In Brazil and various regions globally, the initiation of landslides is frequently associated with rainfall;yet the spatial arrangement of geological structures and stratification considerably influences landslide occ...In Brazil and various regions globally, the initiation of landslides is frequently associated with rainfall;yet the spatial arrangement of geological structures and stratification considerably influences landslide occurrences. The multifaceted nature of these influences makes the surveillance of mass movements a highly intricate task, requiring an understanding of numerous interdependent variables. Recent years have seen an emergence in scholarly research aimed at integrating geophysical and geotechnical methodologies. The conjoint examination of geophysical and geotechnical data offers an enhanced perspective into subsurface structures. Within this work, a methodology is proposed for the synchronous analysis of electrical resistivity geophysical data and geotechnical data, specifically those extracted from the Light Dynamic Penetrometer (DPL) and Standard Penetration Test (SPT). This study involved a linear fitting process to correlate resistivity with N10/SPT N-values from DPL/SPT soundings, culminating in a 2D profile of N10/SPT N-values predicated on electrical profiles. The findings of this research furnish invaluable insights into slope stability by allowing for a two-dimensional representation of penetration resistance properties. Through the synthesis of geophysical and geotechnical data, this project aims to augment the comprehension of subsurface conditions, with potential implications for refining landslide risk evaluations. This endeavor offers insight into the formulation of more effective and precise slope management protocols and disaster prevention strategies.展开更多
Rolling dynamic compaction (RDC),which employs non-circular module towed behind a tractor,is an innovative soil compaction method that has proven to be successful in many ground improvement applications.RDC involves r...Rolling dynamic compaction (RDC),which employs non-circular module towed behind a tractor,is an innovative soil compaction method that has proven to be successful in many ground improvement applications.RDC involves repeatedly delivering high-energy impact blows onto the ground surface,which improves soil density and thus soil strength and stiffness.However,there exists a lack of methods to predict the effectiveness of RDC in different ground conditions,which has become a major obstacle to its adoption.For this,in this context,a prediction model is developed based on linear genetic programming (LGP),which is one of the common approaches in application of artificial intelligence for nonlinear forecasting.The model is based on in situ density-related data in terms of dynamic cone penetrometer (DCP) results obtained from several projects that have employed the 4-sided,8-t impact roller (BH-1300).It is shown that the model is accurate and reliable over a range of soil types.Furthermore,a series of parametric studies confirms its robustness in generalizing data.In addition,the results of the comparative study indicate that the optimal LGP model has a better predictive performance than the existing artificial neural network (ANN) model developed earlier by the authors.展开更多
Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resil...Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resilient modulus values at only a specific stress state from DCP data, corresponding to the predefined thicknesses of pavement layers（a 50 mm asphalt wearing course, a 100 mm asphalt binder course and a200 mm aggregate base course）. In this study, field-measured DCP data were utilized to estimate the resilient modulus of low-plasticity subgrade Piedmont residual soil. Piedmont residual soils are in-place weathered soils from igneous and metamorphic rocks, as opposed to transported or compacted soils.Hence the existing empirical correlations might not be applicable for these soils. An experimental program was conducted incorporating field DCP and laboratory resilient modulus tests on "undisturbed" soil specimens. The DCP tests were carried out at various locations in four test sections to evaluate subgrade stiffness variation laterally and with depth. Laboratory resilient modulus test results were analyzed in the context of the mechanistic-empirical pavement design guide（MEPDG） recommended universal constitutive model. A new approach for predicting the resilient modulus from DCP by estimating MEPDG constitutive model coefficients（k;,k;and k;） was developed through statistical analyses. The new model is capable of not only taking into account the in situ soil condition on the basis of field measurements,but also representing the resilient modulus at any stress state which addresses a limitation with existing empirical DCP models and its applicability for a specific case. Validation of the model is demonstrated by using data that were not used for model development, as well as data reported in the literature.展开更多
Particle crushing occurs near the tip of a penetrometer and influences the development of the tip resistance.To study particle crushing near a penetrometer tip,a cone penetrometer was monotonically jacked and then loa...Particle crushing occurs near the tip of a penetrometer and influences the development of the tip resistance.To study particle crushing near a penetrometer tip,a cone penetrometer was monotonically jacked and then load-tested in medium dense and dense silica sand samples prepared in a halfcylindrical calibration chamber with viewing windows.During the tests,images of the advancing penetrometer and the surrounding soil were taken using digital cameras and analyzed to obtain the displacement and strain fields around the penetrometer using the Digital Image Correlation(DIC)technique.Subsequently,soil samples were collected near the tip of the penetrometer using a novel agarimpregnation technique and digitized using an X-ray microscope.The digitized samples were analyzed to reconstruct the three-dimensional models of individual particles,generating the gradation and relative breakage parameters of the sand around the cone penetrometer.展开更多
