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Alireza Salehi - One of the best experts on this subject based on the ideXlab platform.
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Cone penetration test in stiff over soft clay in centrifuge test
ASME 2019 38th International Conference on Ocean Offshore and Arctic Engineering OMAE 2019, 2019Co-Authors: Yuxia Hu, Mark Cassidy, Alireza SalehiAbstract:This paper describes a numerical study on soil characterization of stiff over soft clays in centrifuge test using Cone penetration test (CPT), especially when the top stiff layer is thin relative to the centrifuge Cone size. An extensive parametric study was conducted using large deformation finite element (LDFE) analysis, with the Cone penetrating continuously from the soil surface. The LDFE model has been validated against existing physical test data with very good agreement. Since the bottom soft clay was normally thick enough to fully mobilise the ultimate Cone Resistance, its undrained shear strength can be interpreted by the existing approach for Cone deep penetration in a uniform clay layer. Thus, the challenge was to interpret the strength of the top stiff layer, where the layer thickness was not thick enough to fully mobilise its ultimate Resistance. Both top layer thickness ratios (to the Cone diameter) and layer strength ratios were considered in the parametric study. Based on the results from LDFE analyses, the interpretation formula of the undrained shear strength in the top stiff layer was proposed as a set of new bearing factors. The proposed Cone bearing factor was a function of the ratio of the measured peak Cone Resistance in the top layer to the stable/ultimate Cone Resistance in the bottom layer and the ratio between the top layer thickness to the Cone diameter. The formula can be used directly when the top layer thickness was known based on the sample preparation. However, the layer interface can be identified based on the study here, if the top layer thickness was not certain. A design flow chart was provided for interpretations of top clay layer strength and top layer thickness based on the Cone Resistance profile obtained from CPT test.
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Cone penetration test in stiff over soft clay in centrifuge test
ASME 2019 38th International Conference on Ocean Offshore and Arctic Engineering OMAE 2019, 2019Co-Authors: Yuxia Hu, Mark Cassidy, Alireza SalehiAbstract:This paper describes a numerical study on soil characterization of stiff over soft clays in centrifuge test using Cone penetration test (CPT), especially when the top stiff layer is thin relative to the centrifuge Cone size. An extensive parametric study was conducted using large deformation finite element (LDFE) analysis, with the Cone penetrating continuously from the soil surface. The LDFE model has been validated against existing physical test data with very good agreement. Since the bottom soft clay was normally thick enough to fully mobilise the ultimate Cone Resistance, its undrained shear strength can be interpreted by the existing approach for Cone deep penetration in a uniform clay layer. Thus, the challenge was to interpret the strength of the top stiff layer, where the layer thickness was not thick enough to fully mobilise its ultimate Resistance. Both top layer thickness ratios (to the Cone diameter) and layer strength ratios were considered in the parametric study. Based on the results from LDFE analyses, the interpretation formula of the undrained shear strength in the top stiff layer was proposed as a set of new bearing factors. The proposed Cone bearing factor was a function of the ratio of the measured peak Cone Resistance in the top layer to the stable/ultimate Cone Resistance in the bottom layer and the ratio between the top layer thickness to the Cone diameter. The formula can be used directly when the top layer thickness was known based on the sample preparation. However, the layer interface can be identified based on the study here, if the top layer thickness was not certain. A design flow chart was provided for interpretations of top clay layer strength and top layer thickness based on the Cone Resistance profile obtained from CPT test.
Yuxia Hu - One of the best experts on this subject based on the ideXlab platform.
