Taiyaba rashid jmi

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RETAINING WALLS-TAIYABA RASHIDF/O ARCHITECTURE & EKISTICSJAMIA MILLIA ISLAMIANEW DELHI

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RETAINING WALLS

• Retaining walls are used to retain earth or other materials which have the tendency to slide and repose at a particular inclination.

• They provide lateral support to the earthfill, embankment or other materials in order to hold them in a vertical position.

• Types:Gravity retaining wallCantilever retaining wallCounterfort retaining wallButtress retaining wallBasement/foundation wallBridge abutment

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GRAVITY RETAINING WALL• Made of plain concrete or brick masonry.

• Stability of wall is maintained by its weight.

• Generally made up to a height of 3m of wall.

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CANTILEVER RETAINING WALL

• Consists of a vertical wall, heal slab & toe slab which act as cantilever beams.

• Stability maintained by weight of retaining wall & weight of earth on the base of retaining wall.

• Height ranges from 3m to 8m.

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COUNTERFORT RETAINING WALL

• Height ranges from 6m to 8m.

• More economical to tie the vertical wall with the heel slab by counterforts at some spacing.

• Acts as tension member to support vertical wall & reduces bending moment.

• Supports the heel slab & reduces bending moment.

• Spacing: 1/3rd the height of wall.

• Stability maintained by weight of earth on base & by self-weight.

• More widely used as it is hidden beneath the retained materials.

• Has a clean, uncluttered face for more efficient use of space in front of wall.

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COUNTERFORT RETAINING WALL

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BUTTRESS RETAINING WALL

• Similar to the counterfort wall.

• Vertical wall is tied with toe of retaining wall at some spacing.

• Acts as compression member to support vertical wall & reduces its bending moment.

• Supports toe slab & reduces its bending moment.

• Spacing: 1/3rd the height of the wall.

• Buttress as compression member is more economical than a tension counterfort.

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BUTTRESS RETAINING WALL

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BASEMENT/FOUNDATION WALL

• Restrained at the bottom by basement floor slab & at the top by the first floor slab.

• Subjected to:Lateral earth pressure exerted by

earth fillVertical load from superstructure.

• Lateral support is provided by basement floor & first floor slabs.

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BRIDGE ABUTMENT• Behaviour similar to basement or

foundation wall.

• Superstructure induces horizontal & vertical loads that alter the normal cantilever behaviour.

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BRIDGE TERMINOLOGY

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FORCES ON RETAINING WALLS

• Self-weight

• Weight of soil above foundation base

• Earth pressure

• Surcharge i.e., forces due to loads on earth surface

• Soil reactions on footing

• Friction on footing due to sliding

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CONSTRUCTION METHODS

• A concrete retaining wall

• An interlocking block retaining wall

• A Wood retaining wall

• An Insulated Concrete Form retaining wall or ICF retaining wall

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SLOPE STABILITY• The field of slope stability encompasses the analysis of static and

dynamic stability of slopes of earth and rock-fill dams, slopes of other types of embankments, excavated slopes, and natural slopes in soil and soft rock.

SIMPLE SLOPE SLIP SECTION

SLOPE WITH ERODING RIVER & SWIMMING POOL

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SLOPE STABILITY

• If the forces available to resist movement are greater than the forces driving movement, the slope is considered stable.

• Factor of safety=Forces resisting movement /Forces driving movement.

• In earthquake-prone areas, the analysis is typically run for static conditions and pseudo-static conditions, where the seismic forces from an earthquake are assumed to add static loads to the analysis.

• METHOD OF SLICES

• BISHOP’S METHOD

• SARMA METHOD

• LORIMER'S METHOD

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• Method for analysing the stability of a slope in two dimensions.

• The sliding mass above the failure surface is divided into a number of slices.

• The forces acting on each slice are obtained by considering the mechanical equilibrium for the slices.

SLOPE STABILITY-ANALYSIS METHODSMETHOD OF

SLICES

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• Proposed by Alan W. Bishop.

• Method for calculating the stability of slopes.

• An extension of the Method of Slices.

