Kazuhiro Hayashi, Shuhei Takahashi, Tomoki Nakamura, S. Tamura
This study aimed to clarify the highly nonlinear behavior of soil–pile system and proposes small-scale reinforced concrete (RC) pile model for use in centrifugal tests. Horizontal static loading centrifugal tests were conducted on 13 small-scale RC pile models at 50-G centrifuge acceleration to illustrate the reproducibility of a full-scale RC pile. The experimental results show that the maximum flexural strength of a small-scale RC pile can be estimated accurately as a function of the full plastic moment Mu. The current design formula for the maximum shear strength Qs in the Architectural Institute of Japan (AIJ) standard is applied to full-scale RC members, while the final fracture mode of the proposed small-scale model corresponds to its estimation. Horizontal static loading centrifugal tests were performed on a soil–pile system consisting of dry sand and a small-scale RC pile model. Furthermore, the experimental results for the soil–pile system correspond well to the ultimate strength based for flexural fracture proposed by Broms (1964) and those for shear fracture according to the AIJ Standard (2010). The experimental results obtained in this study for the proposed small-scale RC pile model are valid for use in assessing a soil–pile system's maximum strength and final fracture mode.
本研究旨在阐明土-桩体系的高度非线性特性，并提出用于离心试验的小尺度钢筋混凝土桩模型。在50-G离心加速度下，对13个小尺寸RC桩模型进行了水平静载离心试验，以说明原尺寸RC桩的可重复性。试验结果表明，小尺度钢筋混凝土桩的最大抗弯强度可以准确地估计为全塑性弯矩Mu的函数。现行日本建筑学会(Architectural Institute of Japan, AIJ)标准中最大抗剪强度Qs的设计公式适用于全尺寸RC构件，而所提出的小尺寸模型的最终断裂模式与其估算值相对应。在由干砂和小尺度钢筋混凝土桩模型组成的土-桩体系上进行了水平静荷载离心试验。此外，土桩体系的试验结果与Broms(1964)提出的基于弯曲断裂的极限强度和AIJ标准(2010)提出的基于剪切断裂的极限强度相吻合。本文提出的小尺度钢筋混凝土桩模型的试验结果可用于评估土桩体系的最大强度和最终断裂模式。
{"title":"Centrifuge testing of nonlinear soil–pile response using 1:50 scale reinforced concrete pile models","authors":"Kazuhiro Hayashi, Shuhei Takahashi, Tomoki Nakamura, S. Tamura","doi":"10.1680/jphmg.22.00049","DOIUrl":"https://doi.org/10.1680/jphmg.22.00049","url":null,"abstract":"This study aimed to clarify the highly nonlinear behavior of soil–pile system and proposes small-scale reinforced concrete (RC) pile model for use in centrifugal tests. Horizontal static loading centrifugal tests were conducted on 13 small-scale RC pile models at 50-G centrifuge acceleration to illustrate the reproducibility of a full-scale RC pile. The experimental results show that the maximum flexural strength of a small-scale RC pile can be estimated accurately as a function of the full plastic moment Mu. The current design formula for the maximum shear strength Qs in the Architectural Institute of Japan (AIJ) standard is applied to full-scale RC members, while the final fracture mode of the proposed small-scale model corresponds to its estimation. Horizontal static loading centrifugal tests were performed on a soil–pile system consisting of dry sand and a small-scale RC pile model. Furthermore, the experimental results for the soil–pile system correspond well to the ultimate strength based for flexural fracture proposed by Broms (1964) and those for shear fracture according to the AIJ Standard (2010). The experimental results obtained in this study for the proposed small-scale RC pile model are valid for use in assessing a soil–pile system's maximum strength and final fracture mode.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-02-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45294574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-01-01DOI: 10.1680/jphmg.2023.23.1.1
Xianfeng Ma
{"title":"Editorial","authors":"Xianfeng Ma","doi":"10.1680/jphmg.2023.23.1.1","DOIUrl":"https://doi.org/10.1680/jphmg.2023.23.1.1","url":null,"abstract":"","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45997370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tianqiang Jia, S. Stanier, P. Watson, Xiaowei Feng, S. Gourvenec
Tolerably mobile subsea foundations may be used to replace conventional fixed mudmat foundations for pipeline infrastructure and are designed to slide on the seabed along with the connected pipeline, in order to accommodate thermally induced horizontal forces. This allows the size of the foundation and the resulting fabrication and installation costs to be substantially reduced. The performance of mobile foundations is explored in this paper through four centrifuge model tests on a NC or LOC reconstituted calcareous silt obtained from the Northwest Shelf of Western Australia. The results are compared to three existing tests performed on a kaolin clay. The results show that under typical periodic surface sliding and intervening rests, sliding resistance evolves within a cycle with resistance peaks evident at either end of the sliding footprint due to the formation of berms, and the residual resistance increasing with sliding cycles towards a drained state. Shear and consolidation induced settlements accumulate with sliding cycles although at a reducing rate. The tests in the calcareous silt show higher normalised initial peak sliding resistance, a more dramatic loss and slower recovery of sliding resistance with cycles, and slower rate of decrease of incremental settlement compared with the response in kaolin clay.
