D. Gaudio, J. Seong, S. Haigh, Giulia M. B. Viggiani, G. Madabhushi, R. Shrivatsava, Ravikant Veluvolu, P. Padhy
Centrifuge modelling is an effective tool to assess the response of reduced-scale structures subjected to earthquakes under increased gravity. Space limitations, however, force the model to be contained within relatively small boxes, whose boundaries may affect the seismic performance of the structure under consideration. In this paper, the influence of the proximity of the boundaries of an Equivalent Shear Beam (ESB) container during dynamic centrifuge tests of an onshore wind turbine resting on liquefiable soils is evaluated. To this end, numerical modelling of the ESB box was implemented in the Finite Element framework OpenSees, to replicate the results observed in the experiment. The hydraulic and mechanical soil parameters were calibrated against far-field centrifuge results only. From this calibration, the seismic performance of the raft foundation turned out to be in a good agreement with the experimental results for a seismic input capable of triggering liquefaction. A larger numerical model, where boundaries do not play any role, was then built, to compare its outcomes with those of the small model, thus allowing the effect of ESB boundaries to be assessed.
{"title":"Boundary effects on dynamic centrifuge modelling of onshore wind turbines on liquefiable soils","authors":"D. Gaudio, J. Seong, S. Haigh, Giulia M. B. Viggiani, G. Madabhushi, R. Shrivatsava, Ravikant Veluvolu, P. Padhy","doi":"10.1680/jphmg.21.00085","DOIUrl":"https://doi.org/10.1680/jphmg.21.00085","url":null,"abstract":"Centrifuge modelling is an effective tool to assess the response of reduced-scale structures subjected to earthquakes under increased gravity. Space limitations, however, force the model to be contained within relatively small boxes, whose boundaries may affect the seismic performance of the structure under consideration. In this paper, the influence of the proximity of the boundaries of an Equivalent Shear Beam (ESB) container during dynamic centrifuge tests of an onshore wind turbine resting on liquefiable soils is evaluated. To this end, numerical modelling of the ESB box was implemented in the Finite Element framework OpenSees, to replicate the results observed in the experiment. The hydraulic and mechanical soil parameters were calibrated against far-field centrifuge results only. From this calibration, the seismic performance of the raft foundation turned out to be in a good agreement with the experimental results for a seismic input capable of triggering liquefaction. A larger numerical model, where boundaries do not play any role, was then built, to compare its outcomes with those of the small model, thus allowing the effect of ESB boundaries to be assessed.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44609938","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}
The shaft capacity of driven piles in clay increases with time even after installation-induced consolidation is completed. However, existing studies have shown that these gains in capacity are variable and cannot be predicted reliably. Projects such as those involving life extension of existing offshore platforms (which often involve increased platform loads) as well as those considering foundation re-use provide the motivation for this paper, which investigates the potential for model scale testing to replicate the ageing characteristic of shaft friction in a laboratory environment. The study employs a number of model piles installed in reconstituted, high plasticity Onsoy clay in laboratory pressure chambers. The first time tension load tests on these piles, performed over the period of 1 year after installation, are compared with a similar series of tests on full-scale driven piles in Onsoy, Norway. Good agreement between laboratory and field experiments is observed when allowance is made for the significantly longer consolidation periods of the full-scale piles. This finding implies that ageing effects of shaft friction in clay can be investigated over relatively short time periods using model piles in laboratory testing chambers.
{"title":"Investigation of a laboratory-based approach to determine ageing of shaft friction of piles in clay","authors":"Bin Huang, B. Lehane, P. Watson","doi":"10.1680/jphmg.21.00016","DOIUrl":"https://doi.org/10.1680/jphmg.21.00016","url":null,"abstract":"The shaft capacity of driven piles in clay increases with time even after installation-induced consolidation is completed. However, existing studies have shown that these gains in capacity are variable and cannot be predicted reliably. Projects such as those involving life extension of existing offshore platforms (which often involve increased platform loads) as well as those considering foundation re-use provide the motivation for this paper, which investigates the potential for model scale testing to replicate the ageing characteristic of shaft friction in a laboratory environment. The study employs a number of model piles installed in reconstituted, high plasticity Onsoy clay in laboratory pressure chambers. The first time tension load tests on these piles, performed over the period of 1 year after installation, are compared with a similar series of tests on full-scale driven piles in Onsoy, Norway. Good agreement between laboratory and field experiments is observed when allowance is made for the significantly longer consolidation periods of the full-scale piles. This finding implies that ageing effects of shaft friction in clay can be investigated over relatively short time periods using model piles in laboratory testing chambers.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43591545","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}
Resistance offered by the soil to the cutting edge of the caisson and soil flow around the cutting edge will vary continuously during sinking. In this study, a series of 1g model tests are performe...