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Cone penetration test in stiff over soft clay in centrifuge test
ASME 2019 38th International Conference on Ocean Offshore and Arctic Engineering OMAE 2019, 2019Co-Authors: Yuxia Hu, Mark Cassidy, Alireza SalehiAbstract:This paper describes a numerical study on soil characterization of stiff over soft clays in centrifuge test using Cone penetration test (CPT), especially when the top stiff layer is thin relative to the centrifuge Cone size. An extensive parametric study was conducted using large deformation finite element (LDFE) analysis, with the Cone penetrating continuously from the soil surface. The LDFE model has been validated against existing physical test data with very good agreement. Since the bottom soft clay was normally thick enough to fully mobilise the ultimate Cone Resistance, its undrained shear strength can be interpreted by the existing approach for Cone deep penetration in a uniform clay layer. Thus, the challenge was to interpret the strength of the top stiff layer, where the layer thickness was not thick enough to fully mobilise its ultimate Resistance. Both top layer thickness ratios (to the Cone diameter) and layer strength ratios were considered in the parametric study. Based on the results from LDFE analyses, the interpretation formula of the undrained shear strength in the top stiff layer was proposed as a set of new bearing factors. The proposed Cone bearing factor was a function of the ratio of the measured peak Cone Resistance in the top layer to the stable/ultimate Cone Resistance in the bottom layer and the ratio between the top layer thickness to the Cone diameter. The formula can be used directly when the top layer thickness was known based on the sample preparation. However, the layer interface can be identified based on the study here, if the top layer thickness was not certain. A design flow chart was provided for interpretations of top clay layer strength and top layer thickness based on the Cone Resistance profile obtained from CPT test.
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Cone penetration test in stiff over soft clay in centrifuge test
ASME 2019 38th International Conference on Ocean Offshore and Arctic Engineering OMAE 2019, 2019Co-Authors: Yuxia Hu, Mark Cassidy, Alireza SalehiAbstract:This paper describes a numerical study on soil characterization of stiff over soft clays in centrifuge test using Cone penetration test (CPT), especially when the top stiff layer is thin relative to the centrifuge Cone size. An extensive parametric study was conducted using large deformation finite element (LDFE) analysis, with the Cone penetrating continuously from the soil surface. The LDFE model has been validated against existing physical test data with very good agreement. Since the bottom soft clay was normally thick enough to fully mobilise the ultimate Cone Resistance, its undrained shear strength can be interpreted by the existing approach for Cone deep penetration in a uniform clay layer. Thus, the challenge was to interpret the strength of the top stiff layer, where the layer thickness was not thick enough to fully mobilise its ultimate Resistance. Both top layer thickness ratios (to the Cone diameter) and layer strength ratios were considered in the parametric study. Based on the results from LDFE analyses, the interpretation formula of the undrained shear strength in the top stiff layer was proposed as a set of new bearing factors. The proposed Cone bearing factor was a function of the ratio of the measured peak Cone Resistance in the top layer to the stable/ultimate Cone Resistance in the bottom layer and the ratio between the top layer thickness to the Cone diameter. The formula can be used directly when the top layer thickness was known based on the sample preparation. However, the layer interface can be identified based on the study here, if the top layer thickness was not certain. A design flow chart was provided for interpretations of top clay layer strength and top layer thickness based on the Cone Resistance profile obtained from CPT test.
Mark Cassidy - One of the best experts on this subject based on the ideXlab platform.
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Cone penetration test in stiff over soft clay in centrifuge test
ASME 2019 38th International Conference on Ocean Offshore and Arctic Engineering OMAE 2019, 2019Co-Authors: Yuxia Hu, Mark Cassidy, Alireza SalehiAbstract:This paper describes a numerical study on soil characterization of stiff over soft clays in centrifuge test using Cone penetration test (CPT), especially when the top stiff layer is thin relative to the centrifuge Cone size. An extensive parametric study was conducted using large deformation finite element (LDFE) analysis, with the Cone penetrating continuously from the soil surface. The LDFE model has been validated against existing physical test data with very good agreement. Since the bottom soft clay was normally thick enough to fully mobilise the ultimate Cone Resistance, its undrained shear strength can be interpreted by the existing approach for Cone deep penetration in a uniform clay layer. Thus, the challenge was to interpret the strength of the top stiff layer, where the layer thickness was not thick enough to fully mobilise its ultimate Resistance. Both top layer thickness ratios (to the Cone diameter) and layer strength ratios were considered in the parametric study. Based on the results from LDFE analyses, the interpretation formula of the undrained shear strength in the top stiff layer was proposed as a set of new bearing factors. The proposed Cone bearing factor was a function of the ratio of the measured peak Cone Resistance in the top layer to the stable/ultimate Cone Resistance in the bottom layer and the ratio between the top layer thickness to the Cone diameter. The formula can be used directly when the top layer thickness was known based on the sample preparation. However, the layer interface can be identified based on the study here, if the top layer thickness was not certain. A design flow chart was provided for interpretations of top clay layer strength and top layer thickness based on the Cone Resistance profile obtained from CPT test.
