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A Caltech Library Repository Feedhttp://www.rssboard.org/rss-specificationpython-feedgenenWed, 07 Aug 2024 18:08:21 -0700Study of slope instability in the ocean floor
https://resolver.caltech.edu/CaltechEERL:1970.SML.1970.001
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 conclusions reached in the study, some detailed recommendations regarding future studies and experimental work are given in the final section of the report.https://resolver.caltech.edu/CaltechEERL:1970.SML.1970.001A study of high-frequency strong ground motion from the San Fernando earthquake
https://resolver.caltech.edu/CaltechEERL:1975.SML.1975.001
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 well with those determined by a two-parameter source model of the San Fernando earthquake. Focusing of energy to the south by the southward propagating rupture is observed at frequencies below 8 Hz. The propagation of rupture was incoherent with respect to higher frequency components.
The relationship between intensity of ground motion and site geology is examined. It is found that while, -in general, sedimentary sites were accelerated more strongly than basement rock sites, no clear difference could be found between sedimentary sites classified as "soft" by Trifunac and Brady (1975) (generally recent alluvium) and those classified as having "medium" soil stiffness, generally consisting of older alluvium and sedimentary rock. The difference between amplitudes recorded on basement rock and sediments is more complex. In general, smoothed amplitude spectra from accelerograms recorded on basement rock are lower than smoothed amplitudes at corresponding sedimentary sites. However, basement site spectra show marked isolated peaks, as high as those from sedimentary sites at similar distances. This is attributed to the focusing effects of the irregular topography normally accompanying basement rock outcrops. In the frequency band considered, it is concluded that for the purposes of aseismic design of structures no discrimination should be made between the intensity of ground motion expected on basement rock, sedimentary rock, and coarse-grained alluvium typical of Southern California.
The agreement between the recorded strong motion amplitudes and those predicted by a simple two-parameter source model suggests that the model can be used for the assessment of strong ground motion to be used in design procedures. A procedure for estimating design earthquakes using the source model and the amplitude decay expression is presented.https://resolver.caltech.edu/CaltechEERL:1975.SML.1975.001Dynamic centrifuge testing of cantilever retaining walls
https://resolver.caltech.edu/CaltechEERL:1982.SML-82-02
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 gages. Moment, pressure, shear, and displacement distributions (static, dynamic, and residual) were obtained.
From the test data, some empirical curves for relating the upper bound responses of the retaining walls to the strong motion characteristics of the applied earthquakes were obtained.https://resolver.caltech.edu/CaltechEERL:1982.SML-82-02Application of plasticity theory to soil behavior : a new sand model
https://resolver.caltech.edu/CaltechEERL:1983.SML-83-01
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 may be criticized when applied to soil. A recent theory, called "bounding surface plasticity," generalizes the conventional plasticity and describes more accurately the cyclic responses of metals and clays. This new theory is first presented and linked with the conventional plasticity, then applied to a new material, sand. Step by step a new sand model is constructed, mainly from data analysis with an interactive computer code. In its present development, only monotonic loading s are investigated. In order to verify the model ability to describe sand responses, isotropic, drained and undrained tests on the dense Sacramento River sand are simulated numerically and compared with real test results and predictions with another model. Finally the new constitutive equation, which was formulated in the p-q space for axisymmetric loadings, is generalized in the six-dimensional stress state with the assumption of isotropy and a particular Lode's angle contribution. This new model is ready to be used in finite element codes to represent a sand behavior.https://resolver.caltech.edu/CaltechEERL:1983.SML-83-01Experimental studies of dynamic response of foundations
https://resolver.caltech.edu/CaltechEERL:1983.SML-83-02
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 foundations of different shapes, sizes, masses, and moments of inertia were tested. The effect of soil depth, boundary conditions, and depth of foundation embedment were investigated. Mainly rocking and horizontal modes of vibration were studied, The impulse rocking-horizontal excitation of the models was provided by actively perturbing the model structures using explosive energy or by passively exciting them by shaking the whole soil bucket using a hydraulic shaking system. The forced vibration was produced by a miniature air-driven counterrotating eccentric mass shaker mounted on the model structures. During the tests detailed measurements of the static and dynamic contact pressure distributions, displacement components of the model, and acceleration amplitudes at different elevations of the model structure were obtained. The acceleration ratios were used to determine the modes of vibration of the foundation systems. Natural frequencies and damping coefficients of the modes were calculated by f1tting the amplitude-frequency response of a single degree of freedom mass-spring dashpot oscillator to the experimental response curves derived from the test data. Experimental results provided information regarding the influence of different geometrical, inertial, and loading conditions on the vibrational characteristics of the soil-structure system. In particular the effect of foundation embedment was to increase the model resonant frequencies and to cause an appreciable change in contact pressure distribution underneath the footing. However, the resonant frequencies predicted by the lumped parameter analysis for