Applicatio of Soil Structure Interaction in the analysis of flexible retaining wall
- 1. Delhi Technological University Department of civil engineering Application of Soil-Structure Interaction (SSI) in The Analysis of Flexible Retaining Walls
- 2. ABSTRACT One of the most important features of flexible retaining walls is that wall deformations highly influence the distribution of earth pressures on the wall. The deflection of flexible retaining walls is controlled by the flexural rigidity of the wall and the soil pressure generated based on the permissible movement of the wall. The conventional method of design for flexible retaining walls is based on a limit equilibrium theory that searches the force equilibrium by assuming the soils engaged around the wall are all in the limit state.
- 3. INTRODUCTION • Soil–structure interaction (SSI) consists of the interaction between soil (ground) and a structure built upon it. • It is primarily an exchange of mutual stress, whereby the movement of the ground- structure system is influenced by both the type of ground and the type of structure. • Flexible retaining structures have received much attention since 1940 because of their widespread use in engineering construction. • Flexible retaining walls, usually have a single row of piles, likely made of timber, reinforced concrete, or sheet steel, driven so that their lower ends are embedded in soil. • One of the most important features of flexible retaining walls is that wall deformations highly influence the distribution of earth pressures on the wall.
- 4. LITERATURE REVIEW • Franza et al. (2021) The response of pile groups and piled structures to vertical and tunnelling- induced loads is studied. Several scenarios are analysed: namely, piles subjected to vertical loads; piles and piled structures that are affected by tunnelling induced ground movements. It is found that the action of slabs and stiff superstructures decreases the distortions of the structure above ground, whereas it likely increases the foundation distress due to tunnelling. • Deepashree et al. (2020) In the current study structure is analysed without SSI and also the behaviour of the structure is studied by considering SSI effect using spring elements. The time period in the hard soil is lesser when compared to the other two medium of soil and is highest for soft soil under SSI effect. The maximum displacement is seen in soft soil than other soil types in both the cases such as with SSI and without SSI system and it is maximum for SSI system.
- 5. • Lin et al. (2014) In this research a fully instrumented experiment was conducted to investigate the soil-structure interaction of single short, stiff laterally loaded piles. A hollow steel pipe pile with a diameter of 102 mm, a thickness of 6.4 mm, and a length of 1.524 m was installed in well-graded sand and subjected to increasing lateral load. The measurement-based p-y curves at different depths along the pile length showed nonlinear behavior, with the initial slope (initial stiffness) and ultimate soil reaction increasing as the depth increased. • Suleiman et al. (2014) The soil-structure interaction of piles used to stabilize failing slopes (i.e., subjected to lateral soil movement known as passive piles) was experimentally investigated using a state-of-the-art soil-structure interaction facility. The soil-pile interaction pressure measurements above the sliding surface indicate that the pressure exerted on the pile by the moving soil increased as the soil movement increased, and that the soil pressure increased linearly along the pile within the moving soil.
- 6. • Wang et al. (2013) This paper will discuss the modifications of p-y curves that are needed to take into account the configuration of the wall system (group effects), the unsymmetrical driving forces in the backfill side, the soil resistance in the penetration side, and the long- term effect from the sustained load. The results show that the p-y Curve method for design of anchored sheet-pile wall is rational and can also be adaptable for seismic conditions. • Chen et al. (2010) This paper presents the development of project-specific p-y curves for the analysis and design of tangent and secant pile walls in the Marquette Interchange Project. Site-specific and project-specific p-y curves were successfully developed from PMTs for the Marquette Interchange Project. As such, the procedure presented herein is proven to work in full scale.
- 7. • Suleiman et al. (2010) This research focuses on measuring the soil-pile interaction pressure for a laterally loaded pile. The paper also describes the installation procedure, the soil properties, the measured pile force-displacement relationship and the measured strain along the length of the pile. The soil-pile interaction pressure was successfully measured and the location of the maximum pressure ranged from 47.2 cm and 56.6 cm, which is influenced by the free soil surface and the relative stiffness between the pile and the soil. • Dicleli et al. (2005) In this paper, the effect of soil–structure interaction on the seismic performance of seismic-isolated bridges is studied. The analyses results have revealed that soil–structure interaction effects may be neglected in the seismic analysis of seismic-isolated bridges with heavy superstructure and light substructure constructed on stiff soil.
