The design of piles in liquefiable soils requires careful consideration, both of the behaviour of the piles themselves and the impact on the supported structures. A freefield site response analysis using threedimensional. Analysis of laterally loaded piles in liquefiable soils with. Design examples design of pile foundations in liquefiable soils. The tools and procedures developed in the current project were based on uptodate models for liquefiable soil and for soilpile interaction, which obviated the need for many of. Modeling relies on use of validated elastoplastic material model for soil skeleton. Effects of soil liquefaction on pile foundation and its. Seismic bearing capacity of piles in liquefiable soils. Research dynamic stiffness of piles in liquefiable soils. The liquefiable soil was modelled in between two layers of nonliquefiable soil fig. Piles are considerably long element and the soil around it offers an excellent support.
A unified plasticity model for large postliquefaction shear deformation of sand provides the basis for the effective and efficient. The liquefiable soil was modelled in between two layers of nonliquefiable soil figure 3b, and a reinforcedconcrete pile with a fixed head was modelled to span the three soil layers with varying properties thickness, type, articulation. In soilsthat are assessed tobe non liquefiable,the conventional methods maybe adoptedto assess the ultimate shaft friction and end bearing capacity of the piles, including the possible effects of group action. The analysis of pile foundations in liquefiable soil and exposed to seismic loadings requires a thorough evaluation of the inertial loads. The moving soil can exert damaging pressures against the piles, leading to failure. The results show that in sloping grounds, when a nonliquefiable soil layer overlies a liquefiable soil layer and piles are embedded in the nonliquefiable soil layer, the lateral spreading has more. The tested groupedpiles connected with a pile cap are used to support 4 sets of model dry storage tank. Lateral capacity of piles in liquefiable soils 662 i. The effects of soil, pile, and earthquake parameters on the two potential pile failure mechanisms, bending and buc. Numerical model and input motion used in the analysis new pile d 1. In this paper, effective stress analysis is applied to a case study of a bridge pier founded on piles in liquefiable soil.
Canivan3 abstract the three most common ground improvement methodologies used by engineers to mitigate the potential damage from liquefaction include densification, drainage, and reinforcement. Behavior of piles in liquefiable soils during earthquakes. The pile models were buried in a twolayered soil system, consisting of a. Buckling of piles in foundation on liquefiable soils. The seismic design of pile foundations in these liquefiable soils poses very difficult problems in analysis and design. Both systems increase the bearing capacity of soil and allow reducing the.
Deficiencies of the existing pile failure theories are highlighted. Modeling relies on use of validate elastoplastic material model for soil skeleton, verified fully coupled porous media soil skeleton. Both experiments were conducted in similar ground conditions, ground water level, foundation dimensions, foundation contact pressure and input ground motions except the fact that in the second test helical piles have been utilized to underpin the shallow foundation situated atop the. The pile can be seriously destroyed by the soil liquefaction during strong earthquakes. Madabhushiii abstract an investigation into the base capacity of piles in passing through loose, lique. This paper develops a three dimensional finite element modelling method for piles in liquefiable ground and applies it to the analysis of seismic pile responses. Piles in layered liquefiable soils were analysed in detail as case histories show that these conditions increase the seismic. Behavior of floating piles in liquefiable soils ahmet pamuk 1 and thomas f. A nonlinear spring soil pile interface was adopted and compared with the no interface method in which the pile nodes were directly. Finite element model for piles in liquefiable groundjournal. The pile that located in liquefiable soil having proximity to be suffered by earthquake vibration should be designed for eulers buckling. Modeling relies on use of validated elastoplastic material model for soil skeleton, verified fully coupled porous media soil skeleton pore fluid water dynamic finite element formulation, and detailed load staging of fem models. Ge dan brown and associates pc dan brown and associates 2016 annual kansas city special conference. Various analyses procedures for piles in liquefiable soils are discussed.
Piles in liquefiable soils are conventionally designed against bending failure due to lateral loads arising from inertia andor. Previous research on dynamic stiffness performed for the washington state department of transportation wsdot resulted in the development of a manual that provided simple charts for estimating the stiffnesses of typical pile foundations in soil. The study examines the likely effects of liquefaction, cyclic ground displacements and soilstructure interaction on the bridge foundation during a strong earthquake. Evaluation of the effects of liquefaction on concrete pile. Jun 02, 2019 the liquefiable soil was modelled in between two layers of non liquefiable soil figure 3b, and a reinforcedconcrete pile with a fixed head was modelled to span the three soil layers with varying properties thickness, type, articulation. However, if the soil is soft and the supported load is large, then it is likely that the pile would buckle. The results show that in sloping grounds, when a non liquefiable soil layer overlies a liquefiable soil layer and piles are embedded in the non liquefiable soil layer, the lateral spreading has more influences on the damage of piles. Fujita ana buki k om uten and kaga wa uni versi ty, japa n abstrac t a general picture of the current state of the art and the emerging technology for dealing effectively with the seismic design and. The variations in bending moment along piles in different ground slopes for various conditions are presented in figs. A substantial portion of these ground failures and structural damages are a direct result of or related to lateral spreading. Finite element model for piles in liquefiable ground.
