D. ANINOIU, V. A. CODREA, O. BARBU - STUDY OF LANDSLIDES IN PINOASA COAL OPEN-PIT (OLTENIA, GORJ...

Studii şi cercetări, Geology-Geography 18, Bistriţa, p. 37-45 37

STUDY OF LANDSLIDES IN PINOASA COAL OPEN-PIT

(OLTENIA, GORJ COUNTY)

Daniel ANINOIU, Vlad A. CODREA

, Ovidiu BARBU

Abstract. In northern Oltenia – Gorj County – there are numerous landslides

originating both from natural causes, but also because of the lignite mining in open-pits.

Pinoasa open-pit is an illustrating case study, because of the large variety of landslide

types. This paper briefly describes some of the most representative landslides from the

area, trying to outline a typology based on the different control factors of landslides. In

future, the landslides occurred inside the coal mining areas from Oltenia – Pinoasa mining

area included - should be integrated in the national program of hazard maps. The relief

changes should be analyzed trough the IKONOS images. All landslides will be put under

monitoring trough topographic measurements. In Gorj department all landslides – natural

or human induced – will be mapped, these maps being useful in future for interventions in

case of emergencies.

Key words: coal mining, open-pits, landslides, Oltenia, southwestern Romania.

INTRODUCTION

Landslides are complex geodynamic processes, sometimes repetitive, with slow

addition of all factors that are controlling their activation. Landslides are in fact

nothing else but the natural tendency to re-establish the natural balance of the

slopes. The landslide can happen sometimes very fast.

The landslides can be activate either by natural, or human induced causes. The

natural ones are: physical and chemical features of the rocks related to genesis,

mineralogy, structure, degree of compaction, stratification and rock cracks,

humidity, cohesion, internal friction, porosity and permeability; gravitation;

physical and chemical water actions; influence of temperature; slope inclination

and structure; influence of plants; earthquakes. The human actions refer to: broken

of the natural talus balance due to mining works carried on its basement; vibrations

induced by heavy gears (excavators, trucks etc.); pressure of some constructions;

talus angle different by the natural one; deforestations; accumulation of water as

ponds inside the open-pits; changes of the river courses etc. Pleistocene or

Holocene landslides can sometimes be recorded, but there are even older too

(Florea, 1979).

Babeş-Bolyai University of Cluj-Napoca, Faculty of Biology and Geology, 1

Kogălniceanu Str., 400084 Cluj-Napoca, Romania.

Corresponding author: e-mail: [email protected]

mailto:[email protected]

38 Daniel ANINOIU, Vlad A. CODREA, Ovidiu BARBU

In Romania, landslides are often recorded in several regions. Oltenia is among

the ones where such processes are common, mainly in the Getic Depression, this

area belonging from geological viewpoint to the Southern Carpathian Foredeep

(Săndulescu, 1984). Only in Gorj County there are reported 51 localities and 98

areas with landslides. In northern Oltenia, Pliocene coal is mined since over a half

of century. Therefore, there are numerous coal open-pits and former underground

mines (Petrescu et al., 1987) where Pliocene lignite was and still is mined. In the

still working open-pits, landslides often occur, as consequence of the huge

excavations. Pinoasa coal open-pit is among these ones.

GEOLOGICAL AND GEOGRAPHICAL SETTINGS

Pinoasa coal open-pit is located inside the area comprised between Jiu and Jilt

rivers, southwest to Tg. Jiu town (Fig. 1). From geomorphologic viewpoint this

area is very fragmented, as consequences of the specific Late Pliocene (i.e.

Romanian) lithology dominate by sandy rocks, as well as because of the peculiar

tectonics.

The upper parts of the slopes, ranging between +350 and +230 m. in altitude, are

exposing old landslides that in the last decades were reactivated for the most part

by the excavations carried on for coal mining on the open-pit benches (as on

Boncea and Roşiei valleys; Fig. 8). A special location is the Neagomir sterile

dump, which was erected on Neagomir Valley, following the natural pitching.

There, landslides occurred rather often.

Pinoasa open-pit is crossed from east to west by five main faults that are

dividing this coal area in several distinct blocks. The first fault is named Arderea,

which can be observed along Pinoasa Valley, following the axe of the Runcurel-

Pinoasa-Rovinari anticline. The vertical gap between the blocks due to this fault is

reaching between 5-6 m toward west rising until 15 m to east. The second fault is

Beterga, following same trending, but leading to lower gaps, 2-4 m only. In the

central part of the coal mining area, this fault is divided into two branches. The

Valea Roşiei Fault is trended east-west, with gaps comprised between 8-10 m.

