unit 1.pptx

Soil Types and Formation

• Soil is a loose layer of earth covering the planet's surface, formed from disintegrated rock, humus, inorganic, and organic materials.

• Soil formation takes around 500 years or more as rocks break into smaller parts due to various forces like wind, water, and salts' reaction.

• Soil is classified based on texture, proportions, and organic and mineral compositions.

Types of Soil

Sandy Soil

• Consists of small particles of weathered rock with low nutrients and poor water holding capacity.

• Good for drainage systems and formed from rocks like granite, limestone, and quartz.

Silt Soil

• Made up of smaller particles than sand, holds water better, and is fertile.

• Easily transported by moving currents and found near water bodies.

Clay Soil

• Smallest particles, tightly packed with low airspace, good water storage, but poor drainage.

• Sticky when wet and densest type of soil.

Loamy Soil

• Combination of sand, silt, and clay with properties of each type, suitable for farming.

• Retains moisture and nutrients, making it fertile for agricultural practices.

Soil Examination and Analysis

• Sample preparation involves drying soil samples at 105°C, removing any lumps formed due to moisture.

• Contaminants like bigger particles, inorganic and organic matter, and blood need to be removed.

• Techniques like turbidity test, pH measurements, and microscopic examination are used for soil analysis.

• Particle size distribution is crucial for predicting behaviors and ensuring product quality.

Turbidity in Water

• Turbidity is the cloudiness in water caused by particles and molecules scattering light.

• It can be affected by silt, sand, mud, bacteria, chemical precipitates, and impacts water treatment processes.

• High turbidity can block filters, damage valves, and reduce the efficiency of water treatment systems.

• Measuring turbidity is essential for maintaining water treatment systems and ensuring their effectiveness.

Measuring Turbidity

• Turbidity can be measured using an electronic turbidity meter or a turbidity tube.

• Units of measurement: nephelometric turbidity units (NTU) or Jackson turbidity units (JTLJ).

• Turbidimeters are accurate and useful for low turbidities but have high cost and power supply requirements.

• Nephelometric principle corrects for interferences and provides long-term calibration stability.

Soil pH Measurement

• Soil pH indicates soil acidity or alkalinity.

• pH range in soils: 3 to 9, with 7 being neutral.

• Equipment for measurement: colorimetric test kit or handheld pH meter.

• Method includes taking soil samples, using dye and barium sulfate, and comparing colors with a pH chart.

Forensic Soil Analysis

• Microscopic analysis used to characterize soil specimens in forensic laboratories.

• Stereo microscope used for initial examination to identify mineral and non-mineral components.

• Petrographic microscope used for transmitted polarized light examination.

• Important factors: particle size, distribution, structure, color, and non-mineral matter.

Physical Examinations of Soil Evidence

• Includes soil color, particle size distribution, density gradient, rock fragments, sand particles, clay minerals, organic matter, and biotic matter.

Soil Mechanics

• Sub-discipline of soil science and geotechnical engineering dealing with mechanical properties and processes of soils.

• Applications in predicting soil responses to stresses, soil structure formation, erosion resistance, and reinforcement by plant roots.

• Concepts and methods used in geotechnical engineering are applied to soil science.

Soil Composition

• Mineral matter classified based on bonding characteristics.

• Organic matter contributes to soil properties and contains humus, saccharides, fats, resins, waxes, nitrogen organics, and phosphorus-containing organics.

• Humus formation involves microbial degradation of plants and animals, with specific composition percentages.

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• Components of Soil

  • Saccharides: stabilize soil aggregates, examples include sugar, cellulose, starches, and gums

  • Fats, resins, and waxes: lipid extractable, degraded by lipase into glycerol and fatty acids

  • Nitrogen organics: nitrogen attached to humus, amino acids, and amino sugars

  • Phosphorus organics: source of plant phosphate, occurs as phosphate esters and phospholipids

• Soil Water

  • Provides medium for plants to obtain nutrients

  • Aids in maintaining soil texture, arrangement, and compactness

  • Holard: total water in soil, chesard: absorbable water, echard: unabsorbed water

• Soil Air

  • Composition similar to atmospheric air, essential for respiration of microorganisms and plants

  • Water clogging leads to anaerobic conditions, affecting gas diffusion and root permeability

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• Soil Structure

  • Influences water retention and behavior

  • Soil bulk density and texture affect water infiltration rate

  • Loam soil with humus is considered best for crops

• Formation of Soil Structure

  • Physio-chemical processes and biological processes contribute

  • Includes aggregate formation, flocculation, swelling, shrinking of clay masses

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• Soil Components

  • Root hair, adsorbed water layer, soil solid particle, air space

  • Soil saturated with water, drainage to groundwater

• Soil Texture

  • Contains air spaces, generally has a loose texture

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• Types of Soil

  • Structureless soil, sandy soil, clay soil, and their characteristics

  • Structural units called Peds with various shapes like granular, blocky, prism-like, and platy

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• Soil Structure Shapes

  • Block-like, granular, platy, prism-like

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• Compaction and Soil Additives

  • Soil compaction reduces pore spaces, impacting aeration and nutrient movement

  • Organic matter, calcium, magnesium, phosphorus, nitrogen, potassium, sulfur, and micronutrients can improve soil structure and fertility

