Showing papers in "Journal of the Soil Mechanics and Foundations Division in 1971"

Simplified procedure for evaluating soil liquefaction potential

Abstract: Significant factors affecting the liquefaction (or cyclic mobility) potential of sands during earthquakes are identified, and a simplified procedure for evaluating liquefaction potential which will take these factors into account is presented Available field data concerning the liquefaction or nonliquefaction behavior of sands during earthquakes is assembled and compared with evaluations of performance using the simplified procedure It is suggested that even the limited available field data can provide a useful guide to the probable performance of other sand deposits, that the proposed method of presenting the data provides a useful framework for evaluating past experiences of sand liquefaction during earthquakes and that the simplified evaluation procedure provides a reasonably good means for extending previous field observations to new situations When greater accuracy is justified, the simplified liquefaction evaluation procedure can readily be supplemented by test data on particular soils or by ground response analyses to provide more definitive evaluations

Finite Element Analyses of Retaining Wall Behavior

Abstract: A means is developed for simulation of realistic behavior of the interface between a backfill soil and a retaining wall in finite element analyses. The interface behavior is shown from a series of laboratory tests to be dependent upon normal and shear stresses on the interface. An analytical formulation is derived to fit the observed relationships and utilized to govern the behavior of a one-dimensional element which serves as the interface between two dimensional soil and retaining wall elements in finite element analyses. Analyses are presented of a typical retaining wall-backfill system with varying modes of wall behavior and degrees of wall roughness. Earth presure distributions before the ultimate conditions are reached are shown to be nonlinear. Ultimate conditions and general behavior of the system are shown to be in agreement with classical theory and previously observed behavior. An additional analysis is presented in which the exact construction sequence of a retaining-wall backfill system is simulated.

Lateral and rocking vibration of footings

Abstract: Numerical data are presented for the steady-state response of a rigid circular disk, or footing, supported at the surface of an elastic halfspace and excited by a harmonically varying horizontal force and a harmonically varying overturning moment. The disk is considered to be massless. The response quantities evaluated include the displacements of the disk in the directions of the exciting forces, the rotation due to the horizontal force, and the distributions of the contact stresses beneath the disk. Data are also presented for the stiffness and damping coefficients in an equivalent spring-dashpot representation of the disk-foundation system. The major displacement components are finally compared with those determined from two previously reported approximate solutions, including one based on an assumed distribution of the contact pressure.

Behavior of Laterally Loaded Piles: I-Single Piles

Abstract: An analysis is presented for the horizontal displacement and rotation of a vertical pile subjected to lateral loading and moment, and situated in an ideal elastic mass. Influence factors are presented for a wide range of pile flexibilities and length-to-diameter ratios, for both free-head and fixed-head piles. Comparisons between the elastic solutions and the corresponding solutions obtained from the subgrade reaction theory show that the latter considerably overestimates the displacement and rotation of the pile, but gives a reasonable estimate of the moments in the pile. The elastic analysis is extended to include the effect of local yield between the soil and the pile; the load-displacement relationship for relatively flexible piles is found to be markedly influenced by local yield. The characteristics of behavior indicated by the theoretical solutions agree reasonably well with those reported from measurements on full-scale piles.

