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

A kinematic method of slices has been used in this article to deal with the stability problems of strip foundations subjected to uplift loads. The method is based on the upper bound theorem of limit analysis and satisfies the kinematic admissiblility of the chosen collapse mechanism. Assuming the global rupture surface as an arc of logarithmic spiral, uplift factors F c , F q and F y separately for the effects of cohesion, surcharge and density have been determined. The effect of the yielding of soil mass with partial soil shear strength parameters along the slice interfaces on the results has been examined. The ultimate uplift capacity increases with increase in soil shear strength along the interfaces of slices. The results compare reasonably well with the various existing theories and reported experimental tests data.

Kinematic slices approach for uplift analysis of strip foundations

In the presence of pseudo-static horizontal earthquake body forces and horizontal seepage forces, the vertical pullout capacity of horizontal plate anchors buried in sand has been determined by using the lower bound theorem of the limit analysis in combination with finite elements and linear optimisation. The variations of the pullout factor (a) Fγ with, and (b) the factor Fq with αh, have been established for different embedment ratio of the anchor plate and the friction angle of sand. It is noted that the pullout capacity decreases continuously with increases in the values of αh and . The pullout capacity becomes continuously higher for greater values of the embedment ratio and interface friction angle. The failure patterns have been found to become unsymmetrical in the presence of horizontal body forces.

Vertical pullout capacity of horizontal anchor plates in the presence of seismic and seepage forces

By using the axisymmetric quasi-lower bound finite-element limit analysis, the bearing capacity factors Ncp and Nγqp have been computed for axially loaded piles, with the shaft embedded in a fully cohesive soil medium and the tip placed over cohesive frictional soil strata. The results were obtained for various combinations of L/D, ϕl, and cl/cu; the subscripts l and u refer to lower and upper soil strata, respectively. The factors Ncp and Nγqp increase continuously with increases in L/D and ϕl; the rate of increase of Ncp and Nγqp with L/D, however, decreases with an increase in L/D. For cl/cu>100, the factor Ncp hardly depends on L/D.

Jyant Kumar

Papers

Kinematic slices approach for uplift analysis of strip foundations

Vertical pullout capacity of horizontal anchor plates in the presence of seismic and seepage forces

Bearing Capacity of Piles in Soft Clay Underlaid by Cohesive Frictional Soil

Slope Stability Calculations Using Limit Analysis

Ultimate bearing capacity of strip and circular foundations using power type yield criterion using the method of stress characteristics