Soil Mechanics & Foundation Engineering

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Cornelius Austin
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Foundation Engineering 28-B/7, Jia Sarai, Near IIT,

1 SAMPLE STUDY MATERIAL Potal Correpondence Coure GATE, IES & PSU Civil Engineering Soil Mechanic & Foundation Engineering 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

C O N T E N T SOIL MECHANICS 1. SOIL FORMATION AND SOIL TYPES 3-4 2. PROPERTIES OF SOIL 5-28 3. CLASSIFICATION OF SOIL 29-33 4. SOIL STRUCTURE AND CLAY MINERAL. 34-38 5. SOIL COMPACTION 39-46 6.

2 C O N T E N T SOIL MECHANICS 1. SOIL FORMATION AND SOIL TYPES PROPERTIES OF SOIL CLASSIFICATION OF SOIL SOIL STRUCTURE AND CLAY MINERAL SOIL COMPACTION PRINCIPLE OF EFFECTIE STRESS, CAPILLARITY AND PERMEABILITY SEEPAGE THROUGH SOIL STRESS DISTRIBUTION COMPRESSIBILITY AND CONSOLIDATION SHEAR STRENGTH OF SOIL STABILITY OF SLOPES EARTH PRESSURES AND RETAINING WALLS FOUNDATION ENGINEERING 13. SHALLOW FOUNDATION PILE FOUNDATION SOIL EXPLORATION IES, GATE PAPERS & PRACTICS SET 16. OBJECTIE PRACTICS SET-I OBJECTIE PRACTICS SET-II SOIL MECHANICS & FOUNDATION [IES] PRACTICS SET-III SOIL MECHANICS GATE PAPERS ( ) FOUNDATION ENGINERING GATE PAPERS ( ) B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

3 CHAPTER-1 SOIL FORMATION AND SOIL TYPES The term oil' ha different definition belonging to different dicipline. For a civil engineer, oil mean all naturally occurring relatively unconolidated earth material-organic or inorganic in character that lie above the bedrock. Soil mechanic i the branch of civil Engineering hich deal ith the application of principle of mechanic to engineering problem related to oil. Soil Engineering encompae not only oil mechanic but alo geology, tructural engineering, oil dynamic and many other dicipline hich are often required to obtain practical olution to problem of oil. Soil Formation and Soil Type: Soil can be divided into to main group on the bai of their origin. (a) Formed by phyical eathering by mean of ater, ice and ind. e.g. Gravel, and (b) Formed by chemical eathering by oxidation & hydration. e.g. Clay, ilt Soil of organic origin are extremely compreible. If a product of rock eathering remain available at the place of their origin it i called reidual oil. If oil i tranported from it place of origin by ind, ater, ice etc. and get depoited at other place it i called a tranported oil. According to the tranporting agency and method of depoition tranporting oil can be claified a: Soil Formed by Method of Tranportation and Depoition: 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

4 Loe: Looe depoit of ind blon ilt hich i eakly cemented ith calcium carbonate and montmorillonite. It i formed in arid and emi-arid region. Tuff: A mall-grained volcanic ah tranported by ind or ater. Bentonite: A chemically eathered volcanic ah. Glacial till: A mixture of boulder, gravel, and, ilt and clay, depoited by glacial and not tranported or egregated by ater. Marl: A very fine grained calcium carbonated oil of marine origin. Colluvial oil: Accumulation of rock debri or talu at the bae of a teep cliff due to action of gravity. Peat: A highly organic oil, Bron to black in color, fibrou and highly compreible. Muck: A mixture of fine particle of inorganic oil and black decompoed organic matter. Generally found accumulated in condition of imperfect drainage like amp. (Peat and Muck are alo called a cumuloe oil) Humu: A dark bron, organic oil coniting of partly decompoed vegetative matter. Regional oil depoit of India: 1. Marine depoit: Marine clay are oft and may contain organic matter. It poe lo hear trength and high compreibility. Not uitable a a foundation material. 2. Laterite and Lateritic oil: Formed by the decompoition of rock, removal of the bae and ilica and formation of oxide of iron and aluminium at the top of the oil profile. There are to type of laterite: - Primary and Secondary. Laterite are reddih in color and hard in dry tate. 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

5 If the grain ize increae upon alternate etting and drying cycle, the oil i called laterite but lateritic oil doe not ho thi characteritic. Laterite are ued a foundation material and retain their lope ell. 3. Black cotton oil: Thi i the Indian name given to the expanive oil. It i not neceary that Black cotton oil hould be Black in colour alay. Thee are formed from baalt or trap and contain the clay mineral montmorrillonite, hich i reponible for exceive elling and hrinkage characteritic of the oil. Under-reamed pile are conidered mot uitable a foundation for thee oil. Note: Compreibility mean compreion ( H) per unit increae in effective H tre ( ) i. e. ' 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