Closure on static cone to compute static settlement over sand

Abstract: USE OF A FLAT-ENDED PENETROMETER, AS SUGGESTED BY RANANATHAN, RUNS INTO PRACTICAL DIFFICULTIES. WITHOUT THE POSITIVE GUIDE OF THE CONE POINT, THE TIP MAY DRIFT UNPREDICTABLY, A SERIOUS PROBLEM AT SOUNDINGS IN EXCESS OF ABOUT 50 FEET. FURTHERMORE, THE FLAT TIP, INSTEAD OF SHEDDING SOIL DURING ITS ADVANCE, AS DOES THE CONE TIP, TENDS TO TRAP AND CARRY DOWN ITS OWN SOIL PLUG. THE RESEARCH OF GIELLY, LAREAL, AND SANGLERAT INTO PREDICTING THE COMPRESSIBILITY OF COHESIVE SOILS USING STATIC CONE PENTROMETER DATA SUGGESTS THAT THE DRAINED COMPRESSIBILITY OF COHESIVE SOILS MAY RELATE TO THE UNDRAINED STRENGTH CHARACTERISTICS OF SUCH SOILS. THE ENERGY EXPENDED TO ADVANCE THE CONE PENETROMETER, RESULTING IN RADIAL EXPANSION OF A CYLINDER EQUAL TO THE DIAMETER OF THE PENETROMETER TIP, MAY HAVE A FUNDAMENTAL RELATIONSHIP TO THE DISRUPTION AND COMPRESSIBILITY OF THE STRUCTURE OF ANY SOIL. THE CASE STUDIES PRESENTED BY WEBB AND MELVILL ARE A VALUABLE CONTRIBUTION. A MODEL STUDY MADE IN 1968 BY ANNE TOPSHOJ AND SUPERVISED BY THE AUTHOR INVESTIGATED THE RATIO OF EDGE/CENTER SETTLEMENT FOR A FLEXIBLE, UNIFORMLY LOADED, CIRCULAR AREA OF 4.1 INCHES DIAMETER PLACED ON THE SURFACE OF A DRY, UNIFORM, MEDIUM QUARTZ SAND AT A RELATIVE DENSITY OF ABOUT 25%. SHE ALSO TESTED A RIGID PLATE OF THE SAME DIAMETER PLACED ON A LATEX SHEET ON THE SURFACE OF THE SAME SAND IN THE SAME CONDITION AND LOADED TO THE SAME TOTAL LOAD. THE BEARING OF THIS WORK ON THE RESEARCH OF WEBB AND MELVILL IS ILLUSTRATED AND DISCUSSED.

Volume changes in sands during cyclic loading

Abstract: Measurements of the volume change behavior of sands under cyclic loading simple shear conditions suggest that the vertical strain due to compaction depends only on the shear strain amplitude induced in the sample at strains exceeding 0.05%. This indicates that cyclic shear strain, which deforms the sample allowing particles to move into denser packing, may well be a fundamental parameter in determining the volume change behavior of cohesionless soils under dynamic loading conditions. Quantitative data also showed that there was significantly more volume change for sand at relative densities below 60%. In addition, the importance of the first few strain cycles in determining the total vertical strain in the sample was indicated by the fact that for the range of test parameters studied, as much vertical settlement due to compaction occurs in the first 10 cycles as occurs in the next 40 cycles. The test data may be used to evaluate the possible magnitude of ground surface settlements due to ground shaking caused by earthquakes or other types of ground vibrations.

Test Procedures for Measuring Soil Liquefaction Characteristics

Abstract: The merits and limitations of laboratory simple shear and triaxial compression tests, conducted under cyclic loading conditions, are analyzed. In addition the theoretical relationships between the stress conditions causing liquefaction in simple shear and triaxial compression tests, based on several different failure criteria, are investigated. Finally data are presented for 35 sites where liquefaction is known to have occurred or not occurred during earthquakes, providing a means for evaluating the stress conditions causing liquefaction of sands in the field. It is shown that both analytical and experimental evidence, as well as field data, suggest that most laboratory triaxial compression test data, expressed in terms of σ dc /(2σ a ) should be reduced by a factor of 0.55 to 0.7, depending on the density of the soil and the duration of the earthquake, in order to determine values of τ Dhv /σ' o causing liquefaction during earthquakes under field conditions. Considerable judgment is involved in evaluating such relationships, and data from field studies may provide the basis for evaluating the liquefaction characteristics of sands.

Sand Liquefaction in Triaxial and Simple Shear Tests

Abstract: Data from cyclic loading simple shear and triaxial tests indicate that the important variable controlling the incidence of liquefaction in a given number of cycles in a saturated sand at a particular void ratio is the initial effective stress ratio; the ratio of the peak alternating shear stress to the initial effective mean normal stress. Contrary to previously published results, equal resistances to liquefaction are obtained in both kinds of tests. This agreement is considered to be due to three things: (1) Representation of the confining pressure in the simple shear test by the mean normal stress in the plane of deformation; (2) the improved model of the simple shear apparatus used; and (3) the use of experimental techniques which insures the development of uniform strains in the simple shear test. The experimental techniques used evolved from a fundamental study of the deformation of samples in the simple shear apparatus.

Behavior of Laterally Loaded Piles: II-Pile Groups

Abstract: An elastic analysis is presented for the horizontal displacement and rotation of a laterally loaded pile group and the distribution of horizontal forces within the group. The interaction between two identical equally loaded piles is analyzed first, and the increases in displacement and rotation of the piles, in relation to the single pile values, are expressed in terms of interaction factors. Using these interaction factors, a method for calculating the displacement and rotation of a general pile group, based on the principle of superposition, is described. An examination of the behavior of square groups of piles reveals that the displacement, rotation, and load distribution in the group is largely influenced by the length-to-diameter ratio of the piles and the relative pile flexibility. It is also found that the displacement depends on the breadth of the group rather than the number of piles in the group. A reasonable measure of agreement is found between a limited number of reported measurements and theoretical predictions of group displacements.

