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characterized in the Sabalan rockfill dam. It is located 55 km from the northwest of Ardebil-Iran, the dam storage capacity is 105x10°m’, crest height is 77 m, and base width is about 330m. The following dam parameters are given below. In this research, the SEEP/W software was employed due to its proficiency in simulating seepage phenomena. The dam's core on both the upstream and downstream sides consist of three filter layers. This study was examined based on the cutoff depth (d), and position of the cutoff wall in the clay core base (X) based on the relative distance (X/L) for 0,0.25,0.5,0.75 and 1. The hydraulic gradient reaches the minimum amount at the shell. In addition, the hydraulic gradient decreases by transferring the position of the cut-off wall from the heel to the toe of the clay core, and the difference percentage between the two hydraulic gradients of the place of the cut-off wall in the heel and toe of the dam is about 34%. Therefore, the optimal position of the cut walls to reduce the hydraulic gradient is at the toe of the dam core. By further shifting the position of the cutoff wall from the heel to the toe of the dam core, there is an increase in seepage. The

Figure 12 characterized in the Sabalan rockfill dam. It is located 55 km from the northwest of Ardebil-Iran, the dam storage capacity is 105x10°m’, crest height is 77 m, and base width is about 330m. The following dam parameters are given below. In this research, the SEEP/W software was employed due to its proficiency in simulating seepage phenomena. The dam's core on both the upstream and downstream sides consist of three filter layers. This study was examined based on the cutoff depth (d), and position of the cutoff wall in the clay core base (X) based on the relative distance (X/L) for 0,0.25,0.5,0.75 and 1. The hydraulic gradient reaches the minimum amount at the shell. In addition, the hydraulic gradient decreases by transferring the position of the cut-off wall from the heel to the toe of the clay core, and the difference percentage between the two hydraulic gradients of the place of the cut-off wall in the heel and toe of the dam is about 34%. Therefore, the optimal position of the cut walls to reduce the hydraulic gradient is at the toe of the dam core. By further shifting the position of the cutoff wall from the heel to the toe of the dam core, there is an increase in seepage. The

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mecnanism. “A Nazard 1S a potential source Of Narm or danger. it 18s the event or situation that can cause damage or loss. Examples include earthquakes, floods, chemical spills, or system malfunction. Risk is the chance or likelihood of harm occurring due to the combination of a hazard (Giiven & Aydemir, 2021). Several hundred dams have failed, leading to disastrous outcomes and many deaths. Walter Bouldin, Alab dam was the earthen dam with a height of 52 m and a length of 3,407 m, it failed in 1975 due to a seepage problem (Tsakiris et al., 2010). The embankment dam is the common one that faces challenges and failure. In Error! Reference source not found., common potential hazards identified for embankment dams are shown for some Malaysian dams (Hashim et al., 2023). Several studies have proven that internal erosion as well as external factors can lead to dam failures. Many factors can cause a dam to fail, including seepage, internal erosion, overflow from insufficient drainage, freeboard and settlement from earthquakes, and slope failure on the upstream dam body. There were more than 200 major dam failures in the world between 2000 and 2009 (Eldeeb et al., 2023).
mecnanism. “A Nazard 1S a potential source Of Narm or danger. it 18s the event or situation that can cause damage or loss. Examples include earthquakes, floods, chemical spills, or system malfunction. Risk is the chance or likelihood of harm occurring due to the combination of a hazard (Giiven & Aydemir, 2021). Several hundred dams have failed, leading to disastrous outcomes and many deaths. Walter Bouldin, Alab dam was the earthen dam with a height of 52 m and a length of 3,407 m, it failed in 1975 due to a seepage problem (Tsakiris et al., 2010). The embankment dam is the common one that faces challenges and failure. In Error! Reference source not found., common potential hazards identified for embankment dams are shown for some Malaysian dams (Hashim et al., 2023). Several studies have proven that internal erosion as well as external factors can lead to dam failures. Many factors can cause a dam to fail, including seepage, internal erosion, overflow from insufficient drainage, freeboard and settlement from earthquakes, and slope failure on the upstream dam body. There were more than 200 major dam failures in the world between 2000 and 2009 (Eldeeb et al., 2023).
