and structural damage to concrete" (2011), all published by CRC Press/Balkema. He passed away in November 2013.
