N-Values
337
46
a1
3365 [°°
51
26
SY
Figure 2: STP N values at 0.91 m depth.
(b) Two white lines are drawn in Figure 2 to show where ¢ = XXXXXXXXXXand when g =
33.66.
(i) Sketch S as a function of g when ¢ = XXXXXXXXXXThis is the cross-section of
S(¢,g) when ¢ = 73.205.),
(ii) Sketch S as a function of £ when g = XXXXXXXXXXThis is the cross-section of
S(¢,g) when g = 33.66.)
(c) Three points, P, Q and R are shown on Figure 2.
(i) For which of these points is a <0?
(ii) For which of these points is - > 07
(Note: more than one point may satisfy each condition.)
3. Geotechnical engineers use a procedure called the Standard Penetration Test (SPT) to
provide information on geotechnical properties of soil. The SPT measurement is given
as a positive integer (whole number) between 1 and 50 and this is known as the SPT N
value. (You can read more about the SPT in wikipedia, for example.)
A group of geotechnical engineers have recently published a study on soil properties in the
egion near Islamabad in Pakistan [1]. They produced a series of contour maps showing
the SPT N value at various soil depths. Two of these contour maps are shown below
(Figures 1 and 2). These maps have been annotated for the purpose of this assignment.
In Figures 1 and 2, the horizontal axis is latitude which we will denote by £ and the vertical
axis is longitude which we denote by g. We give the SPT N value the mathematical
symbol S. Hence we can write S = S(, g) or, in words, SPT N is a function of latitude
and longitude.
N-Values
33.7
46
41
33.65 ad
31
26
33.6 21
Figure 1: STP N values at 1.52 m depth.
(a) In Figure 1, there are three points marked, A, B and C on the contour plot fo
STP N. What is the feature of the contour plot at each of these points? (There
is a different feature at each point.)