{"title":"Experimental studies on a circular open caisson","authors":"Jitesh T. Chavda, Goudappa R. Dodagoudar","doi":"10.1680/jphmg.20.00050","DOIUrl":"https://doi.org/10.1680/jphmg.20.00050","url":null,"abstract":"Resistance offered by the soil to the cutting edge of the caisson and soil flow around the cutting edge will vary continuously during sinking. In this study, a series of 1g model tests are performe...","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138505201","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}
Wen-bo Yang, Gaoyu Ma, J. Tu, Hao Kou, Yanyang Zhang, Yong Fang, Chuan He
This paper presents results of the voids influences on the dynamic response of tunnel linings and surrounding strata acquired in series of model tests. An experimental model of a tunnel was tested with a void of varying size (ratio of void width to tunnel diameter of 0.13, 0.27, and 0.4) and location (at tunnel apex, haunch and invert). During the tests, the tunnel invert were applied with three types of vibration loads: a sinusoidal load with a fixed frequency, a sinusoidal sweep load, and a simulated train load. The tunnel lining and soil response were recorded by accelerometers, with analysis results presented in both time and frequency domain. The experimental results manifest that the voids can have a distinct influence on the tunnel and soil dynamic response, with a clear amplification of tunnel and soil response for certain cases. The test results also demonstrate that the tunnel and soil response are sensitive to the void size and location in the near field. However, with increased distance from the excitation source, the void effects on the tunnel and soil dynamic response gradually declines.
{"title":"The Effects of Voids on the Dynamic Response of Tunnels Under Train Induced Vibration Loads","authors":"Wen-bo Yang, Gaoyu Ma, J. Tu, Hao Kou, Yanyang Zhang, Yong Fang, Chuan He","doi":"10.1680/jphmg.21.00023","DOIUrl":"https://doi.org/10.1680/jphmg.21.00023","url":null,"abstract":"This paper presents results of the voids influences on the dynamic response of tunnel linings and surrounding strata acquired in series of model tests. An experimental model of a tunnel was tested with a void of varying size (ratio of void width to tunnel diameter of 0.13, 0.27, and 0.4) and location (at tunnel apex, haunch and invert). During the tests, the tunnel invert were applied with three types of vibration loads: a sinusoidal load with a fixed frequency, a sinusoidal sweep load, and a simulated train load. The tunnel lining and soil response were recorded by accelerometers, with analysis results presented in both time and frequency domain. The experimental results manifest that the voids can have a distinct influence on the tunnel and soil dynamic response, with a clear amplification of tunnel and soil response for certain cases. The test results also demonstrate that the tunnel and soil response are sensitive to the void size and location in the near field. However, with increased distance from the excitation source, the void effects on the tunnel and soil dynamic response gradually declines.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43145833","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. Zhan, Y. You, Rui Zhao, Cheng Chen, Yun-min Chen
Soil-bentonite (SB) walls are commonly used as barriers for in situ containments at landfills. SB walls are designed to control the movement of persistent pollutants such as heavy metals in the long term. This paper presents centrifuge and numerical modelling of 50 years of performance of a loess-amended SB (LSB) wall in comparison with a conventional SB wall. Both walls were 28 m high and subjected to a hydraulic head difference of 2 m in the prototype. A purposely-designed apparatus was developed to impose the hydraulic head and a pollutant loading of 200 mg/L lead(II) on two barriers simultaneously. The apparatus was loaded on the ZJU400 geotechnical centrifuge and spun to 100-g. Similitudes of dispersion and adsorption of lead(II) in a centrifuge were discussed. Stress redistribution was observed in small-scale walls due to the enhanced soil arching effect. The lead(II) migration distance in the LSB wall after 50 years was 44.3% shorter than that in the SB wall. The predicted breakthrough time for the LSB wall was 149.1% longer than that for the SB wall when the thickness was 0.6 m. Retardation effects could be attributed to the significant ability of loess to absorb lead(II).
