scholarly journals Comparison of Induced Deflection and Forces in Piles Adjacent to Tunnelling and Deep Excavation in 2D and 3D Problems

2018 ◽  
Vol 203 ◽  
pp. 04011
Author(s):  
Ong Yin Hoe ◽  
Hisham Mohamad
Keyword(s):  
Bending Moment ◽  
Pile Group ◽  
3D Models ◽  
Deep Excavation ◽  
Pile Groups ◽  
Out Of Plane ◽  
National University ◽  
Plane Direction ◽  
2D And 3D ◽  
2D Model

There is a trend in Malaysia and Singapore, engineers tend to model the effect of TBM tunneling or deep excavation to the adjacent piles in 2D model. In the 2D model, the pile is modelled using embedded row pile element which is a 1-D element. The user is allowed to input the pile spacing in out-of-plane direction. This gives an impression to engineers the embedded pile row element is able to model the pile which virtually is a 3D problem. It is reported by Sluis (2014) that the application of embedded pile row element is limited to 8D of pile length. It is also reported that the 2D model overestimates the axial load in pile and the shear force and bending moment at pile top and it is not realistic in comparison to 3D model. In this paper, the centrifuge results of single pile and 6-pile group - tunneling problem carried out in NUS (National University of Singapore) are back-analysed with Midas GTS 3D and a 2D program. In a separate case study, pile groups adjacent to a deep excavation is modelled by 3D and 2D program. This paper compares the deflection and forces in piles in 2D and 3D models.

Seismic Response of Pile Groups Improved with Deep Cement mixing Columns in Liquefiable Sand: Shaking Table Tests

2021 ◽  
Author(s):  
Dingwen Zhang ◽  
Anhui Wang ◽  
Xuanming Ding
Keyword(s):  
Seismic Behavior ◽  
Lateral Displacement ◽  
Bending Moment ◽  
Pile Group ◽  
Shaking Table ◽  
Excess Pore Pressure ◽  
Shaking Table Tests ◽  
Pile Groups ◽  
Acceleration Response ◽  
Table Model

A series of shaking table model tests were performed to examine the effects of deep cement mixing (DCM) columns with different reinforcement depths on the seismic behavior of a pile group in liquefiable sand. Due to the DCM column reinforcement, the fundamental natural frequency of the model ground increases noticeably. The excess pore pressure of soils reduces with the increase of reinforcement depths of the DCM columns. Before liquefaction, the acceleration response of soils in the improved cases is obviously lower than that in the unimproved case, but the acceleration attenuation is greater after liquefaction in the unimproved case. Moreover, the lateral displacement of the superstructure, the settlement of the raft, and the bending moment of the piles in the improved cases are significantly reduced compared to those in the unimproved case, and the reduction ratios rise with the increase of reinforcement depth of the DCM columns. However, reinforcement by the DCM columns may result in the variation of the location of the maximum moment that occurs in the pile.

Numerical modeling of seismically-induced slope displacements: a comparison between 2D and 3D finite difference models and Newmark-Displacements

2020 ◽  
Author(s):  
Gisela Domej ◽  
Céline Bourdeau
Keyword(s):  
Finite Difference ◽  
Cross Section ◽  
3D Model ◽  
3D Models ◽  
Southern Spain ◽  
Longitudinal Cross Section ◽  
Landslide Body ◽  
Mesh Grid ◽  
2D And 3D ◽  
2D Model

