Pub Date : 2021-04-30DOI: 10.37308/DFIJNL.20200701.220
J. Turner
Load tests on drilled shaft foundations with rock sockets in sedimentary formations associated with various Triassic Basins in the Mid-Atlantic region show that some generalizations are possible for estimating geotechnical resistances. Axial load tests on drilled shafts in locations several hundred miles apart produce surprisingly similar results. The common feature is the geology: all of the load-tested rock sockets considered were constructed in sedimentary rock associated with one of the rift basins that developed in response to breaking apart of the supercontinent Pangaea that began during the late Triassic Period (about 220 million years ago) and coincided with opening of the Atlantic Ocean. More specifically, all of the tested rock sockets were in the ‘red bed’ facies of the rift basin sediments consisting of reddish-brown siltstone, sandstone, and shale. Each of the projects described herein and the associated load tests are described and used to illustrate fundamental principles of rock socket design and how load testing can be used as a design tool. The important role of quality construction, in combination with quality assurance through inspection and testing, is emphasized, especially as it relates to the evaluation of base resistance for rock socket design.
{"title":"Geotechnical Resistances of Drilled Shafts in Triassic Basin Sedimentary Rocks","authors":"J. Turner","doi":"10.37308/DFIJNL.20200701.220","DOIUrl":"https://doi.org/10.37308/DFIJNL.20200701.220","url":null,"abstract":"Load tests on drilled shaft foundations with rock sockets in sedimentary formations associated with various Triassic Basins in the Mid-Atlantic region show that some generalizations are possible for estimating geotechnical resistances. Axial load tests on drilled shafts in locations several hundred miles apart produce surprisingly similar results. The common feature is the geology: all of the load-tested rock sockets considered were constructed in sedimentary rock associated with one of the rift basins that developed in response to breaking apart of the supercontinent Pangaea that began during the late Triassic Period (about 220 million years ago) and coincided with opening of the Atlantic Ocean. More specifically, all of the tested rock sockets were in the ‘red bed’ facies of the rift basin sediments consisting of reddish-brown siltstone, sandstone, and shale. Each of the projects described herein and the associated load tests are described and used to illustrate fundamental principles of rock socket design and how load testing can be used as a design tool. The important role of quality construction, in combination with quality assurance through inspection and testing, is emphasized, especially as it relates to the evaluation of base resistance for rock socket design.","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133931593","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-30DOI: 10.37308/DFIJNL.20200831.222
Alejandro Martinez
Piles can be subjected to axial loading in opposite directions during their installation and service life. For instance, piles for offshore jacket structures and load testing reaction systems are subjected to compressive loading during installation and tensile or cyclic loading during service life. This creates a design dilemma: while a large skin friction can lead to refusal at shallower depths than required during driving, it also promotes a large pile axial capacity. This paper describes the load-transfer behavior of piles with surfaces inspired by the belly scales of snakes that mobilize a direction-dependent skin friction. The investigation presented herein consists of a series of twelve centrifuge pile load tests on bio-inspired and smooth reference piles in dense and loose deposits of Ottawa F65 sand. Test results indicate that greater skin friction forces are mobilized when the bio-inspired piles are displaced in the cranial direction (i.e. soil moving against asperities) relative to the caudal direction (i.e. soil moving along asperities). This is observed during pushing and driving installation, where greater skin friction forces were mobilized during installation by pushing in the cranial direction and driving in the cranial direction required more blows per meter. Similarly, the skin friction mobilized during pullout tests was between 82% and 198% greater in the cranial direction than in the caudal direction, and the skin friction mobilized during pullout by the bio-inspired pile in the cranial direction was between 560% to 845% greater than that mobilized by the reference untextured pile. During cyclic loading, degradation of the skin friction magnitude and pile secant stiffness was observed in both cranial and caudal directions; however, the mobilized magnitudes were generally greater in the cranial direction. Discussion is provided on the potential benefits that the bio-inspired surface texture could realize on the overall performance of axially-loaded piles.
