Transcript SIVA
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) 2 SIVA 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 Ultimate 4 SIVA Copyright 2001 Bearing Pressure Definitions Allowable Safe Bearing Pressure qasb < Fs (settlement) /uA/ y =q f.q 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 7 SIVA Copyright 2001 General Failure Local Shear Failure Punching Shear Failure 8 SIVA 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 : 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 SIVA Copyright 2001 Aplikasi Teori Daya Dukung KEMIRINGAN TERZAGHI MEYERHOF HANSEN VESIC BEBAN 0 MUKA TANAH 0 0 b b DASAR PONDASI 0 0 d d 13 SIVA Copyright 2001 Daya Dukung Terzaghi Anggapan-anggapan: 1. 2. 3. 4. 5. 6. 7. 8. Tanah homogen isotropik Mode keruntuhan pondasi adalah 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 SIVA Copyright 2001 Keseimbangan Gaya Keseimbangan gaya-gaya yang bekeja pada baji tanah (soil wedge) adalah: Qu.(2b).1 = - W + 2.CsinΦ + 2.Pp 15 SIVA Copyright 2001 1 q f cN c 1 DN q B 2 N 2 Strip footing 1 q f cN c 1DN q B 2 N 2 16 SIVA Copyright 2001 Faktor Daya Dukung Tanah Menurut Terzaghi dan Berbagai Nilai N yang Berbeda 17 SIVA Copyright 2001 Terzaghi Bearing Equation qu nett = c.Nc + p'o (Nq - 1) + 0.5B'N applies to strip footing Nc, Nq and N are functions of f, and are usually given in graphical form c, f and ' refer to soil properties in the failure zone below the footing p'o is the effective overburden pressure at the founding level shear strength contribution above footing level is ignored : conservative for deeper footings SIVA Copyright 2001 Terzaghi Bearing Equation qu nett = c.Nc + p'o (Nq - 1) + 0.5B'N Overburden p'o = 'o D B Failure Zone (depth 2B) Generalized soil strength : c, f Soil unit weight : ' (total or effective as applicable) (drainage as applicable) SIVA Copyright 2001 Adopt weighted average values ! Bearing Capacity Factors 20 SIVA Copyright 2001 Faktor daya dukung Terzaghi ae Nq ( 3 f ) tgf 4 2 a 2 2 cos ( 4 5 2 f 2 ) N c ( N q 1).ctgf N c 5,7 jika : f 0 N 2( N q 1).tgf 21 SIVA Copyright 2001 Faktor daya dukung Terzaghi Nq e .tgf f tg (45 ) 2 N c ( N q 1).ctgf 2 N c 5,7 jika : f 0 N 2( N q 1).tgf 22 SIVA Copyright 2001 Faktor Daya Dukung Bearing capacity factors 23 SIVA Copyright 2001 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 24 SIVA Copyright 2001 Faktor Daya Dukung Bearing Capacity Factor 1000 100 Nc Nq N Nq = 33 Nc = 10 10 1 0.1 SIVA N = 250 14o 0 Copyright 2001 10 46o 35o 20 30 Friction Angle (deg) 40 50 Persamaan Daya Dukung Meyerhof qu = c.Ncscdcic + q.Nqsqdqiq + 0.5BNsdi Bearing Capacity for soil •• Correction factors Factors for footing shape (s), f cohesion, surcharge and weight footing depth (d) and load inclination (i ). Dfof friction angle, f q = .Df functions •• determine from appropriate equations c • determine by equation B or from graph soil density, , (kN/m3) SIVA Copyright 2001 Faktor daya dukung Meyerhof Nq e .tgf tg (45 2 N c ( N q 1).ctgf f 2 ) N c 5,14 jika : f 0 N ( N q 1).tg (1,4.f ) 27 SIVA Copyright 2001 Faktor daya dukung Hansen Nq e .tgf f tg (45 ) 2 N c ( N q 1).ctgf 2 N c 5,14 jika : f 0 N 1,5( N q 1).tgf 28 SIVA Copyright 2001 Faktor daya dukung Vesic Nq e .tgf f tg (45 ) 2 N c ( N q 1).ctgf 2 N c 5,14 jika : f 0 N 2( N q 1).tgf 29 SIVA Copyright 2001 Pengaruh Muka air 30 SIVA Copyright 2001 Pondasi dengan Beban Momen M P e P e=M P ekivalen eksentrisitas beban SIVA Copyright 2001 Cara Meyerhof menentukan eksentrisitas beban L e B P 2e SIVA Copyright 2001 L' = L- 2e Eksentrisitas 2 arah L 2e2 B e2 P 2e1 SIVA Copyright 2001 L' = L- 2e1 B' = B- 2e2 e1 Daya Dukung Berdasar Data Uji Lapangan (In Situ Test) Plate Bearing Test (Uji Pembebanan Pelat) Standard Penetration Test (SPT) Cone Penetration Test/CPT (Sondir) 34 SIVA Copyright 2001 Plate Load Tests 35 SIVA Copyright 2001 Plate Bearing Test (Uji Pembebanan Pelat) Tanah dengan kekuatan konstan qu qu , p B < 4 Bp Tanah Dengan Kekuatan Meningkat Secara Linear Thd Kedalaman B < 4 Bp qu qu , p Ekstrapolasi Hasil Uji Penurunan Terzaghi & Peck. q q1 i 1,5 SIVA B Bp Copyright 2001 36 Standard Penetration Test (SPT) PONDASI TELAPAK (FOOTING) MEYERHOF (1956,1974) N B 4 ft qa ,1 n K d F1 N B F3 B 4 ft qa ,1 n F2 B 2 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 PONDASI PELAT (MAT/RAFT) N qa ,1 n K d F3 qa qa,1 37 SIVA Copyright 2001 Cone Penetration Test/CPT (Sondir) SCHMERTMANN (1978) 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 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/cm2 38 SIVA Copyright 2001 Belajar Jangan tunggu sampai menit terakhir. 39 SIVA Copyright 2001 Exams My mama always said, “Exam is like a box of chocolates; you never know what you are gonna get” 40 SIVA Copyright 2001