Bio-grouting to enhance axial pull-out response of pervious concrete ground improvement piles

2018 ◽  
Vol 55 (1) ◽  
pp. 119-130 ◽  
Author(s):  
Hai Lin ◽  
Muhannad T. Suleiman ◽  
Hanna M. Jabbour ◽  
Derick G. Brown
Keyword(s):  
Large Scale ◽  
Mechanical Response ◽  
Ground Improvement ◽  
Radial Distance ◽  
Pervious Concrete ◽  
S Wave ◽  
Injection Point ◽  
Concrete Piles ◽  
Pull Out ◽  
Surrounding Soil

Bio-grouting is an environmentallly friendly, sustainable, and low-cost ground improvement technique, which mainly utilizes microbial-induced carbonate precipitation. Previous large-scale applications of MICP have encountered practical difficulties including bio-clogging, which resulted in a limited zone of cemented soil around injection points. The research presented in this paper focuses on evaluating the feasibility of cementing a limited soil zone surrounding permeable piles using MICP bio-grouting to improve the mechanical response of permeable piles under axial pull-out loading. Two instrumented pervious concrete piles (test units), one with and one without MICP bio-grouting, were subjected to pull-out loading at the Soil-Structure Interaction Facility at Lehigh University. The pervious concrete pile served as an injection point during the MICP bio-grouting. The mechanical responses of the test units and surrounding soil were analyzed, along with shear wave (S-wave) velocities, moisture, and CaCO3 contents of the surrounding soil. The results presented in this paper demonstrate that the limited MICP-improved zone, extending a radial distance of approximately 102 mm around pervious concrete piles, improved the load–displacement response, load transfer, and pile capacity under pull-out loading. The ratios between ultimate loads of the test units with and without MICP bio-grouting were 4.2. The average shaft resistance along the pile with MICP bio-grouting was up to 2.8 times higher than that of the pile without bio-grouting.

scholarly journals Behavior of Pervious Concrete Pile based on Vertical Loading

2021 ◽  
Vol 9 (VII) ◽  
pp. 3884-3891
Author(s):  
Avinash A Rakh
Keyword(s):  
Ground Improvement ◽  
The United States ◽  
Pervious Concrete ◽  
Water Runoff ◽  
Vertical Load ◽  
Concrete Piles ◽  
Concrete Pile ◽  
Improvement Method ◽  
Granular Piles ◽  
Surrounding Soil

Permeable granular piles are used to increase the time rate of consolidation, reduce liquefaction potential, improve bearing capacity, and reduce settlement. However, the behaviour of granular piles depends on the confinement provided by surrounding soil, which limits their use in very soft clays and silts, and organic and peat soils. This research effort aims to develop a new ground-improvement method using pervious concrete piles. Pervious concrete piles provide higher stiffness and strength, which are independent of surrounding soil confinement, while offering permeability comparable to granular piles. This proposed ground-improvement method can improve the performance of different structures supported on poor soils. To achieve the goal of the research project, a series of pervious concrete sample mixing has been conducted to investigate the pervious concrete material properties. Laboratory tests are carried out on a pervious concrete pile of 100 mm diameter and variation at different lengths (500mm,400mm,300mm) surrounded by sand of different density. The tests are carried out either with an entire equivalent area loaded to estimate the stiffness of improved ground or only a column loaded to estimate the limiting axial capacity. Pervious concrete is a special concrete product made primarily of a single-sized aggregate. Pervious concrete has been used in pavements to reduce storm-water-runoff quantities and perform initial water-quality treatment by allowing water to penetrate through the surface. In the United States, pervious concrete is mainly used in pavement applications, including sidewalks, parking lots, tennis courts, pervious base layers under heavy-duty pavements, and low traffic-density areas. The vertical load responses of pervious concrete are the variation of soil stresses and displacement are discussed. Nine tests are conducted on pervious concrete pile further investigate the behaviour of the pervious concrete pile and surrounding soil under vertical load condition. Therefore, Pervious Concrete Piles is particularly suitable for reinforcing subsoil that has low strength and poor permeability.

