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![Fig. 4. The critical sliding surfaces found by Hassiotis et al. [17],...](profile/Ernesto-Ausilio/publication/240915289/figure/fig4/AS:357958799118338@1462355436061/The-critical-sliding-surfaces-found-by-Hassiotis-et-al-17-Hull-and-Poulos-30-and_Q320.jpg)
In this paper, the kinematic approach of limit analysis is used to analyse the stability of earth slopes reinforced with piles. First, the case of slope without piles is considered and a procedure is developed to calculate the safety factor for the slope. Results are compared with those obtained using both the limit equilibrium method and more comp...
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... pointed out by Karal [22], a direct consequence of Eq. (2) is that, for frictional materials, the sliding surfaces are surfaces of potential yield, and the displacements and the failure mechanism depend on the safety factor. This defi- nition of FS is also adopted in the present study. The kinematically admissible mechanism considered is shown in Fig. 1, where the sliding surface is described by the log-spiral ...
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... r 0 =radius of the log-spiral with respect to angle 0 . The failing soil mass rotates as a rigid body about the centre of rotation with angular velocity ! : . This mechanism, which was earlier considered by Chen [21], is geometrically defined by angles 0 , 0 , h ( Fig. 1) and mobilized angle of shearing resistance tg' FS . The slope geometry is specified by height H, and angles and which are also indicated in Fig. ...
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... soil mass rotates as a rigid body about the centre of rotation with angular velocity ! : . This mechanism, which was earlier considered by Chen [21], is geometrically defined by angles 0 , 0 , h ( Fig. 1) and mobilized angle of shearing resistance tg' FS . The slope geometry is specified by height H, and angles and which are also indicated in Fig. ...
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... unit weight; functions f 1 -f 4 depend on the angles 0 , h , , and 0 , and the mobilized angle of shearing resistance. Expressions for f 1 -f 4 can be found in Chen [21]; for the sake of completeness they are also reported in the Appendix of this paper. In deriving Eq. (4), it is assumed that the sliding surface passes below the toe of the slope (Fig. 1). However, for the case in which the sliding surface passes through the toe of the slope, the same expression for W : can be used provided f 4 =0 and 0 ...
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... the slope is subjected to a surcharge boundary load, as shown in Fig. 1, the rate of work done by this load ...
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... L=distance between the failure surface at the top of the slope and the edge of the slope (Fig. 1); q=applied normal traction; s=applied tangential traction. For the rigid-block mechanism considered, the only energy dissipation takes place along the sliding surface. The rate of energy dissipation, D : , can be written as [21] By equating the rate of external work to the rate of energy dissipation, we ...
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... distance L is indicated in Fig. 1. For a given FS value, an upper bound for the slope height is obtained solving ...
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... that increases as the surface develops from the top to the base of the slope. For a rotational failure mechanism as shown in Fig. 5, the required stabilising moment due to F, with respect to the rota- tion centre, has an arm that increases as the location of the piles approaches to the slope toe, and consequently force F decreases. However, Figs. 8-10 show that the piles are also very effective when they are located between the middle and the toe of the slope, especially when m is assumed to be zero. The figures also show that the region where the piles are more effective reduces as increases, and is located closer to the toe of the slope. Therefore, when the achievement of a high ...
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... slope safety factor without piles, FS 0 , can be determined from the results presented in Fig. 11 which have been obtained using Eq. (13). As can be noted, the values of FS 0 decrease when increasing the slope angle and increasing the parameter l c' that has been defined in a previous section. It should be noted that the value of l c' also indicates the position of the potential sliding surface within the slope. As pointed out by ...
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... becomes deeper and expands into the soil, especially when the slope is gentle. By contrast, as the value of l c' increases, the critical sliding surface becomes increas- ingly shallow. Duncan and Wright [37] considered sliding surfaces of circular shape. However, this also occurs when log-spiral sliding surfaces are considered, as shown in Fig. 12. The piles are assumed to be located at the middle of the slope which should be a suitable location for the piles. Following Poulos [8], a retaining structure which is located near the toe or the crest of the slope could restrain only a small mass of the soil, while a lot of the soil mass behind or in front of the structure could be ...
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Citations
... Among them, the anti-slide pile usage is the most prevalent geotechnical measure employed in landslide prevention and control projects (Lirer 2012;Zhang et al. 2019) because piles can transfer the sliding force from the bearing segment (piles above the sliding surface) to a stable layer by anchoring the segment (piles below the sliding surface). As a result, the stability of the slope is considerably enhanced (Ausilio et al. 2001;Tang et al. 2014). Other engineering structures, such as retaining walls (Hu et al. 2022;Kashani et al. 2022) and anchor bolt meshes Zhao et al. 2021), have also been employed to further reinforce slope stability. ...