Table 2: Classification of dams according to their hazard potential Table 3: Some dam failure cases (Tsakiris et al., 2010)
Table 2: Classification of dams according to their hazard potential Table 3: Some dam failure cases (Tsakiris et al., 2010)
Figure 1: Main sources of dam failure (Sangodoyin et al., 2014)
Figure 1: Main sources of dam failure (Sangodoyin et al., 2014)
Figure 2: Hierarchy of failure modes (Clarkson & Williams, 2021)
Figure 2: Hierarchy of failure modes (Clarkson & Williams, 2021)
Figure 2: The tectonic divisions of Iraq (Fouad, 2015a)
Figure 2: The tectonic divisions of Iraq (Fouad, 2015a)
Figure 3: Lithological cross sections show the karstification line along the axis of the Mosul dam (V. K. Sissakian et al., 2017)
Figure 3: Lithological cross sections show the karstification line along the axis of the Mosul dam (V. K. Sissakian et al., 2017)
Figure 7: Geological formation under the Badush Dam (Adamo et al., 2019)
Figure 7: Geological formation under the Badush Dam (Adamo et al., 2019)
Table 6: Thickness reduction in steel profiles, in mm acc Ahmed et al., (2013) studied that leakage in sheet pile walls below the hydraulic structure's floor has minimal impact on seepage losses, exit hydraulic gradients, and uplift force. The area and position of the leakage have a significant impact. The sheet pile with an area hole is used when the hole areas are about 2.5% and 10% of the wall area for a single sheet pile at 4m length. The worst case involved leakage in the upper central area of the barrier wall, as the flow path beneath the structure was less and the seepage was larger. The flow efficiency in the barrier can be shown below.
Table 6: Thickness reduction in steel profiles, in mm acc Ahmed et al., (2013) studied that leakage in sheet pile walls below the hydraulic structure's floor has minimal impact on seepage losses, exit hydraulic gradients, and uplift force. The area and position of the leakage have a significant impact. The sheet pile with an area hole is used when the hole areas are about 2.5% and 10% of the wall area for a single sheet pile at 4m length. The worst case involved leakage in the upper central area of the barrier wall, as the flow path beneath the structure was less and the seepage was larger. The flow efficiency in the barrier can be shown below.
Figure 6: Sheet Pile Connection a) Thumb and Finger Type b) Ball and Socket Type (Braja M. Das, 2011)
Figure 6: Sheet Pile Connection a) Thumb and Finger Type b) Ball and Socket Type (Braja M. Das, 2011)
Where Eg is flowing efficiency, Q is flow through the barrier and Qo is flow without sheet pile. Arafat et al., (2022) discovered that the existence of the slot has a great effect on the water contamination under the ground. Flow through the slot depends on the sheet pile depth and slot position. slot increases the contamination discharge. Also, seepage discharge and its characteristics depend on the slot exitance in sheet piles. Arafat et al. (2022) investigated the steady-state seepage and contamination problem in the numerical model (Geo-Studio) to solve groundwater movement, and with the help of the results of (SEEP/W), the module (CTRAN/W) solves contamination time of traveling and concentration distribution. The space diameter was ().1 m, depth of the sheet pile varied from 8m,10m,12m,14m, and 16 m, where the space depth from the ground was 2m,3m,4m, and so on and coefficient of hydraulic conductivity was 1x10’ m/s. Soil porosity and distance from the contaminated source are 0.5m and 10m respectively. Both discharge under the sheet pile and discharge in the slot were computed. Figure 7: Dimensions of the model with slot in the sheet pile and model of the boundary condition.
Where Eg is flowing efficiency, Q is flow through the barrier and Qo is flow without sheet pile. Arafat et al., (2022) discovered that the existence of the slot has a great effect on the water contamination under the ground. Flow through the slot depends on the sheet pile depth and slot position. slot increases the contamination discharge. Also, seepage discharge and its characteristics depend on the slot exitance in sheet piles. Arafat et al. (2022) investigated the steady-state seepage and contamination problem in the numerical model (Geo-Studio) to solve groundwater movement, and with the help of the results of (SEEP/W), the module (CTRAN/W) solves contamination time of traveling and concentration distribution. The space diameter was ().1 m, depth of the sheet pile varied from 8m,10m,12m,14m, and 16 m, where the space depth from the ground was 2m,3m,4m, and so on and coefficient of hydraulic conductivity was 1x10’ m/s. Soil porosity and distance from the contaminated source are 0.5m and 10m respectively. Both discharge under the sheet pile and discharge in the slot were computed. Figure 7: Dimensions of the model with slot in the sheet pile and model of the boundary condition.