{"title":"Centrifuge Modelling of Retardation of Pb2+Migration in Loess–amended Soil–bentonite Barriers","authors":"L. Zhan, Y. You, Rui Zhao, Cheng Chen, Yun-min Chen","doi":"10.1680/jphmg.21.00007","DOIUrl":"https://doi.org/10.1680/jphmg.21.00007","url":null,"abstract":"Soil-bentonite (SB) walls are commonly used as barriers for in situ containments at landfills. SB walls are designed to control the movement of persistent pollutants such as heavy metals in the long term. This paper presents centrifuge and numerical modelling of 50 years of performance of a loess-amended SB (LSB) wall in comparison with a conventional SB wall. Both walls were 28 m high and subjected to a hydraulic head difference of 2 m in the prototype. A purposely-designed apparatus was developed to impose the hydraulic head and a pollutant loading of 200 mg/L lead(II) on two barriers simultaneously. The apparatus was loaded on the ZJU400 geotechnical centrifuge and spun to 100-g. Similitudes of dispersion and adsorption of lead(II) in a centrifuge were discussed. Stress redistribution was observed in small-scale walls due to the enhanced soil arching effect. The lead(II) migration distance in the LSB wall after 50 years was 44.3% shorter than that in the SB wall. The predicted breakthrough time for the LSB wall was 149.1% longer than that for the SB wall when the thickness was 0.6 m. Retardation effects could be attributed to the significant ability of loess to absorb lead(II).","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48247842","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}
S. N. Moghaddas Tafreshi, N. Karami, M. Rahimi, A. R. Dawson
In this study, a new three-dimensional (3D) reinforcement element comprising a horizontal ring connected to the vertical legs is introduced. A series of 1g laboratory scale tests were conducted on a circular footing that rested on a sand bed containing planar or new 3D-reinforcements. The effects of depth of first layer, reinforcements configuration number and spacing of layers are reported. Tests were performed on both discrete or contiguously attached elements. The new 3D elements were examined with either upward- or downward-facing legs. An improvement of about 16% was achieved by the upward-legged contiguous 3D elements over the performance delivered by planar contiguous elements. Also, results show that the vertical legs are capable of exerting passive forces on the soil and increasing the stiffness and bearing capacity of the composite system, but the contributory effect is more pronounced for the upward-leg configuration. Finally, 17% and 26% improvements were achieved, respectively, for two planar and two 3D-reinforcement layers when compared with that of a single layer. The concept of planar reinforcement connected to vertical legs, could be adapted for developing a more efficient generation of reinforcement, such as geogrids with vertical ‘legs’, to take advantage of the passive resistance generated by ‘legs’.
{"title":"Response of a Model Footing Reinforced by Novel Three Dimensional Elements","authors":"S. N. Moghaddas Tafreshi, N. Karami, M. Rahimi, A. R. Dawson","doi":"10.1680/jphmg.21.00055","DOIUrl":"https://doi.org/10.1680/jphmg.21.00055","url":null,"abstract":"In this study, a new three-dimensional (3D) reinforcement element comprising a horizontal ring connected to the vertical legs is introduced. A series of 1g laboratory scale tests were conducted on a circular footing that rested on a sand bed containing planar or new 3D-reinforcements. The effects of depth of first layer, reinforcements configuration number and spacing of layers are reported. Tests were performed on both discrete or contiguously attached elements. The new 3D elements were examined with either upward- or downward-facing legs. An improvement of about 16% was achieved by the upward-legged contiguous 3D elements over the performance delivered by planar contiguous elements. Also, results show that the vertical legs are capable of exerting passive forces on the soil and increasing the stiffness and bearing capacity of the composite system, but the contributory effect is more pronounced for the upward-leg configuration. Finally, 17% and 26% improvements were achieved, respectively, for two planar and two 3D-reinforcement layers when compared with that of a single layer. The concept of planar reinforcement connected to vertical legs, could be adapted for developing a more efficient generation of reinforcement, such as geogrids with vertical ‘legs’, to take advantage of the passive resistance generated by ‘legs’.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2022-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44352745","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}
Jinbiao Wu, G. Kouretzis, Jubert Pineda, L. Suwal, R. Gibson, M. Goodwin
This paper presents an air pluviation system, developed to facilitate 1-g physical model tests in granular soils. The deposition process is fully automated and requires minimal input from the operator, thereby significantly reducing the time required to deposit large volume of granular material, improving the uniformity of the prepared specimens, and the reliability of test results. The components comprising the pluviation system have been calibrated to produce loose-to-very dense sand beds, of relative density that ranges between Dr=7% and Dr>100% of the maximum density achieved with the procedures described in the pertinent standards. The testing chamber where sand is deposited is instrumented with an array of pressure sensors, and the rig is equipped with a miniature Cone Penetration Testing (mini-CPT) device. Measurements from the earth pressure sensors and cone tip resistance profiles are used to evaluate how friction at the sand-chamber interfaces affects the distribution of geostatic stresses inside the chamber, the uniformity of sand beds, and boundary effects during deposition and during mini-CPT testing. The air pluviation system allows preparing layered sand profiles by adjusting the deposition parameters on the fly, and this feature is demonstrated via the analysis of mini-CPT tests performed in layered sand beds.
