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Mark Randolph - One of the best experts on this subject based on the ideXlab platform.
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apparatus for measuring pipe soil interaction behavior using shallow pipe like Penetrometers
Geotechnical Testing Journal, 2020Co-Authors: Mark Andreas Schneider, Sa Stanier, David White, Mark RandolphAbstract:Reliable characterization of surficial marine sediments is essential to ensure the safe and economical design of subsea infrastructure for offshore energy facilities (e.g., seabed cables, pipelines, and shallow foundations). Conventional in-situ testing methods (e.g., cone penetrometer test or T-bar) require careful interpretation to account for the effects of shallow embedment, whereas laboratory tests are affected by sampling-induced disturbances, the impact of which can be significant at the low stress levels relevant to the design of subsea infrastructure. This article describes two novel box-core–sized shallow Penetrometers—the hemiball and toroid—which mimic the shape of subsea pipelines and have been designed to reliably measure the strength, consolidation, and frictional properties of surficial offshore sediments. The development and specification of the actuator used to operate these probes is also described. Another major benefit of these Penetrometers, which are intended to be used offshore for on-deck testing aboard a survey vessel, is their capability to generate effective stress interpretations of the soil behavior, and this is made possible because pore pressure transducers are installed and monitored throughout testing. The results of a first laboratory proof test are presented to illustrate the potential of this novel sensor concept.
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ELASTOPLASTIC CONSOLIDATION SOLUTIONS FOR SCALING FROM SHALLOW Penetrometers TO PIPELINES
Canadian Geotechnical Journal, 2017Co-Authors: Y. Yan, David White, Mark RandolphAbstract:The build-up of friction on seabed pipelines is an important design consideration, affecting their stability and the resulting in-service strain and fatigue. The consolidation beneath a partially embedded pipeline has been investigated in the past and linked to the build-up of axial pipe–soil resistance. This paper extends previous work by providing solutions for consolidation around a new class of shallow penetrometer, to provide a basis to scale from site investigation results directly to the build-up of pipeline friction. Small-strain finite element analyses, using the Modified Cam Clay soil model, are presented for the novel toroid and ball Penetrometers. The effects of initial penetrometer embedment, device roughness, strength gradient, and overload ratio have been explored in a comprehensive manner, and are compared with pipe results. The toroid penetrometer shows excellent agreement with an element of an infinitely long pipe, simplifying the scaling process. The ball penetrometer shows a faster con...
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numerical analysis of Penetrometers free falling into soil with shear strength increasing linearly with depth
Computers and Geotechnics, 2016Co-Authors: Mark Randolph, M H Moavenian, M Nazem, J P CarterAbstract:Abstract Dynamic Penetrometers have been used for offshore oil and gas industry applications such as pipeline feasibility studies and anchoring systems, and military applications including naval mine countermeasures and terminal ballistic studies. The main challenge of using dynamic Penetrometers is the interpretation of their test results in order to deduce the mechanical properties of the penetrated soil via empirical or theoretical relations. Recently, a robust numerical method based on the Arbitrary Lagrangian–Eulerian (ALE) technique has been developed for analysing dynamic penetration problems and used to investigate a smooth penetrometer free falling into a uniform layer of clayey soil. Numerical as well as experimental results indicate that the penetration characteristics, including the impact energy, total time, and total depth of penetration, depend on the mechanical properties of the soil including its stiffness and strength parameters as well as the geometry of the penetrometer and its initial impact energy. In this study, the ALE method is employed to study the effect of shear strength increasing with depth (a common condition of seabed deposits) on the penetration characteristics of a free falling penetrometer. Conducting more than two thousand numerical simulations has shown that there is an approximate quadratic relation between the final embedment depth of a FFP penetrating into a non-uniform clay soil and the combined kinetic energy on contact with the soil and subsequent loss in potential energy of the penetrometer.
