*2.2.1 Qualitative risk assessment*

The level of risk as a product between the severity level (consequence) and the probability level of the analysed event is calculated [14].

Using the information obtained from the analysis, the risk of an event is placed in a matrix (**Figure 2**).

The extent of the risk analysis and the intensity of the prevention and mitigation measures should be proportional to the risk involved. Simple models of hazard identification and qualitative risk analysis are not always enough and therefore it is necessary to use detailed assessments. There are several methods for performing quantitative risk assessment [15]. The choice of a particular technique is particular to the analysed accident scenario.

Those accident scenarios are analyzed more thoroughly which, as a result of the qualitative analysis, are considered as potentially major, probabilities over 10<sup>6</sup> , i.e., they can occur earlier than 10,000 years and major consequences, so high risk above level 15.


#### **Table 3.**

**2.1 Qualitative analysis of the consequences**

**Hazop technique Hazan technique** Identify hazards Assess hazards

Qualitative Quantitative

Made by a team Made by one or two experts

Preferred technique for use in

*Risk Management and Assessment*

*Difference between Hazop and Hazan.*

**Crt. No. Level Effects**

every project

**Table 1.**

Also called "But If?"

levels have the following significance (**Table 2**):

1 Insignificant **Population:** insignificant injuries

community 2 Minor **Population:** insignificant injuries

community

4 Major **Population:** serious injuries

5 Catastrophic **Population:** death

**Table 2.** *Risk severity level.*

**16**

3 Moderate **Population:** medical treatments are required

It is achieved through the classification into five levels of severity, an internationally accepted methodology and used in risk assessment studies [2, 13]. The five

the ecosystem, on short term and reversible

the ecosystem, on short term and reversible

**Economic:** reduction of production capacity

**Economic:** interrupting the production activity **Emissions:** off-site emissions without harmful effects

**Economic:** stopping the production activity

extended areas of the soil

soil which can be remedied quickly

**Ecosystems:** some minor adverse effects on few species or parts of

**Ecosystems:** some minor adverse effects on few species or parts of

**Socio-political:** insignificant social effects without any concern for the

**Emissions:** emissions within the target area withheld with external assistance **Ecosystems:** temporary and reversible damage, damage to habitats and migration of animal populations, plants unable to survive, air quality affected by compounds with potential long-term health risk, possible damage to aquatic life, pollution requiring physical treatments, limited contamination of

**Socio-political:** social effects with moderate concerns for the community

**Ecosystems:** death of animals, large-scale damage, damage to local species and destruction of large habitats, air quality requires "safe shelter" or decision to evacuate, soil remediation is possible only through long-term programs **Socio-political:** social effects with serious concerns for the community

**Socio-political:** social effects with very high concerns for the community

**Emissions:** toxic emissions outside the site with harmful effects **Ecosystems:** death of animals in large numbers, destruction of species of flora, air quality requires evacuation, permanent contamination and on

**Socio-political:** insignificant social effects without any concern for the

exposed to major accidents

Selective technique: it is used especially for systems potentially

*Levels of the probability of producing risks.*


#### **Figure 2.**

*The matrix of qualitative risk assessment and risk levels.*

Methods are used to estimate the accidental emissions in the atmosphere and models of simulation of the dispersion based on which the severity of the possible consequences is evaluated.

• The preparatory phase, of slow, incipient slip (preliminary processes).

From the geotechnical studies and the physico-mechanical characteristics of the boulders and the base terrain, they concluded that the risk of landslides may occur in areas where the slope angle exceeds the internal friction angle of the boulders and on or through the land base if its inclination is greater than the interior rubbing

As a result of the sliding large areas of agricultural land have suffered, constructions of villages or cities, roads, railways etc. are damaged, damage to industrial premises or to the area of hydrotechnical works are made. The masses of ground that can be moved can penetrate the banks of the rivers, causing the bottom to be

The rocks that favor the sliding production the most are the "sensitive clays," spread in the regions that were covered with glaciers in the quaternary. They favor the movement of materials even on slopes of only 2–3°. That is why in the Northern countries of Europe, Alaska and so on, the landslides are frequent and large.