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Cone penetration test in stiff over soft clay in centrifuge test
ASME 2019 38th International Conference on Ocean Offshore and Arctic Engineering OMAE 2019, 2019Co-Authors: Yuxia Hu, Mark Cassidy, Alireza SalehiAbstract:This paper describes a numerical study on soil characterization of stiff over soft clays in centrifuge test using Cone penetration test (CPT), especially when the top stiff layer is thin relative to the centrifuge Cone size. An extensive parametric study was conducted using large deformation finite element (LDFE) analysis, with the Cone penetrating continuously from the soil surface. The LDFE model has been validated against existing physical test data with very good agreement. Since the bottom soft clay was normally thick enough to fully mobilise the ultimate Cone Resistance, its undrained shear strength can be interpreted by the existing approach for Cone deep penetration in a uniform clay layer. Thus, the challenge was to interpret the strength of the top stiff layer, where the layer thickness was not thick enough to fully mobilise its ultimate Resistance. Both top layer thickness ratios (to the Cone diameter) and layer strength ratios were considered in the parametric study. Based on the results from LDFE analyses, the interpretation formula of the undrained shear strength in the top stiff layer was proposed as a set of new bearing factors. The proposed Cone bearing factor was a function of the ratio of the measured peak Cone Resistance in the top layer to the stable/ultimate Cone Resistance in the bottom layer and the ratio between the top layer thickness to the Cone diameter. The formula can be used directly when the top layer thickness was known based on the sample preparation. However, the layer interface can be identified based on the study here, if the top layer thickness was not certain. A design flow chart was provided for interpretations of top clay layer strength and top layer thickness based on the Cone Resistance profile obtained from CPT test.
Woojin Lee - One of the best experts on this subject based on the ideXlab platform.
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Quantitative assessment of temperature effect on Cone Resistance
Bulletin of Engineering Geology and the Environment, 2013Co-Authors: Changho Lee, Raehyun Kim, Jong-sub Lee, Woojin LeeAbstract:Les mesures d’un pénétromètre à cône à capteur de déformation sont influencées par les variations de température lors de la pénétration. Une technique de compensation de température en temps réel à l’aide d’un capteur de Bragg est proposée pour corriger l’effet de la température sur la résistance de pointe. Un pénétromètre à cône, miniature, équipé d’un capteur de Bragg et d’un capteur de déformation a été développé pour évaluer la technique proposée. Les concepts du dimensionnement comportent la configuration du cône, l’installation des capteurs et le dispositif de compensation de température. Il est montré que la résistance de pointe du cône est significativement affectée par la température, l’erreur augmentant avec les variations de température. La résistance de pointe du cône mesurée par le capteur de Bragg est efficacement corrigée par le dispositif de compensation de température en temps réel. Le profil qc du capteur de déformation indirectement corrigé par le test de re-pénétration est tout à fait similaire au profil compensé en temps réel. On en conclut que le dispositif de compensation de température en temps réel utilisant le capteur de Bragg, est une technique efficace pour obtenir des données fiables à partir de profils de résistance d’un pénétromètre à cône. The measurements of a strain gauge type Cone penetrometer are influenced by the temperature change during penetration. A real-time temperature compensation technique using a fiber Bragg grating (FBG) sensor is suggested to correct the effect of temperature on Cone tip Resistance. A 7-mm micro Cone penetrometer equipped with FBG sensors and electrical strain gauges was developed to evaluate the suggested technique. Design concepts include the Cone configuration, sensor installation and the temperature compensation process. It is shown that the measured Cone tip Resistance is significantly affected by the temperature; the error increasing with increasing temperature change. The Cone tip Resistance measured by the FBG sensor is effectively corrected by the real-time compensation method. The q _c profile of the strain gauge indirectly corrected by the re-penetration test is quite similar to the real-time compensated profile. It is concluded that the proposed real-time temperature compensation using the FBG sensor is an effective technique to obtain reliable Cone tip Resistance profiles.
