settlement in foundations

8/6/2019 Settlement in Foundations

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23 July 2011 1

G.MADHURI M.E Structural Engineering

Civil Engineering


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23 July 2011 2


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23 July 2011 3SETTLEMENTS IN FOUNDATION


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23 July 2011 SETTLEMENTS IN FOUNDATION 4


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CAUSES OF FOUNDATIONCAUSES OF FOUNDATION

PROBLEMSPROBLEMS

Construction Flaws

The Ground Around Your Structure

Uneven Support

The Structure



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IDENTIFYING AIDENTIFYING A

FOUNDATIONFOUNDATIONPROBLEMPROBLEM



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EXTERIOR INDICATIONS OF FOUNDATION PROBLEMSEXTERIOR INDICATIONS OF FOUNDATION PROBLEMS

Doors that will not open or close properly

Gaps at the corner of fascia trim

Diagonal cracks in the wall at corners of doors

and windows

Gaps between the garage door and the pavement

at either side of the garage door

Windows that are hard to open and close

Cracks in the exposed grade beam of the house

Cracks in bricks and mortar



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INTERIOR INDICATIONS OF FOUNDATION PROBLEMSINTERIOR INDICATIONS OF FOUNDATION PROBLEMS

Unlevel Floors

Large cracks in the concrete slab

Gaps above kitchen cabinets Cabinet doors that will not stay shut

Diagonal cracks in the wall at corners of doors

and windows Leaks and cracks in and around the fireplace



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Exterior or interior indications offoundation problems could be caused

by

Upheaval

Settlement



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UPHEAVAL :

Foundation upheaval can lift an entire structure but

more often it forces parts of a foundation or slab

upwards while the other section remain stationary.



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SETTLEMENTSETTLEMENT

Settlement means a portion ofthe house foundation hasdropped below the original

foundation elevation.



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Weak bearing soils

Poor compaction Changes in moisture

content

Maturing trees and

vegetation Soil consolidation



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REPAIR METHODS FORREPAIR METHODS FOR

FOUNDATIONFOUNDATIONSETTLEMENTSETTLEMENT



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GROUT PUMPING OR MUDGROUT PUMPING OR MUD

JACKINGJACKINGMudjacking is a process by which a mud is pumped, with

pressure behind it under a concrete slab, with enough pressureto raise, to jack up, the concrete slab.

Usually, a low strength concrete is used.

It is used to stabilize soils below settling footings or slabs.

Mud jacking is suitable if bearing rock or stable soils are not toodeep.



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ADVANTAGES : Mudjacking is relatively inexpensive and it is fast.

DISADVANTAGES:

That it comes with no warranty,

It can lead to your sewer lines being filled with concrete, Sometimes the concrete emerges in unexpected places,

such as the inside of a wall, where there are unidentifiedholes in a slab.



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A pattern of 1-5/8 inch holes are drilledthrough the sunken slab.

A grout mixture is pumped under the slab

with our specializedequipment. Once any void is filled, the

grout becomes

pressurized, hydraulically raising the slab

to the desired height.

The holes are patched using a concrete

mixture.

SLABSLAB

JACKINGJACKING



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It can be done in virtually any weather.

The grout used to raise the slab provides a stable base, thus strengthening

the slab.

Nothing needs to be moved off the slab, as the pump can lift the weight of

the slab.

Low cost: The cost to raise the concrete slab to its original position is

approximately one third compared to replacement.

No loss of use: This technique allows the client to use the slab

immediately.

If the slab is replaced the concrete has to cure for a minimum of 28 days.

BENEFITS TO SLAB JACKINGBENEFITS TO SLAB JACKING



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DRIVEN STEELDRIVEN STEEL

PINSPINS

These are used to stabilize settling foundation wallsor footings. A pin is driven next to the foundationand is inserted into the soil until it contactsbedrock.

The driven pin foundation repair method is oftenused when a portion of a foundation wall is movingor settling, perhaps because of improper site workor footing undermining.

The steel pin foundation repair method permitsmore precise leveling control across the buildingthan grout pumping.



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HELICAL PIER ORHELICAL PIER OR

SCREW-PIERSCREW-PIERHelical / Screw piers are an approach

similar to the driven steel pins, but may beshorter in length and useful where soilconditions do not provide shallow bedrock.

Helical piers to repair sinking foundationsare often used in building repair orreconstruction, and include models whichcan be used to level floor slabs as well.



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No heavy equipment required

Quick installationLower costs

Time-proven engineered system

Installs in limited access areasLimited excavation required


HELICAL PILE FOUNDATION REPAIRHELICAL PILE FOUNDATION REPAIR

ADVANTAGESADVANTAGES


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ROD & STEEL U-CHANNEL ORROD & STEEL U-CHANNEL OR

I-BEAMI-BEAMRod & Channel Repair to Stabilize

Structures over Poor Soils.

Rod and u-channel structural repairs are more

likely to be used where soil conditions prohibitthe other pier or jacking methods

Threaded steel rods are run through the widthor length of the damaged structure and boltedto vertical steel U-channels on the buildingexterior.



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RECONSTRUCTION OFRECONSTRUCTION OF

FOUNDATIONSFOUNDATIONS Some engineers who examine a failing

foundation may prescribe excavation andreconstruction, possibly with reinforcement

over the original design and with additionalfoundation and site drainage. And indeed insome cases these extensive foundation repairsteps are completely appropriate andnecessary both to repair the building and toprevent a recurrence of the trouble.



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For smaller slabs of sunken concrete, suchas residential slabs, driveways, sidewalks,swimming pool decks, etc. is slabjacking.

For larger problems,especially those foundin house and commercial building

foundation shifting, piering is typicallyused to lift and stabilize the foundation.



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23 J l 2011 SETTLEMENTS IN FOUNDATION 31

settlement in foundations

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