Maria giovanna durante universita degli studi del sannio, italy suresh r. The likely effects of liquefaction, lateral spreading and soilstructure interaction on the bridge. Pdf buckling and bending response of slender piles in. Seismic analysis of pile in liquefiable soil and plastic hinge.
Oct 01, 2002 this research developed tools and procedures for evaluating the stiffness of pile foundations in liquefiable soils during earthquakes. The paper provides a useful and current overview of this aspect of design of pile. Geotechnical engineering, department of civil engineering, nerist. Lateral response of pile foundations in liquefiable soils. Piled foundations introduction earthquake engineering. Failure mechanisms of pile foundations in liquefiable soil. The strength and stiffness of the soil decrease due to the increase in pore pressure. Design of pile foundations in liquefiable soils madabhushi, gopal, knappett, jonathan, haigh, stuart on. The liquefiable soil was modelled in between two layers of non liquefiable soil figure 3b, and a reinforcedconcrete pile with a fixed head was modelled to span the three soil layers with varying properties thickness, type, articulation. Pdf lateral loaded pile response in liquefiable soil. Liquefaction resistant structures university of washington. The liquefaction phenomenon of soil deposits can be described as the reduction of shear strength due to pore pressure buildup in the soil skeleton. In general, the observed damage and cracking of piles are often concentrated at the upper and lower boundaries of a liquefied soil layer, where there is a sudden change in soil properties, or at the connection with the pile cap. Piles in layered liquefiable soils were analysed in detail as case histories show that these conditions increase the seismic demand on pile foundations.
The concrete piles in liquefiable soil layers, as the depth increases from top to bottom of pile the displacement of pile decreases. Seismic design of piles in liquefiable soils springerlink. Evidently, such an assumption implies that piles would be better modelled as freestanding columns that extend to the entire liquefiable layer and fixed at some depth into the non liquefiable soil. Pdf seismic soilpile interaction in liquefiable soil sam. Densification of liquefiable soils using driven timber piles t. Three different soil profiles were considered in this project that varied in the thickness of both the liquefiable and nonliquefiable layers, pile. Collapse andor severe damage to pilesupported structures are still observed in liquefiable soils after most major earthquakes e. Due to axial symmetry, only half of the pile and surrounding soil were modelled for the original and. Abstract presented in this paper is numerical methodology to model and simulate behavior of piles in liquefiable soils. Jan 14, 2020 when using piles in liquefiable ground, the piles should be designed for the conditions induced by liquefaction, as the loss of soil support in the liquefied layer may cause large forces in the piles nishizawa et al. Buckling and bending response of slender piles in liquefiable. The high pore water pressures may lead to a significant degradation of strength and stiffness. Seismic response of single piles in liquefiable soil considering p.
Design of pile foundations in seismically liquefiable soils involves identifying the appropriate failure mechanisms. Numerical simulation of inclined piles in liquefiable soils. Lateral loaded pile response in liquefiable soil article pdf available in journal of geotechnical and geoenvironmental engineering 1295. On the efficiency of using helical piles in liquefiable.
The sand compaction pile scp method is one of the most important and costeffective techniques of soil improvement in many countries since 1950 to prevent liquefaction and to increase the bearing capacity for different type of soils. An increase in bending moment occurred as the ground slope increased. After liquefaction, if the residual strength of the soil is less than the static shear stresses caused by a sloping site or a free surface such as a river bank, significant lateral spreading or downslope displacements may occur. This paper presents a pseudostatic method for analysis of piles in liquefiable soil under seismic loads. Piles driven through a weak, potentially liquefiable, soil layer to a stronger layer not only have to carry vertical loads from the superstructure, but must also be able to resist horizontal loads and bending moments induced by lateral movements if the weak layer liquefies. Uplifting behavior of shallow buried pipe in liquefiable soil. The results show that in sloping grounds, when a nonliquefiable soil layer overlies a liquefiable soil layer and piles are embedded in the nonliquefiable soil layer, the lateral spreading has more influences on the damage of piles. Pile and rigid inclusion systems represent a useful practice to support structures in the presence of liquefiable soils in seismic zones. Following are the effects of liquefaction on pile foundations which are discussed in details. Lateral spreading is particularly damaging if a non liquefiable crust rides on top of the liquefied soil. Dynamic analyses of piles subjected to both vertical and horizontal loading under seismic conditions are of great significance to geotechnical and practicing engineers and the numerical methodology proposed in the present study fills the existing research gap. Concrete piles should be detailed for strength and ductility as for columns section 10. This interaction is more complex in the presence of liquefiable soils.
The input required are the saturated or bulk densities. Previous research on dynamic stiffness performed for the washington state department of transportation wsdot resulted in the development of a manual that provided simple charts for estimating the stiffnesses of typical pile foundations in soil deposits. The seismic design of pile foundations in these liquefiable soils. The performance of pile foundations in liquefiable soil subjected to earthquake loading is a very complex process. Numerical simulation of inclined piles in liquefiable soils 2 sponsored by peer mazzoni et al. Design of pile foundations in liquefiable soils world scientific.
