Settlement Behavior Evaluation of Soft-Clay Layer Reinforced with Sand Piles

In this study, the performances of the sand piles in Istanbul's Bağcılar and Zeytinburnu districts has been analyzed using Finite Element Method (FEM). Single and group (triple) piles with various length/diameter ratios (L/D) were placed in the water-saturated soft clay soil. Sand piles were modeled in various L/D ratios (10, 5.71, and 8.57). The distance between the piles was chosen as 2 meters and the group effect was also investigated. A uniformly distributed load of 162 kN/m2 is placed on the ground. In addition, the soil was modeled with the Soft-Soil soil model, the hardening soil model for the infill part, and the sand piles with the Mohr-Coulomb soil model. According to the results , the settlement of the soil decreases by 52.8% for a single pile with an L/D ratio of 8.57. However, the best L/D ratio for triple piles was found to be 5.71. In this case, the settlement decreases by 52.8% compared to the pileless situation. Finally it was concluded that the model with the L/D ratio of 8.57 reduced settlement in the best and the most efficient way.

Evaluation of p-y Curves for Group Piles in Cohesive Soil Based on 3D Numerical Analysis

The pile foundation supported on a structure can generate large horizontal loads due to earthquakes, high winds, and wave actions. The behavior of piles when subjected to horizontal load is generally analyzed using the p-y curve and “p-multiplier (Pm),” which is the coefficient of the group pile effect. In this study, the p-y curves and Pm were calculated by analyzing a single pile and group of piles arranged in 3 × 3 installed in cohesive soil using the finite element analysis program, Plaxis 3D. The soil resistance (p) increased as the undrained shear strength of the clay increased and the distance between the pile centers (S/D) increased. In the case of the group pile effect, when Pm was closer to the center of the group pile, the distance between the pile centers was smaller, and Pm was less due to the interference effect of the adjacent individual piles. In conclusion, it was observed that Pm is affected by the location of the individual piles and the distance between the pile centers.

Determining the depth of plugging a pile with one layer of struts or anchors

The aim of the proposed work is to develop a simplified version of determining the depth of plugging a pile with one layer of struts or anchors. When setting the problem, the scheme by E.K. Jacobi was offered, which suggests, that the deepening of the wall should be such as to ensure the stability of the wall against soil protrusion. Methodologically, the problem is solved analytically. The calculations take into account the active and passive soil pressures, the intensity and shape of whose plots is determined using Coulomb's theory. Comparative results of the depth of pile plugging obtained by the simplified method and the method currently used in the calculations of single pile fences with one layer of fasteners are presented. It is shown that the depth of pile plugging and groove calculation made in a simplified way does not practically differ from the depth of wall immersion calculated by the existing method.

A field study on the load sharing behavior of a micropiled-raft underpinned by a waveform micropile

A waveform microiple(WMP) uses jet grouting method to generate shear keys along the pile shaft for improving the shaft resistance and cost efficiency. In this study,field loading tests were performed in this study to characterize the load sharing behavior upon inclusion of a waveform micropile (WMP) in a group of four micropiled-raft. First, single-pile compressive loading tests were conducted on three WMPs and five Type A micropiles (MP). Subsequently, a group-pile loading test was performed on a piled raft comprising 2 × 2 MPs and a central WMP. The load–settlements, axial stiffnesses, and load transfer mechanisms of individual MPs were analyzed during the tests, including the short- and long-term effects of the axial stiffnesses of the MPs on the load sharing ratio of the micropiled-raft. The single-pile loading test results revealed that the shear keys along the WMPs caused its bearing capacities and axial stiffnesses to be 1.5 times and 2–5 times higher than those of MPs, respectively. In the micropiled-raft loading test, the load sharing ratios of the MPs increased with their axial stiffnesses, and the highest load sharing capacity was exhibited by the WMP, which constituted 30% of the total load and 2–3 times that of MPs. Moreover, the influence of raft on the load-sharing capacity should be considered as well.