{"title":"Skin Friction Directionality in Monotonically- and Cyclically-Loaded Bio-inspired Piles in Sand","authors":"Alejandro Martinez","doi":"10.37308/DFIJNL.20200831.222","DOIUrl":"https://doi.org/10.37308/DFIJNL.20200831.222","url":null,"abstract":"Piles can be subjected to axial loading in opposite directions during their installation and service life. For instance, piles for offshore jacket structures and load testing reaction systems are subjected to compressive loading during installation and tensile or cyclic loading during service life. This creates a design dilemma: while a large skin friction can lead to refusal at shallower depths than required during driving, it also promotes a large pile axial capacity. This paper describes the load-transfer behavior of piles with surfaces inspired by the belly scales of snakes that mobilize a direction-dependent skin friction. The investigation presented herein consists of a series of twelve centrifuge pile load tests on bio-inspired and smooth reference piles in dense and loose deposits of Ottawa F65 sand. Test results indicate that greater skin friction forces are mobilized when the bio-inspired piles are displaced in the cranial direction (i.e. soil moving against asperities) relative to the caudal direction (i.e. soil moving along asperities). This is observed during pushing and driving installation, where greater skin friction forces were mobilized during installation by pushing in the cranial direction and driving in the cranial direction required more blows per meter. Similarly, the skin friction mobilized during pullout tests was between 82% and 198% greater in the cranial direction than in the caudal direction, and the skin friction mobilized during pullout by the bio-inspired pile in the cranial direction was between 560% to 845% greater than that mobilized by the reference untextured pile. During cyclic loading, degradation of the skin friction magnitude and pile secant stiffness was observed in both cranial and caudal directions; however, the mobilized magnitudes were generally greater in the cranial direction. Discussion is provided on the potential benefits that the bio-inspired surface texture could realize on the overall performance of axially-loaded piles.","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134258098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-30DOI: 10.37308/DFIJNL.20200923.224
B. Fellenius
Results of a static loading test were used together with soil exploration records in a survey comprising analysis of the test records and estimating settlement of piled foundation to support a pipe rack. The test pile was a strain-gage instrumented, 400-mm diameter, precast, prestressed concrete pile driven into a clay and silt deposit to 25 m embedment. Two main issues were expected to be addressed by the survey participants: First, realization that the strain records were affected by presence of residual force in the pile and, second, calculation of the settlement of the piled foundation expected from the foundation load. A total of 52 submissions were received from 20 different countries. Only 12 of the submissions realized the presence of residual force. Most submissions reported a calculated settlement of the piled foundations ranging from 10 mm through 50 mm; however, 11 reported values between 60 and 200 mm. Surprisingly, only 20 submissions reported ground surface settlement close to the 200-mm value resulting from textbook analysis based on the available information. The subsequent construction of the piled foundations coincided with placing a fill across the site and lowering of the groundwater table, thus, causing a general subsidence.
