PART 1 DEALS WITH THE DYNAMIC ASPECTS OF THE SUBJECT: MATHEMATICAL ANALYSIS OF SYSTEMS SUBJECTED TO INDEPENDENT VIBRATIONS BY MEANS OF MATHEMATICAL MODELS. THE ANALYTICAL SYSTEMS USED ARE NON-LINEAR SYSTEMS, HYDRODYNAMICS AND NUMERICAL METHODS. PART 2 EXAMINES SEISMIC MOVEMENTS, THE DYNAMIC BEHAVIOUR OF STRUCTURES AND THE BASIC CONCEPTS OF THE SEISMIC DESIGN OF STRUCTURES.

Fundamentals of earthquake engineering

Soils that exhibit nonassociated flow may, according to stability postulates by Drucker and by Hill, become unstable when exposed to certain stress paths inside the failure surface. Series of conventional triaxial tests on fully saturated and on partly saturated specimens were performed under drained and undrained conditions to study the regions of stable and unstable behavior. For specimens that compress and have degrees of saturation higher than critical, undrained conditions lead to effective stress paths directed within the region of potential instability, and instability was observed provided the yield surface opens up in the outward direction of the hydrostatic axis. Thus, instability occurs inside the failure surface. Instability is not synonymous with failure, although both may lead to catastrophic events. The location of the instability line is discussed. Examples of a shallow submarine slope and a nearly fully saturated steeper slope representing a tailings dam, which both should remain stable a...

Closure of "Static Instability and Liquefaction of Loose Fine Sandy Slopes"

During the last 30 years various researchers have proposed approximate techniques to estimate the uplift capacity of soil anchors. As the majority of past research has been experimentally based, much current design practice is based on empiricism. Somewhat surprisingly, very few numerical analyses have been performed to determine the ultimate pullout loads of anchors. This paper presents the results of a rigorous numerical study to estimate the ultimate pullout load for vertical and horizontal plate anchors in frictional soils. Rigorous bounds have been obtained using two numerical procedures that are based on finite element formulations of the upper and lower bound theorems of limit analysis. For comparison purposes, numerical estimates of the break-out factor have also been obtained using the more conventional displacement finite element method. Results are presented in the familiar form of break-out factors based on various soil strength profiles and geometries and are compared with existing numerical ...

The ultimate pullout capacity of anchors in frictional soils

The magnitude of the passive earth pressure that resists the movement of a structure is controlled by the amount the structure moves and the direction in which it moves, strength and stiffness of the soil that resists its movement, friction or adhesion on the interface between the structure and soil, and shape of the structure. The Log Spiral Theory, corrected for 3D effects, provides an accurate means of computing ultimate passive pressures. A hyperbolic expression, together with estimated values of soil modulus and ultimate resistance, provides a means of estimating the relationship between structural movement and passive resistance. It is essential that the soil strength and stiffness used in making these estimates should be appropriate for the soil and the drainage conditions involved. The results of an undrained passive pressure load test in stiff sandy silt and a drained passive pressure load test in well-graded gravel are compared with passive pressures computed using the methods discussed. Reasonable agreement between the calculated and measured values shows that the Log Spiral Theory, corrected for 3D effects, and the hyperbolic load-deflection relationship provide an adequate means of estimating passive resistance for a wide range of conditions.

Passive earth pressures : Theories and tests

Numerical limit analysis solutions for the bearing capacity factor Nγ


 
 This study presents a numerical solution for determining the limiting uniform normal pressure acting horizontally behind cohesive-frictional backfill material in a deep contiguous piled wall. At this limiting pressure, the soil tends to flow out in gaps between a series of vertical piles placed at a certain uniform horizontal spacing.
 
 
 
 The lower and upper bound plane strain finite element limit analysis (FELA) has been carried out for this purpose. The Mohr-Coulomb failure criterion, using an associated flow rule, was employed to impose the yield condition in the soil mass.
 
 
 
 A parametric study was carried out to obtain the magnitude of the non-dimensional limiting lateral resistance (F/cD) as a function of normalized pile spacing (S/D), the friction angle of soils (ϕ), and the adhesion factor (δ) at the soil-pile interface; here, F refers to the lateral normal resistance (force) per unit length offered by the pile, S forms the clear spacing between piles, D is the diameter of the pile and c is soil cohesion. The impact of the different parameters on the failure mechanisms has been examined comprehensively.
 
 
 
 The lateral resistance (F/cD) offered by the piles increases generally with a decrease in the spacing between the piles. The magnitude of F/cD increases further with an increase in the values of ϕ and δ.


https://opencivilengineeringjournal.com/VOLUME/16/ELOCATOR/e187414952209080/PDF/

Stability Charts for Limiting Horizontal Normal Pressure on Cohesive-frictional Backfill for Deep Contiguous Piled Walls

This study presents a computational methodology for solving axisymmetric stability problems in rock mechanics by using the finite element lower bound limit analysis. The generalized Hoek and Brown ...

Lower bound limit analysis using nonlinear optimization for solving axisymmetric problems using Hoek-Brown yield criterion

Bearing capacity of strip and circular footing on layered sand with geogrid at the interface

Seismic bearing capacity of foundations on sloping ground using power-type yield criteria

Three different transformation techniques, namely, (i)w-c, (ii) w-k and (iii) tau-p, has been employed for generating multimodal dispersion images on the basis of multi-channel analysis of surface waves (MASW) data recorded in distance-time domain; here w= circular frequency, c = phase velocity, tau = time intercept, p = phase slowness (1/c) and k = wavenumber. All the three methods have been first clearly described. The results from these three different transforms have been examined by using synthetic as well as field data obtained from field tests using 48 geophones. The effect of sensor spread length (X) and geophone numbers (M) on multimodal dispersion images were examined. The solutions from these three transforms were found to match generally well with each other. The w-c transform has been noted to provide the most clarity since it does not require either high sampling rate as normally needed for the tau-p method or inclusion of the zero padding of the data in a distance domain for the w-k approach. The paper will be useful since it not only describes the methods, but it brings out simultaneously their merits in implementation and for generating the dispersion images.

Jyant Kumar

Papers

Stability Charts for Limiting Horizontal Normal Pressure on Cohesive-frictional Backfill for Deep Contiguous Piled Walls

Lower bound limit analysis using nonlinear optimization for solving axisymmetric problems using Hoek-Brown yield criterion

Bearing capacity of strip and circular footing on layered sand with geogrid at the interface

Seismic bearing capacity of foundations on sloping ground using power-type yield criteria

Multimodal phase velocity-frequency dispersion images using different MASW transformation techniques