The samples taken from the slopes of the masses on the results obtained from the geotechnical testing.
The stability analysis carried out by GEO5 software and uses free sliding analysis by wet and pore saturated weight charting provided the safety factor of 1.35. The safety precautions were followed by inclinometers and wire extensometer measurements. The other pore saturated asphalt bound shear box and unaxial test compression tests were resulted in the geotechnical and geoseismical data over sliding soil /shale inter surface quality and the characteristics of free rock falling risk and discontinuity distribution, sub crack density and distribution on stereo nets were determined. The research was firstly followed the perched water levels on geoseismical data over causing water burst or explosion of highly free mud and landslides. The hazardous rock falls over saturated soil and uncohesive rock explosions. The proposed study was secondly as strengthening methods such as asphalt mixing as precautious on shear stabilization and other wire mesh barriers anchored. The free sliding cracks was filled by asphalt and compressed for stabilization strengthening known as the characteristics of avoiding shear falls in the future. The unconditional expectations related to this study was also defined for this region such as the influence of the ground water, rock cracks and slope design, explosion exchange dynamics leading to landslide.
- mining pit
- Şırnak asphaltite
- free slide
- geoseismical analysis
- shale stability
- slope stability
Open pit mine slope stability and the rock fall risk assessment were studied in high steep excavation site in order to avoid landslides or rock falls occurred several times in Avgamasya Asphaltite mining sites, Şırnak. The high steep slopes were reaching over 120 m high with partly 60–65 degree shale/soil slopes developing major free landslide hazard in harsh climate conditions in recent years. The coal seam was so vertical diving at the working area of miners, made compulsory to pre-search and take precautions by a hot melted asphalt/fly ash mixture filling through tension cracks over rock falling and free sliding cavities in the hazardous mining operation area in the open pit asphaltite mining. The critical issues and precautions for free failure in Avagamasya Open Pit Site No 2 were mentioned as below:
Basic instability parameters searched by many researchers mentioned above anisotropy as often caused sudden failure by hazardous fractures and cracks in excavation and mining sites [1, 2, 3, 4, 5, 6, 7, 8, 9, 10].
Tensile cracks and shear loads that occurred in the free slip surfaces on heterogeneous breccias formations in Şırnak geology [11, 12] and cracks and land of asphaltite mining investigated by standards [13, 14, 15, 16].
Hazard risk can be examined as water income and levels in the mine [17, 18]. In the pit slopes, these values of pore pressure u are synchronized the stress and the ground water income patterns should be extracted [19, 20].
During the works, asphalt filling stabilization of cracks on the safety of the slopes [21, 22, 23, 24] and steps are formed in the work stages, the safety of the truck transportation road and the safety of the excavation area were ensured by anchorage reinforcement [25, 26, 27, 28, 29].
A steeper safe stepping of the slopes and a suitable minimum fly ash addition pouring and crack area of asphalt filling design has been developed lower horizontal adhesive stabilization and less cracks [30, 31, 32, 33, 34, 35, 36]. High compacting vibration, drainage and low excavation capacity were also affected excavation time, free slope, crack yields and steep displacements following discontinuous failures [37, 38].
Ideally, extensometer patterns and wire cables in the stereo net were explored awareness of slide by examining the fractures in the Avgamasya asphaltite mining area. Tele monitoring of boreholes and level mirrors was made daily. In addition, acoustic sound noise analysis was also carried out. Since drilling inspection holes and daily wire follow-up was costly, taking measurements with tension wire extensometers in bevel chucks showed more reliable horizontal deformation values. Accordingly, 45 and 50 degree angles of Şırnak asphaltite quarries were found to be reliable [28, 32]. Two different design models have been developed in order to obtain these stability values. According to these models, it is thought that the slopes may be exposed to planar and wedge type shifts and frees sliding over the slip planes depending on the fracture bedding and density (Figures 1 and 2).
