The Performance of Taper Helical Pile Embedded in Loose Sand Under Uplift Static and Cyclic Load Using 3D-Finite Element Analysis

Piles with helices are a kind of foundation that is capable of withstanding compression, tension, and lateral loads. However, for almost 25 years, this kind of Pile was widely used across the world. Its behaviour is unpredictable and terrifying, especially in Iraq. The present study analysed this kind of Pile using the finite element method. It was recommended that the helical pile geometry be modeled by numerical model technique and the computer program Plaxis 3D. The plaxis 3D software is a well-known geotechnical engineering tool that numerically analyses soil and simulates experimental work in terms of curve matching and outcomes. Furthermore, an analysis of variables was conducted. The primary variable research investigates the influence of the number of helices and the tapered helix distance under static and cyclic load. The final finding is that the more helices in a pile, the smaller the displacement (or amplitude) in comparison to one helix under the effect of uplift static and cyclic load. As a result that the effect of helix number on soil behaviour is more than the effect of changing the distances between helix.

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.

Nghiên cứu sự phân bố tải trọng trong quá trình làm việc của móng bè cọc

Móng bè cọc ngày càng được áp dụng rộng rãi, đặc biệt là cho các tòa nhà cao tầng. Trong móng bè cọc, cọc không được thiết kế để chịu toàn bộ tải trọng mà chỉ để giảm độ lún đến một mức độ cho phép. Bài báo này trình bày nghiên cứu sử dụng kết hợp với phương pháp phần tử hữu hạn để thiết kế móng bè cọc. Kết quả nghiên cức chỉ ra rằng: phương pháp móng bè cọc như là một phương án móng thay thế. Phân tích phần mềm Plaxis 3D để xác định độ lún và hệ số phân bố tải trọng trong móng bè cọc.

Consolidation in Soft Soil – Case Study on Prefabricated Vertical Drains (PVDs)

Background: Constructing on soft ground is one of the challenges of geotechnical engineering. The unpredictable behaviour and characteristics of soft soil can cause much damage resulting in high maintenance costs in the post-construction phase. Objective: The purpose of this study is to analyse the consolidation process and ground improvement method using surcharge and a prefabricated vertical drain by measuring the accuracy of the prediction settlement value with the actual site settlement results. Methods: An effective ground improvement method is the application of a surcharge and prefabricated vertical drains (PVDs). Various methods can be used to predict the settlement effectively, one such method being PLAXIS 3D simulation. A case study on ground improvement works was selected for this research, where PVDs were constructed and implemented at the site. A few undisturbed samples were collected from the site to generate the parameters based on the lab test conducted in the simulation process. This parameter was carefully studied and representing the principal input for the 3D model, which is generated and represents the actual ground improvement method for the selected case study. The analysis was performed using a borehole and soft soil model to generate the diagram. The prediction settlement value was generated from the PLAXIS 3D analysis as the baseline comparing to the actual results. The factors that influence the settlement value, such as the length and spacing of the prefabricated vertical drain, construction method, and soil characteristics, are also discussed. Results: A predicted settlement of 2553 mm was generated by the simulation, while the actual settlement outcome at the site was 2096 mm, a difference of 457 mm, and a prediction accuracy of 82.1%. Conclusion: The study found that the combination of surcharge and prefabricated vertical drain in the ground improvement worked well. Also, discussed were the factors that influenced the accuracy of the prediction and the site results.

Effect of groundwater on the displacements of axially loaded pile in clayey soil

The displacement of a loaded pile could be vertical (axial) or horizontal (lateral); these displacements are sensitive to groundwater presence within the soil mass. This paper presents a theoretical study to investigate vertical and horizontal displacement of piles embedded in a clayey soil for different levels of groundwater under the ground surface. The study was performed using the commercial finite element package PLAXIS-3D. Three diameters of the concrete piles were considered: 0.5, 0.75 and 1 m, and were subjected to 1,000 kN axial load. The effect of 0, 5, 10, 15 and 20 m groundwater along the 20 m pile in length from the ground surface on the vertical and horizontal displacements was investigated. The results indicated that the vertical and horizontal displacements increase when the ground water level increases towards the base of pile. Also, there is a significant increase in the horizontal displacement up to 15 m of groundwater level from ground surface and decreased at levels from 15 to 20 m.

