Peat Soil Compaction Characteristic and Physicochemical Changes Treated with Eco-Processed Pozzolan (EPP)

Peat soil was defined as the highly organic surface layer derived primarily from plant remains. Peat, on the other hand, was the subsurface of wetland systems, consisting of unconsolidated superficial layers with a high non-crystalline colloid (humus) content. Peat soils have a low shear strength of 5 to 20 kPa, a high compressibility of 0.9 to 1.5, and a high moisture content of >100%. The purpose of the study was to prognosticate the potential of Eco-Processed Pozzolan (EPP) as peat soil stabilization material with improved technique and its consequence of the methods, which was the peat soils index properties and analyse the characteristics of the peat soil stabilization before and after treatment using Eco-Processed Pozzolan (EPP). The soil was mixed with 10, 20, and 30% Eco-Processed Pozzolan (EPP) and then compacted (compaction test) in a metal mould with an internal diameter of 105 mm using a 2.5 kg rammer of 50 mm diameter, freefalling from 300 mm above the top of the soil Three layers compaction of approximately equal depth and 27 blows spread evenly over the soil surface for each layer. The expected result to accomplish the main purpose was to prognosticate the potential Eco-Processed Pozzolan (EPP) as peat soil stabilization material with improved technique and its consequence of the methods. According to the findings, peat soil treated with EPP will transform its qualities from peat to usable soil. However, the presence of moisture will reduce the mixture's ability. According to the findings of this study, the optimum EPP for stabilizing peat soils was 30-40%. Correspondingly, the elemental composition of peat soil mixed with EPP improved regardless of Carbon, Ca composition. Comparatively, the amount of Silicon, Si increased from 6.5% (Peat + EPP 10%) to 12.9% (Peat + EPP 40%) due to the crystallization of EPP and peat. Doi: 10.28991/CEJ-2023-09-01-07 Full Text: PD

Relationship of Rainfall Intensity with Slope Stability

The impact of rainfall on landslides is not an uncommon issue worldwide, including in Malaysia. It is a major challenge for geotechnical engineers to ensure the constructed slope is safe and can sustain longer periods of time, including during heavy rainfall. Kota Belud, Sabah, has been selected as the study area to meet the study objectives. Heavy rainfall has been recorded every year within Kota Belud, which has caused a repetition of landslide occurrences within the hilly areas, especially during the monsoon season. Presently, there is no local procedure for determining the rainfall intensity value for slope stability analysis. This study utilized the rainfall intensity value from Hydrology Procedure 26. Seepage analysis conducted shows rainwater infiltration has caused the groundwater level to increase from rainfall starts until 0.5 m below ground level and decrease after rainfall stops, creating fluctuations in the groundwater level during the wet and dry conditions within the wetting front. The factor of safety of the slope shows a decreasing trend, with a reduction of around 27 to 33% after 24 hours of rainfall in conjunction with the changes in groundwater level. However, the factor of safety increased by around 3% from the initial condition after 48 hours. The objective of this study is to identify the factor of safety of a rainfall-induced slope within Kota Belud utilizing the rainfall intensity design limits from Hydrology Procedure 26. Doi: 10.28991/CEJ-SP2023-09-06 Full Text: PD

Investigating the Effect of Gradation, Temperature and Loading Duration on the Resilient Modulus of Asphalt Concrete

This research was carried out to assess the effect of aggregate skeleton, temperature variation, and loading duration on the resilient modulus of asphalt concrete mixtures. Two different gradation methods, i.e., the conventional method of gradation and the Bailey method of gradation, were adopted to design the aggregate skeleton. The effect of these gradation methods, with temperature and loading duration, on the resilient modulus of asphalt concrete has not been previously investigated. The Modified Marshall Test was used to determine optimum binder content against 4% air voids, and then volumetric and strength parameters were calculated against optimum binder content. For performance tests, specimens were prepared at optimum binder content using a Superpave gyratory compactor. An indirect tensile strength test on both types of mixtures was conducted, and a 20% value of indirect tensile strength was kept for peak load, whereas 10% was kept for seating load for conducting resilient modulus tests. The tests were conducted at 100 and 300 ms duration loads under two different temperatures, i.e., 25 oC and 40 oC. The results declared that aggregate skeleton, temperature, and loading duration have a prominent effect on the resilient modulus of asphalt concrete mixtures. Bailey gradation mixtures disclosed higher resilient modulus values than conventional gradation mixtures. Higher values of resilient modulus were observed for both gradation mixtures at low temperatures and under small duration loads than at high temperatures and large duration loads. The results of the two-way factorial design also confirmed the above findings. Doi: 10.28991/CEJ-2022-08-02-07 Full Text: PD

