Bài tập lớn nền móng ĐHGTVT

Bài tập lớn nền móng ĐHGTVT Sử dụng FB pier tính toán móng cọc đơn lẻ hay tổ hợp cọc. Tính toán sức kháng thành cọc và đầu mũi cọc,... . Hi vọng sẽ giúp ích được các bạn trong việc hoàn thành bài tập lớn được giao

INTERNATIONAL EDUCATION FACULTY

DESIGN OF DRIVEN PILE

ASSIGNMENT

Full name : Nguyen Thien Long

ID Student : 172603217

Course : 58

Major : Advanced Training Program

Project Supervisor's Report : Assoc Prof.PhD Nguyen Chau Lan

Hanoi, November 2020

Category Part I SOIL INVESTIGATION REPORT

Contents

I Geological structure and characteristic of soil layers 4

II Conclusion and suggestion: 4

I Designing the size of the foundation 6

1.1 Size and elevation of pier and foundation 6

1.2 Size and elevation of pile 6

II Design Load 7

2.1 Weight of column 7

2.1.1. Height of pier (without pier cap) 7

2.1.2 Total volume of pier (without pier cap) 8

2.1.3 Volume of pier, which is under water (without pier cap): 8

2.2 Design loads group corresponding lowest water level 8

2.2.1 Standard load at longitudinal bridge in service limit state 8

2.2.2 Designed load at longitudinal bridge in strength limit state 9

III Axial Capacity 10

3.1 Axial bearing capacity of material of pile PR 10

3.2 Bearing resistance of soil QR 11

3.2.1 Frictional Resistance Qs 12

3.2.2 Load carrying capacity of the pile point Qp 14

3.3 Single Pile bearing capacity Ptt 15

IV Pile number and pile distribution in foundation: 15

4.1 Computing Pile number n: 15

4.2 Pile distribution 15

4.2.1 Arranging piles 15

4.2.2 Cap volume: 15

4.3 Loads transfer to cap 15

4.3.1 Loads in service limit state 15

4.3.2 Loads in strength limit state 16

V Checking Strength Limit State 16

5.1 Checking single pile axial resistance 16

5.1.2 Checking single pile axial resistance: 18

5.2 Checking the axial bearing capacity of group pile: 18

VI Checking Service Limit State 19

6.1 Determine total consolidation settlement 19

6.2 Checking pile head displacement 21

VII Strength of bars and pile joint 22

7.1 Computing and arranging vertical bar in pile 22

7.1.1 Computing maximum moment of lifting and pitching of pile 22

7.1.2 Caculating the number of reinforce bars needed 23

7.2 Reinforcement of the belt for the pile 24

7.3 Detail of hard pile rod reinforcement 25

7.4 Reinforced wire rod 25

7.5 Steel stake head 25

7.6 Steel hooks 25

VIII Joint construction 25

Part I SOILS INVESTIGATION REPORT

I Geological structure and characteristic of soil layers

At Drilled Hole 4 - BH4, drilled to - 40m met 4 layer of soil:

■ Layer 1: Grey-Clayey Silt, liquid state

 Elevation of the surface: 0.0(m)

 Bottom elevation: -5.2(m)

 Water content W = 25.8%

 Saturated ratio Sr = 85.3%

 Plastic Index IL= 0.51

■ Layer 2: Fine sand, grey, very loose

Layer 2 occurs in Drilled Hole 4 - BH4 founded under Layer 1

 Thickness: 9.0(m)

 Elevation of the surface: -5.2(m)

 Bottom elevation: -14.2(m)

■ Layer 3: Green, grey -Clayey Silt, semi-solid state

Layer 3 occurs in Drilled Hole 4 - BH4 distributed under layer 1 and layer 2

■ Layer 4: Grey - Fine Sand, semi-dense state

Layer 4 occurs in Drilled Hole 4 - BH4, distributed under layer 1, layer 2 and layer 3

 The profile of soil in this area is diverse, complicated and non-uniform

 Layer 1 & 2 were weak layer because of low SPT index and load capacity, layer 3 had average SPT index, and layer 4 had highest ratio

