Mektan-I-4 Soil Classification - Exercise

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<p>Diskripsi Singkat (GBPP)Mata kuliah ini membahas tentang: 1. Pengenalan umum (permasalahan dan aplikasi mekanika tanah), 2. Tanah dan proses pembentukannya, 3. Sifat indeks (kadar air, berat jenis, berat satuan, angka pori, derajat kejenuhan, analisis ukuran butir, batas Atterberg) 4. Klasifikasi tanah (BS, ASTM, AASHTO), 5. Pemadatan (laboratorium &amp; lapangan, kontrol kepadatan), 6. Tegangan dalam tanah, 7. Rembesan (permeabilitas, uji permeabilitas laboratorium &amp; lapangan; tanah berlapis/anisotropis, flownet, tekanan rembesan, rembesan pada bendungan tanah, filter), 8. Pengenalan kuat geser tanah.</p> <p>Contoh soal1. Butiran tanah tinggal dalam saringan no. 4 = 91% atau lolos saringan no. 4 = 9% dan hanya 4% lolos saringan no. 200. Koefisien keseragaman Cu = 8, koefisien gradasi Cc = 4 dan indeks plastisitas PI = 3 %</p> <p>-</p> <p>Tanah yang tinggal dalam saringan no. 4 = 91 %, maka tanah kerikil (G). Karena lolos saringan no. 200 = 4%, maka harus diperiksa gradasinya. Diketahui Cu = 8 &gt; 4 dan Cc = 4 &gt; 3, maka tanah bergradasi buruk (P)Tanah termasuk klasifikasi GP</p> <p>-</p> <p>Contoh soal2. Butiran lolos saringan no. 200 (0,075 mm) = 65%; batas cair LL = 40%, dan batas plastis = 22%.</p> <p>- Tanah lolos saringan no. 200 = 65% &gt; 50%, maka termasuk berbutir halus. - LL = 40% &lt; 50%, maka harus diperiksa PI-nya - PI = LL PL = 40% - 22% = 18% &gt; 7%, - Menurut grafik plastisitas tanah adalah CL.</p> <p>Contoh soal3. Butir tanah lolos saringan no. 200 = 51%, batas cair LL = 53%, batas plastis PL = 40%, tanah anorganik</p> <p>Contoh soal4. Hasil uji lab : LL = 41% dan PL = 14%. Hasil analisis saringan:No. Saringan 4 % butiran lolos 100</p> <p>1040 200</p> <p>92,979,4 59,1</p> <p>Klasifikasikan tanah menurut: USCS</p> <p>Example :Soil A : Cu = 34, Cc = 1.6, fines 0 % , gravel : sand = 76 : 24</p> <p>Soil B : Cu = 800, Cc = 0.25, fines 34 % , gravel : sand = 41 : 25, LL = 26 %, PI = 9 %Soil C : fines 95 % , LL = 42 %, PL = 24 %, PI = 18 %</p> <p>Soil D : Cu = 1.8, Cc = 0.95, fines 8 % , gravel : sand = 4 : 96 LL = 25 %, PL = 19 %, Soil E : fines 75 % , LL = 40 %, PL = 20 %, gravel : sand = 35 : 65Find classification of these soils (USCS) Cu = D60/D10</p> <p>Cc = D302/(D10*D60)</p> <p>Soil Classification (Bristish Standard)Klasifikasi : pengelompokan tanah berdasar karakteristik material (gradasi butir dan plastisitas), tidak tergantung kondisi lapanganKelompok tanah group symbols : Huruf pokok Huruf diskripsi/kualifikasi Huruf pokok : G = gravel, S = sand, M = silt, C = clay atau F = fine-soil (fines) Pt = peat (humus/gambut)</p> <p>Huruf diskripsi/kualifikasiW = well graded P = poorly graded : Pu = uniform graded Pg = gap graded</p> <p>L = low plasticity I = intermediate plasticity H = high plasticity V = very high plasticity E = extremely high plasticity range O = organic</p> <p>Soil A : Cu = 34, CZ = 1.6, fines 0 % , gravel : sand = 76 : 24 Coarse fraction = 100 % GRAVEL / SAND Gravel : sand = 76 : 24 GRAVEL (G)</p> <p> Cu = 34 &gt; (4 - 6) CZ = 1.6 (1 - 3)well graded (W)</p> <p> Soil A : GW = well graded sandy GRAVEL</p> <p>Soil B : Cu = 1.8, CZ = 0.95, fines 3 % , gravel : sand = 4 : 96 Fines = 3 % coarse grained soil</p> <p> Gravel : Sand = 4 : 96 SAND (S) Cu = 1.8 &lt; (4 - 6) CZ = 0.95 ( 1 - 3)</p> <p>poorly graded Cu = 1.8 uniform</p> <p> Soil B : SPu uniform slightly silty SAND</p> <p>Soil C : Cu = 800, CZ = 0.25, fines 34 % , gravel : sand = 41 : 25, LL = 26 %, PI = 9 % Fines = 34 % coarse grained soil Gravel : Sand = 41 : 25 GRAVEL (G)</p> <p> Fines = 34 % (15 - 35 %) very silty/clayey use plasticity chart :LL = 26 % PI = 9 % above-A line C LL &lt; 35 % L</p> <p> Soil C : GCL = very clayey GRAVEL (clay of low plasticity)</p> <p>Soil D : fines 95 % , LL = 42 %, PL = 24 %, PI = 18 Fines 95 % SILT/CLAY</p> <p> Use Plasticity chartLL = 42 % &amp; PI = 18 % above-A line C LL = 42 % (35 - 50 %) I</p> <p> Soil D CI : CLAY of intermediate plasticity</p> <p>Note : 1. If detail is not required liquid limit in plasticity chart 2 parts L or U (I, H,V, E) U = The upper plasticity range 2. First letter dominant soil fraction name of soil Example : SW = well graded SAND SCL= very clayey SAND of low plasticity CIS = intermediate plasticity sandy CLAY MHSO = sandy organic SILT of high plasticity 3. Classification (symbol) suggested sub-group symbol if possible 4. Symbol F could be used when clay (C) or silt (M) is not an important consideration. 