<p>The majority of numerical landslide models are designed in 2D. In particular, models based on finite difference methods (FDM) are time-consuming and – as a result – in most cases also cost-intensive. 3D models, therefore, increase the processing time significantly. Another contributing factor to long processing times in the context of modeling of seismically-induced displacements is the fact that mesh grid increments must be small due to the necessity of correct wave propagation through the material. The larger the frequency range of the applied seismic signal should be, the smaller has to be the mesh grid increment. 3D models are, however, considered as more realistic.</p><p>In this work, we present a comprehensive study on numerical 2D and 3D models of the Diezma Landslide, Southern Spain. The Landslide is represented in its shape as it appeared at the time of the main rupture on 18<sup>th</sup> of March in four model layouts: (1) a simplified model in 3D that outlines the landslide body with planar triangular tiles, (2) a longitudinal cross section through this simplified 3D model representing the simplified 2D model, (3) a smooth model in 3D that envelops the landslide body according to the main topographic features, and (4) a longitudinal cross section through this smooth 3D model representing the smooth 2D model.</p><p>On both the simplified and the smooth 2D models, a series of 11 seismic scenarios was applied as SV-waves assuming a source sufficiently far for vertical incidence at the model bottoms in order to produce horizontal shear inside the landslide body with respect to the underlying bedrock. All 11 signals are characterized by different frequency contents, Arias Intensities from 0.1 to 1 m/s, moment magnitudes from 5.0 to 7.0 and peak ground accelerations from 0.8 to 1.2 m/s², and therefore correspond to scenarios that represent the local seismicity in Southern Spain.<br>Because of time-related limitations, only four of these signals were respectively applied to the simplified and smooth 3D model. Newmark-Displacements were calculated using all 11 signals with the classic Newmark-Method that approximates the landslide body in 2D by a rigid block on an inclined plane, and with Newmark’s Empirical Law as spatial information covering the landslide area across the slope in regular intervals.</p><p>We present a systematic comparison of all models and obtained displacements, showing that the Newmark-Methods deliver very similar results to the maximum displacements obtained by FDM. Moreover, we discuss on a particular example that – although seeming more accurate in the layout – smooth models lead not necessarily to realistic results.</p>

scholarly journals Evaluation of U10Mo Fuel Plate Irradiation Behavior via Numerical and Experimental Benchmarking

2012 ◽  
Author(s):  
Samuel J. Miller ◽  
Hakan Ozaltun
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
3D Models ◽  
Creep Model ◽  
Element Analysis ◽  
Dimensional Changes ◽  
3 Dimensional ◽  
Out Of Plane ◽  
2D And 3D ◽  
Irradiation Behavior

This article analyzes dimensional changes due to irradiation of monolithic plate-type nuclear fuel and compares results with finite element analysis of the plates during fabrication and irradiation. Monolithic fuel plates tested in the Advanced Test Reactor (ATR) at Idaho National Lab (INL) are being used to benchmark the performance of proposed fuel for several high power research reactors. Post-irradiation metallographic images of plates sectioned at the mid-plane were analyzed to determine dimensional changes of the fuel and the cladding response. A constitutive model of the fabrication process and irradiation behavior of the tested plates was developed using the general purpose commercial finite element analysis package, ABAQUS. Using calculated burn-up profiles of irradiated plates to model the power distribution and including irradiation behaviors such as swelling and irradiation enhanced creep, model simulations allow analysis of plate parameters that are either impossible or infeasible in an experimental setting. The development and progression of fabrication induced stress concentrations at the plate edges was of primary interest, as these locations have a unique stress profile during irradiation. Additionally, comparison between 2D and 3D models was performed to optimize analysis methodology. In particular, the ability of 2D and 3D models to account for out of plane stresses which result in 3-dimensional creep behavior that is a product of these components. Results show that assumptions made in 2D models for the out-of-plane stresses and strains cannot capture the 3-dimensional physics accurately and thus 2D approximations are not representative. Stress-strain fields are dependent on plate geometry and irradiation conditions, thus, if stress based criteria is used to predict plate behavior (as opposed to material impurities, fine micro-structural defects, or sharp power gradients), unique 3D finite element formulation for each plate is required.

scholarly journals Numerical analysis of reducing tunneling effect on viaduct piles foundation by jet grouted wall