{"title":"Results of an Instrumented Static Loading Test and Its Application to Design Compilation of an International Survey","authors":"B. Fellenius","doi":"10.37308/DFIJNL.20200923.224","DOIUrl":"https://doi.org/10.37308/DFIJNL.20200923.224","url":null,"abstract":"Results of a static loading test were used together with soil exploration records in a survey comprising analysis of the test records and estimating settlement of piled foundation to support a pipe rack. The test pile was a strain-gage instrumented, 400-mm diameter, precast, prestressed concrete pile driven into a clay and silt deposit to 25 m embedment. Two main issues were expected to be addressed by the survey participants: First, realization that the strain records were affected by presence of residual force in the pile and, second, calculation of the settlement of the piled foundation expected from the foundation load. A total of 52 submissions were received from 20 different countries. Only 12 of the submissions realized the presence of residual force. Most submissions reported a calculated settlement of the piled foundations ranging from 10 mm through 50 mm; however, 11 reported values between 60 and 200 mm. Surprisingly, only 20 submissions reported ground surface settlement close to the 200-mm value resulting from textbook analysis based on the available information. The subsequent construction of the piled foundations coincided with placing a fill across the site and lowering of the groundwater table, thus, causing a general subsidence.","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127570357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-04-30DOI: 10.37308/DFIJNL.20200409.216
R. Moghaddam
This study presents the development and calibration of resistance factors for the serviceability limit state (SLS) condition (φSLS) used in the load and resistance factor design (LRFD) of deep foundations. The performance function was established based on load corresponding to tolerable displacement (Qδtol) and design load (Qd). A dataset of published full-scale load tests including projects from Texas, Missouri, Arkansas, Louisiana, and New Mexico was compiled and consisted of 60 load test cases comprising 33 driven piles and 27 drilled shafts. Resistance factors for SLS conditions were calibrated for tolerable displacements using both the Monte Carlo simulation (MCS) and the First Order Second Moment (FOSM) approaches. From the calibration study, resistance factors at SLS conditions were obtained ranging from 0.33 to 0.62 using FOSM method and 0.37 to 0.67 using the MCS for driven piles. In the case of drilled shafts, SLS resistance factors ranged from 0.37 to 0.77 following the FOSM method and 0.41 to 0.86 based on MCS.
{"title":"Resistance Factors at Serviceability Limit State Using the Texas Cone Penetrometer as the Predictive Model","authors":"R. Moghaddam","doi":"10.37308/DFIJNL.20200409.216","DOIUrl":"https://doi.org/10.37308/DFIJNL.20200409.216","url":null,"abstract":"This study presents the development and calibration of resistance factors for the serviceability limit state (SLS) condition (φSLS) used in the load and resistance factor design (LRFD) of deep foundations. The performance function was established based on load corresponding to tolerable displacement (Qδtol) and design load (Qd). A dataset of published full-scale load tests including projects from Texas, Missouri, Arkansas, Louisiana, and New Mexico was compiled and consisted of 60 load test cases comprising 33 driven piles and 27 drilled shafts. Resistance factors for SLS conditions were calibrated for tolerable displacements using both the Monte Carlo simulation (MCS) and the First Order Second Moment (FOSM) approaches. From the calibration study, resistance factors at SLS conditions were obtained ranging from 0.33 to 0.62 using FOSM method and 0.37 to 0.67 using the MCS for driven piles. In the case of drilled shafts, SLS resistance factors ranged from 0.37 to 0.77 following the FOSM method and 0.41 to 0.86 based on MCS.","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"120 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133598613","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-01-19DOI: 10.37308/DFIJNL.20200525.218
A. Marinucci
A full-scale field demonstration project consisting of installation, instrumentation, testing, and extraction of augered cast-in-place (ACIP) piles located in central Florida was undertaken in conjunction with the Florida Department of Transportation and the University of South Florida. Seven instrumented ACIP piles, with a nominal diameter of 457 mm (18 in) or 610 mm (24 in), were installed in mainly sand and silty sand. Load testing was performed on six ACIP piles: two in compression, two in tension, and two laterally. In addition, one of the ACIP piles was extracted for visual inspection and comparison to predictions and measurements. The program demonstrated the fully monitored installation and load tested performance of instrumented ACIP piles, along with the use of manual and automated monitoring; use and accuracy of embedded instrumentation, including thermal integrity profiling (TIP) and embedded strain gages; load-displacement behavior of tested ACIP piles; and the integrity and as-constructed geometry of an exhumed ACIP pile. This paper presents the details, results from the different testing performed, and observations from the experimental field program.