Consolidation at Constant Rate of Strain

Abstract: A new general purpose consolidometer for studying the one-dimensional consolidation behavior of soils is described. The test specimen can be loaded incrementally, as in the conventional test, at a constant rate of stress, or at a constant rate of strain. The apparatus can also be used to measure residual pore pressures and swell pressures during back pressure saturation at constant volume. Pore pressures are measured at the impervious base, and free drainage occurs from the top surface. A general solution to the consolidation equation is derived for conditions of constant rate of strain assuming constant \Ic\dv\N. While particular solutions are given for both a linear soil having constant \Im\dv\N and a nonlinear soil with constant \IC\dc\N, it is shown that for most purposes the linear solution is sufficiently accurate for interpreting constant rate of strain (CRSC) test results. The CRSC test is shown to be a simpler and much faster method for measuring the consolidation characteristics of soils than is the conventional test.

Deformation characteristics of sands under cyclic loading

Abstract: A knowledge of the dynamic stress-strain characteristics of sand subjected to controlled values of shear strain commonly encountered in the field during strong ground shaking is often desirable. Cyclic load simple shear tests have been used to investigate soil performance at shear strain amplitudes greater than those possible from many other types of dynamic laboratory testing equipment. It was found that dynamic modulus values determined near the upper limit of shear strain amplitude that might be expected to be induced by seismic shaking (0.1%) were as much as 40% lower than modulus values obtained at the lowest values of shear strain that were investigated (0.01%). Modulus values were also found to increase slightly with increasing numbers of cycles and with increasing relative density. Values of hysteretic damping, determined from hysteresis loops, showed damping to increase with increasing shear strain amplitude and to decrease slightly with increasing numbers of cycles and increasing values of vertical stress. Curves summarizing the effects of the several parameters on dynamic soil properties have been presented.

Pore Size Distribution Studies

Abstract: Pore-size distribution data for pores of diameters down to 0.016 μm were obtained by mercury porosimetry for a number of laboratory-prepared specimens. Statically-compacted specimens of a kaolinite, an illite, and Boston Blue Clay were evaluated, and changes in the pore-size distribution of the kaolinite were followed as a function of increasing amount of static compaction. In this clay several distinct classes of pore sizes were recognized. Initial compaction reduced the gross pore sizes without influencing the finer classes. After the elimination of the gross pores, further compaction was at the expense of an intermediate class of pores above about 0.14 μm in diameter, pores finer than this being unaffected. Specimens of the kaolinite prepared from a slurry or by sedimentation showed substantially different pore-size distributions from the compacted clay. Drying shrinkage tended to eliminate the larger pores while leaving the smaller ones unaffected. Pore-size distribution appears to be a sensitive parameter with which to follow the effects of microstructural changes which may influence the engineering behavior of the material.

Bearing capacity of anisotropic cohesive soil

Abstract: A new description of anisotropic cohesive strength provides a simple solution for the bearing capacity of a strip load, based on previous work by Hill This solution and a survey of published data on anisotropic shear strength indicate that the bearing capacity at worst is 85% of what would be predicted using conventional shear strength data for vertical compression and bearing capacity theory The bearing capacity is 90% of that predicted by conventional theory and the average of strength from vertical and horizontal compression When compressive strength is available for three orientations of loading, the shear strength can be represented as an ellipse, and the bearing capacity depends on the shape of the ellipse and on the average of vertical and horizontal compressive strengths

Shear strength of sand at extremely low pressures

Abstract: Data contributing to the understanding of the nature of shear strength at extremely low pressures are presented. The expanding use of models for solving soil stability problems has aroused considerable interest in the behavior of sand at confining pressures below 5 psi. Triaxial compression tests were carried out varying the cell pressure between 0.20 psi and 35 psi. Experimental evidence shows that the increased dilatancy of sands sheared at extremely low pressures produces an increase in the principal stress ratio at failure. The overall increase in strength is mostly represented by the introduction of an apparent cohesion intercept. Values of this intercept for the quartz sand tested range from 0.14 psi at loose states to 0.22 psi at dense states. Values of the angle of shearing resistance at extremely low pressures are smaller than those obtained at moderate pressures by less than 0.5°. For loose states, shear can be associated with expansive volume change if the normal pressures are low enough. The shearing behavior of loose sands at very low pressure is quite similar to that of dense sands at moderate pressure.

