PLAXIS 2D Research Articles

Influence of Ali Al -Gharbi Earthquake on Braced Excavation in Silty Clay Soil (Numerical Study)

The design of the braced excavation system is one of the important and necessary matters for the implementation of various projects. The braced excavation system is used to support excavations in temporary projects, so there are shortcomings in the study of this aspect, although sometimes there are many projects that take long periods of time especially the projects of underground tunnels and high buildings. This was the main reason for the study. Therefore, the possibility of exposing the drilling system to earthquakes is great, especially in seismically active areas. If the drilling system is exposed to an earthquake, it can cause great human and material losses, so it must be designed against earthquakes so that ensure complete collapse and failure does not occur. This study aims to investigate the behavior of braced excavations under the influence of the Ali Al-Gharbi earthquake in both x- and y- directions. A numerical study is carried out on braced excavation system of (14×6) m and depth 9m using software Plaxis 3D. The braced excavation system consists of three type of bracing system with three levels of strut and wales connected with sheet pile wall to support sides of excavation and prevent them from collapsing. The results of study showed that the horizontal displacement of braced excavation system is (100-155) % more than vertical displacement (settlement) with seismic time when system is subjected to Ali Al-Gharbi earthquake in both directions with the other factors remaining constant. The stiffness of sheet pile wall also play an important role increases and decreases lateral displacement in both direction. Also, the results showed that the movement of of braced excavation system depends on several factors like as type of soil, time acceleration and the direction of earthquake. Settlement of Ali Al-Gharbi earthquake in Y- direction is 13% more than in X-direction.

Influence of foundation pit excavation on the internal force of adjacent shield segment structure

As subway line density increases, excavation of foundation pits around tunnels unavoidably triggers soil disturbance. This consequently alters the on-site strain and distortion fields of the soil, resulting in internal force modifications in the tunnel shield segment and joint failure. To maintain tunnelling structure safety through numerous foundation pit diggings, this study uses a real-world project as its model. Leveraging the tunnel convergent deformation results derived from prior analyses with PLAXIS 3D software, the Midas GTS software is utilized to explore the alterations in internal forces and joint failure patterns of the tunnel subjected to convergent deformations of 4cm and 5cm. The findings are as follows: (i) Under the effect of a vertical load, the segment deformation takes on a transverse elliptical shape. (ii) The majority of joint failure is primarily focused around the foundation pit excavation area, where the base of the arch opens inwardly, and the midsection of the arch expands outwardly. (iii) The stress on the structure escalates as the extent of foundation pit excavation increases.

Effect of Seismic Loading on Porewater Pressure in Clayey Soil under Disconnected Piles-Raft Foundation

The disconnected piled raft foundation (DCPRF) is one of the newly introduced foundations for specialization in geotechnical engineering, which significantly reduces the moment and stress on the pile head. In addition, this type of foundation is an ideal choice in areas with seismic activity due to the presence of cushion material between the raft and the piles. This work aims to present a numerical model in PLAXIS 3D software for connected piled raft and disconnected piled raft foundations under the influence of seismic loads and investigate the effect of pore water pressure on the disconnected foundation compared to the connected foundation. The study will depend on the earthquake that struck Iraq in November 2017 in the Halabja region. Strength was 7.3 on the Richter scale with PGA (0.1g). The results of changing pore water pressure showed the variation of pore water pressure. In the case of a DCPRF, the porewater pressure and excess porewater pressure in the soil are much greater than in the case of a CPRF. The increase in the porewater pressure is due to the weight of the building and the weight of the additional cushion layer on the soil. The mechanism for transferring the load in the case of a DCPRF is carried out by raft, then to the cushion, and then to the soil and piles. The load transferred to the soil in the case of DCPRF is more than that transferred to the soil in the CPRF system.