{"title":"Full-Scale Load Testing and Extraction of Augered Cast-in-Place (ACIP) Piles in Central Florida","authors":"A. Marinucci","doi":"10.37308/DFIJNL.20200525.218","DOIUrl":"https://doi.org/10.37308/DFIJNL.20200525.218","url":null,"abstract":"A full-scale field demonstration project consisting of installation, instrumentation, testing, and extraction of augered cast-in-place (ACIP) piles located in central Florida was undertaken in conjunction with the Florida Department of Transportation and the University of South Florida. Seven instrumented ACIP piles, with a nominal diameter of 457 mm (18 in) or 610 mm (24 in), were installed in mainly sand and silty sand. Load testing was performed on six ACIP piles: two in compression, two in tension, and two laterally. In addition, one of the ACIP piles was extracted for visual inspection and comparison to predictions and measurements. The program demonstrated the fully monitored installation and load tested performance of instrumented ACIP piles, along with the use of manual and automated monitoring; use and accuracy of embedded instrumentation, including thermal integrity profiling (TIP) and embedded strain gages; load-displacement behavior of tested ACIP piles; and the integrity and as-constructed geometry of an exhumed ACIP pile. This paper presents the details, results from the different testing performed, and observations from the experimental field program.","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130116218","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-31DOI: 10.37308/DFIJNL.20200820.221
N. Aarthi
A critical appraisal of the reviewed literature revealed that there are very limited studies available on the strength characteristics focusing on the load-settlement behavior of sand compaction columns (SCCs) when installed in cohesionless deposits. The method, though contemporary to the reputed stone column technique, is not yet studied rigorously in the available past studies, more precisely on the load-bearing characteristics when compared to the latter. Therefore the present study focuses on studying the behavior of multiple column composite foundation supported by sand compaction columns installed in loose to medium dense sands on a lab-scale numerical model. The study is carried out using commercially available finite element (FE) code 3D PLAXIS. Spacing to diameter ratio (S/D) ranging from 1.5 to 3.5 and initial relative density (RD) from 30 to 60% was adopted to study the changes in the load-settlement behavior of the improved deposit. Extending the FE model to further parametric study, the effect of angle of internal friction of the column sand and diameter of the column on the bearing capacity and settlement characteristics were analysed with and without normalization. From the results obtained, it is found that, for the considered FE model, the improved deposit with 3D spacing between the SCCs behaves distinctly different from all other cases analyzed.
{"title":"Behavior of Sand Compaction Columns Installed in Cohesionless Deposits","authors":"N. Aarthi","doi":"10.37308/DFIJNL.20200820.221","DOIUrl":"https://doi.org/10.37308/DFIJNL.20200820.221","url":null,"abstract":"A critical appraisal of the reviewed literature revealed that there are very limited studies available on the strength characteristics focusing on the load-settlement behavior of sand compaction columns (SCCs) when installed in cohesionless deposits. The method, though contemporary to the reputed stone column technique, is not yet studied rigorously in the available past studies, more precisely on the load-bearing characteristics when compared to the latter. Therefore the present study focuses on studying the behavior of multiple column composite foundation supported by sand compaction columns installed in loose to medium dense sands on a lab-scale numerical model. The study is carried out using commercially available finite element (FE) code 3D PLAXIS. Spacing to diameter ratio (S/D) ranging from 1.5 to 3.5 and initial relative density (RD) from 30 to 60% was adopted to study the changes in the load-settlement behavior of the improved deposit. Extending the FE model to further parametric study, the effect of angle of internal friction of the column sand and diameter of the column on the bearing capacity and settlement characteristics were analysed with and without normalization. From the results obtained, it is found that, for the considered FE model, the improved deposit with 3D spacing between the SCCs behaves distinctly different from all other cases analyzed.","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116630750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-31DOI: 10.37308/DFIJNL.20190716.208
M.G. Souissi
The capacity-to-torque ratio, Kt, has been used in the design of helical piles and anchors for over half a century. Numerous research efforts have been conducted to accurately predict this capacity-to-torque ratio. However, almost of all these Kt factors are based on shaft geometry alone. The capacity-to-torque ratio described herein was found to depend on the shaft diameter, shaft geometry, helix configuration, axial load direction, and installation torque. In this study, 799 full scale static load tests in compression and tension were conducted on helical piles of varying shaft diameters, shaft geometry, and helix configurations in different soil types (sand, clay, and weathered bedrock). The collected data were used to study the effect of these variables on the capacity-to-torque ratio and resulted in developing a more reliable capacity-to-torque ratio, Km, that considers the effect of the variables mentioned above. The study shows that the published Kt values in AC358 (ICC-ES Acceptance Criteria for Helical Piles Systems and Devices) underestimate the pile capacity at low torque and overestimate it at high torque. In addition, and based on probability analysis, the predicted capacity using the modified Km results in a higher degree of accuracy than the one based on the published Kt values in AC358.
