Challenges and Recommendations for Steel H-Piles Driven in Soft Rock
K. Ng and T. Sullivan
ABSTRACT: The capacity of a pile driven in soft rock depends on soil confinement along the pile and rock at its toe; these are rarely known during design. This design challenge often leads to a large discrepancy between estimated and measured resistances. Results of six bridge projects completed in Wyoming, USA, are presented to highlight the challenges pertaining to present design and construction practices of driven piles in rock. The results show that static analysis methods, dynamic analysis methods, and structural analyses yield inconsistent pile resistance estimations. A recommendation considering the structure-geo-material interaction is proposed to improve the design and construction of steel H-piles driven in soft rock.
KEYWORDS: Pile, LRFD, Rock, WEAP, CAPWAP
Experimental Study on Pile Foundations having Batter Piles Subjected to Combination of Vertical and Horizontal Loading at 1-g Field
Anh-Tuan Vu, Tatsunori Matsumoto, Shun-ichi Kobayashi and Shinya Shimono
ABSTRACT: In this study, the behaviours and resistance mechanisms of pile foundations having batter piles were investigated through a series of vertical load tests and combination load tests on model foundations in dry sand ground at 1-g field. Pile foundation models consisting of 3 piles and 6 piles, with or without batter piles, were used in the experiments. The model pile was close-ended pipe with a length of 255 mm and an outer diameter of 20 mm. Dry silica sand having a relative density, Dr, of about 82% was used for the model ground throughout the experiments. Triaxial CD tests of the sand were carried out to obtain the mechanical properties and to investigate the behaviour of the sand. The results indicate that the piled raft having batter piles is the most effective to increase the resistances (in both vertical and horizontal directions) and reduce the inclination.
KEYWORDS: Piled raft, Pile group, Batter pile, Dry sand, Model test
Fundamental Experiments on a Reinforcement Method using Sheet Pile Wall for Bridge Pile Foundations Subjected to Pile Embedment Reduction and Numerical Validation
T. Tikanta, T. Matsumoto, A. T. Vu, S. Kobayashi, S. Shimono and C. Bamrungwong
ABSTRACT: Development of an effective countermeasure for existing bridge foundations subjected to the influence of riverbed excavation in Thailand is the main objective of this research. Due to the riverbed soil excavation for the utilization in construction works for many years, the level of riverbed of the Mae Nam Ping River has been considerably decreased, resulting in reduction of embedment lengths of piles for many bridge foundations. Erosion was not a cause of the lowering of the riverbed. Reductions of bearing capacity due to the lowering of riverbed soil is the main cause of bridge pile foundation settlements or collapses at present. In order to prevent the damages of existing bridge pile foundations caused by the riverbed soil excavation, a reinforcement method using sheet piles called “Sheet Pile Wall (SPW) reinforcement” is proposed in this paper. The proposed SPW reinforcement method consists of 2 simple steps without new additional piles or any modifications of existing structures. Firstly, sheet piles are constructed surrounding the existing problematic bridge pile foundation. Finally, the empty space inside the SPW is filled with sand or other porous materials such as crushed concrete. In order to investigate the performance of the proposed SPW reinforcement method, series of load tests on model pile foundations in dry sand were carried out. The experimental results show that the proposed SPW reinforcement method is very efficient and promising. Numerical simulation of an experiment using FEM was also carried out to get more insight into the mechanism of the SPW method and validate the proposed SPW method.
KEYWORDS: Reinforcement, Existing bridge pile foundation, Riverbed soil excavation, Model load test, Numerical analysis
Numerical Studies on Performance of Offshore Wind Turbine Composite Suction Pile in Sand Subjected to Combined Loading
San-Shyan Lin, Yun-Chih Chiang, Xin-Hua Lin, Hsing-Yu Wang, and Sung-Shan Hsiao
ABSTRACT: In order to increase the overall bearing capacity of a wind turbine foundation, a composite type of suction pile is proposed in this paper. Numerical studies on the performance of the proposed suction pile with enlarged lid size subjected to combined lateral and axial loading is presented in the paper. The numerical model is firstly validated by comparison with other numerical study results. The parametric analysis results prove a suction pile with enlarged lid size has better performance than a normal suction pile on both the overall bearing capacity and the stability of the foundation.