Different aspects regarding slope stability improvement using piles

The problem of slope stability is a common one in the field of geotechnical engineering. There is more than one method that can be adopted in order to improve the stability of a slope. During the last decade, using piles for improving the mechanical behaviour of slopes has become the main approach of dealing with unstable slopes. In the current paper, the stability of a slope was analysed by using the tridimensional finite elements method using different scenarios of consolidation with timber piles. A parametric analysis was carried out for two different slopes: sand slope and soft soil slope. There were also analysed two different constitutive models: Mohr-Coulomb and Hardening Soil Small with different location of the consolidation system. The stability analyses employed both timber piles and concrete piles which were modelled in Plaxis 3D software by using two different approaches: embedded piles and volume piles. In the end, the most favourable position for the pile consolidation system is highlighted in order to attain the maximum stability of the slope. Also, different aspects of the constitutive models, modelling the piles and pile material are discussed from the point of view of slope stability improvement.

Numerical study on lateral response of piles in sandy slopes employing a hardening soil model

The present study investigates the lateral response of piles on sandy slopes. PLAXIS 3D has been employed to perform three-dimensional finite element analysis. A number of numerical assessments have been conducted on the pile with a constant slope height, having different ground slope inclinations from 10° to 30° in sandy soil with different relative densities from 30% to 70%. The embedment length-to-diameter ratio is 30. Responses are compared with the results of horizontal ground conditions. The impact of pile position on the sloping ground has also been investigated by placing the pile at various positions from crest to toe of the sloping ground. The analysis has been done by providing the pile with lateral displacement in one case and a lateral load in the other. The current investigation will examine slope stability with and without pile reinforcement. Lateral pile capacity increases as relative density increases and it decreases as the slope of the ground increases. Maximum lateral displacement and maximum bending moment decrease as relative density increases and increase when the level ground is changed to sloping ground. The depth of the maximum bending moment is also reported.

Vertical bearing capacity of spun precast concrete pile in liquefiable soil: a case study

Spun precast prestressed concrete (SPC) pile has been used in many parts of the world as a viable foundation alternative. This study assesses the load-carrying capacity of SPC piles passing through a deep soft subsoil layer and resting on a dense sand layer. The vertical bearing capacity of the SPC pile has been estimated using various analytical methods and static pile load tests for the Jolshiri area of Dhaka. The liquefaction potential of the site has been assessed using local seismic site conditions, field and laboratory test data. The liquefaction analysis suggests that the topsoil layer is liquefiable to a depth of 4.5 m. The capacity obtained from the load test is compared with those obtained from the different methods, ultimate push-in load, and local design guidelines. Finite Element Analysis (FEA) was performed considering the hardening soil (HS) model using PLAXIS 3D to simulate field conditions. The load settlement response obtained from FEA shows a good agreement with the test results. The capacity examinations primarily suggest that the SPC pile can be a viable foundation solution for the subsoil conditions of Jolshiri Abasion area of Dhaka.

A nonlinear optimization method for calibration of large‐scale deep cement mixing in very soft clay deep excavation

AbstractThis work proposes a novel technique to conduct back‐analysis of lateral displacement of deep cement mixing (DCM) columns in deep excavation construction. For the first time, we propose a process to investigate both soil and underground structure end‐to‐end automatically. The novel technique is a complex combination of three crucial factors: (1) a nature‐inspired optimization algorithm (O), (2) a three‐dimensional PLAXIS Geotechnical Engineering software (P) and (3) a modern Python language programming (P), hereinafter called the a nature‐inspired optimization algorithm (O), a three‐dimensional PLAXIS Geotechnical Engineering software (P) and a modern Python language programming (P) (OPP) technique. The novel meta‐heuristic algorithm simulated the co‐evolved partnership behavior of shrimps and goby fishes, termed Shrimp and Goby Association (SGA), which plays an important role in complex analyses. A series of exams to determine the SGA's performance is conducted on 38 benchmark test functions (IEEE Congress on Evolutionary Computation 2017 and 2019) and three real‐world engineering design problems to showcase its applicability. The metaheuristic and PLAXIS 3D analysis work well together, which makes the back‐analysis technique powerfully to determinate stiffness parameters instead of the traditional approaches. Based on the optimized parameters, the lateral deflection of DCM and soil are well predicted for excavation. This study proposes a technique to estimate efficiently the stiffness parameter for very soft soil. As a consequence of the optimization process, an equation to determine the stiffness parameter of DCM columns from laboratory test is also proposed. Based on the obtained results, this research provides a comprehensive methodology for predicting risk, enhancing safety, saving time and money, and effectively designing and constructing underground structures.