{"title":"Helical Pile Capacity-to-Torque Correlation: A More Reliable Capacity-to-Torque Factor Based on Full Scale Load Tests","authors":"M.G. Souissi","doi":"10.37308/DFIJNL.20190716.208","DOIUrl":"https://doi.org/10.37308/DFIJNL.20190716.208","url":null,"abstract":"The capacity-to-torque ratio, Kt, has been used in the design of helical piles and anchors for over half a century. Numerous research efforts have been conducted to accurately predict this capacity-to-torque ratio. However, almost of all these Kt factors are based on shaft geometry alone. The capacity-to-torque ratio described herein was found to depend on the shaft diameter, shaft geometry, helix configuration, axial load direction, and installation torque. In this study, 799 full scale static load tests in compression and tension were conducted on helical piles of varying shaft diameters, shaft geometry, and helix configurations in different soil types (sand, clay, and weathered bedrock). The collected data were used to study the effect of these variables on the capacity-to-torque ratio and resulted in developing a more reliable capacity-to-torque ratio, Km, that considers the effect of the variables mentioned above. The study shows that the published Kt values in AC358 (ICC-ES Acceptance Criteria for Helical Piles Systems and Devices) underestimate the pile capacity at low torque and overestimate it at high torque. In addition, and based on probability analysis, the predicted capacity using the modified Km results in a higher degree of accuracy than the one based on the published Kt values in AC358.","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126237642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-31DOI: 10.37308/DFIJNL.20200121.213
S. Saye
This paper presents observations of the influence of pile installation methods on the measured side resistance of driven pipe piles bearing in plastic soils. Pile installation practices that can reduce the capacity of completed piles in plastic soils from that calculated include re-driving of piles after partial or full dissipation of excess pore water pressure, long installation times, slow jacking, the influence of surface casing in soft soils, and the use of vibratory hammers. Selected case histories are used to illustrate how deviations from rapid and nearly continuous pile installation can result in poor performance. Designers and Contractors need to be more aware of the damaging effects of these practices and that the selected design approach may not effectively consider the selected installation procedures. Where project requirements dictate use of these installation approaches that damage pile side resistance, the proposed construction influence factors may be used to modify a SHANSEP-based side resistance method to estimate the potential reductions in side resistance associated with the selected approach. Although the number of case histories available are too few to characterize the reliability of the construction influence factor approach, the cases sufficiently demonstrate the damage that can occur when these practices are used and the importance of construction procedures for driven pipe pile foundations that minimize or avoid damage to side resistance and to highlight where special design and testing are merited. struction actions or interruptions can have on the pile side resistance. A generalized design approach is then presented to help designers and contractors address this issue. Saye et al. (2013) presented an empirical approach to assess the average side resistance of driven pipe piles in plastic soils using an adaptation of the Stress History and Normalized Soil Engineering Properties, SHANSEP, concept (Ladd and Foott, 1974). This approach includes assessments of the soil overconsolidation ratio, OCR, developed using both oedometer tests and an empirical correlation to undrained shear strength data. The empirical correlations in the SHANSEP-based approach incorporate the results of selected pile loading tests and laboratory OCR assessments presented by Almeida et al., (1996) and others to capture the effect of soil state on the strength of the soil-pile interface. Experience applying the SHANSEP-based approach shows that some pile installation practices can damage the pile side resistance. These damaging practices are identified. This paper then applies the SHANSEP-based approach to a small set of loading tests and soil property records to demonstrate how reductions in the side resistance of driven pipe piles in plastic soils may result from specific pile installation practices. When recognized, these damaging practices can either be avoided or considered in the planning and installation of the foundations. Specifically, thi