6 CHAPTER-2 PROPERTIES OF SOIL Phae Diagram: In general, oil ma i a three-phae ytem compoed of olid, liquid and gaeou matter. The diagrammatic repreentation of the different phae in oil ma i called the phae diagram. Phae diagram (Partially aturated) Phae diagram: 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

7 Some Definition: 1. Water content (): Defined a the ratio of eight of ater ( ) to the eight of olid ( ) in a given ma of oil. W 100 % W W = eight of ater W = eight of olid There can be no upper limit to ater content i.e oid Ratio (e): Defined a the ratio of volume of void (v v ) to the volume of olid (v ). e v v = volume of void = volume of olid. Soil ha to contain ome void but there cannot be an upper limit to the void volume i.e. e > 0 3. Poroity (n): Defined a the ratio of the volume of void to total volume of the oil (v). v n 100 % v = volume of void = total volume of oil. The poroity of a oil cannot exceed 100% i.e. 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

8 0 n 100 In oil engineering, void ratio i frequently ued. 4. Degree of aturation (S): Defined a the ratio of volume of ater to volume of void. % 100 v v volume of ater volume of void The degree of aturation varie beteen 0 and 100 i.e Air content (a c ): Defined a the ratio of volume of air (v a ) to volume of void (v v ). a ac 1 S, 0 a c 100 v 6. Percentage air void (n a ): It i defined a volume of air void (v a ) to the total volume (v) of oil ma. a na 100 %, 0 n 100 n a na c 7. Unit eight: (a) Bulk unit eight ( t ) or Total unit eight: Defined a the total eight of a oil ma () per unit of total volume (v) t or t v v v v W = eight of oil ma a 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

9 = total volume of oil ma It S.I unit i KN / m 3 (b) Dry unit eight ( d ): Defined a the eight of olid ( ) per unit of total volume (v). d v (c) Saturated unit eight ( at ): Defined a the total eight of a fully aturated oil ample ( at ) per unit of total volume (v) at at (d) Submerged unit eight ( ' ): ' at here, = unit eight of ater. The reduction in unit eight occur due to action of buoyant force on the oil olid. The ubmerged unit eight i roughly one half of the aturated unit eight i.e. 1 ' 2 at 8. Specific gravity (G or G): Specific gravity of olid may be defined a the ratio of unit eight of olid ( ) to that of ater ( ). G At 4C, = 1 g/cc. or 9.81 kn/m Apparent or Ma pecific gravity (G m ): It i defined a the ratio of the bulk unit eight of the oil ( t ) to the unit eight of ater ( ). G m t alue of G : Soil Type Specific Gravity 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

10 Clean and and gravel Silt and Silty and Inorganic clay Soil having higher percentage of mica, iron The value of pecific gravity for mot of the oil lie beteen Coare-grained oil exhibit loer value. The preence of organic matter lead to very lo value. The pecific gravity of organic oil i beteen. Soil ith high quantity of iron or mica exhibit higher value. Some important relationhip: All notation have their tandard meaning (a already explained) 1. Relation beteen, and W: W W 1 W Weight of olid W Total eight of oil ater content Weight of olid i the ratio of total eight of oil to the (1+ ater content). 2. Relation beteen e and n : e n n & e 1 e 1 n n = poroity e = void ratio 3. Relation beteen e, W, G and S: 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

11 es G GATE, IES & PSU ( ) e = void ratio. = Weight of ater. S = Degree of aturation. G = Specific Gravity 4. Relation beteen t, G, e, and S G Se t 1 e (1) t bulk unit eight of oil. unit eight of ater. 5. Relation beteen at, G, e, and : G e at 1 e at Saturated unit eight unit eight of ater. ( S 1) Obtained by putting value of S = 1 in above relationhip (4). 6. Relation beteen d, G, e and : (Dry oil) d G 1 e If S = 0 Obtained by putting value of S = 0 in relationhip (5). 7. Relation beteen, G, e and : (Submerged oil) ()D e g 18 2 () d 8. Relation beteen t, d and : d t 1 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

