Dike construction has been widely used because of its potential to protect people and properties from overtopping flows. Water levels may exceed a dike crest and cause overtopping flow during high river discharge. This phenomenon has caused serious damage to the dike body due to the reduction of soil shear strength. The increase of water content within particles and its relationship with the development of breach channel failure in downstream and upstream slopes are affected by a series of geotechnical and hydraulic aspects. Transient seepage and slope stability analyses (FOS) were performed in this study using 2D finite element methods and time-history measurements under the effect of sandy and very silty sand soils. The numerical model of SLIDE 2018 was limited by its inability to incorporate all physical processes governing an overtopping breach failure. Numerical analyses were performed to simulate the development of pore pressures and water content at six positions in the dike’s upstream and downstream slopes in physical experimental tests using the van Genuchten Equation and the limit equilibrium method. The numerical results revealed that fine particles increase the pore water pressure and reduce the FOS. Appropriate dike design and maintenance are dependent on surrounding hydraulic conditions, dimensions, and soil types. Non-cohesive materials with fine particles were preferable. Doi: 10.28991/CEJ-SP2021-07-04 Full Text: PDF

The construction of dike materials is an essential parameters in controlling the safety of hydraulic engineering. The dike material is an earthfill material constructed from non-cohesive materials or mixed from cohesive and non-cohesive materials. Overtopping failure can affect the dike stability during water cross above dike crest and could threat people lives and property. It is reduced the matric suctions binds soil particles due to the increasing volumetric water content during the transition of water level from the upstream into downstream slopes. In this paper, two spatial overtopping tests are conducted in Hydraulic Geotechnical laboratories at the Universiti Sains of Malaysia to observe the evolution of horizontal and vertical water levels as well as the development of lateral and vertical erosion processes under constant inflow discharge of 30 L/min. The vertical and horizontal water levels as well as the vertical erosion process are measured using one digital camera installed in front of dike embankment, while the horizontal erosion process was measured using another digital camera installed in front of downstream slope. Two types of coarse sand and very silty sand soils are used to construct dike embankment in small flume channel. The small flume is constructed from transparent PVC material to observe the development of water distributions and erosion processes with sediment box to collect the eroded materials. A pilot channel is cut in dike crest along the side wall of small flume channel to initiate breach channel in the dike crest. The initiation of breach channel is crucial for the evolution breach channel failure in the downstream and upstream slopes. The results show that the vertical and horizontal water levels are distributed faster in coarse sand soil compared with those in the very silty sand soil while the horizontal water levels are distributed faster than vertical water levels for both soils. The permeability of coarse sand increases the velocity of water flow for occupation soil particles and beginning failure in dike crest faster. The presence of fine particles in the very silty sand has reduced the rate of erosion processes inside dike particles in horizontal and vertical directions. The fine particles absorb a large amount of water content and, thus reduce the easiest water infiltration into particles with higher matric suctions. The analyzing of the distributions of water levels and erosion process help to understand the behavior of dike embankment during overtopping failure and increase the maintenance for dikes parts to reduce the potential danger.

The usage of dikes embankments has a great influence on the development of hydraulic engineering. It increases the suitability of water resources for humanity needs. Different Geotechnical and hydraulics powers affect on the stability of dike construction through transition of water flow in the upstream slope. The development of erosion process inside dike construction occurred as a result of an overtopping water flow cross above the dike crest. The dike erosion initiates breach channel inside dike and later widened into upstream and downstream slopes. In this study, a 2D and 3D vertical and horizontal erosions test is constructed in Hydraulic Geotechnical laboratories at the Universiti Sains Malaysia to observe the evolution of the breach channel during spatial overtopping failure. Two constant dike slopes of (1V:3H) and (1V:2.5H) for both upstream and downstream slopes are used as a parametric test during overtopping tests. The vertical and horizontal distributions of water levels are also highlighted prior to overtopping failure. The results indicate that the vertical and horizontal erosion widen the dike breach for slope of 1V:2.5H faster than those for 1V:3H while the spread of water infiltration in horizontal and vertical levels are higher for latter slope than for previous one.