{"title":"Use of Case Histories to Illustrate the Effect of Installation Activities on the Side Resistance of Pipe Piles in Plastic Soils","authors":"S. Saye","doi":"10.37308/DFIJNL.20200121.213","DOIUrl":"https://doi.org/10.37308/DFIJNL.20200121.213","url":null,"abstract":"This paper presents observations of the influence of pile installation methods on the measured side resistance of driven pipe piles bearing in plastic soils. Pile installation practices that can reduce the capacity of completed piles in plastic soils from that calculated include re-driving of piles after partial or full dissipation of excess pore water pressure, long installation times, slow jacking, the influence of surface casing in soft soils, and the use of vibratory hammers. Selected case histories are used to illustrate how deviations from rapid and nearly continuous pile installation can result in poor performance. Designers and Contractors need to be more aware of the damaging effects of these practices and that the selected design approach may not effectively consider the selected installation procedures. Where project requirements dictate use of these installation approaches that damage pile side resistance, the proposed construction influence factors may be used to modify a SHANSEP-based side resistance method to estimate the potential reductions in side resistance associated with the selected approach. Although the number of case histories available are too few to characterize the reliability of the construction influence factor approach, the cases sufficiently demonstrate the damage that can occur when these practices are used and the importance of construction procedures for driven pipe pile foundations that minimize or avoid damage to side resistance and to highlight where special design and testing are merited. struction actions or interruptions can have on the pile side resistance. A generalized design approach is then presented to help designers and contractors address this issue. Saye et al. (2013) presented an empirical approach to assess the average side resistance of driven pipe piles in plastic soils using an adaptation of the Stress History and Normalized Soil Engineering Properties, SHANSEP, concept (Ladd and Foott, 1974). This approach includes assessments of the soil overconsolidation ratio, OCR, developed using both oedometer tests and an empirical correlation to undrained shear strength data. The empirical correlations in the SHANSEP-based approach incorporate the results of selected pile loading tests and laboratory OCR assessments presented by Almeida et al., (1996) and others to capture the effect of soil state on the strength of the soil-pile interface. Experience applying the SHANSEP-based approach shows that some pile installation practices can damage the pile side resistance. These damaging practices are identified. This paper then applies the SHANSEP-based approach to a small set of loading tests and soil property records to demonstrate how reductions in the side resistance of driven pipe piles in plastic soils may result from specific pile installation practices. When recognized, these damaging practices can either be avoided or considered in the planning and installation of the foundations. Specifically, thi","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"39 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123596488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-12-31DOI: 10.37308/DFIJNL.20190617.206
P. Cosentino
Excessive pile rebound has been occurring for over a decade, when high displacement prestressed concrete piles are driven mostly with single acting diesel hammers in Florida’s low permeability very fine sand blends. This very complex engineering phenomenon, which occurs due to interactions between the soil, pile, and hammer; typically is observed at depths great than approximately 15 m (50 feet). Rebound greatly diminishes the end bearing capacities, causing various problems and significant cost increases. Findings from several research studies have produced some obvious trends based on grain size, Atterberg limits and cyclic triaxial testing. Excessive rebound was categorized as movements exceeding 12.5 mm (0.5-inches) while no-rebound was considered to be less than 6 mm (0.25-inches). Coarse grained rebound soils were very fine sands, passing the number 100 sieve, with silts and clays. According to the Unified Soils Classification System they classified as SM and have silt contents between about 20 and 40%. Cohesive rebound soils were highly plastic