slop stabilization pertemuan 8 - 10 mata kuliah: s0892 – ground improvement method tahun: 2010

Slop StabilizationPertemuan 8 - 10

Mata kuliah : S0892 – Ground Improvement MethodTahun : 2010

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COURSE 3

Content:• Problems On slope• Stabilization Methods:

– Soil Nailing– Retaining Wall– Reinforcement

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PROBLEMS ON SLOPE

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SLOPE FAILURE

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FAILURE TYPE

• ROTATIONAL

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FAILURE TYPE• TRANSLATIONAL

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FAILURE TYPE

• FALLING

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FAILURE TYPE

• BLOCK SLIDE

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FAILURE TYPE

• TOPPLE

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FAILURE TYPE

• FLOW

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PROBLEMS ON SLOPE

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STABILIZATION METHODS

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STABILIZATION METHODS• SOIL NAILING

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SOIL NAILINGDEFINITION

• Soil nailing is a technique in which soil slopes, excavations or retaining walls are reinforced by the insertion of relatively slender elements - normally steel reinforcing bars.

• The bars are usually installed into a pre-drilled hole and then grouted into place or drilled and grouted simultaneously.

• They are usually installed untensioned at a slight downward inclination. A rigid or flexible facing (often pneumatically applied concrete otherwise known as shotcrete) or isolated soil nail heads may be used at the surface.

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SOIL NAILING

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SOIL NAILINGBASIC PRINCIPLE

• The basic concept of soil nailing is to reinforce and strengthen the existing ground by installing closely spaced steel bars, called "nails," into a slope or excavation as construction proceeds from the "top down."

• This process creates a reinforced section that is itself stable and able to retain the ground behind it. The reinforcements are passive and develop their reinforcing action through nail ground interactions as the ground deforms both during and following construction.

• Nails work predominantly in tension, but are considered by some to also work in bending/shear under certain circumstances.

• Generally, the soil nails significantly increase the apparent cohesion of the soil through their ability to carry tensile loads.

• A construction facing is also usually required, and is typically shotcrete reinforced by welded wire mesh. For permanent walls, the shotcrete construction facing is typically covered in cast-in-place concrete facing.

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SOIL NAILING

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SOIL NAILING• Nails work predominantly in tension but may develop bending/shear in certain circumstances. The effect of

the nail reinforcement is to improve stability by (a) increasing the normal force and hence the soil shear resistance along potential slip surfaces in frictional soils; and (b) reducing the driving force along potential slip surfaces in both frictional and cohesive soils. A construction facing is also usually required and is typically shotcrete

reinforced by welded wire mesh. • The steel nail bars are typically 20 to 35 mm in diameter, with a yield strength in the range of 420 to 500

N/mm2, and are typically installed into drillholes having diameters in the range of 100 mm to 300 mm and at a spacing between 1 and 2 meters.

• The nail lengths are typically 70 to 100 percent of the wall height. • Nail inclinations are generally on the order of 15 degrees below horizontal to facilitate grouting.• Soil nails typically consist of steel reinforcement inclusions and may be categorized on the basis of their

method of installation and degree of corrosion protection. For conventional drill and grout nail installations, the nail grout consists typically of a neat cement grout with a watercement ratio of about 0.4 to 0.5. Where a stiffer consistency grout is required (e.g., to centralize the nail when no centralizers are used in a hollow stem auger installation or to control leakage of grout into the ground such as in highly permeable granular soils or highly fractured rock),

• a lower slump sand-cement grout may be used. Sand-cement grout may also be used in conjunction with large nail holes for economic reasons.

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SOIL NAILING

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SOIL NAILING – CONSTRUCTION

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RETAINING WALLS

A retaining wall is a structure that holds back soil or rock from a building, structure or area. Retaining walls prevent downslope movement or erosion and provide support for vertical or near-vertical grade changes

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RETAINING WALLS

11

2 2

3 31

1

2 2

3 3

PA

PA

PA

PA

PPPP

PPPP

S

S

S

Stoe

toe

toe

toeR

R

R

Ryy

yy

Safety against sliding along the base

tan }.{

A

iPsliding P

WPF

HH

hh

soil-concrete friction angle 0.5 – 0.7 soil-concrete friction angle 0.5 – 0.7

to be greater than 1.5


PP= 0.5 KPh2PP= 0.5 KPh2 PA= 0.5 KAH2PA= 0.5 KAH2

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RETAINING WALLS

11

2 2

3 31

1

2 2

3 3

PA

PA

PA

PA

PPPP

PPPP

S

S

S

Stoe

toe

toe

toeR

R

R

Ryy

yy

Safety against overturning about toe

H/3

}{3/

A

iiPgoverturnin P

xWhPF

HH

hh



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RETAINING WALLS

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REINFORCEMENT

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REINFORCEMENT

45 0+ /2

H

LR LE

Lo

Sv

z

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REINFORCEMENT

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REINFORCEMENT

OVERTURNING STABILITY, FS 2 SLIDING STABILITY, FS 1.5

BEARING CAPACITY STABILITY,

FS 3