The most common landslides are recorded on slopes with moderate inclinations

In Romania, this type of process affected at the level of 1975 over 800,000 ha, some of which at about 250,000 ha with active landslides and 550,000 ha with stabilized landslides [16]. However, these expanded in the following years, espe-

The studies for the prevention of landslides and the fight against their negative

a. Recognition of the areas affected by landslides and those susceptible to

d. Establishing the causes and mechanisms of movement in different types of

(a) *The recognition of the areas affected by landslides and those susceptible to landslides* is facilitated by the observation of the specific micro-relief, by the mosaic

f. Knowledge of the way of intervention and of the technical works for

b. Establishing the types, respectively the classification of the sliding.

e. The mechanisms of movement in different types of rocks.

(10–30°) consisting of rocks with high shale, intensely fractured and altered.

cially until 1982. The landslides take large areas of slopes within the Sub-Carpathians (especially the curvature sector, where on certain areas they affect almost entirely the slopes), the Plateau of Moldova, the Transylvanian Depression, the Getic Plateau and even in the mountainous area (in the east of the Eastern Carpathians, in the sectors with high weight of clay shale, where the oil exploitation contributes to the disturbance of the slope balance by drilling, spills, vibrations. Example: the sliding in Zemes in 1992 moved out of work 47 oil wells, pipes,

electrical networks, dwellings, the school).

consequences aim at the following stages:

c. Establishing the evolution stage.

stabilizing the lands.

landslides.

rocks.

**19**

• The actual slip (crossing the geomorphological threshold).

• Natural stabilization (balancing, post-processing processes).

raised or the partial or total obstruction of the drainage section.

angle of the rocks.

*Risk of Slipping Industrial Landfills*

*DOI: http://dx.doi.org/10.5772/intechopen.91020*

Specific simulation methods are applied to assess the consequences of possible explosions or fires. The results of some simulation studies of the formation of breaches in the body of the tailings dam and the acid water collection pond are used to assess the consequences of such events.

The frequency diagram—consequences, FN (loss of materials or number of fatalities) centralizes the result of the analyses carried out in this way and it graphically presents the social risk specific to the project in correlation with the socially acceptable level of risk.

An overall assessment of the risk associated with the sliding of industrial waste will be made using the methodology of rapid environmental and health risk assessment developed by the World Health Organization.

#### **3. Sliding of waste sterile dumps**

The loss of the stability of the waste sterile dumps is determined by the following factors:


The probability of production is average, considering the compliance with the technical design criteria for the stability of the dumps, established for the specific conditions of the site and the characteristics of the material ([7], pp. 12–13).

The dumps will be monitored continuously, through visual control, through manual and automated topographic measurements, and the tailing will be carried out in stages, with the flatting and compaction of the deposited material. The severity of the accident can be major due to the large amounts of waste resulting from and deposited on the dumps and the fact that the sliding may cause damage to buildings on the site or access roads.

Waste dumps sliding after the completion of the deposits and carrying out the rehabilitation works have low probability and moderate severity, the associated risk being much lower than in the operating phase.

Geotechnical field investigations and studies of the physico-mechanical characteristics of the boulders and of the basic land have led to the conclusion that landslides can occur through boreholes. The risk of sliding slopes occurs in areas where the slope angle exceeds the interior friction angle of the welded rocks and on or through the base terrain if its slope is greater than the interior friction angle of the rocks.

The landslides of the industrial tailings deposits are a category of natural risk phenomena, which define the process of movement, the actual movement of the rocks or deposits on the slopes, as well as the resulting form of relief.

