Engineering Geology and Soil Mechanics
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Added on 2021-04-16
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Geological classification This system classifies soils based on their geological origin. The two main groups of soil based on its components are: organic soil and inorganic soil. Soil structure classification Soils can also be classified based on their structure, which is determined by the average grain size, conditions. Based on structure, soils can be classified as: single-grained, flocculent and honey-comb structures. This system classifies soils into 3 main classes: organic soils, coarse-grained soils, fine-grained soils and organic soils.
Engineering Geology and Soil Mechanics
Added on 2021-04-16
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Engineering Geology and Soil Mechanics 1ENGINEERING GEOLOGY AND SOIL MECHANICSNameCourseProfessorUniversityCity/stateDate
Engineering Geology and Soil Mechanics 2Table of Contents1.Task 1.................................................................................................................................................41.1.Task 1.1: Modes of formation, and classification and description of different rock types...41.1.1.Sedimentary rocks................................................................................................................41.1.2.Igneous rocks.......................................................................................................................41.1.3.Metamorphic rocks..............................................................................................................51.2.Task 1.2: Common rock forming minerals and susceptibility to weathering........................51.3.Task 1.3: Common usage of rock and un-cemented sediments for construction..................72.Task 2.................................................................................................................................................92.1.Task 2.1: Soil descriptions for in-situ and sampled.................................................................92.1.1.In-situ soil materials.............................................................................................................92.1.2.Sampled soil materials.......................................................................................................102.2.Task 2.2: Classification of soils...............................................................................................112.2.1.Geological classification....................................................................................................112.2.2.Soil structure classification................................................................................................112.2.3.Unified system...................................................................................................................122.2.4.Grain-size classification.....................................................................................................122.2.5.Soil-type classification.......................................................................................................122.3.Task 2.3: How to determine basic soil properties..................................................................122.3.1.Permeability.......................................................................................................................132.3.2.Shear strength....................................................................................................................142.3.3.Consistency limits..............................................................................................................152.3.4.Consolidation.....................................................................................................................162.3.5.Compaction........................................................................................................................162.3.6.Density index.....................................................................................................................162.3.7.Particle size........................................................................................................................162.3.8.Specific gravity..................................................................................................................172.4.Task 2.4: Calculations and graphs relating to basic soil properties.....................................172.4.1.Dry density and water content............................................................................................172.4.2.Particle size and shear strength..........................................................................................182.4.3.Void ratio and permeability...............................................................................................183.Task 3...............................................................................................................................................193.1.Task 3.1: Measures of geotechnical design parameters........................................................19
Engineering Geology and Soil Mechanics 33.1.1.Soil bearing capacity..........................................................................................................193.1.2.Shear strength....................................................................................................................213.1.3.Soil permeability................................................................................................................223.2.Task 3.2: Methods of ground investigation............................................................................223.2.1.Trial pitting........................................................................................................................233.2.2.Window sampling..............................................................................................................233.2.3.Cable percussion drilling...................................................................................................233.2.4.Rotary