The observation of different asphaltite qualities in the field and the diversity of production provide the identification of qualified coal seams needed. Depending on the strength and hardness properties of coal, it is more difficult to determine the chemical structure and strength of asphaltites and side rocks containing heterogeneous structures compared to many other types of coal. The strength and failure type of the country rock differ. The components that make up the coal differ depending on the distribution, orientation, amount and strength and hardness values of these components in the asphaltite sample. This situation is determined relatively within a homogeneous asphaltite matrix. More qualified asphaltite shows softer mechanical strength. Hard veins are also very important in the country rocks. Asphaltite quality and development can be determined underground by seismic reflection and resistivity measurements, depending on the density Figures 3 and 4.
Asphaltite and shale, marly shale, marly limestone and various marly formations that are the subject of this study can also be revealed. The Siirt Formation, which is outcropping in the west–east directions of Şırnak province, is important in bedding and forms important rock units in asphaltite bedding in terms of rock mechanics. This unit generally consists of marls containing clay and shale and clays with asphaltite. Sulphate-rich water resources are also located in these units consisting of claystone rocks. Due to its different mechanical strengths and densities, it helps to find underground bedding. In addition, it has been evaluated within the scope of this study since it creates various engineering data.
In operation, the drilling cores are subjected to mechanical tests on site and under laboratory conditions. The micro structural and mineralogical studies carried out. Compression tests were carried out on samples with relatively weak asphaltite and claystone levels and hard, higher strength asphaltite veins with diameters of 34 mm and 84 mm.
With the findings obtained, it was determined that asphaltites containing components with different strength and hardness properties show different fractures. It is aimed to determine the changes in different breaking stresses and strengths for each borehole and logs.
Possible bedding will be examined with seismic reflection method and exploration drillings will be opened at the location points displayed on the map below. Drilling exploration locations will be opened at 1000 m depth at the points shown on the map. Seismic reflection data describe possible asphaltite bedding as shown in the Figure 2.
1.1 Uniaxial compression strength tests
Uniaxial compression strength tests without environmental stress were carried out in the Şırnak University laboratory with a 2000 kN capacity hydraulic controlled test device. Axial and circumferential deformation gauges are placed at the levels of half of the sample lengths, as shown in the figure, so that their measurements are not affected by changes in the sample edges. The axial strain gauges were placed tightly on both sides of the specimens, mutually. Measuring range of axial deformation gauges on the sample is 50 mm for 84 mm diameter samples and 35 mm for 34 mm diameter samples as shown in Figures 5 and 6. The circumferential strain (rad) was calculated with the help of strain gauges connected to the chain wrapped around the sample. During the test (Figure 7), digital feedback was provided by circumferential strain and the control value used was set at 0.05 mm/min. The rock properties were defined.
2. Stability modeling and asphalt covering for free rock sliding control in Şırnak open pit coal mining
Water drained layered surfaces confirmed the geotechnical stability caused anisotrophical pore pressure developed and compression strength developed. The below equation showed the shear on fre slip surface with cohesive mater.
where the shear force and stress and nominal load and compression stress at angle was caused failure at weak layer shear in the slope.
Vertical unaxial strength and Horizontal strength of the specimens were changed.
GEO5 model weight slice chart construction carried out as given below serial equation sum:
slice load kN , slope angle, The slip surface stability analyzed as load chart sum. Safety factors over 1,35 and 1,5 was confirming the stability.
Regarding the crack distribution and density orientation and intersection with water perched tables shown (Figure 5) as shear risk factor
10 m length slice at discontinuity at angle of crack and density of % heteregenous distriburtion on slip surface as was calculated.
The studied stages were as below:
Slope Stability Chart modeling was managed as shown in Figure 3.
The Stability mechanism and control by asphalt crack filling and cable net pillar construction was avoiding pore pressure for each slice as given Eq. (5)
u deformation intrinsic friction resistance, F weight slice, a shear fracture inclination angle t time, μ crack mud viscosity i weight slice.