This slip process has three phases:

Methods are used to estimate the accidental emissions in the atmosphere and models of simulation of the dispersion based on which the severity of the possible

Specific simulation methods are applied to assess the consequences of possible explosions or fires. The results of some simulation studies of the formation of breaches in the body of the tailings dam and the acid water collection pond are used

The frequency diagram—consequences, FN (loss of materials or number of fatalities) centralizes the result of the analyses carried out in this way and it graphically presents the social risk specific to the project in correlation with the socially

An overall assessment of the risk associated with the sliding of industrial waste will be made using the methodology of rapid environmental and health risk assess-

The loss of the stability of the waste sterile dumps is determined by the

• The configuration and the physical-mechanical characteristics of the

• The hydrodynamic particularities of the waters in the area and their

• The geotechnical characteristics of the waste sterile material (porosity, internal friction angle, cohesion, cracking specifies, humidity, degree of

The probability of production is average, considering the compliance with the technical design criteria for the stability of the dumps, established for the specific conditions of the site and the characteristics of the material ([7], pp. 12–13). The dumps will be monitored continuously, through visual control, through manual and automated topographic measurements, and the tailing will be carried out in stages, with the flatting and compaction of the deposited material. The severity of the accident can be major due to the large amounts of waste resulting from and deposited on the dumps and the fact that the sliding may cause damage to

Waste dumps sliding after the completion of the deposits and carrying out the rehabilitation works have low probability and moderate severity, the associated risk

Geotechnical field investigations and studies of the physico-mechanical charac-

The landslides of the industrial tailings deposits are a category of natural risk phenomena, which define the process of movement, the actual movement of the

teristics of the boulders and of the basic land have led to the conclusion that landslides can occur through boreholes. The risk of sliding slopes occurs in areas where the slope angle exceeds the interior friction angle of the welded rocks and on or through the base terrain if its slope is greater than the interior friction angle of

rocks or deposits on the slopes, as well as the resulting form of relief.

consequences is evaluated.

*Risk Management and Assessment*

acceptable level of risk.

following factors:

founding ground.

compaction, etc.).

buildings on the site or access roads.

the rocks.

**18**

being much lower than in the operating phase.

This slip process has three phases:

to assess the consequences of such events.

**3. Sliding of waste sterile dumps**

ment developed by the World Health Organization.

interaction with the material from the dump.


From the geotechnical studies and the physico-mechanical characteristics of the boulders and the base terrain, they concluded that the risk of landslides may occur in areas where the slope angle exceeds the internal friction angle of the boulders and on or through the land base if its inclination is greater than the interior rubbing angle of the rocks.

As a result of the sliding large areas of agricultural land have suffered, constructions of villages or cities, roads, railways etc. are damaged, damage to industrial premises or to the area of hydrotechnical works are made. The masses of ground that can be moved can penetrate the banks of the rivers, causing the bottom to be raised or the partial or total obstruction of the drainage section.

The rocks that favor the sliding production the most are the "sensitive clays," spread in the regions that were covered with glaciers in the quaternary. They favor the movement of materials even on slopes of only 2–3°. That is why in the Northern countries of Europe, Alaska and so on, the landslides are frequent and large.

The most common landslides are recorded on slopes with moderate inclinations (10–30°) consisting of rocks with high shale, intensely fractured and altered.

In Romania, this type of process affected at the level of 1975 over 800,000 ha, some of which at about 250,000 ha with active landslides and 550,000 ha with stabilized landslides [16]. However, these expanded in the following years, especially until 1982. The landslides take large areas of slopes within the Sub-Carpathians (especially the curvature sector, where on certain areas they affect almost entirely the slopes), the Plateau of Moldova, the Transylvanian Depression, the Getic Plateau and even in the mountainous area (in the east of the Eastern Carpathians, in the sectors with high weight of clay shale, where the oil exploitation contributes to the disturbance of the slope balance by drilling, spills, vibrations. Example: the sliding in Zemes in 1992 moved out of work 47 oil wells, pipes, electrical networks, dwellings, the school).

