Soil Dynamics and Machine Foundations

Code No: R42018

R10

Set No. 1

IV B.Tech II Semester Supplementary Examinations, July - 2014

SOIL DYNAMICS AND MACHINE FOUNDATIONS

(Civil Engineering)

Time : 3 hoursMax. Marks: 75

Answer any Five Questions

All Questions carry equal marks

Design charts of Pauw’s and Sung solutions and Code books IS2974 - Part-II - 1980 and

IS2974 -Part-I - 1982 are allowed in the examination halls

1. a) Define the following terms

i) Natural Frequencyii) Critical Damping

iii) Period andiv) Spring Constant

b) A machine foundation can be idealized as a mass-spring system. This foundation can be subjected to a force that can be given as Q(b) = 8000 sin(ωt). Given f = 800
cycles/min. Weight of the machine + foundation = 2 kN, spring constant = 750 kN/m. Determine the maximum and minimum force transmitted to the subgrade

2. a) Explain about the foundation soil system as Spring dash pot system with assumptions

b) The following data was obtained in a cyclic plate load test, using a plate of size 0.3 m
x 0.3 m.

Load Intensity

(kN/m2)

Settlement

(mm)

250500

0.50.40.950.8

75010001500

1.61.252.51.93.62.6

Plot the necessary graph and determine the values of cu for the Base area of 10m2 foundation block.

1 of 2

|''|'||||''|''||'|'|

Code No: R42018

R10

Set No. 1

3.a) What are the modifications made by Quinlan and Sung to Reissner?s theory?

Explain.

b) Elucidate briefly Pauw’s analogy of foundation soil system

4. a) Describe the procedure to determine the young’s modulus of soil under dynamic

loading conditions by means of block resonance test.

b) A field vibration test has been conducted at a site with a vibrator mounted on a footing of radius 24 cm. the weight of footing and vibrator is 250 kg. The vibrator produces an exciting force of 20 kN at a frequency of 15 cycles /second. The amplitude at operating frequency of 10 cycles/sec is 3 mm. what should be the coefficient of elastic uniform compression of soil. If the damping coefficient is 10 kg.sec/cm, determine the
percentage of error in amplitude at an operating speed of 15 cycles/sec.

5.Explain in detail about the principle of dynamic bearing capacity of Shallow foundations.

6.Design a suitable block foundation for a two cylinder compressor with the following

data:

Operating speed = 600 rpm. Vertical dynamic force = 5.5 t, dynamic moment = 5.9 t-m.

Safe bearing capacity of the soil 20 t/m2. Coefficient of elastic compression, cu = 4.5 x

103 t/m3.

7.Explain the Seismic stability of slopes by Swedish circle method.

8.Explain the concept of active isolation and the passive isolation with neat sketches.

2 of 2

|''|'||||''|''||'|'|

Code No: R42018

R10

Set No. 2

IV B.Tech II Semester Supplementary Examinations, July - 2014

SOIL DYNAMICS AND MACHINE FOUNDATIONS

(Civil Engineering)

Time : 3 hoursMax. Marks: 75

Answer any Five Questions

All Questions carry equal marks

Design charts of Pauw’s and Sung solutions and Code books IS2974 - Part-II - 1980 and

IS2974 -Part-I - 1982 are allowed in the examination halls

1. Derive the equation of motion of a single degree freedom damped model. Under what
conditions there will be under damped over damped and critically damped states?

2. a) Discuss about the Pressure bulb Concept in dynamics.

b) How do you determine the natural frequency of foundation soil system using Barkan’s
approach?

3. a) How do you analyse a block foundation based on elastic half-space theory?

b) Explain Quinlan and Sung’s modifications.

4. a) What are the laboratory methods used to determine the dynamic properties of soils?
Explain them in brief

b) The exciting force in a constant force amplitude excitation is 120 kN. The natural

frequency of the machine foundation is 4 Hz. The damping factor is 0.36. Determine the magnification factor and the force transmitted to the base with an operating
frequency of 10 Hz.

5. Explain the main differences between the static and dynamic capacity of shallow
foundations with the codal provisions

6. Design a suitable foundation block for a double acting steam hammer whose data are
given below. Weight of the falling ram = 5.0 t. height of the drop = 1.5 m. Area of the
piston = 0.2 m2. Average steam pressure on piston = 120 t/m2. Weight of the anvil =
100.0 t. base area of the anvil = 6.0 m2. weight of the frame = 1.5 t, which is fixed to the
foundation block. The thickness of the pad under the anvil is 0.60 m. ‘E’ of the material
of pad = 5.0 X 104 t/m2. Coefficient of impact (restitution) = 0.65.

Soil properties: coefficient of uniform compression = Cu = 4.5 X 103 t/m3. Mass density of soil = 1.9 g/cc. safe bearing capacity of the soil is 25 t/m2.

7. Explain the Seismic stability of slopes by Newmarks sliding block method

8. a) What are the locations of isolation of Bridges against seismic action?

b) Explain the basic properties of the good isolation materials.