- 8. • Masia (2004) A soil/structure interaction model for the simulation of the structural response, including wall cracking, of lightweight masonry structures to expansive soil movements is described. The simulation of swell and shrink in expansive soils due to changes in soil suction is discussed. The model is capable of reproducing the essential features of the structural response observed in full scale experiments. Simple modeling assumptions and the use of static condensation of the global stiffness equations allow fast solution speeds to be achieved. • Chaudhary et al. (2001) In this research, using a two-stage system identification methodology for non-classically damped systems, modal and structural parameters of four base-isolated bridges are reliably identified using acceleration data recorded during 18 earthquakes. Soil– structure interaction (SSI) effect in these bridges is examined by comparing the identified and physical stiffness of the sub-structure components. It is found that SSI is relatively pronounced in bridges founded in weaker soils and is more strongly related to the ratio of pier flexural stiffness and horizontal foundation stiffness.
- 9. OBJECTIVES • To analyse the deformation of the structural system based on mobilised earth pressure and soil resistance along the wall. • To use non linear p-y curve for modelling the passive resistance of soils due to lateral deformation of embedded wall section. • To analyse group affect on pile
- 10. MATERIAL AND METHODOLOGY AVAILABLE METHODS OF DESIGN AND ANALYSIS FOR FLEXIBLE RETAINING STRUCTURES 1. Limit-equilibrium analysis (classical design method), 2. Sub-grade reaction method, 3. Finite-element method 4. Nonlinear py curve method.
- 11. LIMIT-EQUILIBRIUM ANALYSIS (CLASSICAL DESIGN METHOD) • The classical soil mechanics procedures based on the active and the passive earth pressure in the limit state have been used in the past for determining the required depth of penetration and factor of safety, extensively for sheet-pile walls. • It is no doubt that the success of design by using the classical method has been achieved and recognized in the engineering practice. • The limit-equilibrium analysis does not take into account the nonlinear mobilization of soil reaction with wall deflection in the analysis.
- 12. SUB-GRADE REACTION METHOD • The subgrade reaction is the resistance from peripheral ground layers. It is a reaction force which depends on the ground displacement. • The subgrade method takes into account the soil-structure interaction based on the assumption of soils with linear-elastic behavior. • This model will not realistically capture the ultimate (or yield) soil resistance.
- 13. FINITE-ELEMENT METHOD • The use of finite-element methods has allowed attempts at a complete solution of retaining-wall problems, including the computation of stresses and deformations in both the wall and the adjoining soil. • The finite-element method shows promise in handling the complicated stress- strain relationship for the retaining system. Although the finite-element analysis has been developed far enough to be used for design purposes • it requires soil parameters from sophisticated laboratory tests, significant engineer’s time in preparation of the model, and devoted efforts in interpreting the computed results. Even with such high demanding factors, some interesting problems have been solved by using this complicated method.
- 14. NONLINEAR P-Y CURVE METHOD • Recently, the method of analysis for beams or piles on nonlinear foundations employs the soil response curves derived from full-scale experiments and has been accepted as a rational design method by many engineers. • The method commonly is referred to as the p-y method and has been successful in aiding the design of laterally loaded piles. • Many researches and field loading tests have been performed in the past 40 years worldwide to provide guidance on how to estimate the nonlinear soil resistance (p) versus the pile deflection (y) for a board range of soil and rock formations.
- 15. DIFFERENCE BETWEEN THE OLD AND NEW APPROACHES CLASSICAL SOIL MECHANICS PROCEDURE • Based on the active and the passive earth pressure in the limit state. • To determine depth of penetration and factor of safety, extensively for sheet-pile walls METHODS BASED ON SOIL STRUCTURE INTERACTION • provide better capabilities in handling complex nonlinear soil behavior in multi-layers formation • Helps in analyzing the deformation of the system based on the mobilized soil resistance along the wall
- 16. RESULTS AND DISCUSSION • The numerical model for the SSI method is based on the so-called “Winkler” foundation, where the active earth pressure is considered as external loads and the soil below the excavation level is modeled by a series of nonlinear p-y springs to provide passive resistance (Figure 1). • The active earth pressure above the excavation level should take into account. Wa is the center to center spacing for a pile-wall system and Wp is the unit width (equivalent diameter) for representing the structural member in the analysis model.
- 17. Source: https://doi.org/10.1061/9780784413128.067 The p-y curves below the excavation level become unsymmetrical, which usually indicates that the soil resistance at the backfill side is much higher than those in the excavation side.
