The ITB Unit Hydrograph Method: A Novel Approach to User-Defined Unit Hydrograph Development (Part II)

This paper is the second part of a comprehensive two-part series on the ITB Unit Hydrograph (ITB-UH) Method, titled The ITB Unit Hydrograph Method: A Novel Approach to User-Defined Unit Hydrograph Development. Building on the foundational concepts introduced in Part I, this paper delves into advanced applications of the ITB-UH Method, emphasizing its adaptability, calibration capabilities, and real-world utility. The ITB-UH Method introduces novel derivations for the Peak Rate Factor (Kp) and Peak Discharge (Qp), along with a time-step normalization approach that enables flexible adjustments to unit rainfall durations and a systematic calibration process. These innovations significantly enhance the method's versatility and accuracy in modeling flood discharge across diverse hydrological conditions. The practical applicability of the ITB-UH Method is demonstrated through real-world flood discharge calculations in the Pinamula River, located in Buol District, Central Sulawesi Province. Three illustrative examples highlight the method's versatility: (1) analyzing flood hydrographs at a 1-hour time step to showcase its practical applicability for flood management; (2) recalculating flood hydrographs with a finer 0.5-hour time step to demonstrate its adaptability to varying temporal resolutions; and (3) refining model parameters to improve alignment with observed flood hydrographs, underscoring the method's capacity for calibration and optimization. To evaluate the method's performance, robust metrics such as the Nash–Sutcliffe Efficiency (NSE), Percentage Bias (PBIAS), and Index of Agreement (IA) are employed. These metrics confirm the ITB-UH Method's accuracy and reliability, with results consistently aligning closely with observed data. Collectively, the findings underscore the ITB-UH Method's suitability across diverse hydrological settings and its potential to enhance both the verification of existing SUH methods and the development of user-defined hydrographs. By enabling more accurate and effective flood management, the ITB-UH method represents a significant advancement in hydrological modeling, with broad implications for water resource management and infrastructure planning worldwide. Doi: 10.28991/CEJ-2025-011-05-015 Full Text: PD

Interpretation Methods for Seismic Downhole Test in Inclined Boreholes

Geotechnical investigations often involve inclined boreholes, which can be used for downhole (DH) seismic surveys. However, as there is no interpretation method for downhole tests in inclined boreholes (IDH), this study proposes alternative interpretation methods based on the direct method (DM), interval method (IM), modified interval method (MIM), and refracted ray path method (RRM). We have named the proposed methods, adding an I to the original name to indicate that they are performed in an inclined well, i.e., DMI, IMI, MIMI, and RRMI. To analyze the applicability of the proposed methods, eight simple models with horizontal layers and four 2D models were used to obtain the P- and S-wave velocity profiles. Among all the proposed methods, the RRMI method showed the best fit between the calculated S-wave velocity (Vs) profile and the real models, providing good reliability. To test the equations and hypotheses, new interpretation steps were developed based on Snell's law and a modification of the numerical bisection method, which showed that the error increased slightly as the dip angle of the well decreased. The next step was to test the accuracy of the RRMI method in the field and develop downhole test processing software for vertical and inclined boreholes. Doi: 10.28991/CEJ-2023-09-10-016 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

Characteristic and Physicochemical Properties of Peat Soil Stabilized with Sodium Hydroxide (NaOH)

Peat in various phases of decomposition has poor shear strength and high compressive deformation. For this research study, it will focus on stabilizing peat soil using NaOH. There are two main tests that were conducted in this research study, which are index property testing and the compaction test. For index property testing, there were six (6) experiments conducted to study the index properties of disturbed peat soil, which are moisture content, fiber content, organic content, liquid limit, pH, and specific gravity. Then, for the compaction test, a 4.5kg rammer was used to determine the best mixture of stabilizer blended with different volumes of 5%, 7%, and 9% stabilizer. The desired outcome of this study is to stimulate further research into the use of the chemical NaOH as a peat soil stabilizer for improved soil usage. 7% and 9% of NaOH only have a slightly different percentage, and it can be concluded that this was the optimum percentage of NaOH as a chemical stabilizer for peat soil. It can be seen clearly that 5% is the higher dry density with a lesser moisture content of the peat. When the percentage of NaOH was increased, the graph pattern also changed. NaOH has been observed as an alteration agent for peat soil dry density. It can be seen clearly that 5% NaOH is the higher dry density of the peat with the lesser moisture content and is suitable as a peat soil stabilizer. The increment of oxygen content recorded changes from 13.3% to 23%, while the sodium (Na) content decreased significantly with the increment of oxygen (O). Sodium content decreased from 8.7% for untreated specimens to 4.5% and 5.5% when peat was treated with NaOH, with 5% of NaOH and 9% of NaOH. Doi: 10.28991/CEJ-2023-09-09-09 Full Text: PD