Bearing Capacity of Eccentrically Loaded Footings

Abstract: The bearing capacity of an eccentrically loaded footing is determined by analytical formulation. In this analysis, the footing has been considered rigid with a rough base. It has been assumed that the rupture surface is a log spiral, and failure occurs on the same side as the eccentricity with respect to the center of the footing. The resistance mobilized on this side is fully passive and partial on the other. The footing has been assumed to lose contact with increase in eccentricity and the results are given in the form of bearing capacity factors N γ , N q , and N c . For the verification of analytical solutions, model tests were conducted on sand both in dense as well as loose states. Footings were tested both at surface and at a depth such that D f / B = 1 and eccentricity of load ranged from 0.1 B and 0.4 B , in which D f and B are, respectively, depth and width of footing. Test data of the previous investigators are also analyzed and compared with the proposed theory. A reasonable agreement was found between the theory and the test data.

Initial Settlement of Structures on Clay

Abstract: A METHOD FOR HAND CALCULATION FOR PREDICITNG THE SETTLEMENT (DUE TO UNDRAINED SHEAR) OF STRUCTURES ON STRUCTURES ON SATURATED CLAY WHEN LOCAL YIELDING OCCURS IN THE FOUNDATION SOIL IS PROPOSED. THE METHOD EMPLOYS A CORRECTION TO THE SETTLEMENT COMPUTED FROM ELASTIC THEORY I. E., WITHOUT ANY YIELDING USING DIMENSIONLESS PLOTS DEVELOPED FROM FINITE ELEMENT ANALYSES FOR THE LOADING OF A HOMOGENOUS, ELASTO- PLASTIC SOIL. THE METHOD REQUIRES A KNOWLEDGE OF THREE PARAMETERS: THE ELASTIC VALUE OF YOUNG'S MODULUS IN UNDRAINED SHEAR; THE ULTIMATE BEARING CAPACITY; AND THE INITIAL SHEAR STRESS RATIO. YIELDING WILL NOT SIGNIFICANTLY INCREASE THE INITIAL SETTLEMENT UNLESS THE INITIAL SHEAR STRESS RATIO IS GREATER THAN 0.4, WHICH CORRESPONDS TO A FOUNDATIONS SOIL WITH AN OVERCONSOLIDATION RATIO OF 1.5 OR LESS. THE PROPOSED METHOD FOR COMPUTING INITIAL SETTLEMENT WOULD APPLY MODULUS IN UNDRAINED SHEAR AND INITIAL SHEAR STRESS RATIO RARELY USED. SINCE EVALUATION OF YOUNG'S MODULUS IN UNDRAINED SHEAR AND INITIAL SHEAR STRESS SRATIO CAN BE EXPENSIVE AND TIME-CONSUMING, TYPICAL VALUES ARE PRESENTED WHICH COULD BE SELECTED ONCE THE PLASTICITY CHARACTERISTICS, UNDRAINED SHEAR STRENGTH AND STRESS HISTORY OF THE FOUNDATION CLAY WERE ESTABLISHED. AN ALTERNATE METHOD FOR DETERMINING INITIAL SETTLEMENT WHICH UTILIZES SOIL PROPERTIES DETERMINED FROM IN-SITU PRESSURE-METER TESTS, IS COMMENTED ON.

Long-Term Pressure Effects on Shear Modulus of Soils

Abstract: Long-term resonant-column tests were performed on seven air-dry soils to determine their small-strain dynamic behavior under confining pressures maintained for durations up to 803 days. Test results indicate that: (1) The shear modulus of air-dry soils at constant confining pressure increases with time; (2) the shear modulus after 2 years can be predicted within 15% from 2-day tests; (3) the time-dependent increase in modulus increases with decreasing particle size; (4) the time-dependent increase in density under a constant pressure accounts for only 0-15% of the total time-dependent modulus increase; (5) continuous low amplitude vibration (shearing strain less than 0.00001) has no measurable effect on the soils tested over and above the time-dependent modulus increase; and (6) a 10-psi step increase in pressure may destroy up to 15% of the time-dependent modulus accumulated with time in clay, but does not influence sand or silt.

Relative Density and Relative Compaction

Abstract: Since the pioneering work of R. R. Proctor some 40 years ago, soil mechanics engineers and contractors have been accustomed to evaluating a compacted fill in terms of relative compaction. Because of the many similarities, the terms relative compaction and relative density can be confused. The study presented herein was made to show the distinction between terms and to illustrate a simple and practical correlation between them.