The safety factor in free sliding has been investigated by following the stress cracks by transforming the slope deformations based on the internal friction angle patterns. Fracture agglomeration and cohesion-free free fall displacements can be observed above 50 mm. In order to increase the viscosity in the cracks, the waste liquid polymer materials were poured into these gaps to provide stability. The joint density over slip surface for each slice was calculated by the Equations sequentially as below:
safety water saturated rock parameters regarding pore water content
Safety factor was calculated by perched water table and water saturation
2.1 Rock texture, mineralogy and petrographic characteristics
As seen in Figure 8, the samples subjected to the tests generally present a heterogeneous rock texture consisting of claystone levels and anhydrite veins and layers of different frequencies. The thickness and elongation of the calcite veins in the claystone levels range from mm to cm. Its mineralogical composition is generally composed of anhydrite and clay minerals. Typically, the clay content and anhydrite content are inversely proportional to the samples. In other words, samples with low clay content generally contain higher density calcite veins.
Changes in the microstructure and mineralogy of the clay matrix, which appeared homogenous macroscopically, were determined in the microscopic examination of the samples subjected to experiments. As seen in Figure 5, the brown, dark brown and black regions usually contain clay matrix and rarely scattered calcite lumps in it. The areas seen in more gray tones form fine-grained anhydrides dispersed in fine-grained clays and form calcite-rich clay matrix. The anhydrite content and distribution in the clay matrix varies in sections. Besides, different types of matrix can be found in the same example.
As a result of the experiments conducted under environmental stress conditions, it was determined that the highest strength values ϭ varied between 9 and 81 MPa depending on the mineralogical composition of the samples. Failures occurred along the clay matrix in samples with low uniaxial compressive strength values. The samples with high values ϭ are the samples containing more than 84% marl. The general images of these examples show a homogeneous structure. The uniaxial compressive strength values ϭ obtained were accepted as extreme values ϭ indicating the strength properties of marl veins and clay matrix. In cases where the clay content is more than 10%, the uniaxial compression strength decreases very little. The opposite situation develops when the clay content is less than 7–10%. In this case, uniaxial compressive strength increases significantly due to the relatively increasing marl veins.
After these results, the relations between mass distribution of clays and σc under uniaxial conditions are evaluated in Figure 9. The standard test results similar to the ϭ values were obtained in uniaxial compression strength were encountered. When the clay content is more than 7–10%, the σc values decrease with an almost constant orientation.
Thus, in conditions where the clay content is less than 7–10%, σc values τ show a significant increase with the decrease of the clay percentage. In view of these results, it is thought that the initial fractures were controlled by the mechanical properties of the claystone levels, as the claystone levels were weaker than the low calcite belt levels.
The presence of chlorite belts is shown in claystone matrices of different type belts and different anisotropic strength properties together in the same sample. In the slip area of Avgamasya Open Pit quarry No 2. shale face the sliding shale formations is shown in Figures 10 and 11.
3. Geotechnical studies
Stack weight in the slip area to determine the geotechnical stability in American Standards (ASTM and GEO5) based. In the area where the strengthening cabling of the masses and the presented soil rock interface of the phase content is given in Tables 1 and 2.
|Sample No||Asphalt Ash compost fill||Asphalt+Fine Shale compost fill||S1||S2||S3||S4|
|Lı(%)||11.8 Mpa ϭ||9.6 Mpa ϭ||26||15||28||17|
|Pı(%)||42 RQD||40 RQD||19||11||18||22|
|Ip (%)||46 RMR||44 RMR||10||9||8||12|
Kum ve çakıllı
|γk max g/cm3||1,68||1,93||2,05||1,90|
|Permeability (k) (cm/s)||5,63*10−4||6*10−4||3,0*10−4||5,62*10−4|
Slip face of shale and limestone rock pillar parameters are given in Table 3 below.
|Specification of rock fill||Asphalt Ash compost fill||Asphalt+Fine Shale compost fill|
|Natural unit weight, γn (kN/m3)||16||18|
|Saturated unit weight, γd (kN/m3)||16||18|
|Cohesion, c (kN/m2)||52||88|
|Intern. Friction Angle, ϕ (°)||30||34|
Free slide rock stability to assess the risk of slipping GEO5 program used and was advantageous. Rock stability GEO5 program provided safety analysis at 1.35 safety factor. Stability analysis of weight slices as wide 3 m blocks as possible cut into slices. On Slope S1 free slip surface formed like 2m mesh using GEO 5 FEM program by groundwater data section submerged discharge gave the critical red level slip surface effect and poor stability factor was practiced by lower mesh cross section [19, 20]. Using GEO5 on slip slice chart is advantageous at different slip surface pore pressure in program as in Figure 12, depending on the rock surface or planar wedge type drift is not formed in particular from 30 to 40 m length was determined.