The studies for the prevention of landslides and the fight against their negative consequences aim at the following stages:


(a) *The recognition of the areas affected by landslides and those susceptible to landslides* is facilitated by the observation of the specific micro-relief, by the mosaic

appearance of the soils (unevolved soils) as well as by the presence of certain plant associations that indicate the varied ecological conditions determined by the newly formed soils.

mining targets. Most are found in Suceava (224), Maramureş (180), Caraş-Severin (78) and Alba (66) counties. The problem is that only 247 of the 1101 dumps are owned by companies, the rest reaching over the years in the custody of local

Regarding the decanting ponds, there are 108, only 15 of which are operational. Most are in the counties of Maramures (15), Hunedoara (13), Harghita and Caraş-Severin (10). Many of them present a risk of sliding, especially in the seasons with heavy rainfall. Safety and environmental works have been started in many decanting ponds, but over time they have been interrupted even for years. On the other hand, where the greening was done many years ago, and the land was subsequently relocated, no monitoring was done, so no one knows what the current situation is. Within the 556 mining objectives approved for closure since 1998, there are 78 decanting ponds with a total stored volume of 341.31 million m<sup>3</sup> and an area of approximately of 1770 ha, as well as 675 mining waste dumps, with a volume of

In Romania, one of the worst events of this type occurred in October 1971, when the tailings dam on the outskirts of Certejul de Sus, Hunedoara County broke down and the avalanche of toxic sludge killed 89 people and injured almost 100 others, most of the victims being children. The victims were buried in the waste of decanting ponds after the dam was broken or crushed by the debris of the blocks taken by the toxic avalanche. Over the 300,000 cubic meters of tailings lapped everything in their path, in only a quarter of hour. The wave of toxic sludge covered and destroyed six blocks, a home for single people and over 50 households. Almost half of the 89 victims killed by the disaster were students and preschoolers, and

(c) *Establishing the evolution stage* leads to the differentiation of the active sliding (characterised by the fact that the process of moving the materials on the slopes is in progress), semi-stabilized sliding (characterised by an obvious reactivation potential) and stabilized sliding (old sliding, which does not present conditions for the

(d) *Establishing the causes and mechanisms of movement in different types of rocks*. Within the natural causes which have already been mentioned, the strength characteristics of the rocks, represented by the angle of internal friction and cohesion, are of the utmost importance in the study of the dynamics of landslides. These can

τ ¼ ð Þ σ � u tgφ þ c (2)

; u = pore water pressure; φ = internal shear angle,

; σ = normal pres-

3101.92 million m3 and an area occupied by about 9260 ha [16].

almost a quarter of them were women [16].

be determined with the Coulomb-Terzaghi equation:

in which τ = shear strength (tangential shear stress), daN/cm<sup>2</sup>

.

the displacement forces or due to the decrease of the resistance forces.

may retain its original structure or may be completely destroyed.

The water pressure in the pore (u) is determined by the formula u = γaha, in which γ<sup>a</sup> is the specific weight of the water, and ha, the equipotential height taken

(f) *Knowledge of the way of intervention and of the technical works for stabilizing the lands*, it is known that the stability of a slope is conditioned by the existence of a balance between the forces of movement (represented by the multiplication between the mass of the material and the gravitational acceleration) and those that are opposed to the movement (the shear strength of the rocks that make up that slope). Therefore, the triggering of a sliding will start either due to the increase of

The movement can occur by translation or rotation, and the displaced material

movement retake).

in point a.

**21**

sure on the shear plane, daN/cm<sup>2</sup>

degrees; and c = cohesion, daN/cm<sup>2</sup>

administrations.

*Risk of Slipping Industrial Landfills*

*DOI: http://dx.doi.org/10.5772/intechopen.91020*

The profile of the slopes has an irregular appearance, the surface deposits are kneaded in the form of sliding steps, mounds, waves, furrows, cracks, ridges, micro-depressions often occupied by water mesh or hygrophilous vegetation.

