Waseim Azzam

1. The early 1950s marked the initial emergence of the concept of micropile-distinct technologies in Italy (Moon and Lee 2016). Micropiles are deeply embedded elements that require drilling and gro...

Pile foundations used in marine and onshore structures are often exposed to repeated axial loading, which can reduce their capacity and increase settlement over time. To address this issue, this study aims to evaluate the performance of rocket piles in sand and to understand how modifying pile geometry can enhance axial capacity under both static and quasi-static cyclic loading. A series of 1-g physical model tests were carried out to investigate the influence of sand relative density, pile slenderness ratio (L/D), fin-length ratio (Lf/L), fin-width ratio (b/D), fin location along the shaft, and surface roughness (Ra) on load–settlement behavior. The experimental results show that adding fins to the pile shaft significantly increases ultimate load capacity and reduces settlement compared to conventional smooth piles. The improvement is particularly noticeable under quasi-static cyclic loading, where fins help mobilize greater shaft resistance and limit the accumulation of settlement. Furthermore, larger fin-width and fin-length ratios provide greater performance enhancement. The main contribution of this study is the experimental evaluation of rocket piles under cyclic conditions and the development of practical design charts that allow engineers to estimate load improvement and settlement reduction based on fin geometry and surface characteristics, offering a more economical and efficient foundation solution in sandy soils.

Expansive soils are clayey soils that undergo significant volume changes due to moisture content variations which can severely affect the stability of foundations and infrastructure. This study investigates the use of talcum powder as a novel stabilizing additive to reduce the swelling potential of expansive soils with particular focus on the behavior of the treated soil under curing conditions. Talcum powder concentrations of 5%, 10%, 15%, 20% and 25% by dry weight of soil was considered. A comprehensive series of laboratory tests were conducted, including swelling pressure, Atterberg limits, modified Proctor compaction and unconfined compressive strength at 4 curing times: 0 days, 7 days, 14 days and 28 days. In addition, mineralogical and microstructural analyses were carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Experimental results revealed that incorporating talcum powder at a content of 25% by dry weight effectively reduced the swelling pressure by 37.5%. The compression index decreases with the increase in the talcum powder content. The results highlight the material’s significant capability to enhance the engineering properties of expansive soils, particularly under curing conditions and offer a cost-effective and readily available solution for soil stabilization applications.

This research investigates the effectiveness of cross-sectional modification in piles as an advanced deep foundation technique for clay soils. Conventional circular piles often underperform under compressive loads due to their limited surface area and geometry. To address this limitation, this study proposes the use of X-section cast-in-place concrete (XCC) piles, designed to improve compressive strength compared to traditional circular piles. The behaviour of XCC piles under compression in clay soil was analysed using PLAXIS 3D V20 software. A series of numerical models were run at different XCC pile geometry and length in clay soil with different cohesion. Numerical results indicate that at an Lp/Dp ratio of 16 and θ° = 120°, the bearing capacity of XCC piles increased by 1.4 times compared to conventional piles with the same cross-sectional area and clay cohesion values of 70 KN/m², 100 KN/m², and 150 KN/m². Furthermore, XCC piles demonstrated a twofold increase in vertical load-carrying capacity compared to conventional piles. These findings highlight the enhanced performance of XCC piles, attributed to their optimized cross-sectional geometry, which maximizes soil-pile interaction. Therefore, XCC piles represent a promising solution for improving compressive resistance in clay conditions.

A series of three–dimensional finite – element models (PLAXIS 3D V20) were developed to investigate the non-linear behavior of XCC section piles under torsional load in clay soil with various soil cohesion states. Piles were assumed to behave in a linear elastic model, while the soil was modeled using the non-linear (HSM) hardening soil model. The influence of pile length to pile diameter ratio (L_p/D_p), 0pen arc spacing to pile diameter ratio (a_p/D_p), and open arc degrees(θ˚) were explored. the numerical results showed that the torsional capacity of the pile increases with the increase of clay cohesion. At the ratio of pile length to pile diameter (L_p/D_p) = 15, and the ratio of the open arc spacing to pile diameter (a_p/D_p) = 0.14, open arc degrees(θ˚) = 90 the efficiency of improvement in the torsional capacity reached to 3.96, 5.06, and 5.71 times of torsional capacity of conventional pile with the same cross-sectional area at clay cohesions of 70 KN/m², 40 KN/m², and 30 KN/m², respectively. furthermore, the torsional capacity of the XCC section pile increases with the increase in soil cohesion (C_u), pile diameter (D_p), pile length (L_p), and open arc spacing. but it decreases with the increase of open arc degrees(θ˚). The change of shape to XCC shape can significantly increase the earth pressure and skin friction around the pile by creating a passive zone, and increasing the perimeter.