Safety factor was in the ASTM standard as based GEO 5 rock stability safety factor of over 1.35. Using the parameters determined by model chart analysis of GEO 5, the appropriate support system for the long-term stability of the slopes was determined. Accordingly, it was decided to make asphalt cohesive support with fly ash material in front of the slope. Subsequently, 2 m long rock bolts were placed to provide short-term slope stability. After this stage, it was understood that a compost of asphalt-cover structure should be made on the crack section. The slope was required to ensure the long-term stability of the Asphaltite open pit quarry.
4. Slope analysis of S1 and S2 shale soil/rock face slopes
The stack S2 hillside after rains made the small size of the movements that have been identified in field studies. No. S2 to develop pile slope is covered with talus and 10 m mesh rock stability GEO5 programs were created problem due to heterogeneous structure and complexity with the program (Figure 3A). S2 The top of the stack and the maximum height difference between the heel point 45 m, the slope of the maximum height of 50 m, the slope of the surface tilt angle is 40°.
Regarding cohesive resistive parameters obtained from the asphalt composed rock formations made in c ‘= 1.9 kpa, φ ‘= 22°, γnat. = 1.97 = 2.27 g/cm3 g/cm3, and are used to γdry. According to γdry and γnat calculated separately on the potential slip surface deformation iso values seen in Figure 13.
S2 after water perched table on the slope of a deep instability, high shear force occurred. The instability was observed. Similarly the slope S3 indicates instability and displacement reached 30 m depth slip circular surface in Bishop Theory. (Figure 12)
In addition, 1 m wide and 10 m high pillar construction by cable cover by a safety factor values were above 1.5 (Figure 14)
When using a pillar to reduce instabilities under perched water tables in the slip deformation displacement was shown in Figure 8 and displacement m below the maximum possible shift of the substrate reached 9 m depth.
The rock and filled asphalt waste fly ash compost shear stability ranged from 10 to 13 kPa with 610 kPa reaching a possible shift in the base.
5. Results and discussions
Therefore, the existing design was updated in this way and the safety coefficient of the slopes was obtained over 1.5 when the asphalt cohesive support structure was filled with 2 m filling as seen in Figure 4. As a result, the long-term security conditions of the shale slopes could only be achieved with these suggested measurements. and pillar cabled support. Cracks occurring in the S1 S2 and S3 slope as seen in Figure 2 reflected the free sliding situation where the safety coefficient was below 1 for 2 m blocks. For the stabilization case where the safety coefficient was over 1.35, the slip surface water parameters of the rock material on the slip surface were determined by slice weight analysis. Since the proposed analysis method was available for anchorage rock slopes, GEO 5 was directly used in this study. Because it was clear that completely degraded shale forming a weak slope over asphalt filled stabilized rock mass or completely free slip ground. GEO 5 method was preferred as the most suitable method for characterization of the free stability of the slope. RocScience software was also using finite element mesh programs and the parameters at this case of complete failure were determined. GEO5 analyzes were performed using the slice method. In this method, the safety coefficient is obtained by decreasing the shear strength parameters of the material forming the slope. GEO5 program calculated the 1.35 safety coefficient using shear force and resistive load. The reduced resistive load reduction method produced slide on slice weight principles. On the effective pore pressure, the rock failure by shear performs on below Eq (23).
As a result of analysis, shear resistive work performed in the field of geotechnical stabilization, the future should be considered a danger to very large fills and the filling cracked field should be determined according to the method of stabilization. Also within the project study area will be opened due to urban use preventive methods to investigate the instability in the region and it is important to develop a separate.
