In this study, the usability of construction and demolition waste (CDW) aggregates as filling when stabilized with alkaline activator solution (AAS) and blast furnace slag (BFS) was investigated. The initial stage of this study involved determining the engineering properties of CDW by laboratory experiments. In the next stage, modified Proctor tests were performed to investigate the compaction behavior of CDW, to which 5% to 30% BFS was added with water or AAS. In the following stage, California bearing ratio experiments were performed to determine the mixture specimen with the highest strength. In the final stage, a weak soil layer was created in a test tank, and fillings of different thicknesses were built on it using CDW with and without additives in the determined optimum mixing ratio. Then, plate-loading tests were conducted using a model foundation to evaluate the load–deformation behavior of the fillings. The study’s results indicated that adding BFS with water or AAS to CDW increased strength. Furthermore, the addition of 20% BFS yielded the highest strength value, and the CDW aggregates with the added BFS increased the ultimate bearing capacity by up to 4.72 times compared to those without the additive.

Estimating a pile shaft’s frictional capacity is challenging and has been a controversial subject among researchers. In this study, the shaft friction resistance of non-displacement (pre-installed) model piles under axial load was investigated. Four different model piles were used, including steel, timber, and two composite piles (FRP and PVC filled with concrete). The angle of interface friction (δ) between test sand, and pile materials was determined using an interface shear test (IST) at four relative densities. Axial pile load experiments were implemented in a soil tank and piles were embedded into loose to very dense sand. Model pile load tests were performed in such a way that there was no end (point) bearing capacity (only friction was generated), and lateral friction resistance between the pile material and the soil along the pile shaft formed the complete bearing capacity of the model pile. According to experimental results, it was observed that, with increasing sand relative density and surface roughness of the pile material, the shaft friction resistance of the model pile increases. A back-calculation analysis was also performed to find the values of lateral earth pressure coefficient (K) using Burland’s (1973) equation with the help of measured shaft friction capacity of the model pile load test. By performing multivariate regression analysis, an equation was obtained between the back-calculated lateral earth pressure coefficient (K) and other parameters. The obtained equation was used to calculate the K values given in other studies in the literature. It was determined that the obtained equation was in good agreement with the data in other studies. This equation can be beneficial in practice and can be advantageous for further study in the future.

Since construction and demolition waste (CDW) contain materials such as gypsum, wood, brick, plaster, etc., its engineering properties may not be at the desired quality. Therefore, if CDW is to be recycled and reused, the properties of CDW may need to be improved by various methods. In this study, the modifications in compaction and strength properties of CDW obtained from demolished building were investigated by adding fly ash (FA) at certain ratios. For this purpose, modified proctor, unconfined compression strength and California bearing ratio (CBR) tests were conducted on the CDW with and without FA-added. As a result of the experimental studies, it was observed that the addition of alkaline activator solution (AA) to the CDW increased the strength of the CDW. In addition, the strength of CDW increased significantly with the usage of AA in FA-added CDW samples. The FA additive ratio that gave the highest strength in the tests with water and AA was found to be 5% and 15%, respectively. As a result of the study, it is predicted that CDW with FA and AA can be used as a filling material as an alternative to natural aggregate.

In this study, the presence of a foundation near the sheet pile wall built on sand soil was simulated in the laboratory, similar to the field conditions. For this purpose, laboratory tests of sheet pile wall (SPW) (defo) and bearing capacity (q_ult) of the foundation were carried out by applying vertical loads to the steel model foundation. Besides, laboratory tests were represented by the Mohr‐Coulomb material model under 3D plane deformation conditions, and numerical analyses were performed. These studies were performed by varying the distance among the SPW, the foundation (L), and the penetration depth of SPW (Hp). The results demonstrated that L had a greater effect on q_ult and δmax than the H_p. When L was kept constant and H_p was increased, it was seen that q_ult increased and δmax decreased. Moreover, the raise in L has resulted in an increment in the qult and δmax decreased. In addition, a good agreement between numerical analysis and experimental test was observed.

Historical masonry structures are very important as they carry cultural heritage, so it is important to protect these structures from natural disasters such as earthquakes and transferred to the next generations. It is known that masonry structures are weak against earthquakes, therefore, a suitable analysis method for assessment and retrofitting purposes is a must. Generally, the fixed-base concept is used for analysis and design purposes, however, in reality, the structures are not fixed-base but they are resting on soils. The aim of this study is to make a comparison study between dynamic responses of fixed-base and soil-structure interaction (SSI) models for bridge masonry structures, the historical Dalal bridge was selected as the case study. First, the bridge was modeled as a fixed base model, and then three different soil profiles (hard, medium and soft soils) were added to the underneath of the structure. The numerical models were analyzed under Elcentro earthquake record. Results indicating a good agreement between the fixed base and the case of hard soil base. However, considerable differences were observed for medium and soft soil profiles.