A series of triaxial compression tests were carried out on cohesionless soils reinforced with discrete, randomly distributed fibers, both synthetic and natural, to study the influence of fiber characteristics (i.e., weight fraction, aspect ratio, and surface friction) soil characteristics and its density, and confining stress on shear strength of reinforced soils. A regression analysis of test results has been carried out to develop a mathematical model to bring out the effect of these factors on the shear strength of reinforced soil. The model estimates the strength of soils reinforced with any type of fiber and under given stress environment. The model predictions agree reasonably well with the experiment results and the results published in the literature. The test results indicate that the failure envelopes of soil-fiber composites have a curvilinear failure envelope, with a transition occurring at a certain confining stress, termed as “critical confining stress,” below which the fibers tend to slip. The amount of the critical confining stress is affected by the fiber aspect ratio. Fiber inclusion increase significantly the shear strength of soil. The increase in strength is function of fiber weight fraction, aspect ratio and soil grain size.

Even though soil is a highly variable material, the analysis of flow through earth dams typically proceeds deterministically and results can sometimes be quite misleading. In fact it is well known that soil permeability varies randomly from point to point in space and an improved earth dam model should incorporate this variability. In this paper the soil permeability in an earth dam of variable geometry is viewed as a weakly stationary spatially random field following a lognormal distribution with prescribed mean, variance, and spatial correlation structure. The mean and variance of the total flow rate through the dam and free surface drawdown are estimated using Monte Carlo simulations. A simplified empirical approach to the prediction of the mean and variance of the flow rate is presented to allow these quantities to be approximated easily and without resorting to simulation.

The LATWAK test consists of hitting in the horizontal direction the side of a pile on which a horizontal velocity transducer is attached. The blow is delivered with a sledge hammer equipped with a dynamic force transducer. The force time signal from the hammer (input) and the velocity time signal from the pile (output) are recorded during the impact. The experimental mobility curve is obtained as a function of frequency by calculating the modulus of the complex valued ratio of velocity over force using Discrete Fourier Transforms. Theoretically it is assumed that the pile is an elastic member with mass and that the soil can be represented by linear springs and viscous damping. The problem of the steady state forced vibration of the pile in such a soil is solved mathematically. It leads to the theoretical mobility curve for the pile-soil system. The experimental mobility curve obtained in the LATWAK test on the pile is matched with the theoretical mobility curve. A system identification technique is used to match the two curves and to extract the best-fit model parameters, which include the static lateral stiffness K for the pile-soil assembly. To evaluate the usefulness of the method, the lateral stiffness K _p predicted by the LATWAK test on a pile was compared to the lateral stiffness K _m measured in a static lateral load test on the same pile. A total of 20 pile load tests and 20 LATWAK tests were performed and used to compare K _p and K _m . The results are encouraging.

Mine soils developed from mine spoils commonly have a wide range of particle size. The slopes of old spoil piles usually are marked by gullies due to years of uncontrolled erosion. These characteristics raise questions about applicability of available theories and models for estimating runoff and erosion. An investigation was made to determine whether available erosion models can work for mine soils and can account for gully erosion. The investigation at an abandoned surface mine consisted of measurement of soil and sediment properties, measurement of runoff and erosion, observations of armor by rock fragments on gully floor, and calculations with available theories of sediment transport and slope stability. The results at this site suggest that (1) predictions with the ANSWERS model have about the same accuracy as those made for agricultural lands; (2) armor provided by rock fragments are temporary as they are periodically removed by debris flows; (3) detachment by rainfall impact is the primary cause of erosion on short steep slopes; and (4) a simplified method can be used for estimating erosion on such slopes.

Ground disturbance due to waves generated by a machine foundation can be detrimental to adjacent structures or sensitive equipment operating nearby. Most of the vibratory energy that affects structures nearby is carried by surface (Rayleigh) waves that propagate in a zone close to the ground surface. Therefore, for machine foundations vibrating from moderate to high frequencies, the amplitude of ground motion can be reduced significantly by installing a wave barrier around the source. A three-dimensional boundary element algorithm incorporating quadratic elements has been used to perform an extensive parametric study on the effectiveness of open trenches as wave barriers. The key geometrical and material parameters that govern the performance of an open trench wave barrier have been identified, and a design formula in the form of an algebraic expression has been developed for estimating the vibration screening effectiveness of such barriers. Furthermore, through comparisons with published field test data and rigorous boundary element solutions, the validity of the design formula has been established.

Experimental results are presented that characterize the behavior of a loose, fine-grained, water-saturated sand tested under globally undrained conditions is a plane strain apparatus. Together with local measurements of boundary forces and deformations, stereophotogrammetry is used to track the progressive localization of strain. The constitutive behaviors in the tests prior to localization can be characterized as either undrained local softening or undrained load softening and subsequent rehardening. In both cases, a consistent pattern of onset of the formation of the persistent shear band, mobilization of the maximum effective friction, and the complete formation of the band was observed. Conditions approximating steady state only were observed in the shear bands. The effect of strain localization on the conventionally derived steady state line was found to be minimal when undrained load softening behavior was observed, but significantly different steady-state lines were found from results of plane strain and axisymmetric tests. The differences between tests conducted under these two stress conditions assessed to evaluate the practical implications of the observed differences.

This paper presents results of a series of numerical experiments, using nonlinear finite-element analyses, which investigate the effects of wall embedment depth, support conditions, and stress history profile on the undrained deformations around a braced diaphragm wall in a deep clay deposit. The analyses use a comprehensive effective stress soil model (MIT-E3) to describe important aspects of clay behavior, including small-strain nonlinearity and anisotropic stress-strain-strength, and focus on soil profiles with constant overconsolidation ratio, where the shear strength and stiffness are proportional to the depth. The results are combined in prototype “design” charts for estimating ground movements as functions of the excavation depth and support conditions, and incorporate the effects of wall length on base stability. Similar techniques are applied for a typical soil profile in Boston where a stiff overconsolidated crust overlies much softer clay. The results show the importance of the underlying clay on predicted wall deflections and ground movements.

This paper examines the eigenvalues and eigenvectors of a massive rigid square block bonded to an elastic medium. Uncoupled vertical and coupled sliding-rocking modes of vibration are considered. The supporting medium is modeled as an elastic homogeneous or layered, inertial or massless half-space. For a geometrically damped system, the eigenvalues are complex-valued, while they are purely imaginary in an undamped system. Numerical results are presented to illustrate the effects of inertial interaction. The data is computed by a procedure that takes into account the mixed boundary conditions at the surface of the half-space.

Pile driving formulas are commonly used to estimate the load capacity of driven piles. The formulas assume that there is a correlation between the pile set and the ultimate load capacity of the pile. The important factors influencing the load capacity include the hammer characteristics, the properties of the pile and soil, and the pile set. The present technical note investigates the feasibility of using neural networks to predict the load capacity of driven piles. Neural networks attempt to simulate the process by which the human brain learns to discern patterns in arrays of data. The data used in this study were derived from actual pile driving records. First, the neural network concepts are reviewed, then the neural network model for predicting the pile capacity is presented. The neural network predictions were found to be more consistent and reliable than other, more conventional pile driving formulas.

The characteristic load method (CLM) for analysis at laterally loaded piles and drilled shafts can be used to accurately estimate ground-line deflections and maximum bending moments for both free-head and fixed-head piles in both clay and sand. This technical note provides equations for the nonlinear relationships used in the CLM for analysis of laterally loaded piles and drilled shafts. These equations can be used in spreadsheets or computer code to automate and simplify the analyses. The steps required for spreadsheet analysis of loading conditions involving both load and moment are described.