The stability was increased by compost rock cracks filled with asphalt/fly ash density reducing the water sorption content of uniaxial test blocks for 25 volume % rock cavity by 85% asphalt and 15% fly ash filling as shown in Figure 15.
The uniaxial compression strength of shale was increased to over 9 MPa by compost rock cracks filled with asphalt/fly ash density reducing the water sorption content of uniaxial test blocks for 25 volume % rock cavity by 85% asphalt and 15% fly ash filling as shown in Figure 16.
The uniaxial compression strength of shale was decreased to lower 8 MPa by compost rock cracks filled with increased fly ash content increasing the water sorption content. The uniaxial compression strength decreased to lower values in tested blocks for 25 volume % rock cavity by 80% asphalt and 20% fly ash filling as shown in Figure 17.
The water saturation of shale tested blocks was decreased over 70% by compost rock cracks filled with increased asphalt content over 60 vol % with increasing the cohesive filler content in tested shale blocks for 25 volume % rock cavity as shown in Figure 17.
In the scope of this study, both the numerical analysis and the proposed new asphalt flay ash fillings were evaluated for the reinforcement of free slides and stabilization of the migrating slope excavation, as well as the necessary weight slice analyses by GEO5 to ensure slope stability in the case sections of Avgamasya Pit Quarry No 2. The asphalt filling performance for free rock sliding was managed for slopes S1 S2 and other critical sub water perched face as seen in Figure 3 caused water filled cracks and weak sub face soil texture.
5.1 Stabilization work and free sliding land and asphalt crack fill study
As a free slide soil -shale slip type was driven possible in rock falls of 2–5 m facing slopes, the main concepts of asphalt flay ash mixture filling was considered for stability and reinforcing weight slices over analyzed slip surface as explained above. Here, the rock cohesion was improved as an isolated block between water planes. The critical slopes were investigated that this block will not slip on planes with certain friction coefficients by improved cohesive matter of asphalt bound filling. The most important part of the problem was to determine the numerical values of crack filling performance by asphalt ash mixture that characterize the region in the stabilization analysis based on this theoretical idea. Numerical values of cohesion in stability problems determined by crack discontinuity. It can be summarized as the orientation of the surfaces, the average friction coefficients between these surfaces, the dimensions of the sliding wedge and the crack water pressures between the surfaces. Since these asphalt bound composite rocks were tested in various measuring techniques, the stability analysis of a rock slope should be done within the maximum and minimum cohesion values of these binder compost properties. The smallest of the safety numbers to be obtained should be used in the reference sizing, by the extensometer wire measurements as seen in Figure 18.
The rock fall, 3 m length crack elevation, asphalt compost filling made difference between the top and the heel point on 15 m. 30 m maximum height of the slope. The frequency distributions of the discontinuity orientations in the region are obtained in the form of a contour diagram as a result of placing a large number of discontinuity orientation measurements in a co-area network and a certain statistical evaluation. From this diagram, the maximum frequency orientations are called the dominant discontinuity orientations and they determine the planes to be used in stability analysis (Eq. (7)).
The mechanical properties of these discontinuity planes in terms of the stability of the rock slopes were free failures and friction coefficients. These properties can be determined as a result of shear tests of samples with discontinuity taken from the field. The Friction matter was critical in shale slopes due to low friction angle of below 22o. The force required to slide a block weighing W on a horizontal plane in a direction parallel to the plane must exceed the co-failure and friction force between the two surfaces. If the cohesion between two surfaces is assumed to be zero, the force required for shear should be W tgϕ,n weight slice chart. (Figure 19). The shear driving force reduced by strength planar levels auger bored and asphalt fill - wire net anchorage were applied as seen in Figure 19.
The free slip motion, shear forces in a slope was varied depending on the volume of the mass that is able to slide. Accordingly, the shape and therefore the weight of the mass that can slide should be found. In order to perform this procedure, it is necessary to know the properties of the mass that can slide and to be included in one of the rock or ground class. Since the soil rock facing slip grounds was considered as heterogeneous, continuous and mostly anisotropic, and the mechanical properties of rocks, which had a discontinuous environment, and therefore the slice method was considered to be applied in even those free rock falls. It was impossible to apply the stability analysis model methods for rock falls applied to the open pit mines and road slopes of the heavily cracked rock slopes with the thought that the material itself was cut during the slope deterioration. Although The free soil slide was occurring with weight slice Bishop methods at 50–60 m length, the rock free slide was calculated for this shale formation so that a vertical limestone slope was fallen down at a height of 7–8 m That was the most common case to be broken as well in the past.