Design of Conical Foundations with Increased Bearing Capacity in Areas of Undermined Soils

This article discusses the foundations of a conical shape directed with their apex downwards to increase the cross-sectional area and, accordingly, the bearing capacity during settlement and under the influence of horizontal tensile strains in undermined areas. To simulate the deformability of undermined and seismically exposed foundations, a three-dimensional expandable box was manufactured and assembled. Models of a conical foundation with an aperture angle of the cones at 90° and 80° were buried into the soil at 0.75 of its height, in order to provide a safety margin for further loading due to an increase in the bearing area when the cone is immersed deeper into the ground. Laboratory and field tests were performed on the vertical loading of single cones before and after horizontal soil displacement. Numerical modeling of the interaction between soil and foundation was carried out for conical foundation models that were considered for laboratory and field testing using the Plaxis 2D (Version 8.2) program. To compare the bearing capacity, isolated shallow foundations with a diameter equal to the cross section of the conical foundation at the intersection with the ground surface were tested. The isolated shallow foundations lost their bearing capacity after 0.15 kN in laboratory tests and after 75 kN in the field tests, while the ultimate bearing capacity of conical foundations with the similar cross section at the soil surface was not achieved, even after 0.2 kN during laboratory tests with horizontal soil displacement and at a load of 100 kN in field tests.

Dynamic Analysis of the Almagrera Tailings Dam with Dry Closure Condition

In light of growing concerns over sustainability, particularly in the wake of environmental disasters like the Aznalcollar dam break, the Spanish authorities have heightened their awareness of issues surrounding ore tailings management. The main aim of this paper is to study the dynamic behavior for the dry closure of the Almagrera dam under the action of an earthquake. This study was carried out with the Plaxis 2D v9.02 program, which uses the finite element (FE) method. The dynamic analysis of the dam was interpreted in terms of deformations, displacements and principal stresses. The construction of the Uniform Seismic Hazard Acceleration Response Spectrum (USHARS) and the selection of real accelerograms for the time-history dynamic calculations is a noted feature of this research. Numerical analyses show that the dam is safe enough because a failure surface has not been formed, although several plastic zones may appear in the dam. The FE study of deformations display that the tailings may attain large deformations, displacements and failure, although this does not jeopardize the safety of the dam where the displacements are smaller than 3 mm. Neither the tailings nor the dam are expected to suffer liquefaction. It was determined that the 0.09 g threshold value is not exceeded in the acceleration-time graphs on the old reservoir field surface, which is the most critical situation.

Static behavior of piled raft foundation in clay

Abstract Wall piles supported with anchors are considered one of the most prevalent types of engineering support. This research includes studying the behavior of wall piles through a numerical parametric study using the FE-method program (PLAXIS 2D). The study includes the most influencing factors such as the angle of the inclination, the vertical spacing between the rows of anchors, and the distance of the first row of anchors from the ground surface. The effects of these factors on the stability of the wall were studied. Optimal positioning of the anchors is crucial, as it maximizes their effectiveness and contributes significantly to reducing the overall construction costs. The use of a guys queue for the economic aspect saves the cost of executing two guys queue because the effect of having two rows does not significantly change the transfer values. The optimum angle of inclination of the tensioner row is 15° in favor of safety, and as it gives good stability of the wall to the wedge wall, with an increase in this angle, the horizontal movement decreases. The first optimum dimension for a row of guys from the horizontal surface of the earth is O = 25%H. Decrease the values of horizontal movement of the wall by increasing the angle of friction.

