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The FieldSed is an inexpensive portable device for performing an image-based soil particle size analysis. The process, which includes the image analysis, is referred to as SedImaging (short...

A comprehensive model for the index void ratios emax and emin of sands is presented. It is based on a large set of previously published sand properties as well as tests on 25 new materials including glass spheres and two types of rice. The new model uses the index void ratios of perfectly uniform spherical glass beads as baselines to which factors accounting for the three most influential intrinsic soil properties are applied. The three properties are particles roundness, R, sphericity, S, and the coefficient of uniformity, Cu. The following three factors led to the new model’s improvement over previous such efforts: (1) use of sands spanning a wide range of R, S, and Cu values; (2) consideration of the combined and coupled effects of R, S, and Cu; and (3) utilization of a recently developed computational geometry method on digital images to obtain precise values of R and S for large, statistically reliable numbers of particles.

Soil particle roundness (R) and sphericity (S) are two important intrinsic properties that govern a soil’s mechanical behavior. Although R and S have well-established mathematical definitions dating back to the 1930s, the values are much more typically estimated using charts developed in the 1940s and 1950s. The charts, are based on the earlier mathematical definitions. Using these charts, a class of undergraduate civil engineering students at the University of Michigan were asked to estimate (Rc and Sc) from images of twenty geologically and geographically diverse sands spanning a range of actual R and S values. The images were of three-dimensional (3D) assemblies of the sands as they would be found in images taken remotely or in situ. The students’ estimates were statistically analyzed and compared with rigorously determined R and S using a recently developed computational geometry algorithm. Overall, the students’ estimates were scattered, particularly for natural sands exhibiting intermediate ...

Detailed profiles of hydraulic conductivity are recovered from the deployment of direct-push permeameters at the Geohydrologic Experimental and Monitoring Site, Kansas. Measurements with thin tapered tips, and with standard cone penetration test (uCPT) tips, show only minor differences, suggesting that tip-local disturbance effects are small, and that routine uCPT measurements are therefore representative of pristine conditions. Permeameter measurements are correlated against closely deployed uCPT measurements, estimates of hydraulic conductivity from uCPT sounding correlations, and from grain size correlations derived from both vision CPT (VisCPT) and from cone metrics. On-the-fly evaluations of hydraulic conductivity require that the tip-local pressure field is both steady and partially drained. Continuous penetration is shown to yield pore pressures sufficiently close to steady to enable conductivities to be directly determined. Cone metrics of cone resistance, sleeve friction, and pore pressure ratio are shown to be sufficient to discriminate between partially drained and undrained behavior, and therefore to define the permissible regime where conductivities may be determined from uCPT sounding data. Estimates of hydraulic conductivities from uCPT sounding data are shown to correlate with independently measured magnitudes of hydraulic conductivity recovered using the permeameter tests. However, most of hydraulic conductivities from the permeameter tests (4.5 cm length screen) are underpredicted, suggesting that storage effects, the inability to reach a steady state, or the effects of dilation may influence the response. Profiles of hydraulic conductivities evaluated from the on-the-fly method also correlate well with the permeameter measurements. Predictions from soil classification and from VisCPT methods are also capable of estimating conductivities, with soil classifications giving the closest correlations of these two for this particular suite of data.

The generation and dissipation of pore fluid pressures following standard piezocone sounding (uCPT) sounding in silty sands are observed to exhibit many of the characteristics of undrained penetration in dilatant materials; steady excess pore pressures may be subhydrostatic, or may become subhydrostatic during dissipation, and are slow to decay. Enigmatic pore pressure dissipation histories which transit from sub- to supra- and again to subhydrostatic before equilibrating at hydrostatic are consistent with a response where undrained pressures are maximally negative remote from the penetrometer tip. This surprising distribution of induced pore fluid pressures is accommodated in cavity expansion models for a dilating soil. A Mohr-Coulomb constitutive model is established for undrained loading of a soil with pore pressure response defined by Skempton pore pressure parameters. Defined in terms of effective stresses, this allows undrained stresses and pore pressures to be determined following cavity expansion ...

An image-based method has been developed for determination of particle-size distributions of coarse-grained soils in the 0.075–2.0 mm range. The percentage of fines is also determined. The test is referred to as sedimaging because it analyzes an image of a soil that has been rapidly sedimented through water to sort the particles by size. The sorting facilitates image analysis based on wavelet transformation. This paper details the sedimaging hardware, image analysis method, and test procedures. Parallel sedimaging and sieving tests on nine soils of different colors, gradations, and particle shapes showed nearly identical results. Sedimaging holds several advantages over sieving, including decreased testing time, lower energy consumption, less equipment maintenance, and improvement of the work environment.