1 of 1

|''|'||||''|''||'|'|

Code No: R42018

R10

Set No. 3

IV B.Tech II Semester Supplementary Examinations, July - 2014

SOIL DYNAMICS AND MACHINE FOUNDATIONS

(Civil Engineering)

Time : 3 hoursMax. Marks: 75

Answer any Five Questions

All Questions carry equal marks

Design charts of Pauw’s and Sung solutions and Code books IS2974 - Part-II - 1980 and

IS2974 -Part-I - 1982 are allowed in the examination halls

1. a) What are the different types of damping? Derive the governing differential equations
for the damped forced vibrations of single degree of freedom with the Coulomb
Damping.

b) For a machine foundation, given weight = 60 kN, spring constant = 11000 kN/m, and C = 200 kN-s/m, determine (i) whether the system is overdamped, underdamped, or critical damped (ii) the logarithmic decrement, and (iii) the ratio of two successive amplitudes (iv) the damped natural frequency.

2. Design a foundation for a Gas engine with a vertical cylinder and vertically oscillating
parts for the fallowing data:

Total weight of the engine = 4600 kg. Speed of the rotation 260 rpm. Unbalanced vertical force = 1 ton. Base dimensions of the engine 1 X 2.5 m. Elevation of the base above the
ground = 1m. Dense sand exists to a depth 6 m. weight of the moist soil 1.7 t/m3. Use
pauw’s Analogy.

3. What are the laboratory methods used to determine the dynamic properties of soils?
Explain them in brief.

4. Explain about the equipment required Block vibration test and its functions in the test.

5. Explain the main differences in principle between the static and dynamic capacity of
shallow foundations with the codal provisions

Soil properties: coefficient of uniform compression = Cu = 4.5 X 103 t/m3. Mass density of soil = 1.9 g/cc. safe bearing capacity of the soil is 25 t/m2.

7. Explain the Seismic stability of slopes by Newmarks sliding block method

8. What is main purpose of isolation? Explain the different types of vibration isolation.

1 of 1

|''|'||||''|''||'|'|

Code No: R42018

R10

Set No.4

IV B.Tech II Semester Supplementary Examinations, July - 2014

SOIL DYNAMICS AND MACHINE FOUNDATIONS

(Civil Engineering)

Time : 3 hoursMax. Marks: 75

Answer any Five Questions

All Questions carry equal marks

Design charts of Pauw’s and Sung solutions and Code books IS2974 - Part-II - 1980 and

IS2974 -Part-I - 1982 are allowed in the examination halls

1. a) Explain in detail about the Hysteretic Damping.

b) A foundation weighs 800 kN. The foundation and the soil can be approximated as a
mass- spring dashpot system as shown in Fig. 1. Given spring constant = 200000
kN/m, Dashpot Coefficient =2340 kN-s/m. Determine the following (i) Critical
damping coefficient, Cc (ii) damping ratio (iii) logarithemic decrement (iv) damped
natural frequency. The above foundation is subjected to a vertical force Q = Q0 sinωt
in which Q0 = 25 kN, ω = 100 rad/s. Determine the following terms: (v) the amplitude
of the vertical vibration of the foundation, and (vi) the maximum dynamic force
transmitted to the subgrade.

Fig. 1

2. a) Explain in detail, how the coefficient of elastic uniform compression can be computed
using Barkan’s method.

b) A spring - mass system has a spring stiffness ‘k’ N/m and a mass of ‘M’ kg. It has

natural frequency of vibration as 15 Hz. An extra 10 kg mass is coupled to ‘M’ and the natural frequency reduces by 2 Hz. Find ‘k’ and ‘M’.

1 of 2

|''|'||||''|''||'|'|

Code No: R42018

R10

Set No.4

3. a) What are the limitations of Reissner’s theory?

b) Design a foundation for a Gas engine with a vertical cylinder and vertically oscillating
parts for the fallowing data:

Total weight of the engine = 4600 kg. Speed of the rotation 260 rpm. Unbalanced

vertical force = 1 ton. Base dimensions of the engine 1 X 2.5 m. Elevation of the base above the ground = 1m. Dense sand exists to a depth 6 m. weight of the moist soil 1.7 t/m3. Use Pauw’s Analogy.

4. Explain the Block vibration test with a neat sketch and explain the interpretation of
results obtained in this test.

5. Explain in detail about the principle of dynamic bearing capacity of Shallow foundations.

6. Design a suitable block foundation for a two cylinder compressor with the following
data:

Operating speed = 600 rpm. Vertical dynamic force = 5.5 t, dynamic moment = 5.9 t-m. Safe bearing capacity of the soil 20 t/m2. Coefficient of elastic compression, cu = 4.5 x
103 t/m3.

7. Explain the Seismic stability of slopes by Swedish circle method.

8. a) List out and describe the remedial measures to be taken to reduce the amplitude of the
vibrations of existing machines foundation.

b) What are the properties of the good vibrating isolation material? List out and describe
the properties of any two vibration isolating materials.

2 of 2

|''|'||||''|''||'|'|