Soil Deformation Measurements Research Articles

Measurement of Soil Deformation at the Ground Contact Surface of a Traveling Wheel

In order to clarify the soil deformation at the ground contact surface, traveling tests using a rubber-coated rigid wheel were carried out with -5%, 5%, 10%, 20% and 40% slip using a sophisticated soil bin test apparatus. The displacement of soil particles at the ground contact surface was observed through the movement of acrylic wires (1 mm in diameter) laid down on the soil surface. PTV (Particle Tracking Velocimetry), an effective image processing technique, was employed to detect the movement of the acrylic wires using image processing of a series of pictures. The detected movement is assumed to coincide with that of soil particles at the same position. Accordingly, the movement of soil particles could be successfully measured and analyzed. In addition, the soil deformation under the wheel was also measured using PIV (Particle Image Velocimetry). Both measures were then analyzed and the characteristics of soil deformation clarified. The mathematical model for the soil displacement at the ground contact surface showed good agreement with the measured values, except for at high slip.

Camera Calibration Using Neural Network for Image-Based Soil Deformation Measurement Systems

Abstract A neural network camera calibration algorithm has been adapted for image-based soil deformation measurement systems. This calibration algorithm provides a highly accurate prediction of object data points from their corresponding image points. The experimental setup for this camera calibration algorithm is rather easy, and can be integrated into particle image velocimetry (PIV) to obtain the full-field deformation of a soil model. The performance of this image-based measurement system was illustrated with a small-scale rectangular footing model. This fast and accurate calibration method will greatly facilitate the application of an image-based measurement system into geotechnical experiments.

Measurement of soil deformation at the contact surface of a traveling wheel

Measurement of soil deformation at the contact surface of a traveling wheel

Measurement of Soil Deformation at the Ground Contact Surface of a Traveling Wheel

Measurement of Soil Deformation at the Ground Contact Surface of a Traveling Wheel

Theoretical Analysis of Fluid Inclusions for In Situ Soil Stress and Deformation Measurements

In situ determination of stress, strength, and deformation of soils for direct assessment of trafficability and susceptibility to compaction has been a long‐standing problem in soil mechanics and agricultural engineering. Despite considerable progress in development of sophisticated probes, data interpretation remains in its infancy due to incomplete understanding of soil–probe interaction. In this study we developed a novel theoretical framework for describing pressure and deformation of fluid inclusions within an elasto‐plastic soil matrix subject to anisotropic remote stresses that provides the basis for development of in situ probes for stress and deformation measurement. Results showed that for a compressible fluid inclusion (e.g., air) embedded in an elastic matrix, inclusion pressure is determined primarily by the matrix mean stress, Poisson's ratio, and the product of matrix bulk modulus and fluid compressibility. For incompressible fluids (e.g., water), inclusion pressure becomes independent of matrix stiffness. Differences in remote stress affect inclusion shape and influence probe pressure for large deformation due to increasing stress concentration. The solution for an elastic matrix also provides upper and lower bounds for inclusion pressure in an elasto‐plastic matrix under isotropic stress. For the more common anisotropic remote stress, inclusion pressure and deformation differ considerably for elastic and elasto‐plastic soil matrix. We found that elastic rubber membranes, often used to separate the fluid inclusion from the matrix, do not influence inclusion pressure or shape as long as membrane and soil stiffness are of similar magnitude. Pressure measurements from laboratory and field experiments using the so‐called Bolling probe agreed well with inclusion pressures predicted by the proposed model.

Soil deformation measurement using particle image velocimetry (PIV) and photogrammetry

A deformation measurement system based on particle image velocimetry (PIV) and close-range photogrammetry has been developed for use in geotechnical testing. In this paper, the theory underlying this system is described, and the performance is validated. Digital photography is used to capture images of planar soil deformation. Using PIV, the movement of a fine mesh of soil patches is measured to a high precision. Since PIV operates on the image texture, intrusive target markers need not be installed in the observed soil. The resulting displacement vectors are converted from image space to object space using a photogrammetric transformation. A series of validation experiments are reported. These demonstrate that the precision, accuracy and resolution of the system are an order of magnitude higher than previous image-based deformation methods, and are comparable to local instrumentation used in element testing. This performance is achieved concurrent with an order of magnitude increase in the number of measurement points that can be fitted in an image. The performance of the system is illustrated with two example applications.

Soil deformation measurement using particle image velocimetry (PIV) and photogrammetry

A deformation measurement system based on particle image velocimetry (PIV) and close-range photogrammetry has been developed for use in geotechnical testing. In this paper, the theory underlying this system is described, and the performance is validated. Digital photography is used to capture images of planar soil deformation. Using PIV, the movement of a fine mesh of soil patches is measured to a high precision. Since PIV operates on the image texture, intrusive target markers need not be installed in the observed soil. The resulting displacement vectors are converted from image space to object space using a photogrammetric transformation. A series of validation experiments are reported. These demonstrate that the precision, accuracy and resolution of the system are an order of magnitude higher than previous image-based deformation methods, and are comparable to local instrumentation used in element testing. This performance is achieved concurrent with an order of magnitude increase in the number of measurement points that can be fitted in an image. The performance of the system is illustrated with two example applications.

SW—Soil and Water: Direct Measurement of Soil Deformation using the Bead-grid Method

Soil compaction is the alteration of physical properties of the soil and has significant effect on crop production. With the introduction of larger and heavier agriculture machinery it is now a problem throughout the world. Significant knowledge is still required to study and develop a model to predict soil compaction. Numerous theoretical models are now available but these are far from being able to resolve practical problems. A combination of experimental study and theoretical calculations may provide a solution and lead to the development of an effective predictive model. In this study, experiments involving bead-grid are used to measure soil deformation under an axial compressive load. Measurement of horizontal and lateral deformations was performed using precision potentiometers and the data transferred to a computer for the plotting of deformation contours and soil deformation analysis. The results show that the bead-grid method provides an effective and accurate means for measuring soil deformation.

Precise measurement of soil deformation and fluctuation in drawbar pull for steel and rubber-coated rigid wheels

The travelling performance of rigid wheels on sand stratum is measured using two kinds of surface material, i.e. steel and steel coated with rubber. A new method for measuring the displacement of soil beneath the wheel has been developed using small polyester film markers. The trajectories of soil particles beneath the wheels are approximated by an exponential function and the fluctuations in the drawbar pull are represented by a sinusoidal function. The amplitude and basic wavelength of the fluctuation in the drawbar pull are discussed for both types of wheels.

A Flexible Strain Gage for Soil Testing

Abstract A novel strain gage for the measurement of soil deformation is introduced. The gage is based on the principle that the change in the length of a coil is linearly related to the change in its inductance. The gage measures a wide range of strains and can be easily installed on a soil specimen in any direction; therefore, it is particularly suitable for the measurement of deformations of in situ subsurface soil. This paper reports the principle and the characteristics of the gage. A discussion on further improvements is also given.

Soil Deformation Measurement by the Moire, Technique

Soil Deformation Measurement by the Moire, Technique