1/2
Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
ME SEMESTER-1 EXAMINATION WINTER 2018
Subject Code: 3714310 Date: 03/01/2019
Subject Name: Ground Improvement Techniques
Time: 02:30 PM To 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full mark
Q.1

Why ground improvement methods are required and under which type of soil conditions they are adopted? Summarize various ground improvement methods for cohesive soils as per IS: 13094 based on their principle, suitability, advantages and limitations.
07
Q.1

Explain overall the mechanism of admixtures in soil stabilization process. Which engineering properties are generally altered and why? How the selection of method is done?
07
Q.2

Explain the principle of each method mentioned below and discuss (any two) in detail with neat sketches, formulas/equations and plots:
Prefabricated vertical drains ii) Stone columns iii) Vibroflotation
07

A sample of soil compacted according to the standard proctor test has a density of 2.18 g/cm3 at 100% compaction and at an OMC of 13%?What is the dry unit weight? What is the dry unit weight at zero-air voids? If the voids filled with water what will be the saturated unit weight? Assume G 2.67.
07
OR

The compaction of an embankment is carried out in 300mm thick lifts. The rammer used for compaction has the foot area 0.05m2. The energy developed per drop of the rammer is 40kg-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
Q.3

Stone columns were constructed in a deposit of soft clay 6m thick, with undrained cohesion value 38kN/m2, Es=9750 kN/m2, stone column= diameter of each column 300mm, c/c spacing 2.5m, dimension of column foundation =1m x 1m, c/c spacing of columns 3.5m, depth of foundation 1m, load on columns 350 kN/m2, Estimate the settlement of the column foundations. Assume constant A1 0.94, A2 0.6, Af/As 5.3,Sf/Ss 2.1.
07
2/2

Explain in detail with bar chart penetrability of coarse grouts and fine grouts.
07
OR
Q.3

Enlist the various physical measurements for grout mix design. Discuss any three in detail.
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

Compute the flow rate q for an injection pressure equivalent to 100m of water-head, if an injection hole has a diameter of 40mm and 0.5m length of hole is exposed at any one time, if its kG 10-5 m/sec corresponding to a clean fine sand.
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 1.25 x 10-3 cm/sec and the porosity of the alluvium is 36% at an injection pressure of 6kg/cm2. The internal radius of the grout pipe is 2.5cm. The properties of the grouts: density of grout 1.18gm/cc, ratio of viscosity of grout to that of water 2.5 and gelling time of the grout 45min. Compute the radius of the grout front at the gel time of the grout in the formation.
07
Q.5

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

Discuss in detail frame work approach, conceptual frame work approach, equivalent weight approach of grout mix design.
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 grout is more popular in field? Discuss any one chemical grout in detail.
07