KEYWORDS: Composite suction piles, Combined loading, Numerical study
Pile Group Interaction Based on Field Monitoring and Load Tests
K. Yamashita, S. Wakai, J. Hamada and T. Tanikawa
ABSTRACT: The effects of pile group interaction on settlements were investigated based on the results of two monitoring cases of piled raft foundations and single pile load tests in soft ground. The first case was a piled raft consisting piles embedded in deep dense sand with large spacing supporting a 12-story building, and the case second was a piled raft consisting of friction piles with large spacing supporting a 7-story building. The load-settlement data of the monitored and test piles of different dimensions were compared using a modification factor derived from an elastic solution for the axial response of a single pile. Based on the investigation, it was found that the modified load-settlement data of the monitored piles were generally consistent with the static load-settlement curve of a single pile. Therefore, no significant effects of pile group interaction on settlement were found. In such cases as pile groups with large spacing, single pile load test data can be more useful in the settlement prediction of piled rafts and pile groups. In addition, it was found that the pile head stiffness of the equivalent static load-settlement curve derived from the rapid load testing in clay soils using the UPM was considerably large compared to the stiffness of the static load test curve, as pointed out by previous studies.
KEYWORDS: Piled raft foundation, Field monitoring, Static load test, Rapid pile load testing, Effects of group interaction, Rate effects
In-situ Full Scale Load Tests and Reliability Evaluation of Bearing Capacity for Nodular Cast-in-place Concrete Pile
K. Watanabe, A. Mitsumori, H. Nishioka and M. Koda
ABSTRACT: In recent years, both the height and weight of buildings have increased. This trend is especially noticeable in the central urban areas of Japan. Both tensile and compressive forces occur in foundations such as these piles because of the overturning moment from earthquake and wind loads. To address these situations, new types of foundations need to be developed for high-rise superstructures. One approach is the nodular cast-in-place concrete pile, which has a nodular part at the mid-section of the pile. In situ full-scale load tests were carried out to estimate the bearing capacity of the nodular cast-in-place concrete pile. The bearing capacity was also estimated according to the Design Standards for Railway Structures and Commentary. This paper firstly summarizes the in-situ full scale load tests, and then describes the results of standard bearing capacity based on the data from the in situ full-scale load tests, finally mentions the estimation of ground resistance coefficient for nodular cast-in-place concrete piles.
KEYWORDS: Nodular cast-in-place concrete pile, In-situ full scale load test, Bearing capacity, Reliability evaluation
Development of Steel Pipe Pile Combined with Ground Improvement in Narrow Spaces
K. Watanabe, T. Yamamoto and T. Sudo
ABSTRACT: In recent years, works to improve existing structures and strengthen their seismic resistance have increased. Pile construction in narrow spaces is constrained by the site and process. Therefore, a construction method combining steel pipe piles with ground improvement using a mechanical agitator (e-column construction method®) was developed. This paper briefly summarizes the construction method, presents the static load tests and rapid load tests, and discusses the results of load tests. The results of the loading tests suggest that the bearing capacity can be evaluated by using the undrained shear strength and SPT N-value. Also, a simplified rapid loading test can be applied to validating the bearing capacity at a construction site. For the joint of the steel pipe piles, the maximum tensile resistance obtained from the experiment was larger than that obtained from the calculation formula.
KEYWORDS: Steel pipe pile, Ground improvement, Bearing capacity, Full scale load test
Design and Analysis of Composite Foundation for High-rise Buildings
K. Watanabe, N. Suzuki and M. Sahara
ABSTRACT: A composite foundation combines several types of foundation to support a single superstructure. Thus, this type of foundation should be carefully designed considering the stress in the boundary section caused by the difference in the deformation behaviors of each foundation type. This paper shows two design cases of composite foundations for high-rise buildings. These two foundations were designed by considering the effect of deformation on the results of a static FEM analysis. The slab settlement was measured upon completion of con-struction. It was confirmed that composite foundations deform within a presupposed range.
KEYWORDS: Composite Foundation, Performance-based Design, FEM
Pervious Material Made from Landslide Debris for Road Base Construction
Hung-Jiun Liao, Chin-Lung Chiu, Chung-Kuang Chien, Yi-En Tang, Heng-Chih Cheng
ABSTRACT: Landslide is a common event for mountain roads in Taiwan. Among the landslides, some are up slope failure; others are down slope failure. For the former, a large quantity of landslide debris will be generated and then block the road traffic. It would be a good idea to move the debris from the up slope failure site to fill the lost road base resulted by the down slope failure. This paper will introduce an on-site mixing method to prepare pervious-CLSM (controlled low strength material) from the landslide debris by mixing it with proper amount of cement and water. Through the mixing process, the fine soils in the debris will flocculate to a sizable particles and/or stick to the surface of aggregates. As a result, the fines content of the debris can be eliminated and a pervious-CLSM is made. Through the binding effect of cement, the pervious-CLSM can also have moderate strength to maintain the stability of filled embankment and to sustain the traffic load as well. Together with geo-grid, a wrap-faced reinforced embankment as the road base can be constructed quickly using the site prepared CLSM as well as a backhoe machine and hand tools. After verified with a full scale embankment construction, the feasibility of building a pervious embankment in short time with the pervious-CLSM made from landslide debris has been confirmed. But the control of water content of the mixture on-site is crucial for this method.