The seismic design of pile foundations in liquefiable soils poses very difficult problems in analysis and design. Seismic response of pile foundations in liquefiable soil. The design of earthquakeresistant structures depends greatly on the soilfoundationstructure interaction. Soil dynamics 2010 fifth international conference on recent advances in geotechnical earthquake engineering and soil dynamics may 24th, 12.
Evidently, such an assumption implies that piles would be better modelled as free. Seismic response of single piles in liquefiable soil. The seismic behaviour of liquefiable soil was taken into consideration by an appropriate constitutive soil model. Effects of soil liquefaction on pile foundation and its remedies. The likely effects of liquefaction, lateral spreading and soil structure interaction on the bridge during a predicted future earthquake are examined. Piles can be damaged further where a liquefiable soil layer is overlaid by a nonliquefiable layer. Presented in this paper is numerical methodology to model and simulate behavior of piles in liquefiable soils. Jul 10, 2014 the uplifting behavior of pipe in liquefied soil is a multiforce coupled behavior, which is not only dependent on the buildup of excess pore pressure but also determined by the shear strength of the soil, relative displacement of pipe and soil, the amplitude of the input seismic wave, and so forth. This paper presents the response of piles in liquefiable soil under seismic loads. When evaluating the seismic performance of pile foundations in liquefiable soils, it is critically important to estimate the effects of cyclic ground displacements on. Based on the observed case histories, the possible mechanisms of failure of the pile foundations are postulated.
The effects of soil, pile, and earthquake parameters on the two potential pile failure mechanisms, bending and. Sufficient resistance can be achieved by piles of larger dimensions and. The impact loading technique is the first method to compact the sand. Densification of liquefiable soils using driven timber piles. The cyclic study comprises two distinct phases, the first considering the response of piles when subjected only to cyclic soil displacements, and the second considering the. Effective stress analysis of piles in liquefiable soil. The study examines the likely effects of liquefaction, cyclic ground displacements and soil structure interaction on the bridge foundation during a strong earthquake. Pile group in threelayer soil profile subject to lateral spreading. The book also deals with the additional loading attracted by piles in liquefiable soils due to lateral spreading of sloping ground. Zimmie2 abstract centrifuge tests were conducted to study the behaviors of floating single and pile groups 2x2. Depending on the occurrence of liquefaction, the pile foundation may undergo substantial shaking, while the soil is in a fully liquefied state and soil stiffness is at a minimum. Abstract presented in this paper is numerical methodology to model and simulate behavior of piles in liquefiable soil s. The cyclic study comprises two distinct phases, the first considering the response of piles when subjected only to cyclic soil displacements, and the second considering the pile response when both cyclic soil displacements and superstructure inertial forces.
Behavior of piles in liquefiable soils duri ng earthquakes. Pile and rigid inclusion systems represent a useful practice to support structures in the presence of liquefiable soils in. Studies of particular aspects of pilesoil interaction were made. Seismic response and numerical analysis methods springer theses 9783662496619. This research developed tools and procedures for evaluating the stiffness of pile foundations in liquefiable soils during earthquakes. Pile foundations are the most common form of deep foundations that are used both onshore and offshore to transfer large superstructural loads into competent. Pile group in twolayer soil profile subject to lateral spreading. Effect of the soilpilestructure interaction in seismic. It was shown that in case, the maximum bending moment was likely to occur at the middle of the pile on the depth of the liquefiable soil for both free and fixedhead piles. A finite difference based computer program flac3d is used to model a single pile and obtain the deflection and bending. Lateral capacity of piles in liquefiable soil s 662 i. Soil liquefaction occurs when a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress such as shaking during an earthquake or other sudden change in stress condition, in which material that is ordinarily a solid behaves like a liquid.
The tools and procedures developed in the current project were based on uptodate models for liquefiable soil and for soil pile interaction, which obviated the need for many of. Seismic analysis of pile in liquefiable soil and plastic. Several failure mechanisms of piles in liquefiable soils such as pile buckling and excessive settlement of piles in liquefied soil layers were developed at cambridge university based on extensive. Centrifuge seismic test on seismic behavior of pile group. Buckling of piles in foundation on liquefiable soils civil. Another zerolength element with qz spring material was inserted between the pile toe node and the subjacent soil node. Only limited attention has been paid to the axial response of piles during and after an earthquake. In the analysis, finite element 3d models are created considering different soil layers as liquefiable soil. Numerical modeling and simulation of pile in liquefiable soil.
Effective zone radius of sand compaction piles in liquefiable soils. Lateral response of pile foundations in liquefiable soils sciencedirect. For all three cases, it was concluded that pile length and the thickness of the liquefiable layer have little influence on the maximum lateral displacements. The book provides designers and practicing civil engineers with a sound knowledge of pile behaviour in liquefiable soils and easytouse methods to design pile foundations in seismic regions. Pdf collapse andor severe damage to pilesupported structures are still observed in liquefiable soils after most major earthquakes. Numerical modeling and simulation of pile in liquefiable. Design of pile foundations in liquefiable soils request pdf. Seismic risk management of piles in liquefiable soils. A comprehensive overview of pile damages observed in the recent earthquakes is presented in this paper.
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