2021 ◽  
Vol 15 (1) ◽  
pp. 75-86
Author(s):  
Kamel Asker ◽  
Mohmed Tarek Fouad ◽  
Mohamed Bahr ◽  
Ahmed El-Attar
Keyword(s):  
Numerical Model ◽  
Interaction Mechanism ◽  
Back Analysis ◽  
Bending Moment ◽  
Pile Group ◽  
Tunneling Effect ◽  
Shield Tunnel ◽  
Pile Groups ◽  
Perfectly Plastic ◽  
Jet Grouting

Purpose. The target of this study is divided into two parts. The first part is concerned with capability of numerical model to simulate the tunneling process. The second part is related to studying the interaction mechanism between the tunnel, protection technique, and soil. This study themes are investigated by analyzing different protection technique configuration, considering different stiffness of the grouted wall, and applying different interface coefficient between the wall and the soil. Methods. The method used in this study to check the accuracy of the proposed numerical model is 4-D ABAQUS program. The typical excavation of a tunnel is simulated step by step with an assumed rate of tunnel advancement (0.5 to 1.5 m/hr). The soil material utilized in this model is elastic perfectly plastic (the Mohr-Сoulomb criterion), while elastic material is modeled as solid element (S4R) adopted for lining, grouting, filling gaps, shielding, constructing piles, and jet grouted wall. Findings. Results showed that the closer jet grouting to the tunnel with embedded length of 1.5 times tunnel diameter, the better effect on reducing the lateral deformation and bending moment generated on piles. Otherwise, increasing wall thickness more than double grouted column diameter would not affect its shielding efficiency. Furthermore, either increasing or decreasing friction coefficient even if rough between the grouted wall and soil had no effect on the pile behavior. Additionally, applying Mohr-Coulomb criteria for grouted wall with high stiffness allowed realistic response of the pile group. Originality.Capability of the proposed model is verified by back analysis of Changsha Subway Line 1 project, where the shield tunnel would be constructed near existing pile groups of L off-ramp of the Xinzhong Road viaduct. Practical implications. Increasing grouted wall configuration is more effective than mechanical properties or its interface coefficient with surrounded soil in mitigating tunneling effect on nearby piles. Keywords: tunneling, jet grouting, gield measurements, ABAQUS, Changsha Subway Line 1

scholarly journals Numerical Analysis of Stratified and Slug Flows

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Saliha Nouri ◽  
Zouhaier Hafsia ◽  
Salah Mahmoud Boulaaras ◽  
Ali Allahem ◽  
Salem Alkhalaf ◽  
...  
Keyword(s):  
Axial Velocity ◽  
Volume Fraction ◽  
Stratified Flow ◽  
3D Models ◽  
Water Volume ◽  
Volume Distribution ◽  
Two Phase ◽  
Slug Flows ◽  
2D And 3D ◽  
2D Model

The main purpose of this study is to compare two-dimensional (2D) and three-dimensional (3D) two-phase models for both stratified and slug flows. These two flow regimes interest mainly the petroleum and chemical industries. The volume of fluid (VOF) approach is used to predict the interface between the two-phase flows. The stratified turbulent flow corresponds to the oil-water phases through a cylindrical pipe. To simulate the turbulent stratified flow, the k − ω turbulence model is used. The slug laminar flow concerns the kerosene-water phases through a rectangular microchannel. The simulated results are validated using the previous experimental results available in the literature. For the stratified flow, the axial velocity and the water volume fraction profiles obtained by 2D and 3D models approximate the measurement profiles at the same test section. Also, the T-junction in a 2D model affects only the inlet vicinity. For downstream, the 2D and 3D models lead to the same axial velocity and water volume distribution. For the slug flow, the simulated results show that the 3D model predicts the thin film wall contrary to the 2D model. Moreover, the 2D model underestimates the slug length.

scholarly journals Potassium Ascorbate with Ribose: Promising Therapeutic Approach for Melanoma Treatment