a simple two-degree-of-freedom (rocking and translation) model were about 15 to 55 per cent higher than those measured experimentally. These results were approximately consistent with the comparisons made in similar theoretical and experimental studies such as those performed by Morris in the Cambridge centrifuge and those performed on full-scale footings by Stokoe and Richart. Damping ratios of the rocking-sliding vibration did not change considerably when footing size or depth of embedment changed. The existence of rigid boundaries around the soil mass in the bucket, and an inefficient contact between soil and the foundation side walls and lower surface could account for these observations. Uplift and nonlinear large amplitude vibrations were consistently observed during the steady-state vibration tests. Uplift led to a softer vibrating system which behaved non-linearly. As a result the frequency of vibration decreased with the amount of lift-off. In transient vibration uplift reduced the intensity of higher frequency vibration. Soil around the foundation edge yielded and plastic deformations and subsequent softening of the contact soil increased the material damping while it decreased the resonant frequency of the system. It was concluded that elastic half-space theory does not satisfy the needs for analysis of foundation behavior under high amplitude vibrations and more sophisticated methods of analysis are required.https://resolver.caltech.edu/CaltechEERL:1983.SML-83-02Two-phase soil study: A. Finite strain consolidation, B. Centrifuge scaling considerations
https://resolver.caltech.edu/CaltechEERL:1985.SML-85-01
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 consistent results. For the Eulerian formulation, the material derivative contains a convective term. This convective effect is then analytically studied and found not to be negligible for a final natural strain greater than 10%. A method is then introduced that can account for both the moving boundary and the convective effect. This method is tested in a finite difference scheme and found to give identical results with the Lagrangian finite element scheme for the one-dimensional case. Finally the method is used for the axisymmetric problem of consolidation by vertical drain. The solution to this case suggests that arching and subsequent load redistribution should be considered.
PART B -- Conceptually, when a centrifuge is used to test models, the centrifuge is assumed to produce an equivalent ng gravitational field (as on another planet) and the behavior of the model in the ng field is then assumed to be similar to that of the prototype. For most static problems, the centrifuge does model the prototype well but for some dynamic problems, these assumptions can break down. To investigate this, the similarity requirements are examined for the case of a single particle moving in a fluid. It is found that for the post-liquefaction process and for seepage flow, unless the Reynolds number is much less than one in both model and prototype, the centrifuge is not a good simulation. of the prototype situation. But, perhaps contrary to expectations, the breakdown is due to the fact that the behavior in the ng planet is not similar to the prototype 1g planet, whereas the centrifuge does simulate the ng planet well. Further, it is shown that the concept of "modeling of models" can lead to misleading results. Lastly, for cratering experiments, it is concluded that the centrifuge will only model the crater shape just after an explosion and not the final crater shapehttps://resolver.caltech.edu/CaltechEERL:1985.SML-85-01Failure of slopes
https://resolver.caltech.edu/CaltechEERL:1987.SML-87-01
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 problem under gravity, based on unstable material behavior. Using a Lagrangian differencing scheme in space and explicit integration in time with dynamic relaxation, the numerical method finds the equilibrium state of the slope as the large-time limit of a dynamic problem with artificial parameters. The solution predicts localized shear failure zones which initiate at the slope toe and propagate to the slope crest in the manner and geometry observed in the centrifuge tests. In so doing, the finite difference algorithm also demonstrates an apparent ability to predict shear failure mechanisms in solid continua in general.https://resolver.caltech.edu/CaltechEERL:1987.SML-87-01Numerical simulations of two-dimensional saturated granular media
https://resolver.caltech.edu/CaltechEERL:1989.SML-90-02
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 assemblage of discrete paxticles having the shape of discs.
2. To model and represent the interaction of interstitial pore fluid present with the idealized granular media.
The representation of the solid skeleton is based on Cundall and Strack's distinct element model, in which discrete particles axe modelled as discs in two dimensions, each obeying Newton's laws. Interparticle contacts consisting of springs and frictional element dashpots are included. Assuming a Newtonian incompressible fluid with constant viscosity and density, and quasi-steady flow, the fluid phase is described by Stokes' equations. The solution to Stokes' equations is obtained through the boundary integral element formulation. Several validation test cases axe presented along with four simple shear tests on dry and saturated granular assemblages. For these last four tests, the numerical results indicate that the model is able to represent qualitatively the behavior of real soil, while at the same time clarifying the processes occurring at the microscale that influence soil response.https://resolver.caltech.edu/CaltechEERL:1989.SML-90-02Soil stress field around driven piles
https://resolver.caltech.edu/CaltechEERL:1989.SML-90-01
DOI: 10.7907/GVHQ-5N43
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 field during pile driving. These are necessary for comparison with analytical and theoretical work. The work presented here appears to be the first attempt to obtain dynamic response of the soil during driving. The objective was to obtain a good understanding of the physical phenomena occurring in the soil and pile during driving.
