PHILADELPHIA UNIVERSITY

Transcription

1 PHILADELPHIA UNIVERSITY FACULTY OF ENGINEERING AND TECHNOLOGY DEPARTMENT OF CIVIL ENGINEERING. Engineering Geology Part one 1 2nd semester 2018/2019 Eng. Amany Assouli 1

2 INTRODUCTION: What is the engineering geology? engineering geology is application of geological data, technique and principle to the study of :minerals, rocks, soil surface materials and ground water. And this is essential for the proper location, planning, design and construction of engineering structure. Engineering geology provides a systematic knowledge of construction materials, durability and other properties

3 CONT What is the engineering geology study? Minerals Rocks Soli surface Ground water 3

4 Minerals: Building Blocks of Rocks Minerals: Building Blocks of Rocks 4

5 MINERALS: BUILDING BLOCKS OF ROCKS Geologically, a mineral can be defined as a naturally occurring inorganic solid that has an orderly crystalline structure and a definite chemical composition. 5

6 MOST COMMON MINERALS 1. Quartz (sio2) 2. feldspar group 3. mica group 4. pyroxene group 5. amphibole 6. clay group 7. calcite ( caco3) 8. dolomite (mgco3) 9. limonite (fe2o3 ) 10. pyrite ( fes2) 6

7 01_03 7

8 By definition a mineral is/has 1. Naturally occurring 2. Solid (at temperatures normally of the Earth s surface) ICE is a mineral. 3. Ordered crystalline structure (repetitive and ordered crystal structure, e.g.: cubic) 4. Definite chemical composition (SiO2: Quartz, CaCO3: Calcite) 5. Generally inorganic (sugar is not a mineral 8

9 NOT MINERALS A synthetic diamond is not true mineral Organics-C bonded to H (mostly from plants and animals). Calcite (CaCO3) can originate from organisms 9

10 PHYSICAL PROPERTIES Crystal form ( Habit) OF MINERALS External expression of a mineral s internal structure Crystals grow if time and space are enough. Often crystal growth is interrupted due to competition for space and rapid loss of heat 10

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12 Quartz 12

13 A GARNET CRYSTAL 13

14 CUBIC CRYSTALS OF PYRITE Figure 1.7 A 14

15 Crystal form is not clear 15

16 PHYSICAL PROPERTIES OF MINERALS Luster Appearance of a mineral in reflected light regardless of their color Two basic categories Metallic-appearance of a metal Nonmetallic includes descriptive terms include glassy, silky, pearly, earthy submetallic-appear slightly metallic 16

17 GALENA (PBS) DISPLAYS METALLIC LUSTER Figure

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19 PHYSICAL PROPERTIES OF MINERALS Color Minerals tend to occur in a range of colours, and colour patterns which help to identify them Most minerals are coloured by a limited number of metals present as impurities. The most common elements affecting colour are: chromium, iron, manganese, titanium and copper. It is chromium which produces the intense red of ruby and the brilliant green of emerald. 19

20 QUARTZ (SIO 2 ) EXHIBITS A VARIETY OF COLORS 20

21 PHYSICAL PROPERTIES OF MINERALS STREAK WHEN MINERALS ARE SCRATCHED, THE POWDER THAT IS MADE BY THE SCRATCH IS CALLED THE STREAK. SOMETIMES THE COLOUR OF THE STREAK CAN BE USED TO IDENTIFY THE MINERAL. EG. HAEMETITE A BLACK MINERAL HAS A RED STREAK. NO OTHER BLACK MINERAL HAS A RED STREAK. 21

22 PHYSICAL PROPERTIES OF MINERALS dark streak-metallic light streak- nonmetallic Streak obtained by rubbing a mineral sample against an Unglazed Porcelain Plate 22

23 STREAK IS OBTAINED ON AN UNGLAZED PORCELAIN PLATE Figure

24 PHYSICAL PROPERTIES OF MINERALS Hardness Resistance of a mineral to abrasion or scratching Is determined by comparing minerals to a standard scale called the Mohs scale of hardness However, other handy object can be used to determine Hardness: glass, finger nail, streak plate, etc 24

25 Mohs Scale of Hardness Figure 1.9 Not linear scale, but of relative ranking 25

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27 PHYSICAL PROPERTIES OF MINERALS Cleavage Tendency to break along planes of weak bonding Perfect cleavage or imperfect cleavage Produces flat, shiny surfaces Described by resulting geometric shapes: 1. Number of planes (1, 2, or 3 sets of cleavage) 2. Angles between adjacent planes Calcite has 3 set, while quartz has no cleavage 27

28 01_17C 28

29 FLUORITE, HALITE, AND CALCITE ALL EXHIBIT PERFECT CLEAVAGE 29 Figure 1.11

30 PHYSICAL PROPERTIES OF MINERALS It was Archimedes who first worked out the principal of specific gravity or relative density. Specific gravity is defined as the ratio of the weight of a substance compared to that of an equal volume of water. For example, a piece of galena (lead ore), with a specific gravity of 7.4 will feel much heavier than a piece of quartz of a similar size but with specific gravity of 2.65, reflecting the way the atoms are packed together. 30

