This paper presents a one-dimensional (1D) finite-element model for the estimation of ground-water flow through a valley fill. The model determines the piezometric head profile as well as velocities through a waste rock impound. There are serious environmental concerns for a receiving water course due to the effects from acid and sediment generation by these facilities. Understanding ground-water characteristics as it flows through these facilities is the first step in designing safe tailings impound facilities. Flow through a valley fill is nonDarcian due to the large grain sizes and high velocities and requires an alternate energy-loss equation. The Forchheimer equation was used as the basis of the finite-element model. The finite-element model used 1D linear bar elements and required an interative solution due to the nonlinear nature of the problem. Accuracy of the model has been verified by an analytical solution to a more specific problem. A sensitivity analysis showed that the results were most sensitive to the porosity and d₁₀ media characteristic.

Approximate solutions are developed for filtration and subsequent consolidation of compactible cakes on a cylindrical filter element. Darcy's flow equation is coupled with equations for equilibrium stress under the conditions of plane strain and axial symmetry for radial flow inwards. The solutions are based on power function forms involving the relationships of the solidosity ε_s (volume fraction of solids) and the permeability K to the solids effective stress p _s . The solutions allow determination of the various parameters in the power functions and the ratio k₀ of the lateral to radial effective stress (earth stress ratio). Measurements were made of liquid and effective pressures, flow rates, and cake thickness versus time. Experimental data are presented for a series of tests in a radial filtration cell with a central filter element. Slurries prepared from two materials (Microwate, which is mainly SrSO ₄ , and kaolin) were used in the experiments. Transient deposition of filter cakes was followed by static (i.e., no flow) conditions in the cake. The no-flow condition was accomplished by introducing bentonite which produced a nearly impermeable layer with negligible flow. Measurement of the pressure at the cake surface and the transmitted pressure on the central element permitted calculation of k₀ .

Experimental studies of soil penetration by low-velocity projectiles stimulated the development of theoretical modeling of the phenomena. We developed a model of vertical penetration of granular soils verified by known experiments and dimensional analysis. The experimental results showed nonmonotonic dependence between projectile deceleration and depth of penetration. Net resistant force was found to be a complicated function of variable deceleration and depth. This force was defined not only with pure dynamic and static components, but also with a mixed component important for interpretation of experimental results. Theoretical analysis of nonmonotonic variation of resistance with depth permits evaluation of static properties of noncohesive material using dynamic characteristics of projectile penetration. An understanding of physical processes governing projectile's deceleration was acquired. Velocity and acceleration are obtained as functions of initial velocity, depth of penetration, and media properties. We show two conditions when peaks of acceleration are observed. The initial peak is due to dynamic characteristics, and the second peak is due to static characteristics of penetration.

Piedmont residual soils were formed by in-situ weathering of igneous and metamorphic rocks. In this research project, their dynamic properties (shear modulus and damping) were investigated by performing a combination of resonant column and torsional shear tests. These properties were evaluated with respect to confining pressure, shear strain amplitude, particle size distribution, cyclic frequency, and number of cycles and compared to results obtained from other studies reported in the literature. Totally 32 specimens of residual soils were tested. These residual soils were classified as MH, ML, SM-ML, and SM, according to the Unified Soil Classification System. The normalized shear modulus and damping values were found to be in the same range as reported by other authors for transported sands, silts, and clays. With increase in the shear strain amplitude, the normalized shear modulus decreased and damping increased at a rate faster than that for clays but slower than that exhibited by sands. An analytical model was established to predict the shear modulus and the damping ratio as a function of confining pressure and shear strain amplitude for four types of Piedmont residual soils.

Site investigations conducted at the North Carolina State University Research Farm and adjacent construction sites provided the database to study the soil profile and deformation characteristics of Piedmont residual soil. The database includes both laboratory and in-situ test results. The laboratory testing program was composed of oedometer, stress path, triaxial multistage compression, resonant column, and torsional shear tests. In-situ testing included standard penetration tests, dilatometer tests, and pressuremeter tests with Menard and push-in types. A typical soil profile is defined based on Martin's classification system. Test results from triaxial multi-stage compression, resonant column and torsional shear tests show that residual soil's decay pattern of normalized shear modulus with shear strain is similar to and lies between those of sands and San Francisco Bay Mud. The study of soil's compressive stiffness shows that pressuremeter modulus, E _pm , and dilatometer modulus, E _D , are generally consistent while E _N as correlated from a relationship suggested by Martin between E _pm and standard penetration test N -value usually lie on the lower bound. Values of reference deformation modulus, E₁ , as derived from oedometer tests appeared to be a function of the person who conducted the tests. One tester's results are in good agreement with E _pm and E _D , while the others are generally much smaller. Due to the difficulty of trimming Piedmont residual soil specimens, one might suggest that the differences in test results are related to sample disturbance on small specimens such as those used in standard oedometer tests.