Boncea Fault, located in the southern part of the area is an important one, with

rather constant 5-6 m gap. The last main fault is Timişeni, in the south part of the

area, with 3-7 m gap. Apart these main faults, there are also several smaller ones

that control the talus sliding.

Study of Landslides in Pinoasa Coal Open-Pit

(Oltenia, Gorj County) 39

Fig. 1. Location of the coal mining areas near Tg. Jiu

and of Pinoasa coal open pit

GEOLOGICAL CONTROL OF THE LANDSLIDES

The Pliocene-Quaternary deposits from the studied region are exposing also old

landslides that became obvious as the excavations for the coal progressed. The

clay/sand interbeddings, their stratification, faults, fissures, all favor the landslides

(Aninoiu, 2004).

The lithology of the Late Pliocene (Romanian) deposits, as well as the relief

evolution in Quaternary led to old landslides that can be recorded between the

altitudes already mentioned (Nistor, 2008). In same conditions occurred landslides

in the neighborhood coal mining areas (North Jilţ and South Jilţ open pits). Until

now, there are no correlations between Rovinari and Jilţ coal mining areas

concerning these old landslides.

In many cases, the landslides can damage roads, railways, settlements or fertile

areas that cannot be retrieved for agriculture (Fodor & Baican, 2001).


Fig. 2. Talus tumbling-down, h=40m

A. Landslide in Neagomir sterile dump area

In the upper section of the landslide there is a vertical tumbling-down on 40 m

(Fig. 2). To the base, the appearance is the one of a classical consequent landslide.

It should be mentioned that landslides occurred 30-40 years ago, if considering the

age of trees (Figs. 5-6). We may also consider that the water infillings originating

from Neagomir sterile dump played a main role in initiating the landslide. The

slope angle exceeded 30°. The detachment line has 350 m in length, following

Scoarţei Valley. The landslide completely changed the local relief, mainly the

slope, with damages: a lot of waste forest, two large water tanks that were damaged

in Neagomir area falling down, as well as the road that once was at the base of the

slope.

B. The landslide occurred in the area of the Pinoasa open-pit benches

In Pinoasa open-pit area, along the creeks and rivers that are crossing the mining

zone from west to east, there are several old landslides that dislodged the coal

seams X, XI and XII (Figs. 4, 7, 10).

In 2008 a high amplitude slope landslide occurred. On a distance of 450 m, ca.

65,000 t of lignite originating from the upper coal seams fell down, all this coal

being lost (Rotescu & Aninoiu, 2007). Together with this coal, an important part of

the private forest from the neighbourhood was also destroyed (Figs. 5, 6, 8, 11, 12).

The conveyer-belt T27 as well as the rubber mat were pushed away from their

primary position (Fig. 3).



Fig. 3. Talus landslide that pushed away the coal conveyor belt

Fig. 4. Lignite lost in Pinoasa open-pit

Fig. 5. Landslide damaging an oak forest


Fig. 6. Forest damaged by landslide on Neagomir sterile dump

Fig. 7. Talus landslide at Pinoasa coal-open pit

Fig. 8. Landslide moving down slope several trees at Valea Scoarţei



Fig. 9. Old landslide on Boncea Valley

Fig. 10. Old landslide reactivated by the coal mining works

Fig. 11. Talus landslide at Pinoasa I

Fig. 12. “Drunken forest”


Following Grigore & Achim’s (2003) landslides classification, the ones from

Pinoasa open-pit may be ranged as follow:

According to the specific Late Pliocene-Quaternary geological factors: i.

consequent landslides (in obvious dominance); ii. non-sequent landslides initiated

by landfall followed by slump (e.g. Neagomir sterile dump);

According to the dominant lithology: i. plastic-suffosional landslides;

According to the high thickness of the geological deposits involved in

landslide: i. deep landslides;

According to structure: i. landslides on monocline structure;

According to the morphology of landslides: i. step-up landslides; ii. mound-like

landslides; iii. waved landslides;

According to the age of the landslides: i. very old landslides (Late Pliocene-

Pleistocene); ii. old landslides – until 30 years; iii. recent landslides – between

actual and 15 years ago; iv. actual landslides – already activated or in course to be

activate now; v. potential future landslides; vi. new, old or very old landslides

reactivated.

