Daya Dukung Bearing Capacity Tanah kuat batuan rock
Daya Dukung (Bearing Capacity) Tanah kuat batuan (rock) SIVA 1
Pondasi Dangkal ~ untuk melimpahkan beban ke lapisan di bawahnya ~ utamanya untuk tanah kuat atau beban ringan Tanah kuat batuan (rock) SIVA 2 Copyright 2001
Footing Performance Vertical Load Vertical movement safe load SIVA Elastic maximum tolerable settlement maximum service ultimate capacity load Plastic Ultimate Limit State Serviceability Limit State Maximum allowable load = min [safe load, max service load ] Copyright 2001 Plunging Failure
Limit States Serviceability SIVA Ultimate 4 Copyright 2001
Bearing Pressure Definitions Allowable Safe Bearing Pressure qasb < =q F. q /u A/ y s (settlement) F Plan Area, A Ultimate Bearing Capacity qu = Ffail / A SIVA Copyright 2001
Foundation Failure SIVA Rotational Failure Force Soil Heave Resistance Copyright 2001
Pola Keruntuhan General Failure Local Shear Failure Punching Shear Failure SIVA 7 Copyright 2001
General Failure Local Shear Failure Punching Shear Failure SIVA 8 Copyright 2001
FOUNDATION FAILURE 1. Generalized Shear Failure q Soil Failure Lines Settlement passive rigid radial shear SIVA Copyright 2001 log spiral
Perhitungan Daya Dukung Untuk menghitung daya dukung dapat dilakukan dengan analisisis berdasarkan : n n SIVA Data Uji Laboratorium: Teori Terzaghi Teori Meyerhof Teori Brinch Hansen Teori Vesic Data Uji Lapangan : Plate Bearing Test Cone Penetration Test/CPT (Sondir Standard Penetration Test/SPT 12 Copyright 2001
Aplikasi Teori Daya Dukung KEMIRINGAN SIVA TERZAGHI MEYERHOF HANSEN VESIC BEBAN 0 MUKA TANAH 0 0 b b DASAR PONDASI 0 0 d d 13 Copyright 2001
Daya Dukung Terzaghi Anggapan-anggapan: 1. 2. 3. 4. 5. 6. 7. 8. SIVA Tanah homogen isotropik Mode keruntuhan pondasi adalah general shear failure Pondasi adalah strip dengan permukaan bawah kasar Bidang keruntuhan geser diatas permukaan tanah diabaikan Permukaan tanah adalah horizontal Tidak terdapat gaya horizontal, momen dan eksentrisitas Pondasi terletak pada kedalaman D<B Daerah elastis mempunyai sudut batas yang lurus dengan bid. horizontal 14 Copyright 2001
Keseimbangan Gaya Keseimbangan gaya-gaya yang bekeja pada baji tanah (soil wedge) adalah: Qu. (2 b). 1 = - W + 2. CsinΦ + 2. Pp SIVA 15 Copyright 2001
Strip footing SIVA 16 Copyright 2001
Faktor Daya Dukung Tanah Menurut Terzaghi dan Berbagai Nilai N yang Berbeda SIVA 17 Copyright 2001
Terzaghi Bearing Equation qu nett = c. Nc + p'o (Nq - 1) + 0. 5 B 'N applies to strip footing u Nc, Nq and N are functions of f, and are usually given in graphical form u c, f and ' refer to soil properties in the failure zone below the footing u p'o is the effective overburden pressure at the founding level u shear strength contribution above footing level is ignored : conservative for deeper footings u SIVA Copyright 2001
Terzaghi Bearing Equation qu nett = c. Nc + p'o (Nq - 1) + 0. 5 B 'N Overburden p'o = 'o D B Failure Zone (depth 2 B) Generalized soil strength : c, Soil unit weight : ' (total or effective as applicable) (drainage as applicable) SIVA Copyright 2001 Adopt weighted average values !