The low-strain stiffness and energy dissipation in particulate materials is strongly determined by the behavior of contacts. This paper presents results of a test program designed to study the effect of contact response on the propagation of waves. Wave velocity and attenuation were measured during isotropic loading using a resonant column device at shear strains varying from γ= 10 ⁻⁵ to γ= 10 ⁻⁶ . Elastic, viscoplastic and brittle contact behaviors were studied with steel spheres, lead shot, and silica-kaolinite pellets. All measured velocity-stress exponents were b /2 >≈ 1/6, which is the theoretical value for spherical contacts. High-tolerance steel spheres approximated this value. Contact crushing showed the highest exponent. Theoretical analyses confirmed that several phenomena conduce to a velocity-stress exponent b /2 = 0.25: buckling of particle chains and increase in coordination number, elastoplastic behavior, and cone-plane contacts. Load and unload data for viscoplastic lead shot showed that contact deformation is the governing parameter for low-strain stiffness, regardless whether the causing mechanism was elastic deformation, creep, or yield. All measured damping-stress exponents were between κ=−0.45 for steel and κ=−0.11 for the brittle pellets, while the theoretical value for frictional Mindlin contacts is κ=−2/3. Damping showed higher sensitivity than velocity to stress and time.

Twenty-four reduced scale models of vertical and steeply sloping (1 H :6 V ) reinforced soil walls were built using kaolin as the backfill, reinforced with a nonwoven geotextile simulant, and loaded to failure under increasing self-weight in the geotechnical centrifuge. Models were constructed on either firm or rigid foundations, and different lengths of reinforcement were tested. No pullout failures were observed in any models. In vertical walls failure developed entirely within the reinforced zone when L /H≥ 0.75; in the steeply sloped walls this threshold occurred when L /H≥ 0.67. Models on firm foundations showed better performance than identical models built on rigid foundations. A stability analysis using the simplified, two-dimensional limit-equilibrium simplified Bishop method incorporating reinforcement was found to be a good predictor of the behavior of the models based on calculated factors of safety at failure. The development of tension cracks in the backfill as walls underwent prefailure deformations led to stress concentrations in the geosynthetics and should be avoided in practice.

A full-scale vibration test is conducted to measure the low-amplitude dynamic characteristics of a reinforced concrete cantilever wall-backfill system. Measurements during a frequency sweep are recorded along the wall length. From these measurements, resonant frequencies are identified, along with the corresponding response configurations that depict variation in motion along the wall length. In general, the wall and adjacent backfill zone are observed to move together in-phase. Farther away from the wall, out-of-phase wall-backfill motions are measured at higher resonant frequencies. Finally, retaining systems of uneven height, such as wing walls, are shown clearly to exhibit three-dimensional (3D) seismic response characteristics.

Correlations developed between a simple field test, a 1 point standard Proctor test on air-dry sand, and relative density-test values are presented for 29 filter sands studied. The correlations allow prediction of 70 and 50% relative density values from the field 1 point compaction test value. The field 1 point standard Proctor dry-density value on air-dry sand was greater than the 50% relative density value for all 29 sands tested.

Pumping can occur when clay is compacted wet of optimum. Rather than densifying, the clayey soil squeezes out from underneath the compaction equipment. Adding gravel to the clayey soil creates a granular skeleton that increases the undrained shear strength. The results of this study show that even a partial gravel skeleton can prevent pumping of a clayey soil. Pumping occurred during the modified proctor compaction test when the undrained shear strength was less than 14 kPa (290 psf) and the initial tangent modulus was less than 1,600 kPa. To prevent pumping, the tested clayey soil (sand and montmorillonite mixture) had to contain at least 63% rounded gravel or 54% angular gravel. A lower percentage of angular gravel prevented pumping because it more effectively interlocked and created the necessary gravel skeleton at a lower density than the rounded gravel.