Electric Penetrometer for Site Investigations

Abstract: Several types of penetrometers are being used for the static penetration test which have generally the same basic dimensions but differ greatly in shape and method of operation. A review is presented of the most common mechanical penetrometers, including the Begemann friction cone penetrometer, with their advantages and disadvantages. Subsequently, an electric penetrometer is fully described which contains a strain gage load cell and which permits also the measurement of side friction on a separate sleeve. The resistances are recorded directly and continuously as graphs. The penetrometer has a built-in inclinometer to check the verticality of the sounding. The method provides greater reliability of the measurements than the traditional mechanical cones as various potential sources of error have been eliminated. It allows a great degree of automation and has increased the range of applicability of the penetrometer test.

Heave and lateral movements due to pile driving

Abstract: Vertical and lateral displacements of soil and driven piles occur during pile driving in certain types of soils. The occurrence of vertical heave often significantly adds to the cost of a pile foundation. The undetected occurrence of heave of piles and foundation soils can lead to ultimate failure of a pile foundation. A case history study of 13 pile foundations was undertaken. Mechanisms of soil and pile displacements are proposed and the effects of various factors on the displacement phenomena are analyzed. The principal factors which affect the mode and magnitude of soil and pile displacement are: (1) The characteristics of the soil into which the piles are driven; (2) the characteristics of the piles themselves; (3) the sequence of pile driving; and (4) the overall geometry of the pile foundation. An approximate method of prediction of the magnitude of soil and pile heave is presented.

Engineering Properties of Mine Tailings

Abstract: The engineering properties of tailings from nine mines are summarized to demonstrate that these are good engineering materials. Such properties as gradation, specific gravity, mineral content, laboratory maximum and minimum density, in-place density and moisture, permeability, triaxial shear data, and one-dimensional compression data are presented in graphical and tabular form. Presented is an example of tailings usage in constructing a 4-mile section of Interstate 90 near Kellogg, Idaho, proving that tailings can be used to construct a modern high-capacity freeway. The theoretical design of a small earth dam is also given as an example that tailings could be used to build a dam with adequate factors of safety. It is strongly felt that the material properties presented will promote interest in the employment of mill tailings in future construction projects for both structural and environmental reasons.

Limit analysis of stability of slopes

Abstract: THE UPPER BOUND THEOREM OF LIMIT ANALYSIS IS APPLIED TO OBTAIN COMPLETE NUMERICAL SOLUTIONS FOR THE CRITICAL HEIGHT OF SLOPES. A LOGARITHMIC SPIRAL MECHANISM WHERE THE FAILURE SURFACE MAY PASS BELOW THE TOE IS ASSUMED IN THE ANALYSIS. THE ANALYSIS INCLUDES THE EXISTING LIMIT EQUILIBRIUM SOLUTIONS AS WELL AS THE PREVIOUSLY OBTAINED LIMIT ANALYSIS SOLUTIONS AS A SPECIAL CASE, SO THAT IT MAY BE CONSIDERED A GENERALIZATION OF ALL THESE PREVIOUS SOLUTIONS. THE RESULTS FOUND ARE PRACTICALLY IDENTICAL TO THOSE OBTAINED BY THE EXISTING LIMIT EQUILIBRIUM PROCEDURES. /AUTHOR/

Inflection Point Method for Computing C v

Abstract: Presented herein is a new method for determining coefficient of consolidation C v from an oedometer test which is based on the discovery that time factor T corresponding to the inflection point of a semilogarithmic plot of a time curve is fixed and equal to T = 0.405.

Unconfined Transient Seepage in Sloping Banks

Abstract: A finite difference scheme is used for the problem of unsteady flow with arbitrary variations in water levels in nonhomogeneous and anisotropic porous soils. The solutions are obtained by using the finite difference scheme for an approximate nonlinear and the linearized version of the free surface equation of flow. The phreatic surface at any time level is located by satisfying the special boundary condition at that surface. A special iterative scheme is employed to locate the point of exit of the phreatic surface at the entrance face. Numerical solutions are compared with experimental results with a large parallel-plate viscous flow model. Good agreement is obtained between the two results. A flow net is constructed for typical numerical results to indicate their application for field problems. On the basis of good comparisons, it is concluded that the proposed numerical method can be employed for the location of the free surface in riverbanks and embankments subjected to transient flow conditions.