Ye BR VVECAUER IR CRAY LEED VEE VV GCRAR IER OU MEG LAA CON EWE BOUL Aghajani et al., (2018) studied in the core earth dam and detected the best position for installing the cut-off based on some Iranian dams Inclined the core layer, also finite element GeoStudio SEEP/W software was used. The position of the cutoff depends on the connection with lower permeable layers. The height and top crest width of the dam are 40m and 5m also the side slope is 1V:3H. The dam foundation layer thickness is 40m as shown in the Figure 8. The cutoff was penetrated to the dam body and extended to the dam foundation. Distance of the sheet pile from the endpoint from the crest was denoted by (x) and it was 0, 5, 15, 25, and 45 m. Embedded depth in the dam has been denoted as (d) and varied by 20, 30, 50, and 60 m. The following results have been collected: the best point to embed the cut-off is 5m away from the dam crest toward the upstream. Seepage from the dam was equal to (0.0000090 m°/s) for all different penetrations of d (20, 30, 50, and 60m). Also, the flux through the dam foundation for the same distance of (x) was about (0.00085 m?*/s/m) for d (20, 30, and 50m). Cutoff wall locations of x = 5 m can be assessed as an optimum point and the cutoff length and its position in the dam body to detect their influences on seepage, uplift pressure, and exit gradient. SEEP/W program has been used too. Figure 8: The phreatic line and flow path for analysis cases with partially embedded cutoff wall of d = 20 m and various locations for cutoff wall; (a) x = 0, (b) x = 15 m, and (c) x = 45 m.
Ye BR VVECAUER IR CRAY LEED VEE VV GCRAR IER OU MEG LAA CON EWE BOUL Aghajani et al., (2018) studied in the core earth dam and detected the best position for installing the cut-off based on some Iranian dams Inclined the core layer, also finite element GeoStudio SEEP/W software was used. The position of the cutoff depends on the connection with lower permeable layers. The height and top crest width of the dam are 40m and 5m also the side slope is 1V:3H. The dam foundation layer thickness is 40m as shown in the Figure 8. The cutoff was penetrated to the dam body and extended to the dam foundation. Distance of the sheet pile from the endpoint from the crest was denoted by (x) and it was 0, 5, 15, 25, and 45 m. Embedded depth in the dam has been denoted as (d) and varied by 20, 30, 50, and 60 m. The following results have been collected: the best point to embed the cut-off is 5m away from the dam crest toward the upstream. Seepage from the dam was equal to (0.0000090 m°/s) for all different penetrations of d (20, 30, 50, and 60m). Also, the flux through the dam foundation for the same distance of (x) was about (0.00085 m?*/s/m) for d (20, 30, and 50m). Cutoff wall locations of x = 5 m can be assessed as an optimum point and the cutoff length and its position in the dam body to detect their influences on seepage, uplift pressure, and exit gradient. SEEP/W program has been used too. Figure 8: The phreatic line and flow path for analysis cases with partially embedded cutoff wall of d = 20 m and various locations for cutoff wall; (a) x = 0, (b) x = 15 m, and (c) x = 45 m.
Table 8: The influence of the sheet pile positions on seepage discharge and pore water pressure.
Table 8: The influence of the sheet pile positions on seepage discharge and pore water pressure.
Figure 9: Model of the dam, soil with a cavity system.
Figure 9: Model of the dam, soil with a cavity system.