{"title":"Centrifuge testing of a tolerably mobile subsea foundation: exploring the effect of soil type on the evolution of whole-life resistance and settlement","authors":"Tianqiang Jia, S. Stanier, P. Watson, Xiaowei Feng, S. Gourvenec","doi":"10.1680/jphmg.22.00017","DOIUrl":"https://doi.org/10.1680/jphmg.22.00017","url":null,"abstract":"Tolerably mobile subsea foundations may be used to replace conventional fixed mudmat foundations for pipeline infrastructure and are designed to slide on the seabed along with the connected pipeline, in order to accommodate thermally induced horizontal forces. This allows the size of the foundation and the resulting fabrication and installation costs to be substantially reduced. The performance of mobile foundations is explored in this paper through four centrifuge model tests on a NC or LOC reconstituted calcareous silt obtained from the Northwest Shelf of Western Australia. The results are compared to three existing tests performed on a kaolin clay. The results show that under typical periodic surface sliding and intervening rests, sliding resistance evolves within a cycle with resistance peaks evident at either end of the sliding footprint due to the formation of berms, and the residual resistance increasing with sliding cycles towards a drained state. Shear and consolidation induced settlements accumulate with sliding cycles although at a reducing rate. The tests in the calcareous silt show higher normalised initial peak sliding resistance, a more dramatic loss and slower recovery of sliding resistance with cycles, and slower rate of decrease of incremental settlement compared with the response in kaolin clay.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44931951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. S. Domingos, C. Pinto, F. Danziger, Arthur V. S. Pinheiro, T. Lunne
Large flexible calibration chambers (CC) to evaluate and develop interpretation methods for cone penetration tests (CPT) in cohesionless soils have been used since the late 1960s. Nevertheless, only average boundary stress values are known in almost all tests already performed. Tactile Pressure Sensors represent a useful tool to assess the stress distribution in an area under loading and have been applied in some geotechnical studies. The present study presents the results of CPTs carried out on a large flexible CC in a very loose and a medium dense fine quartz sand. Tactile pressure sensors were placed on the walls of the CC, allowing the measurement of horizontal stresses and their spatial distribution in all test phases: sample formation, lateral and cavity cell filling, piston filling, sample stressing, and CPT. In particular, the Tactile Pressure Sensors were able to measure the horizontal stresses before the cavity and lateral cell filling, i.e. when no information is available about the horizontal stresses in regular tests. The measurements contribute to the discussion on the influence of the CC boundaries on the test results. The results encourage the use of tactile pressure sensors in a more routinely base in large flexible CC testing.