Introduction: Pipelines are among the main systems for conveying fluids over long distances and are typically installed below ground level along most of their alignment. These systems are widely employed for transporting water, petroleum, natural gas, and other fluids, as well as for serving as utility corridors. During seismic events, buried pipelines may experience both transient and permanent ground deformations. Methods: In this study, the influence of key parameters-including pipe wall thickness, burial depth, and soil type-on the behavior of underground pipelines subjected to surface loading and earthquake waves was investigated using PLAXIS 2D. Three pipe diameters and various burial depths were analyzed in both homogeneous and composite soil layers to evaluate pipeline crown displacement. Results: The results show that pipe displacement tends to increase with larger pipe diameters and greater burial depths under various soil conditions and wall thicknesses. Pipelines installed in loose sand demonstrated higher seismic sensitivity compared to those embedded in clay soils, where lower displacement values were observed. Increasing the pipe wall thickness, and consequently its stiffness, resulted in a noticeable reduction in displacement. Additionally, the crown displacement was found to rise with increasing surface loads and pipe diameters, especially at shallow embedment depths. Furthermore, pipelines placed in composite soil exhibited improved performance, with reduced displacements compared to those in uniform soil layers. Discussion: The observed behavior indicates that both geometric properties, such as diameter and thickness, and geotechnical conditions, such as soil type and layering, play critical roles in controlling pipeline response under seismic and surface loading. The improved performance in composite soils suggests that soil stratification can enhance system stability, while loose sand conditions amplify seismic effects due to lower stiffness. Conclusion: The findings of this study provide quantitative relationships that can help explain how burial depth, pipe geometry, and soil conditions influence pipeline displacement under different loading scenarios.

The failure of dike embankments due to overtopping flow plays a crucial role in understanding the mechanisms behind dike erosion, which is essential for effective disaster mitigation. The "SLIDE" program was used to analyze the transient response of pore water pressure (PWP) and volumetric water content (VWC) within a homogeneous coarse sand bed. The authors have previously examined the use of seepage-control elements in 3D simulations of embankment breach failures due to overtopping, conducted in laboratory flumes at the University of Science of Malaysia. In this study, pore water pressure (PWP) and volumetric water content (VWC) were measured at various points beneath the crest and along both the upstream and downstream slopes for three different dike crest widths: 7 cm, 12 cm, and 18 cm. This paper also presents a factor of safety (FOS) analysis across the unsaturated–saturated zones within the dike embankment during the events of overtopping moments until full saturation of the downstream slope. The results indicate that increases in both PWP and VWC occurred across all test groups along the slopes. Narrower crest widths led to higher pore water pressure at the onset of overtopping, while wider crest widths resulted in increased pore pressure toward the end of the erosion process. A reduction in the factor of safety was observed along the crest and downstream slope. However, in dikes with wider crest widths, the length of the embankment decreased due to prolonged flow discharge through the downstream toe and remnants of the upstream slope. The transient flow and slope stability results provide new insights into the coupled hydromechanical behavior of dike soil during overtopping events.

Marine clay is a problematic soil because of its high compressibility and low shear strength, and it must be stabilized before construction. Cement and lime are the usual stabilizers, but both raise environmental concerns: they release significant CO₂ and are vulnerable to sulfate attack. Supplementary cementitious materials (SCMs) offer a more sustainable option. Calcined shale (CS), one such SCM, has performed well in concrete but has been little studied for soil stabilization. This study examines CS as a partial replacement for lime in marine clay, using a ternary mix of CS, palm oil fuel ash (POFA), and lime to improve both strength and durability. The work is divided into two parts. Part (1) treats marine clay with POFA and lime to find the best POFA dosage. Part (2) tests the CS–POFA–lime mix using unconfined compressive strength (UCS), flexural strength, durability, and microstructural analyses to identify the most effective blend. The results show that 3% lime is the optimum dosage, and that 10% CS with 5% POFA is the best combination for replacing part of the lime. Adding 5% lime alone increased UCS, flexural strength, and Young’s modulus by 152%, 50%, and 130%, respectively. Adding CS and POFA pushed these gains to 185%, 173%, and 230%. The findings show that CS, a locally available pozzolanic material, is an effective and more environmentally friendly partial substitute for lime in marine clay stabilization.