KEYWORDS: Landslide debris, Road base, Previous material, CLSM
Advances in Numerical Modelling of Different Ground Improvement Techniques
E. Heins, K.-F. Seitz, A. Chmelnizkij, M. Milatz and J. Grabe
ABSTRACT: Common ground improvement techniques like deep vibration compaction, vibro replacement stone columns, dynamic compac-tion or vibratory rolling are still a subject of research. Research fields are for example optimized layouts or estimation of main influencing parameters. A lot of successful scientific research is conducted on piles and piling using various numerical methods. Therefore, it is assumed that numerical models can be used to improve ground improvement methods. In this contribution, different ground improvement techniques and numerical models to simulate the influence of these techniques on the surrounding soil are presented. Furthermore, optimization methods and potentials of ground improvement techniques are shown.
KEYWORDS: Ground improvement, Numerical modeling, Mathematical optimization, Deep vibration compaction, Vibro replacement stone columns, Dynamic compaction, Vibratory rollers
Load Sharing Mechanism of Combined Pile-Raft Foundation (CPRF) under Seismic Loads
Ashutosh Kumar and Deepankar Choudhury
ABSTRACT: In the present work, the load sharing mechanism under seismic loads for fully hinged (H) and fully rigid (R) connected Combined Pile-Raft Foundation (CPRF) have been studied by using three-dimensional finite element based geotechnical software. The importance of connection condition has been investigated in detail. After successful validation of experimental results of the proposed numerical model of CPRF, the same model has been analyzed under different earthquake loading conditions. Results of the present analyses show that connection rigidity had little influence on vertical settlement of CPRF but had pronounced response on the load sharing by foundation components. In the purview of seismic loading, lateral stiffness played a pivotal role in deciding the load-settlement, lateral displacement, bending moment in piles and inclination response of CPRF. The load sharing by foundation components is governed by mobilization of lateral displacement. Initially, raft shares higher proportion of seismic loads but reaches to limiting value at relatively smaller displacement thereafter piles bear the remaining load. CPRF-H reached the limiting value of inclination at 4% of normalized lateral displacement which is unlike the case for CPRF-R. The findings of the present study provide insight into the behavior of CPRF subjected to seismic loads and can be used for the seismic design of CPRF.
KEYWORDS: Pile-raft, Pseudo-static, Seismic, Settlement, Load sharing, Lateral displacement
Deflection Behaviour of GFRP Bar Reinforced Concrete Passive Bored Pile in Deep Excavation Construction
J. L. Zhou, E. Oh, X. Zhang, M. Bolton, H. Y. Qin and L. Zhang
ABSTRACT: This paper describes the investigation of a glass fibre reinforced polymer bar (GFRP bar) as a replacement for a traditional steel bar reinforcement in bored concrete piles with specific application to deep excavation construction. These two concrete passive piles were cast and experiments were conducted with reference to soil excavation. Normally, the point load which is applied to the pile head is provided by static lateral load test equipment for determining the pile behaviour; however, these two piles suffered from changed earth pressure during excavation. The amount and location of horizontal movement was monitored along the pile length by an inclinometer system which contained a PVC tube and a readout probe. The deflection behaviours of GFRP piles during the installation of one concrete and two steel supports were provided. It is concluded that, based on the difference between the total accumulated deflection of each pile, the GFRP bar reinforced concrete piles can resist the lateral loading and can provide an alternative to traditionally reinforced concrete piles used in shield construction.
KEYWORDS: Deflection behavior, GFRP bar, Passive piles, Deep excavation, Soil movement
Loading and Dynamic Response Considerations for the Design of Wind Turbine Foundations on South African Soils
Byron Mawer, Denis Kalumba, Charles Warren-Codrington
ABSTRACT: Wind energy has been selected an appropriate means of diversifying South Africa’s energy mix and improving its electricity capacity in view of growing socio-economic and environmental pressures. However, this comes with engineering challenges, one being designing efficient foundations for wind turbine structures. This discussion was centred on the sources of loading that wind turbines experience and the consequences of this on the geotechnical design of gravity footings. Rotational stiffness of the foundation was shown to have an important effect on the dynamic response of the wind turbine tower, and thus, on the assumptions surrounding the calculation of the natural frequency of the global system. Means of assessing the rotational and lateral stiffness as well as models investigating soil stiffness inclusion in natural frequency assumptions were evaluated in the context of a South African case study, specific to the South Eastern city of Port Elizabeth. Soils of this region were dominated by weathered silty fine sands and varying degrees of pedogenic calcrete, creating unique challenges in design. Soil stiffness effects on natural frequency assumptions were found to be more critical than the minimum stiffness requirements applied by design guidelines and had a notable effect on dynamic amplification for an undamped system.
