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An adjustable shear stress straight flume commonly used to measure cohesive sediment erosion rates has been modified to include downstream bed load traps. The new flume can be used not only to measure erosion rates, but also to analyze and quantify the modes of transport for this complex problem. The new device was used to study transport modes of quartz particles ranging in size from 19 to 1,250 [micro]m. As expected, the traps captured the coarse material (bed load) and the fine material bypassed the traps (suspended load). Transport properties of natural sediments from three locations were also studied. Fine sediments with little or no sand eroded as aggregates which maintained their integrity in the flume channel while moving as bed load into the traps. Natural sediments that included high percentage of sand also eroded as aggregates. However, these aggregates quickly disaggregated. Sand moved as bed load and fell into the traps while fine particles moved predominately in suspension. DOI: 10.1061/(ASCE)WW.1943-5460.0000054 CE Database subject headings: Bed loads; Sediment; Sand, hydraulic; Silts; Suspended loads. Author keywords: Bed load; Sediment; Sand; Silt; Separation; Transport; Suspension.

Five Austin-style sand filters were constructed by the California Department of Transportation (CALTRANS) as retrofit projects for maintenance yards and park-and-ride facilities in the Los Angeles and San Diego metropolitan areas. Each of these filter systems included storm-water monitoring equipment for collection of flow weighted composite samples. In addition, detailed records were compiled of the design elements, construction costs, and type and amount of maintenance required at each of the sites. The construction costs were relatively high because of the retrofit nature of the project and the integration of the CALTRANS storm-drain system with those of the adjoining metropolitan areas, which eliminated any opportunities for economies of scale. An analysis of performance using linear-regression techniques indicated that for sediment and almost all particle associated constituents, effluent concentration was independent of influent concentration. For instance, the average suspended solids concentration in treated runoff was 7.8 [+ or -] 1.2 mg/L (at the 90% confidence level) regardless of observed influent concentration. The constant effluent quality produced for the particulate constituents indicates that the calculation of a percent reduction is more indicative of the influent concentration rather than the performance of the filter itself. Rejuvenation of the filter bed was required at three sites after 3 years of operation when the solids loading to the system was between 5 and 7.5 kg/[m.sup.2] of filter area. However, the clogging may have been accelerated by problems with the pumps that resulted in standing water on the filter for extended periods. Other maintenance activities consisted mainly of inspections, pump repair, and activities to reduce mosquito breeding. The main impediment to widespread implementation is the initial construction cost; however, modifications of the filter configuration and media may reduce these costs and increase effectiveness, thereby making the technology more attractive. DOI: 10.1061/(ASCE)0733-9496(2003)129:3(234) CE Database subject headings: Sand filters; California; Performance; Costs; Maintenance.

Both the driving response and static bearing capacity of open-ended piles are affected by the soil plug that forms inside the pile during pile driving. In order to investigate the effect of the soil plug on the static and dynamic response of an open-ended pile and the load capacity of pipe piles in general, field pile load tests were performed on instrumented open- and closed-ended piles driven into sand. For the open-ended pile, the soil plug length was continuously measured during pile driving, allowing calculation of the incremental filling ratio for the pile. The cumulative hammer blow count for the open-ended pile was 16% lower than for the closed-ended pile. The limit unit shaft resistance and the limit unit base resistance of the open-ended pile were 51 and 32% lower than the corresponding values for the closed-ended pile. It was also observed, for the open-ended pile, that the unit soil plug resistance was only about 28% of the unit annulus resistance, and that the average unit frictional resistance between the soil plug and the inner surface of the open-ended pile was 36% higher than its unit outside shaft resistance. DOI: 10.1061/(ASCE)1090-0241(2003)129:4(296) CE Database subject headings: Piles driving; Sand; Pipe piles; Static loads; Dynamic loads; Pile load tests.

We present a transport model for mixed sand/gravel sediments. Fractional transport rates are referenced to the size distribution of the bed surface, rather than subsurface, making the model completely explicit and capable of predicting transient conditions. The model is developed using a new data set of 48 coupled observations of flow, transport, and bed surface grain size using five different sediments. The model incorporates a hiding function that resolves discrepancies observed among earlier hiding functions. The model uses the full size distribution of the bed surface, including sand, and incorporates a nonlinear effect of sand content on gravel transport rate not included in previous models. The model shares some common elements with two previous surface-based transport models, but differs in using the full surface size distribution and in that it is directly developed from a relatively comprehensive data set with unambiguous measurement of surface grain size over a range of flow, transport rate, and sediments. DOI: 10.1061/(ASCE)0733-9429(2003) 129:2(120) CE Database keywords: Sediment transport; Models; Sand; Gravel.