Significant differential settlements were observed on a flat, undeveloped, generally silty but highly stratified alluvial site in eastern Simi Valley, Calif., due to groundshaking from the 1994 Northridge earthquake. The observed settlements were due to both liquefaction of soil beneath the ground water table and dry shaking of loose soils above it. A nearby strong motion recording station provided highly reliable ground motion data for analysis. Extensive cone penetration tests (CPT) along with occasional seismic cones (SCPT), flat plate dilatometer tests (DMT), and soil sampling were performed. Previously developed methods were adopted for converting the CPT data to equivalent Standard Penetration Test blow count (SPT-N) values for establishing liquefaction potential and predicting settlement. Site specific calibration of CPT data was performed to establish a correlation between CPT readings and the percentage of fines. Contours of predicted ground settlement agreed very well with the location and the observed differential settlements along a ground fissure that developed shortly after the earthquake.

Coastal slopes are subjected to destabilizing forces from wave action, current scour, and exfiltrating ground water. As such, they are vulnerable to both surficial erosion and shallow sliding failure because of their low shear strength near the surface. One way of increasing the stability of these slopes is to increase the confining stress on the ground surface by means of an anchored geosynthetic system (AGS). This approach is less visually and physically intrusive than traditional “hard armor” methods, which in many instances are prohibited in environmentally sensitive areas such as coastal sand dunes. Theoretical relationships for determining required AGS loads and anchorage lengths are presented that can be used to evaluate stability for different soil conditions and seepage directions. Some important variables affecting AGS performance such as failure depth, surface configuration, anchor orientation, and seepage influence on near-surface stability are also described. The theoretical predictions were examined by conducting laboratory stability tests on saturated sand slopes, which were stabilized by an anchored geosynthetic netting and subjected to parallel seepage and tractive surface stresses. Good agreement was observed between predicted and actual anchor loads at failure.

The cone penetration test (CPT) has gained wide acceptance for geotechnical site characterization and measurement of mechanical soil properties in situ. However, unlike the standard penetration test (SPT), soil specimens are not obtained in the CPT. Therefore, the soil type can only be estimated through empirical correlations with CPT sounding data or by retrieving field specimens adjacent to the test location. This technical note describes a new vision cone penetrometer (VisCPT), which permits observation and recording of subsurface images in real time as the VisCPT is pushed into the ground at the CPT standard advance rate of 20 mm/s. A high- and low-magnification miniature charge-coupled device (CCD) camera system housed within the VisCPT provide images with fields of view of 2.3 and 18 mm, respectively (measured diagonally). A field video recording system allows the video sequence from each camera to be recorded in real time on two super VHS (S-VHS) format video recorders. Examples of images acquired ...

Dear Editorial Board Members, reviewers, authors, subscribers, and members of the geotechnical and geoenvironmental engineering communities: Many of you have noticed major changes to the masthead of our Journal over the last few months. My term as Editor-in-Chief expired in January and I am taking the opportunity of this Editorial to introduce Professor Craig Benson as the new Editor-inChief of the Journal of Geotechnical and Geoenvironmental Engineering (JGGE). Craig is a Professor at the University of Wisconsin and is well known and very highly regarded for his pioneering research and teaching in geoenvironmental engineering over the last two decades. Craig was a member of our editorial board in 1995 and an editor from 1996 to 2000. His previous experience has made our transition essentially seamless. As my term comes to a close, I would like to thank the many individuals that made the last 3 years at the helm of JGGE my most professionally rewarding assignment. I was blessed with a group of outstanding and dedicated editors with whom it was a delight to interact on an almost daily basis. Ross Boulanger, Radoslaw Michalowski, Chuck Shackelford, and Jim Withiam were the editors through virtually the entire 3-year period. Each contributed to the Journal not only as a specialist in his areas of expertise, but advised me on the general direction of the Journal and its management. In 2003, Jim turned over his position to Ken Fishman after having served JGGE as an editorial board member since 1994 and an editor since 1996. As most of you know, Jim is the founding editor of the Geo-Institute’s ~GI! magazine GeoStrata and will now be able to devote even more time to stewardship of this GI publication. Only Radoslaw Michalowski’s tenure on the board eclipsed Jim’s. Radoslaw was an editorial board member since 1990 and served as an editor since 1998. While his move to the University of Michigan in 1999 certainly was unrelated to his position with the JGGE , I was fortunate to have a colleague nearby to consult with on JGGE matters. Very recently, Radoslaw’s position was turned over to Professor Joseph Labuz at the University of Minnesota. Ross Boulanger of UC