Bearing Capacity Factors SIVA 20 Copyright 2001
Faktor daya dukung Terzaghi SIVA 21 Copyright 2001
Faktor daya dukung Terzaghi SIVA 22 Copyright 2001
Faktor Daya Dukung Bearing capacity factors SIVA Copyright 2001 23
Rumus Umum Daya Dukung Secara umum daya dukung dapat ditulis sbb: qu = c. c Nc + q. D. Nq + . 0, 5 B. N dimana: c, q, = faktor koreksi yang tergantung pada bentuk, kedalaman, kemiringan: beban, muka tanah, dasar pondasi SIVA 24 Copyright 2001
Faktor Daya Dukung Bearing Capacity Factor 1000 100 Nc Nq Ng Nq = 33 Nc = 10 10 1 0. 1 SIVA N = 250 14 o 0 Copyright 2001 10 46 o 35 o 20 30 Friction Angle (deg) 40 50
Persamaan Daya Dukung Meyerhof qu = c. N c. c. N Ncscdcic + q. N q. q. N Nqsqdqiq + 0. 5 BN B N s d i Bearing Capacity for soil • • Correction factors Factors for footing shape (s), cohesion, surcharge footing depth (d) and loadweight inclination (i ). Dfof friction angle, q = . Df • functions • determine from appropriate equations c • determine by equation B or from graph soil density, , (k. N/m 3) SIVA Copyright 2001
Faktor daya dukung Meyerhof SIVA 27 Copyright 2001
Faktor daya dukung Hansen SIVA 28 Copyright 2001
Faktor daya dukung Vesic SIVA 29 Copyright 2001
Pengaruh Muka air SIVA 30 Copyright 2001
Pondasi dengan Beban Momen M P e=M P ekivalen eksentrisitas beban SIVA Copyright 2001
Cara Meyerhof menentukan eksentrisitas beban L e P 2 e SIVA Copyright 2001 L' = L- 2 e B
Eksentrisitas 2 arah L 2 e 2 B e 2 P 2 e 1 SIVA Copyright 2001 L ' = L - 2 e 1 B' = B- 2 e 1
Daya Dukung Berdasar Data Uji Lapangan (In Situ Test) Plate Bearing Test (Uji Pembebanan Pelat) n Standard Penetration Test (SPT) n Cone Penetration Test/CPT (Sondir) n SIVA 34 Copyright 2001
Plate Load Tests SIVA 35 Copyright 2001
Plate Bearing Test (Uji Pembebanan Pelat) n Tanah dengan kekuatan konstan B < 4 Bp n Tanah Dengan Kekuatan Meningkat Secara Linear Thd Kedalaman B < 4 Bp n SIVA Ekstrapolasi Hasil Uji Penurunan Terzaghi & Peck. 36 Copyright 2001
Standard Penetration Test (SPT) n PONDASI TELAPAK (FOOTING) MEYERHOF (1956, 1974) Dimana : qa, 1 = daya dukung ijin utk penurunan 1 inchi Kd = 1+0, 33 D/B≤ 1, 33 Nn = SPT yang dikoreksi F = faktor tergantung energi pukulan SPT n SIVA PONDASI PELAT (MAT/RAFT) 37 Copyright 2001
Cone Penetration Test/CPT (Sondir) SCHMERTMANN (1978) n DAYA DUKUNG BATAS PADA TANAH NON KOHESIF MENERUS : qu = 28 – 0, 0052(300 -qc)1, 5 BUJUR SANGKAR : qu = 48 – 0, 0090(300 -qc)1, 5 n DAYA DUKUNG BATAS PADA TANAH KOHESIF MENERUS : qu = 2 + 0, 28 qc BUJUR SANGKAR : qu = 5 + 0, 34 qc qu dan qc dalam tsf atau kg/cm 2 SIVA 38 Copyright 2001
Belajar Jangan tunggu sampai menit terakhir. SIVA 39 Copyright 2001
Exam s My mama always said, “Exam is like a box of chocolates; you never know what you are gonna get” SIVA 40 Copyright 2001
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