In order to achieve these objectives both dynamic (transient) and static responses of the soil and pile were measured by means of transducers: accelerometers and strain gages for the pile, pressure transducers for the soil. In particular, the relations between static and dynamic data were explored, which resulted in the modelling of the soil-transducer interaction with a non-linear, history- dependent, model.
Results were obtained regarding pile dynamics, soil dynamics, and soil stress field (radial and vertical distribution, stress contours). Both linear and soil-cell model assumptions were used, which enabled a comparison between the two, leading to an estimate that each constitutes a bound of the real stress field, with the linear giving the higher, and the non-linear the lower bound, and the true stress being closer to the lower bound.
The soil response during driving is obtained, filling the gap in the study of the pile-soil system, where only the pile response was known. Recommendations for further work and better experimental procedures are given.https://resolver.caltech.edu/CaltechEERL:1989.SML-90-01Seismic deformation analysis of earth dams : a simplified method
https://resolver.caltech.edu/CaltechEERL:1991.SML-91-01
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 simplified method and study the dynamic response of the rigid block on an inclined plane experimentally, shaking table tests are performed on the model used in the simplified method. Comprehensive numerical simulations are carried out with the computer programs developed, and comparisons with the test results are made.
Finally, applying the developed method to La Villita Dam and El Infiernillo Dam, seismic deformation analyses are carried out. In addition, an attempt to reproduce some of the motions recorded on La Villita Dam during the 1985 earthquake is made in this study.https://resolver.caltech.edu/CaltechEERL:1991.SML-91-01Physical scale modeling of geotechnical structures at one-G
https://resolver.caltech.edu/CaltechEERL:1996.SML-97-01
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 sand placed in a loose and dense state in adjacent halves of a laminar box, and the results of these tests were compared with a similar centrifuge test (Model 3) which was performed as part of the VELACS study. Some of the one-g models were constructed with an alternate model sand and an alternate pore fluid to investigate these modeling variations. One-g models were also constructed with the sand at a uniform density throughout the laminar box.
The research indicates that there is a significant conflict between the time scaling for dynamic processes and dissipation processes in both the centrifuge and one-g techniques, which means that excess pore pressures generated in the model saturated sand by a simulated earthquake will be less than what would occur in the same sand in the real prototype. This effect is generally more severe in the centrifuge. This implies that model tests performed to investigate liquefaction, flow failure problems, and/or deformation problems in saturated sands may significantly underestimate the potential behavior of the prototype. In addition to the above, the research provides insight into the behavior of adjacent loose and dense sands and indicates the potential for high excess pore pressures to develop in the dense sand. Current practice ignores the potential for liquefaction in dense sands or the development of cyclic mobility in the assessment of the seismic performance of geotechnical structures.https://resolver.caltech.edu/CaltechEERL:1996.SML-97-01Centrifuge Studies of Cyclic Lateral Load-Displacement Behavior of Single Piles
https://resolver.caltech.edu/CaltechAUTHORS:20140529-140628605
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 soil more closely resembling the fine-grained MI sand, at higher relative densities than had been achieved in
the earlier tests. It is worth pointing out here that it is not easy to produce a model pile with the correctly scaled EI, since, although the dimensions can be correctly calculated, they are based on an assumed E for the material
which may be slightly different in the metal actually machined, and the strain gauges, leads and moisture-protection coating employed increase the EI in the
final product. A further deficiency of the first test pile was that, although the model pile had been instrumented with 5 strain gauges, they had been installed in locations and at intervals that proved inconvenient in the actual
centrifuge tests. Only three gauges could be positioned below ground surface. On the model pile whose use is described here, 6 strain gauges were bonded,
closer together near the top, at sites such that all six gauges were at or below the soil surface. As will be seen later, this enabled much better curves
of moment in the pile as a function of depth to be plotted.https://resolver.caltech.edu/CaltechAUTHORS:20140529-140628605Centrifuge studies of cyclic lateral load-displacement behavior of single piles
https://resolver.caltech.edu/CaltechAUTHORS:20140529-141936464
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 is
of concern, current interest centers on those in the Arctic.