KEYWORDS: Natural frequency; Rotational stiffness; Cyclic loading; Pedocretes; Wind turbines, Gravity foundations
Comparison of Numerical Analyses of Behaviour of Column-Reinforced Foundations
Mounir Bouassida, Mnaouar Klai, Seifeddine Tabchouche And Mekki Mellas
ABSTRACT: This paper studies the prediction of behaviour of foundations resting on a soil reinforced by sand and stone columns. The preliminary design is based on an optimized improvement area ratio predicted by the methodology proposed by Bouassida & Carter (2014). The prediction of the behaviour of the reinforced soil is predicted by numerical computations carried out by Plaxis V9.2D and FLAC3D codes in plane strain and axisymmetric conditions. A Tunisian case history of oil tank is investigated. When assuming the linear elastic behaviour for constituents of reinforced soil, it is noted that the predictions of settlements given by Columns 1.01 software are in good agreement with numerical results obtained by Plaxis and FLAC3D codes. Comparison between those approaches shows the validity of results using the Columns 1.01 software. By adopting the Mohr-Coulomb failure criterion for columns material and the hardening soil model for soft clay, the evolution of long term settlement predicted by Plaxis code showed the acceleration of the consolidation of the compressible soft clay due to the enhanced drainage property of column material.
KEYWORDS: Behaviour, Case history, Settlement, Numerical, Sand column, Soft clay
Particle Image Velocimetry Analysis on the Sinking of Shallow Foundation in 2D
P. Pizette and N-E. Abriak
ABSTRACT: This paper focuses on the development of punching device dedicated to study the failure of 2D analogue soil. In order to follow the kinematic behaviours of soil, Particle Image Velocimetry (PIV) analysis has been developed and tested in the case of the shallow foundations. The results show that the field of the soil displacement under the foundation can be followed via the PIV method. In particular, the image analysis results are qualitatively in good agreement with the Prandlt scheme.
KEYWORDS: Schneebeli’s material, Shallow foundation, PIV
Attempt of Simple Calculation on Studying Failure Mechanism of DM Columns
B. T. T. Nguyen, T. Takeyama and M. Kitazume
ABSTRACT: A simple calculation, based on limit equilibrium method, was performed to evaluate the failure pattern of deep mixing (DM) columns, used to reinforce an embankment slope. The failure modes of the columns are important in the application of DM columns, according to Japanese and the US guidelines. By using laboratory tests and numerical analysis, a certain failure mode took place with certain ground conditions, while an overall view with various modes cannot be observed. In this study, a trial of limit equilibrium method to access the failure mode of the columns is focused with an overall mechanism. As a result, while the calculation can simply predict the failure pattern of the DM columns, a parametric study was also performed to evaluate the effect of several improvement factors. Because the calculation was simplified with several assumptions, the further application of the method needs to be validated and evaluated by further studies.
KEYWORDS: Limit equilibrium method, Centrifuge model, Deep mixing, Shallow mixing, Failure pattern
Microzonation of Liquefaction Hazard using Liquefaction Index in Babol City
A. Janalizadechoobbasti, M. Naghizadeh rokni, R. Charaty
ABSTRACT: One of the devastating effects of the earthquake is on liquefaction phenomenon site, which is one of the most important and most complex topics in seismic geotechnical engineering. Liquefaction is a phenomenon that occurs in loose, saturated sediments without stickiness in undrained conditions under the influence of waves caused by earthquakes or heavy static load. In order to cope with devastating effects of this phenomenon, it is essential to identify areas prone to liquefaction. This identification can be conducted as microzoning, in which risk capacity is determined in different areas. Thus, in this paper, the zoning map of Babol liquefaction risk will be provided. In this regard, a study was conducted on the soils in Babol and after examining different areas of the city, laboratory results and field studies of more than 50 boreholes in different areas with a depth of 20 m were analyzed for finding liquefaction and non-liquefaction segments. In this study, different approaches were used including Seed, Iwasaki, Haeri and Yasrebi, Chin & Zhang and Sewmez & Gocojlou procedures and finally, a computer program was written for examining and providing microzoning map of Babol liquefaction risk.
KEYWORDS: Liquefaction, Microzonation, Babol, Index, Seismic Geotechnic
