Behavior Geotechnical and Geologic of the Grounds

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Behavior Geotechnical and Geologic of the Grounds
Behavior Geotechnical and Geologic of the
Grounds Northeast Algerian Affected by the
Landslides
A.Saihia and M. Meksaouine
Faculty of Engineering Sciences University Badji Mokhtar Annaba Algeria
E-mail: [email protected], [email protected]
yellowish end and marly limestone of the miopliocène [1].

Abstract—Landslides made the ir appearance with the current of
the decade 1990 and the beginning of y ears 2000 on muc h of
places of the to wn of Constant ine and its area which extend s to
north to the M editerranean. These slips appeared after a rainy
climate repeated over successive years. Acc ording to the results
of analyses on s ites, lit hology, th e microtectonic one, water, the
slope of t he r elief, are t he prin cipal cause s. The geolog y of
northern of Constantine is cha racterized by the presence of clay
and ma rl. Th e com plexity o f th e c lay s oils, t heir capac ity o f
saturation, th e deterioration of t he rock s a nd their fast
degradation by seepage waters in these zones are as many factors
favorable to th e re lease and the acceleration of t he landslides.
Geological research and meticulous geotechnics were carried out
on th e site s accompanied by s eries b y measurements by
inclinometer, and piezometers
Keywords—Landslide, north east
inclinometer
Fig. 1. Situation of the zone of slip
Algeria, geotechn ical, c lay,
They are overthrust folds created by the compression of with
the sep aration of the plate Euro- African.Slip of t he
sedimentary layers of basins was carr ied out on more 100km
north in the s outh by the g one up vo lcanic ones r eleased by
underground e nergy [2],[3]. On these bloc ks of sedimentary
basins o ne meets layers o f s ame al ternations and th e var ious
alternations cau sed by the anticlines effects. O ne meets o f
them the sa me types of clays and marls in the borders of the
south of Europe [4].
I. INTRODUCTION
N
orth east of Algeria knew l ately o f t he significant
losses caused by the landslides (see fig. 1).These losses are in
general var ious ty pes of constructions: Transportation r oads,
works o f publ ic works, zones o f new or old agglomerations.
Movements o f grou nd ar e no t noticed th at i f th ey have one
impacts on the company or the economy of the country .These
landslides have t he sa me cha racteristics from the point o f
view:
- form (opening, depth, rate of travel...);
- unst able co nditions ( climate, geol ogy, topog raphy o f the
ground, microtectonic...);
- d amage (fissured buil dings made uni nhabitable,
significant dep ression o f r oad section, works communication
made impracticable (bridges, viaduct...).
B. Geotechnic
On all the sites the depth of the slips is of an average of 25
with 35m this was deter mined by surveys, tests inclinometric
and p iezometric . G
eotechnics tests relat e to t
he
physicomechanical pr operties of the grounds; the latter gave
appreciably similar results on all the area, characterized by a
very s ignificant s welling of clays and marls at the p oint of
internal loss o f cohesion of t he rock which caused a r upture
by shearing. The complexity of absorption of water has a role
essential in their behavior and consequently in he behavior of
the ground on the sur face and in-dep th [5]. I n a gr ound
containing of fine materials (clays and silts), the variations of
the wa ter c ontent h ave e ffects o n i ts mechanical pr operties:
absorption i nvolves a reduc tion in the shear strength, t he
desiccation involves on the c ontrary an improvement of these
properties on a small scale and on a large scale of the cracks
and cracks more or less profound appear [6].
II. GEOLOGIC AND GEOTECHNICAL ANALYSES
A. Geology
The geology of the northern of constantine is
characterized by sedimentary formations made up primarily of
clay and sandstone of Smendou, with appearance of
alternation of clay at least schistous, black color, likings
88
© 2014 UTA
A.Saihia and M. Meksaouine
Journal of Advanced Sciences & Applied Engineering Vol. 01, N° 01 (2014) 88-91
contributed to determine in a precise way the facts of the case
[12].
While basing onesel f on the index of plasticity an d the
argillaceous fraction, one can have various behaviors of clays.
According to Ske mpton, the value of th e A c (activ ity of
clays), whi ch by d efinition is the fraction of the index o f
plasticity (I P )(%) wit h t he co ntent o f c lay, ref lects the
mineralogical character directly. Thus, we will have:
Ac<0,75 i nactive clay, 0,75 <Ac<1,25 no rmal cla y, Ac>1,2 5
clay active) [7].
