Browsing by Author "Kaya, Zulkuf"

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Sustainable Stabilization of Peat Soil with Hybrid Geopolymer Jet Grout Columns
(Springer Int Publ A.G., 2025) Yalcin, Hakan; Erol, Aykut; Kaya, Zulkuf; Cadir, Cenk Cuma; Uncuoglu, Erdal; Akin, Muge K.
Peat soils present severe challenges in geotechnical engineering due to their low shear strength, high water content, and aggressive chemical environments such as sulfate exposure. While cement-based jet grouting (JG) is widely used, it entails high carbon emissions and energy consumption. Hybrid geopolymer jet grout columns (HGJGCs) are presented in this work as a viable and sustainable alternative. Unlike conventional geopolymer studies that rely on pre-cured molds later exposed to aggressive environments, this research simulates realistic field conditions by injecting fresh geopolymer directly into sulfate-rich peat, where early-age durability and strength are critical. To address early strength limitations commonly seen in aggressive situations, a tiny amount of cement was added to the fly ash/GGBFS-based combination. Crucially, there is no need for high heat because the mechanism cures at room temperature. Physical model testing, laboratory-scale jet grouting, and performance comparisons with conventional JGCs were all carried out. Results show that HGJGCs increased the bearing capacity of peat by 5.5 times, improved compressive strength (5.3-5.7 MPa), and reduced settlement more effectively than JGCs. Additionally, CO2 emissions were reduced by 25.14% due to lower binder-related emissions and energy demand. This work shows that hybrid geopolymer systems are a viable, low-carbon substitute for peat stabilization because they can function well in real-world, chemically demanding situations.
Citation - WoS: 3
Citation - Scopus: 3
Experimental Investigation of Soil Disturbance Effect on Bearing Capacity of Organic Soil
(Springer int Publ Ag, 2024) Cadir, Cenk Cuma; Kaya, Zulkuf; Yalcin, Hakan; Erol, Aykut; Uncuoglu, Erdal; Akin, Muge
The model test investigations on the soft soils are usually carried out on samples prepared in the laboratory and assuming site conditions. However, such soils that are prepared in the laboratory only partially reflect the site conditions. Considering this gap in the literature, this study mainly focuses on the bearing capacity and settlement behavior of the undisturbed organic soil obtained by a novel block sampling technique. The disturbed organic soil prepared in the laboratory was investigated with large-scale model experiments for two different footing types (square and rectangular). Vane Shear testing (VST), Dynamic Cone Penetration (DCP) tests, and finite-element analysis (FEA) were performed. The average bearing capacity values of disturbed and undisturbed soil were 60.98 kPa-68.71 kPa and 108.18 kPa-110.89 kPa for square and strip footings, respectively. Bearing capacity reductions of up to 40% were determined on laboratory-prepared soils. The cone reached the required depth (450 mm) with three blows for disturbed soil, while it was reached with four blows for undisturbed soil. Likewise, the undrained shear strength obtained by the VST was determined as 22.16 kPa and 16.60 kPa for undisturbed and disturbed soils, respectively. Shear strength losses of up to 25% for disturbed soils were observed. The bearing capacity values obtained from FEA were comparable to those obtained with the model tests. It was concluded that the degree of degradation of organic soils in the laboratory significantly affects the bearing capacity of the soil.
Citation - WoS: 6
Citation - Scopus: 7
Improvement of an Undisturbed Peat Soil With Jet Grout Columns: Physical and Numerical Modeling
(Springer Heidelberg, 2023) Yalcin, Hakan; Kaya, Zulkuf; Cadir, Cenk Cuma; Uncuoglu, Erdal; Erol, Aykut; Akin, Muge
The bearing capacity of the composite-formed soil, such as grouted peat soil, is a crucial design parameter that can be improved by employing jet grout columns (JGCs). The coupling effect of the requirement of new industrial sites and reduction in the suitable regions for construction requires research on improving the bearing capacity of abundantly available peat soils. Despite routinely reported studies on peat soil, improvement studies basically took upon the disturbed soil samples. Research on the sample collecting techniques or experiments on undisturbed peat soil has not been conducted intensively. This study uses a domestic jet grout device to compare features of the undisturbed peat soils at the laboratory using axial loading tests. While samples were collected undisturbedly using specially designed steel boxes, the peat soil within the steel boxes was improved by jet grout columns. Additionally, PLAXIS 3D simulations were used to estimate the behavior of the improved soil. Results showed that the bearing capacity of the soil increased 4 times for square foundations (2 x 2 JGC) and 4.5 times for strip foundations (3 x 1 JGC) compared to the unimproved organic soil.