The main elements of a landslide are:


(b) *Establishing the types, respectively the classification of the landslides* is made on the basis of several criteria: the geological structure of the slope, the way of affecting the slope, the characteristic morphology, the production time and so on. The most frequent and at the same time the most important through their consequences are the complex slidings, the interventions for their stabilization being very expensive. They are deep landslides, with generally old floods, with thicknesses exceeding 5 m, moving slowly on slopes, generalized on important areas of slopes.

The classification according to the depth to which the deposits are disturbed is very important, from this point of view there are three important categories:


The most dangerous are those which are deep, violent and rapid (with speeds of 2–3 m per hour), with disastrous consequences when they occur in inhabited areas: cracks in the soil, mounds, slope breaks, ditches, overturned vegetation, destruction of dwellings, roads and other economic objectives, etc.

A category of catastrophic landslides is represented by the sliding-crumbling, characteristic of the areas consisting of alternations of plastic rocks (clays or marls) and relatively hard rocks (hone) and even uncemented (sand, gravel). They are the result of the erosion affecting the base of the slopes, causing the breakage and collapse of the masses without support, together with their lateral pushing on those on the intensely moistened sliding bed. Moreover, the cutting of the slopes and excavations can lead to the triggering of such sliding, thus it is necessary to take into account the limit value of the slopes in relation to the type of rock.

According to a report of the inter-ministerial commission [16] for the inventory of industrial dumps, in Romania there are 1101 waste dumps, 994 of which are

#### *Risk of Slipping Industrial Landfills DOI: http://dx.doi.org/10.5772/intechopen.91020*

appearance of the soils (unevolved soils) as well as by the presence of certain plant associations that indicate the varied ecological conditions determined by the newly

The profile of the slopes has an irregular appearance, the surface deposits are kneaded in the form of sliding steps, mounds, waves, furrows, cracks, ridges, micro-depressions often occupied by water mesh or hygrophilous vegetation.

• The sliding slope or the detachment shaft, which is the area where the sliding

• The body or mass of the sliding, which comprises the part of the displaced terrain, corresponding to the sector with chaotic micro relief, unfolded

• The front of the sliding, corresponding to the terminal part of the slide.

moving slowly on slopes, generalized on important areas of slopes.

• *Medium depth sliding*, with thicknesses between 2 and 5 m.

but which acquire a special magnitude where they occur.

account the limit value of the slopes in relation to the type of rock.

of dwellings, roads and other economic objectives, etc.

**20**

• The bed, the mirror or the sliding surface, representing the lubricated substrate, more or less smooth, on which the mass of material is moved down the slope.

(b) *Establishing the types, respectively the classification of the landslides* is made on the basis of several criteria: the geological structure of the slope, the way of affecting the slope, the characteristic morphology, the production time and so on. The most frequent and at the same time the most important through their consequences are the complex slidings, the interventions for their stabilization being very expensive. They are deep landslides, with generally old floods, with thicknesses exceeding 5 m,

The classification according to the depth to which the deposits are disturbed is

• *Surface sliding*, up to 2 m thick, with the highest frequency and which usually represent reactivations of the old surfaces with sliding, but are also present on the slopes that have undergone a single cycle of mass movement processes.

• *Deep sliding*, with thicknesses exceeding 5 m, with a slightly lower frequency,

The most dangerous are those which are deep, violent and rapid (with speeds of 2–3 m per hour), with disastrous consequences when they occur in inhabited areas: cracks in the soil, mounds, slope breaks, ditches, overturned vegetation, destruction

A category of catastrophic landslides is represented by the sliding-crumbling, characteristic of the areas consisting of alternations of plastic rocks (clays or marls) and relatively hard rocks (hone) and even uncemented (sand, gravel). They are the result of the erosion affecting the base of the slopes, causing the breakage and collapse of the masses without support, together with their lateral pushing on those on the intensely moistened sliding bed. Moreover, the cutting of the slopes and excavations can lead to the triggering of such sliding, thus it is necessary to take into

According to a report of the inter-ministerial commission [16] for the inventory

of industrial dumps, in Romania there are 1101 waste dumps, 994 of which are

very important, from this point of view there are three important categories:

formed soils.