Effect of damper mass on soil-structure displacement in dynamic response to earthquake vibration with finite element modelling

Earthquake is a natural disaster that always occur inside the region of pacific ring of fire. Many structures such as high-rise buildings, bridges, dams and many more failed and take severe damage due to the impact of the strong vibration of the earthquake. A pile foundation is a type of deep footing which is suitable for high-rise buildings founded on clay soils where its function to prevent potential failures such as bearing capacity and collapse. In addition, the problem of tall buildings is prone to sway and damaged when earthquake strike and such vibrations cause the dynamic behaviour of structure to change significantly in terms of excessive lateral displacements and accelerations. Thus, the effect of damper mass on soil-structure displacement in dynamic response to earthquake vibration was determined. The effectiveness of vibration absorber to the single pile structured in clay soil was modelled and simulated in finite element program PLAXIS 3D version 20 with and without the presence of the damper where the inputs were taken from the Sumatera and Chi – chi earthquakes. The problem was modelled and simulated by drawing a geometry, assigning the soil and pile materials input, loading and boundary conditions, meshing generated and staged construction for calculations of displacement structure output in response to dynamic due to earthquake vibration. The displacement-time with the effect of mass of the vibration with and without absorber are presented. The results show a good performance of damper on the single pile structured on soft soil with different types of earthquakes.

Effect of asymmetry pile’s length on piled raft foundation system under earthquake load

In light of the global development of construction, particularly tall buildings and skyscrapers, researchers have spent years studying and developing types of foundations that are suitable in terms of endurance in heavily loaded and economic terms, particularly in weak soils under dynamic loading. In the event of high-rise buildings or weak soil media, the piled-raft foundation system is considered an efficient system that fits the design criteria. Several factors influence the performance of the piled-raft foundation system, among pile length, which was taken into account in the numerical study using the Plaxis 3D program. Four pile length scenarios are explored using 28 piles in a pattern 4 × 7 group with a rectangular raft of 10 × 20 and 1.5 m thickness. The central piles 3 × 2 are all the same length of 12 m or 20 m, but the others vary to 10 m, 8 m, and 6 m. In addition to the El-Centro seismic loading, a uniform static load of 300 kN/m2 was applied to the weak C- ϕ soil. The results reveal that the length of the asymmetric pile has a substantial effect on the behavior of the piled raft foundation. The symmetry pile’s length has greater static and dynamic load sharing than the asymmetry pile’s length. Static load sharing is greater than dynamic load sharing in all models, with static sharing values of 73.2% for the uniform pile’s length group L12 + 12 and 68.82%, 63.33%, and 55.96% for the asymmetry groups L12 + 10, L12 + 8, and L12 + 6, respectively. With decreasing external pile length, the dynamic load sharing values under 0.1 g intensity are 72.3%, 67.4%, 60.6%, and 55.2%, respectively. When the seismic intensity increases to 0.2 g, these values decrease by around 3%, and so on for 0.3 g. Vertical settlement increases as the exterior pile length decreases and the seismic energy increases. The maximum settlement values for L12 + 12, L12 + 10, L12 + 8, and L12 + 6 at 0.3 g seismic intensity are 137.9, 158.1, 169.7, and 171 mm, respectively. The differential settlement caused by seismic load is greater in the case of the asymmetry pile length group (L12 + 10). The differential settling increases with increasing seismic intensity in all models. The maximum lateral displacement increases as seismic intensity increases, whereas the length of the pile has no impact on the lateral displacement. When compared to a 12-m pile length, a 20-m pile will have a larger load sharing and less settlement, but exhibit a similar trend. The external pile’s length has a slight effect on the factor of safety where the reduction under the seismic load by about 18% for the both symmetry and asymmetry cases respectively in comparison to static case.

Comparative Study on the Reinforced Sand-Bed and the Stone Column in Improving the Clay Deposit Supporting Isolated Footing

The working mechanism of a geotechnical structure can be understood from the deformations and the vertical stresses in the soil media. This article attempts to study the deformation, vertical stress development, and distribution of improved clay deposits carrying a single isolated footing. Through PLAXIS 3D software, numerical analyses were conducted for the ground improvement methods, such as the geogrid reinforced sand-bed (GRSB) and ordinary and geogrid encased stone column installation (OSC and GESC). In GRSB, the results show that the stresses were maximum at the sand–clay interface at a depth of 0.67 B (B—footing width). It is proposed to place an additional layer of geogrid at the interface, and it must be within the critical depth, i.e., the width of the footing. Furthermore, for the current study, the stiffness of the geogrid in the sand layer greater than 500 kN/m was insignificant in soil improvement, whereas the optimum axial stiffness of the stone column encasement was 1,000 kN/m based on the stress concentration factor. The stone column installation improved the clay layer even below the depth of 0.67 B, improving the capacity of clay to carry higher vertical stresses on par with the stone columns. The GRSB carried higher vertical stresses than the unimproved ground. However, the OSC and GESC could carry vertical stresses higher than the GRSB. This knowledge can allow the practitioners to decide the depth of placement of the reinforcement and also to choose an alternate if one method is not feasible for the site.