Currently, most designs for landslide hazard control employ geotechnical measures as the primary strategy and vegetation measures as the supplemental strategy. However, few studies have investigated the synergistic protection effectiveness of combining geotechnical and vegetation measures. To evaluate the synergistic mechanism between roots and piles and the corresponding slope-protection effect, we focused on tap-like arbor roots and anti-slide piles and used 3D printing technology to efficiently build composite models of roots and soil. In addition, this study uses square steel to simulate anti-slide piles, conducts a series of experiments with different support modes, and monitors the deformation and failure processes of shallow soil slopes. The results show that (1) both roots and piles could improve the anti-sliding force; under the synergistic support of roots and anti-slide piles (SSRAP), the postpeak anti-sliding force attenuation rate decreases, with the residual anti-sliding force demonstrating a significant advantage. (2) Root-support measures can only control the deformation of the slope bottom, while pile-support measures can effectively control the deformation of different slope areas. (3) The slope surface is characterized by numerous small cracks with poor connectivity under root support. The process of crack expansion is obviously delayed under pile support, and the SSRAP inherits their respective advantages, further enhancing the slope integrity. These results fill the research gap in the synergistic mechanism of geotechnical and vegetation measures and present the development of effective strategies for the comprehensive prevention and control of landslide disasters.
... The efficiency of one or more rows of piles as a stabilisation measure, is usually evaluated on the basis of the increment in the factor of safety of the slope due to the presence of the piles [LEE et al., 1995;HASSIOT-IS et al., 1997;CAI and UGAI, 2000;AUSILIO et al., 2001;ASHOUR and ARDALAN, 2012;KOURKOULIS et al., 2012]. However, considering that the groundwater level changes due to rainfall are cyclic and transient, the occurrence in some time intervals of limit conditions of the pile-slope system does not necessarily imply a collapse, but rather the accumulation of permanent displacements. ...
Installing one or more rows of piles in unstable slopes is recognised as an effective measure for their stabilisation. The effect of the presence of the piles on slope stability is usually quantified in terms of a safety factor against a possible reactivation of the landslide. However, such an event might still occur for example owing to a significant raising of the groundwater level, especially for active landslides in clay that are periodically reactivated by rainfall. Although the mobility of this type of landslides is usually prevented or attenuated by suitable drainage systems, the piles could be designed to perform a function of reducing the landslide displacements during the reactivation stages. Therefore, a more rational and economical design approach than the conventional limit equilibrium method, consists in admitting the occurrence in some time intervals of limit conditions of the slope in the presence of the piles, and evaluating the effectiveness of such a stabilising measure in terms of accumulated permanent displacements of the unstable soil mass. The resulting displacements should avoid the occurrence of significant damage and preserve the serviceability of existing structures. In this context, a simplified methodology is employed in the present paper to predict the rainfall-induced movements of landslides in the presence of stabilising piles. Specifically, the proposed method uses a water balance equation to relate rainfall to groundwater level changes, and a motion equation of a two-block system representing the landslide body, to relate the aforementioned changes to the landslide displacements accounting for the passive resistance exerted by the piles. This force is evaluated on the basis of the arrangement of the piles and their expected failure mode, using some practical solutions available in the literature. The method is applied to some case studies to quantify the effectiveness of the piles in reducing the landslide mobility, and to show how this method can be used for predictive purposes. The obtained results demonstrate that the presence of the piles can significantly reduce the landslide mobility during the reactivation stages. Their effectiveness mainly depends on the location of the piles respect to the slip surface and their geometric and material features, which in turn influence the occurring failure mode of the pile.
... In this approach, lateral forces and a moment were exerted at the potential sliding surface to account for the presence of piles. The obtained results agree well with those derived from Bishop's method and with the upper-and lower-bound solutions of limit analysis [36]. By combining the 3D finite element method with the commonly used analytical techniques, Kourkoulis et al. developed a hybrid design methodology for the anti-slide piles. ...
... According to Ausilio et al., piles are very effective when placed in between the toe and middle of the slope. The optimal location was suggested nearer to the toe of slope where the factor of safety is maximum and stabilizing force is minimum [36]. Wei et al. recommended the position between the halfway slope and center of the critical slip surface of the unreinforced slope as the optimal location, and the precise location is closer to the central part of slope. ...