In order to minimise the cost of constructing low volume roads (LVRs), it is essential that optimum use is made of locally available, naturally occurring materials. However, conflicts often arise between material acce...In order to minimise the cost of constructing low volume roads (LVRs), it is essential that optimum use is made of locally available, naturally occurring materials. However, conflicts often arise between material acceptability, as defined by conventional test methods and specifications, and material suitability in terms of actual engineering performance as a “fit-for-purpose” road construction material. To avoid such conflicts, it is crucial to adopt appropriate test methods and specifications for selecting construction materials. This paper presents a materials evaluation framework for optimizing the utilisation of materials in LVR pavements based on the use of the Dynamic Cone Penetrometer (DCP). This approach enables materials to be selected on the basis of their “fitness-for-purpose”. It avoids suitable materials from being rejected based on one or other of the traditionally specified parameters not being complied with, even though their strength, as measured by the DCP penetration rate (DN value in mm/blow) of the soil, may be adequate. Investigations of the properties of a wide range of locally available materials that have been used successfully in the construction of LVRs have confirmed the validity of the materials evaluation framework.展开更多
Dynamic cone penetrometer is mainly used as an in situ device and laboratory application, in a mould, has rarely been reported due to the confining effect. In this study, a dynamic lightweight cone penetrometer that c...Dynamic cone penetrometer is mainly used as an in situ device and laboratory application, in a mould, has rarely been reported due to the confining effect. In this study, a dynamic lightweight cone penetrometer that can be used in a CBR （California bearing ratio） mould in the laboratory as well as in the field, with similar results, was developed. The results show that the influence of the mould confinement can be eliminated when the hammer mass is 2.25 kg. A strong correlation was found between CBR values and the new dynamic lightweight penetrometer index, for six fine-grained soil samples, with different moisture contents, used in this study.展开更多
Portable in-situ devices have been used for characterizing low accessible field,such as the railway subgrade.In this study,the automated cone penetrometer(ACP)was designed for the application on the railway subgrade.A...Portable in-situ devices have been used for characterizing low accessible field,such as the railway subgrade.In this study,the automated cone penetrometer(ACP)was designed for the application on the railway subgrade.ACP is composed of the cone tip,driving rod,and hydraulic hammer system.The hydraulic motor lifts and drops the 294.3 N hammer from a height of 200 mm such that the potential energy of 58.9 N m impacts the driving rod.The N-value(NACP)from the ACP test was compared with the dynamic cone penetration index(DCPI)from the dynamic cone penetrometer(DCP)test.The test results show that the NACP and DCPI profiles show opposite trend owing to the inverse concept of the unit.From the correlation of DCPI and NACP,the limitation of DCPI reveals owing the minimum manually measured value of 1 mm/blow.Additionally,the evaluation of the deflection modulus(EFWD)using NACP is more efficient than that using DCPI.Based on the result of this study,we suggest that ACP can be used for strength and stiffness evaluation of railway subgrade rapidly and reliably.展开更多
Small bodies in the solar system are known to be covered by a layer of loose unconsolidated soil composed of grains ranging from dusty sands to rugged boulders.Various geophysical processes have modified these regolit...Small bodies in the solar system are known to be covered by a layer of loose unconsolidated soil composed of grains ranging from dusty sands to rugged boulders.Various geophysical processes have modified these regolith layers since their origin.Therefore,the landforms on regolith-blanketed surfaces hold vital clues for reconstructing the geological processes occurring on small bodies.However,the mechanical strength of small body regolith remains unclear,which is an important parameter for understanding its dynamic evolution.Furthermore,regolith mechanical properties are key factors for the design and operation of space missions that interact with small body surfaces.The granular penetrometer,which is an instrument that facilitates in situ mechanical characterization of surface/subsurface materials,has attracted significant attention.However,we still do not fully understand the penetration dynamics related to granular regolith,partially because of the experimental difficulties in measuring grain-scale responses under microgravity,particularly on the longer timescales of small body dynamics.In this study,we analyzed the slow intrusion ofa locomotor into granular matter through large-scale numerical simulations based on a soft sphere discrete element model.We demonstrated that the resistance force of cohesionlessregolith increases abruptly with penetration depth after contact and then transitions to a linear regime.The scale factor of the steady-state component is roughly proportionalto the internal friction of the granular materials,which allows us to deduce the shearstrength of planetary soils by measuring their force depth relationships.When cohesion is included,due to the brittle behavior of cohesive materials,the resistance profile is characterized by a stationary state at a large penetration depth.The saturation resistance,which represents the failure threshold of granular materials,increases with the cohesion strength of the regolith.This positive correlation provides a reliable tool for measuring the tensile strength of granular regolith in small body touchdown missions.展开更多
