Part 1_ Slope Stability

Slope stability

SLOPE STABILITY

SLOPE STABILITY

Mata kuliah TIMBUNAN DAN KONSTRUKSI PENAHAN TANAH (RC14-1354)


SLOPE STABILITY

SLOPE STABILITY



FLOW CHARTFLOW CHART

SLOPE STABILITY

(2)

RETAINING WALL

(3)

SOIL SHEAR STRENGT

(1)

SHEETPILE (4)

SHALLOW FOUNDATION

(5)

DEEP FOUNDATION

(6)

OUTLINEOUTLINE

• Common landslide case in the word Indonesia

• Infinite slope analysis without and with water seepage

• Finite slope analysis (Cullman, Fellenius, Bishop Method)

• Slope stability calculation using x-stable and Slope/w

Why do we need to learn slope stability?Slope stability involves analysis whether a slope

of soil is safe or not, and how to possibly enhance the stability of the slope

UNRESTRAINED SLOPE

If the soil surface are rugged then:gravity component of the soil will tend to drive the

ground downward even to allow the landslide

SLOPE STABILITY

SLOPE STABILITY



R.L. Schuster, U.S. Geological Survey

Types of slopes• Natural– Valleys, hills– Coastal and river

• Man-made– Cuttings and embankments– Temporary excavations–Waste heaps (landfill slopes)

SLOPE STABILITY

SLOPE STABILITY



• Infinite slope (unlimited high)• Finite slope (limited high)

SLOPE STABILITY

SLOPE STABILITY



Types of slopes

Landslide in Berau, Kalimantan

• 24 Mei 2012• Triggered by heavy

rainfall, river scouring at the river bend area.

• Potential solution: relocate the road and better land use regulation.

SLOPE STABILITY

SLOPE STABILITY



Landslide of Porong highway

SLOPE STABILITY

SLOPE STABILITY



• 18 March 2014• Triggered by heavy

rainfall, construction errors.

• Potential solution: Designed a new embankment reinforcement.

Causes of Slope failure• Gravity• Seepage• Earthquake• Erosion• Construction• Slope failures can depend on:

– Soil type– Soil Stratification– Ground water– Seepage– Slope geometry

SLOPE STABILITY

SLOPE STABILITY



Signs of unstable slopes and ready to landslides

SLOPE STABILITY

SLOPE STABILITY



Shelby, 1993Shelby, 1993

Slope Stability• Safety Factor: = Resisting/Driving Forces

If SF >1, then safe or stable slopeIf SF <1, then unsafe or unstable slope

• Driving and resisting force variables:– Slip surface – “plane of weakness”– Type of Earth materials– Slope angle and topography– Climate, vegetation, and water– Shaking

• Causes vs. triggers

SLOPE STABILITY

SLOPE STABILITY



WT

PA = PB konstan

W = berat pias tanah

R = reaksi tanah didasarInfinite Slope without seepage

SLOPE STABILITY

SLOPE STABILITY



SLOPE STABILITY

SLOPE STABILITY



Rumus Infinite Slope Tanpa Aliran

• W = L H • Na = W cos β = LH cos β• Ta = W sin β = LH sin β

d=

SLOPE STABILITY

SLOPE STABILITY



Rumus Infinite Slope Tanpa Aliran

Maka,

SLOPE STABILITY

SLOPE STABILITY



Infinite Slope dengan aliran (1)

SLOPE STABILITY

SLOPE STABILITY



Infinite Slope dengan aliran (2)