The increased frequency of landslides and associated devastations necessitates developing sustainable mitigation measures. The present paper aims to appraise the research developments in enhancing slope stability using anti-slide piles for landslide mitigation. The previous researchers made an immense effort to identify the soil–structure interaction of the anti-slide pile. The soil arching between the piles was identified as the soil–pile interaction mechanism. A detailed review of the soil arching between the piles is performed, and the observations are presented in detail. Recently, different sustainable methods for the analysis and design of anti-slide piles have been developed. An attempt was made to carry out a comprehensive review of the analysis methods and their critical features, and the observations are provided. The parameters affecting the performance of the anti-slide piles were identified, and the influence of those parameters on the behavior of piles is also discussed. Finally, the novel designs developed by researchers to overcome the limitations of conventional anti-slide piles and the utilization of sustainable materials as anti-slide piles were appreciated. The authors like to highlight that anti-slide piles are an effective solution for landslide risk reduction, and there is further scope for research in this field.
... Sommer 1977;Fukuoka 1977;Reese et al. 1992;Poulos 1995;Smethrust and Powrie 2007). Different methods have been proposed to evaluate the performance and design of reinforcing piles in slopes, as well as to evaluate the safety factor of a reinforced slope (Ito et al. 1979(Ito et al. , 1981(Ito et al. , 1982Chow 1996, Hassiotis et al. 1997, Cai and Ugai 2000Ausilio et al. 2001;Jeong et al. 2003, Won et al. 2005, Wei and Cheng 2009, Ellis et al. 2010, Yamin and Liang 2010Kourkoulis et al. 2011Kourkoulis et al. , 2012; Ashour and Ardalan 2012; Galli et al. 2017;Di Laora and Fioravante 2018). However a widely accepted design procedure is still lacking (Di Laora et al. 2017). ...
The paper analyses the behavior of a rigid passive pile embedded in a soil profile consisting of a stable layer underlying an unstable layer subjected to a uniform soil displacement. Pile-soil interaction is considered by modeling the soil by a series of elastic–plastic springs along the pile shaft. The modulus of horizontal subgrade reaction is assumed to linearly increase with depth in the unstable layer and constant in the stable one. The ultimate soil resistance is assumed increasing with depth in both layers. The results of analysis are presented in dimensionless form in terms of shear force developed at the slip surface as a function of the pile embedment into the stable layer and the distribution of soil characteristics over depth. The method allows capturing pile response not only at the soil ultimate state but also at the intermediate states. Specifically, the governing equations for the elastic, elastic–plastic and plastic cases are discussed and, whenever possible, a set of closed-form expressions is provided to estimate the maximum bending moment along the shaft and the pile head deflection, so that for an assigned value of the required stabilizing force both ultimate and serviceability limit state of the pile can be checked. A numerical example is given to illustrate the application of the proposed procedure.
... The figure shows a set of shallow failure surfaces that covers a sliding mass of approximately 326 tons. The critical failure starts 1 m (3.28 ft) from the crest of the slope edge [A], and it corresponds to a compound failure (Ausilio et al., 2001) that curves at both ends and has a level or flat central point. The failures finish at the canal bottom 1.5 m underneath and 3 m to the left of the slope toe [B]. ...
... Anti-sliding pile is a widely used reinforcement to enhance the stability of earth slopes, due to its advantages of strong stabilization and small disturbance to the original equilibrium of slopes (Ausilio et al., 2001;Li et al., 2006;Nian et al., 2008;Abdelaziz et al., 2017). Early investigation of pile-reinforced slope stability was resorted to the deterministic approaches, in which a global factor of safety F s is calculated by fixed representative values of soil or pile parameters. ...
Stabilization pile is a common measurement for landslide mitigation. In previous literatures, the deterministic safety factor F s method has been well established for pile-reinforced slope stability analysis, for example by limit analysis. However, the F s method by itself cannot reflect the inherent uncertainty and spatial variability of mechanical properties of soil. This paper presents a probabilistic analysis procedure for width-constrained pile-reinforced slope where the failure pattern and soil spatial variability are both accounted for under three-dimensional (3D) condition. A modified discretization kinematic analysis-based mechanism is employed as the deterministic model. The spatial variability of cohesion c and friction angle φ is modeled as lognormal random fields by using the Karhunen-Loève expansion. The sparse polynomial chaos expansion (SPCE) is used to construct the meta-model to reduce the computational cost in high dimensional stochastic problems. The failure probability, probability density function (PDF), and other useful reliability results can be provided by performing Monte Carlo simulations of the proposed SPCE meta-model. Finally, the influences of soil spatial variability, slope geometry, and pile parameters on the slope reliability are analyzed. The combination of the modified dis-cretization mechanism and SPCE provides a useful tool for the probabilistic analysis of pile-reinforced earth slopes under 3D condition. The probabilistic simulation results are also helpful for reliability design of pile-reinforced slope in practice.