{"title":"The use of tactile pressure sensors for horizontal stress measurements on a large flexible Calibration Chamber","authors":"G. S. Domingos, C. Pinto, F. Danziger, Arthur V. S. Pinheiro, T. Lunne","doi":"10.1680/jphmg.21.00084","DOIUrl":"https://doi.org/10.1680/jphmg.21.00084","url":null,"abstract":"Large flexible calibration chambers (CC) to evaluate and develop interpretation methods for cone penetration tests (CPT) in cohesionless soils have been used since the late 1960s. Nevertheless, only average boundary stress values are known in almost all tests already performed. Tactile Pressure Sensors represent a useful tool to assess the stress distribution in an area under loading and have been applied in some geotechnical studies. The present study presents the results of CPTs carried out on a large flexible CC in a very loose and a medium dense fine quartz sand. Tactile pressure sensors were placed on the walls of the CC, allowing the measurement of horizontal stresses and their spatial distribution in all test phases: sample formation, lateral and cavity cell filling, piston filling, sample stressing, and CPT. In particular, the Tactile Pressure Sensors were able to measure the horizontal stresses before the cavity and lateral cell filling, i.e. when no information is available about the horizontal stresses in regular tests. The measurements contribute to the discussion on the influence of the CC boundaries on the test results. The results encourage the use of tactile pressure sensors in a more routinely base in large flexible CC testing.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48254180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
L. Sakellariadis, E. Bleiker, M. Iten, H. Buschor, A. Kieper, R. Herzog, A. Marin, O. Adamidis, I. Anastasopoulos
Motivated by the need to develop rational design methods for the retrofit of existing bridges on pile groups, the paper introduces recent experimental developments at the ETHZ Drum centrifuge. Four setups are developed for vertical, pushover, combined, and vibration testing. Their capabilities and limitations are demonstrated using as example a 2x1 pile group on dense saturated sand. Single piles are subjected to vertical loading, exploring the role of installation effects and interface roughness. Pushover loading is employed to measure the moment capacity (Mult) of a lightly- and a heavily-loaded group. In contrast to intuitive expectations, the heavily-loaded system mobilises larger Mult. The developed combined loading apparatus is proof-tested for a shallow foundation. Combined loading under constant vertical load is conducted to derive failure envelopes, revealing significant coupling between lateral and moment loading, and confirming the expansion of the failure envelope with increasing static vertical load. The vibration testing setup is proof-tested, confirming the possibility to identify the natural frequency of the system and the small-strain stiffness of the foundation through non-destructive testing. Although the study is fuelled by our ongoing work on pile groups, the developed experimental setups are of general applicability for the study of deep and shallow foundation systems.
{"title":"Testing Pile Foundations at the ΕΤΗ Zurich Drum Centrifuge: Recent Developments","authors":"L. Sakellariadis, E. Bleiker, M. Iten, H. Buschor, A. Kieper, R. Herzog, A. Marin, O. Adamidis, I. Anastasopoulos","doi":"10.1680/jphmg.21.00067","DOIUrl":"https://doi.org/10.1680/jphmg.21.00067","url":null,"abstract":"Motivated by the need to develop rational design methods for the retrofit of existing bridges on pile groups, the paper introduces recent experimental developments at the ETHZ Drum centrifuge. Four setups are developed for vertical, pushover, combined, and vibration testing. Their capabilities and limitations are demonstrated using as example a 2x1 pile group on dense saturated sand. Single piles are subjected to vertical loading, exploring the role of installation effects and interface roughness. Pushover loading is employed to measure the moment capacity (Mult) of a lightly- and a heavily-loaded group. In contrast to intuitive expectations, the heavily-loaded system mobilises larger Mult. The developed combined loading apparatus is proof-tested for a shallow foundation. Combined loading under constant vertical load is conducted to derive failure envelopes, revealing significant coupling between lateral and moment loading, and confirming the expansion of the failure envelope with increasing static vertical load. The vibration testing setup is proof-tested, confirming the possibility to identify the natural frequency of the system and the small-strain stiffness of the foundation through non-destructive testing. Although the study is fuelled by our ongoing work on pile groups, the developed experimental setups are of general applicability for the study of deep and shallow foundation systems.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45604501","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shafts are frequently constructed to allow access to subsurface infrastructure and the resulting excavation generally deep and narrow. Shafts may be constructed using a variety of methods and plan forms dependent on ground conditions and intended use. An axisymmetric (cylindrical) geometry is often preferred due to the relatively simple structural analysis, construction method and for a number of approaches that are available to estimate the ground movements around such an excavation. In certain cases, particularly when there is restricted space both above and below surface, non-circular shafts could be a preferred solution. The assessment of surface movements around non-circular shafts is difficult as little information exists and there are few empirical prediction methods available. In this study, a series of centrifuge tests have been conducted to investigate the effects of modifying the cross-sectional profile of a shaft (i.e. circular in plan compared with elliptical). Analysis of measurements obtained from centrifuge tests undertaken at City, University of London's geotechnical centrifuge facility are presented and compared with existing predictive methods. An addendum to the empirical equations and procedures for predicting surface settlements arising from circular shafts is presented to allow for the assessment of movements around elliptical shafts in clay.
