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Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
ME SEMESTER-I • EXAMINATION WINTER 2017
Subject Code: 2714306 Date:09/01/2018
Subject Name: Soil Improvement Technology
Time: 02:30 PM TO 05:00PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1

Discuss in detail concept, principle, methodology, applications and limitations of various soil improvement methods used for cohesive soils based on IS: 13094.
07
Q.1

Explain the mechanism and construction methodology of each method mentioned below and discuss (any two) in detail with neat sketches, formulas/equations and plots:
CNS ii) Electrokinetic Injections iii) Soil Nailing iv) Electro Osmosis
07
Q.2

A compacted fill is to be constructed of the two potentials borrow pit areas A B. The in-situ properties of soil at sites are as follows:
Borrow Area void ratio(en)= 0.8, water content(%wn)= 17.65% and Gs 2.65, Borrow Area void ratio(en)= 0.68, water content 14.25% and Gs 2.65, The compacted volume of the embankment will be 50,000m3. Unit weight is 20 kN/m3 at a placement water content of 20%. Soil from the borrow area is to be excavated and transported to the site in truck of 10 m3 capacity. During excavation and dumping of soil in the trucks, soil increases in volume by 10%. At the site, additional water which is added to soil and compacted to desired extent by pneumatic rubber tired rollers. The cost of excavation, transportation and compaction is Rs. 600 per truck for borrow area A Rs. 800 per truck for borrow area B. Water charges per truck is Rs. 250. Which of the two borrow area is more economical?
07

The compaction of an embankment is carried out in 250mm thick lifts. The rammer used for compaction has the foot area 0.04m2. The energy developed per drop of the rammer is 36kg-m. Assuming 50% more energy in each pass over the compacted area due to over-lap, calculate the number of passes required to develop compactive energy equivalent to IS light compaction for each layer.
07
OR

Calculate the time required for 50%,70%and 90 consolidation of a saturated clayey silt soil using wick drains at various triangular spacings. The wick drains measure 100 4 mm and has a Ch 6.5 x 10-6 m2/min.
07
Q.3

What do you understand by cement stabilization? Enlist all the factors kept in mind while designing cement stabilization or the factors affecting the performance of soil-cement mixtures.
07

Stone columns were constructed in deposit of soft clay soil. Given clay,
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undrained cohesion is equal to 35kPa. Modulus of elasticity Es 9700kPa. Stone column diameter (for each column) 0.5m, c/c spacing 2.5m. Column foundation: plan 1m 1m c/c spacing of column 3m, Depth of foundation Df 1m, Load on column 400 kPa, Estimate settlement of column foundation.
OR
Q.3

Define grouting and discuss the various methods of grouting on functional basis. Differentiate fine grouts and coarse grouts with respect to penetrability.
07

A 15m thick hydraulically isotropic clay stratum overlies an impervious stratum. If the Cv 5.5 x 10-4 cm2/sec. Find the time required for 50% consolidation. In order to accelerate the rate of settlement, vertical sand drains of 1m dia were installed at 5m c/c. Calculate how much settlement is accelerated due to provisions of sand drains. For n Tr 0.081 for Ur 50%.
07
Q.4

Discuss (any two)in detail with reference to soil-cement mixtures from the following with neat sketches, formulas/equations and plots:
Compressive strength, modulus of elasticity, plasticity index ii) Degree of pulverization, moisture content, density iii) Soil Amendments and additives.
07

Explain lime stabilization in detail and also discuss the role of various stabilizing agents in development of strength.
07
OR
Q.4

Explain in detail bituminous stabilization. Under which soil conditions they are preferred? Classify the various bituminous stabilized mixtures with their applicability.
07

A silicate grouting is to be done at a place where the permeability of the alluvium to be grouted is 1.21 x 10-3 cm/sec and the porosity of the alluvium is 30% at an injection pressure of 7kg/cm2. The internal radius of the grout pipe is 2.5cm. The properties of the grouts: density of grout 1.16gm/cc, ratio of viscosity of grout to that of water 2.5 and gelling time of the grout 50min. Compute the radius of the grout front at the gel time of the grout in the formation.
07
Q.5

Enlist the various physical properties needed for grout mix design for both fine grouts and coarse grouts. How they are determined? Explain the determination of any three properties in detail with neat sketch and justify its importance in grout mix design.
07

For a dynamic compaction test, given: weight of hammer 15 metric tons, height of drop 12m. Determine the significant depth of influence for compaction in meter.
07
OR
Q.5

Enlist various methods employed in stage grouting. Explain the down stage without and with packer with neat sketch.
07

Enlist various types of chemical grouts. Which properties are governing the design of chemical grouts? Discuss any two type of chemical grout in detail.
07