... In landslide control, three main methods have been adopted: Unloading by modifying the ground surface geometry, draining by constructing surface and subsurface drainage facilities (Godt et al., 2009;Chen et al., 2021a;Medina et al., 2021;Fang et al., 2023), and resisting by installing continuous or discrete retaining structures, such as walls or anti-slide piles (Hassiotis et al., 1997;Ausilio et al., 2001;Chen et al., 2020;Liu et al., 2021). Anti-slide piles offer many advantages in practical applications (Wang and Zhang, 2014;Al-Defae and Knappett, 2015). ...
The anti-slide pile is one of the most used measures in landslide control globally. Following its application, various structures have been developed. In this paper, we analyze the anti-slide pile structure development process and extract two development paths. One path is aimed at improving the applicability. The second path starts from an in-depth study of pile–soil interactions. However, these two paths share a single design concept: The anti-slide pile provides direct resistance to maintain landslide stability, that is, the anti-slide pile and the landslide body are thought to be confrontational sides. We here propose developing and utilizing the landslide body in anti-slide pile design. Accordingly, the confrontation relationship between the anti-slide pile and the landslide body can be changed while shifting away from the view that the landslide body is only a hazard. On this basis, we also design a novel structure: An arm-stretching-type anti-slide pile. The simulation verification results show that this novel structure works well in realizing the proposed design concept. Compared with the commonly used wholly buried pile, the safety factor of the landslide controlled by the novel structure is improved by 43.56%. This study promotes the design concept of anti-slide pile developing from the existing slide–resist single mode to the slide–self-stabilize–resist compound mode.
... In the FELA method (Kumar and Chakraborty 2013), only the ultimate failure mechanism and corresponding factor of safety would be demonstrated, and the absolute internal force and deformation during the intermediate process would not be obtained. It differs from other conventional methods, e.g., the limit equilibrium method (Poulos 1995;Hassiotis et al. 1997), limit analysis method (Ausilio et al. 2001;Nian et al. 2008;Li et al. 2012), and finite difference method (Ni et al. 2018). As to cases of seismic loading (Lin and Wang 2006;Yan et al. 2020;Huang et al. 2020), the pseudo-static method is widely accepted because of the definite physical significance and simple parameter determination in comparison to Newmark's method and ground response analysis method. ...
... This study is presented to evaluate the seismic stability of SCTPF by FELA, and the seismic loading has been modeled as a statically applied inertial force, the magnitude of which is a product of a seismic coefficient and the weight of the potential sliding mass. First, the FELA method is successively validated by the cases of a slope containing a laterally loaded single pile , portal pilereinforced slope under static conditions (Zhao et al. 2017), and common pile-reinforced slope under seismic conditions (Ausilio et al. 2001;Nian et al. 2016;Li et al. 2016). Subsequently, the effects of various factors (inc. ...
... There is no proper example case that can be exactly adopted for direct validation of the application of the FELA method in the analysis of the seismic stability of SCTPF. Consequently, only a stepwise validation can be accomplished by three types of degenerated cases: (i) static loading case with a laterally loaded single pile ); (ii) static loading case with portal piles (or h-type piles) (Zhao et al. 2017); and (iii) seismic loading cases with and without antislide piles (Ausilio et al. 2001;Nian et al. 2016;Li et al. 2016). Undoubtedly, shear strength parameters were varied in these three recorded cases. ...
In this study, the seismic stability of the slope containing a two-pile foundation (SCTPF) under seismic loads is evaluated by the finite element limit analysis (FELA) method. The seismic loading is modeled as a statically applied inertial force, the magnitude of which is a product of a seismic coefficient and the weight of the potential sliding mass within the framework of the pseudo-static method. The feasibility of FELA in the analysis is validated by comparing the predicted safety factors, yield acceleration coefficients, and potential failure surfaces with those in published studies. On this basis, some non-dimensional multipliers are presented to investigate the variations of seismic safety factors with different factors and simplify the calculation of seismic safety factors. Numerous values of the multipliers under different conditions have been given in this study and the tendency of these multipliers with different factors has been explored by fitting curves or distribution regions. Furthermore, four detailed design tables for seismic safety factors and six representative slope failure modes are presented, with the mechanisms and conditions of these failure modes and the transitions among them elaborated.
