Soils can rarely be described as ideally elastic or perfectly plastic and yet simple elastic and plastic models form the basis for the most traditional geotechnical engineering calculations. With the advent of cheap powerful computers the possibility of performing analyses based on more realistic models has become widely available. One of the aims of this book is to describe the basic ingredients of a family of simple elastic-plastic models of soil behaviour and to demonstrate how such models can be used in numerical analyses. Such numerical analyses are often regarded as mysterious black boxes but a proper appreciation of their worth requires an understanding of the numerical models on which they are based. Though the models on which this book concentrates are simple, understanding of these will indicate the ways in which more sophisticated models will perform.

Soil Behaviour and Critical State Soil Mechanics

The extraction of groundwater can generate land subsidence by causing the compaction of susceptible aquifer systems, typically unconsolidated alluvial or basin-fill aquifer systems comprising aquifers and aquitards. Various ground-based and remotely sensed methods are used to measure and map subsidence. Many areas of subsidence caused by groundwater pumping have been identified and monitored, and corrective measures to slow or halt subsidence have been devised. Two principal means are used to mitigate subsidence caused by groundwater withdrawal—reduction of groundwater withdrawal, and artificial recharge. Analysis and simulation of aquifer-system compaction follow from the basic relations between head, stress, compressibility, and groundwater flow and are addressed primarily using two approaches—one based on conventional groundwater flow theory and one based on linear poroelasticity theory. Research and development to improve the assessment and analysis of aquifer-system compaction, the accompanying subsidence and potential ground ruptures are needed in the topic areas of the hydromechanical behavior of aquitards, the role of horizontal deformation, the application of differential synthetic aperture radar interferometry, and the regional-scale simulation of coupled groundwater flow and aquifer-system deformation to support resource management and hazard mitigation measures.

Review: Regional land subsidence accompanying groundwater extraction

The driven monopile is currently the preferred foundation type for most offshore wind farms. While the static capacity of the monopile is important, a safe design must also address issues of accumulated rotation and changes in stiffness after long-term cyclic loading. Design guidance on this issue is limited. To address this, a series of laboratory tests were conducted where a stiff pile in drained sand was subjected to between 8000 and 60 000 cycles of combined moment and horizontal loading. A typical design for an offshore wind turbine monopile was used as a basis for the study, to ensure that pile dimensions and loading ranges were realistic. A complete non-dimensional framework for stiff piles in sand is presented, and applied to interpret the test results. The accumulated rotation was found to be dependent on relative density, and was strongly affected by the characteristics of the applied cyclic load. Particular loading characteristics were found to cause a significant increase in the accumulated ro...

https://www.icevirtuallibrary.com/doi/pdf/10.1680/geot.7.00196

Response of stiff piles in sand to long-term cyclic lateral loading

http://research.me.mtu.edu/abstracts/Odegard%20-%20Nanoclay-%20modified%20asphalt%20materials.pdf

Nanoclay-modified asphalt materials: Preparation and characterization

This paper is concerned with micromechanics of Schneebeli material specimens composed of wooden roller stacks. Several laboratory tests are carried out to analyse the material behaviour under complex loading conditions, involving loading–unloading cycles and principal axes rotations. In order to characterize micromechanical deformation features and structure evolution, a series of pictures is taken during loading. Pictures are then digitized using a stereo device, obtaining the position of each roller. Starting from these data a number of computer programs, conceived for the purpose, allow us to measure micromechanical variables and to analyse their evolution.

In the following, after the description of the devices employed in this research, macromechanical results are analysed to evaluate the reliability of the laboratory model. Then, local variables are introduced and the use of continuum mechanics to describe granular materials behaviour is discussed. Finally, the evolution of local kinematic variables is described, focusing interest on the evolution of specimen anisotropy. © 1997 by John Wiley & Sons, Ltd. Mech. cohesive-frictional mater. 2, 121–163 (1997)

Experimental micromechanical analysis of a 2D granular material: relation between structure evolution and loading path

Field and laboratory observations of seismic settlements of shallow foundations on granular soils that are not attributable to changes in density or liquefaction are explained in terms of seismic degradation of bearing capacity. Limit analysis using a Coulomb‐type mechanism including inertial forces in the soil and on the footing gives expressions for seismic bearing capacity factors that are directly related to their static counterparts. Comparison of the two depicts clearly the rapid deterioration of the overall foundation capacity with increasing acceleration. Such periodic inertial fluidization causes finite settlements that are possible even in moderate earthquakes. Reduction in foundation capacity is due to both the seismic degradation of soil strength and the lateral inertial forces transmitted by shear to the foundation through the structure and any surcharge. A straightforward sliding‐block procedure with examples is also presented for computing these settlements due to loss of bearing capacity f...

Seismic bearing capacity and settlements of foundations

A practical approach to grain shape quantification

Free‐field limit analysis of a homogeneous layer of dry soil excited by uniform horizontal and vertical acceleration components leads to simple equations describing various stages of inertial shear fluidization. Orientations of potential shear flow spread out from the initial slip planes developed at moderate acceleration ratios, less than 0.3, until the general fluidization state is reached, when a broad band of planes are mobilized throughout the layer. In these directions, the layer then behaves as a viscous fluid. For loose saturated soils, it is postulated that initial fluidization will initiate liquefaction, and therefore the free‐field solution for this neutral case may serve as a useful benchmark for estimating liquefaction trigger accelerations. All intermediate stages, both active and passive, from static conditions to general dynamic fluidization are expressed. The solution seems relatively insensitive to boundary conditions, since the free‐field lateral pressures derived do not differ signific...

Dynamic Fluidization of Soils

This paper derives the seismic bearing capacity factors for a C- phi soil within the framework of the Mohr-Coulomb theory. Horizontal and vertical accelerations, and the effects of: a) inertia forces of the soil both below and above the footing; and b) the applied loads are all taken into consideration. The method is used to derive the ultimate seismic bearing capacity for a square footing 2.5m wide founded 1.0m below a homogeneous soil with C (soil cohesion parameter) = 7 kPa, phi = 25 degrees and a unit weight of 18 kN per cubic metre. The results indicate that the horizontal accelerations as well as soil cohesion and vertical accelerations affect the bearing capacity coefficients considerably.

Seismic bearing capacity of soils

A feasibility study was performed on using xanthan gum and guar gum, two biopolymers that are naturally occurring and inexpensive, to stabilize mine tailings (MT). The simple fall cone method was adopted to evaluate the liquid limit and undrained shear strength of sun-dried MT mixed with xanthan gum or guar gum solutions at different concentrations. Environmental scanning electron microscopy (ESEM) imaging was also conducted to study the microstructure of the biopolymer-MT system. The results indicate that the inclusion of xanthan gum or guar gum increases both the liquid limit and the undrained shear strength of the MT, higher biopolymer concentrations leading to greater increases. The increase of the liquid limit and undrained shear strength of the MT mixed with a biopolymer solution is mainly attributable to the high viscosity of the biopolymer pore fluid and the bonding between the biopolymer and the MT particles. Guar gum is more effective than xanthan gum in increasing the liquid limit and u...

Muniram Budhu

Papers

Seismic bearing capacity and settlements of foundations

A practical approach to grain shape quantification

Dynamic Fluidization of Soils

Seismic bearing capacity of soils

Biopolymer Stabilization of Mine Tailings