- 18. • The p-y curves (soil resistance) will be calculated based on the width of the wall (as the equivalent pile diameter), Wp. • The reduction of soil resistance (p value) due to group effect should be considered in the analysis, especially for sheet-pile and soldier-pile walls. • It should be noted that the depth or overburden pressure is a factor in calculation of p-y curves. The overburden pressure on the backfill side is much greater than the excavation side at the same depth.
- 19. The p-y curves had a general trend of increased initial slope (initial stiffness) and ultimate soil reaction as the depth increased. However, the initial slope at 315 mm was larger than that at 525 mm, which may be attributed to small pressure-measurement errors and to the presence of angular- shaped sand particles. Fig. 2 Measured soil-pile interaction force-displacement relationship(p-y curves) at several depths along the pile length Source: https://doi.org/10.1061/9780784413128.067
- 20. Reduction Factors for Piles in a Row • When piles are in a closely-spaced group with substantial interaction, the shear- failure planes resulting from the movement of each pile will overlap, and the ultimate resistance for piles in a group may be less than that accumulated from a single pile. • A modification factor similar to those recommended by Brown et al. (1987), is needed to reduce the soil resistance for piles in a row without spacing (such as sheet- pile walls) or with a very close spacing (such as drilled-shaft walls).
- 21. Source: https://doi.org/10.1061/9780784413128.067 •Reese and Van Impe (2001) have reviewed experimental data on side-by-side piles shown in Figure 3. •They suggest that the outer pile should carry slightly more load than the interior piles.
- 22. CONCLUSION • The p-y curve method was developed based on the commonly-recognized structural theory. With the p-y curve method, both equilibrium and compatibility are automatically satisfied when the solution converges. • The distribution of the soil pressure and soil resistance is rational based on the p-y curve method. Engineers can receive the information, such as the deformation profile.. • The reduction of soil resistance (P value) due to group affect should be considered in the analysis.
- 23. REFERENCES • Brown, D. A., Reese, L.C., and O’Neill, M.W., (1987) “Cyclic Lateral Loading of a Large- ScalePileGroup,”Journal of the Geotechnical Engineering Division, American Society of Civil Engineers, Vol. 113, No. 11. • Chen, J., Farouz, E., and Landers, P. (2010) “Development of Project-Specific p-y Curves for Drilled Shaft Retaining Wall Design,” Proceedings of Earth Retention Conference 3, ASCE, Bellevue, Washington, pp. 162-169. • Reese, L. C. and Welch, R.C., (1975) “Lateral Loading of Deep Foundations in Stiff Clay,”Journal of the Geotechnical Engineering Division, American Society of Civil Engineers, Vol. 101, No. GT7, pp. 633-649. • Clough,G.W.andDuncan,J.M., (1971) “Finite element analysis of retaining wall behavior”. Journal of Soil Mechanics and Foundation Engineering Division, ASCE, 97(12): 1657-1673. • Desai,C.S.,Drumm,E.C.andZaman,M.M., (1985) “Cyclic testing and modeling of interface”. Journal of Geotechnical engineering, ASCE, 111(6): 793-815.
- 24. • Matlock, H. (1970) “Correlations for Design of Laterally Loaded Piles in Soft Clay,” Proceedings, Offshore Technology Conference, Houston, Texas, Vol. I, Paper No. 1204, pp. 577-594. • Mononobe, N. and Matsuo, M., (1929) “On the Determination of Earth Pressures DuringEarthquakes,”Proceedings, World engineering Conference, Vol.9., pp.176. • National Cooperative Highway Research Program (NCHRP), (2008), Seismic Analysis and Design of Retaining Walls, Buried Structures, Slopes, and Embankments, Report 611, Transportation Research Board of the National Academies, Washington, D.C. • Reese, L. C., Cox, W.R., and Koop, F.D., (1974) “Analysis of Laterally Loaded Piles in Sand,” Proceedings, Offshore Technology Conference, Houston, Texas, Vol. II, Paper No. 2080, pp. 473-484. • Reese, L. C., Cox, W.R., and Koop, F.D., (1975) “Field Testing and Analysis of LaterallyLoadedPilesinStiff Clay,” Proceedings, Offshore Technology Conference, Houston, Texas, Paper No. 2312, pp. 671-690.