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Carlotta Cavicchio ◽  
Mascia Benedusi ◽  
Erika Pambianchi ◽  
Alessandra Pecorelli ◽  
Franco Cervellati ◽  
...  
Keyword(s):  
Connexin 43 ◽  
Early Stage ◽  
3D Models ◽  
Definitive Treatment ◽  
Novel Treatments ◽  
Promising Therapeutic Approach ◽  
Current Therapies ◽  
Melanoma Treatment ◽  
2D And 3D ◽  
2D Model

While surgery is the definitive treatment for early-stage melanoma, the current therapies against advanced melanoma do not yet provide an effective, long-lasting control of the lesions and a satisfactory impact on patient survival. Thus, research is also focused on novel treatments that could potentiate the current therapies. In the present study, we evaluated the effect of potassium ascorbate with ribose (PAR) treatment on the human melanoma cell line, A375, in 2D and 3D models. In the 2D model, in line with the current literature, the pharmacological treatment with PAR decreased cell proliferation and viability. In addition, an increase in Connexin 43 mRNA and protein was observed. This novel finding was confirmed in PAR-treated melanoma cells cultured in 3D, where an increase in functional gap junctions and a higher spheroid compactness were observed. Moreover, in the 3D model, a remarkable decrease in the size and volume of spheroids was observed, further supporting the treatment efficacy observed in the 2D model. In conclusion, our results suggest that PAR could be used as a safe adjuvant approach in support to conventional therapies for the treatment of melanoma.

scholarly journals 3D Centrifuge Modeling of the Effect of Twin Tunneling to an Existing Pile Group

2017 ◽  
Vol 7 (5) ◽  
pp. 2030-2040
Author(s):  
M. A. Soomro ◽  
M. A. Keerio ◽  
M. A. Soomro ◽  
D. K. Bangwar
Keyword(s):  
Axial Force ◽  
Urban Areas ◽  
Load Transfer ◽  
Three Dimensional ◽  
Bending Moment ◽  
Pile Group ◽  
Centrifuge Modeling ◽  
Pile Groups ◽  
Moment Capacity ◽  
Centrifuge Tests

In densely built urban areas, it is inevitable that tunnels will be constructed near existing pile groups. The bearing capacity of a pile group depends on shear stress along the soil-pile interface and normal stress underneath the pile toe while the two would be adversely affected by the unloading process of tunneling. Although extensive studies have been conducted to investigate the effects of tunnel construction on existing single piles, the influence of twin tunnel advancement on an existing pile group is merely reported in the literature. In this study, a series of three-dimensional centrifuge tests were carried out to investigate the response of an existing pile group under working load subjected to twin tunneling at various locations in dry Toyoura sand. In each twin tunneling test, the first tunnel is constructed near the mid-depth of the pile shaft, while the second tunnel is subsequently constructed either next to, below or right underneath the pile toe (Tests G_ST, G_SB and G_SU, respectively). Among the three tests, the 2nd tunnel excavated near the pile toe (Test G_ST) results in the smallest settlement but the largest transverse tilting (0.2%) of pile group. Significant bending moment was induced at the pile head (1.4 times of its bending moment capacity) due to the 2nd tunnel T. On the contrary, tunneling right underneath the toe of pile (i.e., Test G_SU) results in the smallest tilting but largest settlement of the pile group (4.6% of pile diameter) and incremental mobilisation of shaft resistance (13%). Due to stress release by the twin tunneling, the axial force taken by the front piles close to tunnels was reduced and partially transferred to the rear piles. This load transfer can increase the axial force in rear piles by 24%.

scholarly journals A Study on the Seismic Response Characteristics of an Oblique Pile Group-Soil-Structure with Different Pile Caps

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Desen Kong ◽  
Yifei Bai ◽  
Yongpo Chen ◽  
Meixu Deng
Keyword(s):  
Soil Structure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Layer ◽  
Bending Moment ◽  
Horizontal Displacement ◽  
Pile Group ◽  
Vertical Displacement ◽  
Pile Groups ◽  
Cap Model

