Corrective measure to check pile foundation failure

Pile foundation contains sound bearing strength, good durability and small differential settlement with regards to other foundation types.

Pile foundations are normally provided in the following conditions :-

1. Low bearing strength of soil.
2. Non-existence of perfect bearing stratum at shallow depths.

3. Greater loads from the super structure for which shallow foundation may not become inexpensive or feasible.

But pile foundations become damaged and collapse specifically throughout earthquakes because of the following purposes.

1. Inadequacy of sufficient boring
2. Improper soil grouping
3. Soft strata under tip of pile
4. Insufficient driving formula (wrong data)

5. Imperfect size of hammer leads to deficient penetration, too light or get damaged if too heavy
6. Misapprehension of load
7. Damaged of encased piles
8. Buckling of piles
9. Cracking of piles
10. Vibration that leads to lateral or vertical movement
11. Flowing strata resulting from adjoining excavation or bank sloughing
12. Tension failure of concrete pile for shortage of reinforcement
13. Eccentricity because of bowing or falling out of plumb
14. Deterioration caused by lower ground water level
15. Insect and marine borer attack and erosion

16. Detachment of concrete caused by poor quality of concrete or reactive aggregate
17. Failure of the thin shell of the piles
18. Overweight owning to earthfill.

Corrective measures to get rid of failure of pile foundation:

1. Preliminary repair like encasement or replacement
2. Extraction of partial load
3. Underpinning

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Published By
Rajib Dey
www.constructioncost.co
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Some useful tips on concreting in hot weather

The quality of concrete is affected by severe weather conditions (intense heat or cold, and humidity deviations). If concreting is done in hot weather, proper precautions should be taken to combat all the adverse effects of extreme ambient temperature.

Definition of hot weather for concreting: As per guidelines provided by American Concrete Institute (ACI) vide ACI-305R-10, hot weather means job-site conditions that speed up the rate of moisture loss or rate of cement hydration of freshly mixed concrete, along with the following:

a) Ambient temperature of 27 °C (80°F) or greater; and
b) Evaporation rate that surpasses 1 kg/m2/h

Canadian Concrete Design code (CSA A23.1/.2) employs the similar ambient temperature for hot weather (27 °C).

Challenges of Hot Weather Concreting

How concrete is impacted with hot weather: The water is a prime ingredient in concrete. When the temperature is raised, the rate of vaporization is also increased. So, adequate quantity of water is required in concrete production to cope up with hot weather condition.

The following issues are also occurred due to hot weather condition:

1- Accelerated slump loss leading to the addition of water on the job-site,
2- Increased rate of Setting resulting in placing and finishing difficulties,
3- Increased tendency for thermal and plastic cracking,
4- Critical need for prompt early curing,
5- Difficulties in controlling entrained air,
6- Increased concrete temperature resulting in long term strength loss.

Precautions for Hot Weather Concreting: These precautions should be taken throughout concrete production and delivery, and will enhance the stability performance of concrete to get rid of unwanted cracking.

1- Apply materials and mix proportions which contain good resistance capacity against hot-weather conditions.
2- Chill the concrete or one or more of its constituents.
3- The uniformity of concrete should allow quick placement and consolidation.
4- Minimize the time of transport, placing and finishing as far as possible.
5- Schedule concrete placements to control exposure to atmospheric conditions (i.e. at night or all through good weather conditions).

Common Solutions for Cooling Materials: The common process to be followed for chilling concrete is to reduce the temperature of the concrete materials prior to start of mixing.

The aggregates and mixing water should be retained as cool as possible since these materials significantly affect the concrete temperature after mixing as compared to other materials. In severe hot condition, a segment of water is substituted with ice to reduce the temperature. Curing of concrete is vital for decreasing the adverse effects of hot weather on the quality of concrete.



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Published By
Rajib Dey
www.constructioncost.co
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