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- 1. DESIGN AND ANALYSISOF MSE WALL AT ROB KOTTAYAM Presented by: Guided By: Sruthi Raj pk. Prof. Anil Kumar PS Roll no: 07
- 2. • Design andanalysis of Mechanically stabilized earth retaining wall of ROB Kottayam. Using MSEW Software. • Provided Initial height of the wall 7m with modular concrete panel facing • Follows FHWA-NHI-10-024 Design guidelines • External stability check - Direct sliding, Bearing Capacity and Eccentricity can be assessed using Ka based on Coulomb’s lateral earth pressure. • Internal stability check – Pull out resistance, connection strength, Reinforcement tension resistance. INTRODUCTION
- 3. LITERATURE REVIEW Author Year of publicati on Journalname Description 1.Joseph E Bowler 1988 Foundation analysis and design • The mechanically reinforced earth wall uses the principle of placing reinforcing into the backfill using devices such as metal strips and rods, geotextile strips and sheets and grids, or wire grids • Basic 3 components of a reinforced retaining wall is earth fill, facing unit and Reinforcement 2.Christopher Barry R. 2009 Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes – Volume I:FHWA-NH-10-024 • Mechanically Stabilized Earth Walls (MSEWs) and Reinforced Slopes (RSSs) are cost effective soil-retaining structures that can tolerate much larger settlements than reinforced • placing tensile reinforcing elements (inclusions) in the soil, the strength of the soil can be improved significantly. • Use of a facing system to prevent soil raveling between the reinforcing elements allows very steep slopes and vertical walls to be constructed safely.
- 4. Author Year of publicati on Journal nameDescription 3.Armin stuedlein 2010 Design and Performance of a 46-m- High MSE wall • Geotechnical instrumentation, including wall surveys, inclinometer installations with sondex settlement rings, piezometers, and strain gages on reinforcing strips, provides information required to verify performance of the wall relative to design • Selected steel strip reinforcement in order to limit and extend embankment fill . 4.Michael Dobie 2013 Reinforced Soil Retaining Walls – An Outline of Design Methods and Sources of Conservatism • Conservatism can be reduced by using a method of calculation for internal stability which models likely modes of failure as closely as possible, and requires as few assumptions as possible to make the calculation. • Soil tests are required to define the fill shear strength and unit weight
- 5. Author Year of publicati on Journal nameDescription 5.Haresh D Golakiya 2015 Design and behaviour of Mechanically stabilized earth wall • Angle of internal friction Ø is the most important of all other parameters as the basic principal of mechanically stabilization of earth depends on it. • Length of reinforcement layers increases as height of wall increases. Design strength of reinforcement and vertical spacing between two reinforcements are also main factors 6.Richard J Bathurst 2016 The influence of facing stiffness on the performance of two geosynthetic reinforced soil retaining walls • Stiff facing in a reinforced soil wall is a structural component that can lead to significant reductions in reinforcement loads compared to flexible facing systems. 7.Soroush Nazarin 2017 Estimation of Maximum Lateral Displacement of the Back to Back Mechanically Stabilized Earth Walls • Back to back mechanically stabilized earth walls (MSEWs) are the structures usually used in two sides of bridge abutments and ramps
- 6. Author Year of publicati on Journal nameDescription 8.Ratnesh ojha 2021 Study of Geosynthetic Reinforced Retaining Wall under Various Loading • Reinforcement in the soil can be used to enhance the behavior of retaining walls under seismic loading in terms of improved overall stability of the structure. • In Case of high retaining wall, tiered walls are preferred over a single height retaining wall due to their cost-effectiveness 9.Haitham H. Muteb 2021 Mechanically Stabilized Earth MSE Walls Applications • Reinforcing structure and the facing units serve as a supporting system • The MSE approach is used to solve the infrastructure problems that are faced in transportation programs. 10. Hariprasad chennarupa 2022 The analysis and design of MSE wall by considering variation of friction angle of backfill material along the depth • (MSE)structures are done by using various types of reinforcements (coir fiber, metal strips, and geosynthetic materials). • Angle of shearing resistance between reinforcement and backfill plays an significant role in the stability and serviceability of MSE walls.
