Front-face pressure drop during the standstill phase for EPB mechanized tunnelling in coarse-grained soils

Abstract Knowledge of porous media structure is an essential part of the hydrodynamic investigation of fluid flow in porous media. To study soil behavior (as a granular porous media) and water and contaminant movement in the vadose zone, appropriate estimation of soil water retention curve (SWRC) and soil hydraulic conductivity curve (SHCC) has a pivotal role and is one of the most challenging topics for researchers and engineers in soil and water science. The SWCR can be approximated using an accurate particle size distribution (PSD) function. In this study by applying random close packing (RCP) method as an encouraging method for predicting and studying particle configuration, an optimal particle size distribution is developed for coarse-grained soils (0.025 mm < PSD < 3.35mm). The mentioned RCP is generated using heuristic algorithm with merging applicable equations of soil science. For porous media modeling, MATLAB software is used and the predicted results by the optimal model for the parameters of porosity, pressure drop, and saturated hydraulic conductivity are compared with laboratory measurements. Experimental design is conducted by MINITAB and predicted coarse-grained soils structure by the model is compared with 4 sifted soils. The results of the sensitivity analysis showed that the porosity obtained from the model is strongly sensitive to the resolution factor and should be chosen with a sufficiently large amount (higher than 250). Results showed good consistency (up to 95%) between predicted porosity and only 10% difference in pressure drop and permeability with observed measurements.

Download Full-text

The Alteration of the Pore Spaces in Sandstones

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100071491 ◽

1973 ◽

Vol 31 ◽

pp. 210-211

Author(s):

R. E. Ferrell ◽

G. G. Paulson

Keyword(s):

Electron Microscope ◽

Scanning Electron Microscope ◽

The Other ◽

Coarse Grained ◽

Depositional Fabric ◽

Soluble Components ◽

Scanning Electron ◽

Shape And Size

The pore spaces in sandstones are the result of the original depositional fabric and the degree of post-depositional alteration that the rock has experienced. The largest pore volumes are present in coarse-grained, well-sorted materials with high sphericity. The chief mechanisms which alter the shape and size of the pores are precipitation of cementing agents and the dissolution of soluble components. Each process may operate alone or in combination with the other, or there may be several generations of cementation and solution.The scanning electron microscope has ‘been used in this study to reveal the morphology of the pore spaces in a variety of moderate porosity, orthoquartzites.

Download Full-text

On the Origin of the Microscystalline Structure in Rapidly Solidified IN-100 Powder

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078821 ◽

1977 ◽

Vol 35 ◽

pp. 260-261

Author(s):

J. M. Walsh ◽

K. P. Gumz ◽

J. C. Whittles ◽

B. H. Kear

Keyword(s):

The Other ◽

Coarse Grained ◽

Microcrystalline Structure ◽

Routine Examination ◽

Atomization Process ◽

Centrifugal Atomization ◽

Splat Quenching ◽

Powder Particles ◽

Dendritic Microstructures ◽

Rapidly Solidified

During a routine examination of the microstructure of rapidly solidified IN-100 powder, produced by a newly-developed centrifugal atomization process1, essentially two distinct types of microstructure were identified. When a high melt superheat is maintained during atomization, the powder particles are predominantly coarse-grained, equiaxed or columnar, with distinctly dendritic microstructures, Figs, la and 4a. On the other hand, when the melt superheat is reduced by increasing the heat flow to the disc of the rotary atomizer, the powder particles are predominantly microcrystalline in character, with typically one dendrite per grain, Figs, lb and 4b. In what follows, evidence is presented that strongly supports the view that the unusual microcrystalline structure has its origin in dendrite erosion occurring in a 'mushy zone' of dynamic solidification on the disc of the rotary atomizer.The critical observations were made on atomized material that had undergone 'splat-quenching' on previously solidified, chilled substrate particles.

Download Full-text

Correlation between dislocation, grain boundary and interface of duplex SS in stress corrosion cracking(SCC)

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177775 ◽

1990 ◽

Vol 48 (4) ◽

pp. 928-929

Author(s):

Wang Zheng-fang ◽

Z.F. Wang

Keyword(s):

Stainless Steel ◽

Thermal Cycle ◽

Secondary Phase ◽

Corrosion Cracking ◽

Coarse Grained ◽

Test Environment ◽

Fine Grained ◽

Evaluation Test ◽

Welding Thermal Cycle ◽

Micro Analysis

The main purpose of this study highlights on the evaluation of chloride SCC resistance of the material,duplex stainless steel,OOCr18Ni5Mo3Si2 (18-5Mo) and its welded coarse grained zone(CGZ).18-5Mo is a dual phases (A+F) stainless steel with yield strength:512N/mm2 .The proportion of secondary Phase(A phase) accounts for 30-35% of the total with fine grained and homogeneously distributed A and F phases(Fig.1).After being welded by a specific welding thermal cycle to the material,i.e. Tmax=1350°C and t8/5=20s,microstructure may change from fine grained morphology to coarse grained morphology and from homogeneously distributed of A phase to a concentration of A phase(Fig.2).Meanwhile,the proportion of A phase reduced from 35% to 5-10°o.For this reason it is known as welded coarse grained zone(CGZ).In association with difference of microstructure between base metal and welded CGZ,so chloride SCC resistance also differ from each other.Test procedures:Constant load tensile test(CLTT) were performed for recording Esce-t curve by which corrosion cracking growth can be described, tf,fractured time,can also be recorded by the test which is taken as a electrochemical behavior and mechanical property for SCC resistance evaluation. Test environment:143°C boiling 42%MgCl2 solution is used.Besides, micro analysis were conducted with light microscopy(LM),SEM,TEM,and Auger energy spectrum(AES) so as to reveal the correlation between the data generated by the CLTT results and micro analysis.

Download Full-text

A preliminary study on the potential of front face fluorescence spectroscopy for the discrimination of Moroccan virgin olive oils and the prediction of their quality

Analytical Methods ◽

10.1039/d0ay01746a ◽

2021 ◽

Author(s):

Hicham Zaroual ◽

El Mestafa El Hadrami ◽

Romdhane Karoui

Keyword(s):

Fluorescence Spectroscopy ◽

Olive Oil ◽

Virgin Olive Oil ◽

Front Face ◽

Virgin Olive Oils ◽

Olive Oils ◽

Preliminary Study

This study examines the feasibility of using front face fluorescence spectroscopy (FFFS) to authenticate 41 virgin olive oil (VOO) samples collected from 5 regions in Morocco during 2 consecutive crop seasons.

Download Full-text