For the study of interaction between piles-soil-structure with different caps, the FLAC3D finite difference software was used as the research tool, and dynamic load was El Centro seismic wave. The numerical model of obliquely pile groups of the pile-soil-structure with low cap and high cap was established, respectively. The variation of pore pressure, the moment, the displacement of piles, and the displacement of pier was analyzed. The results indicate that under the action of earthquake, the distribution of pore water pressure in the soil layer increases gradually from top to bottom. The instantaneous negative value of partial soil due to shear dilation occurs at the peak of vibration acceleration. The middle area of the pile foundation in sandy soil is prone to liquefaction. In the same model, the maximum bending moment of inclined piles is greater than that of vertical piles. The vertical displacement of the vertical piles is a constant value along the depth, while the vertical displacement of the inclined piles is changed along the depth of the buried piles. In the high cap model, the horizontal displacement of the inclined piles is no longer monotonous along the burying depth, and the maximum value occurs in the sand soil layer. The vertical and horizontal displacements of the inclined piles and vertical piles in the high cap model are obviously greater than those of the low cap model. The maximum horizontal displacement of the pier of the two models occurs at the same time.

MICROSTRUCTURE MODELING AND PREDICTION OF THE MECHANICAL PROPERTIES OF ADVANCED HIGH STRENGTH STEELS

2014 ◽  
Vol 11 (supp01) ◽  
pp. 1344009 ◽  
Author(s):  
ALIREZA ASGARI ◽  
BERNARD F. ROLFE ◽  
PETER D. HODGSON
Keyword(s):  
Mechanical Properties ◽  
Phase Distribution ◽  
High Strength Steels ◽  
High Strength ◽  
3D Models ◽  
Strain Partitioning ◽  
Heterogeneous Microstructure ◽  
Advanced High Strength Steels ◽  
2D And 3D ◽  
2D Model

Dual phase (DP) steels were modeled using 2D and 3D representative volume elements (RVE). Both the 2D and 3D models were generated using the Monte-Carlo-Potts method to represent the realistic microstructural details. In the 2D model, a balance between computational efficiency and required accuracy in truly representing heterogeneous microstructure was achieved. In the 3D model, a stochastic template was used to generate a model with high spatial fidelity. The 2D model proved to be efficient for characterization of the mechanical properties of a DP steel where the effect of phase distribution, morphology and strain partitioning was studied. In contrast, the current 3D modeling technique was inefficient and impractical due to significant time cost. It is shown that the newly proposed 2D model generation technique is versatile and sufficiently accurate to capture mechanical properties of steels with heterogeneous microstructure.

Geometrical effects on the load transfer mechanism of pile groups: three-dimensional numerical analysis

2018 ◽  
Vol 55 (5) ◽  
pp. 749-757 ◽  
Author(s):  
Yaru Lv ◽  
Dongdong Zhang
Keyword(s):  
Load Transfer ◽  
Three Dimensional ◽  
Bending Moment ◽  
Pile Group ◽  
Transfer Mechanism ◽  
Single Pile ◽  
Pile Groups ◽  
Load Transfer Mechanism ◽  
Side Resistance ◽  
Geometrical Effects

This paper investigates geometrical effects on the load transfer mechanism of off-ground capped pile groups subjected to vertical load by four three-dimensional numerical simulations, including a circular single pile, an X-shaped cross-sectional concrete (XCC) single pile, a 4 × 4 circular pile group, and a 4 × 4 XCC pile group. The ultimate bearing capacities of the XCC and circular piles within pile groups are approximately 0.86 and 0.74 times that of the XCC and circular single piles, respectively. The group efficiency of the XCC pile group is mainly improved by its side resistance. Comparing the XCC pile group to the circular pile group, the increment in side resistance is almost larger than the increment in pile perimeter, indicating that the pile geometry alters the load transfer mechanism via stress concentration and lateral stress arching. A nonuniform load distribution on piles within a capped pile group causes a bending moment along the pile shafts. The bending moment of XCC piles is smaller than that of circular piles because the raft stiffness of an XCC pile group is increased by its larger circumscribing pile diameter.

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