The conclusion drawn is that using a sheet pile at the upstream location results in ¢ significant reduction in uplift pressure forces compared to the scenario where nc sheet pile is used. According to the information provided, the upstream sheet pile causes a decrease of 75% in uplift pressure forces. Mansuri et al., (2014) investigated the cutoff of various placements with different angles on the uplift pressure in the diversion dam foundation using the Seep/w model. Poisson’s Equation for water movement in a porous medium was used as shown below. The underlying soil was isotropic with a permeability of (10° m/s), while the cutoff wall was constructed using a low-permeability material (10° m/s). There were 10 different cases detected based on ratio (b1/b) including 0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9 in which (b/) is the distance from sheet pile tc upstream end and (b) is the dam base length. Therefore, it can be concluded that the optimal location for the cutoff aimed at reducing uplift force, is at the upstream (heel) of the dam. The intensity factor at the heel of the dam was 0.35 and this equation below was obtained. Table 9: The influence of the sheet pile position on X, Y exit gradient
The conclusion drawn is that using a sheet pile at the upstream location results in ¢ significant reduction in uplift pressure forces compared to the scenario where nc sheet pile is used. According to the information provided, the upstream sheet pile causes a decrease of 75% in uplift pressure forces. Mansuri et al., (2014) investigated the cutoff of various placements with different angles on the uplift pressure in the diversion dam foundation using the Seep/w model. Poisson’s Equation for water movement in a porous medium was used as shown below. The underlying soil was isotropic with a permeability of (10° m/s), while the cutoff wall was constructed using a low-permeability material (10° m/s). There were 10 different cases detected based on ratio (b1/b) including 0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9 in which (b/) is the distance from sheet pile tc upstream end and (b) is the dam base length. Therefore, it can be concluded that the optimal location for the cutoff aimed at reducing uplift force, is at the upstream (heel) of the dam. The intensity factor at the heel of the dam was 0.35 and this equation below was obtained. Table 9: The influence of the sheet pile position on X, Y exit gradient
Table 11: Properties of the sheet piles. The result indicated if the sheet pile position shifts away from the downstream end, the exit gradient increases. When the sheet pile remains in a fixed position, the exit gradient decreases as the length of the sheet pile increases. The best case was a sheet pile depth of 20m and fixed at the dam toe or at least at B/8. At the mentioned point the value of the exit gradient was 0.5 while was equal to 1.8 for 3B/8. The factor safety decreased when the sheet pile moved away from the downstream end. The sheet pile position shifts towards the downstream end, increasing average flow
Table 11: Properties of the sheet piles. The result indicated if the sheet pile position shifts away from the downstream end, the exit gradient increases. When the sheet pile remains in a fixed position, the exit gradient decreases as the length of the sheet pile increases. The best case was a sheet pile depth of 20m and fixed at the dam toe or at least at B/8. At the mentioned point the value of the exit gradient was 0.5 while was equal to 1.8 for 3B/8. The factor safety decreased when the sheet pile moved away from the downstream end. The sheet pile position shifts towards the downstream end, increasing average flow
Figure 11: Sketch of boundary conditions and the foundation properties.
Figure 11: Sketch of boundary conditions and the foundation properties.
Figure 12:Flow net of the optimum model within (d/b = 0.2) in relative cutoff location of (0.839) from the upstream.
Figure 12:Flow net of the optimum model within (d/b = 0.2) in relative cutoff location of (0.839) from the upstream.
The conclusion drawn is that using a sheet pile at the upstream location results in a significant reduction in uplift pressure forces compared to the scenario where no sheet pile is used. According to the information provided, the upstream sheet pile causes a decrease of 75% in uplift pressure force. Angelov & Asr, (2021) discovered the upstream cutoff inclination efficiency under the concrete foundation dam to mitigate the seepage characterizes risk. The angles will vary from 0° to 180°, progressively increasing at an interval of 30°, the model of the study was analyzed due to finite element geotechnical software — PLAXIS 2D. All angles were measured in the counter-clockwise direction. The seepage discharge beneath the toe points at angles (0°, 30°, 60°, 90°, 120°, 150°, and 180°) amounted to (1.164x107, 1.087x10°, 1.045x10°, 1.003x10°, 1.098x10°, 1.334x10°, 1.509x10°) m%s, respectively. The lowest discharge rates were observed at angles 60° and 90°, with the minimum discharge occurring beneath the cutoff wall point at 60° this is because, in this arrangement, the water path is maximally extended. This essentially results in an increased duration for water molecules to traverse from areas of higher potential energy to points of lower potential energy. Uplift pressure and seepage are closely related to each other because as water flows through the soil profile, it generates upward pressure on the horizontal base of the dam the test results were (20.89, 21.16, 21.12, 20.82, 20.73, 21.31 and 21.06 KN/m?) respectively. The minimum uplift pressure was for angle 120° and this upward force has a great role in foundation dam stability, if the dam weight is unsuitable to resist this force, it may cause a reduction in the shear stress between the dam and soil causing the structure's floor to rupture, ultimately resulting in a collapse. Khassaf Al-Saadi et al., (2011) discovered when the cut-off is located at the toe, increased exit gradient values are observed if the cut-off is inclined towards the upstream side (© is less Table 12:Influence of the sheet pile inclination and position on seepage, exit gradient, and uplift pressure reduction.
