Penyelidikan Tanah

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Tanah?

Fungsi Pondasi…

Menerima beban dari bangunan atas (upper structures) , memikul, melimpahkan & meratakan

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melimpahkan & meratakan ke lapisan tanah di bawahnya.

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Dense SandDense SandDense SandDense Sand

Dense SandDense SandDense SandDense Sand

Soft ClaySoft ClaySoft ClaySoft Clay

Leaning Tower of Pisa

Kesalahan menjadi monumen!

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Limit States

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ServiceabilityServiceabilityServiceabilityServiceability UltimateUltimateUltimateUltimate

Foundation FailureFoundation Failure

ForceForceRotational FailureRotational Failure

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Soil HeaveSoil Heave ResistanceResistance

Kriteria Perencanaan(Design Criteria)

1. Daya dukung ijin ≥ tegangan yang terjadi atau angka keamanan terhadap keruntuhan geser cukup

2. Penurunan yang terjadi ( total and

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2. Penurunan yang terjadi ( total and differential settlement) masih dalam batas yang diijinkan

3. Aman terhadap pengaruh luar misalnya penggerusan, dll

Tujuan Penyelidikan Tanah

1. Menentukan jenis dan kedalaman pondasi2. Mengevaluasi beban - daya dukung pondasi3. Memperkirakan penurunan4. Menetukan potential problem misal : tanah

ekspansif, tanah mudah longsor, (collapsible

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ekspansif, tanah mudah longsor, (collapsible soil) dll.

5. Memperkirakan air tanah6. Memperkirakan tekanan tanah lateral misal :

untuk dinding penahan tanah7. Menentukan cara pelaksanaan ( construction

method )

Penyelidikan Tanah untuk Pondasi

Geo-Laboratory~ for testing

Design Office~ for design & analysis

soil properties

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construction site

Pengujian Tanah (Soil Testing)

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� CONE PENETRATION TEST (CPT / SONDIR)

� STANDARD PENETRATION TEST (SPT)

� PLATE BEARING TEST� FIELD VANE SHEAR TEST� DLL.

Sifat Tanah

1. Sifat fisik (physical properties)� Ukuran butir� Liquid limt & plastic limit ( batas atterberg)� Kadar air� Unit Weight ( γ ), Specific Gravity Gs

� Dll.2. Sifat mekanis (mechanical properties) � parameter kuat

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2. Sifat mekanis (mechanical properties) � parameter kuat geser c, φ.

� Unconfined compression test (uji kuat tekan bebas)� Direct shear test (uji geser langsung)� Triaxial compression test (uji tekan 3 sumbu)� Vane shear test

3. Sifat kemampatan (compressibility characteristics)� Uji konsolidasi (oedometer test)

4. Sifat hidrolis (hydraulics properties)� Uji permeabilitas (constant head & falling head)

Pengujian Tanah

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Pengujian sample tanah di Laboratorium

Pengujian Tanah

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Pengujian sample tanah di Laboratorium

SPT: Automatic Trip Hammer

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Field Drilling and Sampling

� Air or Mud Rotary Drilling

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Angle Drilling

� Assess geologic features (dip, strike, joints, etc.)

� Foundation testing for bridge abutments.

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bridge abutments.

Confined Access/ Interior Drilling

� Limited Access Drill Rigs are small in size, but have the torque of many full size truck

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many full size truck rigs.

� Capability, boring depths, size, etc. vary

� Esp. useful for remedial sampling

4Exploration for abutments, bridges, docks, etc.

Offshore Drilling/ Barge Rig

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docks, etc.

Drilling: Continuous Flight Auger

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� Casing with outer spiral� Inner rod with plug/or pilot

assembly� For sampling, remove pilot

Drilling & SamplingHollow Stem Auger

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� For sampling, remove pilot assembly and insert sampler

� Typically 5ft sections, keyed, box & pin connections

� Maximum depth 60-150ft

Drilling & SamplingHollow Stem Auger

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Boring Locations

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Profil Tanah

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KEDALAMAN BOR

LEBAR BANGUNANJUMLAH TINGKAT/LANTAI

1 2 4 8 16

(m)KEDALAMAN BOR

(m)

30,5 3,4 6,1 10,1 16,2 24,1

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61 3,7 6,7 12,5 20,7 32,9

122 3,7 7 13,7 24,7 41,5

UNTUK BANGUNAN RUMAH SAKIT DAN PERKANTORAN, SOWERS AND SOWERS (1970) MENGUSULKAN :

Db = 3 S0,7 UNTUK BANGUNAN BAJA RINGAN DAN BETON SEMPIT

Db = 6 S0,7 UNTUK BANGUNAN BAJA BERAT DAN BETON LEBARDIMANA :

Db = KEDALAMAN BOR ( m )S = JUMLAH TINGKAT/ LANTAI

JARAK LOBANG BOR

JENIS PROYEK JARAK (m)

BANGUNAN TINGKAT 10 - 30

BANGUNAN INDUSTRI 1 LANTAI 20 - 60

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BANGUNAN INDUSTRI 1 LANTAI 20 - 60

JALAN RAYA 250 - 500

PERUMAHAN 250 - 500

BENDUNGAN DAN TANGGUL 40 - 80

Kedalaman & Jarak Bor

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PROFIL TANAH

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Standard Penetration Test (SPT)

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Standard Split Spoon Sampler

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� Thick wall (0.25in) cylinder

� Sampling tube is split along the length

� Hammered into the ground

SPT Correction Factors

60.0

NCCCEN RSBm

60 =

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• hammer efficiency (Em) …. Table 4.3

• bore hole diameter (CB)…….Table 4.4.

• sampler correction (CS) ……Table 4.4

• rod length (CR) ………Table 4.4

Cone Penetrometer

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CPT Truck

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Crawler Type CPT Truck

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Typical CPT Data

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Texas Cone PenetrometerDesign Charts

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N KONSISTENSIKUAT TEKAN BEBAS

qu (kN/m2)

0-2 SANGAT LUNAK 0-25

Hubungan Konsistensi Lempung-Nilai SPT N

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2-5 LUNAK 25-50

5-10 SEDANG 50-100

10-20 KAKU (STIFF) 100-200

20-30 SANGAT KAKU 200-400

>30 KERAS (HARD) >400

Hubungan N - Kepadatan Relatif, - ΦTanah Pasir.

NKEPADATAN RELATIF

Φ(o)

Dr (%)

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0-5 0-5 26-30

5-10 5-30 28-35

10-30 30-60 35-42

30-50 60-95 38-46

Hubungan Nilai N - φφφφ

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Hubungan Penyelidikan Tanah-Biaya

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Laporan Penyelidikan Tanah

1. Skope penyelidikan2. Deskripsi rencana bangunan3. Deskripsi lokasi4. Keadaan geologi

Detail eksplorasi lapangan (jumlah,

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5. Detail eksplorasi lapangan (jumlah, kedalaman , jenis boring)

6. Deskripsi lapisan tanah7. Kondisi muka air tanah8. Rekomendasi pondasi9. Kesimpulan dan batasan penyelidikan

tanah.

Lampiran

� Peta lokasi� Denah lokasi boring� Boring log

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� Boring log� Hasil uji laboratorium� Grafik lain yang perlu

Rekomendasi Pondasi

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Denah Lobang Bor

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Profil Tanah

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Belajar

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Jangan tunggu sampai menit terakhir.

Exams

My mama always said, “Exam is like a box of chocolates; you never know what you

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of chocolates; you never know what you are gonna get”