assNATIONAL INSTITUTE OF TECHNOLOGY: TIRUCHIRAPPALLI – 620 015B.TECH CIVIL ENGINEERING

ASSIGNMENT-I

CE208 GEOTECHNICAL ENGINEERING-II

1. What sort of expertise would be needed to choose the borehole depth and number in a soil investigation?

2. How do you analyse the samples obtained after sampling for strength if they are fine sand, over-consolidated clay and soft sandstone?

3. Discuss the factors which are relevant to the planning of a well-balanced exploration programme.

4. If you are in charge of subsoil exploration of important structures, how do you decide the depth of exploration? List the factors you will consider and their importance.

5. What is the area ratio of a Shelby tube with an outer diameter of 3in and an inside diameter of 2.874in?

6. A soil profile is shown in Fig. 1, along with SPT (N) values in the clay layer. Determine the variation of cu and OCR with depth.

7. A cone penetration test was conducted in a deposit of normally consolidated dry sand (normally consolidated). The following table gives the results of the test:

Depth (m) Point resistance of cone, qc (MN/m2)1.5 2.053.0 4.234.5 6.016.0 8.187.5 9.979.0 12.42

Dry sand, =17kN/m3

Sand, sat=19kN/m3

Clay, sat=17kN/m3

SandFig.1

2.0m

2.0m

GWT

2.0m

2.0m

2.0m

2.0m

N6

8

6

4

6

Assume the dry unit weight of sand to be 16kN/m3. Estimate the average angle of internal friction (φ’) and the average relative density Dr.

8. In the soils profile shown in Fig.2, if the cone penetration resistance (qc) at A, as determined by an electric friction-cone penetrometer, is 0.8MN/m2 , find

(i) The undrained cohesion (ii) The OCR

9. The result of a refraction survey at a site are given in the following table:

Distance from the source of disturbance (m)

Time of first arrival of P wave (secx103)

2.5 11.25.0 23.37.5 33.510.0 42.415.0 50.920.0 57.225.0 64.430.0 68.635.0 71.140.0 72.150.0 75.5

Determine the thickness and the P-wave velocity of materials encountered.

4.0m

A

Clay, =18kN/m3

Clay, sat =20kN/m3