clays, classified as CH and also have silt contents between about 20 and 40%. Cyclic triaxial testing indicated that rebound soils are much more resilient than no-rebound soils, requiring many more cycles to produce strains of 2.5, 5, 10 and 15 percent. Historical Overview of Pile Rebound Historically, pile driving rebound has been referred to differently by various authors. Some call it pile “bounce” (Murrell et al., 2008), others call it “high pile rebound” (HPR) (Hussein, 2006; Cosentino et al., 2010, and 2016). Still others (Authier and Fellenius, 1980; Likins, 1983) use the terminology “high quake” (i.e., the limit or end of the elastic pile movement during a single hammer blow) as part of its description. Hussien (2006) notes that HPR increases as driving depths increase and that HPR is a function of the soils dynamic response, which is described terms of damping. During an evaluation of a 762 mm (30 -inch) instrumented PCP test pile along Florida’s State Road 528 in Brevard County, he documented a nearly 30 percent decrease in static capacity (5400 to 3900 kN) during 41 single acting air hammer blows and a corresponding 45 percent increase in rebound (9 to 13 mm). The instrumentation included strain gages and accelerometers mounted near the top of the pile. This decrease in capacity occurred even though the driving blows per 25 mm (1-inch) increased from 12 to 17 or 42 percent. The author produced excellent load versus deflection data from both static load testing and corresponding dynamic testing. Low displacement piles may rebound, but their rebound could mostly be the result of elastic compression. Elastic compression (δ) is defined as the load (P) times the pile length (L) divided by the pile area (A) and elastic modulus (E) or δ = PL/AE. When A is small, as is the case for low displacement piles, δ increases and may be a major component of the rebound (Nguyen et al., 2019). Murrell et al
数据取自12个不同的lo
{"title":"How Soils Can Help Predict High Rebound of Prestressed Concrete Displacement Piles","authors":"P. Cosentino","doi":"10.37308/DFIJNL.20190617.206","DOIUrl":"https://doi.org/10.37308/DFIJNL.20190617.206","url":null,"abstract":"Excessive pile rebound has been occurring for over a decade, when high displacement prestressed concrete piles are driven mostly with single acting diesel hammers in Florida’s low permeability very fine sand blends. This very complex engineering phenomenon, which occurs due to interactions between the soil, pile, and hammer; typically is observed at depths great than approximately 15 m (50 feet). Rebound greatly diminishes the end bearing capacities, causing various problems and significant cost increases. Findings from several research studies have produced some obvious trends based on grain size, Atterberg limits and cyclic triaxial testing. Excessive rebound was categorized as movements exceeding 12.5 mm (0.5-inches) while no-rebound was considered to be less than 6 mm (0.25-inches). Coarse grained rebound soils were very fine sands, passing the number 100 sieve, with silts and clays. According to the Unified Soils Classification System they classified as SM and have silt contents between about 20 and 40%. Cohesive rebound soils were highly plastic clays, classified as CH and also have silt contents between about 20 and 40%. Cyclic triaxial testing indicated that rebound soils are much more resilient than no-rebound soils, requiring many more cycles to produce strains of 2.5, 5, 10 and 15 percent. Historical Overview of Pile Rebound Historically, pile driving rebound has been referred to differently by various authors. Some call it pile “bounce” (Murrell et al., 2008), others call it “high pile rebound” (HPR) (Hussein, 2006; Cosentino et al., 2010, and 2016). Still others (Authier and Fellenius, 1980; Likins, 1983) use the terminology “high quake” (i.e., the limit or end of the elastic pile movement during a single hammer blow) as part of its description. Hussien (2006) notes that HPR increases as driving depths increase and that HPR is a function of the soils dynamic response, which is described terms of damping. During an evaluation of a 762 mm (30 -inch) instrumented PCP test pile along Florida’s State Road 528 in Brevard County, he documented a nearly 30 percent decrease in static capacity (5400 to 3900 kN) during 41 single acting air hammer blows and a corresponding 45 percent increase in rebound (9 to 13 mm). The instrumentation included strain gages and accelerometers mounted near the top of the pile. This decrease in capacity occurred even though the driving blows per 25 mm (1-inch) increased from 12 to 17 or 42 percent. The author produced excellent load versus deflection data from both static load testing and corresponding dynamic testing. Low displacement piles may rebound, but their rebound could mostly be the result of elastic compression. Elastic compression (δ) is defined as the load (P) times the pile length (L) divided by the pile area (A) and elastic modulus (E) or δ = PL/AE. When A is small, as is the case for low displacement piles, δ increases and may be a major component of the rebound (Nguyen et al., 2019). Murrell et al","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122129952","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-10-13DOI: 10.37308/dfijnl.20191014.211