SLOPE STABILITY

SLOPE STABILITY



Rumus Infinite Slope Dengan Aliran

• W = L H ϒsat• Na = W cos β = LHϒsat cos β• Ta = W sin β = LHϒsat sin β

σN’ = N’/A

SLOPE STABILITY

SLOPE STABILITY



Rumus Infinite Slope Dengan Aliran

Maka,

1. METODE CULMANN

=45 + f/2

SLOPE STABILITY

SLOPE STABILITY



SLOPE STABILITY

SLOPE STABILITY



cos1

cossin4cHCR

SLOPE STABILITY

SLOPE STABILITY



1. METODE CULMANN

SLOPE STABILITY

SLOPE STABILITY



1. METODE CULMANN

SLOPE STABILITY

SLOPE STABILITY



1. METODE CULMANN

Tentukan Bidang Longsor Kritis dengan cara menentukan harga sudut . Turunkan cd terhadap kemudian sama dengankan 0 , H dan konstan

Harga yang kritis:

2d

cr

SLOPE STABILITY

SLOPE STABILITY



METODE CULMANN

METODE CULMANN

2d

cr

SLOPE STABILITY

SLOPE STABILITY



SLOPE STABILITY

SLOPE STABILITY



Terzaghi & Peck

Stability Number

Terzaghi & Peck, 1967

SLOPE STABILITY

SLOPE STABILITY



m

cH uCR

SLOPE STABILITY

SLOPE STABILITY



Terzaghi & Peck, 1967

SLOPE STABILITY

SLOPE STABILITY



Metode Fellenius

TIMBUNAN DIATAS LEMPUNG LUNAK ( U = 0, CU)

3. Metode Fellenius

SLOPE STABILITY

SLOPE STABILITY



SLOPE STABILITY

SLOPE STABILITY



2 1cos

1

1

' cos '

sin

i

n

i i i i i

n

i i

c b w u b tgF

w

p

nNN

p

nNNN

W

WLCFS

1

1

sin.

tan.cos..

p

nNN

p

nNNNN

W

LUWLCFS

1

1

sin.

'tan]..cos.['.

• Short Term Lempung :

• Long Term lempung, Long Term dan Short Term Pasir :

SLOPE STABILITY

SLOPE STABILITY



Metode Bishop

4. Metode Irisan BISHOP yang Disederhanakan

SLOPE STABILITY

SLOPE STABILITY



Gambar : Analisa Stabilitas dg Metoda Irisan yg biasa untuk Talud pada Tanah yg Berlapis

C

A

SLOPE STABILITY

SLOPE STABILITY



Gambar : Gaya – gaya yang bekerja pada irisan (a) ; Poligon gaya keseimbangan (b)

SLOPE STABILITY

SLOPE STABILITY



𝑇 𝑟=𝑁𝑟 ¿Dari gambar di atas, diperoleh :

𝑊𝑛+∆𝑇=𝑁𝑟 cos𝛼𝑛+[𝑁𝑟 tan∅𝐹𝑠

+𝑐 ∆ 𝐿𝑛

𝐹𝑠 ]sin𝛼𝑛

Pada gambar (b) menunjukkan keseimbangan dari irisan nomor n. Jumlahkan gaya dalam arah vertikal

Atau,

𝑁𝑟=𝑐+∆𝑇 −

𝑐 .∆ 𝐿𝑛

𝐹𝑠sin𝛼𝑛

cos𝛼𝑛+tan∅ .sin 𝛼𝑛

𝐹𝑠

(1)

(2)

SLOPE STABILITY

SLOPE STABILITY



Untuk keseimbangan blok ABC, ambil momen terhadap O

Dengan,

∑𝑛=1

𝑛=𝑝

𝑤𝑛𝑟 sin 𝛼𝑛=∑𝑛=1

𝑛=𝑝

𝑇 𝑟 𝑟

𝑇 𝑟=1𝐹𝑠

¿

¿1𝐹 𝑠

¿

(3)

(4)

SLOPE STABILITY

SLOPE STABILITY



Masukkan Persamaan (2) dan (4) ke persamaan (3), sehingga,

(5)

𝑚𝛼 (𝑛)=cos𝛼𝑛+tan∅ . sin𝛼𝑛

𝐹𝑠

𝐹 𝑠=∑𝑛=1

𝑛=𝑝

¿¿¿ ¿

Masukkan Persamaan (2) dan (4) ke persamaan (3), sehingga,

Fs harus dicoba keduanya (Trial & Error)