PLAXIS 3D numerical analysis of complex geotechnical problems of colossal built heritage

The paper aims to contribute to the preservation of high valuable historic masonry structures and historic urban landscapes through the combination of geotechnical, structural engineering. The main objective of the study is to conduct finite element analysis (FEA) of bearing saturated soft clay soil problems and induced structural failure mechanisms. This analysis is based on experimental and numerical studies using coupled PLAXIS 3D FE models. The paper presents a geotechnical analytical model for the measurement of stresses, deformations, and differential settlement of saturated clay soils under colossal stone/brick masonry structures. The study also discusses the behavior of soft clay soils under Qasr Yashbak through numerical analysis, which helps in understanding the studied behavior and the loss of soil-bearing capacity due to moisture content or ground water table (G.W.T) changes. The paper presents valuable insights into the behavior of soft clay soils under colossal stone/ brick masonry structures. The present study summarized specific details about the limitations and potential sources of error in Finite Element Modeling (FEM). Further field research and experimental analysis may be required to address these limitations and enhance the understanding of the studied soft clay soil behavior. The geotechnical problems in historic monuments and structures such as differential settlement are indeed important issues for their conservation since it may induce serious damages. It deserves more in-depth researches.

Pemodelan Numerikal Kestabilan Lereng Batulempung (Studi Kasus Ruas Jalan Sumedang-Cirebon Km 68+750)

The Sumedang-Cirebon Km 68+750 road section is a national road and an important transportation infrastructure in West Java. Albeit the road section's slope has previously been strengthened with bored pile reinforcement, the slope continues to move. This study's objective is to examine slope stability by considering earthquake loads and to suggest improvements for efficient slope reinforcement. Slope stability analysis utilizing PLAXIS 2D program based on the finite element method and DMT-KD Method which is the result of field testing using the Flat Dilatometer Test (DMT)). PLAXIS modeling results show that the slope failure line is deeper below the bored pile reinforcement. The results of the analysis using DMT-KD method showed similar slope failure, the conclusion is DMT-KD method can be the initial basis for slope stability analysis on mudstone. The PLAXIS modeling results obtained a static safety factor of 1.113 and a safety factor due to an earthquake of <1, both of which fall short of the requirements of minimum of 1.5 for static loads and 1.4 for earthquake loads. The body of the road develops cracked as a result of this issue. Additional reinforcement modeling is carried out using bored piles and gabions. As shown in the results of additional reinforcement modeling, bored pile reinforcement that reaches below the slope failure line is more successful than gabion reinforcement at the slope's base in raising the safety factor.

Pemodelan Numerikal Kestabilan Lereng Galian Abutment Jembatan pada Ruas Jalan Tol Bogor – Ciawi – Sukabumi

The Cikereteg Bridge is one of the infrastructures on the Bogor-Ciawi-Sukabumi Toll Road. Based on drilling data, it is recognized that the groundwater level is high and that the slope under the bridge has soil with a low standard penetration tests value (N-SPT) of less than 10. Hence, the stability of the slope is called into doubt. In order to strengthen slope stability under the bridge, this research will investigate slope stability while taking seismic loads into account and offer options for efficient slope reinforcement. By using the PLAXIS 2D software, the finite element method was used to analyze slope stability. The outcomes of the modelling suggest that the slope may not be stable, since it does not fulfill the design slope criteria, which are 1.8 for static conditions and 1.5 for earthquake situations. Respectively, the safety factor value is 1.396 for static condition and 1.068 when given an earthquake load. The design reinforcement model's results highlight that the subdrain reinforcement in combination with bored piles and ground anchors can fulfill the criteria for the slope of the bridge plan.