文摘In Brazil and various regions globally, the initiation of landslides is frequently associated with rainfall;yet the spatial arrangement of geological structures and stratification considerably influences landslide occurrences. The multifaceted nature of these influences makes the surveillance of mass movements a highly intricate task, requiring an understanding of numerous interdependent variables. Recent years have seen an emergence in scholarly research aimed at integrating geophysical and geotechnical methodologies. The conjoint examination of geophysical and geotechnical data offers an enhanced perspective into subsurface structures. Within this work, a methodology is proposed for the synchronous analysis of electrical resistivity geophysical data and geotechnical data, specifically those extracted from the Light Dynamic Penetrometer (DPL) and Standard Penetration Test (SPT). This study involved a linear fitting process to correlate resistivity with N10/SPT N-values from DPL/SPT soundings, culminating in a 2D profile of N10/SPT N-values predicated on electrical profiles. The findings of this research furnish invaluable insights into slope stability by allowing for a two-dimensional representation of penetration resistance properties. Through the synthesis of geophysical and geotechnical data, this project aims to augment the comprehension of subsurface conditions, with potential implications for refining landslide risk evaluations. This endeavor offers insight into the formulation of more effective and precise slope management protocols and disaster prevention strategies.
基金supported under Australian Research Council’s Discovery Projects funding scheme(project No. DP120101761)
文摘Rolling dynamic compaction (RDC),which employs non-circular module towed behind a tractor,is an innovative soil compaction method that has proven to be successful in many ground improvement applications.RDC involves repeatedly delivering high-energy impact blows onto the ground surface,which improves soil density and thus soil strength and stiffness.However,there exists a lack of methods to predict the effectiveness of RDC in different ground conditions,which has become a major obstacle to its adoption.For this,in this context,a prediction model is developed based on linear genetic programming (LGP),which is one of the common approaches in application of artificial intelligence for nonlinear forecasting.The model is based on in situ density-related data in terms of dynamic cone penetrometer (DCP) results obtained from several projects that have employed the 4-sided,8-t impact roller (BH-1300).It is shown that the model is accurate and reliable over a range of soil types.Furthermore,a series of parametric studies confirms its robustness in generalizing data.In addition,the results of the comparative study indicate that the optimal LGP model has a better predictive performance than the existing artificial neural network (ANN) model developed earlier by the authors.
文摘Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resilient modulus values at only a specific stress state from DCP data, corresponding to the predefined thicknesses of pavement layers（a 50 mm asphalt wearing course, a 100 mm asphalt binder course and a200 mm aggregate base course）. In this study, field-measured DCP data were utilized to estimate the resilient modulus of low-plasticity subgrade Piedmont residual soil. Piedmont residual soils are in-place weathered soils from igneous and metamorphic rocks, as opposed to transported or compacted soils.Hence the existing empirical correlations might not be applicable for these soils. An experimental program was conducted incorporating field DCP and laboratory resilient modulus tests on "undisturbed" soil specimens. The DCP tests were carried out at various locations in four test sections to evaluate subgrade stiffness variation laterally and with depth. Laboratory resilient modulus test results were analyzed in the context of the mechanistic-empirical pavement design guide（MEPDG） recommended universal constitutive model. A new approach for predicting the resilient modulus from DCP by estimating MEPDG constitutive model coefficients（k;,k;and k;） was developed through statistical analyses. The new model is capable of not only taking into account the in situ soil condition on the basis of field measurements,but also representing the resilient modulus at any stress state which addresses a limitation with existing empirical DCP models and its applicability for a specific case. Validation of the model is demonstrated by using data that were not used for model development, as well as data reported in the literature.
基金funded by the National Science Foundation under Grant No. 1562538The support of NSF is gratefully acknowledged
文摘Particle crushing occurs near the tip of a penetrometer and influences the development of the tip resistance.To study particle crushing near a penetrometer tip,a cone penetrometer was monotonically jacked and then load-tested in medium dense and dense silica sand samples prepared in a halfcylindrical calibration chamber with viewing windows.During the tests,images of the advancing penetrometer and the surrounding soil were taken using digital cameras and analyzed to obtain the displacement and strain fields around the penetrometer using the Digital Image Correlation(DIC)technique.Subsequently,soil samples were collected near the tip of the penetrometer using a novel agarimpregnation technique and digitized using an X-ray microscope.The digitized samples were analyzed to reconstruct the three-dimensional models of individual particles,generating the gradation and relative breakage parameters of the sand around the cone penetrometer.