SLOPE STABILITY

SLOPE STABILITY



𝐹 𝑠=∑𝑛=1

𝑛=𝑝

¿¿¿ ¿

Misal ΔT = 0, maka Persamaan (5) menjadi,

(6)

SLOPE STABILITY

SLOPE STABILITY



Xstabl

SLOPE STABILITY

SLOPE STABILITY



Contoh Data Tanah

No Parameter Tanah Kedalaman (m)

0-2 2-4 4-6

1 Berat Volume ( t/m3) 1.6 1.8 1.8

2 Kohesi ( t/m2) 0.7 0.2 0.2

3 Sudut Geser Dalam 10.2 22.09 22.09

SLOPE STABILITY

SLOPE STABILITY



Contoh Data Timbunan

H = 6 meter

SLOPE STABILITY

SLOPE STABILITY



Input Data ke Program Xstabl

Diganti Metric (Menunjukkan Satuan)

1. Buka Program Xstable

SLOPE STABILITY

SLOPE STABILITY




2. Memasukkan segmen tanah dan soil unit

SLOPE STABILITY

SLOPE STABILITY




SLOPE STABILITY

SLOPE STABILITY




3. Setelah input segmen dan soil unit, maka hasilnya sebagai berikut :

Segmen

SLOPE STABILITY

SLOPE STABILITY




4. Lanjutkan lagi untuk input data segmen pada tanah dibawah timbunan (subsurface)

SLOPE STABILITY

SLOPE STABILITY




5. Isikan data setiap segment number dan jenis tanahnya

SLOPE STABILITY

SLOPE STABILITY




6. Selanjutnya akan didapat tampilan sebagai berikut

SLOPE STABILITY

SLOPE STABILITY




Nomor Soil Unit

12

43

5

Segmen

SLOPE STABILITY

SLOPE STABILITY




7. Selanjutnya input parameter data tanah dan timbunan yang diketahui

SLOPE STABILITY

SLOPE STABILITY




Tampilan hasil input parameter tanah

SLOPE STABILITY

SLOPE STABILITY



8. Isi data permukaan airnya, maka secara otomatis akan muncul seperti berikut ini

SLOPE STABILITY

SLOPE STABILITY



8. Type of water surface dipilih “Phreatic”

SLOPE STABILITY

SLOPE STABILITY



9. Diasumsikan MAT sepanjang soil unit 1, sehingga x coord dan y coord diisi sesuai segmen soil unit 1

1

SegmenSoil unit

MAT sepanjang soil unit 1

SLOPE STABILITY

SLOPE STABILITY



Input data untuk x coord dan y coord pada water surface

SLOPE STABILITY

SLOPE STABILITY



10. Selanjutnya menganalisis bidang kelongsoran pada data tanah yang telah diinput

SLOPE STABILITY

SLOPE STABILITY



Input data pada analisis circular surface

SLOPE STABILITY

SLOPE STABILITY



Termination Points

Initiation Points

SLOPE STABILITY

SLOPE STABILITY



11. Setelah itu masukkan beban dengan asumsi beban 10 kpa

SLOPE STABILITY

SLOPE STABILITY



12. Setelah meng input semua data , selanjut me run program xstabl (Stability Analysis)

SLOPE STABILITY

SLOPE STABILITY



Hasilnya...

SLOPE STABILITY

SLOPE STABILITY



Hasilnya...

Beban

Hasil input Initatiation & Termination Points (Bentuk bidang longsornya)

SLOPE STABILITY

SLOPE STABILITY



Sehingga didapat nilai FS

SLOPE STABILITY

SLOPE STABILITY



Nilai FS = 0,904

Hasil output dari program xstabl untuk mengetahui hasil analisisnya dapat dilihat disini

SLOPE STABILITY

SLOPE STABILITY



TERIMA KASIH

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Part 1_ Slope Stability