International Journal of Advanced Engineering Technology E-ISSN 0976-3945

Research Article ANALYSIS & DESIGN OF 44 METER M.S.E. (MECHANICALLY STABILIZED EARTH) WALL BY USING PLAXIS 8.2

1D. Kishan, 2Dr. N. Dindorkar, 3Dr. R. Srivastava, 4* Ankesh Shrivastava

Address for Correspondence

1Asst. Prof, Department of Civil Engineering, MANIT, Bhopal MP INDIA 2Professor, Department of Civil Engineering, MANIT, Bhopal MP INDIA 3Director, NIT, Jamshedpur (Jharkhand) 4Research Scholar, , Deptt. of civil Engineering, MANIT Bhopal MP INDIA E mail [email protected] ABSTRACT Mechanically Stabilized Earth (MSE) Wall has been increasingly used in many Central, state and private projects over the last 20 years. MSE walls are reliable, constructible, and cost effective. However, designing and analysis of MSE all has become a problem for many agencies using them. In this paper a Finite-Element Program PLAXIS is used to analysis and designing of 44 meter 4 tiered MSE wall. Based on the parametric studies it is observed that the top 1 st tiered wall shows the deflection of about 130mm, the total displacement of wall is about 132mm, extreme stresses on to the wall are about 29.69%, and total extreme stresses are about 973. 06 kN/m 2 to the downward direction from the top of the wall. This paper presents the results of investigations to design and analysis of 44 meter MSE wall.

1. INTRODUCTION includes precast concrete panels, dry cast modular blocks, metal sheet and plates, , is an abundant construction material, which welded wire mesh, shotcrete, wood lagging and has compressive strength and no tensile strength. panels, and wrapped sheet of . To overcome this weakness, the soil can be 2. PROBLEM STATEMENT reinforced with materials with high tensile The basic need of the infrastructure in civil strength. The basic principal of earth engineering is continuously increasing to cater reinforcement is the generation of frictional the development of nation, and it is necessary resisting force between the backfill soil and that invent new technique to minimize the use of reinforcing element. The reinforcing element cement concrete in all infrastructural projects can be geosynthetics, metal straps, strips and and generate a new environmental friendly bars etc. Mechanically stabilized earth (MSE) is technique for the construction of various civil a method of reinforcing earthen materials so that engineering structures. they can support their own weight within the Widening of in hilly , construction minimum space and maximum side slopes. MSE of embankments and foundations on soft walls are typically constructed using four with minimum utilization of land are the major structural components: 1) geogrid reinforcement issues to be addressed during planning and 2) wall facing 3) retained backfill and 4) design stages of all major projects. Therefore in reinforced backfill soil. The facing also plays an the present study the analysis and designing of important role in the stability of the wall, which 44 meters, 4 tiered MSE wall for the widening

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International Journal of Advanced Engineering Technology E-ISSN 0976-3945 of Ghat has been carried out using finite minimum vertical spacing is of 80mm and element program PLAXIS 8.2. maximum spacing is of 280mm. this spacing is 3. OBJECTIVE OF STUDY determined by the relevant books and codes. A The main objective of the current study is to ‘IRC CLASS-A’ loading was applied as a determine the alternate method for construction moving load on to the wall considering as a of highway roads in hilly areas. The major tasks worth condition for the movement of the performed in this study are as follows vehicles to the wall. a 300mm × 300mm vertical 1. To study the fundamental principal and chimney is to be design at the facing side of the further development of reinforced wall for the proper drainage of the runoff water. structures to achive economical designing of the wall. 2. Perform the parametric studies of the various factors that may govern the important parameters of MSE wall like a) The effects of reinforcement. b) The effects of backfill soil. c) The final objective is to compare the total displacement, stresses, strains and axial forces developed in the reinforcing layers as as in soil. 4. DISCRIPTION OF TIERED WALLS The MSE wall consists of 4 tiered walls each of 11meter height, with effective length of reinforcing layer at 1 st tiered wall from the bottom is of 20meter, 2 nd tiered having 15meter, 3rd tiered having 12meter and top 4 th having 10 meters respectively. The total numbers of reinforcing layers are 28, in which each tiered wall heaving 7 reinforcing layers of geogrid SR- 2/UX1700. The present study is initially intended to work with concrete modular blocks of size 300mm × 300mm in plane with a height of 200mm. uniformly graded with different relative density and unit weight was used as backfill and surcharge for each tier. Reinforcing geogrid is used as reinforcing material with Fig. 4.1 Cross Section-44 m wall