 Layer 2 would be appeared settlement when put the foundation in there,

■ Suggestion:

 Due to this profile, the recommended suggestion is Friction pile- Concrete pile

 The end of pile should be placed into layer 4

Part II Technical design Overall Design

I Designing the size of the foundation

1.1 Size and elevation of pier and foundation

 Elevation of pier

In navigable waterway, the elevation of grider’s bottom is calculated as following:

Where:

o PTE: Pier top elevation

o HWL: The highest water level

o NWE: Navigable water elevation

o The thickness of foundation(TF): 2(m)

o The elevation of foundation’s top(EFT):

Choose EFT = -2.5(m)

o The elevation of foundation’s bottom(EFB):

 Elevation of pile:

o The thickness of pile cap(TPC): 1(m)

o The elevation of pile cap’s top(EPCT):

o The elevation of pile cap’s bottom(EPCB): concided with EFB, so

EPCB=-4.5(m)

1.2 Size and elevation of pile

❖ Pile tip elevation: -35.50(m)

❖ Shape and size of pile: The cross section of piles is square and the size is

450x450(mm2)

❖ Length of piles: (without the length of pile cap)

 The slender of pile:

❖ Total length of precast concrete pile:The pile is divided into 4 segments, eachsegment is 8m long and spliced by weld.

II Design Load

2.1 Weight of column

2.1.1 Height of pier (without pier cap)

Height of pier(without cap) Htr:

Where:

o Pier top elevation : PTE = 7(m)

o Elevation of foundation’s top : EFT = -2.5(m)

o Head cap thickness : HCT = 0.8+ 0.6= 1.4 m

2.1.2 Total volume of pier (without pier cap)

Total volume of column Vtr:

2.1.3 Volume of pier, which is under water (without pier cap):

Volume of pier column under water surface Vtn:

Trong đó:

LWL = 3.1(m) : Lowest water level

EFT = -2.5(m) : Elevation of foundation’s top

Str : Area of column’s cross section (m2)2.2 Design loads group corresponding lowest water level

Load Unit limit stateService

- Vertical dead-load in service limit state at top of pier kN 5000

- Vertical live-load in service limit state at top of pier kN 2500

- Lateral live-load in service limit state at tranverse kN 120

Mo- Momentum of live-load in service limit state KN.m 900Load factor: Live load : n = 1.75

Dead load: n = 1.25 kN/m3): Unit weight of concrete

= 9.81(kN/m3) : Unit weight of water

2.2.1 Standard load at longitudinal bridge in service limit state

■ Standard Axial load at longitudinal bridge:

■ Standard Lateral load at longitudinal bridge:

■ Standard Moment at longitudinal bridge:

2.2.2 Designed load at longitudinal bridge in strength limit state

■ Designed axial load at longitudinal bridge

■ Designed lateral load at longitudinal bridge:

■ Designed moment at longitudinal bridge:

Table of combination of load at top of cap:

Load Unit Service Limit State Strength Limit State

III Axial Capacity

3.1 Axial bearing capacity of material of pile PR

Where:

o f’c: 28-day compressive strength of concrete

o Ast: area of cross-section of reinforced steel

o f’y: yield strength of steel

■ The factored bearing capacity of a pile: PR

Consider that pile bears compressive force only, the resistance force according tomaterial:

Where:

 : Resistance coefficient, = 1

 Ag: Gross area of cross-section of pile,

 Ast: Area of cross-section of reinforced steel,

 Calculated axial resistance load

 Nominal axial resistance load

Hence:

3.2 Bearing resistance of soil QR

With:

Where: Qp: Frictional tip resistance load(MPa)

qp : Unit frictional tip resistance load(MPa)

Qs : Frictional side resistance load(MPa)

qs : Unit side resistance load(MPa)

Ap: Area of pile’s tip(mm2)

As : Area of pile’s side(mm2)

:Resistance factor for tip resistance,

: Resistance factor for side resistance, Type of soil

Sand 1 0.45

3.2.1 Frictional Resistance Qs

 Methodology for calculating:

Cohensionless soil(sand): SPT method

Cohensive soil(clay): -method

 Cohensive soil:

Where:

Su: Undrained shear strength (Mpa), Su = Cuu

: Adhension factor applied for Su according to Tomlinson(1987) designed curve

Undrainedshearstrength(MPa)

Factor

Unitfrictionalsideresistanceload(MPa)

Areaofpile’sside(m2)

Frictionalsideresistanceload(kN)

: Corrected SPT blow count (blow/300mm)Correction process for SPT:

Using formula:

Where:

N: Uncorrected SPT blow count(blow/300mm)

: Vertical effective stress(MPa)

Calculated for :

Unit weight

of soil(kN/m3)

Unit weight

of water(kN/m3)

Specificgravity Void ratio

Saturatedunit weight(kN/m3)

Verticaleffectivestress(MPa)

UncorrectedSPT blow count(blow/300mm)

CorrectedSPT blow count(blow/300mm)

)

Unitfrictionalsideresistanceload(MPa)

Areaofpile’sside(m2)

Frictionalsideresistanceload(kN)

3.2.2 Load carrying capacity of the pile point Qp

The pile tip contacted with sand in layer 4, calculated Qp corresponding

and

Where:

Ap: Area of pile tip(mm2)

: Corrected SPT blow count(blow/300mm)

Limitingtipresistanceload(MPa)

Totalfrictional tipresistanceload(kN)

Factor

Calculatedfrictional tipresistanceload(kN)

4 0.2025 13.28915868 39.83794 806.7184 0.45 484.3898Soil bearing capacity:

3.3 Single Pile bearing capacity Ptt

IV Pile number and pile distribution in foundation:

4.1 Computing Pile number n:

Where:

N: Designed axial load at longitudinal bridge at strength limited state(kN)

Ptt : Single pile bearing capacity (kN)

Changing numbers: thus n = 12

4.2 Pile distribution

4.2.1 Arranging piles

Piles are arranged in square pattern on plan view, with parameter below:

The number of piles: n = 12

The number of pile’s line according to longitudinal direction: n = 3

The spacing between centre of piles responding to longitudinal direction:

a = 1400mm

The number of pile’s line according to cross section direction: n = 3

The spacing between centre of piles responding to horizontal direction:

b = 2700mm

Cap volume:

4.3 Loads transfer to cap

4.3.1 Loads in service limit state

■ Standard axial load at longitudinal bridge:

=

■ Standard lateral load at longitudinal bridge:

■ Standard moment at longitudinal bridge:

4.3.2 Loads in strength limit state

■ Designed axial load at longitudinal bridge:

■ Designed lateral load at longitudinal bridge:

■ Designed moment at longitudinal bridge:

Table of loads acting at the bottom of pile cap

Limit State

StrengthLimit State

V Checking Strength Limit State

5.1 Checking single pile axial resistance

Methodology: Using FB-Pier

Final Maximums for all load cases

Maximum pile forcesMax shear in 2

Maximum soil forcesMax axial soil

Where: Nmax: Max axial force

ΔN : Own weight of pile (kN)

Ptt : Single Pile bearing capacity (kN)

We have:

So,

=> Satisfied

5.2 Checking the axial bearing capacity of group pile:

Where:

Vc: Total compressive load of pile group

QR: Axial resistance of pile group

: Resistance factor of pile group

Qg: Nominal axial resistance of pile group.: Coefficient of resistance of

group piles in cohensive, cohensionless soil

: Nominal axial resistance of group piles in cohensive, cohensionless soil.Using interpolation method, we obtains

5.2.1 Clay soil

For calculate Qg, use formula below:

Where:

X: Width of pile group(m)

Y: Length of pile group(m)

Z: Depth of pile group(m)

: Average undrained shear strength along the depth of penetration of the piles(MPa).: Undrained shear strenth at the base of the group(MPa)

Nc: Ratio depends on Z/X

With Z/X<2.5, use formula:

Layer

Sum of resistance load for single

pile Equivalent group pile resistance loadResistance

VI Checking Service Limit State

6.1 Determine total consolidation settlement

Have: Db = 17(m) Equivalent footing inside and between layer 4 and layer 1 = Db =