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

Short-, Medium-, and Long-Term Prediction of Carbon Dioxide Emissions using Wavelet-Enhanced Extreme Learning Machine

Carbon dioxide (CO2) is the main greenhouse gas responsible for global warming. Early prediction of CO2 is critical for developing strategies to mitigate the effects of climate change. A sophisticated version of the extreme learning machine (ELM), the wavelet enhanced extreme learning machine (W-EELM), is used to predict CO2 on different time scales (weekly, monthly, and yearly). Data were collected from the Mauna Loa Observatory station in Hawaii, which is ideal for global air sampling. Instead of the traditional method (singular value decomposition), a complete orthogonal decomposition (COD) was used to accurately calculate the weights of the ELM output layers. Another contribution of this study is the removal of noise from the input signal using the wavelet transform technique. The results of the W-EELM model are compared with the results of the classical ELM. Various statistical metrics are used to evaluate the models, and the comparative figures confirm the superiority of the applied models over the ELM model. The proposed W-EELM model proves to be a robust and applicable computer-based technology for modeling CO2concentrations, which contributes to the fundamental knowledge of the environmental engineering perspective. Doi: 10.28991/CEJ-2023-09-04-04 Full Text: PD

AI Mix Design of Fly Ash Admixed Concrete Based on Mechanical and Environmental Impact Considerations

It has become very important in the field of concrete technology to develop intelligent models to reduce overdependence on laboratory studies prior to concrete infrastructure designs. In order to achieve this, a database representing the global behavior and performance of concrete mixes is collected and prepared for use. In this research work, an extensive literature search was used to collect 112 concrete mixes corresponding to fly ash and binder ratios (FA/B), coarse aggregate and binder ratios (CAg/B), fine aggregate and binder ratios (FAg/B), 28-day concrete compressive strength (Fc28), and the environmental impact point (P) estimated as a life cycle assessment of greenhouse gas emissions from fly ash- and cement-based concrete. Statistical analysis, linear regression (LNR), and artificial intelligence (AI) studies were conducted on the collected database. The material binder ratios were deployed as input variables to predict Fc28 and P as the response variables. From the collected concrete mix data, it was observed that mixes with a higher cement content produce higher compressive strengths and a higher carbon footprint impact compared to mixes with a lower amount of FA. The results of the LNR and AI modeling showed that LNR performed lower than the AI techniques, with an R2(SSE) of 48.1% (26.5) for Fc and 91.2% (7.9) for P. But ANN, with performance indices of 95.5% (9.4) and 99.1% (2.6) for Fc and P, respectively, outclassed EPR with 90.3% (13.9) and 97.7% (4.2) performance indices for Fc and P, respectively. Taylor's and variance diagrams were also used to study the behavior of the models for Fc28 and P compared to the measured values. The results show that the ANN and EPR models for Fc28 lie within the RMSE envelop of less than 0.5% and a standard deviation of between 15 MPa and 20 MPa, while the coefficient of determination sector lies between 95% and 99% except for LNR, which lies in the region of less than 80%. In the case of the P models, all the predicted models lie within the RMSE envelop of between 0.5% and 1.0%, a coefficient of determination sector of 95% and above, and a standard deviation between 2.0 and 3.0 points of impact. The variance between measured and modeled values shows that ANN has the best distribution, which agrees with the performance accuracy and fits. Lastly, the ANN learning ability was used to develop a mix design tool used to design sustainable concrete Fc28 based on environmental impact considerations. Doi: 10.28991/CEJ-SP2023-09-03 Full Text: PD