Experimental investigation of compaction-grouted soil nails

2017 ◽  
Vol 54 (12) ◽  
pp. 1728-1738 ◽  
Author(s):  
Qiong Wang ◽  
Xinyu Ye ◽  
Shanyong Wang ◽  
Scott William Sloan ◽  
Daichao Sheng
Keyword(s):  
Large Scale ◽  
Scale Model ◽  
Interface Shear ◽  
Soil Nails ◽  
Soil Nail ◽  
Pull Out ◽  
Grouting Pressure ◽  
Large Scale Model ◽  
Ultimate Failure ◽  
Surrounding Soil

An innovative compaction-grouted soil nail was designed by injecting grout into a special latex balloon (grouting bag) to avoid bleeding and penetration of grout into the surrounding soil. A series of large-scale model tests was performed to study the surrounding soil responses due to grouting and the subsequent pull-out resistance of the soil nail. The experimental results show that grouting pressure plays an important role in the enhancement of the density and (or) strength of the surrounding soil. In addition, during the pull-out process, the compaction-grouted soil nail exhibits a strain-hardening behaviour without a yield point. This is a significant advantage of this new soil nail, indicating that it can enable soil masses to remain stable against a relatively large deformation before ultimate failure. The main factors behind the improvement of the pull-out resistance of the new soil nail are, first, the compaction–densification of the soil near the grouting bag due to grouting, resulting in the enhancement of the shear strength of the soil, and, second, the enlargement of the grouting bag, causing the increase of the interface shear and end resistance to the pull-out of the soil nail.

scholarly journals The effect of melt on seismic anisotropy of ice polycrystalline aggregates

2020 ◽  
Author(s):  
Maria-Gema Llorens ◽  
Albert Griera ◽  
Paul D. Bons ◽  
Enrique Gomez-Rivas ◽  
Ilka Weikusta ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Large Scale ◽  
Seismic Anisotropy ◽  
Mechanical Response ◽  
Seismic Velocity ◽  
Solid Phase ◽  
Ice Sheets ◽  
P Wave ◽  
S Wave ◽  
Two Phase

<p>Observations of P-wave (Vp) and S-wave (Vs) velocities in Antarctic and Greenland ice sheets show a strong decrease of 25% of Vs in their deep parts, while Vp remains approximately constant. The drastic Vs decrease corresponds to the basal “echo free zone”, where large-scale disturbances and strong preferred ice crystal orientation are found. According to Wittlinger and Farra (2014), the low Vs may be due to the presence of unfrozen liquids resulting from pre-melting at grain joints and/or melting of chemical solutions buried in ice. In this contribution we investigate the evolution of seismic velocity anisotropy during deformation of temperate ice by means of microdynamic numerical simulations. Temperate ice is modelled as a two-phase non-linear viscous aggregate constituted by a solid phase (ice polycrystal) and a liquid phase (melt). The viscoplastic full-field numerical approach (VPFFT-ELLE) (Lebensohn and Rollet, 2020) is used to calculate the mechanical response of the two-phase aggregate, which deforms purely by dislocation glide. Viscoplastic deformation is coupled with dynamic recrystallisation processes, such as grain boundary migration, intracrystalline recovery and polygonisation (Llorens et al., 2017), all driven by the reduction of surface and strain energies. The changes in P- and S-wave velocities are calculated with the AEH-EBSD software (Vel et al., 2016) from single crystal stiffness and microstructural measurements of crystal preferred orientations (CPO) during deformation. Regardless the amount of melt and intensity of recrystallisation, all simulations evolve from a fabric defined by randomly oriented c-axes to a c-axis preferred orientation (CPO) distribution approximately perpendicular to the shear plane.  For purely solid aggregates, the results show that the highest Vp and lowest Vs velocities are rapidly aligned with the CPO (at a shear strain of 1), and then evolve to a strong single maximum with progressive deformation. This alignment has been previously predicted in models, experiments and measured in ice core samples. When melt is present, the maximum and minimum seismic velocities are not aligned with the CPO and both Vp and Vs are considerably lower than in cases without melt.  However, if the bulk modulus of ice is assumed for the melt phase, the presence of melt produces a remarkable decrease in S-wave velocity while Vp is maintained constant. These results suggest that the decrease in S-wave velocity observed at the base of ice sheets could be explained by the presence of overpressured melt, which would be unconnected at triple grain junctions in the ice polycrystal.</p><p> </p><p>References:</p><p>Wittlinger and Farra. 2014. Polar Science 9, 66-79.</p><p>Lebensohn and Rollet. 2020. Computational Mat. Sci. 173, 109336.</p><p>Llorens, et al. 2017. Philosophical Transactions of the Royal Society A, 375, 20150346.</p><p>Vel, et al. 2016. Computer Methods in Applied Mechanics and Engineering 310, 749-779.</p><p> </p>