{"title":"Surface settlements arising from elliptical shaft excavation in clay","authors":"R. Goodey, S. Divall, B. Le","doi":"10.1680/jphmg.21.00080","DOIUrl":"https://doi.org/10.1680/jphmg.21.00080","url":null,"abstract":"Shafts are frequently constructed to allow access to subsurface infrastructure and the resulting excavation generally deep and narrow. Shafts may be constructed using a variety of methods and plan forms dependent on ground conditions and intended use. An axisymmetric (cylindrical) geometry is often preferred due to the relatively simple structural analysis, construction method and for a number of approaches that are available to estimate the ground movements around such an excavation. In certain cases, particularly when there is restricted space both above and below surface, non-circular shafts could be a preferred solution. The assessment of surface movements around non-circular shafts is difficult as little information exists and there are few empirical prediction methods available. In this study, a series of centrifuge tests have been conducted to investigate the effects of modifying the cross-sectional profile of a shaft (i.e. circular in plan compared with elliptical). Analysis of measurements obtained from centrifuge tests undertaken at City, University of London's geotechnical centrifuge facility are presented and compared with existing predictive methods. An addendum to the empirical equations and procedures for predicting surface settlements arising from circular shafts is presented to allow for the assessment of movements around elliptical shafts in clay.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-10-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44182457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper has studied the failure mechanism of geocell reinforced vertical anchors in sand through a series of tests and numerical analyses. It is observed that the anchor load carrying capacity significantly increases with the application of geocell reinforcement, which is primary associated with the rupture behaviour of reinforced anchor beds. The rupture surfaces are found to have originated from bottom edge of the geocell mattress and propagated to the soil surface in a curvilinear shape. The size of rupture surface tends to increase with increase in length, width and height of geocell mattress leading to increased load carrying capacity of the system. However, beyond certain length, width, and height of geocell mattress, further increase in size of the rupture surfaces was marginal. Geocells of relatively smaller pocket size (i.e., close to anchor size) can effectively confine the soil leading to a coherent structure that inhibits potential rupture close to the anchors. But with geocells of wider pocket openings enable the formation of rupture within the geocell mattress. Hence, it is concluded that the load carrying capacity of reinforced anchors which is dependent on the size of the rupture surface is influenced by the geometry of the geocell mattress.