CONCLUSIONS

Inside Pinoasa coal field, on ca. 15 km² a large variety of landslides can be

observed.

In this area, due to the alternating lithology (clay vs. sand), the landslides

occurred very long time ago, since the Late Pliocene (Middle and Late Romanian),

continuing in Pleistocene and Holocene. These old landslides were observed in

proportion as the excavations for coal progressed westward.

The recent landslides were observed, estimated and mapped easily due to their

obvious visible effects: changes of the local relief, age of trees from cornice and the

landslide mass. The recent landslides were brutal and deeply changed the western

slope of the Neagomir sterile dump. They caused considerable damages, destroying

two water tanks at Neagomir (each one on 10 m diameter) as well as ca. 8 ha of

forest. The former road linking Pinoasa open-pit to the outer Neagomir sterile

dump was damaged, being impassable for more than five years. In Pinoasa open-pit

the landslide damaged a coal conveyer belt on 450 m length. Over than 65,000 t of

lignite were lost.

In the future, the landslides occurred inside the coal mining areas from Oltenia

should be integrated in the national program of hazard maps. The relief changes

should be analyzed by the IKONOS images. All landslides will be put under

monitoring by topographic measurements. In Gorj County all landslides – natural

or human induced – will be mapped, these maps being useful in future for

interventions in case of emergencies.



Rezumat. Studiul alunecărilor de teren din aria carierei de cărbuni Pinoasa (jud.

Gorj). În nordul Olteniei – jud. Gorj – sunt consemnate numeroase alunecări de teren,

generate atât de cauze naturale, cât îndeosebi de exploatarea lignitului în cariere la zi.

Cariera Pinoasa este un elocvent studiu de caz prin varietatea remarcabilă a alunecărilor de

teren. În acest articol sunt succint descrise câteva dintre cele mai reprezentative alunecări

de teren din zonă, încercându-se şi o încadrare tipologică în funcţie de diferiţii factori de

control care le declanşează. În viitor, alunecările de teren care apar în câmpurile miniere de

exploatare a cărbunilor din Oltenia – inclusiv cariera Pinoasa – trebuie integrate în cadrul

programelor naţionale de cartare a zonelor de risc. Modificările de relief trebuie analizate

prin intermediul imaginilor IKONOS. Toate alunecările de teren trebuie permanent

monitorizate prin măsurători topografice. În judeţul Gorj alunecările de teren – naturale sau

având cauzalitate antropică – vor fi cartate, hărţile rezultate constituind o bază utilă pentru

intervenţiile în cazuri de urgenţă.

Cuvinte-cheie: exploatări de cărbuni, cariere la zi, alunecări de teren, Oltenia, sud-

vestul României.

REFERENCES:

ANINOIU, D., 2004, Geologia structurală a depozitelor pliocen- cuaternare din bazinul

minier Rovinari, Ed. Academică Brâncuşi: 137 pp.

FLOREA, M., N., 1979, Alunecările de teren şi taluze, Ed. Tehnică: 301 pp.

FODOR, D., BAICAN, G., 2001, Impactul industriei miniere asupra mediului, Ed.

Infomin: 392 pp.

GRIGORE, M., ACHIM, F., 2003, Iniţiere şi date generale privind alunecările de teren şi

unele elemente specifice ale acestora pe teritoriul României, Ed. Universitară: 141 pp.

NISTOR, C., 2008, Impactul carierei Roşia de Jiu asupra dinamicii locale a reliefului,

Revista Minelor, 1, (199): 21- 26.

PETRESCU, I., MĂRGĂRIT, Gh., NICORICI, E., NICORICI, M., BIŢOIANU C.,

DUŞA, A., ŢICLEANU, N., PĂTRUŢOIU, I., TODROS, C., MUNTEANU, A.,

IONESCU, M., BUDA, A., 1987: Geologia zăcămintelor de cărbuni, vol. 2, Ed.

Tehnică: 386 pp.

ROTESCU, C., ANINOIU, D., 2007, Consideraţii asupra gradului de recuperare a rezervei

geologice de lignit în zona anticlinalului Runcurel-Rovinari jud. Gorj, Revista Minelor,

1, (187): 9- 11.

SĂNDULESCU, M., 1984, Geotectonica României. Ed. Tehnică: 336 pp.

Received: 22 January 2013

Accepted: 17 February 2013

D. ANINOIU, V. A. CODREA, O. BARBU - STUDY OF LANDSLIDES IN PINOASA COAL OPEN-PIT (OLTENIA, GORJ...

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