scholarly journals Optimizing Manufacturing and Osseointegration of Ti6Al4V Implants through Precision Casting and Calcium and Phosphorus Ion Implantation? In Vivo Results of a Large-Scale Animal Trial

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1670 ◽  
Author(s):  
Wölfle-Roos JV ◽  
Katmer Amet B ◽  
Fiedler J ◽  
Michels H ◽  
Kappelt G ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Large Scale ◽  
In Vivo Studies ◽  
Control Group ◽  
Implant Surface ◽  
Precision Casting ◽  
Pull Out ◽  
Significant Difference ◽  
Calcium And Phosphorus

Background: Uncemented implants are still associated with several major challenges, especially with regard to their manufacturing and their osseointegration. In this study, a novel manufacturing technique—an optimized form of precision casting—and a novel surface modification to promote osseointegration—calcium and phosphorus ion implantation into the implant surface—were tested in vivo. Methods: Cylindrical Ti6Al4V implants were inserted bilaterally into the tibia of 110 rats. We compared two generations of cast Ti6Al4V implants (CAST 1st GEN, n = 22, and CAST 2nd GEN, n = 22) as well as cast 2nd GEN Ti6Al4V implants with calcium (CAST + CA, n = 22) and phosphorus (CAST + P, n = 22) ion implantation to standard machined Ti6Al4V implants (control, n = 22). After 4 and 12 weeks, maximal pull-out force and bone-to-implant contact rate (BIC) were measured and compared between all five groups. Results: There was no significant difference between all five groups after 4 weeks or 12 weeks with regard to pull-out force (p > 0.05, Kruskal Wallis test). Histomorphometric analysis showed no significant difference of BIC after 4 weeks (p > 0.05, Kruskal–Wallis test), whereas there was a trend towards a higher BIC in the CAST + P group (54.8% ± 15.2%), especially compared to the control group (38.6% ± 12.8%) after 12 weeks (p = 0.053, Kruskal–Wallis test). Conclusion: In this study, we found no indication of inferiority of Ti6Al4V implants cast with the optimized centrifugal precision casting technique of the second generation compared to standard Ti6Al4V implants. As the employed manufacturing process holds considerable economic potential, mainly due to a significantly decreased material demand per implant by casting near net-shape instead of milling away most of the starting ingot, its application in manufacturing uncemented implants seems promising. However, no significant advantages of calcium or phosphorus ion implantation could be observed in this study. Due to the promising results of ion implantation in previous in vitro and in vivo studies, further in vivo studies with different ion implantation conditions should be considered.

scholarly journals On the effects of membrane viscosity on transient red blood cell dynamics

Soft Matter ◽  
2020 ◽  
Vol 16 (26) ◽  
pp. 6191-6205 ◽  
Author(s):  
Fabio Guglietta ◽  
Marek Behr ◽  
Luca Biferale ◽  
Giacomo Falcucci ◽  
Mauro Sbragaglia
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Blood Circulation ◽  
Hydraulic Properties ◽  
Large Scale ◽  
Mechanical Response ◽  
Cell Dynamics ◽  
Membrane Viscosity

Computational Fluid Dynamics is currently used to design and improve the hydraulic properties of biomedical devices, wherein the large scale blood circulation needs to be simulated by accounting for the mechanical response of RBCs at the mesoscale.