The conclusion drawn is that using a sheet pile at the upstream location results in a significant reduction in uplift pressure forces compared to the scenario where no sheet pile is used. According to the information provided, the upstream sheet pile causes a decrease of 75% in uplift pressure force. Angelov & Asr, (2021) discovered the upstream cutoff inclination efficiency under the concrete foundation dam to mitigate the seepage characterizes risk. The angles will vary from 0° to 180°, progressively increasing at an interval of 30°, the model of the study was analyzed due to finite element geotechnical software — PLAXIS 2D. All angles were measured in the counter-clockwise direction. The seepage discharge beneath the toe points at angles (0°, 30°, 60°, 90°, 120°, 150°, and 180°) amounted to (1.164x107, 1.087x10°, 1.045x10°, 1.003x10°, 1.098x10°, 1.334x10°, 1.509x10°) m%s, respectively. The lowest discharge rates were observed at angles 60° and 90°, with the minimum discharge occurring beneath the cutoff wall point at 60° this is because, in this arrangement, the water path is maximally extended. This essentially results in an increased duration for water molecules to traverse from areas of higher potential energy to points of lower potential energy. Uplift pressure and seepage are closely related to each other because as water flows through the soil profile, it generates upward pressure on the horizontal base of the dam the test results were (20.89, 21.16, 21.12, 20.82, 20.73, 21.31 and 21.06 KN/m?) respectively. The minimum uplift pressure was for angle 120° and this upward force has a great role in foundation dam stability, if the dam weight is unsuitable to resist this force, it may cause a reduction in the shear stress between the dam and soil causing the structure's floor to rupture, ultimately resulting in a collapse. Khassaf Al-Saadi et al., (2011) discovered when the cut-off is located at the toe, increased exit gradient values are observed if the cut-off is inclined towards the upstream side (© is less Table 12:Influence of the sheet pile inclination and position on seepage, exit gradient, and uplift pressure reduction.
Table 13: The whole test results for uplift pressure and exit gradient. Obead (2013) investigated the different positions of the cutoff inclination on the steady-state two-dimensional water seepage through the foundation of a dam structure using FORTRAN 90. The inclination cutoff was embedded in U/S, mid- base, and D/S places. Inclination angles were measured as the counterclockwise direction for (0, 30°, 45°, 60°, 90°, 105°,120°, 150°). The maximum ranges for uplift ratios were obtained when (© < 90°) counterclockwise for the upstream sheet pile, then it decreased when the angle ratio was between 90° to 120° and started to increase again. Uplift heads for various points on the dam base were identified using the parameter (Xm/Ld = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0), where Xm represents the target point and Ld is the length of the dam base. For midpoint sheet pile installation, the minimum uplift head was observed at 150 degrees for different points. The optimal condition for minimizing uplift pressure was associated with angles (© > 90 degrees), and a rapid decrease in the uplift head was noted for (Xm/Ld > 0.5) towards the downstream direction. The maximum value for exit gradient was noted when the inclination angle was almost equal to 150° for both U/S and mid-base cutoff positions. The downstream (D/S) exit gradient of the dam structure for D/S cutoff penetration diminished as the angle (©) increased towards the downstream side (0 >90°). This trend continued until the cutoff inclination angle reached approximately 120°, beyond that the exit gradient developed with further increases in (0). The optimum angles for U/S, Mid base, and D/S sheet pile for minimum seepage achievement were around 60°, 105° and 120° respectively.
Table 13: The whole test results for uplift pressure and exit gradient. Obead (2013) investigated the different positions of the cutoff inclination on the steady-state two-dimensional water seepage through the foundation of a dam structure using FORTRAN 90. The inclination cutoff was embedded in U/S, mid- base, and D/S places. Inclination angles were measured as the counterclockwise direction for (0, 30°, 45°, 60°, 90°, 105°,120°, 150°). The maximum ranges for uplift ratios were obtained when (© < 90°) counterclockwise for the upstream sheet pile, then it decreased when the angle ratio was between 90° to 120° and started to increase again. Uplift heads for various points on the dam base were identified using the parameter (Xm/Ld = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0), where Xm represents the target point and Ld is the length of the dam base. For midpoint sheet pile installation, the minimum uplift head was observed at 150 degrees for different points. The optimal condition for minimizing uplift pressure was associated with angles (© > 90 degrees), and a rapid decrease in the uplift head was noted for (Xm/Ld > 0.5) towards the downstream direction. The maximum value for exit gradient was noted when the inclination angle was almost equal to 150° for both U/S and mid-base cutoff positions. The downstream (D/S) exit gradient of the dam structure for D/S cutoff penetration diminished as the angle (©) increased towards the downstream side (0 >90°). This trend continued until the cutoff inclination angle reached approximately 120°, beyond that the exit gradient developed with further increases in (0). The optimum angles for U/S, Mid base, and D/S sheet pile for minimum seepage achievement were around 60°, 105° and 120° respectively.