5. The presence of COBBLES (Cb) &amp; BOULDERS (B) presented using + GW + Cb : well graded GRAVEL with COBBLES B + CL : BOULDERS with low plasticity CLAY</p> <p>SOIL DESCRIPTION detail materials &amp; characteristics of soil mass Example of soil description at field : Dense, reddish-brown, subangular, well graded, gravelly SAND</p> <p> Dense, brown, heterogeneous, well graded, very silty SAND and GRAVEL with some COBBLES. Stiff, brown, closely fissured CLAY of high plasticity London clay.</p> <p> Spongy, dark brown, fibrous PEAT</p> <p>AASHTO Designation : M - 145 (1982)Coarse grained soil &gt; 0.075 mm</p> <p>Fine grained soil &lt; 0.075 mm.Granular soils : fine fraction &lt; 35 % Silt - Clay materials : fine fraction &gt; 35 % Soil classified into groups and sub-groups Granular materials : A1 A-1-a A-1-b A-3 A-2 A - 2 - 4, A - 2 - 5,</p> <p>A - 2 - 6,</p> <p>A-27</p> <p>Silt - Clay material : A - 4, A - 5, A - 6 A - 7 A - 7 - 5, A - 7 - 6 Highly organic soil (peat) visual identification A - 8 not suitable for embankment/subgrade</p> <p>AASHTO Soil Classification System The AASHTO Soil Classification System was developed by the American Association of State Highway and Transportation Officials, It is used as a guide for the classification of soils and soilaggregate mixtures for highway construction purposes. The classification system was first developed in 1929, but has been revised several times</p> <p>GROUP INDEX Group-index = (F - 35) 0.2 + 0.005 (LL-40)+0.01(F-15)(PI-10) F = % fine fraction (percentage of material &lt; 0.075 mm) LL = liquid limit PI = plasticity index For negative group index reported as nil Dinyatakan dalam angka bulat terendah using group index chart :Fine fraction LL PGI PI PGI</p> <p>summation</p> <p>For group index from A - 2 - 6 &amp; A - 2 - 7 use PI only.</p> <p>Example Group-index = (F - 35) 0.2 + 0.005 (LL-40)+0.01(F-15)(PI-10)F = % fine fraction (percentage of material &lt; 0.075 mm)</p> <p>LL = liquid limitPI = plasticity index</p> <p>a) Soil A - 6 , F = 55 % , LL 40 % , PI = 25 % Group index = (55 - 35) [0.2 + 0.005(40 - 40)] + 0.01 (55 - 15) (25 - 10) = 4.0 + 6.0 = 10 b) Soil A - 2 - 7, F = 30 %, LL = 50, PI = 30 Group index = 0.01 (30 - 15) (30 - 10 ) = 3</p> <p>Application of group index :1. For evaluation in groups clayey granular material &amp; silt-clay materiala) Group A - 1 - a, A - 1 - b, A - 2 - 4, A - 2 - 5 &amp; A - 3 satisfied for subgrade when good drainage and good compaction. b) A - 2 - 6 &amp; A - 2 - 7 (clayey granular) and silt clay (A - 4, A - 5, A - 6, &amp; A 7) require subbase layer or increasing base course thickness. c) Dianggap % F minimum kritis 35 %, dengan mengabaikan plastisitas 15 % affected by PI &gt; 10 d) LL 40 % critical e) PI 10 % critical</p> <p>f) non-plastic soils group index 0 2. No upper limit of group index, evaluation : F, LL &amp; PI3. With good drainage and good compaction supporting value for a subgrade material dianggap berbanding terbalik terhadap group index. group index = 0 good subgrade material group index = 2 bad</p> <p>Contoh soal5. Hasil uji lab : LL = 41% dan PL = 14%. Hasil analisis saringan:No. Saringan 4 % butiran lolos 100</p> <p>1040 200</p> <p>92,979,4 59,1</p> <p>Klasifikasikan tanah menurut: AASHTO Dari Tabel, karena butiran lolos saringan no. 200 = 59,1% &gt; 35%, maka tanah termasuk lanau atau lempung LL = 41% A-5 atau A-7. PI = 27% dan PL = 14% A-7-6 GI = 12,44 Jadi tanah termasuk klasifikasi A-7-6(12)</p>