• By making some simplifying assumptions, the problem becomes statically determinate and suitable for hand calculations.

• Forces on the sides of each slice are horizontal

• The method has been shown to produce factor of safety values within a few percent of the "correct" values.

SLOPE STABILITY-ANALYSIS METHODSBISHOP’S

METHOD

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• c’= effective cohesion

• ’= angle of internal friction

• b= width of slice

• w= weight of each slice

• u= water pressure at base of each slice

SLOPE STABILITY-ANALYSIS METHODSBISHOP’S

METHOD

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• Proposed by Sarawa K. Sarma

• A Limit equilibrium technique used to assess the stability of slopes under seismic conditions.

• May also be used for static conditions if the value of the horizontal load is taken as zero.

• Can analyse a wide range of slope failures as it may accommodate a multi-wedge failure mechanism and therefore it is not restricted to planar or circular failure surfaces.

• May provide information about the factor of safety or about the critical acceleration required to cause collapse.

SLOPE STABILITY-ANALYSIS METHODS

SARMA METHOD

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• Developed in the 1930s by Gerhardt Lorimer.

• A technique for evaluating slope stability in cohesive soils.

• Differs from Bishop's Method in that it uses a clothoid slip surface in place of a circle.

• This mode of failure was determined experimentally to account for effects of particle cementation.

SLOPE STABILITY-ANALYSIS METHODS

LORIMER'S METHOD

A CLOTHOID OR EULER SPIRAL

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REINFORCED EARTH

• Also called Mechanically Stabilized Earth or MSE.

• Soil constructed with artificial reinforcing.

• Can be used for retaining walls, bridge abutments, dams, seawalls, and dikes.

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REINFORCED EARTH• MSE walls stabilize unstable slopes and retain the soil on steep slopes and

under crest loads.

• The wall face is often of precast, segmental blocks, panels or geocells that can tolerate some differential movement.

• The walls are infilled with granular soil, with or without reinforcement, while retaining the backfill soil.

• Reinforced walls utilize horizontal layers typically of geogrids.

• The reinforced soil mass, along with the facing, forms the wall.

• In many types of MSE’s, each vertical fascia row is inset, thereby providing individual cells that can be infilled with topsoil and planted with vegetation to create a green wall.

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• Ease of installation.

• Quick construction.

• Do not require formwork or curing and each layer is structurally sound as it is laid, reducing the need for support, scaffolding or cranes.

• Do not require additional work on the facing.

• Retain sufficient flexibility to withstand large deformations without loss of structural integrity, and have high seismic load resistance. 

REINFORCED EARTHADVANTAGES

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GEOSYNTHETIC MATERIALS• Polymeric products used to solve civil

engineering problems.

• Includes eight main product categories: geotextiles, geogrids, geonets, geomembranes, geosynthetic clay liners, geofoam, geocells and geocomposites.

• Suitable for use in the ground where high levels of durability are required.

• Can also be used in exposed applications.

• Available in a wide range of forms and materials, each to suit a slightly different end use.

Geocells

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GEOSYNTHETIC MATERIALS

GEOSYNTHETIC REINFORCED STRUCTURES

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GEOGRID• Geosynthetic material used to reinforce soils.

• Used to reinforce retaining walls, as well as subbases or subsoils below roads or structures.

• Soil pulls apart under tension. Compared to soil, geogrids are strong in tension.

• Transfer forces to a larger area of soil.

• Made of polymer materials, such as polyester, polyethylene or polyproylene.

• Woven or knitted from yarns, heat-welded from strips of material, or produced by punching a regular pattern of holes in sheets of material, then stretched into a grid.

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GEOCELLS• Also called Cellular Confinement

Systems.

• Used in construction for erosion control, soil stabilization on flat ground and steep slopes, channel protection, and structural reinforcement for load support and earth retention.

• Typically made with ultrasonically-welded high-density polyethylene (HDPE) or Novel Polymeric Alloy strips that are expanded on-site.

• Creates a stiff mattress or slab to distribute the load over a wider area.

• Reduces punching of soft soil.

• Increases shear resistance and bearing capacity.

• Decreases deformation.

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