{"title":"Failure Mechanism of Geocell Reinforced Vertical Plate Anchor Subjected to Lateral Loading","authors":"A. K. Choudhary, S. Dash","doi":"10.1680/jphmg.21.00009","DOIUrl":"https://doi.org/10.1680/jphmg.21.00009","url":null,"abstract":"This paper has studied the failure mechanism of geocell reinforced vertical anchors in sand through a series of tests and numerical analyses. It is observed that the anchor load carrying capacity significantly increases with the application of geocell reinforcement, which is primary associated with the rupture behaviour of reinforced anchor beds. The rupture surfaces are found to have originated from bottom edge of the geocell mattress and propagated to the soil surface in a curvilinear shape. The size of rupture surface tends to increase with increase in length, width and height of geocell mattress leading to increased load carrying capacity of the system. However, beyond certain length, width, and height of geocell mattress, further increase in size of the rupture surfaces was marginal. Geocells of relatively smaller pocket size (i.e., close to anchor size) can effectively confine the soil leading to a coherent structure that inhibits potential rupture close to the anchors. But with geocells of wider pocket openings enable the formation of rupture within the geocell mattress. Hence, it is concluded that the load carrying capacity of reinforced anchors which is dependent on the size of the rupture surface is influenced by the geometry of the geocell mattress.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43047014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cemented paste backfill (CPB) is fine-grained soil undergoing cementation. It is widely used in underground mining operations for ground support and mine waste (tailings) disposal. In the field, CPB may be placed in one layer (continuous filing), or multiple layers (discontinuous or sequential filling). Till today, no studies have addressed the effect of the different filling strategies on the response of CPB during cyclic events by using the shaking table technique. This manuscript presents new findings of investigating the effect of the different filling strategies of CPB on its geotechnical response to dynamic loading. CPB samples were prepared with different scenarios, including one Layered-CPB (discontinuous filling) sample at which each layer was cured to different curing time, and two unlayered-CPB (continuous filling) that were cured to 2.5 hrs and 4.0 hrs, respectively. All samples were exposed to same cyclic loading conditions using 1-D Shaking table. Geotechnical parameters or characteristics, including pore-water pressure, settlement, volumetric water content and liquefaction susceptibility were monitored or determined before, during, and after shaking. Obtained results indicate that Layered-CPB samples are resistant to liquefaction under the studied loading conditions, while the unlayered-CPB samples are prone to liquefaction under the studied conditions when they are cured to less than 4.0 hrs of curing time.
{"title":"Pore water pressure and liquefaction response of layered fine soils undergoing cementation","authors":"Imad Alainachi, M. Fall","doi":"10.1680/jphmg.21.00019","DOIUrl":"https://doi.org/10.1680/jphmg.21.00019","url":null,"abstract":"Cemented paste backfill (CPB) is fine-grained soil undergoing cementation. It is widely used in underground mining operations for ground support and mine waste (tailings) disposal. In the field, CPB may be placed in one layer (continuous filing), or multiple layers (discontinuous or sequential filling). Till today, no studies have addressed the effect of the different filling strategies on the response of CPB during cyclic events by using the shaking table technique. This manuscript presents new findings of investigating the effect of the different filling strategies of CPB on its geotechnical response to dynamic loading. CPB samples were prepared with different scenarios, including one Layered-CPB (discontinuous filling) sample at which each layer was cured to different curing time, and two unlayered-CPB (continuous filling) that were cured to 2.5 hrs and 4.0 hrs, respectively. All samples were exposed to same cyclic loading conditions using 1-D Shaking table. Geotechnical parameters or characteristics, including pore-water pressure, settlement, volumetric water content and liquefaction susceptibility were monitored or determined before, during, and after shaking. Obtained results indicate that Layered-CPB samples are resistant to liquefaction under the studied loading conditions, while the unlayered-CPB samples are prone to liquefaction under the studied conditions when they are cured to less than 4.0 hrs of curing time.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-07-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44085842","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Cone penetrometer test is widely used for in-situ site investigations and for establishing direct penetrometer to foundation or anchor design correlations. This paper focuses on the soil flow mechanisms during the continuous penetration of a cone penetrometer in layered clays. A series of centrifuge tests was conducted with the cone penetrating through soft-stiff, stiff-soft, soft-stiff-soft, and stiff-soft-stiff clay profiles. Particle image velocimetry allowed accurate resolution of the soil flow mechanism around the cone where a half cone model was penetrated into layered clays against a transparent window. The observed soil movement was compared with both previous observations for pile/cone, and with movement from shallow strain path method (SSPM). The comparison with SSPM results showed that SSPM can provide reasonable evaluations on maximum lateral and vertical displacements even though the upheave movement can be overestimated. The effect of soil layering on the failure mechanisms was studied extensively by exploring soil flow mechanisms and soil displacement paths at various distances from the advancing cone centreline and soil layer interface. The reported characteristics of cone penetration in layered soils provided in-depth understanding of cone penetration responses that will lead to the development of mechanism-based theoretical model for cone penetration in layered fine-grained soils.