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International Journal of Advanced Engineering Technology E-ISSN 0976-3945

5. FINITE-ELEMENT MODELING The reinforced wall is design as per the relevant The widening of ghat road in hilly areas where clauses in BS 8006-1995 and NCMA design other conventional techniques are not applicable manual on design of segmental . accepts the construction of MSE wall has been For the finite element modeling of the wall chosen for this parametric study. This paper PLAXIS 8.2 (a finite-element code for rock and based on the construction of the 40 meter soil soil analysis) has been chosen, and the construction of the wall is carried out safely and reinforced wall in Vijayawada (Andhra economically. The finite element mesh consists Pradesh). of 1276 numbers of 15-node triangular elements to the entire tiered wall and 338 number of 5- node bar element to model the reinforcement (geogrid). The horizontal and vertical boundary conditions are apply for the safe and accurate designing. 6. MATERIAL DATA SHEET There are four major components which constitute a reinforcing soil system. These are the soils, the reinforcement, the draining soil and the facing (skin). In order to design safe and economical reinforced soil structures it is necessary to have detailed characteristics of all four components.

• The Backfill and Draining Materials High quality backfill material is required for durability, good drainage, and good reinforcement interaction, which can be obtained from well graded granular materials. The back fill soil properties have a great influence on behavior of reinforced soil. The unit weights of materials, in Table 1, provide reasonable values

for unit weights of soils in the absence of Fig. 5.1 Finite-Element Modeling of the Soil reliable test results. Wall

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International Journal of Advanced Engineering Technology E-ISSN 0976-3945

Table 1- Unit weights of soils 3 3 Granular Material γm: Moist bulk weight (kN/m ) γsat : Saturated bulk weight (kN/m )

Loose Dense Loose Dense 16.0 18.0 20.0 21.0 Well graded sand and gravel 19.0 21.0 21.5 23.0 Coarse or medium sand 16.5 18.5 20.0 21.5 Well graded sand 18.0 21.0 20.5 22.5 Fine or silty sand 17.0 19.0 20.0 21.5 Rock fill 15.0 17.5 19.5 21.0

Table 2- Soil data sets parameters Mohr-Coulomb Backfill soil Draining soil

Type Units Undrained Drained 3 γdry kN/m 18 16 3 γsat. kN/m 20 20

Kx m/day 0.00 1.00

Ky m/day 0.00 1.00 2 Cref kN/m 10 1 φº · 30 30 2 Eref kN/m 6000 1000 ν - 0.3 0.3

Table 3- Modular facing Block Parameter Linear Elastic Modular Block Type Non-Porous 3 γdry (kN/m ) 24 2 10 Eref (kN/m ) 1.05X10 Ν 0.15

• The facing (skin) element structure, it also controls the aesthetics of the The facing element protects the soil and reinforced earth wall. reinforcing elements from weathering effects • The Reinforcing Element and used o keep the backfill soil from flowing. The soil reinforcing element is designed and Since the facing is the visible part of the positioned within the compacted backfill to give

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International Journal of Advanced Engineering Technology E-ISSN 0976-3945

the composite structure tensile strength. The • Mesh Data mechanism of soil to reinforcement stress The performance of the wall in the is transfer is through the pressure developed due to basically depends upon the mesh data in which overburden of the backfill soil on to the the project has been generating. reinforcing elements. Table 4- data set Parameter No. Identification EA (kN/m) ν

1 SR-2/UX-1700 64.10 0.00

Table 5- Number, Type of Element, Integrations Type Type of element Type of integration Total no. Soil 15-noded 12-point Gauss 1276 Geogrid 5-node line 4-point Newton-Cotes 338

7. RESULTS • Stresses

(a) Total Stress=977.77kN/m 2 (b) Cross sectional view

Fig. 7.1 Stresses on to the Wall

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International Journal of Advanced Engineering Technology E-ISSN 0976-3945

Fig. 7.2 –Depth vs. Stresses The total effective principal stresses are about- shows the total effective stresses on to the wall 973.06 kN/m 2. The stress is increases with the and fig. (b) Shows the cross-sectional view of depth of wall; negative sign shows the the effect of stress on to the MSE wall. downward effect of stresses to the vertical • Strain direction. The on to the top of The maximum strain acting on to the facing of the wall is about-9.39 kN/m 2 and increases with the wall, as the depth is increases the effects of the depth of the wall, and highest stress on to the the strains are also increases up to a certain wall is about-980.66 kN/m 2 located just at the limit. The total strain is of about 29.69%. of facing wall. Above fig. 7.1 (a)

