GEOTECHNICAL ENGINEERING – I B.E. IVTH SEMESTER Prof. R. G. Bade

UNIT 1 1. Introduction: Formation of soil, residual & transported soil, major deposits found in India, soils generally used in practice such as sand, gravel, organic soil, clay, Betonies, black cotton soil etc. Introduction to clay mineralogy. 2. Phases of soil: Various soil weight & volume inter-relationship. Density index, methods of determining in situ density.

What is Geotechnical Engineering? Soil: Natural aggregates of mineral grains, loose or moderately cohesive inorganic or organic in nature that have the capacity of being separated by means of simple mechanical processes. Geotechnical Engineering: A unique combination of science, experience, judgment and a passion for understanding the uniqueness and variability of ground conditions resulting from the forces of nature. It is the art of determining the properties of unseen and variable materials to provide a facility that perform as expected at acceptable level of risk and at an optional cost.

Application of civil engineering to earthen materials What is Geotechnical Engineering? Application of civil engineering to earthen materials Soil Rock Groundwater

What is the difference between soil and dirt? If you can grow food in it, get paid to analyze it, or get college credit for playing with it, it’s soil; otherwise it’s dirt.

Branches of Geotechnical Engineering Soil Mechanics Rock Mechanics Foundation Engineering Geoenvironmental Engineering Geotechnical Earthquake Engineering Geologic Engineering

Soil Behavior Introduction “Concrete and Steel are textbook materials; Soil is not.”

Soil is heterogeneous Homogeneous Heterogeneous

Soil is anisotropic Anisotropic Isotropic

Soil is non conservative Before After Conservative Before After Nonconservative (but that doesn’t mean it’s liberal)

Soil is nonlinear Stress Strain Linear Stress Strain Nonlinear

SOIL FORMATION Weathering is the process of the breaking down rocks. There are two different types of weathering. Physical weathering and chemical weathering. In physical weathering it breaks down the rocks, but what it's made of stays the same. In chemical weathering it still breaks down the rocks, but it may change what it's made of. For instance, a hard material may change to a soft material after chemical weathering. STAGE 1 STAGE 2 STAGE 3 STAGE 4

SOIL PROFILE

SOIL TYPES SOIL TYPES RESIDUAL SOIL SEDIMENT SOIL ALLUVIUM SOIL LACUSTRINE SOIL MARINE SOIL PARTICULAR SOIL EXPANSIVE SOIL ORGANIC SOIL COLLAPSIBLE SOIL QUICK CLAY

BASIC CHARACTERISTIC PARTICLE BONDING THE PARTICLE BONDING IS VERY WEAK SO RELATIVELY EASY TO GOING TO CHANGE AND HAVE NON-LINEAR BEHAVIOUR AND CHARACTERISTIC SHAPE, SIZE AND STRUCTURE OF SOIL PARTICLE Cohesive Soil Non-cohesive Soil

PHYSICAL PROPERTIES OF SOIL BASIC DEFINITION AND PHASE RELATIONS Solid Water Air Soil is generally a three phase material Contains solid particles and voids Voids can contain liquid and gas phases Phase Volume Mass Weight Air Va Water Vw Mw Ww Solid Vs Ms Ws

Units Length metres Mass tonnes (1 tonne = 103 kg) Density t/m3 Weight kilonewtons (kN) Stress kilopascals (kPa) 1 kPa = 1 kN/m2 Unit weight kN/m3 Accuracy Density of water, rw = 1 t/m3 Stress / Strength to 0.1 kPa

Weight and Unit weight Force due to mass (weight) more important than mass W = M g Unit weight

Specific Gravity This is defined by Gs is useful because it enables the volume of solid particles to be calculated from mass or weight

Voids Ratio It is not the actual volumes that are important but rather the ratios between the volumes of the different phases. This is described by the voids ratio, e, or porosity, n, and the degree of saturation, S. The voids ratio is defined as and the porosity as The relation between these quantities can be simply determined as follows Hence

Degree of Saturation The degree of saturation, S, has an important influence on soil behavior. It is defined as The phase volumes may now be expressed in terms of e, S and Vs Vw = e S Vs Va = Vv – Vw = e Vs (1 – S)