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numerical analysis of Penetrometers free falling into soil with shear strength increasing linearly with depth
Computers and Geotechnics, 2016Co-Authors: Mark Randolph, M H Moavenian, M Nazem, J P CarterAbstract:Abstract Dynamic Penetrometers have been used for offshore oil and gas industry applications such as pipeline feasibility studies and anchoring systems, and military applications including naval mine countermeasures and terminal ballistic studies. The main challenge of using dynamic Penetrometers is the interpretation of their test results in order to deduce the mechanical properties of the penetrated soil via empirical or theoretical relations. Recently, a robust numerical method based on the Arbitrary Lagrangian–Eulerian (ALE) technique has been developed for analysing dynamic penetration problems and used to investigate a smooth penetrometer free falling into a uniform layer of clayey soil. Numerical as well as experimental results indicate that the penetration characteristics, including the impact energy, total time, and total depth of penetration, depend on the mechanical properties of the soil including its stiffness and strength parameters as well as the geometry of the penetrometer and its initial impact energy. In this study, the ALE method is employed to study the effect of shear strength increasing with depth (a common condition of seabed deposits) on the penetration characteristics of a free falling penetrometer. Conducting more than two thousand numerical simulations has shown that there is an approximate quadratic relation between the final embedment depth of a FFP penetrating into a non-uniform clay soil and the combined kinetic energy on contact with the soil and subsequent loss in potential energy of the penetrometer.
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Penetration Resistance and Stiffness Factors for Hemispherical and Toroidal Penetrometers in Uniform Clay
International Journal of Geomechanics, 2011Co-Authors: Y. Yan, David White, Mark RandolphAbstract:This paper reports numerical analyses of shallowly embedded hemispherical and toroidal Penetrometers under torsional and vertical load. These novel Penetrometers are a new design suited to the assessment of near-surface soil strength and are aimed at the analysis of pipeline embedment and axial pipe-soil interaction. The geometry of the Penetrometers avoids the complication of end effects that arise if a short pipe segment is used, as is the current practice. The operation of these devices involves vertical penetration typically of up to half a diameter, followed by rotation about the vertical axis, whereas the corresponding loads are recorded. The FE analyses explore the undrained bearing capacity and stiffness factors required for the measured loads to be converted to soil strength and stiffness for application in design. On the basis of these analyses, the geometry of the toroidal penetrometer has been optimized to minimize the size of the instrument and limiting interference across the toroid, which would hamper comparisons between the penetrometer response and a pipeline. It is shown that a relatively compact toroid can be used.
Abbas Hemmat - One of the best experts on this subject based on the ideXlab platform.
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A horizontal multiple-tip penetrometer for on-the-go soil mechanical resistance and acoustic failure mode detection
Soil and Tillage Research, 2014Co-Authors: Abbas Hemmat, Tayebeh Rahnama, Zahra VahabiAbstract:Abstract Soil mechanical resistance can be used as an indicator of soil compaction. For on-the-go mapping of spatial variability in soil compaction, single and multiple-tip horizontal Penetrometers have been developed and used to measure the soil mechanical resistance. However, it has been reported that the measured soil resistance in different soil layers depends not only on the degree of soil compactness but also on soil failure mode induced by the shank of the sensor. It was hypothesized that the differences in sound signals collected by microphones during penetration tests could be used to differentiate the failure modes. In this research, an acoustic multiple-tip horizontal penetrometer was developed, with three 30° prismatic tips attached horizontally to S-shape load cells and worked at depths of 10, 20 and 30 cm. The tips working at 10 and 30 cm depths were also fitted with microphones. The sensor was tested in a field with a clay loam soil. The sound signal was first de-noised using wavelet method, and then frequency spectrum and power spectral density of the signals were obtained by fast Fourier transform and Welsh's method, respectively. When the prismatic tips were operated below the critical depth of the sensor (tips at depths of 20 and 30 cm), there was a significant relationship between horizontal resistance index (HRI) and the cone index measured by a vertically-operated cone penetrometer; whereas for the shallower depth (10 cm) the relationship was not significant. The power of the sound recorded of the tip passing through the disturbed soil above the critical depth (10 cm) was much lower than when the tip was penetrating the undisturbed soil located below the critical depth (30 cm). The increase in power of the acoustic signal with depth was in line with the increase in the measured HRI. It can be concluded that the developed combined acoustic penetrometer can both detect soil failure mode and measure soil horizontal resistance.
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Influence of failure mode induced by a horizontally operated single-tip penetrometer on measured soil resistance.
