This study examined the efficacy of Fly Ash Type F-based geopolymer binders in enhancing the impermeability of clayey soils. A clayey soil of the CL type was stabilized using geopolymer mixtures composed of fly ash activated by two different alkaline systems: (1) sodium silicate combined with lime and (2) sodium bicarbonate combined with lime. The FA binders were added at dosages of 10%, 20%, and 30% by weight of dry soil, and FA/AA was 0.2, 0.4, and 0.6. Standard falling head permeability tests were performed to evaluate the efficacy of the therapies. The experimen results indicated a marked improvement in reducing soil permeability with both alkaline activator systems. The greatest reduction was observed at a 30% replacement ratio when the sodium silicate–lime mixture was used. Beyond this level, a slight increase in permeability was recorded, which can be attributed to the excessive alkalinity of the mixture and the potential formation of microcracks. On the other hand, the sodium bicarbonate–lime system showed a consistent trend, where higher replacement levels continued to lower permeability. Overall, the study highlights that fly ash–based geopolymers, when properly optimized in terms of activator type and dosage, provide an effective and sustainable approach for improving the impermeability of clayey soils, particularly in hydraulic and geotechnical engineering applications
The evaluation of undrained shear strength (Su) in fine-grained soils is crucial for geotechnical engineering applications. This study aims to assess Su in fine-grained soils through laboratory testing and data analysis by different equations Su Undrained shear strength from field and Based on SPT-N Values. The introduction provides an overview of the importance of Su in geotechnical engineering and highlights the complexity of estimating Su in fine-grained soils. The material and methods section describes the collection of soil samples from Fallujah, which predominantly consist of silty clay and clayey silt. Field investigations were conducted to obtain Su measurements using field vane shear tests. The section also provides details on the field-testing data, including borehole depth, SPT results, consistency, Su, Su from SPT NOVO, and soil description. The laboratory testing and data analysis section presents the results of laboratory shear testing conducted on the collected soil samples. The testing involved determining the undrained shear strength of the soils using appropriate testing apparatus and procedures. The data obtained from the laboratory testing are analyzed to identify trends in Su and soil consistency. Based on the analysis of the data and the results obtained from the laboratory testing, it can be concluded that there is a relatively weak correlation between the undrained shear strength (Su) and the Standard Penetration Test (SPT) N-value. The correlations proposed by Sowers (1979), Kulhawy and Mayne (1990), Reese, Touma, and O'Neill (1976), and Terzaghi and Peck (1967) all show modest R2 values, indicating limited correlation between Su and N-value
ABSTRACTStudies in geotechnical engineering have the nonlinear behavior of soils. An experimental study was carried out on models of piled rafts, and four piles with a diameter of 25 mm and a length of (300, 400, and 500) mm were taken, with a raft of (180x180) mm, and compared with the piled-raft system of 180 × 180 raft and nine piles of 19 mm and 500 mm in diameter and length respectively. They were tested for raft resistance, number of piles, length, and diameter while maintaining the spacing between piles. Test results showed the raft performance improved by 76% when adding piles. The increase in the (L/D) ratio for variable (L) length leads to an increase in pile share of 87% for the groups (2×2). Also, pile share was increased by 10% with a decrease in the diameter of piles and an increase in the number of piles in the group. Therefore, the increment in each pile’s skin friction results in an increase in the bearing capacity of each pile.