The results of the LTP Est (Laboratory of the Public works of
the EAST) give values for the IP (index of plasticity) ranging
between 3 5% and 40% and for th e WL (li mit of l iqidity)
between 55% and 60% at the end of October 2005 [8]. Other
tests car ried o ut at the en d o f Febr uary 2 006 gave f or like
results between 35% and 45% for the IP and between 60% and
75% for th e WL. Of such v alues are cl ose to the l imiting
values whi ch ar e abo ut 80% in clays
and th e marls o f
Constantine a ccording t o t he r epertory of th e Alg erian
laboratories o f the gr ounds. ( the gy psum inflates i n the
presence of water and becomes lubricating, which will explain
the disorders observed on the surface) [9].
In addi tion, of th e shear tests to the t riaxial apparatus o n
clays determined angles of repose natural ranging between 3°
and 6°; th ey are values clo se t o the rupt ure for the in clined
grounds. In the curve of Talbo t, cl ays reach porosity i n
0.84 [10]. I t is n oticed
that the indices o f p lasticity are
slightly homogeneous where they are definitely higher, which
explains the te ndency t o the ground hea ving. The cla y o f
mio-pliocene has coe fficients o f c ompressibility vary ing
from 0,188 to 0,28 7 [11]. These values c orrespond for the
majority of the surveys.
Fig. 2. Representation of the limit of the circle of slip
They are t he results of the investigations of the partner of
geotechnical recognition u sing cored survey s, statements
piezometric, inclinometric ( see fi g. 3 ) and to pographic, t he
taken samples w ere t he sub ject o f ph ysical an d mechanical
identification and were u sed for a study of s tability b y
estimating the safety coefficient with proposal of solutions of
confortement adapted t o the site and the problem arising (see
fig. 2).
B. Site of Mila 2
The analysis of the landslide assigns the city 185 residences to
Mila and its approximately near, of a population of more than
3000 inhabitants (s ee fig.4).T he causes o f this sli p are mainly
by the e ffect o f wa ter, the na ture o f the gr ound and with the
slope of the ground. The pr eliminary tests sho wed that the
ground is suited to construction, the constraint of the ground is
about 1.2 bars and surmounted layers are those of marly clay.
After one year of provisional acceptance of work of a phase of
40 residences, it was noted only the ap pearance of the macrocracks on the l evel of the walls of a building and widening of
the expansion joints (see fig.5) which are propagated towards
the foundations. Progressively the phen omenon observed
epugnant of other buildings.
III. ARIOUS SITES OF SLIP
This instability of ground is regional it affects 4
departments (Constantine, Mila, Jijel, Bejaia), this problem is
shown only i f the condition s necess ary are met ,i t is
emphasized by media and economic importance.
* In Constantine more than 20% of the perimeter of city which
counts more 5000ha
* I n Mila department t he motorways of Sétif-Constantine
(RN5) road section of Chelghoum Laid on 250m, The viaduct
of Oued Dib, abutment rivets southern on the RN 27 i n the
district o f Grarem (Mila), New ag glomeration of 185
residences on the level of the place head.
* In Jij el depar tment, road (RN27) Con stantine- Jijel wit h
SEBARI section of 300m .
* The town of Bejaia districts of Smina, Sidi Ahmed, Brise de
Mer in Bejaia more 600ha.
C. Site of Mila 3
The layout of the section of motorway Sétif –
Constantine), sectio n r oad of Chelghoum Laid on 250m,
crosses ge ological formations t o d ominant ar gillaceous, of
age mio-pliocene. Surface topography constitutes a slope with
relatively weak slope where the relief has a moutonnée surface
which co uld reflect pal éo-slips. Our own
investigations,
carried ou t on these movements o f mass, spread ou t in t ime,
enabled us t o estimate the width of th is ge ological r isk. The
recognitions of g round are distr ibuted over t hree p eriods and
taking place in at the end of November 2005, at the beginning
of January 2006 and end Mars 2007. We noted that these slips
are of rational type, planar whose surface of separation is not
very deep. T he faces of deta chment o f t he various s lips c an
reach the uneven significant ones and the volume of materials
moved can be estimated at several hundred or thousands cubic
meters in certain cases.
A. Site of Mila 1
During the realization o f the viaduct o f Ou ed D ib of Mi la
department, earthmovings surrounding the Southern abutment
Constantine side, appeared, wi th falls invading the trunk road
RN 27.
It is the e mbankment of acc ess of t he so uthern abut ment; at
summer set u p by co mpany (COG E-FAR. Italy) ; who was
affected by a system of r uptures sign ificant an d generalized
under form opening o f cra cks macroscopic on the in-d epth
surface and found by th e surveys in depth . The object of this
study, is to show the relevance of the use combined of several
methods o f investigation, su rface and in -depth h aving
89
© 2014 UTA
A.Saihia and M. Meksaouine
Journal of Advanced Sciences & Applied Engineering Vol. 01, N° 01 (2014) 88-91
realized on these neuralgic sites did not have the effect and to
hope for stabilization of these slips.