A procedure for estimating the undrained stress-strain behavior of sand from drained self-boring pressuremeter and seismic piezocone penetration tests is proposed in this paper. The procedure offers an inexpensive alternative to laboratory testing and avoids the uncertainty of the empirical methods based on index measurements such as the Standard Penetration Test blow count and the tip resistance in a Piezocone Penetration Test (CPTU). To check its validity, the proposed procedure was used to infer the undrained triaxial stress-strain curves and the results were compared with laboratory triaxial tests on undisturbed samples. The undrained limit equilibrium stability of a dike was also assessed using the inferred stress-strain behavior to illustrate the usefulness of the procedure. The result of the stability analysis was found to be in qualitative agreement with the observed performance of the dike during a recent field experiment attempting to trigger static liquefaction. CE Database keywords: Sand; In situ tests; Stress-strain curves; Dikes; Penetration tests.

While successful in removing turbidity and pathogens from drinking water, slow sand filters require ripening periods at the beginning of each filter run. The premise of this research was that it should be possible to enhance the ripening of slow sand filters. Potential ripening agents were screened by assessing their interaction with the surface of filtration media and turbidity particles. Four natural organic polymers and nine synthetic polymers were investigated for their potential to enhance filter ripening. Of the 13 modifying agents considered, none conclusively sorbed to the filter media, and only one, a synthetic polymer, interacted with kaolin particles. A filter modified with continuous feed of the polymer ripened successfully and produced water with turbidity below 1.0 NTU in about 24 h. Most turbidity removal in the treated filter occurred in the schmutz-decke rather than within the depth of the filter bed. Hence, the mechanism of enhanced ripening in this case probably was particle agglomeration with resulting acceleration of particle deposition at the filter surface accompanied by straining or attachment to previously removed particles.

Model tests were performed at the Geotechnical Centrifuge Facility of Delft University of Technology, The Netherlands, to examine the mechanics of light nonaqueous phase liquid (LNAPL) movement in a partially saturated porous granular medium. The experiment simulated a 2D spill of LNAPL in an unsaturated sand prepared at two values of porosity. The duration of the centrifuge model tests corresponded to a prototype equivalent of 110 days. The choice of modeling a 2D flow together with the use of a transparent container enabled direct visual observation of the experiments. Scaling laws developed in connection with other centrifuge modeling studies were used to support the test results. Tests were conducted at two different centrifuge accelerations to verify, by means of the 'modeling of models technique,' the similitude between the different experiments. The paper presents details of the experimental methodologies and the measuring techniques used to evaluate the final distribution of water and LNAPL content in the soils.

This study presents direct evidence for the influence of the previbration cycles induced in the conventional resonant colum tests on the measured dynamic properties of a dry sand. The tests were performed on an energy-injecting virtual-mass resonant column system, under which the material properties can be measured at a very low number of previbration cycles (

The coupled bridge foundation-superstructure finite-element code FLPIER was employed to predict the lateral response of the single piles and 3 x 3 to 7 x 3 pile groups founded in both loose and medium dense sands. The p-multiplier factors suggested by McVay et al. for laterally loaded pile groups with multiple pile rows were implemented for the predictions. The soil parameters were obtained through a back-analysis procedure based on single pile test results. The latter, as well as the numerical predictions of both the single and group tests, are presented. It was found that the numerical code FLPIER did an excellent job of predicting the response of both the single piles and the 3 x 3 to 7 x 3 pile groups. The latter involved the predictions of lateral load versus lateral deflection of the group, the shears and bending moments developed in the individual piles, and the distributions of the lateral loads in each pile row, which were all in good agreement with the measured results.

The ultimate bearing capacity of short, precast concrete piles driven into calcareous sands was examined by pile-load tests carried out at two sites in Kuwait. The piles had a 0.3 m x 0.3 m square cross section and extended to a maximum depth of 12 m. They were driven through a loose-to-compact calcareous surface sand layer underlain by a competent dense-to-very-dense siliceous cemented sand deposit. The pile tips and part of the pile shafts were embedded in the lower layer. The base resistance and shaft friction were calculated using the Meyerhof method for a layered soil profile. The method employs the standard penetration test N values. The results indicate that a great portion of the pile capacity is due to base resistance. The skin friction mobilized is small and consists of two components corresponding to the two layers penetrated along the pile shafts. The calculated pile capacities were very close to the measured values. The unit skin friction is not constant along the pile shafts.