Seepage Analysis and Optimization of Reservoir Earthen Embankment with Double Textured HDPE Geo-Membrane Barrier

This research paper focuses on conducting a steady state seepage analysis along with the downstream slope factor of safety using the Modified Bishops method in a poorly compacted earthen embankment and optimizing the same reservoir earthen embankment in a case study located near Sadiyavav village in Junagadh district in Gujarat, India. The study site, situated at 21°32'06.5"N and 70°37'26.7"E, is renowned for its Asiatic lions. The analysis and optimization were performed with a double-textured High-Density Polyethylene (HDPE) Geo-membrane barrier. Previously, designs and numerical solutions proposed homogenous embankments and too poorly compacted with no drainage arrangements, which led to anisotropic conditions within the section and water seeping out, cutting the phreatic line. The paper presents the documented improvements in the factor of safety achieved through the seepage analysis and the optimization of the HDPE Geo-membrane barrier. Two improvement techniques were studied using the “Limiting Equilibrium-Finite Element Method” (LS-FEM). The first using (HDPE) Geo-membrane stabilized with gabions, and the second alternative using HDPE Geo-membrane with gabions in addition to rock toe. The study results showed improvements in the downstream slope stability for the two alternatives by 3% and 10%, respectively. Doi: 10.28991/CEJ-2023-09-11-07 Full Text: PD

A Review of Advances in Peat Soil Stabilisation Technology: Exploring the Potential of Palm Oil Fuel Ash Geopolymer as a Soil Stabiliser Material

This study aims to highlight the latest developments in the field of peat soil stabilisation technology via chemical stabilisation. The review examines the use of traditional stabilisers such as OPC and various non-traditional stabiliser materials, i.e., Palm Oil Fuel Ash (POFA)-OPC blends, chemical solutions, and geopolymer materials, to enhance the Unconfined Compressive Strength (UCS) characteristics of peat soils based on the ASTM D 4609 requirements. OPC, POFA-OPC blends, and alkaline solutions mostly produced stabilised soil samples that fell short of the ASTM requirements. Existing studies on the use of waste-derived geopolymers to treat peat soils are limited, while the use of POFA geopolymer materials has mostly focused on the improvement of clayey and silty soils. The results of soil stabilisation with geopolymer were very encouraging, as the strength gains were in line with the ASTM soil strength requirements. As a result of this review, it can be concluded that POFA geopolymer is a viable soil stabiliser material with the addition of Ground Granulated Blast Furnace Slag, and that the use of POFA-GGBFS geopolymer to enhance the strength properties of peat soils should be investigated. Doi: 10.28991/CEJ-2023-09-08-017 Full Text: PD

Utilization of Bitumen Modified with Pet Bottles as an Alternative Binder for the Production of Paving Blocks

This study considers the utilization of bitumen modified with molten polyethylene terephthalate (PET) waste bottles as an alternative binder in paving blocks. PET waste was used at 2, 4, 6, 8, and 10% to modify bitumen in the production of paving blocks. Compressive strength test and skid resistance test were conducted on the paving block samples to evaluate their mechanical strength properties, while water absorption and the Cantabro abrasion tests were carried out to ascertain the durability of the paving block samples. The PET-modified bitumen paving blocks (PMBPB) have enhanced compressive strength and skid resistance compared to unmodified bitumen paving blocks. Also, a significant reduction in water absorption rate of up to 56% was achieved in PET-modified bitumen paving blocks (PMBPB) compared to the unmodified sample. The abrasion loss in the PMBCB samples was the least compared to that in normal cement paving blocks and unmodified bitumen paving blocks. The maximum compressive strength and least water absorption for the PET-modified bitumen concrete paving blocks were obtained at a 10% PET replacement level. It can be concluded that enhanced compressive strength and durability in cement paving blocks and unmodified bitumen paving blocks could be achieved with the use of PET modified bitumen in concrete paving block production, and this will also encourage PET waste recycling and contribute meaningfully to sustainability in concrete paving block production. Doi: 10.28991/CEJ-2023-09-01-08 Full Text: PD