Principles of Soil Mechanics 2023 with complete solution

A clay soil has a liquid limit of 60%, a plastic Limit of 20% and a natural, in situ water content of 25%, The clay in the natural, in situ state would likely: a) be normally consolidated b) have a high compressibility c) have a stiff consistency d) have a soft consistency have a stiff consistency An Aeolian soil is a soil which is formed by: a) deposition of soil particles along or a base of a slope by gravity b) transportation and deposition of soil particles by wind c) erosion and weathering of parent materials in place d) deposition by flowing water in a stream or river transportation and deposition of soil particles by wind Clay minerals are formed by the movement and crushing action of glacier ice. True or False False Clay soils have plastic properties because they contain a high percentage of fines (particles smaller than the #200 sieve (0.075mm)) True or False False Clay minerals are formed by chemical weathering of rock minerals True or False True In a dispersed structure clay mineral particles form parallel, face- to- face orientation. True or False True The relationship between zero air voids dry unit weight and moisture content depends on the compactive effort applied to the soil. True or False False For a given soil, the modified Proctor compaction curve will have a higher optimum moisture content and a higher maximum dry unit weight than the standard Proctor compaction curve. True or False False For clays, as specific surface area decreases, the liquid limit increase. True or False False One process that holds water molecules to a clay mineral particle surface is the attraction of dipolar water to the negatively charged clay mineral particle surface True or False True For a clay soil compacted with a given compactive effort, the maximum dry density tends to decrease as plasticity index of the clay soil decreases. True or False False A soil has water content of 20% degree of saturation of 90% and specific gravity of soil solids of 2.70. the porosity of this soil is 37.5% True or False True Compacting a cohesive, clayey soil on the wet side of optimum moisture content contrasted with the dry side of optimum moisture content will give the soil: (choose 2) a) higher shear strength b) higher potential for drying shrinkage c) higher stiffness (i.e. higher slope of the stress- strain curve) d) a lower hydraulic conductivity because the clay clods/aggregates can be remolded. - higher potential for drying shrinkage - a lower hydraulic conductivity because the clay clods/aggregates can be remolded. A moist soil sample weighing 0.02kN has a moisture content of 33.0%. If 0.002kN of water are added to the sample, the moisture content of the sample will be: a) 46.4% b) 43.0% c) 33.1% d) Need a value of G(s) of the soil to solve this problem. 46.4% Soil with a G(s) of 2.71 and a water content 16% is compacted to produce a cylindrical sample of volume 8.619e-5 m^3. After compaction 6% of the total volume of the sample is air. The weight of the soil solids in kN that is required to form this sample is: a) 26.59 kN b) 1.50e-3 kN c) 2.16e-3 kN d) 1.75e-3 kN 1.50e-3 kN Determine the total volume of borrow material in m^3 with a void ratio of 1.25 that is required to construct a embankment of total volume 200,000 m^3 at a void ratio of 0.80. a) 312,500 m^3 b) 250,000 m^3 c) 160,000 m^3 d) 128,000 m^3 250,000 m^3 Seepage velocity is: a) lower than discharge velocity b) determined by dividing the discharge velocity (numerator) by the void ratio of the soil (denominator) c) the product of the hydraulic conductivity times the hydraulic gradient d) determined by dividing the discharge velocity (numerator) by the porosity of the soil (denominator) determined by dividing the discharge velocity (numerator) by the porosity of the soil (denominator) Compaction rollers equipped with Intelligent Compaction systems can assess and quality control a higher percentage of compacted earthworks compared to using a nuclear density gauge. True and False True Hydraulic conductivity does not depend on the viscosity and unit weight of the permeating fluid. True and False False For the equation k= 2.303 (aL/At)log(h(1)/h(2)) used to analyze a falling head permeability test 't' corresponds to elapsed time between total head differences 'h(1)' and 'h(2)' is the cross- sectional area of the standpipe. True and False False For downward, steady state seepage through a saturated soil sample under a hydraulic gradient of 1.0 the pressure head is constant through the soil sample. True and False True For anisotropic hydraulic conductivity conditions, the flow net is drawn in transformed section with the horizontal scale compressed relative to the vertical scale because the horizontal hydraulic conductivity is typically greater than the vertical hydraulic conductivity. True and False True Why are soil mechanics and geotechnical engineering an important discipline of civil engineering? Because every other civil engineering discipline, in some important way, depends on a knowledge and application of soil mechanics and geotechnical engineering. Weight- Volume Relationships: Soils can be a 2 phase, 3 phase, 4 phase medium: 2 phase: dry soil or saturated soil 3 phase: unsaturated soils- soil solids, water and air 4 phase: soil solids, liquid water, air ice (frozen soil) or soil solids, water, air, and