Factors affecting the strength, modulus, stress-strain, and time-to-failure relationships of moist-cured silicate-grouted sands were investigated from short-term and creep tests. Variables included in the short-term tests were curing time, sand gradation and mineralogy, rate of loading, curing time, and confining pressure. Confining pressure was varied up to 550 kPa, and the stress and strain loading rates were varied from 0.05 to 5.0 Pa/min and from 0.01 to 1.0%/min, respectively. The shear strength and failure strain of moist-cured grouted sands were independent of the confining pressure, but they were affected by all other variables investigated. Compressive failure strains for silicate-grouted sands were less than 0.4% and the limitation in improving the compressive strength of sand has been quantified. Grouted limestone sand had the highest strength. The creep behavior of grouted sand was also investigated. Stress-strain and time-to-failure relationships for grouted sands have been developed.

A 1D saturated sand layer of 2 m in thickness, in which a silt seam is sandwiched, is liquefied by an instant shock. It is found that a water film is easily formed beneath the silt seam with a thickness as thin as a few millimeters just after liquefaction in loose sand and that the film lasts longer than the post-liquefaction settlement. The effect of the water film on pore-pressure distribution and sand settlement is intensively studied. 1g shake table tests are then carried out for 2D models with or without seams of silt within a saturated sand layer. In the former case, water films formed beneath silt seams just after liquefaction enable the soil mass above them to glide due to an unbalanced force along the water films, not only during but also after shaking. In the latter case, the soil deforms continuously, mostly during shaking, and stops afterward. Thus, a significant effect of water films formed beneath thin, low-permeability sublayers in a liquefied loose sand, on the failure mode and timing in lateral spread, is clearly demonstrated by these simple model tests.

A general approach has been established to assess the undrained stress-strain curve and effective stress path under monotonic loading from drained triaxial tests. An appropriate formulation of a drained and drained rebounded (i.e., over-consolidated) triaxial test response is developed that, in turn, allows the assessment of developing liquefaction and the undrained behavior of saturated sands. The formulation presented is based upon reported experimental drained test results that were obtained from different investigators using different testing techniques. This formulation is a function of the confining pressure and basic properties of the sand, such as relative density, uniformity coefficient, and particle shape (roundness), which can be obtained from visual inspection. The approach is verified by comparing predicted and reported (observed) undrained behavior. The developed formulas allow one to predict the potential of sand to liquefy, the type of liquefaction, the peak and residual strength values, as well as the whole undrained stress-strain curve and effective stress path. The simplicity of this approach makes it an attractive general method to characterize the undrained behavior of sands in a preliminary analysis with no need to run sophisticated experimental tests.

The potential for changes in the wettability of a subsurface system following exposure of sands to a variety of non-aqueous-phase liquids (NAPLs) was assessed. Many of the NAPLs were collected from field sites with on-going NAPL recovery systems. Three methods were used to evaluate the wetting conditions: contact angle measurements, a qualitative bottle test, and capillary pressure-saturation curves. The results clearly show that a wide range of wetting conditions can be expected following spills of complex NAPL mixtures to the subsurface. NAPLs comprised of higher molecular weight constituents - such as creosote - or with added surfactants - such as gasoline - had a greater impact on the system wettability than the lower molecular weight NAPLs. Neat solvents did not have a significant impact on the wettability of quartz surfaces. Many of the petroleum products tested resulted in the formation of weakly water-wet surfaces. Under these conditions, the potential recovery of NAPL from the subsurface would be maximized. Much lower recoveries would be expected for the NAPL-wetting creosote and coal tar contaminants, however.

This paper presents the soil friction restraint on oblique pipelines in loose sand. A series of experimental tests are conducted in a prefabricated large-scale drag box with dimensions 1.83 m x 1.83 m x 1.22 m. Model pipes 0.61 m long with diameters of 152.4, 228.6, and 304.8 mm are obliquely moved from an axial-longitudinal to lateral-transversal direction in the drag box to study the associated soil restraints of the oblique pipes with various shallow embedded depths. All the test results indicate that for the axial pipes, the longitudinal soil restraint could be estimated as the product of the average of the vertical and horizontal earth pressures at the centerline of the pipe and the tangent value of soil-pipe friction angle, whereas for the lateral pipes, the transversal soil restraint could be predicted by using the limit equilibrium model with the assumption of the planar sliding failure surface. The longitudinal and transversal soil restraints of the oblique pipes could geometrically be obtained by multiplying the corresponding cosine and sine values of the oblique angle with the associated longitudinal soil restraint of axial pipe and the transversal soil restraint of the lateral pipe, respectively. The findings also indicate that the scale effects are not significant for the size of the pipes tested herein.

A recommendation is made to base grouted sand behavior analysis on both partial and total filling of pores to study particulate as well as continuum behavior. Continuum behavior, however, is posited to be optimum for peak stress analysis.