The size and shape of soil particles reflect the formation history of the grains. In turn, the macroscale behavior of the soil mass results from particle level interactions which are affected by particle shape. Sphericity, roundness, and smoothness characterize different scales associated with particle shape. New experimental data and results from published studies are gathered into two databases to explore the effects of particle shape on packing density and on the small-to-large strain mechanical properties of sandy soils. In agreement with previous studies, these data confirm that increased angularity or eccentricity produces an increase in emax and emin. Furthermore, the data show that increasing particle irregularity causes a decrease in stiffness yet heightened sensitivity to the state of stress; an increase in compressibility under zero-lateral strain loading; an increase in the critical state friction angle cs; and an increase in the intercept of the critical state line there is a weak effect on the slope . Therefore, particle shape emerges as a significant soil index property that needs to be properly characterized and documented, particularly in clean sands and gravels. The systematic assessment of particle shape will lead to a better understanding of sand behavior.

Particle Shape Effects on Packing Density, Stiffness, and Strength: Natural and Crushed Sands

The GPR (Ground Penetrating Radar) conference in Hong Kong year 2016 marked the 30th anniversary of the initial meeting in Tifton, Georgia, USA on 1986. The conference has been being a bi-annual event and has been hosted by sixteen cities from four continents. Throughout these 30 years, researchers and practitioners witnessed the analog paper printout to digital era that enables very efficient collection, processing and 3D imaging of large amount of data required in GPR imaging in infrastructure. GPR has systematically progressed forward from “Locating and Testing” to “Imaging and Diagnosis” with the Holy Grail of ’Seeing the unseen’ becoming a reality. This paper reviews the latest development of the GPR’s primary infrastructure applications, namely buildings, pavements, bridges, tunnel liners, geotechnical and buried utilities. We review both the ability to assess structure as built character and the ability to indicate the state of deterioration. Finally, we outline the path to a more rigorous development in terms of standardization, accreditation, and procurement policy.

A review of Ground Penetrating Radar application in civil engineering: A 30-year journey from Locating and Testing to Imaging and Diagnosis

[1] The competing hypotheses for gas hydrate formation at the particle scale in sediments describe processes of pore-filling, frame-building, or cementation. New measurements of compressional (VP) and shear wave (VS) velocities in fine-grained sands subjected to low confinement and monitored during formation of tetrahydrofuran hydrate indicate that hydrate nucleates in the pore space (presumably at grain boundaries) and grows with limited impact on the sediment shear stiffness, VP, and VS until crystals begin to interact with the granular skeleton at ∼40% hydrate concentration. VS increases significantly more than VP at higher hydrate concentrations, reflecting larger changes in the specimen's shear stiffness than its bulk stiffness. The results indicate that seismic velocities and/or their ratio (VP/VS) have limited capability for locating hydrate or constraining hydrate concentrations.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2005GL022607

Compressional and shear wave velocities in uncemented sediment containing gas hydrate

The thermal conductivity of the different soil components—mineral, liquids and air—varies across two or- ders of magnitude. Two studies are implemented to explore the role of contacts in heat conduction in dry granular mate- rials. The first set of experiments is designed to elucidate heat transfer at contacts, and it is complemented with a numeri- cally based inversion analysis for different local and boun- dary conditions to extract proper material parameters. Then, the thermal conductivity of dry soils is measured at different packing densities to address the relevance of coordination number and particle shape effects. Together, both studies confirm the prevailing effect of contact quality and number of contacts per unite volume on heat conduction in granular materials. Interparticle contacts and the presence of liquids in pores play a critical role in heat transfer, and determine the ordered sequence of typical thermal conductivity values: kair < kdry-soil < kwater < ksaturated-soil < kmineral.

Fundamental study of thermal conduction in dry soils

Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough

PART ONE: INTRODUCTION. Chapter 1: Materials And Scales. PART TWO: PARTICULATE MATERIALS. Chapter 2: Characterization Of Particles And Particulate Media. Chapter 3: Particle-Fluid Interactions. Chapter 4: Load-Deformation Behavior. Chapter 5: Conduction And Diffusion - Soil Behavior. PART THREE: ELASTIC WAVES AND SOILS. Chapter 6: Elastic Waves In The Continuum. Chapter 7: Elastic Waves In Particulate Media. Chapter 8: Velocity And Attenuation: Data And Empirical Relations. Chapter 9: Laboratory Measurement Methods. PART FOUR: ELECTROMAGNETIC WAVES AND SOILS. Chapter 10: Electromagnetism. Chapter 11: Electromagnetic Properties: Physical Description And Analytical Models. Chapter 12: Electromagnetic Properties: Data And Empirical Relations. Chapter 13: Laboratory Measurement Methods. PART FIVE: PROCESS MONITORING. Chapter 14: Process Monitoring With Elastic And Electromagnetic Waves. APPENDIX A: MATHEMATICAL CONCEPTS. REFERENCES.

Moheb A. Fam

Papers

Soils and Waves: Particulate Materials Behavior, Characterization and Process Monitoring

Drilling in mudrocks: rock behavior issues

Assessing and Monitoring the Geo-Environment

Physical And Mechanical Properties of Two Shales