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Quantitative assessment of temperature effect on Cone Resistance
Bulletin of Engineering Geology and the Environment, 2013Co-Authors: Changho Lee, Raehyun Kim, Jong-sub Lee, Woojin LeeAbstract:The measurements of a strain gauge type Cone penetrometer are influenced by the temperature change during penetration. A real-time temperature compensation technique using a fiber Bragg grating (FBG) sensor is suggested to correct the effect of temperature on Cone tip Resistance. A 7-mm micro Cone penetrometer equipped with FBG sensors and electrical strain gauges was developed to evaluate the suggested technique. Design concepts include the Cone configuration, sensor installation and the temperature compensation process. It is shown that the measured Cone tip Resistance is significantly affected by the temperature; the error increasing with increasing temperature change. The Cone tip Resistance measured by the FBG sensor is effectively corrected by the real-time compensation method. The q c profile of the strain gauge indirectly corrected by the re-penetration test is quite similar to the real-time compensated profile. It is concluded that the proposed real-time temperature compensation using the FBG sensor is an effective technique to obtain reliable Cone tip Resistance profiles.
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Evaluation of State Parameter of Crushable Jeju Sand Using Cone Resistance
Marine Georesources & Geotechnology, 2011Co-Authors: Moonjoo Lee, Sungjin Hong, Raehyun Kim, Woojin LeeAbstract:This study was performed to evaluate the critical state parameter of crushable Jeju sand and to suggest the relationship between the state parameter and Cone Resistance of Jeju sand. It is observed from a drained triaxial test that Jeju sand mainly shows contractive behavior due to high void ratio and large compressibility. Although strain localization is not evident, the particle crushing results in a lower void ratio than the critical state void ratio of some Jeju specimens. Critical state parameters of Jeju sand are similar to those of calcareous sands, but significantly larger than those of common sands. The relationship between the normalized Cone Resistance and state parameter of Jeju sand significantly differs from that of other materials, and this relation appears to be affected by the stress level. This is because the variation of stress level affects the state parameter of Jeju sand more significantly than that of common sand due to the high compressibility of Jeju sand.
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Penetration rate effects on Cone Resistance measured in a calibration chamber
2010Co-Authors: Rodrigo Salgado, Monica Prezzi, K. Kim, Woojin LeeAbstract:In this paper, the effects of penetration rate on Cone Resistance in satu- rated clayey soils were investigated by performing miniature Cone penetration tests in a calibration chamber. These tests, using both a conical and flat-tip penetrometers, were performed at nine and eight different penetration rates, respectively, in two spe- cimens prepared by mixing kaolin clay and Jumunjin sand with different mixing ra- tios and consolidated to a K0 condition. The mixing ratios of these two specimens were decided based on results of flexible-wall permeameter tests performed on clayey sand mixtures prepared at various mixing ratios. A correlation between Cone resis- tance and drainage conditions was established based on the Cone penetration test re- sults. The transition from no drainage to partial drainage and from partial drainage to full drainage were defined as a function of penetration rate normalized with respect to the penetrometer diameter and the coefficient of consolidation.
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Effect of Stress History on CPT-DMT Correlations in Granular Soil
Journal of the Korean Geotechnical Society, 2010Co-Authors: Moonjoo Lee, Sungkun Choi, Min-tae Kim, Ju-hyeong Lee, Woojin LeeAbstract:Stress history increases the residual horizontal stress of granular soil and, consequently, the penetration Resistance. This study analyzes the effect of stress history on the Cone Resistance (qc), horizontal stress index (KD) and dilatometer modulus (ED) of CPT and DMT from calibration chamber specimen in OC as well as NC state. Test results show that the normalized Cone Resistance by mean effective stress correlates well with the relative density and the state parameter, whereas the normalized Cone Resistance by vertical effective stress is a little affected by stress history. The influence of stress history is more reflected on KD than ED and qc. The KD/K0, in which the effect of stress history on KD is compensated by the at-rest coefficient of earth pressure, K0, is related to relative density, state parameter and the normalized Cone Resistance by mean effective stress. It is also observed that the normalized dilatometer modulus by mean effective stress (ED/σm') shows a unique correlation with the state parameter, regardless of stress history.