boring.....................................................................................................................243.3.Task 3.3: Laboratory measures on soils.................................................................................244.Task 4...............................................................................................................................................264.1.Task 4.1: Laboratory data for determining shear strength parameters using current codesof practice.............................................................................................................................................264.2.Task 4.2: Soil permeability and 1-D consolidation tests........................................................294.2.1.Soil permeability test.........................................................................................................294.2.2.One dimensional consolidation test....................................................................................30References................................................................................................................................................33
Engineering Geology and Soil Mechanics 41.Task 11.1.Task 1.1: Modes of formation, and classification and description of different rock typesRocks are usually classified based on their mode of formation, texture and chemical and mineral composition. Considering these parameters, the three main classes or types of rock formation are: metamorphic, sedimentary and igneous[ CITATION Sci11 \l 1033 ]. 1.1.1.Sedimentary rocksThese rocks form as a result of collection, deposition and accumulation of remains of living and non-living things, including soil particles, plant remains, animal remains, etc. (generally referred to as sediments)[ CITATION Del15 \l 1033 ], on land or sea/ocean floor. These sediments are usually eroded by various processes including erosion and weathering[ CITATION And17 \l 1033]. As more sediments get deposited, their self-weight compresses them together thus forming a solid rock known as sedimentary rock. The weight increases the intensity of pressure at the bottom of the sediments where he rock gets formed through a process known as lithification. These rocks form in layers and it can take several years for them to form a layered appearance. Sedimentary rocks include: sandstone, gypsum, limestone, conglomerate and shale. The main classification of sedimentary rocks are: clastic, organic and non-clastic. Clastic sedimentary rocks are formed from different sizes of pre-existing rock particles. They include shale, conglomerate, siltstone, sandstone and breccia. Organic sedimentary rocks are formed from organisms such as fossils. They include limestone, dolimites and coal[ CITATION Geo18 \l 1033 ]. Non-clastic sedimentary rocks are also known as chemical sedimentary rocks. These rocks get formed when a saturated mineral solution evaporates. They include rock salt and gypsum. Sedimentary rocks are relatively soft and can crumble or break easily. It is estimated that sedimentary rocks cover 75% of the earth’s surface whereas the remaining 25% is covered by metamorphic and igneous rocks[ CITATION Sirnd \l 1033 ]. 1.1.2.Igneous rocksFormation of igneous rocks is associated with volcanic processes or the occurrence of plate tectonics. These rocks form as a result of cooling and solidification/crystallization of melted rocks[ CITATION Liu13 \l 1033 ]. The melted rock can be found below the surface of earth (where it is called magma or silicate melts) or be released on the earth’s surface when a volcanic eruption
Engineering Geology and Soil Mechanics 5occurs (where it is called lava)[ CITATION duB17 \l 1033 ]. When these rocks form below the surface of the earth, they are called plutonic or intrusive igneous rocks, and when they form on the earth’s surface they are known as volcanic or extrusive igneous rocks[ CITATION WuX10 \l 1033 ]. Igneous rocks include: granite, basalt, pumice, scoria, peridotite, gabbro, dacite and obsidian[ CITATION Vil09 \l 1033 ]. Igneous rocks are generally compact, hard and crystalline in nature. However, some of them are cemented or welded and others remain weak when they do not undergo complete cooling process like others.1.1.3.Metamorphic rocksThese are rocks formed when sedimentary or igneous rocks are subjected to different temperature and pressure conditions thus changing their forms[ CITATION Liu16 \l 1033 ];[ CITATIONRat17 \l 1033 ]. These conditions are usually different from the original condition under which thesedimentary or igneous rocks were formed and that is why they are able to be transformed into new forms[ CITATION Sin17 \l 1033 ]. As these rocks are subjected to extreme temperatures or greater pressures, their chemical composition, mineral arrangement and structure changes[ CITATION Pan17 \l 1033 ]; [ CITATION Yan13 \l 1033 ]. Metamorphic rocks include: slate, gneiss, phyllite, migmatite, quartzite, schist and marble[ CITATION Ozb18 \l 1033 ]. Metamorphic rocks usually have shiny crystals and ribbon like layers[ CITATION Uda17 \l 1033 ].1.2.Task 1.2: Common rock forming minerals and susceptibility to weatheringRocks are formed from different minerals. By definition, minerals are naturally occurring non-living materials that have specific chemical composition and which are usually crystalline, solid and stable at room temperature. There are more than 5,000 mineral species. However, most of the rocks are formed from a mixture of a few minerals known as rock-forming minerals. These rock-forming minerals include the following:Quartz – this mineral is commonly known as silica. It is among the commonest minerals present in the crust of earth. It mainly comprises of silicon dioxide. The shape of quartz is usually prismatic and hexagonal. When quartz is pure, it is colorless but impurities can give it several colors including orange, pink and violet. Quartz is chemically and physically resistant to weathering. This means that the mineral remains stable and unaltered even when exposed to
