Jairo Espitia - Academia.edu (original) (raw)
Papers by Jairo Espitia
PanAm Unsaturated Soils 2017, 2018
Rock Mechanics and Rock Engineering, 2018
The uniaxial compressive strength of Belencito claystone was studied through stress control and s... more The uniaxial compressive strength of Belencito claystone was studied through stress control and suction control path tests. Short-term uniaxial compression tests on conditioned specimens at different values of suction and long-term hydro-mechanical tests using a climatic box were performed. Volumetric deformation data and acoustic emission measurements from the short-term tests were used to determine σ CD (crack damage stress threshold). Regardless of the level of suction, the σ CD threshold occurred between 70 and 83% of the σ peak.short-term. The experimental results confirmed that the interpretation made by Brace and Bombolakis (
Geophysical Research Letters, 2017
According to field measurements, the basic character of the particle size distributions obtained ... more According to field measurements, the basic character of the particle size distributions obtained from the landslide accumulations is fractal. The collapse of the granular columns with fractal particle size distribution (FPSD) is performed numerically and experimentally to form dry granular flows and the mechanism of how FPSD affects the particle movements is then investigated. Numerical and experimental analyses show that particle flow mobility increases as the fractal dimension increases. Several linear relationships exist between the fractal dimension and flow mobility parameters. By analyzing the kinetics of granular flows, it is found that a large number of small-sized particles will form a boundary layer where the particle shearing and velocities are remarkably increased and will thus have a lubricant effect on the flow mobility. Moreover, the number of particle collisions increases, and small-sized particles are more likely to obtain higher spreading velocities via the greater contribution of particle interactions.
Géotechnique Letters, 2017
Poisson's ratio is an important parameter for the study of the behaviour of rocks in various ... more Poisson's ratio is an important parameter for the study of the behaviour of rocks in various contexts of rock engineering. Some studies have indicated that suction has an effect on Poisson's ratio of argillaceous rocks and that there is a non-linear response of this feature for other types of rocks during the loading process. Nevertheless, an assessment that couples the dependence of Poisson's ratio on stress and suction is still lacking. This study addresses this through a detailed analysis of axial and radial deformations during uniaxial compression tests on specimens at equilibrium under several different suction conditions using the moving point regression technique. Experimental results show a non-linear variation of Poisson's ratio with stress and that suction has a significant influence on it. The model proposed to couple the effect of suction and stress on Poisson's ratio of argillaceous rocks presents higher prediction performance.
EPJ Web of Conferences, 2017
This study presents an experimental analysis on the influence of the particle size distribution (... more This study presents an experimental analysis on the influence of the particle size distribution (psd) on the mobility of dry granular materials. The psd obeys a power law of the form: N(L>d)=kd-Df , where N is the number of particles with diameter L greater than a given diameter d, k is a proportionality constant, and D f is the fractal dimension of the psd. No laboratory or numerical study has been conducted to date analysing how a fractal psd influences the mobility of granular flows as in the case of rock avalanches. In this study, the flow characteristics of poly-dispersed granular materials that have a fractal psd were investigated in the laboratory. Granular mixtures having different fractal psd values were placed in a hollow cylinder. The cylinder was lifted and the distance of flow of the mixture was measured with respect to the original position of the cylinder. It was determined that the distance of flow of the mixtures was directly related to their fractal psd values. That is, the larger the distance of flow of the mixture, the larger is the fractal psd of the granular mixture tested. Thus, the fractal psd in dry granular mixtures seems to have a large influence on the easiness by which dry granular mixtures move in the field.
Springer Series in Geomechanics and Geoengineering, 2017
Shales and stiff clays when deformed under direct shear stress conditions develop narrow shear zo... more Shales and stiff clays when deformed under direct shear stress conditions develop narrow shear zones within which different sets of discontinuities or cracks are present. These cracks form in the shear zone in a progressive manner. In the first stage of deformation, a small set of unconnected cracks called Riedel shears form. In the second stage of deformation, a series of cracks called Thrust shears form. They connect with the Riedel shears. In the third stage of deformation, The Riedel and Thrust discontinuities interact, forming an undulating and rough failure surface. In this study, the fractal dimension concept from fractal theory is used to evaluate the progressive degree of cracking in the shear zone that causes the failure of shales and stiff clays forming part of natural slopes and earth dams. It was established that the intensity of cracking in the samples was reflected in the fractal dimension values. High levels of cracking were associated with high values of the fractal dimension.
Springer Series in Geomechanics and Geoengineering, 2017
The paper studies the hydromechanical behaviour of an argillaceous rock from the Colombian Andes.... more The paper studies the hydromechanical behaviour of an argillaceous rock from the Colombian Andes. The influence of total suction on some physical/mechanical properties is analyzed on an argillaceous rock from the Colombian Andes. A wetting path was applied to the rocks using the vapor transfer technique. Uniaxial compression tests were conducted on specimens at different levels of suction. Also, microstructural observations are carried out using a Mercury Intrusion Porosimeter Apparatus. Results from the laboratory tests indicate that anisotropic deformations took place during the wetting path. Also, total suction contributed to a considerable and non-linear reduction in the peak compressive stress, elastic modulus and stress thresholds of the tested samples. Microstructural analysis indicated the influence of suction on the dominant pores.