Yong Hoon Byun - One of the best experts on this subject based on the ideXlab platform.
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Instrumented Cone Penetrometer for Dense Layer Characterization.
Sensors, 2020Co-Authors: Jong-sub Lee, Yong Hoon ByunAbstract:Subsurface characterization is essential for a successful infrastructure design and construction. This paper demonstrates the use of an instrumented Cone penetrometer (ICP) for a dense layer characterization at two sites. The ICP consists of a Cone tip and rods equipped with an accelerometer and four strain gauges, which allow dynamic driving, in addition to quasi-static pushing of the Cone. The force and velocity of the Cone are measured using the ICP instrumentation and compared with the N value, dynamic Cone penetration index, and static Cone Resistance. A strong correlation has been observed between the total Cone Resistance estimated from the ICP and the dynamic Cone penetration index and static Cone Resistance. After the correction of the dynamic Cone Resistance effect, the static component of the total Cone Resistance can be used as an alternative to a static Cone Resistance. This novel approach of soil Resistance estimation using the ICP may be useful for dense layer characterization.
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Assessing subgrade strength using an instrumented dynamic Cone penetrometer
Soils and Foundations, 2019Co-Authors: Jong-sub Lee, Sangyeob Kim, Won Taek Hong, Yong Hoon ByunAbstract:Abstract Subgrade strength is an important aspect to be considered when designing unsurfaced roads and working platforms for pavement structures. Furthermore, dynamic Cone penetration tests are used to characterize the subgrade strength. However, the results of dynamic Cone penetration tests, including the penetration depth per blow, can be affected by transferred energy and the verticality of the Cone penetrometer. The objective of this paper is to characterize the subgrade strength using an instrumented dynamic Cone penetrometer (DCP). The instrumented DCP includes a load cell and an accelerometer, located on the Cone tip, and measures the dynamic responses of force and velocity over elapsed time. Weathered soil is compacted with three different dry unit weights in a square-shaped container for lab-scale dynamic Cone penetration tests. Using instrumented and standard DCPs, several dynamic Cone penetration tests are performed, and the dynamic Cone penetration index (DCPI) is recorded along the depth profiles. Based on the dynamic responses at the Cone tip of the instrumented DCP and the principles of energy conservation, the dynamic Cone Resistance is suggested as a new strength index. The experimental results show that the dynamic Cone Resistance increases with the depth of the instrumented DCP, providing a reliable subgrade strength profile in the soil. In addition, the correlation between the DCPI obtained from the instrumented DCP and the dynamic Cone Resistance suggests that the dynamic Cone Resistance is more sensitive than the DCPI for stiff soil. Based on the correlation values of the dynamic Cone Resistance obtained from the instrumented DCP, the internal friction angle and California bearing ratio values can be estimated with a high degree of reliability. This study demonstrates that use of the instrumented DCP may be a promising in situ testing method for the reliable characterization of subgrade strength.
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Study on Correlation between Dynamic Cone Resistance and Shear Strength for Frozen Sand-Silt Mixtures under Low Confining Stress
Journal of the Korean Geoenvironmental Society, 2016Co-Authors: Sangyeob Kim, Jong-sub Lee, Seung-seo Hong, Yong Hoon ByunAbstract:Investigation of in-situ ground in cold region is difficult due to low accessibility and environmental factors. In this study, correlation between dynamic Cone Resistance and shear strength is suggested to estimate the strength of frozen soils by using instrumented dynamic Cone penetrometer. Tests were conducted in freezing chamber after preparing sand-silt mixture with 2.3% water content. Vertical stresses of 5 kPa and 10 kPa were applied during freezing, shearing, and penetration phase to compare the dynamic Cone Resistance and shear strength. The dynamic Cone Resistance, additionally, is calculated to minimize the effect of energy loss during hammer impact. Experimental results show that as the shear strength increases, the dynamic Cone penetration index (DCPI) decreases nonlinearly, while the dynamic Cone Resistance increases linearly. This study provides the useful correlation to evaluate strength properties of the frozen soils from the dynamic Cone penetration and direct shear tests.