Effect of Location and Angle of Cutoff Wall on Uplift Pressure in Diversion Dam

Abstract

Some facility for the prevention of piping, reducing exit gradient and seepage amount under hydraulic structures, is construction of cutoff wall and drain. Therefore, this study compares the efficiency of cutoff wall on some design parameters in an assumed diversion dam cross-section. For this purpose, different placements of cutoff wall with various angle of inclination were used in the dam foundation. Results of this study showed that minimum uplift pressure happens when cut off wall is in the heel (upstream) of the dam. With fixing of longitudinal cut off wall placement, inclination of cutoff wall respect to the vertical position, results in reducing of uplift pressure. Effect of inclination of cutoff wall in upstream of the dam; respect to vertical position, in reducing of uplift pressure is very high.

Influence of Cavity Under Hydraulic Structures on Seepage Characteristics

“…It is also note that for most cases the greatest values of seepage discharge and uplift pressure are when the site of the cavity after the sheet pile (near the downstream structure), while the lowest values of these characteristics are when the location of the cavity before the sheet pile, it is the opposite of what is observe for the exit gradient, where the greatest value of it when the site of cavity before the sheet pile, and the lowest value of the exit gradient when the location of the cavity after the sheet pile (near downstream structure). Figure (4) shows that the ratio of the drop in the amount of discharge when changing the horizontal position of the cavity from the greatest value of it before the sheet pile to a lower value after the sheet pile is about (42%) for each of the three different cases of cavity depths (Y = 1.5, 3.5, 5) m. Figure (5) shows the amount of change in a drop of uplift pressure when the position of the cavity change from the highest value of it before the sheet pile to a lower value after the sheet pile is about (3%) for the depth of the cavity (Y = 1.5, 3.5m), and about (23%) for its depth (y = 5m). Figure (6) shows the increase in the exit gradient at the change of the cavity location from the maximum value of it after the sheet pile to its lowest value by about (38.8%) for each of the cavities locate at depths (Y = 1.5, 3.5 m), and about (10.2%) for the cavity of the depth (Y = 5m).…”

“…(3) Maatooq et al (2014), laboratory study of sandy soil containing cavity to show the effect of location and diameter of the cavity on the amount of seepage over time and the form of flow lines, then established an equation for seepage, and the importance of cavity on seepage proparties. (4) Mansuri et al, (2014), studied the effect of the cutoff on the uplift pressure and finding its efficiency, which showed reducing in uplift pressure (5) Mansuri et al, (2014), prevent piping by using cutoff with different displacements and various angles of inclination to minimize the uplift pressure, where results showed reduse in uplift pressure values (6) El-Jumaily and AL-Bakry, (2013), depending on the method of finite volume and the use of rectangular elements, the seepage was analyzed under the hydraulic structure which contains sheet piles at the toe or heel of it, the assessment showed adjacent results (7) Ahmed, (2013), investigated the confined flow under hydraulic structures, where the hydraulic conductivity of the soil is considered as a three-dimensional arbitrary field, where the results showed isotropic condition (8) Obead, (2013), used finite element model for steady and two dimensional flow analyses under the base of the structure with cut off wall to control leakage. Also used for this purpose is a computer program in (Fortran 90) to find seepage proparties behind the cutoff wall, which led to a good consensus with previous studies (9) Rafiezadeha and Astiani, (2012), A computer analysis program has been developed for seepage of differentiated media based on the boundary element method to show the ability and accuracy of the mathematical model to solve various types of applied three-dimensional seepage problems that ascend in engineering practice.…”

Linked Simulation-Optimization Model for Optimum Hydraulic Design of Water Retaining Structures Constructed on Permeable Soils

“…In contrast, the numerical seepage analysis methods such as the finite element method (FEM) provides accurate solutions for a wide range of the seepage problems encountered in the real field [4,5]. However, these solutions might not be useful, as the resulting designs may not satisfy the safety requirements and also would not optimize the construction costs.…”

Model test and numerical investigation of the effect of the impervious layer’s slope on seepage characteristics under hydraulic structures

“…However, the exit gradient and cost of construction for the blanket was found to be to be less than the cost of the cut-off wall. Mansuri et al (2014) investigated the effect of location and angle of cut-off wall on uplift pressure in diversion dams. Their study showed that the lowest uplift pressure happens when the cut-off wall is located at the heel of the dam.…”