contaminant (e.g. gasoline), soil: tire shred mixture What is the water content percentage of dry soil? 0% What is the water content percentage of saturated soil? 100% To improve the engineering properties of soil through compaction: - Reduce settlements - Increases strength and bearing capacity - Reduce permeability (e.g. dams, levees, landfill liners) Soil compaction is a function of: 1) Water content 2) Compactive effort 3) Soil type A colluvial soil is a soil that was formed by transportation of the soil particles by gravity, such as down a slope to the base of the slope True or False True The Three major classifications that is Identified through the USCS are: Course- grained Soils Fine- grained Soils Highly organic soils Compaction of Fine Grained Cohesive Soils examine the effect of water on: -Soil structure -Hydraulic Conductivity - volume change behaviour -Shear Strength the basis for weight- volume calculations is the assumption that the W(s), V(s) and G(s) of the soil DOES NOT CHANGE from the borrow area to the compacted fill. True or False True the design requirements of the Compacted Clay Liner (CCL) for a Municipal Solid Waste Landfill: - MINIMIZE HYDRAULIC CONDUCTIVITY - Adequate shear strength - Shrink/swell behaviour - Deform without cracking and minimize compressibility - Resistance to chemical attack - Workability and constructability - Availability of materials - Cost It is the total head that determines flow of water in soils. No change in total head from one point to another in a soil, no flow of water. True or False True Slug Test are used to determine the hydraulic conductivity of the formation in the immediate vicinity of a monitoring well screened interval. - it involves injecting or withdrawing a known volume of water from a well and monitoring formation's response by measuring the rate at which the water level returns to equilibrium. Analysis of 1-D Permeameter Systems: - Velocity head is negligible - All total head is lost in the soil - no total head lost in the open permeameter tube, reservoirs or very coarse particles. - Negative pore pressures can exist - Flow direction determined by total head gradient - Method of head component determination: - Start at flow boundaries - For heads in soil, first determine elevation head and total head, calculate pressure head - Uniform loss of total head in uniform soils Flow nets are useful for assessing: - Seepage losses from reservoirs - Pore pressures on structures (eg. uplift pressures) - Pore pressures and seepage velocities in dams - Critical points with respect to stability and erosion of water retaining structures (e.g. examine hydraulic gradients) You cannot have a flow line in parallel to an equipotential line because total head doesn't change along the equipotential line. (flow lines must always be perpendicular) True or False True One process that holds water molecules to a clay mineral particle surface is the attraction of dipolar water to the negatively charged clay mineral particle True or False True A residual soil is a soil the was formed by transportation of the soil particles by gravity, such as down a slope to the base for the slope. True or False False A flocculated clay structure has clay mineral particles in a face- to- edge, "cardhouse type" orientation and is formed when there is net attraction between the particles True or False True Compacting a cohesive, clayey soil on the dry side of optimum moisture content contrasted with the wet side of optimum will give the soil higher potential for drying shrinkage. True or False False the relationship between zero air voids dry unit weigh and moisture content is linear on a graph of dry unit weight versus moisture content True or False False Hydraulic conductivity depends on the viscosity and unit weight of the permeating fluid True of False True If there is no change in total hydraulic head from one point to another in a soil mass, then there is no flow of water True or False True Negative pore cannot occur in a 1-D permeameter system with steady state seepage because water will be in a state of compression with steady state seepage. True or False False In a stratified soil system ( with soil layers of differing hydraulic conductivity values) with horizontal flow parallel to the stratification, the horizontal hydraulic gradient across each of the layers is different. True or False False In a soil deposit, the horizontal hydraulic conductivity is typically greater than the vertical hydraulic conductivity True or False True Seepage velocity is determined by multiplying the discharge velocity by porosity of the soil True or False False In a flow net for seepage through an embankment dam, the change in pressure head is equal to the change in elevation head along the top flow line. True or False False Effective stress is less than the actual contact stress between the soil particles True or False True Given a 1-m deep pond overlying a course gravel layer, if the depth of the water in the pond increases to 2-m, the effective stress within the gravel will increase by 9.81 kN/m^3 True or False False Water will rise higher above the water table in a clay rather than a sand because the size of the interconnected pore spaces of a clay are smaller that those of a sand True or False True The pressure in capillary water above the water is equal to atmospheric pressure. True or False False