Although the idea of rock blocks sliding on a plane in rock slopes is an element, it is seen that rock wedges (weight blocks) bounded by two or more surfaces are formed as a result of the intersection of various discontinuities in nature, and their stability is more common in engineering works. In such cases, the rock wedge can slide, not on a plane, but on two planes, and its movement can be in the direction of the intersection of two planes. If it is, the event may occur.
The asphalt composed landfill of cable anchorage slopes developed cohesive resistivity and decreased perched water level on free sliding surfaces and the safety factor values reached over 1.5 and 1.8.
Asphaltite open pit mine and asphaltite excavation seam was hard to control against free sliding rock surrounding areas. There were 60 m even higher steeper slopes at angles over 65o. There were sliding large land marly shale masses or shattered shale rock formations. Underground water and harsh climatic conditions contain high risk hazard areas in operation site with higher risk factor of free slide. In order to eliminate rock falls and related events, significant precautions should be taken. The rock fall risk may ease to take precautions using asphalt composite filling. Even the application of elimination rock falls by wire net may reduce water content of soil. In this research, the pillar of 3 m and wire net were used with stabilization. The stability mixture of asphalt fill at certain thickness of 20 mm increased the safety. The low strength and porosity was critical for slide. The hazardous area could be safer by cohesive asphalt bound of rock cracks and long free rock slip surfaces out of water pressure.
Rock samples performed on the laboratory test results in the slope material not permeable that the cohesion value of 54–184.7 kPa, angle of internal friction of the 30.5–32.4o varied among marly shale/limestone with standard classifications. Stability analysis performed in the models srowed in Figure 5 were unstable free slide rock interfaces. By use asphalt stabilization and pillar the hazardous free sliding slopes were converted to the stable condition. Shear force causing free slide was redueed by asphalt flyash mixture filling by cohesion of 400 kPa and 2 MPa shear strength with rock at 19 MPa uniaxial strength.
High strength landfill mass improved the slope stability. However, low strength foam concrete landfill might result in higher water discharge and drier soil condition. The pillar bottom layers avoided water saturation of cracks and slip surface bottom area even sequential top surfaces of slopes.
Dissociation detailed inclinometer observations provided in rocks on free slide area also offered a positive contribution to stability problems.
For those reasons, asphalt composite crack fill can use virtual any classical slope stability programs, rock slope stability calculations in order to do construction safety and dry soil matters as given factor over 1.35.
|c ‘kg/cm2||Effective Cohesion|
|Φ’ο||Effective internal friction angle|
|Φο||Internal friction angle|
|τ kg/cm2||Shear stress|
|σ kg/cm2||Normal stress|
|Wopt||Optimum water content|
|γNatural g/cm3||Natural unit volume weight|
|Saturated g/cm3||Saturated unit volume weight|
|γDry g/cm3||Dry unit volume weight|
|γkmax g/cm3||Maximum dry unit volume weight|
|γs g/cm3||Grain unit volume weight|
|S1, S2, S3, S4||Şırnak free slide slopes no. 1, 2, 3, 4|
|S11||Sample taken from Şırnak Asphaltite Open Pit Mine free slide slope no.|
|SP||In the combined ground classification; poorly graded sand, gravel sand, fine material no|
|SW||In combined ground classification; well-graded sand, gravelly sand, little or no fine material|
|SC||In the combined ground classification; claystone sand, sand-clay mixture|
|GW||In combined ground classification; well graded gravel, gravel-sand mixture, fine material little or no|
|Ji||Joint density sequence at slice i|
|N||Serial distribution of Discontinuity|
|Rc||Shear risk factor|
|τθi||Shear Stress at slip surface at slice i|