{"title":"Soil Flow Mechanisms around Cone Penetrometer in Layered Clay – PIV Analysis in Centrifuge","authors":"Yue Wang, M. S. Hossain, Yuxia Hu","doi":"10.1680/jphmg.21.00042","DOIUrl":"https://doi.org/10.1680/jphmg.21.00042","url":null,"abstract":"Cone penetrometer test is widely used for in-situ site investigations and for establishing direct penetrometer to foundation or anchor design correlations. This paper focuses on the soil flow mechanisms during the continuous penetration of a cone penetrometer in layered clays. A series of centrifuge tests was conducted with the cone penetrating through soft-stiff, stiff-soft, soft-stiff-soft, and stiff-soft-stiff clay profiles. Particle image velocimetry allowed accurate resolution of the soil flow mechanism around the cone where a half cone model was penetrated into layered clays against a transparent window. The observed soil movement was compared with both previous observations for pile/cone, and with movement from shallow strain path method (SSPM). The comparison with SSPM results showed that SSPM can provide reasonable evaluations on maximum lateral and vertical displacements even though the upheave movement can be overestimated. The effect of soil layering on the failure mechanisms was studied extensively by exploring soil flow mechanisms and soil displacement paths at various distances from the advancing cone centreline and soil layer interface. The reported characteristics of cone penetration in layered soils provided in-depth understanding of cone penetration responses that will lead to the development of mechanism-based theoretical model for cone penetration in layered fine-grained soils.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47312524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
During previous earthquakes, displacements of shallow foundations on liquefiable sites caused significant damage to overlying super-structures leading to casualties and catastrophic economic loss. Various countermeasures have been developed to minimize liquefaction-related damages while minimizing cost and environmental impact. This study aims to evaluate the use of helical piles as a possible technique to mitigate the settlement, tilting, and sliding of shallow foundations on the liquefiable ground in seismic conditions. For this purpose, twelve 1g shaking table tests were conducted on uniform loose saturated Babolsar sand subjected to harmonic base input motion for (1) free-field condition, (2) a model foundation on the soil surface, and (3) a model foundation underpinned by helical piles. The effects of input motion amplitudes and the number of helical piles were investigated in terms of acceleration response, excess pore water pressure (EPWP), and foundation displacements. The results confirmed the satisfactory performance of helical piles in reducing shallow foundation displacements. In particular, the mean permanent settlements were reduced by 45% and 75% when using four and eight helical piles, respectively. Similar trends were observed for the shallow foundation permanent tilting and sliding; permanent tilting was reduced by 30% and 59% when using four and eight helical piles, respectively, while these results were 45% and 68% for the sliding.
{"title":"Mitigating Liquefaction-Induced Displacements of Shallow Foundation using Helical Piles","authors":"P. Esmaeilpour, Y. Jafarian, A. Cerato","doi":"10.1680/jphmg.21.00039","DOIUrl":"https://doi.org/10.1680/jphmg.21.00039","url":null,"abstract":"During previous earthquakes, displacements of shallow foundations on liquefiable sites caused significant damage to overlying super-structures leading to casualties and catastrophic economic loss. Various countermeasures have been developed to minimize liquefaction-related damages while minimizing cost and environmental impact. This study aims to evaluate the use of helical piles as a possible technique to mitigate the settlement, tilting, and sliding of shallow foundations on the liquefiable ground in seismic conditions. For this purpose, twelve 1g shaking table tests were conducted on uniform loose saturated Babolsar sand subjected to harmonic base input motion for (1) free-field condition, (2) a model foundation on the soil surface, and (3) a model foundation underpinned by helical piles. The effects of input motion amplitudes and the number of helical piles were investigated in terms of acceleration response, excess pore water pressure (EPWP), and foundation displacements. The results confirmed the satisfactory performance of helical piles in reducing shallow foundation displacements. In particular, the mean permanent settlements were reduced by 45% and 75% when using four and eight helical piles, respectively. Similar trends were observed for the shallow foundation permanent tilting and sliding; permanent tilting was reduced by 30% and 59% when using four and eight helical piles, respectively, while these results were 45% and 68% for the sliding.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2022-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42754865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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