Estimation of Overall Fatigue Life of Jack-up Leg Structure

Jack-up platforms are designed to work in three conditions: Transit, Preloading and Operating. The fatigue life of the jack-up platforms in operating condition will be determined to be similar to that of offshore fixed steel structures. In preloading conditions, fatigue damage is usually ignored. Up to now, the fatigue damage of the jack-up leg structure in transit conditions has been calculated at approximately 20% of the total fatigue damage of the jack-up leg structure in two conditions (transit and operating). The approximate calculation method is usually accepted by consultants and register agencies. If the approximation is used, the fatigue life of the jack-up leg structure will be calculated only as for the jacket structure of the fixed offshore structure, with 80% of the allowable fatigue life based on standards. The approximation proved to have many disadvantages: the different travel times of each jack-up rig cannot be mentioned; hot spots that need to be maintained during the transit condition have not been pointed out; it is difficult to guarantee the safety of the jack-up leg structures in the transit condition. In order to overcome the limitations of the approximation method, this paper will propose a method to predict the overall fatigue life of the jack-up leg structure in three main problems. Firstly, we use the analysis method of fatigue of fixed steel offshore structures for jack-up leg structures in operating conditions. Secondly, we suggest a method to analyze the fatigue of the structures in transit conditions. Herein, motion analysis and determination of inertia forces on the leg structure are performed by the Boundary Element Model (BEM) in SACS software. Then the inertia forces are assigned to a Finite Element Model (FEM) in SACS to decide the internal forces of the structures. Hotspot stresses are determined by combining nominal stress from FE analysis results with a concentrated stress factor from the analysis of joint local models in the ANSYS program. Then, fatigue damage and fatigue life of hotspots of the structure are determined in the transit condition. Finally, a formula is suggested to determine total fatigue damage in operating conditions and transit conditions with different cases in relation to different fraction factors. These results are used to predict fatigue life corresponding to the most dangerous cases of structural joints. These new suggestions are applied to fatigue analysis for jack-up Tam Dao 05. Currently, the Tam Dao 05 platform has been operating in the Vietnam East Sea. Doi: 10.28991/CEJ-2022-08-03-06 Full Text: PD

Numerical Modeling for the Effect of Soil Type on Stability of Embankment

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: PD

Assessing the Effect of GGBFS Content on Mechanical and Durability Properties of High-Strength Mortars

As a large amount of steel is produced for the industrialization and modernization of Vietnam, a correspondingly large quantity of steel slag is also released annually. Besides, the demand for mortar is increasing due to urbanization, especially for the high-strength and durability mortar used for important constructions and structures in aggressive environmental areas. This study aims to carry out further research into high-strength mortars incorporating ground granulated blast furnace slag (GGBFS). The control mixture was designed with a water-to-binder ratio of 0.2, and the amount of silica fume used was equal to 25% of the total binder amount by mass. Four other mixtures were designed using GGBFS to substitute for 15, 30, 45, and 60% of cement by mass. The engineering properties of fresh and hardened mortars were comprehensively investigated, especially the durability properties. The microstructure of these mortars was also examined using scanning electron microscopy. Test results show that replacing 15 or 30% of cement with GGBFS yields an improvement in mortar's strength and durability properties. All the mortars in this study show excellent qualities with high strength, low water absorption, and high resistance to chloride attack. Moreover, the presence of GGBFS reduces the shrinkage of mortar caused by the drying process. Doi: 10.28991/CEJ-2022-08-05-07 Full Text: PD

Geotechnical and Mechanical Characterization of Lateritic Soil Improved with Crushed Granite

Since many years, road infrastructures in West Africa are most often subject to premature degradations despite the large number of studies. This problem is often due to the poor control of the behaviour of materials used for the pavement, but also to the scarcity of good quality materials. Nowadays, with economic development, there is a necessity for road infrastructures of good quality. In this framework, the main objective was to study the vertical geotechnical variability of the gravelly lateritic soil from the Saaba site in Burkina Faso and to improve their performances by adding crushed granite. The results show that the physical properties of the soils are almost identical depending on the depth. However, a small difference in the mechanical properties was observed. Due to their poor characteristics, these materials cannot be used for the sub-base layer according to the pavement design guide for tropical countries, CEBTP [1]. In order to improve their geotechnical and mechanical characteristics, crushed granite of class 0/31.5 mm was added at different percentages: 20, 25, 30, and 35%. It appears that the plasticity index, the methylene blue value, as well as the optimal water content of the material decreased. The soaked CBR recorded a maximum relative increase of 164% (from 14 to 37%) with the addition of 20 to 30% of crushed granite. With the addition of 20 to 30% of crushed granite, Young's modulus and unconfined compressive strength also showed a clear increase of 309% (from 80 to 327 MPa) and 140% (from 0.72 to 1.73 MPa). By comparing the results with the CEBTP specifications, the addition of 30% of granites at 95% compactness allows the materials to have a CBR that exceeds the value of 30% and can be used in the sub-base layer of road pavement. The addition of 30% granite allows the materials to record an unconfined compressive strength higher than 0.5-1.5 MPa, which corresponds to lateritic soil suitable for sub-base layer according to Messou [2]. After the addition of 30% granite, the materials record a Young's modulus greater than 300 MPa and can be used as a base layer. The assessment of the improvement of mechanical performance simultaneously based on the CBR, the Young's modulus, and the compressive strength showed the contradictory evolution of the results from these different parameters. A discussion was made on the relationship between these parameters. Doi: 10.28991/CEJ-2022-08-05-01 Full Text: PD