- 7. MECHANICALLY STABILIZED EARTHWALL • A Mechanically Stabilized Earth (MSE) retaining wall is a composite structure consisting of alternating layers of compacted backfill and soil reinforcement elements, fixed to a wall facing. • The stability of the wall system is derived from the interaction between the backfill and soil reinforcements, involving friction and tension. • The wall facing is relatively thin, with the primary function of preventing erosion of the structural backfill. The result is a coherent gravity structure that is flexible and can carry a variety of heavy loads.
- 8. • Benefits ofMSE Walls: • Flexibility to accommodate high differential settlement and several feet of total settlement • Bearing pressure is distributed over a wide foundation area • Extreme wall heights can be achieved • Extreme loads can be carried (bridge abutment footings, cranes) • High resistance to seismic ground movement and other dynamic forces • Free-draining, due to granular backfill and open panel joints
- 9. MSEW SOFTWARE • ProgramMSEW+ is an interactive, graphically rich program, allowing the user to easily explore various design options or conduct forensic analysis. • Use of MSEW+ must be licensed. This device is provided with the software and it constitutes a license. • It enables the designer to conduct comprehensive analysis, including internal, external and global stability.
- 10. METHODOLOGY Evaluation of testresults and bore log data Design of MSE wall External and Internal stability analysis in MSEW Software
- 11. FIELD INVESTIGATION • Theproposed site was situated at caritus Kottayam district • The program of soil investigation consisting boring which was carried out to a depth of 22.3 m • Borehole was terminated at a depth of 22.3m
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- 14. CODAL PROVISIONS IRC 116-2018 Basewidth 0.6 to 0.75H ( For height 1 to 6m ) 0.55 to 0.65H (above 6 to 10m) Batter angle 3° to 6° with vertical angle IRC SP 102 2014 Min length 0.75H or 3m
- 15. DESIGN OF MSEWALL 1. DESIGN WALL GEOMETRY Design is carried out as per FHWA ,IRC 116:2018 , IRC SP 102:2014 Height of the wall ,H = 8m Wall batter , 𝜔 =4° Back slope of the wall , 𝛽=0 (Horizontal backslope) Assuming length of reinforcement =7 m (Min length =0.7H or 3m)
- 16. 2. ENGINEERING PROPERTIESOF SOIL 𝜸(𝑲𝑵/𝒎𝟑) ∅( 𝑫𝒆𝒈𝒓𝒆𝒆) C(𝑲𝑵/𝒎𝟐) Reinforced soil 20 34 0 Retained soil 18 30 0 Foundation soil 20 34 0