Continuum Description of the Time- and Strain-Dependent Poisson’s Ratio of Ligament Under Finite Deformation

2013 ◽  
Author(s):  
Aaron M. Swedberg ◽  
Shawn P. Reese ◽  
Steve A. Maas ◽  
Benjamin J. Ellis ◽  
Jeffrey A. Weiss
Keyword(s):  
Large Scale ◽  
Mechanical Response ◽  
Tensile Deformation ◽  
Large Strain ◽  
Fiber Direction ◽  
Strain Behavior ◽  
Nonlinear Stress ◽  
Poisson's Ratios ◽  
Poisson’S Ratios ◽  
Strain Dependent

Ligament volumetric behavior controls fluid and thus nutrient movement as well as the mechanical response of the tissue to applied loads. The reported Poisson’s ratios for tendon and ligament subjected to tensile deformation loading along the fiber direction are large, ranging from 0.8 ± 0.3 in rat tail tendon fascicles [1] to 2.98 ± 2.59 in bovine flexor tendon [2]. These Poisson’s ratios are indicative of volume loss and thus fluid exudation [3,4]. We have developed micromechanical finite element models that can reproduce both the characteristic nonlinear stress-strain behavior and large, strain-dependent Poisson’s ratios seen in tendons and ligaments [5], but these models are computationally expensive and unfeasible for large scale, whole joint models. The objectives of this research were to develop an anisotropic, continuum based constitutive model for ligaments and tendons that can describe strain-dependent Poisson’s ratios much larger than the isotropic limit of 0.5. Further, we sought to demonstrate the ability of the model to describe experimental data, and to show that the model can be combined with biphasic theory to describe the rate- and time-dependent behavior of ligament and tendon.

Molecular Dynamics Simulation of a Pullout Test on a Carbon Nanotube in a Polymer Matrix

2014 ◽  
Vol 1700 ◽  
pp. 61-66
Author(s):  
Guttormur Arnar Ingvason ◽  
Virginie Rollin
Keyword(s):  
Molecular Dynamics ◽  
Polymer Matrix ◽  
Large Scale ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Atomistic Simulations ◽  
Polymer Molecules ◽  
Molecular Potential ◽  
Pull Out ◽  
Walled Carbon Nanotubes

ABSTRACTAdding single walled carbon nanotubes (SWCNT) to a polymer matrix can improve the delamination properties of the composite. Due to the complexity of polymer molecules and the curing process, few 3-D Molecular Dynamics (MD) simulations of a polymer-SWCNT composite have been run. Our model runs on the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), with a COMPASS (Condensed phase Optimized Molecular Potential for Atomistic Simulations Studies) potential. This potential includes non-bonded interactions, as well as bonds, angles and dihedrals to create a MD model for a SWCNT and EPON 862/DETDA (Diethyltoluenediamine) polymer matrix. Two simulations were performed in order to test the implementation of the COMPASS parameters. The first one was a tensile test on a SWCNT, leading to a Young’s modulus of 1.4 TPa at 300K. The second one was a pull-out test of a SWCNT from an originally uncured EPON 862/DETDA matrix.