Properties of Concrete Produced using Surface Modified Polyethylene Terephthalate Fibres

Conventional techniques of improving the bond properties of virgin Polyethylene Terephthalate Fibres reduce the mechanical strength of the fibres, are labour intensive, and present environmental hazards in the case of chemical treatment. This study introduces a new way of improving the bond properties of fibres obtained from waste Polyethylene Terephthalate bottles by coating the surface of the fibres with a thin layer of sand to counteract the above-mentioned shortcomings. Their performance was compared to that of embossed, serrated, and straight fibres and a control mix without fibres. Workability, compressive strength, tensile and flexural strength were used to assess this performance. Constant fibre length, width, and content were maintained for this exercise. Compared to the other fibres, sand-coated fibres gave the highest increment in tensile and flexural strength of 9.49% and 11.61% compared to the control mix, even though concrete's workability and compressive strength were decreased. Furthermore, the optimization of the fibre length and content for the sand-coated fibres was carried out. The 75 mm long fibres showed the highest improvement in tensile strength of 13.76% and flexural strength of 12.49% compared to other fibre lengths. The optimum percentage of fibres was 1.25% with a 15.49% and 17.26% increment in tensile and flexural strengths, respectively. Doi: 10.28991/CEJ-2022-08-06-03 Full Text: PD

Seismic Behavior of Reinforced Masonry Structure: Relation between the Behavior Factor and the Ductility

The present work concerns a numerical study of the behavior of reinforced masonry (RM) structures under seismic loading. These structures are made of small hollow elements with reinforcements embedded in the horizontal joints. They were dimensioned according to the rules and codes commonly used. They are subject to vertical loads due to their own weight, and to horizontal loads due to seismic forces introduced by the accelerograms. The software used is the non-linear analysis program Drain2D, based on the finite element method, where the shear panel element was introduced. A series of calculations was performed on a number of structures at different levels, excited by three major accelerograms (El Centro, Cherchell, and Kobe). Throughout the study, our main interest is to evaluate the behaviour factor, the ductility, and the failure mode of these structures while increasing the intensity of earthquakes introduced. The results of this present study indicate that the average values of the behaviour factor and the global ductility are of the order of q≈μ≈3.00. The reinforced masonry structures studied have been broken by interstage displacement. The results given by the study are comparable to those given in the literature and in Eurocode 8. The behavior of reinforced masonry under a seismic load is similar to the behavior of reinforced concrete; it is a ductile behavior that allows the dissipation of the energy transmitted by the earthquake. These numerical studies confirm and complete the experimental work carried out by other researchers. Doi: 10.28991/CEJ-2022-08-10-012 Full Text: PD

Flow Characteristics through Granular Soil Influenced by Saline Water Intrusion: A Laboratory Investigation

The coastal geoenvironment initiates saline water intrusion into the freshwater aquifers, producing a geohydraulic problem. Such intrusion not only contaminates the fresh groundwater resources, making them unsuitable for human use, but also alters the hydraulic conductivity of the aquifer materials, which affects the coastal groundwater flow, influencing the water resources planning and management. Past investigations reveal that the groundwater flow can be linear or nonlinear depending upon the hydraulic gradient. Thus, the coefficients of nonlinear hydraulic conductivities are affected by saltwater intrusion. The present study focuses on an in-depth laboratory investigation into the influence of saltwater submergence on the nonlinear flow characteristics through granular soil. The fine sand samples have been submerged under saline water of specified concentrations for a specific duration, and the alteration in their nonlinear geohydraulic properties has been studied. It is observed that the flow characteristics through fine sand are significantly affected by the period of submergence and saline concentration. Appropriate analyses of the test results are performed to interpret the experimental data, and relevant conclusions are drawn therefrom. The novelty of this study is an in-depth analysis of nonlinear flow characterization affected by saline water intrusion. Doi: 10.28991/CEJ-2022-08-05-02 Full Text: PD