- 17. L = 6m H = 7m
- 18. 3. DESIGN LOAD Deadload , 𝑞𝐷 = 12 KPa Live load , 𝑞𝐿 = 24 Kpa 4. COEFFICIENTS OF LATERAL EARTH PRESSURES Coefficient of Active earth pressure of reinforced soil, 𝑘𝑟 = 𝑡𝑎𝑛2 (45- 34 2 )=0.282 Coefficient of Active earth pressure of retained soil , 𝑘𝑎𝑏 = 𝑡𝑎𝑛2(45- 30 2 )= 0.333
- 19. 5. EXTERNAL STABILITYANALYSIS Check for Sliding Sliding force , Fs = 0.5 𝑘𝑎𝑏* 𝛾* 𝐻2 + 𝑘𝑎𝑏* (𝑞𝐷 + 𝑞𝐿 )* H = 287 KN/m 𝜇 = tan(2 3 ∗ 30)=0.364 Resisting force , 𝐹𝑟=𝜇 { (𝛾*H*L) +(𝑞𝐷 *L)} = 439 KN/m Factor of safety against sliding = 𝐹𝑟 𝐹𝑠 =1.53> 1.5 Hence safe
- 20. Check foroverturning Overturing moment , 𝑀0 = 0.5 𝑘𝑎𝑏* 𝛾* 𝐻2 ∗ ( 𝐻 3 )+ 𝑘𝑎𝑏* (𝑞𝐷 + 𝑞𝐿 )* H*(H/2) = 895 KN-m/m Resisting moment, 𝑀𝑟 = 𝛾*H*L* 𝐿 2 +𝑞𝐷 *L* 𝐿 2 = 4214 KN-m/m Factor of safety against overturing = 𝑀𝑟 𝑀0 =4.7 > 2 Hence safe
- 21. Check forBearing capacity 𝑅𝑣 = 𝛾∗H∗L + (𝑞𝐷 + 𝑞𝐿 )* L = 1372 KN/m e = 𝑀0 𝑅𝑣 = 0.65 < 𝐿 6=1.16 Hence safe 𝜎𝑉𝐵 = 𝑅𝑣 𝐿−2𝑒 = 241 𝐾𝑁/𝑚2 Allowable bearing capacity was found out by using Meyerhof’s by considering the foundation as strip footing. For the MSE wall the shape factor, depth factor, and inclination factor are taken as unity. Considering general shear failure. C=0
- 22. As per IS6403: 1981 As per Table 1 bearing capacity factor of IS 6403: 1981 For ɸ = 34° 𝑁𝑞 = 30.32, 𝑁𝛾 = 42.90 W’=0.5 (Water table at the base) B=L-2e =6.7m Ultimate bearing capacity , = 𝐶𝑁𝑐+ 𝛾 𝐷𝑓 𝑁𝑞+ 0.5 𝛾 𝐵𝑁𝛾 W’ = 2043 𝐾𝑁/𝑚2 Net safe bearing capacity , 𝑄𝑛𝑠 = 𝑄𝑢 2.5 = 817.2 𝐾𝑁/𝑚2 𝜎𝑉𝐵 < Hence safe 𝑄𝑢
- 23. 4. Seismic ExternalStability Analysis As per IS 1893-2002 Seismic zone: III and Zone Factor, Z = 0.16 Importance Factor, I = 1.5 (Table 6) Response reduction factor, R = 3 (Table 7) Spectral acceleration coefficient, 𝑆𝑎 𝑔 = 1 from chart Base Acceleration, α = 𝑍𝐼 2𝑅 𝑆𝑎 𝑔 = 0.04 Average accelaration coefficient of soil as per FHWA α𝑚 =(1.45 – α)*α = 0.0564 Lateral thrust from backfill , 𝑃𝐴𝐸 = 0.375∗ α𝑚 * 𝛾 *𝐻2 = 24 KN/m acts at 0.6H from base
- 24. Ineria force ofthe soil in RE block due to self weight , 𝑃𝐼𝑅 = 0.5∗ α𝑚 * 𝛾 *𝐻2 =36.09 KN/m acts at 0.5H from base. Total seismic force , 𝑃𝑇 = 0.5𝑃𝐴𝐸 + 𝑃𝐼𝑅 = 60.59 KN/m Check for sliding Total lateral force , Fs = Total seismic +sliding force =60.59+ 287 =347.59KN/m Resisting force , 𝐹𝑟 = 439 KN/m Factor of safety against sliding = 𝐹𝑟 𝐹𝑠 = 1.27 > 75% of 1.5 = 1.12