... The soil arch between the pile backs governs the soil arching effect in pile soil interactions which has been proven directly through laboratory tests and practical engineering phenomena [10]. Ausilio et al. (2001) [12] developed a methodology for the stability of slopes reinforced with piles using the kinematic approach of limit analysis. ...
... The soil arch between the pile backs governs the soil arching effect in pile soil interactions which has been proven directly through laboratory tests and practical engineering phenomena [10]. Ausilio et al. (2001) [12] developed a methodology for the stability of slopes reinforced with piles using the kinematic approach of limit analysis. ...
... By considering the limit equilibrium method, Poulos (1995) [15] suggested that piles should be located in the vicinity of the centre of the critical failure wedge to avoid merely relocating the failure surface behind or in front of the piles. According to Ausilio et al. (2001) [12] the optimal location of the piles within the slope is near the toe of the slope where the stabilizing force needed to increase the safety factor to the desired value takes a minimum value. They also found out that piles also appear to be very effective when they are installed in the region from the middle to the toe of the slope. ...
Anti-slide piles are widely used as a reinforcement technique for stabilizing slopes as part of landslide mitigation. The interaction between the anti-slide piles and sliding soil mass is best explained using the soil arching effect. The analysis of slopes stabilized with anti-slide piles can be carried out using either an uncoupled or a coupled approach. In the uncoupled approach the limiting soil pressure is obtained using an analytical, empirical, or numerical method, and this limiting soil pressure is used as an additional resistance in slope stability analysis. On the other hand, coupled analysis utilizes powerful numerical tools like 2D and 3D finite element analyses where both the pile response and slope stability are considered simultaneously. The safety and economy of anti-slide piles depend on the critical spacing and position of anti-slide piles. This article presents a detailed review of the anti-slide pile-soil interaction, the design mechanism , analysis of slope stabilized with anti-slide piles, and the parameters influencing the response of piles. The excellent landslides resistance offered by the anti-slide piles urges researchers to pay more attention to this field. .
... For more than three decades, piles in single or multiple rows were used effectively to prevent collapses and increase the slope's stability (Wei and Cheng 2009;Nian et al. 2008;Guo 2013). Across many cases, using piles to stabilize slopes or increase slope stability has been widely accepted (Ausilio et al. 2001). By interconnecting the sliding mass with stronger and more stable layers beneath, the pile's bending resistance is used for stabilization. ...
... In terms of research, the static stability of slopes reinforced with piles has been previously investigated via laboratory experiments (Tang et al. 2014;Xiao et al. 2017;Hajiazizi et al. 2018;Lei et al. 2019), field investigations (Lirer 2012;Xiang et al. 2015;Galli and Bassani 2018), and numerical analyses (Kourkoulis et al. 2011(Kourkoulis et al. , 2012Shukla 2012, 2014;Ho 2015Ho , 2017Kontoe et al. 2018;Pirone and Urciuoli 2018;Lee et al. 1995;Xiao et al. 2017;Ausilio et al. 2001;Gao et al. 2015;Rao et al. 2017). However, there are very limited studies which have considered the effect of using piles on the slope stability in seismic conditions (Nian et al. 2016;Bharathi et al. 2018). ...
A slope may fail as a result of overstress or a decrease in the soil’s shear strength. Piles in single or multiple rows have been widely used as earth retaining systems to stabilize active landslides and improve the slope stability. However, limited studies are available on the effect of pile stabilization on the seismic stability of slopes. Therefore, this study presents two-dimensional and three-dimensional finite element analyses based on the strength reduction technique to investigate the seismic response of slopes stabilized using piles. The effect of the length and configuration of the piles on the stability of the slopes is examined, where five configurations are considered. These configurations are single pile, two piles distributed in one row, four piles distributed in one row, four piles distributed in two rows, and eight piles distributed in two rows. These cases have been compared with a reference case of an unreinforced slope in both dry and saturated conditions. It was found that the number of piles has a remarkable influence on the mobilized factor of safety, and its influence is higher than the pile length. In addition, using the piles in two rows increases the safety compared to using the same number of piles but in one row. Furthermore, the slope yielded a higher factor of safety in the dry cases compared to the saturated cases. More importantly, it was found that the earthquake remarkably affected the mobilized factor of safety of the slope, and thus, the real intensity of the earthquake should be utilized in the assessment and design of slopes. The results presented in this paper are useful to engineers working on the stabilization, assessment, and design of slopes in areas prone to earthquakes.