In the current state it is difficult to bring a radical solution to
this problem, however deepened geological investigations, and
with the support of other adapted analyses, could contribute to
a stabilization of these catastrophic slips.
D. Site of Jijel
The study relates to a vast landslide located on
principal road R.N. 27 between Constantine and Jijel, close to
the vi llage of Sebari whose ruptu re occu rred wit hin a marly
clay f ormation af fecting th e road on a great sectio n. Usin g
piezometers one could raise uncertainty on t he localization of
the slip surface, we examined various assumptions which took
account of morphological features and the geometry of the soil
horizons. It was conside red a sing le s urface who se p osition
was located only at its two ends:
- a hig h zone bein g locat ed in the princip al nic he of
wrenching at altitude 500.00 (NGA).
- a lo w zo ne l imited b y t he ap pearance o f th e pad s at
altitude 480.00.
We also ex tended t he slip surf ace upwards beyond t he
principal nic he t o visible cr acks of regres sion until at
altitude (510.00) in order to determine with more precision
the stabili ty of th e whole of the slope. From t he profiles
thus de fined a nd fixed on th e lo ngitudinal profile b efore
slip, it was implemented f our traditional m ethods of
analysis of stability: Method of Bischop (circular rupture),
method o f Fel lenius (circula r r upture), method o f Ju mbo
(noncircular Rupture), method of distur bance ( noncircular
rupture).
Fig.. 3. Inclinometric test result in the vicinity of the viaduct of O. Dib
E. Site of Bejaia
In this city the slip touched more than 600 ha, they are the
districts of Smina, Sidi Ahmed, Brise de Mer.
Fig. 4. Slip of the roadway quoted Smina
Fig. 6. Collapse of a construction quoted Smina
Constructions on loose grounds and inclined as it is in the case
in the southern side of the city, can lead to disorders of great
width. Instabilities were observed pri marily in the faded
grounds. The slip of S mina completely destroyed part of the
city and threat the stabi lity of the whole district ( see f ig. 6).
With least s trong precipi tation, the sli p wor sens endangering
human lives from where need for supervising the evolution of
the slip. Upstream, one is in t he pres ence o f a rot ational
standard slip which is spread out over a surface of more than
Fig. 5. Widening of the expansion joint quoted 185 residences
This exp ressway is affected in three places where the
roadway is seriously damaged. It proved that work of
confortement (works, sheeting piles, gabionnage, etc.)
90
© 2014 UTA
A.Saihia and M. Meksaouine
Journal of Advanced Sciences & Applied Engineering Vol. 01, N° 01 (2014) 88-91
-5.0
600ha. A s the thalweg narr ows, the slip i s transf ormed int o
muddy castings. This slip threatens a whole district now.
0.0
5.0
10.0
displacement ( cm.)
15.0
20. 0
25.0
30.0
35.0
0.0
F. Site of Constantine
Classified s ites as u nstable represent an ext
ent of
approximately 195 ha ( that is to say 3.9% o f the total surface
of the ci ty) an d ex pose more t han 1 00 000 i nhabitants, t he
equivalent wi th approximately of 15.38 % o f the t otal
population o f t he city. T he final delimitation o f the unst able
grounds by slips is not finalized yet [13], [14].
That means the question of the instability of the grounds with
Constantine deser ves a very detailed attention. Beca use the
town of Constantine, the metropolis of the East, is on the one
hand, a p lace o f ver y s trong de mographic concentrati on.
Observations on ground (see fig. 8) allowed to highlight which
the dynamics of the grounds is more significant in wet periods
than in periods sèches [15]. The presence and the action of the
water o f t he rain s c onstitute o nly one of the cau ses of the
release and the acceleration of the landslides.
Constantine city and l ocated in t he North-eastern area
Algerian, episodically knew sign ificant la ndslides ca using o f
significant human damage and materials (see fig. 7).
-10.0m
Dates
-20.0m
5/2003
7/2003
9/2003
-30.0m
11/2003
01/2004
03/2004
-40.0m
05/2004
07/2004
09/2004
11/2004
-50.0m
01/2005
-60.0m
-70.0m
Fig. 8.Inclinometric test results town of Constantine
[4]
Fig. 7. Slip of the barrier of security of a Constantine road
IV. CONCLUSION
[5]
The w ork c ompleted i n north eastern of Constantine showed
that th is zo ne is into p erpetual movement in wet season
confirmed with m easurements of m onitoring (inclinometric
piezometric géod ésiques).the microtectonic sup ported
instability by a n etwork of active faults. The stu dies
geotechnics of all the area appreciably gave the s ame results;
the argil laceous grounds o f miopliocene are particularly of
average with high plasticity.
Some cases of subjects of slips were so lved by systems of
supporting on the other hand for the slips
of broad wide any solution is not pos sible, a zoning of
prohibition to build was installed.
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
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[2]
[3]
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