Unsaturated Soils: Research & Applications, 2014
PanAm Unsaturated Soils 2017, 2018
Rock Mechanics and Rock Engineering, 2018
The uniaxial compressive strength of Belencito claystone was studied through stress control and s... more The uniaxial compressive strength of Belencito claystone was studied through stress control and suction control path tests. Short-term uniaxial compression tests on conditioned specimens at different values of suction and long-term hydro-mechanical tests using a climatic box were performed. Volumetric deformation data and acoustic emission measurements from the short-term tests were used to determine σ CD (crack damage stress threshold). Regardless of the level of suction, the σ CD threshold occurred between 70 and 83% of the σ peak.short-term. The experimental results confirmed that the interpretation made by Brace and Bombolakis (
Geophysical Research Letters, 2017
According to field measurements, the basic character of the particle size distributions obtained ... more According to field measurements, the basic character of the particle size distributions obtained from the landslide accumulations is fractal. The collapse of the granular columns with fractal particle size distribution (FPSD) is performed numerically and experimentally to form dry granular flows and the mechanism of how FPSD affects the particle movements is then investigated. Numerical and experimental analyses show that particle flow mobility increases as the fractal dimension increases. Several linear relationships exist between the fractal dimension and flow mobility parameters. By analyzing the kinetics of granular flows, it is found that a large number of small-sized particles will form a boundary layer where the particle shearing and velocities are remarkably increased and will thus have a lubricant effect on the flow mobility. Moreover, the number of particle collisions increases, and small-sized particles are more likely to obtain higher spreading velocities via the greater contribution of particle interactions.
Géotechnique Letters, 2017
Poisson's ratio is an important parameter for the study of the behaviour of rocks in various ... more Poisson's ratio is an important parameter for the study of the behaviour of rocks in various contexts of rock engineering. Some studies have indicated that suction has an effect on Poisson's ratio of argillaceous rocks and that there is a non-linear response of this feature for other types of rocks during the loading process. Nevertheless, an assessment that couples the dependence of Poisson's ratio on stress and suction is still lacking. This study addresses this through a detailed analysis of axial and radial deformations during uniaxial compression tests on specimens at equilibrium under several different suction conditions using the moving point regression technique. Experimental results show a non-linear variation of Poisson's ratio with stress and that suction has a significant influence on it. The model proposed to couple the effect of suction and stress on Poisson's ratio of argillaceous rocks presents higher prediction performance.
EPJ Web of Conferences, 2017
This study presents an experimental analysis on the influence of the particle size distribution (... more This study presents an experimental analysis on the influence of the particle size distribution (psd) on the mobility of dry granular materials. The psd obeys a power law of the form: N(L>d)=kd-Df , where N is the number of particles with diameter L greater than a given diameter d, k is a proportionality constant, and D f is the fractal dimension of the psd. No laboratory or numerical study has been conducted to date analysing how a fractal psd influences the mobility of granular flows as in the case of rock avalanches. In this study, the flow characteristics of poly-dispersed granular materials that have a fractal psd were investigated in the laboratory. Granular mixtures having different fractal psd values were placed in a hollow cylinder. The cylinder was lifted and the distance of flow of the mixture was measured with respect to the original position of the cylinder. It was determined that the distance of flow of the mixtures was directly related to their fractal psd values. That is, the larger the distance of flow of the mixture, the larger is the fractal psd of the granular mixture tested. Thus, the fractal psd in dry granular mixtures seems to have a large influence on the easiness by which dry granular mixtures move in the field.
Springer Series in Geomechanics and Geoengineering, 2017
Shales and stiff clays when deformed under direct shear stress conditions develop narrow shear zo... more Shales and stiff clays when deformed under direct shear stress conditions develop narrow shear zones within which different sets of discontinuities or cracks are present. These cracks form in the shear zone in a progressive manner. In the first stage of deformation, a small set of unconnected cracks called Riedel shears form. In the second stage of deformation, a series of cracks called Thrust shears form. They connect with the Riedel shears. In the third stage of deformation, The Riedel and Thrust discontinuities interact, forming an undulating and rough failure surface. In this study, the fractal dimension concept from fractal theory is used to evaluate the progressive degree of cracking in the shear zone that causes the failure of shales and stiff clays forming part of natural slopes and earth dams. It was established that the intensity of cracking in the samples was reflected in the fractal dimension values. High levels of cracking were associated with high values of the fractal dimension.
Springer Series in Geomechanics and Geoengineering, 2017
The paper studies the hydromechanical behaviour of an argillaceous rock from the Colombian Andes.... more The paper studies the hydromechanical behaviour of an argillaceous rock from the Colombian Andes. The influence of total suction on some physical/mechanical properties is analyzed on an argillaceous rock from the Colombian Andes. A wetting path was applied to the rocks using the vapor transfer technique. Uniaxial compression tests were conducted on specimens at different levels of suction. Also, microstructural observations are carried out using a Mercury Intrusion Porosimeter Apparatus. Results from the laboratory tests indicate that anisotropic deformations took place during the wetting path. Also, total suction contributed to a considerable and non-linear reduction in the peak compressive stress, elastic modulus and stress thresholds of the tested samples. Microstructural analysis indicated the influence of suction on the dominant pores.
Unsaturated Soils: Research & Applications, 2014