CONTENTS

J. Duhok Univ., Vol.14, No.1 (Pure and Eng. Sciences), Pp 39-51, 2011
field density and lift thickness for the dam
embankments in case when such materials are
mechanically reliable and needed.
2. MATERIAL AND METHODS
Derbendi Gomasbpan was chosen for the
dam site based on the available ground
conditions required for a dam construction in
this site, including, the geomorphological
characteristics, permanent water flow and over
all, the engineering geological properties of the
rocks which include, the rock types, their
structural features and their physical and
mechanical characteristics. The study of these
properties is required during the planning and
designing of the dam foundation and abutments
as well as for the stability of the dam
embankments and the slopes around the
reservoir.
This study started with the site investigation
for the dam site and surrounding area, The
general information about the physiography, the
lithostratigraphy, the surface water flow and the
geologic structures such as the attitude of strata,
their thicknesses, discontinuities characteristics
and others were collected. Rock sampling from
the proposed dam site was also carried out
during this stage of work. Figures (3) and (7).
Sixteen rock samples were taken from the
Pila Spi dolomitic limestone for the laboratory
testing, most of them were tested directly in the
field, Figure (4). This rock was considered to be
designed for the dam foundation and its
abutments., The dolomitic limestone samples
were tested for their strength indexes using the
point load strength test device, Broch, E and J.A.
Franklin, (1972), Figure (4). The point load
strength index (Is) of each tested sample, was
corrected (Is50) to the size of 50 mm diameter by
using the correction factor f = (D/50) 0.45 ,then
(Is50) = f x (P/D 2 ), were: P = the applied load
in Newtons, and D = the distance between the
load points in mm, and (P/D 2 )= Is
The resulted values were determined and
later on converted to unconfined compressive
strength (UCS), using the equation adapted by
D’ Andrea et, al., (1965). The tangent modulus
of elasticity ( Et50) was also determined using the
equation adapted by Irfan T.Y. and Dearman W.
R. (1978), as following:
UCS = 15.296 x Is50 + 16.375
Et 50 = ( 0.588 x Is50 + 0.084 ) x 10 4
The results of the point load strength tests
and the other engineering properties of the
dolomitic limestone are listed in table (1). The
joints spacing range ( the range of distances in
cm between two parallel and adjacent planes of
joints of any set or orientation. ) was the only
joint characteristic used and needed in this study.
Each of these 16 joint spacing ranges, showing
on the table (1), was taken within a square meter
of the surface area of each specific location or
spot on the outcrop, Palmstron, A., (1982), at
which the rock sample was taken from and the
procedure was integrated for the whole
exposure.. The range values of these spacing in
each specific sampled location might be close in
the range values to that of the next spot
locations.
NE SW
Fig. (3): The bedding attitude & Discontinuities of the Pila Spi Limestone at the dam site.
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