Analysis of Llp

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Analysis of Laterally loaded piles.

Project Part-B

NIT Warangal

2nd May 2016

Members:Aakash Mishra(121201)

Rajeeb Singh(121148)Khandu Wangmo(121130)Sherab Jorden(121260)

Supervisor:Dr. Ramana Murthy V, Associate Professor, Geotechnical Division

Project Part-B Analysis of Laterally loaded piles.



Failure mechanism.

Failure mechanism for Axial pile is simple. Pile movesdownward if acting load exceeds the soil resistance and pile

suffers excessive vertical deflection and ultimately leads tocollapse of the structure.In case of Lateral pile mechanism is a bit complex. In thiscase pile can rotate, bend or translate.If the pile is small then it doesn’t bend much but rotates oreven translate. This type is called rigid pile.If the pile is long and slender then it bends on application of load. This type is known as flexible pile.

Figure: Translation. Figure: RotationProject Part-B Analysis of Laterally loaded piles.



Different Approaches for Analysis.)

Beams on Elastic Foundation.

Reese and Matlock: They were the first who assumed thatthe soil modulus to be changing i.e. increasing with depth anddeveloped solutions for laterally loaded piles in a

non-dimensional form. They have developed the expressionsfor the computation of shear force, bending moment, soilreaction and deflection for cohesion less soil.

Davisson and Gill: For elastic cohesive soil this method isemployed to calculate deflection, shear force, bending moment

and soil reaction.

Broms approch :- Broms provided the graph for calculationof lateral capacity of the pile in both cohesive andnon-cohesive soil, in both conditions of Rigid and Flexible pile.




Continuum Approach.

Analysis of laterally loaded pile can be made by treating thesoil which is surrounding the pile as 3 D continuum.

This concept is conceptually more appealing than Beams onElastic Foundation Approach since the interaction betweenpile and soil is indeed 3 D in nature.

Today the most versatile continuum based method for analysisavailable is Finite Element Method. Same method is employed

for our analysis using FEM software.




Single fixed head pile subjected to lateral load in mediumclay.

The soil, pile and Load details are given below:-Medium clayC/s of the pile = Circular

Length of the pile(L)=15mPile Diameter(D) = 80cmpile Cover= 75mmConcrete(γ ) = 25kN/m3Horizontal Force(H) = 400kN

unit weight= 19kN/m3cohesion(C)= 25kN/m3




Figure: Change in thedeflection. Figure: Change in BM

Figure: Change inLateral Capacity.

Figure: Change inMOR




Summary.

It is observed that with change in modulus of elasticity of themedium clay with other parameters constant, the LateralCapacity against the lateral load decreases.

Max. deflection and max. bending moment also decreaseswith increase in modulus of elasticity of the soil.

It can be concluded that with an increase in modulus of elasticity can’t improve the lateral capacity of the soil but ithelps in reducing the lateral deflection of the pile.


C



Change in cohesion in soft clay.

Figure: Change in

Lateral capacity.

Figure: Change in

MOR

Figure: Change in

Axial Capacity.

Figure: Change in

deflectionProject Part-B Analysis of Laterally loaded piles.

S



Summary.

It is observed that with change in the cohesion of the soil theLateral Capacity , Axial Capacity as well as Lateral Momentof Resistance of the soil against the lateral load increases.

Max. deflection, max. Bending moment and Max. ShearForce remains constant.

It can be concluded that with an increase in the cohesion of the soil lateral capacity of the soil increases. It is wise toimprove the cohesion of the soil instead of the modulus of elasticity to increase the lateral capacity.

At the same time if the issue is regarding the deflection thenit’s wise to improve the elasticity of the soil rather thanimproving the cohesion.


R l f Ch i A l f Sh i R i f h



Results of Changing Angle of Shearing Resistance of thesoil

Figure: Results of changing angle of shearing resistance.


Ch i l f h i t f d d



Change in angle of shear resistance for dense sand.

Figure: Change in

Lateral capacity.

Figure: Change in

MOR

Figure: Change inAxial Capacity.

Figure: Change indeflection


S



Summary.

It is observed that with change in the value of φ the LateralCapacity , Axial Capacity as well as Lateral Moment of Resistance of the soil against the lateral load increases.

It can also be concluded from the graph that Axial capacity of the soil increases curve linearly as the value of the angle of shear resistance increases.

The max. deflection, max. Bending moment and Max. ShearForce remains constant with change in the Angle of ShearingResistance of the soil.

It is wise to improve the Angle of shear Resistance of the soilto increase the lateral capacity.


St d i b h i f th il s bj t d t t



Study in behavior of the pile subjected to moment.

The soil, pile and Load details are given below:Sand 1Cross-section of the pile = CircularLength of the pile(L)=15m

Pile Diameter(D) = 80cmpile Cover= 75mmConcrete (γ ) = 25kN/m3Moment acting at tip of pile (M) = 400kN-mEccentricity(e)= 1m unit weight= 14.5kN/m3

Angle of Shearing resistance(φ) = 37




Design check and safety of the pile



Design check and safety of the pile

C/s of the pile = CircularLength of the pile(L)=15mPile Diameter(D) = 80cmpile Cover= 75mm

Concrete(γ ) = 25kN/m3Horizontal Force(H) = 400kNunit weight= 14.5kN/m3Angle of Shearing resistance(φ) = 37Poisson ration(µ)=0.3

Elasticity of the soil(E)= 40Mpa.




Figure: Reinforcement design.


Conclusions



Conclusions

It is essential to check the reinforcement in the pile by takingboth flexural stress and shear stress into consideration. andshear stress.

To take care of bending stress flexural reinforcement isprovided all along the length of the pile in the form of longitudinal bars and for the shear stress helical stirrups areprovided all along the length of the pile with desired spacingbetween stirrup steps.


Soil and pile behavior in multi-layered soil stratum



Soil and pile behavior in multi-layered soil stratum

When a single fixed head circular pile subjected to lateral loads inembedded multi-layered soil strata.

Figure: Soil details of different layers.


Results



Results

Figure: BM and SF.Figure: soil pressureand axial force.




Figure: Horizontal

and verticaldeflection.

Figure: Ultimate

horizontal capacity of the pile.




Figure: Axial capacity of thepile. Figure: Reinforcement check.


When top 7m layer of the soil is replaced by the stiff clay



When top 7m layer of the soil is replaced by the stiff claylayer

The top layer of the soil is replaced with stiff clay and change inpile and soil characteristics are observed and comparison is made.

Figure: Soil layer details.


Results



Figure: BM and SF.Figure: soil pressure and axialforce.


Results



Figure: Horizontal andvertical deflection of thepile. .

Figure: Ultimate horizontalcapacity of the pile.


Results





Results



Figure: Horizontal andvertical deflection.

Figure: Ultimate horizontalcapacity.





When the soil layer below the tip of the pile is replaced



with stiff clay

Figure: Soil details


Results



Figure: BM and SF.Figure: Soil pressure andaxial force.


Results



Figure: Ultimate horizontalcapacity.

Figure: Axial capacity of thepile.


Results



Figure: Horizontal andvertical deflection. Figure: Reinforcement check.





References.



M.J. Tomlinson. PILE DESIGN and CONSTRUCTION

PRACTICE . Fourth Edition, 1994.

APPC soil properties,http://docslide.us/documents/appc-soil-properties.html

Analysis of laterally loaded piles in layered soils,http://www.ejge.com/2008/Ppr0886/Ppr0886.pdf

Three dimensional modeling of laterally loaded pile groupsresting in sand,

http://www.sciencedirect.com/science/article




THANK YOU!


Analysis of Llp

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