YodJ PAUP UE UE BED WULMUTE VV ALE ULE OUUC VES WHALE ALUUEISUNDS Sheet pile depth has a great role in seepage mitigation due to increasing flow path. Moharrami et al., (2015b) investigated the sheet pile length and its role in seepage characteristics. SEEP/W, a component of GeoStudio, was employed to carry out numerical analyses. The dam face had a slope inclination of 30.96° relative to the horizontal axis, with a ratio of 10:6 for horizontal to vertical components, for both the upstream and downstream faces. This same slope was applied consistently across all models. Soil types for foundation layers included clay and silty clay with permeability values of 1x10° m/s and 5x10’ m/s respectively. Concrete impermeable wall material was used to construct the cut-off wall in dimensions (2m length x 1m width) and (3m length x | m width) in two different cases. The result indicated the length of the sheet pile has the role on seepage characterizes modifications. The pore water pressure is reduced by increasing the sheet pile length. Changing the cutoff depth for silty clay is better than clay only. When the cutoff length extends, it intersects with an increased number of flow lines, resulting in a decline in velocity with the growing length of the cutoff wall. The value for total head along the foundation decreased with increasing the cutoff length. The best position to penetrate the cutoff with a suitable length was the downstream point. The length of sheet piles had the great effect on the seepage and it reduced the seepage, exit gradient and uplift pressure under the dam. The chosen permeability for the materials at the cutoff in both horizontal and vertical orientations was | x 10° m/sec, and the thickness was set at 1 meter. The Sattarkhan Earth Fill Dam was selected to examine this research in Northwest Iran. Cutoff length was 5,10 and 15m and penetrated in different positions in the dam core. The cutoff was installed in 7 different places in the dam foundation from the dam upstream heel as 7, 26.7, 46.5, 53, 59.5, 80 and 100 m as shown in the figure below.
YodJ PAUP UE UE BED WULMUTE VV ALE ULE OUUC VES WHALE ALUUEISUNDS Sheet pile depth has a great role in seepage mitigation due to increasing flow path. Moharrami et al., (2015b) investigated the sheet pile length and its role in seepage characteristics. SEEP/W, a component of GeoStudio, was employed to carry out numerical analyses. The dam face had a slope inclination of 30.96° relative to the horizontal axis, with a ratio of 10:6 for horizontal to vertical components, for both the upstream and downstream faces. This same slope was applied consistently across all models. Soil types for foundation layers included clay and silty clay with permeability values of 1x10° m/s and 5x10’ m/s respectively. Concrete impermeable wall material was used to construct the cut-off wall in dimensions (2m length x 1m width) and (3m length x | m width) in two different cases. The result indicated the length of the sheet pile has the role on seepage characterizes modifications. The pore water pressure is reduced by increasing the sheet pile length. Changing the cutoff depth for silty clay is better than clay only. When the cutoff length extends, it intersects with an increased number of flow lines, resulting in a decline in velocity with the growing length of the cutoff wall. The value for total head along the foundation decreased with increasing the cutoff length. The best position to penetrate the cutoff with a suitable length was the downstream point. The length of sheet piles had the great effect on the seepage and it reduced the seepage, exit gradient and uplift pressure under the dam. The chosen permeability for the materials at the cutoff in both horizontal and vertical orientations was | x 10° m/sec, and the thickness was set at 1 meter. The Sattarkhan Earth Fill Dam was selected to examine this research in Northwest Iran. Cutoff length was 5,10 and 15m and penetrated in different positions in the dam core. The cutoff was installed in 7 different places in the dam foundation from the dam upstream heel as 7, 26.7, 46.5, 53, 59.5, 80 and 100 m as shown in the figure below.