INVESTIGATING THE BEHAVIOR OF PILED RAFT FOUNDATION IN CORE WALL FOUNDATION OF HIGH-RISE BUILDINGS

Core structure is an indispensable part of high buildings. Normally, the foundation of the core structure has a raft of larger size than the other foundations in the same project; therefore, the foundation of the core structure can be viewed as a small piled raft foundation. Currently, when calculating the piled foundation of the core, it is mostly assumed that the piles system will bear all the project loads. But this calculation method is not suitable for the actual constructions as well as does not make full use of the bearing capacity of the structure and the ground, leading to using more materials and causing more waste. Core structure aims to increase both stiffness and horizontal load capacity in high-rise buildings, so the moment inside the core transmitted to the foundation is very large. One of the shortcomings of the Plaxis 3D Foundation software is its inability to declare the moment affecting on the foundation due to the loads in this program just includes distributed loads, line loads and point loads in the geometry model. Consequently, when using Plaxis 3D Foundation software to calculate the core wall foundation of high-rise buildings, this moment is converted into an equivalent pair of moments. The research shows that when the core foundation of a high-rise building is placed on soft soil, the pile carries 96%, most of the load transmitted to the foundation. However, when the foundation is placed on hard soil, the soil surrounding the raft will bear about 10% of the load transmitted to the foundation. If this matter is skipped, there will be a large error in calculation and design

Stress-strein state of weak and filled soils reinforced with reinforced concrete and soil piles, respectively

Introduction. The overwhelming majority of construction areas are characterized by difficult engineering and geological conditions, represented by the presence of weak soils at the base. There are construction sites on which a large thickness of fill soil is observed. In these conditions, designers apply: soil consolidation, soil reinforcement, significant deepening of the underground part of buildings, etc. This article presents the formulation and solution of the problems of interaction of reinforced concrete piles with weak soils, as well as the interaction of soil piles with bulk soils as part of a pile-slab foundation, which allow one to determine the reduced deformation modulus and the bedding value. Materials and methods. To describe the change in shear stresses depending on depth, a law was adopted in the form τ(z)=τ0е–αz. The solution is presented by analytical and numerical methods. The results obtained were compared by the analytical solution of the problem with the results obtained in the PLAXIS 3D software package. Results. Regularities of the distribution of the total load on the pile-slab foundation between the pile field and the grillage have been obtained. The analytical solutions in the article are supported by the graphical part, performed using the Mathcad program. Numerical simulation of the problem was carried out in the PLAXIS 3D software package. The dependence of the settlement on the load, calculated by analytical and numerical methods, is shown. An expression is obtained for defining the stresses in different sections of the pile shaft and under the grillage slab. The theoretical and practical aspects of the construction of crushed stone piles are considered. The theoretical substantiation of compaction of bulk soils with crushed stone piles using a special technology is given. A dependence is obtained for determining the reduced modulus of deformation for bulk soil mass reinforced with soil piles. Conclusions. Comparative evaluation of the results of solutions obtained by analytical and numerical methods showed good convergence. The solutions obtained can be used to preliminary determination of the settlement of piles as part of a pile-slab foundation. Selection of the optimal ratio of the pile length and its diameter allows the most effective use of the bearing capacity of the pile. For bulk soils, reinforced with soil piles, it is possible to select the optimal reduced modulus of deformation by varying the pitch of the soil piles.

Analisis Penurunan Tanah dengan Plaxis 2D dan 3D Pada Proyek Reklamasi Belawan

Penurunan tanah adalah masalah yang sering ditemukan pada konstruksi diatas tanah lunak selain pergerakan tanah dan pergeseran tanah. Tanah dengan konsistensi lunak dan memiliki permeabilitas rendah akan lambat mengalirkan air pori dalam tanah sehingga diperlukan penanganan khusus untuk mempercepat prosesnya. Salah satu metode untuk mempercepat proses pengaliran air pori pada tanah dasar yaitu dengan memberikan beban Preloading dan pemancang PVD (Pre-fabricated Vertical Drain). PVD mampu mempercepat keluarnya air pori tanah sehingga proses konsolidasi bisa berlangsung lebih cepat. Data harian penurunan tanah yang terjadi di lapangan dicatat dari settlement plate yang dipasang di lapangan. Analisis ini bertujuan untuk mengetahui perbandingan antara penurunan tanah yang dihitung menggunakan program Plaxis 2D dan 3D dibandingkan dengan penurunan yang tercatat pada settlement plate. Analisis menunjukkan bahwa besar penurunan yang terjadi pada Plaxis 2D adalah 6,47 meter dan dari analisis Plaxis 3D adalah 6,356 meter. Penurunan yang terjadi menurut pengamatan settlement plate di lapangan adalah 6,32 meter. Dapat disimpulkan bahwa analisis dengan menggunakan Plaxis 3D lebih mendekati penurunan hasil observasi dibandingkan dengan menggunakan Plaxis 2D.