文摘In order to minimise the cost of constructing low volume roads (LVRs), it is essential that optimum use is made of locally available, naturally occurring materials. However, conflicts often arise between material acceptability, as defined by conventional test methods and specifications, and material suitability in terms of actual engineering performance as a “fit-for-purpose” road construction material. To avoid such conflicts, it is crucial to adopt appropriate test methods and specifications for selecting construction materials. This paper presents a materials evaluation framework for optimizing the utilisation of materials in LVR pavements based on the use of the Dynamic Cone Penetrometer (DCP). This approach enables materials to be selected on the basis of their “fitness-for-purpose”. It avoids suitable materials from being rejected based on one or other of the traditionally specified parameters not being complied with, even though their strength, as measured by the DCP penetration rate (DN value in mm/blow) of the soil, may be adequate. Investigations of the properties of a wide range of locally available materials that have been used successfully in the construction of LVRs have confirmed the validity of the materials evaluation framework.
文摘Dynamic cone penetrometer is mainly used as an in situ device and laboratory application, in a mould, has rarely been reported due to the confining effect. In this study, a dynamic lightweight cone penetrometer that can be used in a CBR （California bearing ratio） mould in the laboratory as well as in the field, with similar results, was developed. The results show that the influence of the mould confinement can be eliminated when the hammer mass is 2.25 kg. A strong correlation was found between CBR values and the new dynamic lightweight penetrometer index, for six fine-grained soil samples, with different moisture contents, used in this study.
基金This work was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.NRF-2021R1A5A1032433,NRF-2020R1A2B5B03001470).
文摘Portable in-situ devices have been used for characterizing low accessible field,such as the railway subgrade.In this study,the automated cone penetrometer(ACP)was designed for the application on the railway subgrade.ACP is composed of the cone tip,driving rod,and hydraulic hammer system.The hydraulic motor lifts and drops the 294.3 N hammer from a height of 200 mm such that the potential energy of 58.9 N m impacts the driving rod.The N-value(NACP)from the ACP test was compared with the dynamic cone penetration index(DCPI)from the dynamic cone penetrometer(DCP)test.The test results show that the NACP and DCPI profiles show opposite trend owing to the inverse concept of the unit.From the correlation of DCPI and NACP,the limitation of DCPI reveals owing the minimum manually measured value of 1 mm/blow.Additionally,the evaluation of the deflection modulus(EFWD)using NACP is more efficient than that using DCPI.Based on the result of this study,we suggest that ACP can be used for strength and stiffness evaluation of railway subgrade rapidly and reliably.
基金supported by the National Key R&D Program of China(2019YFA0706500)。
文摘Small bodies in the solar system are known to be covered by a layer of loose unconsolidated soil composed of grains ranging from dusty sands to rugged boulders.Various geophysical processes have modified these regolith layers since their origin.Therefore,the landforms on regolith-blanketed surfaces hold vital clues for reconstructing the geological processes occurring on small bodies.However,the mechanical strength of small body regolith remains unclear,which is an important parameter for understanding its dynamic evolution.Furthermore,regolith mechanical properties are key factors for the design and operation of space missions that interact with small body surfaces.The granular penetrometer,which is an instrument that facilitates in situ mechanical characterization of surface/subsurface materials,has attracted significant attention.However,we still do not fully understand the penetration dynamics related to granular regolith,partially because of the experimental difficulties in measuring grain-scale responses under microgravity,particularly on the longer timescales of small body dynamics.In this study,we analyzed the slow intrusion ofa locomotor into granular matter through large-scale numerical simulations based on a soft sphere discrete element model.We demonstrated that the resistance force of cohesionlessregolith increases abruptly with penetration depth after contact and then transitions to a linear regime.The scale factor of the steady-state component is roughly proportionalto the internal friction of the granular materials,which allows us to deduce the shearstrength of planetary soils by measuring their force depth relationships.When cohesion is included,due to the brittle behavior of cohesive materials,the resistance profile is characterized by a stationary state at a large penetration depth.The saturation resistance,which represents the failure threshold of granular materials,increases with the cohesion strength of the regolith.This positive correlation provides a reliable tool for measuring the tensile strength of granular regolith in small body touchdown missions.