V. Aguilar
Public transportation agencies commonly use drilled shaft foundations as support of mast arm traffic signs and signal pole structures. These structures and their foundations are subjected to windinduced torsion. Design provisions can be found in AASHTO specifications for structural supports for highway signs, luminaires and traffic signals; nevertheless, those standards do not provide guidance to estimate the torsional resistance of drilled shaft foundations, or what an appropriate factor of safety (or resistance factor) for design could be. Although load and resistance factors format is desired because AASHTO is moving in that direction, still many Departments of Transportation design requirements are based on factors of safety. In this study, a probabilistic approach is used to recommend a rational procedure to determine factors of safety that consider the uncertainties and the consequences of failure. This procedure can be modified for load and resistance factors design calibration, as well. The skin friction approach was calibrated employing reliability analysis, available statistics, published experimental data, and simulations. However, a lack of field test data has been noticed. Factors of safety for cohesive, cohesionless, and layered soils are recommended. They are presented as a function of the target reliability index, and which in-situ test is performed to obtain the soil strength properties. Three alternatives were considered: standard penetration test, cone penetration test, and vane shear test. The procedure described can be used by practitioners to select appropriate factors of safety based on local conditions when statistical parameters from a particular site investigation are available.
{"title":"Safety Factor for Drilled Shaft Foundations Subjected to Wind-Induced Torsion","authors":"V. Aguilar","doi":"10.37308/dfijnl.20191014.211","DOIUrl":"https://doi.org/10.37308/dfijnl.20191014.211","url":null,"abstract":"Public transportation agencies commonly use drilled shaft foundations as support of mast arm traffic signs and signal pole structures. These structures and their foundations are subjected to windinduced torsion. Design provisions can be found in AASHTO specifications for structural supports for highway signs, luminaires and traffic signals; nevertheless, those standards do not provide guidance to estimate the torsional resistance of drilled shaft foundations, or what an appropriate factor of safety (or resistance factor) for design could be. Although load and resistance factors format is desired because AASHTO is moving in that direction, still many Departments of Transportation design requirements are based on factors of safety. In this study, a probabilistic approach is used to recommend a rational procedure to determine factors of safety that consider the uncertainties and the consequences of failure. This procedure can be modified for load and resistance factors design calibration, as well. The skin friction approach was calibrated employing reliability analysis, available statistics, published experimental data, and simulations. However, a lack of field test data has been noticed. Factors of safety for cohesive, cohesionless, and layered soils are recommended. They are presented as a function of the target reliability index, and which in-situ test is performed to obtain the soil strength properties. Three alternatives were considered: standard penetration test, cone penetration test, and vane shear test. The procedure described can be used by practitioners to select appropriate factors of safety based on local conditions when statistical parameters from a particular site investigation are available.","PeriodicalId":339795,"journal":{"name":"DFI Journal: The Journal of the Deep Foundations Institute","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127441946","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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