Soil and Tillage Research, 2009Co-Authors: Abbas Hemmat, A. Khorsandy, A.a. Masoumi, Viacheslav I. AdamchukAbstract:Abstract Excessive soil compaction has negative effects for agriculture and the environment. Measurement of soil strength is a common indirect measure of soil compactness. In the context of precision farming, on-the-go soil mechanical resistance measurements using single- and multiple-tip horizontal sensors have been developed. It has been reported that there was a significant relationship between soil mechanical resistance values measured with both vertically operated cone penetrometer and horizontally operated sensors only for relatively deep layers. It was hypothesized that the differences in horizontally measured soil resistance in different soil layers could be explained by different failure modes. The objective of this research was to develop a horizontal soil mechanical resistance sensor and to observe the failure mode in front of it while penetrating soil at three different depths. A single-tip horizontal penetrometer was equipped with a 30° prismatic tip and had a base area of 324 mm 2 . The prismatic tip was mounted horizontally to an S-shaped load cell housed inside a shank. A data-logging system was also developed to record measurements with 10 Hz sampling rate. The sensor was tested in a field with silty clay loam soil at three depths of 20, 25 and 30 cm. Cone index (CI) values were obtained with 1 cm depth increments and 1 m horizontal intervals along each transect for comparison using a standard cone penetrometer. The results showed that average horizontal soil mechanical resistance index (HRI) values for both depths of 20 and 25 cm were similar due to the brittle failure mode in both cases. However, when the tip was operated below the critical depth of the sensor, the value of HRI at 30 cm depth increased three times when compared with 20 or 25 cm depth values. This was due to change in failure mode from brittle to compressive mode below the critical depth. There was a significant relationship ( R 2 = 0.75) between HRI and CI for the 30-cm depth, whereas for shallower depths the relation was not significant. It can be concluded that the correlation between measurements obtained with the vertically and horizontally operated Penetrometers would be significant as long as both produced the same soil failure mode.
Viacheslav I. Adamchuk - One of the best experts on this subject based on the ideXlab platform.
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Influence of failure mode induced by a horizontally operated single-tip penetrometer on measured soil resistance.
Soil and Tillage Research, 2009Co-Authors: Abbas Hemmat, A. Khorsandy, A.a. Masoumi, Viacheslav I. AdamchukAbstract:Abstract Excessive soil compaction has negative effects for agriculture and the environment. Measurement of soil strength is a common indirect measure of soil compactness. In the context of precision farming, on-the-go soil mechanical resistance measurements using single- and multiple-tip horizontal sensors have been developed. It has been reported that there was a significant relationship between soil mechanical resistance values measured with both vertically operated cone penetrometer and horizontally operated sensors only for relatively deep layers. It was hypothesized that the differences in horizontally measured soil resistance in different soil layers could be explained by different failure modes. The objective of this research was to develop a horizontal soil mechanical resistance sensor and to observe the failure mode in front of it while penetrating soil at three different depths. A single-tip horizontal penetrometer was equipped with a 30° prismatic tip and had a base area of 324 mm 2 . The prismatic tip was mounted horizontally to an S-shaped load cell housed inside a shank. A data-logging system was also developed to record measurements with 10 Hz sampling rate. The sensor was tested in a field with silty clay loam soil at three depths of 20, 25 and 30 cm. Cone index (CI) values were obtained with 1 cm depth increments and 1 m horizontal intervals along each transect for comparison using a standard cone penetrometer. The results showed that average horizontal soil mechanical resistance index (HRI) values for both depths of 20 and 25 cm were similar due to the brittle failure mode in both cases. However, when the tip was operated below the critical depth of the sensor, the value of HRI at 30 cm depth increased three times when compared with 20 or 25 cm depth values. This was due to change in failure mode from brittle to compressive mode below the critical depth. There was a significant relationship ( R 2 = 0.75) between HRI and CI for the 30-cm depth, whereas for shallower depths the relation was not significant. It can be concluded that the correlation between measurements obtained with the vertically and horizontally operated Penetrometers would be significant as long as both produced the same soil failure mode.