Numerical investigation of the carrying capacity of single polyurethane foam pile in clay and sand soils

The definition of soil stabilization is a method to enhance the engineering properties. Polyurethane grout is one of the least expensive methods and can be used in construction. Polyurethane injection resin systems for crack injection, slab lifting, soil stabilization, leak sealing, and structural crack repair have been used for the last two decades. Polyurethane foam hasn't been used or understood as a loaded structural element in soils like as embedded piles. In this piece of work, a trial was made to numerically study the behavior of polyurethane foam when used as piles embedded in the clay and sand soils. Plaxis 3D software was adopted to carry out this study. Polyurethane piles of varying diameters and lengths were modelled as embedments in the clay and sand soil, and then incremental loads were applied. Moreover, the study involved the behavior of polyurethane piles when the clay strength was increased. The results indicated that embedded pile resistance to loading increased with the increase in length and pile diameter. When the loading results of polyurethane foam embedded in loose sand are compared with the loading results of piles in soft clay, the ultimate capacity of piles in loose sand, was much higher than that in soft clay. The results also indicated that the polyurethane pile load-carrying capacity increased when L/D ratio decreased for both soft and stiff clay. In this study concrete piles in clay and sand soil were modelled to examine the percentage of loading capacity of concrete piles to that of polyurethane piles for clay and sand soil.

Evaluating the impact of construction-induced vibration on nearby structures when building road embankment in Hanoi

Vietnam is currently undertaking numerous transportation and infrastructure projects in urban areas, particularly in densely populated cities such as Hanoi and Ho Chi Minh City. These cities have high traffic density and frequent traffic congestion, which necessitates the use of construction equipment such as vibratory rollers and pile drivers. However, these machines can cause vibrations that affect the surrounding structures. This study investigates the impact of roller compaction-induced vibration on the building structure of Ring road No.2 in Hanoi, Vietnam. The finite element method (Plaxis 2D) was applied to evaluate the impact of vibration on surrounding structures. The maximum measured velocity is similar to the values derived from numerical analysis. The Finite element method (FEM) results exhibited a high degree of correlation with the actual velocity measurement and frequency dominant structure responses caused by ground-borne vibration induced by roller compaction within the frequency range of 5 Hz to 10 Hz.

Experimental and numerical studies on behavior of upgraded caisson-type quay wall under earthquake loading

Upgrading the caisson-type quay wall could be conducted by strengthening the rubble mound beneath the front caisson toe. Subsequently, the rubble in front of the wall is removed to increase the front water depth. This study assessed the dynamic response of the upgraded quay wall under earthquake loading and compared it to the existing case using a centrifuge test and numerical study. The tests were performed in a dry condition under six consecutive input waves with increasing magnitude. The results indicated that the upgrade significantly reduced the displacements of the quay wall. The deformation trend of the caisson also changed from overturning to slipping. A numerical study of the upgraded case was conducted using the PLAXIS 2D program in the dry condition to validate the model. In addition, the simulation in water was performed to realize the difference between the models with and without water. The numerical results were in good agreement with the experimental model. The deformed mode of the quay wall in the dry condition did not differ from that in water. However, the horizontal displacement of the quay wall in water was higher than in the dry condition, whereas the vertical component was slightly lower.

Influence of Deep Foundation Pit Excavation on Adjacent Pipelines: A Case Study in Nanjing, China

To investigate the pipeline deformation pattern caused by the excavation of deep foundation pits in composite soil–rock strata, a comprehensive study integrating on-site monitoring and numerical simulation was conducted. This study centered on a deep foundation excavation project in the soft soil in Nanjing’s floodplain region. The analyses of pipeline settlement and deformation were performed based on field-measured data. This study investigated the impact of excavation on the mechanical properties of the surrounding soil that resulted in the progressive deformation of adjacent pipelines. Furthermore, numerical simulations were conducted using Plaxis 3D CONNECT Edition v22 finite element analysis software. This study elucidated the influence of factors such as pipeline–pit distance and burial depth on pipeline deformation, conducting a quantitative analysis of their effects. The results indicated that deformation primarily occurs unevenly near pit corners and is less pronounced in soil–rock strata than in single-type soil layers. This study established correlations between pipeline displacements and various factors, offering valuable insights for future excavation projects conducted under similar conditions.