Figure 14: Effect of the cutoff position and length on the seepage and uplift pressure.
Figure 14: Effect of the cutoff position and length on the seepage and uplift pressure.
The following results below have been achieved as shown in Figure 17. The relative depth between the penetration depth of cutoff (d) to depth of the permeable foundation (D) is shown in Figure 17, where the foundation depth varied at (15, 22.5, 30, 45 and 60 cm) and the relative depth has been assessed as (0.2, 0.4, 0.6, 0.7 and 1). The minimum total discharge for seepage occurred in the minimum foundation. However, the foundation depth increases the seepage and coefficient increase directly.
The following results below have been achieved as shown in Figure 17. The relative depth between the penetration depth of cutoff (d) to depth of the permeable foundation (D) is shown in Figure 17, where the foundation depth varied at (15, 22.5, 30, 45 and 60 cm) and the relative depth has been assessed as (0.2, 0.4, 0.6, 0.7 and 1). The minimum total discharge for seepage occurred in the minimum foundation. However, the foundation depth increases the seepage and coefficient increase directly.
Figure 15: Graph between relative depth and total discharge.
Figure 15: Graph between relative depth and total discharge.
Table 15: Test result for different cutoff depths related to uplift pressure and exit gradient. Abdul and Jamel, (2017) used the software program to detect the seepage phenomenon with different locations, different lengths, and double soil layers on the seepage case. Using ANN networking with the SEEP/W program showed that the differences are 5%, 2%, and 6% for the exit gradient, discharge, and uplift pressure, respectively, at the base of the hydraulic structure. The length of the cutoff can control the flow properties as concluded by (Sazzad, 2019). The whole test results included following different cases with 729 runs bases on the space distance different soil layers and sheet pile depth, both cutoffs were penetrated at U/S and D/S heel and toes points and second layer has lower permeability than first one, the whole test parameters and values shown below.
Table 15: Test result for different cutoff depths related to uplift pressure and exit gradient. Abdul and Jamel, (2017) used the software program to detect the seepage phenomenon with different locations, different lengths, and double soil layers on the seepage case. Using ANN networking with the SEEP/W program showed that the differences are 5%, 2%, and 6% for the exit gradient, discharge, and uplift pressure, respectively, at the base of the hydraulic structure. The length of the cutoff can control the flow properties as concluded by (Sazzad, 2019). The whole test results included following different cases with 729 runs bases on the space distance different soil layers and sheet pile depth, both cutoffs were penetrated at U/S and D/S heel and toes points and second layer has lower permeability than first one, the whole test parameters and values shown below.
Table 16: Test parameters and values. The test result indicated the discharge variation decreased where both sheet pile extended to second layer and it decreased by about 60.5% where the downstream one depth increased from 2.m to 4.5m for most cases. Changing layer thickness also changed the uplift pressure and discharge where the higher permeable layer thickness increased the uplift pressure increased and discharge increased proportionally. The discharge decreased of about (5.6%) with an increase in (d2 from (2m) to (2.5m). There was an approximately (60.5%) reduction in discharge when (d2) increased from (2.5m) to (4.5m). Uplift pressure depended on soi discharge proportionally. It decreased related to (d1/d2) ratio, it had an indirec relationship with downstream cutoff depth. It increased at 31% to 90% where d2 increased from 2m to 4.5m respectively. The best situation for decreasing the uplift pressure is to extend the first cutoff to penetrate the low permeable layer, decreasing the soil permeability help to reduce discharge and uplift pressure as concluded by (Abdul & Jamel, 2016). The exit gradient is influenced by the permeability of the soil; if the second layer with lower permeability is increased relative to the first layer, the exit gradient also increases. This is because water, unable to infiltrate the deeper layer, moves laterally and reaches the surface more easily. It can be concluded the sheet pile length has a great role in reducing the uplift pressure and seepage. The optimum situation is to extend the sheet piles to meet the impermeable layer with consideration of its position and inclination. Hamad et al. (2023) examined the impact of varying sheet pile depths at upstream (dz), downstream (d2), and intermediate (d3) locations on water seepage through a uniform and isotropic soil foundation. Utilized the SEEP/W code within the GeoStudio software (2018) to analyze steady-state flow. The finding indicated as the sheet pile depth increases; the seepage ratio decreases. The dam foundation hydraulic conductivity was 1x10" 'l m/s, upstream water depth, impermeable layer depth, and dam base width were 25m, 25m, and 23m respectively, and space between sheet pile was computed as (X = 0.0, 11.5, and 23 m, respectively). The following cases below were obtained. a) Case I: when the only downstream sheet pile was penetrated. The flow line was near the upstream base of the dam. d2 = 15m, flow line passed near the heel.