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On-the-Go Mapping of Soil Mechanical Resistance Using a Linear Depth Effect Model
Transactions of the ASABE, 2008Co-Authors: Viacheslav I. Adamchuk, Kenneth A. Sudduth, Troy J. Ingram, Sun-ok ChungAbstract:An instrumented blade sensor was developed to map soil mechanical resistance as well as its change with depth. The sensor has become a part of the Integrated Soil Physical Properties Mapping System (ISPPMS), which also includes an optical reflectance and a capacitor-based sensor implemented to determine spatial variability in soil organic mater and water content, respectively. The instrumented blade of the ISPPMS was validated in laboratory conditions by applying known loads. It was also tested in the field by comparing sensor-based estimates with measurements produced using a standard vertical cone penetrometer and another on-the-go sensor, the Soil Strength Profile Sensor (SSPS), consisting of five prismatic-tip horizontal Penetrometers located at fixed depths. The comparison resulted in reasonable linear relationships between corresponding parameters determined using the three different methods. The coefficient of determination (r2) for average soil mechanical resistance was 0.32 and 0.57 when ISPPMS-based estimates were compared with the standard cone penetrometer and the alternative on-the-go sensor (SSPS), respectively. Depth gradients of soil mechanical resistance obtained using cone penetrometer and ISPPMS methods were correlated with r2 = 0.33. Observed differences in estimated parameters were due in part to the difficulties with obtaining data representing the same depths and in part to differences in sensor geometry and operating conditions, particularly when comparing the on-the-go sensors to the cone penetrometer. Based on its operation during Missouri field mapping, the instrumented blade proved to be a rugged and inexpensive sensor suitable for studying the spatial variability of the physical state of soils in the upper 30 cm of the profile.
Zahra Vahabi - One of the best experts on this subject based on the ideXlab platform.
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A horizontal multiple-tip penetrometer for on-the-go soil mechanical resistance and acoustic failure mode detection
Soil and Tillage Research, 2014Co-Authors: Abbas Hemmat, Tayebeh Rahnama, Zahra VahabiAbstract:Abstract Soil mechanical resistance can be used as an indicator of soil compaction. For on-the-go mapping of spatial variability in soil compaction, single and multiple-tip horizontal Penetrometers have been developed and used to measure the soil mechanical resistance. However, it has been reported that the measured soil resistance in different soil layers depends not only on the degree of soil compactness but also on soil failure mode induced by the shank of the sensor. It was hypothesized that the differences in sound signals collected by microphones during penetration tests could be used to differentiate the failure modes. In this research, an acoustic multiple-tip horizontal penetrometer was developed, with three 30° prismatic tips attached horizontally to S-shape load cells and worked at depths of 10, 20 and 30 cm. The tips working at 10 and 30 cm depths were also fitted with microphones. The sensor was tested in a field with a clay loam soil. The sound signal was first de-noised using wavelet method, and then frequency spectrum and power spectral density of the signals were obtained by fast Fourier transform and Welsh's method, respectively. When the prismatic tips were operated below the critical depth of the sensor (tips at depths of 20 and 30 cm), there was a significant relationship between horizontal resistance index (HRI) and the cone index measured by a vertically-operated cone penetrometer; whereas for the shallower depth (10 cm) the relationship was not significant. The power of the sound recorded of the tip passing through the disturbed soil above the critical depth (10 cm) was much lower than when the tip was penetrating the undisturbed soil located below the critical depth (30 cm). The increase in power of the acoustic signal with depth was in line with the increase in the measured HRI. It can be concluded that the developed combined acoustic penetrometer can both detect soil failure mode and measure soil horizontal resistance.
Yurui Sun - One of the best experts on this subject based on the ideXlab platform.
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Shaft Friction of an ASABE Standard Soil Cone Penetrometer
Transactions of the ASABE, 2013Co-Authors: Xiang Cai, Yurui Sun, Peter Schulze-lammers, Wolfgang Buescher, Christian Maack, Fanjia Meng, J. Lin, Qiang Cheng, Huili ZhangAbstract:Abstract. To ensure penetration results that are comparable under various experimental conditions, cone Penetrometers specified by ASABE Standards have been suggested for many years. Elastic-plastic properties are typical of most agricultural materials, so the material being penetrated by a cone penetrometer may contact the penetrometer shaft, and friction on the shaft may affect the penetration force data. Development of a method for quantifying this friction force is expected to improve the accuracy of cone penetrometer data. The objectives of this study were: (1) to evaluate a method for determining friction force on the shaft of a cone penetrometer while penetrating sand and clay soils packed in a specific cylinder, (2) to verify the penetration friction component (PFC) that may significantly influence penetration resistance (PR) measurements for various densities of chopped maize, and (3) to assess the effectiveness of a proposed filter method for adjusting friction on the penetrometer shaft. With these intentions, we embedded strain gauges into an ASABE Standard small cone. The tip was free from the shaft friction, so the output of this sensor was used as a reference in this study. We found the ASABE Standard small cone suitable for a broad range of soil textures, as little PFC was observed from the sand or the clay soil samples. However, considerable friction from penetrating chopped maize was observed at three levels of packed density using the cylinder method. In this situation, with the reference of the sensor output inside the tip, a pair of coefficients (C 1 = 2329, C 2 = 2120) were optimized to filter the PFC out of the PR measurement. The adjusted data agreed well with those of the reference sensor (R 2 = 0.968; RMSE = 6.521 N). Thus, ASABE Standard Penetrometers can also be used for silage materials without mechanical modification.