Yield and Failure of a Clay under Triaxial Stresses

Abstract: A study is made of the three-dimensional stress-deformation behavior of a normally consolidated saturated remolded clay. It is demonstrated that unless certain requirements of analytical models (e.g., isotropy and volume change) are reconciled with the observed physical performance of the clay in yield, serious errors and misinterpretations would arise in the use of classical plasticity techniques for analysis. The true triaxial test results permit the measurement of associated deformations, and allow for the development of modifications to the classical theory. The adaptation of plasticity theory proposed in this study affords a suitable analytical model for the description of response behavior of the clay over a considerable range of applied stress levels. Beyond this range the changes in material properties accompanying shear deformation can no longer be compatible with the requirements of isotropic plasticity theory. In the ultimate stage of yielding, the clay performance tended to that of an internally frictional material.

Evaluation of pore pressures beneath an embankment

Abstract: Excess pore pressures measured during construction of a highway embankment on a deep deposit of soft to medium clay are evaluated. Several methods for predicting initial excess pore pressures are examined, including a recently developed method that considers the effects of local yield within the foundation soil. Undrained shear strengths backfigured from the field pore pressure data are compared to strengths measured in laboratory shear tests and field vane tests.

Load-Deformation Mechanism for Bored Piles

Abstract: An elasticity model based on the finite element method is developed for analyzing the mechanisms which govern the behavior of bored piles in stiff clay. The method can be used to predict accurately the load capacity and load-deformation behavior of a single pile. A trilinear approximation of the stress-strain curve obtained from undrained triaxial tests is used. The formation of a tension crack which develops at the tip of the pile is shown, invalidating the classical plasticity solutions for tip capacity. The usual assumption of adhesion failure occurring at the pile-soil interface is supported. Comparison of the theoretical results with field measurements on five large-diameter test piles shows the accuracy of the method.

Scale and Boundary Effects in Foundation Analysis

Abstract: The bearing capacity of rough strip footings on sand is analyzed using numerical integration of the plasticity equations. The influence of different boundary conditions below the footing is studied for the zero surcharge case, and bearing capacity coefficients are calculated for various assumed settlements at failure. A pressure dependent solution is described which permits calculation of the variation of Φ with stress level in the failure zone. The results are compared with existing trial failure surface solutions and with experimental values. It is concluded that good agreement can be obtained between theoretical results which assume a trapped elastic wedge beneath the footing, and model results related to average Φ-values from triaxial tests in the normal range of cell pressures. The lack of agreement with field results and the computed variation of Φ in the failure zone imply that this relationship is empirical. A procedure is outlined for relating bearing capacity of a given-sized footing to the initial density of a sand using Φ versus pressure results from plane strain shear tests on sand at the same density.

Flow of air through soils

Abstract: A PROPOSED METHOD FOR SOLUTION MINING OF LOW GRADE ORE WILL INVOLVE THE IN SITU AERATION OF LARGE VOLUMES OF HYDRAULICALLY DEPOSITED SILTY MATERIAL. A LABORATORY INVESTIGATION OF THE SETADY AND UNSTEADY FLOW OF AIR THROUGH SOIL SHOWED THAT FICK'S LAW GIVES AN ADEQUATE DESCRIPTION OF THE FLOW PROCESS AND, MOREOVER, HAS MATHEMATICAL ADVANTAGES OVER THE MORE COMMON D'ARCY'S LAW. THE PROCESS OF IN SITU AIR INJECTION WAS EXAMINED THEORETICALLY ON THE BASIS OF FICK'S LAW. EXPERIMENTAL DATA FROM FIELD TESTS WERE FOUND TO BE IN GOOD QUALITATIVE AGREEMENT WITH THE PREDICTIONS OF THE THEORY. /AUTHOR/

Recoverable Deformation of Cohesionless Soils

Abstract: Herein is shown that available experimental data on the recoverable behavior of cohesionless soils may be fitted closely using constitutive relations corresponding to a special case of the first order theory of hypoelasticity. Four forms of first order isotropic constitutive law are first presented and conditions are determined under which each law is integrable to an elastic law. Constants for the isotropic hypoelastic law are then determined which fit available data for triaxial states of stress and it is shown that the resulting law is inelastic. Consideration is then given to fitting the data by means of an anisotropic first order incremental law. Integrability conditions for triaxial loading states are obtained and are shown to be satisfied by both isotropic and anisotropic laws. The integrated law for triaxial loading for the isotropic case is obtained and demonstrated by application to the anisotropic consolidation test. Tests are described to investigate the elastic character of the recoverable behavior.