Engineering Geology and Soil Mechanics 6different weathering conditions. The mineral does not have a cleavage and it is very hard, making it very resistant to mechanical weathering[ CITATION Yao17 \l 1033 ]. It is also resistant to chemical weathering because it is made up of interlocking silica tetrahedra. Quartz’s resistance to weathering makes it one of the most stable rock forming minerals. Mica – this is a group of silicate minerals containing iron, magnesium, potassium, water, silicon and aluminium. These minerals form book-like, flat crystals. They are usually found in intrusive igneous rocks, but can also be found in metamorphic and sedimentary rocks. There are 28 mica species but only 6 are known to be rock-forming minerals. These are: muscovite, paragonite, phlogopite, biotite, lepidolite and glauconite. These species are susceptible to different levels of weathering. During chemical weathering, the minerals’ color changes. In general, mica is relatively resistant to weathering. Olivine – this is a glassy, green, silicate mineral containing magnesium and iron. It is very common in ultramafic and mafic rocks. Olivine provides very minimal resistance to weathering hence it is highly susceptible to weathering. When exposed to a weathering environment, olivine loses its appeal very quickly thus becoming dull, yellowish brown and earthy[ CITATION ten12 \l 1033 ]. The mineral is also susceptible to hydrothermal metamorphism, which converts it from igneous to metamorphic rock[ CITATION San13 \l 1033 ]. Leaching changes olivine principally resulting to elimination of magnesium and addition of iron and water. Most of chemical reactionsof this mineral are complex and they include carbonation, oxidation and hydration.Pyroxene – this is a group of silicate mineral containing aluminium, calcium, magnesium, silicon, iron and oxygen. Pyroxenes re usually in form of columnar or short prismatic crystals. This mineral is usually found in metamorphic and igneous rocks. Pyroxene is relatively susceptible to weathering because it solidifies easily when exposed to high temperatures.Amphibole – this is a group of silicate minerals containing aluminium, calcium, magnesium, iron, water, oxygen and silicon. Amphiboles are usually in form of needle-like or prismatic crystals and are very common in metamorphic and igneous rocks. This mineral is not very susceptible to weathering nor is it very resistant to weathering. When exposed to certain conditions, amphibole can weather.
Engineering Geology and Soil Mechanics 7Feldspar – this is a group of silicate mineral that is the commonest mineral on earth. On Mohs scale, the hardness of feldspar is 6[ CITATION Ald17 \l 1033 ]. This means that the mineral is relatively resistance to weathering. Calcite – this is a clear or white carbonate mineral containing calcium carbonate. It is very common in sedimentary rocks. Calcite is susceptible to weathering, especially chemical weathering. When exposed to chemical weathering conditions, calcite will break down easily andits sediments carried away by groundwater solution and surface water.Garnet – this is a group of silicate mineral that is found in different colors – red, blue, colorless, orange yellow, black, purple, green, pink, brown, etc. On Mohs scale, the hardness of calcite ranges between 6.5 and 7.5 making it resistance to weathering. Some species of garnet include almandine, spessartine, grossular, andradite, pyrope and uvarovite. 1.3.Task 1.3: Common usage of rock and un-cemented sediments for construction Rocks and un-cemented sediments have been and are still widely used for construction purposes all over the world. These materials are used as construction materials because of the suitability of their mechanical, physical and chemical properties for the intended use[ CITATION Sau13 \l 1033 ]. Rocks can be used for construction of both temporary and permanent structures. Un-cemented sediments (also referred to as unlithified sediments) are materials that include loose aggregates and sand, collected from unconsolidated sediments of seas, lakes and rivers. The commonest use of rocks and un-cemented sediments is construction of temporary structures. These structures are mainly used for providing support, access or protection to the permanent structure being constructed. They can either be incorporated into the completed work or dismantled and removed once the permanent structure is completed or self-supporting[ CITATION Rat14 \l 1033 ]. Strength requirements of these structures are less than those of permanent structures. Rocks and un-cemented sediments can also be used to construct temporary structures for the purposes of decoration, exhibitions and modelling so as to assess theaesthetics, efficiency, function and appearance of the structure. One of the fundamental characteristics of un-cemented sediments is that they do not contain cement, which is a major binding material in construction.
Engineering Geology and Soil Mechanics 8The figure below is an illustration of a structure built from rock and un-cemented sediments. The structure, which is a wall, is made of large and smaller rocks. The rocks have been arranged by hand and without a binding material (cement). The structure appears to be less strong than a similar one built from rock and cemented sediments. Looking at the wall, it has larger rocks at the base so as to lower the center of gravity and make it stronger. Once the rocks have been placed appropriately, the small gaps remaining between the rocks can be filled with un-cementedsediments. This kind of a wall is known as dry rock wall. Below are other images that illustrate how rock and un-cemented sediments can be used for construction. The structures seem to have been constructed for different purposes including decoration, exhibitions, modelling and assessing the function. Generally, rock and un-cemented sediments have unprecedented usage in construction. Even though most of structures are built using rock and cemented sediments, the others also havenumerous uses. It is up to engineers and geologists to ensure that the rock and un-cemented sediments used are suitable for the intended purpose.
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