The main elements of a landslide are:

downstream by the detachment shaft.

material mass breaks.

*Risk Management and Assessment*

mining targets. Most are found in Suceava (224), Maramureş (180), Caraş-Severin (78) and Alba (66) counties. The problem is that only 247 of the 1101 dumps are owned by companies, the rest reaching over the years in the custody of local administrations.

Regarding the decanting ponds, there are 108, only 15 of which are operational. Most are in the counties of Maramures (15), Hunedoara (13), Harghita and Caraş-Severin (10). Many of them present a risk of sliding, especially in the seasons with heavy rainfall. Safety and environmental works have been started in many decanting ponds, but over time they have been interrupted even for years. On the other hand, where the greening was done many years ago, and the land was subsequently relocated, no monitoring was done, so no one knows what the current situation is.

Within the 556 mining objectives approved for closure since 1998, there are 78 decanting ponds with a total stored volume of 341.31 million m<sup>3</sup> and an area of approximately of 1770 ha, as well as 675 mining waste dumps, with a volume of 3101.92 million m3 and an area occupied by about 9260 ha [16].

In Romania, one of the worst events of this type occurred in October 1971, when the tailings dam on the outskirts of Certejul de Sus, Hunedoara County broke down and the avalanche of toxic sludge killed 89 people and injured almost 100 others, most of the victims being children. The victims were buried in the waste of decanting ponds after the dam was broken or crushed by the debris of the blocks taken by the toxic avalanche. Over the 300,000 cubic meters of tailings lapped everything in their path, in only a quarter of hour. The wave of toxic sludge covered and destroyed six blocks, a home for single people and over 50 households. Almost half of the 89 victims killed by the disaster were students and preschoolers, and almost a quarter of them were women [16].

(c) *Establishing the evolution stage* leads to the differentiation of the active sliding (characterised by the fact that the process of moving the materials on the slopes is in progress), semi-stabilized sliding (characterised by an obvious reactivation potential) and stabilized sliding (old sliding, which does not present conditions for the movement retake).

(d) *Establishing the causes and mechanisms of movement in different types of rocks*. Within the natural causes which have already been mentioned, the strength characteristics of the rocks, represented by the angle of internal friction and cohesion, are of the utmost importance in the study of the dynamics of landslides. These can be determined with the Coulomb-Terzaghi equation:

$$\boldsymbol{\pi} = (\boldsymbol{\sigma} - \mathbf{u})\,\mathsf{tg}\,\mathsf{p} + \mathsf{c} \tag{2}$$

in which τ = shear strength (tangential shear stress), daN/cm<sup>2</sup> ; σ = normal pressure on the shear plane, daN/cm<sup>2</sup> ; u = pore water pressure; φ = internal shear angle, degrees; and c = cohesion, daN/cm<sup>2</sup> .

The water pressure in the pore (u) is determined by the formula u = γaha, in which γ<sup>a</sup> is the specific weight of the water, and ha, the equipotential height taken in point a.

(f) *Knowledge of the way of intervention and of the technical works for stabilizing the lands*, it is known that the stability of a slope is conditioned by the existence of a balance between the forces of movement (represented by the multiplication between the mass of the material and the gravitational acceleration) and those that are opposed to the movement (the shear strength of the rocks that make up that slope). Therefore, the triggering of a sliding will start either due to the increase of the displacement forces or due to the decrease of the resistance forces.

The movement can occur by translation or rotation, and the displaced material may retain its original structure or may be completely destroyed.

#### *Risk Management and Assessment*

Along with the natural causes, human activity can contribute to the triggering of sliding with disastrous effects, through improper use of the lands and carrying out works and constructions that do not take into account the degree of stability of the slopes.
