Recursos de colección

Caltech Authors (142.336 recursos)

Repository of works by Caltech published authors.

Group = Soil Mechanics Laboratory

Mostrando recursos 1 - 17 de 17

  1. Applications of Plasticity Theory to Selected Problems in Soil Mechanics

    Baligh, Mohsen Mohamed
    Two topics in plane strain perfect plasticity are studied using the method of characteristics. The first is the steady-state indentation of an infinite medium by either a rigid wedge having a triangular cross section or a smooth plate inclined to the direction of motion. Solutions are exact and results include deformation patterns and forces of resistance; the latter are also applicable for the case of incipient failure. Experiments on sharp wedges in clay, where forces and deformations are recorded, showed a good agreement with the mechanism of cutting assumed by the theory; on the other hand the indentation process for blunt wedges...

  2. Cyclic Lateral Loading of Piles; Analysis of Centrifuge Tests

    Scott, Ronald F.
    In two previous reports (6,7) results were given of a number of cyclic lateral load tests on model piles loaded in a centrifuge. The tests results were obtained in the form of loads and deflections at the top of the pile and readings from strain gauges distributed down the pile; the latter are interpreted in the form of moments. In contrast to field tests, the centrifuge pile experiments are carried out in an extremely uniform medium consisting, in the tests discussed, of dry and wet sand in two test series. The result of this soil uniformity is that moment readings can be...

  3. Centrifuge studies of cyclic lateral load-displacement behavior of single piles

    Scott, Ronald F.
    A meeting was held at the California Institute of Technology, February 26, 1976, between a group representing the American Petroleum Institute (API), and Professors K. L. Lee of UCLA and R. F. Scott of Caltech. Problems relating to the dynamic performance of offshore structures were discussed, in particular with respect to their interaction with foundation soils, and the hazards related to the sliding of those soils on modest slopes. Attention was given to both wave- and earthquake-generated forces, especially on pile-supported structures, with particular consideration directed towards the latter. Although the behavior of structures at a wide variety of locations...

  4. Centrifuge Studies of Cyclic Lateral Load-Displacement Behavior of Single Piles

    Scott, Ronald F.
    In the period following the completion of the previous report of December 1977 and the end of the contract on OSAPR Project 8 with California Institute of Technology, additional pile loading tests were conducted. Two different test series were followed through: additional load-unload cyclic tests again in simulation of the Mustang Island (MI) tests and pile vibration tests. The reasons for the first series were: (a) the model pile dimensions originally chosen for the Mustang Island simulation did not correctly represent either the El of the prototype pile, nor its width; and (b) it was desired to perform the tests in a...

  5. Axially-loaded centrifuge pile tests

    Christenson, John E.; Scott, Ronald F.
    This report concerns investigations of the behavior of piles under axial loading using centrifugal modeling and t-z analysis. The results of five centrifuge model pile tests on instrumented piles are presented. The present chapter puts this work into perspective, both with relation to current practical concerns with pile performance and existing analytical techniques.

  6. Analysis of Centrifuge Pile Tests; Simulation of Pile-Driving

    Scott, Ronald F.
    Previous studies on the centrifuge have been directed towards simulating the behavior of a laterally-loaded pile in fine, dry and saturated sand. After data had been obtained on the model pile, attention was turned to modelling the soil-pile interaction behavior. Since the Winkler [continuous reaction elements (springs) distributed along the pile length] foundation representation is the simplest that can be adduced, and, moreover, has been found to give adequate results for design in a variety of foundation problems, attempts were made to extract a Winkler type of function from the model pile test results. The pile response is obtained from the output of...

  7. Application of plasticity theory to soil behavior : a new sand model

    Bardet, Jean-Pierre
    The representation of rheological soil behavior by constitutive equations is a now branch of soil mechanics which has been expanding for 30 years. Based on continuum mechanics, numerical methods (finite elements) and experimental techniques, this now discipline allows practicing engineers to solve complex geotechnical problems. Although all soils are constituted of discrete mineral particles, forces and displacements within them are represented by continuous stresses and strains. Most stress-strain relationships, which describe the soil behavior, are derived from plasticity theory. Originated for metals, the conventional plasticity is presented and illustrated simultaneously with a metal and a soil model. Each plasticity concept...

  8. Physical scale modeling of geotechnical structures at one-G

    Gibson, Andrew Douglas
    The use of physical scale modeling techniques for geotechnical applications is investigated. The scaling laws to relate a prototype structure to a model are developed for the centrifuge modeling technique and for the laboratory (or one-g) environment. A theory based on critical or steady state concepts for the constitutive scaling of the behavior of the soil in a one-g model is investigated. A series of one-g models of varying configurations was constructed in a laminar box and subjected to earthquake like motions on a shake table. A total of 73 tests was performed. Most tests were constructed of saturated Nevada...

  9. Seismic deformation analysis of earth dams : a simplified method

    Yan, Liping
    Motivated by the dynamic behaviors of two earth dams, named La Villita Dam and El Infiernillo Dam in Mexico, during an earthquake on September 19, 1985, a seismic deformation analysis is elaborated in this study. Firstly, a simplified method is developed by applying a rigid block model to study the major characteristics of an earth dam during an earthquake and calculate the seismic permanent displacements. In this method, the sliding mass is modeled as a rigid body along a well defined surface. Both inclined plane and circular arc slip surfaces are considered. Secondly, in order to validate the numerical procedure of the...