- 25. Check foroverturning Overturning moment , 𝑀0 = 895+ 𝑃𝐼𝑅*0.5H+ 𝑃𝐴𝐸 ∗ 0.65𝐻 = 1164 KN-m/m Resisting moment , 𝑀𝑟 = 4214 KN-m/m Factor of safety against overturning = 𝑀𝑟 𝑀0 =3.6 > 75% of 2 = 1.125 Hence safe Check for bearing capacity 𝑅𝑣 = 1372 KN/m e = 𝑀0 𝑅𝑣 = 0.84 < 𝐿 6=1.16 Hence safe 𝜎𝑉𝐵 = 𝑅𝑣 𝐿−2𝑒 = 258 KN/𝑚2 𝜎𝑉𝐵 < Hence safe
- 26. 6. INTERNAL STABILITYANALYSIS The facing of the MSE wall is a gabion structure. The thickness of the gabion unit is 0.8. That is the vertical spacing of the reinforcement layer is taken as 0.8m . Geogrid is selected as the reinforcement and the ultimate tensile strength of the geogrid is 150 KN/m. 𝑅𝐹𝐼𝐷= 1.3 (Table 3-9. Installation Damage Reduction Factors, FHWA) 𝑅𝐹𝐶𝑅 = 2 (clause 3.5.2.c Creep Reduction Factor, FHWA) 𝑅𝐹𝐷 = 1.3 (Table 3-11. Durability (Aging) Reduction Factors for PET, FHWA)
- 27. No of reinforcementlayer = 8/0.8 =10 Internal stability 𝒑𝒉 =𝛾 ∗ 𝑧 ∗ 𝑘𝐴 + 𝑞𝑠 * 𝑘𝐴 =20*z*0.282 + 36*0.282 =5.64 *z +10.152 1) For geogrid vertical spacing 𝑇𝑢 = 150 KN/m 𝑇𝑎𝑙𝑙𝑜𝑤𝑎𝑏𝑙𝑒 = 𝑇𝑈𝑙𝑡 𝑅𝐹 = 𝑇𝑈𝑙𝑡 𝑅𝐹𝐼𝐷∗𝑅𝐹𝐷∗𝑅𝐹𝐶𝑅 = 150 1.3∗2∗1.3 = 44.38 KN/m 𝑇𝑑𝑒𝑠𝑖𝑔𝑛 =31.7 KN/m
- 28. 𝑇𝑑𝑒𝑠𝑖𝑔𝑛 = ℎ ∗𝒑𝒉 𝐶𝑟 h= 25.36 5.64 ∗z +10.152 Max depth for h =1m ,z= 2.69m Max depth for h= 0.5m , z= 7.19m 2)Embedment length of geogrid layers 2𝑐𝑖𝑐𝑟𝐿𝑒𝑝0tan∅ = 𝑝ℎ h 𝐹𝑠 Le = (0.52 𝑧+0.94)ℎ 𝑧 Equation for 𝐿𝑅 = (H-z) tan (45- ∅ 2 ) = 4.25 -0.53z
- 29. From the aboverelationship the spacing of geogrid layers and their length are given below Layer no Depth (m) Spacing(h) (m) Le (m) Le (min) (m) 𝐿𝑅 (m) L (cal) (m) L(req) (m) 1 0 0 0 1 4.25 5.25 7 2 0.8 0.8 1.356 1 3.83 4.83 7 3 1.6 0.8 0.886 1 3.40 4.40 7 4 2.4 0.8 0.729 1 2.98 3.98 7 5 3.2 0.8 0.651 1 2.55 3.55 7 6 4 0.8 0.604 1 2.13 3.13 7 7 4.8 0.8 0.573 1 1.71 2.71 7 8 5.6 0.8 0.550 1 1.28 2.28 7 9 6.4 0.8 0.533 1 0.86 1.86 7 10 7.2 0.8 0.520 1 0.434 1.434 7
- 30. EXTERNAL STABILITY Checkfor sliding 𝐹𝑟 𝐹𝑠 = 1.53> 1.5 Hence safe Check for overturning 𝑀𝑟 𝑀0 = 4.7 > 2 Hence safe Check for bearing capacity e = 𝑀0 𝑅𝑣 = 0.84 < 𝐿 6=1.16 Hence safe 𝜎𝑉𝐵 = 𝑅𝑣 𝐿−2𝑒 = 258 KN/𝑚2 𝜎𝑉𝐵 < Hence safe
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- 38. REFERENCES • PC varghese‘Foundation engineering’ ,2012. • FHWA-NHI-10-024 ‘Design and Construction of Mechanically Stabilized Earth Walls and Reinforced Soil Slopes’ ,Volume I- 2009. • IS 6403 (1981): Code of practice for determination of bearing capacity of shallow foundation.
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