The particular point of the discussion regarded current field investigations, laboratory test procedures, determination of soil material properties and behavior under cyclic or dynamic loadings, and analysis including soil-structure interactions. It is felt that improvement is needed in all these areas to improve confidence in the
ability of analyses to estimate the performance of offshore structures under design loads. Field data on the performance of full-scale structures under severe loading conditions are urgently required, but are unlikely to be obtained because of the scale of the structures
involved and the low probability of having a particular instrumented structure subjected to design loads. Consequently some form of model study seems inevitable to enable alternative design or analysis methods to be checked.
A program of implementing this possibility was suggested.
It would consist of a program of laboratory tests, and associated analytical efforts, performed at UCLA under the supervision of Professor Lee, to determine the types of test and analysis best suited to the present problem. This program would be addressed by Professor Lee in a complementary proposal.
In order to provide the equivalent of field tests which can be employed to check the results of analysis, it was proposed that centrifugal model tests be performed at Caltech under the supervision of Professor Scott, in close cooperation with Professor Lee. These would consist of cyclic tests of simplified, but realistic model structures
consisting of one-pile or multi-pile arrangements imbedded in saturated soil. The soil would be the same as is to be used at UCLA in the parallel investigation.
The proposal to perform tests on model piles in a centrifuge
at Caltech was accepted by the American Petroleum Institute, and work was initiated. Static and cyclic lateral loading tests on model piles in dry and saturated sands and a saturated sandy silt have been
performed. This report describes the apparatus, tests, results, and analyses involved in the tests.https://resolver.caltech.edu/CaltechAUTHORS:20140529-141936464Analysis of Centrifuge Pile Tests; Simulation of Pile-Driving
https://resolver.caltech.edu/CaltechAUTHORS:20140529-134059571
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 a series of strain gauges attached to the pile. In effect these indicate the bending moment in the pile as a function of length along it. As a consequence, to obtain the pile-soil interaction behavior at various locations along the pile, it
is necessary to integrate the bending moment function twice for each level of applied load to obtain pile displacements (the top displacement is measured and known), and to differentiate it twice, to get the soil interaction
pressure. Then, at a given point on the pile, the pile-soil interaction behavior is given by plotting the pressure versus the displacement at various load levels. A series of such functions at different depths gives the information required for subsequent analyses.
The troubles with this procedure are well-known. Double integration is satisfactory and gives a good indication of pile deflections, since the smoothing process eliminates the effect of random errors in the measurement
of pile strains. However, double differentiation exaggerates the same errors, and the resulting pressure function can be quite erratic. It is necessary to smooth the strain gauge data first before processing it;
various smoothing techniques are available and have been tried. The results of preliminary attempts at obtaining a smoothing function are described in a previous report (3).
In the stage of the work reported here, a revised method of analysis was developed, and applied both to calibration tests of the pile, and to the tests carried out in dry and saturated sand. The results of these applications are described below.https://resolver.caltech.edu/CaltechAUTHORS:20140529-134059571Axially-loaded centrifuge pile tests
https://resolver.caltech.edu/CaltechAUTHORS:20140529-135227305
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.https://resolver.caltech.edu/CaltechAUTHORS:20140529-135227305Cyclic Lateral Loading of Piles; Analysis of Centrifuge Tests
https://resolver.caltech.edu/CaltechAUTHORS:20140529-143954237
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 represented by a smooth and continuous curve. Erratic data due to alternately dense and loose soil layers are avoided. In the second report (7) the fitting of curves to this data was discussed
briefly with reference to the use of a fifth-order spline function. The advantage of the technique is that the curve passes through all the data points in contrast with least squares or linear regression fits. In the
latter, general curves are obtained representative of the pile deflections in some way which pass near but not necessarily through the data points. Errors in the data are inherently accepted in this method.https://resolver.caltech.edu/CaltechAUTHORS:20140529-143954237Applications of Plasticity Theory to Selected Problems in Soil Mechanics
https://resolver.caltech.edu/CaltechAUTHORS:20151130-164806389
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 transforms into that of compression with a rigid
part of clay moving with the wedge. Finite element solutions, for a bilinear material model, were obtained to establish a correspondence between the response of the plane strain wedge and its axi-symmetric
counterpart, the cone. Results of the study afford a better understanding of the process of indentation of soils by penetrometers and piles as well as the mechanism of failure of deep foundations (piles and anchor plates).
The second topic concerns the plane strain steady-state free
rolling of a rigid roller on clays. The problem is solved approximately for small loads by getting the exact solution of two problems that encompass the one of interest; the first is a steady-state with a geometry
that approximates the one of the roller and the second is an instantaneous solution of the rolling process but is not a steady- state. Deformations and rolling resistance are derived. When compared with existing
empirical formulae the latter was found to agree closely.https://resolver.caltech.edu/CaltechAUTHORS:20151130-164806389