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