Table 16: Test parameters and values. The test result indicated the discharge variation decreased where both sheet pile extended to second layer and it decreased by about 60.5% where the downstream one depth increased from 2.m to 4.5m for most cases. Changing layer thickness also changed the uplift pressure and discharge where the higher permeable layer thickness increased the uplift pressure increased and discharge increased proportionally. The discharge decreased of about (5.6%) with an increase in (d2 from (2m) to (2.5m). There was an approximately (60.5%) reduction in discharge when (d2) increased from (2.5m) to (4.5m). Uplift pressure depended on soi discharge proportionally. It decreased related to (d1/d2) ratio, it had an indirec relationship with downstream cutoff depth. It increased at 31% to 90% where d2 increased from 2m to 4.5m respectively. The best situation for decreasing the uplift pressure is to extend the first cutoff to penetrate the low permeable layer, decreasing the soil permeability help to reduce discharge and uplift pressure as concluded by (Abdul & Jamel, 2016). The exit gradient is influenced by the permeability of the soil; if the second layer with lower permeability is increased relative to the first layer, the exit gradient also increases. This is because water, unable to infiltrate the deeper layer, moves laterally and reaches the surface more easily. It can be concluded the sheet pile length has a great role in reducing the uplift pressure and seepage. The optimum situation is to extend the sheet piles to meet the impermeable layer with consideration of its position and inclination. Hamad et al. (2023) examined the impact of varying sheet pile depths at upstream (dz), downstream (d2), and intermediate (d3) locations on water seepage through a uniform and isotropic soil foundation. Utilized the SEEP/W code within the GeoStudio software (2018) to analyze steady-state flow. The finding indicated as the sheet pile depth increases; the seepage ratio decreases. The dam foundation hydraulic conductivity was 1x10" 'l m/s, upstream water depth, impermeable layer depth, and dam base width were 25m, 25m, and 23m respectively, and space between sheet pile was computed as (X = 0.0, 11.5, and 23 m, respectively). The following cases below were obtained. a) Case I: when the only downstream sheet pile was penetrated. The flow line was near the upstream base of the dam. d2 = 15m, flow line passed near the heel.
Figure 16: Seepage rate variation (q/kh) with different sheet pile length. The rate of exit gradient reduction is reduced by extending sheet pile depth eradually. A notable decrease in the relative exit gradient was achieved at its highest point when the sheet pile was driven into the toe for example (95.07%, 93.20%, and 89.38%) for cutoff length (5,10 and 15m respectively), as previously noted, the exit eradient is influenced by the flow pattern and uplift pressure. The extension of sheet piles near the toe results in diverting the flow line away from the toe, leading to the removal of the flow line at the toe and the occurrence of soil boiling further downstream, as previously discussed (Ahmed & Elleboudy, 2010). The most optimum cases related to reduction the pressure head is to penetrating sheet pile near the heel. b) Case II: when Upstream and downstream sheet pile used, their depth changed
Figure 16: Seepage rate variation (q/kh) with different sheet pile length. The rate of exit gradient reduction is reduced by extending sheet pile depth eradually. A notable decrease in the relative exit gradient was achieved at its highest point when the sheet pile was driven into the toe for example (95.07%, 93.20%, and 89.38%) for cutoff length (5,10 and 15m respectively), as previously noted, the exit eradient is influenced by the flow pattern and uplift pressure. The extension of sheet piles near the toe results in diverting the flow line away from the toe, leading to the removal of the flow line at the toe and the occurrence of soil boiling further downstream, as previously discussed (Ahmed & Elleboudy, 2010). The most optimum cases related to reduction the pressure head is to penetrating sheet pile near the heel. b) Case II: when Upstream and downstream sheet pile used, their depth changed
Table 17: Seepage Parameters reduction related to utilization both U/S and D/S sheet pile with different length with compared to single sheet pile utilization.
Table 17: Seepage Parameters reduction related to utilization both U/S and D/S sheet pile with different length with compared to single sheet pile utilization.
Related topics:
Geological EngineeringDam - Seepage AnalysisSoil Foundations
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