: Settlement of pile group (mm).

q : Net foundation applied at 2Db/3 This figure is equal to the applied load us the top

of group devided by the area of equivalent footing and does not include the weight of piles andsoil between the piles (MPa)

N0 :Axial load at bottom of cap at service limit state,

S : Area of equivalent footing

X : Width of the pile group(m)

Db : Depth of embedment in the layer that provide support

D’ : Efective depth taken as 2Db/3 (mm)

: SPT blow count corrected for both the overburden and hammer effeciency effects(blow/300mm)

I: Influence factor of the effective group embedment

Have:

o Compute q:

The area of equivalent foundation:

So, the force

N160=13.28916 (from the previous table) at the tip of pile

o Calculate the settlement:

So, the settlement of pile group is 5.619mm

6.2 Checking pile head displacement

Methodology: Using FB-PIER

Maximum pile head displacementsMax

displacement

in axial

VII Strength of bars and pile joint

7.1 Computing and arranging vertical bar in pile

Total casting length: Lcd = 32 (m) Divined into 4 part, each part is 8m long

7.1.1 Computing maximum moment of lifting and pitching of pile

Maximum bending moment

Mtt = max (Mmax(1); Mmax(2))

In which:

• Pile lifting moment

Lifting hook position:

Lifting hook position b = 0.294Ld = 0.294 x 8 = 2.352 (m)

Maximum moment:

Thus:

Mtt = max (Mmax(1);Mmax(2)) = max (7.94 ; 13.72) = 13.723 (kN.m)

7.1.2 Caculating the number of reinforce bars needed

We choose reinforced rebar ASTM A615M include 8Ø 25 have f’c = 30MPa, fy = 414MPa arrange at the cross-section , calculate same as rectangular section with singlereinforcement bar( specifically square cross-section 450x450mm)

Essential nominal resistance moment:

The height of stress block:

Check the elastic condition:

 Satisfied

Calculating for area and arrange of steel

Choose reinforced rebar ASTM A615M include 8Ø 25 and total area iis 1530, and the thickness

of cover concrete( to centre of steel bar) is 65mm, the effective depth d’=385mm

Recalculate height of stress block:

Recalculate elastic condition:

 Satisfied

7.2 Reinforcement of the belt for the pile

Because the pile is mainly compressed, it is not necessary to review the strength of thebelt reinforcement Therefore, reinforcing steel bars are arranged according to the requirements

of structure

+ The head of each pile is arranged with belt step 50 mm on a length of 1350 mm

+ Next we arrange with reinforced belt step is 100 mm on a length of 1100mm

+ The remainder of each pile (middle section of the pile) is arranged with the pile step: 150mm

7.3 Detail of hard pile rod reinforcement

Steel pile nose with a diameter of 40, with a length of 100 mm

The protrusion of the pile tip is 50 mm

7.4 Reinforced wire rod

At the top of the pile lay a grid of reinforced concrete pile with a diameter of 6 mm,with mesh a = 50 x 50mm The net is arranged to ensure that the concrete pile is notdamaged due to local stress during pile driving

7.5 Steel stake head

The pile head is coated with a flat steel bar of 10mm thickness for the purpose ofprotecting the pile head from damage when piling and in addition it is also useful for bonding

piles during construction together

7.6 Steel hooks

Steel hooks are selected in diameter 22 Because of the rebar in the pile is very redundant

so we can always use hooked steel hook for hanging hooks, then we do not need to make thethird hook to create favorable conditions for construction and piling in yards

The distance from the beginning of each pile to each anchor is a = 1.6m = 1600 mm

VIII Joint construction

We use welded joints to connect the pile back together Joints must ensure that the jointstrength is equivalent to or greater than the strength of the pile at the jointed section

To connect the piles back together, we use 4 angle steel L-100x100x12 piles into thefour corners of the pile and then use the welding line to connect the two piles (for solid piles,square usually use welding joints For round piles, the tube is usually used to connect bolts Inaddition, to increase safety for joints, we use 4 steel plates 500x100x10mm is dabbed betweentwo angles to increase the length of joints Weld thiclmess =10 mm