31 Fracture PHYSICAL PROPERTIES OF MINERALS Absence of cleavage when a mineral is broken Specific Gravity Weight of a mineral/weight of an equal volume of water Average value =

32 CONCHOIDAL FRACTURE 32 Figure 1.12

33 PHYSICAL PROPERTIES OF MINERALS Other properties Magnetism Calcite Reaction to hydrochloric acid Gold Malleability Calcite Double refraction Halite Taste Sulfur Smell Elasticity Mica 33 Magnetite

34 MINERAL GROUPS Nearly 4000 minerals have been named Rock-forming minerals Common minerals that make up most of the rocks of Earth s crust Only a few dozen members are common Composed mainly of the 8 elements that make up over 98% of the continental crust 34

35 ELEMENTAL ABUNDANCES IN CONTINENTAL CRUST Al-Qudah 2006 Almost 75% of crustal composition Figure

36 MINERAL GROUPS Silicates-(dark and light) Most important mineral group 1. Comprise most rock-forming minerals 2. Very abundant due to large % of silicon and oxygen in Earth s crust Silicon-oxygen tetrahedron Fundamental building block Four oxygen ions surrounding a much smaller silicon ion 36

37 Si O Tetrahedron Fe, Mg, K, Na and Ca bond the silicate structure to produce an electrically neutral compound. Figure

38 Figure 1_16 COMMON SILICATE MINERALS: 38

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40 01_16 Al-Qudah

41 COMMON SILICATE MINERALS ARE: Feldspar group Most common mineral group (50% of Earth s crust) Quartz The only common silicate composed entirely of oxygen and silicon (SiO2) 41

42 POTASSIUM FELDSPAR Figure

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44 ORIGIN OF SILICATE MINERALS: 1. Crystallization from molten rocks (Magma) while cooling. 2. Weathering of other Silicate minerals at Earth s surface (e.g. Clay Minerals) Which mineral to form is controlled by: Environmental conditions during crystallization (T&P, close to Earth s surface or deep). Chemical composition of Magma. Example: Olivine forms deeper than Quartz 1200ºC 700ºC. 44

45 MINERAL GROUPS IMPORTANT NONSILICATE MINERALS Forms only 8% of Earth s crust Often occur as constituents in sedimentary rocks due to their origin. Economically important including: (Oxides, Sulfides, Sulfates, Halides, Carbonates & Native Elements) 45

46 Origin At earth s surface Al-Qudah 2006 Mag. Forms from magma at high T&P Thermal Solutions Earth s surface aqueous solutions Next to magmatic activity Diamond from magma at high T&P. Graphite low T metamorphism. Table 1.1 Earth s surface aqueous solutions 46 Earth s surface aqueous solutions

47 MINERAL GROUPS Important nonsilicate minerals Carbonates Primary constituents of limestone and marble Limestone is used commercially for road paving, building stone, and as the main ingredient in Portland cement 47

48 MINERAL GROUPS Important nonsilicate minerals Halite and gypsum Both are commonly found in thick layers Like limestone, both halite and gypsum are important nonmetallic resources 48

49 MINERAL GROUPS Important nonsilicate minerals A number of other minerals have economic value Examples Hematite (oxide mined for iron ore) Sphalerite (sulfide mined for zinc ore) Galena (lead) Native Elements: Gold, Silver, copper and Carbon (Diamond & Graphite) 49

50 NATIVE COPPER 50

51 MINERAL RESOURCES Are the storehouse of useful minerals that can be recovered. It includes: Reserves (known deposits that can be profitably extracted at the current time) Known deposits that are not yet recoverable due to economic conditions or technology. Inferred deposits, but not yet discovered. 51

52 Ore: profitable metallic mineral, but may include non-metallic minerals, like fluorite and sulfer. Industrial rock minerals: are not ores, like these used as building stones, ceramics and fertilizers. 52

53 ECONOMIC VALUE Element must be concentrated above the level of its average crustal abundance. Example Al needs 4 times the concentration of its average crustal abundance (4x8.1%). Economic changes. 53

54 Talc Gypsum Bauxite Copper Sulfur Muscovite (Mica) Halite Calcite Limonite /Taconite Feldspar Quartz (massive type) Quartz crystal Diamond Baby powder, soapstone, gymnastics to grasp bars Wall board, Plaster of paris Aluminum foil, Airplane parts/ aluminum Tubing, electrical wires, sculptures Fungicides, kills bacteria, vulcanizes rubber, in coal and fuels White, gray material in electrical insulators Salt Hard water deposit/part of limestone rock of ancient sea beds/forming along shores of the Great Salt Lake Source of Iron / around Cedar City Ceramics and porcelain, colors in granites (not black) Glass manufacturing/radios/computers /electronic equipment Cutting tools/ blades/ saws 54