  10. Numerical simulations of two-dimensional saturated granular media

    Tan, Phalkun
    The liquefaction phenomenon in soil has been studied in great detail during the past 20 years. The need to understand this phenomenon has been emphasized by the extent of the damages resulting from soil liquefaction during earthquakes. Although an overall explanation exists for this phenomenon through the concept of effective. stress, the basic mechanism of loss of strength of the soil skeleton has not been thoroughly examined and remains unclear. The present study proposes a numerical model for simulations of the behavior of saturated granular media. The model was developed with two main objectives: 1. To represent the mechanical response of an...

  11. Soil stress field around driven piles

    Allard, Marie-Agnes
    The description, equipment, and results of a series of pile-driving experiments conducted in a centrifuge using a model pile driven in dry sand are presented. The work was conceived on the basis of the modelling of a soil-structure system under an artificially generated gravitational field, and motivated by the need for experimental data for a better understanding of the complex phenomena involved in the pile-soil interaction during driving. The behavior of the pile itself has been the focus of more attention in the past, but few full-scale or model experimental results have been obtained to the present concerning the soil stress...

  12. Failure of slopes

    Burridge, Paul Brian
    The dynamic mechanism of slope failure is studied both experimentally and analytically to establish the spatial and temporal process of failure initiation and propagation during collapse of a natural or man-made slope. Model slopes, constructed of a brittle cemented sand material, are tested to collapse in a geotechnical centrifuge and the dynamics of failure recorded by motion picture film and mechanical detectors within the slope specimen. Shear failure is observed to initiate at the toe and propagate rapidly to the crest in the presence of crest tension cracking. A finite difference approach is taken to numerically solve the plane strain slope stability...

  13. Two-phase soil study: A. Finite strain consolidation, B. Centrifuge scaling considerations

    Tan, Thiam-Soon
    Two different aspects of the behavior of soil as a two-phase medium are studied, namely, the consolidation of soil and scaling relations for soils in centrifuge testing. PART A -- First a consistent approach is presented that unifies all current theories of consolidation of soil. For one-dimensional finite strain consolidation, a Lagrangian finite element scheme is then given and tested against three different experiments and found to give consistent results. For a quick solution to a particular problem, the regular perturbation method applied to the formulation in which the dependent variable is the natural strain is shown to give the most...

  14. Experimental studies of dynamic response of foundations

    Hushmand, Behnam
    An investigation was made into the behavior of rigid foundations and structures resting on the surface or embedded in a cohesionless soil and subjected to transient active or passive excitations and forced vibrations using the centrifuge modeling technique. The investigation was aimed at studying both low and high amplitude vibrations of foundations under machine type loadings, earthquake or wave induced vibrations, and other sources of dynamic loads. Rigid "prototype" foundations of mass and size comparable to foundations of a low rise building were simulated in the centrifuge at a centrifugal acceleration of 50g. Rigid model structures (aluminum towers) attached to...

  15. Dynamic centrifuge testing of cantilever retaining walls

    Ortiz, L. Alexander
    An investigation was made into the behavior of flexible cantilever walls retaining a cohesionless soil backfill and subjected to earthquake-type dynamic excitations using the centrifuge modelling technique. The study was motivated by the abundant observations of earth retaining structure damage and failures documented in earthquake damage reports. The "prototype" typical walls were designed using the traditional Mononobe-Okabe dynamic lateral earth pressure theory, were properly scaled for use in the centrifuge at 50 g's, and were subjected to lateral earthquake-like motions which were considered to be of realistic levels. The walls were amply instrumented with pressure and displacement transducers, accelerometers, and strain...

  16. Study of slope instability in the ocean floor

    Scott, Ronald F.; Zuckerman, Kenneth A.
    There are three sections to the report: (a) ocean floor soil types and characteristics; (b) stability analysis of submarine slopes; and (c) discussion of problems, w-ith conclusions and recommendations. in the first section the physical and mechanical properties of the soils encountered in various types of ocean-floor terrain are described and summarized in tables and diagrams. The application of conventional subacrial slope stability analyses to ocean-floor soils and their environment is examined in the second section. Some aspects of the stability of under consolidated soils forming in areas of rapid deposition are given particular attention. Following a summary of the...

  17. A study of high-frequency strong ground motion from the San Fernando earthquake

    Berrill, John Beauchamp
    This thesis describes an investigation of the attenuation of strong earthquake ground motion in the 0. 4 to 16 Hz frequency band during the M=6.4, February 9, 1971, San Fernando, California earthquake. It is found that Fourier amplitudes of ground acceleration decay according to a simple expression incorporating a geometric spreading term, and a material attenuation term with constant specific attenuation Q. The scatter in the amplitude data about an expected level given by the simple decay expression is nearly constant with respect to both frequency and focal distance. Fourier amplitudes of acceleration corrected to a reference hypocentral distance agree...

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