B.E. Geotechnical Engineering – I- Mumbai- December 2019
MUMBAI UNIVERSITY
Subject: Geotechnical Engineering – I
Semester: 5
[Total Time: 3 hrs]
[Total Marks: 80]
N.B. 1) Question No. 1 is compulsory.
2) Attempt any three from the remaining five questions.
3) Figures to be the right indicate the full marks.
4) Assume suitable data if not given and justify the same.
Q. 1) A) Explain the scope of geotechnical engineering in the design of earth retaining structures. (5M)
b) Show the energy supplied in light companion test is 592 Kilojoule per cubic meter. (5M)
c)A lake full of water up to a depth of 10m and soil below its bottom surface is saturated clay with ysal= 20kN/m3 and unit weight of water is 10 kNm/m3. Calculate the effective stress at a depth of 5m below lake bed level. (5M)
d) Explain the validity of Darcy’s law for the determination of permeability of soil. (5M)
Q. 2) A) Explain the quicksand condition and derive the expression for a critical hydraulic gradient. (5M)
b) The bulk unit weight of soil is 17kN/m3 and water content is 12%. Calculate the void ratio of soil if G= 2.65 yw= 9.8 kN/m3(5M)
c) A soil sample has a liquid limit of 20% and a plastic limit of 12%. The following data are also available from sieve analysis. (10M)
| Sieve Size | % Passing |
| 4.72 | 90 |
| 0.425mm | 85 |
| 0.075mm | 38 |
Classify the soil according to IS Classification system.
Q. 3) a) In an unsaturated specimen of clay has a volume of 19.5cc and a mass of 31gm. On oven drying the mass reduces to 18gm. The value of dry specimen as determined by the displacement of mercury is 10cc. Determine shrinkage limit, specific gravity, shrinkage ratio, and volumetric shrinkage. (10M)
b) A dry soil has a porosity of 25%. Find how much water is required to saturate 1 m3 of this soil. (5M)
c) Explain the methods used to determine the in-situ permeability. (5M)
Q. 4) a) Explain the characteristics of flow net. (5M)
b) Explain the factors affecting the compaction. (5M)
c) In a falling head permeability test the length and area of cross section of soil specimen are 0.17 m and 21.8 x 10-4 m2 respectively. Calculate the time required for the head to drop form 0.25m to 0.10m the area of the cross-section of the standpipe is 0.002 m2. The sample has three layers with permeabilities 0.00003 m/sec for first 0.06 m, 0.00004m/sec for second 0.06 m and 0.0006 m/sec for third 0.05 m thickness. Assume the flow is taking place perpendicular to the bedding plane. (10M)
Q. 5) a) Calculate the equivalent permeability in horizontal and vertical direction of soil deposit consisting of three Layers 150 cm, 180cm, and 200 cm thick with permeabilities 10-5, 10-7, and 10-9 m/sec respectively. (5M)
b) 1000m3 of earth fill is to be constructed. How many cubic meters of soil is to be excavated from a borrow pit in which the void ratio is 0.95 if the void ratio of earth fill is to be 0.7 (5M)
c) Explain different methods of boring for soil exploration. Cover exclamation point-wise duly supported by diagrams. (10M)
Q. 6) a) A fully saturated sample of clay was found to have a specific gravity of 1.01 and water content of 29% The soil sample was oven-dried and its mass specific gravity was found to reduce to 1.83. Calculate the shrinkage limit of soil. (10M)
b) Using the given data, classify the following soil as per IS 1498.
a) Liquied limit = 40%, Plasitc limit = 22% (2M)
b) Liquied limit = 20%, Plasitc limit= 14% (3M)
c) Passing 75u sieve =10% (5M)
Pasing 4.75 umm sieve 70%
Cu = 8, Cc= 2.8 and Ip (plasticity index) = 4%