T H E P H A S E O F G E O T ECH NICAL

S T UDY F O R A N E W C O N S T RUCT IO N I N

A L B ANIAA U T H O R S : P R O F. D O C . L U L J E TA B O Z O ; M S C .

S K E N D E R A L L K J A ; M S C . B E S I A N X H A G O L L I ; M S C . A N I K O S H O ; M S C A R D I TA M A L A J ; M S C L O R E N A

H A R I Z A J

GENERAL

• In this paper is described the experience of geotechnical studies for two important facilities in

Bilisht and Seman Fier, Albania. The study is performed on two sites; Spot no 1 in eastern part

of Albania, and spot no 2 in western part of Albania.

• This paper provides a review of developments in use of in situ geophysical testing methods as:

seismic refraction; down hole, cross hole, geo-radar (GPR); cone penetration testing (CPTU)

standard penetration testing (SPT); dynamic cone penetration testing (DPSH), boring, sampling

according to the nature of soil with laboratory testing.

LOCATION SPOT 1

LOCATION SPOT 2

• Spot no.1 is a river terrace where there are present: silty clay, silty sand, sand and gravel.

• Spot no.2 a marine lagoon, where soft soils composed by silty clay, silty sand and loose sand

are present.

• From in situ testing we have results as below:

In spot no.1, using cross hole tests we had the possibility to compile tomographic cross-section

for the survey line. As it can be seen till 8m depth we find very weak soils (Vp< 0,33km/s), from

8m to 20m depth we have weak soils (Vp= 1-1,6km/s), and deeper we can find normal soils.

• The comparison of the data from different in situ tests show that the trend of the change of

“Vs” is the same, but the velocity has more rapid growth when is determined by seismic

refraction. In other part by SPT-tests and DPSH-test we have calculated the “Vs”, and we can

see the same trend of the behaviour of the soils, with small differences after 4m depth.

• From CPTU tests made in spot no.2, we can see another situation. From 4m to 12m we have

very low values of FR, also deeper 22m FR<1. This conclusion is confirmed also by change of

the shear wave velocity with depth.

LABORATORY TESTING

From undisturbed soils samples, we have made the following investigations:

• classification tests,

• one dimensional consolidation test,

• direct shear,

• triaxial tests.

LAYER LL PL PI g

unit % % kN/m3

Top Soil 51.3 up to 62.8 30.1 up to 31.6 21.2 up to 31.2 18.2

Sands and Silty Sands - - - 19.6

Clayey Silts 28.6 23.5 5.1 18.7

Soft Clays 52.5 26.3 26.2 18.5

LAYER Eeod

D.SH

CUU UCS

ϕ° c

unit MPa KPa KPa MPa

Clayey Silts 7.4 up to 21.7 19.0 up to 25.2 22.89 up to 75.8 384.3 up to 524.6 -

Sands &Silty Sands 9.12 17.7 up to 31.1 11.3 up to 52.9 - -

Sandy, Silty Gravels - 26.4 up to 51.1 9.2 up to 24.1 - -

Mudstones

&

Sandstones- - - 5.4 up to 28.0

• After investigations are finished, some graphs are compiled. In these graphs the difference

between modulus of deformation and friction angle vs depth can be noted. . If we made the

comparison between parameters determined by laboratory and in situ tests we can evaluate

that laboratory values are smaller than values determined by in situ tests.

As we can see from graphs friction angle

achieved different tests and different type of

soils is in the range between 20 and 50°.

We can see an increasing trend of friction angle

from more cohesive materials to less cohesive

materials.

By these results we can say that, the deposits of two spots are composed by weak soils.

•According to EC-8, in the empirical charts for simplified liquefaction analysis, for N60 value,

•VS<150m/s, grain size distribution, degree of consolidation DR= (40-60) %, and

amax= (0, 34-0, 42) g, in spot no.2 it is possible to appear the sand’s liquefaction from (4- 13) m

•Some layers are very deformable, E= (0, 2 to 0, 4).104 kPa.

As a result, different objects will be suffering from big settlements, and they can pass in

limit states (ultimate or service). To avoid these negative phenomena’s we are obliged to improve the soil.

Many solutions are in practice, but we will recommend two of them:

•Preloading for consolidation of very porous soils

•Consolidation by vertical drainages, realized by stone or gravel piles, and horizontal drainages.

The selection of the improvement soil’s method depends from time in disposition and financial possibilities.

CONCLUSION

• From our study we arrive in the following conclusions:

• For the problematic areas with weak soils, during investigation phase needs to combine

laboratory with in situ tests.

• Spot no.1 _ in this point we might have loss of stability and big settlements. So, before starting

the construction, it is necessary to improve the soils in manner to be less deformable.

• Spot no. 2 _ in this point we might have the sand’s liquefaction problem under seismic action

and big settlements. It is recommended that before construction a soil improvement is needed.

ACKNOWLEDGEMENTS

• The work presented here represents a collaborative effort between the authors and numerous

colleagues from “A.L.T.E.A & GEOSTUDIO 2000” ltd Company.

THANK YOU

Ani Kosho