The relation between seismic P‐ and S‐wave velocity dispersion in saturated rocks

Geophysics ◽  
1994 ◽  
Vol 59 (1) ◽  
pp. 87-92 ◽  
Author(s):  
Gary Mavko ◽  
Diane Jizba
Keyword(s):  
Wave Velocity ◽  
Large Scale ◽  
Velocity Dispersion ◽  
Seismic Velocity ◽  
Ultrasonic Velocities ◽  
S Wave ◽  
Local Flow ◽  
Wave Velocities ◽  
Shear Compliance

Seismic velocity dispersionin fluid-saturated rocks appears to be dominated by tow mecahnisms: the large scale mechanism modeled by Biot, and the local flow or squirt mecahnism. The tow mechanisms can be distuinguished by the ratio of P-to S-wave dispersions, or more conbeniently, by the ratio of dynamic bulk to shear compliance dispersions derived from the wave velocities. Our formulation suggests that when local flow denominates, the dispersion of the shear compliance will be approximately 4/15 the dispersion of the compressibility. When the Biot mechanism dominates, the constant of proportionality is much smaller. Our examination of ultrasonic velocities from 40 sandstones and granites shows that most, but not all, of the samples were dominated by local flow dispersion, particularly at effective pressures below 40 MPa.

Geosynthetic Encased Column: comparison between numerical and experimental results

2021 ◽  
Vol 44 (4) ◽  
pp. 1-12
Author(s):  
Nima Alkhorshid ◽  
Gregório Araújo ◽  
Ennio Palmeira
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Ground Improvement ◽  
Soft Soil ◽  
Experimental Tests ◽  
High Permeability ◽  
Soft Soils ◽  
Column Comparison ◽  
Surrounding Soil ◽  
Granular Column

The use of granular column is one of the ground improvement methods used for soft soils. This method improves the foundation soils mechanical properties by displacing the soft soil with the compacted granular columns. The columns have high permeability that can accelerate the excess pore water pressure produced in soft soils and increase the undrained shear strength. When it comes to very soft soils, the use of granular columns is not of interest since these soils present no significant confinement to the columns. Here comes the encased columns that receive the confinement from the encasement materials. In this study, the influence of the column installation method on the surrounding soil and the encasement effect on the granular column performance were investigated using numerical analyses and experimental tests. The results show that numerical simulations can reasonably predict the behavior of both the encased column and the surrounding soil.

Molecular Dynamics Modeling the Nano-Identation of Titanium

2021 ◽  
Author(s):  
Peiqiang Yang ◽  
Xueping Zhang ◽  
Zhenqiang Yao ◽  
Rajiv Shivpuri
Keyword(s):  
Molecular Dynamics ◽  
Plastic Deformation ◽  
Titanium Alloys ◽  
Large Scale ◽  
Mechanical Response ◽  
Pure Titanium ◽  
Dynamics Modeling ◽  
Dynamics Model ◽  
Nano Indentation ◽  
Molecular Dynamics Modeling

Abstract Titanium alloys’ excellent mechanical and physical properties make it the most popular material widely used in aerospace, medical, nuclear and other significant industries. The study of titanium alloys mainly focused on the macroscopic mechanical mechanism. However, very few researches addressed the nanostructure of titanium alloys and its mechanical response in Nano-machining due to the difficulty to perform and characterize nano-machining experiment. Compared with nano-machining, nano-indentation is easier to characterize the microscopic plasticity of titanium alloys. This research presents a nano-indentation molecular dynamics model in titanium to address its microstructure alteration, plastic deformation and other mechanical response at the atomistic scale. Based on the molecular dynamics model, a complete nano-indentation cycle, including the loading and unloading stages, is performed by applying Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The plastic deformation mechanism of nano-indentation of titanium with a rigid diamond ball tip was studied under different indentation velocities. At the same time, the influence of different environment temperatures on the nano-plastic deformation of titanium is analyzed under the condition of constant indentation velocity. The simulation results show that the Young’s modulus of pure titanium calculated based on nano-indentation is about 110GPa, which is very close to the experimental results. The results also show that the mechanical behavior of titanium can be divided into three stages: elastic stage, yield stage and plastic stage during the nano-indentation process. In addition, indentation speed has influence on phase transitions and nucleation of dislocations in the range of 0.1–1.0 Å/ps.

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