Due to rise in temperature, the viscosity and the Unit Weight of the percolating fluid a reduced to 60% and 90% respectively. If other things remain constant, the coefficient of permeability
K1/K2 = Y1U2/U1Y2 . K2 = 0.90/0.60 = 1.50 means 50% increases
Coefficient of permeability of soil
1. Grain size ↑ 2. Void ratio ↑ 3. Particle shape → less for angular particles than rounded particles at the same void ratio. 4. Soil structure → More for soils with a flocculent structure. 5. Pore fluid properties → Decreases with the increase in viscosity 6. Adsorbed water (in clay) → Fine-grained soils contain a layer of water strongly attached to the particle surface that is known as adsorbed water. Adsorbed water is not free to move under gravity and hence reduces the effective void space available for fluid flow 7. Impurities and foreign matter
The average coefficient of permeability of natural deposits
permeability in the horizontal direction parallel to the stratification is many times that in the vertical direction perpendicular to the stratification
The total discharge from two Wells situated near to each other is
The flownet for an earthen Dam with 30 metre water depth consists of 25 potential drops and 5 flow channels. The coefficient of permeability of dam material is 0.03 mm/sec. The discharge per metre length of dam is
Discharge Q = KH Nf/Nd x L = 0.03x30x5x1/25/1000 = 0.00018 m3/sec
The most suitable method for drainage of fine grained cohesive soil is
Electro-osmotic method is used when co-efficient of permeability lies between 10-7cm/see to 10-5 cm/sec. In electro-osmotic method, two electrodes are driven into the saturated cohesive soil
Total number of stress components at a point within a soil mass loaded at its boundary is
The intensity of vertical pressure directly below a concentrated load of 3/2π tonnes at a depth of 3/2π is given by
Vertical stress on a vertical line at constant radial distance from the axis of a vertical load
Phreatic line in an earthen dam is
Hydrostatic pressure acts below the phreatic line whereas atmospheric pressure exists above the phreatic line. This line separates a saturated soil mass from an unsaturated soil mass.
The hydrostatic pressure on the phreatic line within a dam section is
Rate of consolidation
Consolidation is the process in which reduction in volume takes place by expulsion of water under long-term static loads.
The unit of the coefficient of consolidation is
Cv = d2/t cm2/sec
Terzaghi eqn
Where, u = Pore water pressure z = thickness of soil sample t = time of consolidation
The slope of isochrone at any point at a given time indicates the rate of change of
Isochrone:- A line on a diagram or map connecting points relating to the same time or equal times.
Within the consolidation process of a saturated clay
Consolidation is the process in which reduction in volume takes place by expulsion of water under long-term static loads.
The value of compression index for a remolded sample whose liquid limit is 50% is
Compression index is extremely useful for determination of the settlement in the field. Compression index of clay (a) For undistributed soils, Cc = 0.009 (LL-10) (b) For remoulded soils, Cc = 0.007 (LL-10) In question given remoulded soil sample Cc = 0.007(50-10) Cc = 0.28
Which one of the following clays behaves like a dense sand?
Coefficient of consolidation of soil is affected by
K/Cc is directly proportional to Cv
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