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• Nutrient Application

  • Balanced fertilizers with P, N, K crucial for plant growth

  • Sulfur essential for protein synthesis and root development

  • Micronutrients support plant functions and root development

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• Soil Management Practices

  • Crop rotation, cover crops, tillage practices, and soil amendments can mitigate soil compaction

  • Gypsum and appropriate tillage practices can enhance soil structure

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• Ignition Test

  • Apparatus and method for conducting an ignition test on soil samples

  • Calculation of percentage weight loss on ignition

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• pH Measurement

  • Apparatus and method for measuring pH of soil samples

  • Standardizing pH-meter, dissolving soil sample, filtering, and measuring pH values

Soil Analysis using X-Ray Diffraction

• Soil forensic investigations may involve small soil samples (0.5 to 5 mg).

  • Routine pressed powders for XRD analyses may not be suitable for such small samples.

• XRD analysis methods for small soil samples:

  • Depositing samples onto Si wafer low background holders or loading into thin glass capillaries.

  • Mounting small specimens on glass fibers for analysis in Gandolfi or Debye–Scherrer powder camera.

• X-ray methods are crucial for differentiating materials in forensic examinations.

• Reproducible quantitative XRD is valuable for examining earth materials.

• XRD patterns can be likened to fingerprint comparisons between soil samples.

Murder of Father Heslin (1921) with Beach Sand Evidence

• Father Heslin was kidnapped and murdered in Colma, California in 1921.

• Chemistry professor Edward Heinrich linked the murderer to a baker and decorator of cakes.

• William Hightower, a master baker, was suspected and found guilty of the murder.

• Sand evidence from Hightower's knife and tent linked him to the crime scene.

Forensic Engineering Examination of Construction Materials

• Testing of construction materials can be physical, chemical, verifying quantity, and checking for damage.

• Testing is essential for quality control, compliance with specifications, certification, and legislative requirements.

• Materials from suppliers are tested to comply with standards and may have third-party accreditation.

• On-site testing methods for timber include oven dry testing and using a moisture meter.

• Testing of bricks includes compressive strength, water absorption, efflorescence, hardness, size, shape, color, soundness, and structure tests.

Timber Moisture Content Testing

• Moisture content of timber is crucial for its application.

• Moisture content is expressed as a percentage and can be measured using oven dry testing or moisture meters.

• Recommended moisture content levels vary based on the timber's application and environment.

• Oven dry testing involves drying timber in a ventilated oven to determine moisture content.

• Moisture meters for timber can be pin-type or pinless, measuring moisture content through different methods.

Brick Testing Methods

• Testing bricks includes compressive strength, water absorption, efflorescence, hardness, size, shape, color, soundness, and structure tests.

• Efflorescence test helps identify alkalis on brick surfaces.

• Various tests like hardness, size, shape, color, soundness, and structure tests ensure the quality of bricks.

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• Testing sand

  • Bulking test to determine sand volume increase

    • Damp sand depth measured (e.g. 150 mm)

    • Saturated sand depth measured (e.g. 124 mm)

    • Bulking calculation: (150 - 124) / 124 x 100 = 21%

  • Silt test to check cleanliness

    • Salt water solution poured over sand sample

    • Silt layer height should not exceed 6 ml or 6% of sand height

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• Testing concrete

  • Slump test for consistency

    • Steel slump cone filled and tamped, slump measured

    • Usual slump specification: 50-75 mm

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• Test cubes

  • Made and crushed to check concrete strength

    • Standard 150 x 150 x 150 mm steel test cube mold used

    • Cubes tested at 7 and 28 days for compressive strength

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• Various concrete tests

  • Rebound hammer test for surface hardness

  • Penetration test (Windsor probe test) for compressive strength

  • Pull out test to quantify concrete strength

  • Vibration test to measure vibrations and correlate compressive strength

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• Key terms

  • Scale pointer, plunger, exposed probe length, damage zone

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• Introduction to structure failure

  • Building failure categorized into physical and performance failures

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• General causes of failure

  • Problems leading to structure failure

    • Weakness due to size, shape, or material choice

    • Instability from design flaws or material issues

    • Manufacturing errors causing structural weaknesses

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• Types of cracks in structures

  • Horizontal cracks at junctions and bases of structures

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• Man-made vs natural causes of failure

  • Structural failures due to human errors or material irregularities

  • Natural factors like rainfall contributing to building collapses

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• City-specific reasons for building collapses in Mumbai

  • High property prices leading to living in old properties

  • Building collapses due to lack of maintenance and substandard materials

  • Shoddy construction and violations of building codes due to corruption and demand

Case Study: Canacona Building Collapse

Main Ideas:

• Date: January 8, 2014

• Incident: Collapse of an under-construction five-storey building

• Casualties: 18 workers killed, 14 injured

• Causes:

  • Poor workmanship

  • Lack of soil analysis

  • Substandard quality of construction materials

• Observation:

  • Debris showed beams and slabs on top of each other with no columns

  • Columns reduced to powder at the site

• Concrete Grade:

  • M20 grade used for columns, deemed inadequate

  • Recommendation for M25 grade for columns

Supporting Details:

• Location: Ruby residency in Chaudi, Canacona

• Speculation: Weak columns and strong beams as a possible cause

• Source