{"title":"Development and operation of an automatic air pluviation system for physical modelling applications","authors":"Jinbiao Wu, G. Kouretzis, Jubert Pineda, L. Suwal, R. Gibson, M. Goodwin","doi":"10.1680/jphmg.21.00018","DOIUrl":"https://doi.org/10.1680/jphmg.21.00018","url":null,"abstract":"This paper presents an air pluviation system, developed to facilitate 1-g physical model tests in granular soils. The deposition process is fully automated and requires minimal input from the operator, thereby significantly reducing the time required to deposit large volume of granular material, improving the uniformity of the prepared specimens, and the reliability of test results. The components comprising the pluviation system have been calibrated to produce loose-to-very dense sand beds, of relative density that ranges between Dr=7% and Dr>100% of the maximum density achieved with the procedures described in the pertinent standards. The testing chamber where sand is deposited is instrumented with an array of pressure sensors, and the rig is equipped with a miniature Cone Penetration Testing (mini-CPT) device. Measurements from the earth pressure sensors and cone tip resistance profiles are used to evaluate how friction at the sand-chamber interfaces affects the distribution of geostatic stresses inside the chamber, the uniformity of sand beds, and boundary effects during deposition and during mini-CPT testing. The air pluviation system allows preparing layered sand profiles by adjusting the deposition parameters on the fly, and this feature is demonstrated via the analysis of mini-CPT tests performed in layered sand beds.","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2021-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47733419","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}
Measuring displacements in model tests typically involves contact-based sensors such as Linear Potentiometers, where contact between two moving parts occurs at the sensing point. The sensor's finit...
{"title":"Measuring Vertical Displacement Using Laser Lines and Cameras","authors":"S. Sinha, B. Kutter, K. Ziotopoulou","doi":"10.1680/jphmg.21.00038","DOIUrl":"https://doi.org/10.1680/jphmg.21.00038","url":null,"abstract":"Measuring displacements in model tests typically involves contact-based sensors such as Linear Potentiometers, where contact between two moving parts occurs at the sensing point. The sensor's finit...","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2021-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46114835","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}
Deep-buried tunnels have been increasingly used for transportation infrastructure and underground space development in major metropolitan areas around the world. Evaluation of the earth pressure on...
在世界主要大都市地区，深埋隧道越来越多地用于交通基础设施和地下空间开发。土压力评估。。。
{"title":"Study on Earth Pressure of Deep-Buried Tunnel in Layered Ground with Centrifuge Modeling","authors":"Xianfeng Ma, Mingyang Cao, Lei Wang, Yu Cong","doi":"10.1680/jphmg.21.00006","DOIUrl":"https://doi.org/10.1680/jphmg.21.00006","url":null,"abstract":"Deep-buried tunnels have been increasingly used for transportation infrastructure and underground space development in major metropolitan areas around the world. Evaluation of the earth pressure on...","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2021-09-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44610994","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}
R. P. Cunha, A. F. Cordeiro, M. Sales, H. Bernardes
The need for understanding the interaction between the elements of a piled raft foundation system becomes relevant when one of the piles collapses, presents a defect related to the installation pro...
当其中一根桩倒塌时，需要了解桩筏基础系统各元件之间的相互作用，这是一个与安装程序有关的缺陷。。。
{"title":"Physical 1g modelling of defective small-scale piled-raft systems founded in sand","authors":"R. P. Cunha, A. F. Cordeiro, M. Sales, H. Bernardes","doi":"10.1680/jphmg.21.00025","DOIUrl":"https://doi.org/10.1680/jphmg.21.00025","url":null,"abstract":"The need for understanding the interaction between the elements of a piled raft foundation system becomes relevant when one of the piles collapses, presents a defect related to the installation pro...","PeriodicalId":48816,"journal":{"name":"International Journal of Physical Modelling in Geotechnics","volume":null,"pages":null},"PeriodicalIF":1.9,"publicationDate":"2021-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46540536","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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