12 9. Relation beteen d, G,, and n a : G Thi expree the relationhip beteen dry unit eight and the percentage air void. Thi i ueful in the tudy of compaction behavior in oil. When n a = 0, i.e. hen the oil become fully aturated at a given ater content, d i given by: G d 1 G METHODS OF WATER CONTENT DETERMINATION: 1. Oven-drying method: Commonly adopted and the implet method ued in laboratory. Sample are dried for 24 hour in the oven at temperature C. 2 3 Water content, 100 % 3 1 W 1 = eight of container W 2 = eight of container ith moit ample. W 3 = eight of container ith dried ample. Weight of ater, W = 2 3 Weight of olid W = Pycnometer method Quick laboratory method. 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

13 Suitable for coheionle oil. GATE, IES & PSU ( ) Pycnometer: Gla bottle ith conical top-900ml. capacity; W 1 = eight of empty pycnometer. W 2 = eight of pycnometer + oil W 3 = eight of pycnometer + oil + ater W 4 = eight of pycnometer + ater W = eight of oil olid. Water content, W W i Weight of ater, W W W W... ii 2 1 Weight of olid (W ) can be found by removing olid from W 3 and replacing it by eight of an equivalent volume of ater, hence the eight W 4 ill be: W W W3 W W4 and G G G iii G 1 Putting value of (ii) and (iii) in equation (i), ater content ill be W W G 1 W3 W4 G 2 1 W % Note: In thi method G hould be already knon. 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

14 3. Sand Bath method: GATE, IES & PSU ( ) Quick and field method. Wet oil ample i placed in container and dried by placing it on a and bath. Water content i determined by uing equation a ued in oven-drying method. Uniform heat i provided to oil ma in thi method. 4. Rapid moiture Meter method: Portable equipment. Calcium carbide (CaC 2 ) i ued a reagent. It react ith moiture of oil ample and produce acetylene ga (C 2 H 2 ) CaC 2H O C H Ca OH Intrument i calibrated to meaure the preure due to C 2 H 2 a the percentage of moiture in the ample. May not give actual value. 5. Torion Balance moiture meter method: Thi method i good for oil hich quickly reaborb moiture from atmophere. In thi method eighing and drying i done imultaneouly. Laboratory method. Infrared radiation i ued for drying the ample. DETERMINATION OF SPECIFIC GRAITY OF SOIL SOLIDS: Determined by uing pycnometer. 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

15 W 1 = eight of empty pycnometer. W 2 = eight of pycnometer + oil (oven dried) W 3 = eight of pycnometer + oil olid + ater W 4 = eight of pycnometer + ater Weight of dry oil W = (W 2 W 1 ) Weight of ater having the ame volume a that of olid, W. = (W 4 W 1 ) (W 3 W 2 ) = (W 2 W 1 ) (W 3 W 4 ) Specific gravity, G Specific gravity value are reported at 27C (In India) If Tc i the tet temperature, then Specific gravity at 27C i given by: G A e kno that doe not very ith change in temperature, o can be aumed cont for all the temperature. There fore G cont. G or TºC TºC cont. G or 27ºC 27ºC cont. 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

16 Hence G TºC GATE, IES & PSU ( ) G 27ºC 27ºC TºC DETERMINATION OF IN SITU WEIGHT: 1. Core cutter Method: It cannot be ued in cae of hard and gravelly oil. A core-cutter (ith 25 mm high dolly at top) of knon volume (1000 cc) i driven into oil uing a hammer. The cutter filled ith oil i eighed and volume of cutter i calculated from the dimenion of cutter and thu In itu unit eight i determined by dividing oil eight by volume of cutter. Dry unit eight, d t 1 W W 2. Sand replacement method: Ued in hard and gravelly oil. A hole i made into the ground and the excavated oil i eighed. The volume of hole i determined by replacing ith and (aeno and). Thu, In itu unit eight i calculated by dividing eight of excavated oil to the volume of the hole. 3. Water diplacement method: Suitable for coheive oil only. Suitable for oil from hich lump can be taken out. Sample i brought to a regular hape (eight W 1 ) and coated ith a thin layer of paraffin ax and again eighed (let W 2 ). No, the coated ample i placed into a metal container filled ith ater up to the brim. The diplaced ater ( ) i meaured. Hence the volume of uncoated oil pecimen i given by 28-B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

17 W2 W1 pa pa = unit eight of paraffin ax. W1 Hence, bulk unit eight of oil, t Dry unit eight of oil, 1 t d n To Buy Potal Correpondenece Package call at B/7, Jia Sarai, Near IIT, Hauz Kha, Ne Delhi Ph engineerintitute.com

BASICS OF SOIL MECHANICS

BASICS OF SOIL MECHANICS Lecture Outline Topic for dicuion 1. Origin of Soil 2. Three Phae Diagram 3. Important Term 4. Phae Relationhip 5. Atterberg limit Origin of Soil Soil are formed by eathering of