Roman D. Hryciw

Laboratory Measurement of Small Strain Shear Modulus Under K0 Conditions

A new device to measure the small strain shear modulus (Gmax) under a no lateral strain condition has been developed. The techniques for measuring Gmax are discussed, with emphasis on bender element techniques. The performance of the bender elements are compared with results from simultaneous resonant column tests. An in-depth description of the lateral stress measurement system, the Gmax determination technique, and the measurement of vertical strain is presented along with representative test results to demonstrate the performance of the device.

Video tracking for experimental validation of discrete element simulations of large discontinuous deformations

Abstract The discrete element method (DEM) simulates large discontinuous deformations as a natural outcome of discrete particle interactions. The method is well suited for problems such as plowing, penetration and hopper flows. However, verification of DEM simulations has been largely limited to comparisons with laboratory stress-strain diagrams of two dimensional simulations of at most a few thousand ideally-shaped particles. This paper presents an automated video tracking and digital image analysis system that has been developed to obtain soil particle displacement fields and velocities from small-scale laboratory experiments. A three-dimensional simulation of a laboratory plowing experiment is performed in which a one-to-one correspondence is achieved between the number of particles and their size distribution in simulation and physical experiment. The data obtained from the video tracking system are used to evaluate the qualitative and quantitative ability of the simulation to model the experiment kinematics.

Grain-Size Distribution of Granular Soils by Computer Vision

A semi-automated technique for obtaining the grain-size distribution (GSD) of granular soils using computer vision is presented. Backlighted digital images of a soil specimen dispersed over a glass specimen plate are acquired at three different magnifications. Images of the specimen are acquired by placing the specimen plate randomly beneath the field of view of a charged-coupled device (CCD) video camera. The size of particles with projected areas from 50 to 2000 pix2 is measured in each image. Multiple images are acquired at each magnification until the measured size distribution of particles counted at that magnification stabilizes. Probabilistic corrections are then used to obtain a statistically unbiased GSD from the image data obtained at all three magnifications. A comparison of GSD data for two uniform and two nonuniform soils using both computer vision and sieving is presented.

Development of Computer Vision Technique for In Situ Soil Characterization

Construction and rehabilitation of highways, tunnels, and bridges require detailed information about subsurface stratigraphy. This study presents development of a new method for characterizing subsurface soil in situ using computer vision. Hardware and software systems are integrated to obtain the grain-size distribution (GSD) of subsurface soils continuously with depth and to identify small-scale subsurface anomalies. Research is being conducted in three phases. The first phase consists of measuring the GSD of detached cohesionless soil specimens in the laboratory from digital images obtained with a computer vision system (CVS). The second phase uses the CVS to develop image processing and analysis techniques to classify soil assemblies in the laboratory and identify subsurface anomalies by simulating the manner in which images will be acquired in situ. A texture analysis approach has been developed that can detect changes in stratigraphy. The technique has been successful in identifying different types of dry, uniformly graded soils. Finally, a subsurface vision probe is being designed and constructed that will capture video images at three different levels of magnification continuously with depth.

Roundness and Sphericity of Soil Particles in Assemblies by Computational Geometry

AbstractThe use of computational geometry methods for determining soil roundness (R) and sphericity (S) were evaluated and extended to particles segmented from images of three-dimensional particle assemblies. Two Adobe Photoshop lasso tools were used to delineate particles with full projections from the assemblies. Results were in excellent agreement with values published in traditional roundness and sphericity charts, thus confirming that the computational method can replace the much slower and less objective chart methods. Complete volume-based distributions of particle roundness and sphericity were presented for three soils with vastly different particle shapes. Values of R and S obtained from images of three-dimensional assemblies were almost indistinguishable from values obtained using images of detached particles showing their largest projected areas. Mean R values were also computed for 10 different soils of various geologic origins. As expected, crushed sands exhibited the smallest mean values of ...

Evaluation and Quality Control of Dry-Jet-Mixed Clay Soil-Cement Columns by Standard Penetration Test

Dry jet mixing has been widely used since the 1980s for stabilization of soft soil. The quality and strength of the dry-jet-mixed columns must be evaluated to confirm the success of the stabilization. The standard penetration test (SPT) is shown to be a simple and effective method for this task. The strength characteristics along the length of the column were determined, and correlations between the SPT blow count and the unconfined compressive strength were developed.

Microdeformations in Sands by Digital Image Processing and Analysis

Laboratory experiments are typically performed on particulate media to study stress-deformation behavior and to verify or calibrate computer models from controlled or measured boundary stresses and displacements. However, such data do not permit the formation of shear bands, displacement fields within flowing granular media, and other smallscale localized deformation phenomena to be identified. Described are two semiautomated computer vision techniques for accurately determining the two-dimensional displacement field in granular soils from video images obtained through a transparent planar viewing window. The techniques described are applicable for studying the behavior of particulate media under plane strain and certain axisymmetric test conditions. Digital image processing and analysis routines are used in two different computer programs, Tracker and Tracer, Tracker uses a graphical user interface that allows individual particles to be selected and tracked through a sequence of digital video images. A c...

Translucent Segregation Table Test for Sand and Gravel Particle Size Distribution

An image-based method has been developed for rapidly determining the size distribution of coarse sand and gravel. The system utilizes a back-lit tilting “translucent segregation table” (TST) to segregate the particles by size prior to photographing the specimen from above. Most significantly, the soil particles need not to be detached from each other; they only need to rest on the translucent plate in a single layer. An image-processing method called “watershed segmentation” digitally separates the soil particles so that each one is individually accounted for in the resulting size distribution. A sieve-equivalent particle size, which considers the passage of ellipsoids through square sieve openings, is obtained for every particle in the specimen. Twenty soil specimens were tested by the TST and by sieving. Slight differences between sieve and TST results were observed and explanations for the minor discrepancies were explored. Considering that the TST uses a single camera and just one photograph, it appears to be an attractive clean, rapid, and low-cost alternative to sieving.

Laboratory Testing Apparatus for Slopes Stabilized by Anchored Geosynthetics

A laboratory testing apparatus is described for examining slopes subjected to seepage and stabilized by anchored geosynthetics (AGS). The AGS technique can increase the stability of cohesionless slopes such as coastal dunes against surficial erosion and shallow mass failure caused by wave action and seepage forces. In the AGS, a geosynthetic fabric is placed on the face of the slope and tensioned via anchorage to the ground. The required tension is achieved through frictional or pullout resistance of earth anchors that are fastened to the fabric and driven into the underlying soil mass. In the laboratory testing apparatus, however, AGS tensioning is provided by thin wires connected to rigid steel tubes that exert line loads on the fabric. The wires in turn are connected to dead weights “beneath” the slope that simulate anchor loads. The prototype slopes are failed by uniformly decreasing anchor loads while maintaining the seepage gradient and orientation constant. Very good agreement was observed between experimental results and theoretical predictions of the failure mode and the average AGS loads at failure.

Particle roundness and sphericity from images of assemblies by chart estimates and computer methods

AbstractSoil 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 ...