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Energy-based comparison between a dynamic cone penetrometer and a motor-operated static cone penetrometer
Soil & Tillage Research, 2011Co-Authors: Yurui Sun, J. Lin, Qiang Cheng, P. Schulze Lammers, Aaron A. Berg, F. Meng, Q. ZengAbstract:Dynamic cone Penetrometers (DCP) have been available for many years. However, there is still an uncertainty between the simplified Dutch Formula and the complete one. As a continual approach to assess both formulae, this study provides an energy-based comparison between a DCP and a motor-operated static cone penetrometer (SCP). The results yielded by SCP were regarded as reference. Through the designed experiment, we observed that both formulae considerably extenuated the energy loss arisen from strikes, which was equivalent to an overestimation of the calculated penetration force. Since the overestimation is greater than the uncertainty between both formulae, a better analytical model is required. Regarding the energy loss, the shaft vibration should also be taken into account for correcting each formula.
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evaluation of a combined penetrometer for simultaneous measurement of penetration resistance and soil water content
Journal of Plant Nutrition and Soil Science, 2004Co-Authors: Yurui Sun, Peter Schulze LammersAbstract:A combined penetrometer is an appropriate tool to measure the soil cone resistance and the water-content profile. As a relatively new technique, a combined capacitance-penetrometer for the simultaneous measurement of cone index and soil water content was developed at the Department of Agricultural Engineering of Bonn University in 2002. The objective of this study was the evaluation of the effectiveness and applicability of the innovated penetrometer with a focus on three aspects: (1) A capacitance sensor with two electrode configurations was calibrated for silt loam, sandy loam, and sand. The calibration results show that both electrode configurations have sufficient water-content sensitivity, but soil-specific calibrations seem necessary. (2) Under laboratory conditions, the dynamic resolution and response of the capacitance-penetrometer were validated, and its radius of influence was determined. (3) The field measurement results demonstrate that this measurement technique can be used to improve the interpretation quality of soil cone index data. Bewertung eines Penetrometers zur gleichzeitigen Bestimmung von Eindringwiderstand und Bodenfeuchte Fur die Ermittlung von Bodenprofilen fur den Eindringwiderstand und die Bodenfeuchte erscheint die Kombination aus Penetrometer und Bodenfeuchtesensor als geeignete Losung. Ein solcher Kombinationssensor wurde im Jahr 2002 am Institut fur Landtechnik der Universitat Bonn fur die simultane Messung des Eindringwiderstandes und der Bodenfeuchte entwickelt. In diesem Beitrag wird die Tauglichkeit und Anwendbarkeit fur Feldmessungen in folgenden Schritten dargestellt: (1) Ein kapazitiver Sensor mit zwei Elektrodenkonfigurationen wurde fur die drei Bodenarten schluffiger Lehm, sandiger Lehm und Sand kalibiriert. Die Kalibrationsgleichungen zeigen, dass beide Elektrodenanordnungen uber ausreichende Empfindlichkeit zur Bodenfeuchtemessung verfugen. Es sind aber bodenartspezifische Kalibrierungen notwendig. (2) Die dynamische Auflosung und das Ansprechverhalten des Feuchtesensors wurden fur beide Elektrodenanordnungen untersucht, und die Ausbreitung des dielektrischen Feldes wurde bestimmt. (3) Die Ergebnisse der Messungen im gewachsenen Boden zeigen, dass die Messmethode zur Verbesserung der Interpretation der Konus-Indexwerte herangezogen werden kann.