Week 7 Challenge

AIM-:

1)How to fix no. of piles in the deep foundations in a flyover in Delhi, listing all the loads acting on it and making all the combinations as per IRC 6.

What are the different factors that can impact the number of piles and its depth.

how it is different in wall type abutment .

and pier (free and fix)

ANS-:For Delhi area the type of soil found there is sandy, loamy, sand or sandy loam and loam silty loam. Hence pile foundation is suitable for such type of soil.

Piles are the structural component which comes under the deep foundation, The function of the pile is to transmit a load of a structure to competent sub-surface strata by the resistance develop from bearing at the toe or skin friction along the surface of both. piles also carry uplift pressure and lateral load.

No of piles that are required in deep foundation is calculated by using the below formula,

Number of piles = Safe bearing capacity of soil/pile capacity.

The pile shaft should have adequate structural capacity to withstand all loads (vertical, axial or otherwise) and moments which are to be transmitted to the subsoil .The load-carrying capacity of a pile depends on the properties of the soil in which it is embedded.

Following are the loads which is acting on the structure.

1. Dead load
2. SIDL
3. Vehicular Live Load.
4. Breaking Force.
5. Live Load surcharge.
6. Earth pressure (In abutment)
7. Water Current Load.
8. Wind Load.
9. Temperature Load.
10. Earth quake load.

calculating single pile capacity and then by usaing above formula no. of pile can be calculated

Factors that can impact no.of piles-:

loading from superstructure

loading from substructures

soil weight

water current force

bearing capacity of soil

friction in soil

Spacing in piles and diameter of piles

different from wall type abutment and pier

PILE	WALL ABUTMENT	PIER
In rocks, the pile should be taken down to rock strata devoid of any likely extension of erosion and properly socketed as required by the design.	Foundation may be taken down to a comparatively shallow depth below the bed surface provided good bearing stratum is available, and the foundation is protected against scour.	The foundations shall be taken to such depth that they are safe against scour or protected from it.
In soil, the minimum depth of foundations below the point of fixity should be the minimum length required for developing full fixity as calculated by any rational formula.	The embedment of foundations in soil shail be based on correct assessment of anticipated scour considering the values given under Clause 703 of IRC 78.	For fix pier longitudinal moment created in the superstructure should be taken into consideration generated due to worst possible load combination for deciding depth of foundation. For free pier only superstructure and substructure loadings are considered for determining depth of foundation.
piles should also be designed to sustain surcharge effect of embankment.	it is important to consider overall stability of the structure and abutment.	the depth should also be sufficient from consideration of bearing capacity, settlement, liquefaction potential, stability and suitability of strata at the founding level and sufficient depth below

2)How to fix the diameter of well in the deep foundation in a river bridge in Delhi, listing all the loads acting on it and making all the combinations as per IRC 6.

ANS-:Well foundation is a type of deep foundation which is generally provided below the water level for bridges. many factor which decide the diameter of well foundation in river bridges i.e. Property of soil, mean velocity of water flowing in the river, base pressure, uplift pressure etc.

The minimum dimensions of dredge-hole shall not be less than 3 m as per IRC 78 Cl.708.

external diameter of singular circular not exceeds 12 M.

different factors that can impact the diameter of welL-:

Factors that can impact diameter of well are loading from superstructure and substructures, soil weight, if it is present in a water body then water current force, bearing capacity of soil & friction in soil.

For well foundation in soil,

Well foundations shall be taken down to a depth which will provide a minimum grip of 1/3rd the maximum depth of scour below the design scour level specified in Clause 703.3 of IRC 78

1)What is free standing length in a pile system and how to determine this.

Also list all the applicable code clauses from IRC and IS codes

ANS-:

The lenght of piles which is coming under scour depth and liquification zone is known as free standing length in pile system. piles under scouring and liquification is important criteria consider for designing the pile foundation.For free standing lenght we have to worry by taking different criteria like providing Liner in that lenght.

Codes which is use to design and contruction process of pile are IRC 78, IS 2911

Imp clauses we is use in Code are.

In IRC 78: Clause no 703 (discharge and depth of scouring for foundation desing.) is use to find free standing lenght in pile system.

Clause no 706 for loads, forces, stability and stress in foundation design.

Clause no 708 for detail about well foundation.

Clause no 709 for detail about Pile foundation.

IS 2911 code is all about pile foundation design and construction.

2)What will be the impact of free-standing length on the full length of the pile.

Roughly determine no. of piles on abutment of height 5 m and width of 12 m.

Vertical capacity – 250 tonnes

Horizontal capacity-35 tonnes

ANS-:

The capacity of piles may be reduced by slenderness effects when a portion of the pile is free standing or when the soil is too weak to provide lateral support. A group of free standing piles is likely to settle more than a single pile.

The capacity of piles may be reduced by slenderness effects when a portion of the pile is free standing or when the soil is too weak to provide lateral support

A group of free standing piles is likely to settle more than a single pile.

No.of piles = Total load from above/Capacity of 1 pile

SUPERSTRUCTURE LOAD=12*5*2.5=150T

150/2500=1 , provide 1 no. of pile

c)List out failures in deep foundations and their remedies as per the codal provisions.

What all construction parameters need to be taken care of before planning a deep foundation

ans-:

Following are failure in deep foundation and there remedies.

• Unequal settlement of the sub-soil
• Horizontal movement of the soil adjoining the structure.
• Tilt and tolerance failure.
• Lateral pressure tending to over- turn the structure
• lateral escape of the soil below the foundation
• Rcc failure.
• Buckling of piles.
• Breaking of piles.
• Tension failure of concrete pile for lack of reinforcemen.
• Disintegration of concrete due to poor quality of concrete or reactive aggregate.

Remedies to prevent failure of pile foundation:

• Early repair such as encasement or replacement
• Removal of partial load
• Underpinning

Construction parameter use in deep foundation.

• Protective works i.e. cofferdam, sheet pilling to be done around the foundation.
• Site clearence adn boring shall be done as per indian standerd.
• Lowering the steel cages after clearing.
• Casting the piles by pouring wet concrete.
• Bottom plug sink & top plugging in case of well.