(a) Stress-Strain Curve for 1 st Tiered wall (b) Stress-Strain Curve for 2 nd Tiered wall

(c) Stress-Strain Curve for 3 rd Tiered wall (d) Stress-Strain Curve for 4 th Tiered wall Fig. 7.3 –Stress vs. Strain Curve For Different Tiered wall

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International Journal of Advanced Engineering Technology E-ISSN 0976-3945

• Displacement Displacement, in Newtonian mechanics, presented the load vs. settlement graph for specifies the change in position of a point in different reinforcing layer, which shows that at a reference to a previous position. In simple terms, constant loading, as the depth increases the it's the difference between the initial position settlement were also increases. and the final position of an object. Fig. 7.4

Fig. 7.4 –Load vs. Displacement Plot for Different Reinforcing Layers

(a) (b) (c) (d)

Fig. 7.5 Displacement of Facing of Different Tiered Section

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International Journal of Advanced Engineering Technology E-ISSN 0976-3945

Fig. 7.5 (a) shows the displacement plot of 1 st “Parametric study of reinforced and unreinforced on soft soil ”. tiered wall, which gives the total displacement 3. BS 8006-1995 Code of practice for of the facing is about 0.18mm, Fig. (b) Shows Strengthened/ reinforced soils and other fills. nd 4. BS 8002-1994 Code of practice for Earth the displacement plot of 2 tiered wall, which retaining structures. gives total displacement, is about 0.15mm, Fig. 5. C.Yoo (2002), “ design of geosynthetics rd reinforced segmental retaining wall in a tiered (c) Shows the displacement plot if 3 tiered arrangement ”- Use of numerical modeling as a wall, gives the displacement is about 0.08mm, design aid. 6. C.R. Lawson, T.W. Yee & J-C Choi, “ Segmental th and Fig. (d) Gives the displacement of top 4 block retaining walls with combination geogrid tiered wall, gives the displacement is about and anchor reinforcements ” 7. G.L. Sivakumar Babu, professor, department of 0.05mm. from the above all the figures state that civil engineering, IIT Bangalore, “ Use of soil the maximum displacement of facing is in nailing for excavation stability and slope stability improvement ” – analysis of case study. bottom tiered and top tiered facing represents 8. Guangxin Li., yunminchen, Xiaowu tngg Eds.(2008), text book “ Geosynthetics in Civil minimum displacement. and Environmental engineering ” geosynthetic asia. 8. CONCLUSION 9. H.I. Ling, C.P. Cardany, L-X. Sun & H. The finite element analysis performed in this Hashimoto, “ Finite Element study of a Geosynthetic-Reinforced soil retaining wall ” study has indicated that geotextile reinforcement with concrete block facing. 10. Halil Murat Algin professor civil engineering may be an effective method of improving the harran university, turkey, “settlement analysis of performance of embankments constructed over geosynthetic reinforced soil retaining walls ” at foundation level. ghat road. The stabilizing effect of the geotextile 11. IS: 456-2000 code of practice for design of was seen to increase as the geotextile modulus concrete structures. 12. J.Otani, T.Hirai, H.Ochiai, and S.Shinowaki increased. The effect was greatest for shallower (1998), “ evaluation of foundation support for deposits. The effect of geotextile reinforcement geosynthetic reinforced soil wall on sloping ground ” was compared with alternative construction 13. K. Rajagopal, professor, department of civil techniques which involved the use of light engineering, IIT Madras, “ Design principal of reinforced soil walls ” weight fill or berms alone and in conjunction 14. NCMA Design Manual for Segmental Retaining with geotextile reinforcement. In particular, it Walls , 3rd Edition (2009). 15. PLAXIS 8.2 design manuals a “finite element was found that the combined use of geotextile code for rock and soil analysis”. 16. P.T. Raju “ Construction of tiered reinforced soil reinforcement and light weight fill may be a retaining walls ” for widening of ghat road to very effective means of improving the sridurga malleswara swami varla devastanam, Vijayawada. performance of embankments over hilly . 17. Robert M. Koerner (1990), text book, second 9. REFERENCES edition, “ designing with geosynthetics ”. 18. Techfab india industries LTD. (2007), “ techgrid 1. AASHTO (American Association of State geogrid reinforced soil walls with welded wire Highway and Transportation Officials), LRFD mesh facing ” to retain the approach to a flyover. (Load and Resistance Factor Design), MSE (Mechanically Stabilized Earth) wall design manual . 2. Abdul aziz A. kamal, pauleen A. lane, and Ali A.R. Heshmati (2005), 13 th ACME conference,

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