ON THE PARTICLE CRUSHING FEATURES OF SANDY SOILS

2020 ◽  
Vol 7 (2) ◽  
Author(s):  
Haruyuki Yamamoto
Keyword(s):  
High Pressure ◽  
Volumetric Strain ◽  
Sandy Soils ◽  
Deviatoric Stress ◽  
Volume Shrinkage ◽  
Silica Sand ◽  
Mean Stress ◽  
Stress Tests ◽  
Particle Crushing ◽  
Weathered Granite

Previous studies have investigated particle crushing of sandy soils in high-pressure conditions. In practice, the volume shrinkage and decreasing shear strength due to particle crushing around the pile-foundation tip in crushable sandy soils may be more important. Therefore, this study aims to confirm the volume shrinkage of sandy soils, e.g., silica sand, weathered granite, and volcanic sand, under various stress paths with a combination of high principal stresses. High-pressure crushing tests were carried out using a true tri-axial compression apparatus under the planned stress paths. Isotropic compression tests and combined stress tests (mean stress p and deviatoric stress q) were employed for three types of sandy soil. The particle-crushing progress became active in combination with mean stress p and deviatoric stress q. In addition, the relationships between the plastic volumetric strain and relative breakage were found to be approximately linear. As expected, the silica sand was less crushable than the weathered granite sand and volcanic sand under the same stress conditions.

ON THE SHEAR STIFFNESS DECREASE OF SANDY SOILS DUE TO PARTICLE CRUSHING PROGRESS

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
haruyuki yamamoto
Keyword(s):  
High Pressure ◽  
Sandy Soil ◽  
Shear Failure ◽  
Sandy Soils ◽  
Shear Stiffness ◽  
Deviatoric Stress ◽  
Mean Stress ◽  
Particle Crushing ◽  
Soil Particles ◽  
The Mean

Many previous studies have focused on theoretical and experimental evaluations of the crushing of sandy soil particles under high pressure conditions. From the perspective of practical scenarios, the decreased bearing capacity caused by volume shrinkage and the reduced shear strength and stiffness caused by the crushing of sandy soil particles are important aspects. Therefore, this study aims to confirm the decrease in the shear stiffness of sandy soils subjected to various stress levels combined with high principal stresses. Author conducted crushing tests using the high-pressure true tri-axial compression apparatus under the planned stress paths. Tests on isotropic compression without deviatoric stress q and those involving combinations of the mean stress p and deviatoric stress q up to the shear failure line (SFL) on the p-q plane are employed to characterize the particle crushing of sandy soils. The results indicate that the shear stiffness of sandy soils starts to decrease due to particle crushing under a combination of low mean stress p and high deviatoric stress q. Furthermore, experimental formulas regarding the decrease in shear stiffness due to particle crushing were estimated based on the relationships among the mean stress p, deviatoric stress q and deviatoric strain εd.

scholarly journals Application Ranges of EPB Shield TBM in Weathered Granite Soil: A Laboratory Scale Study

2021 ◽  
Vol 11 (7) ◽  
pp. 2995
Author(s):  
Tae-Hwan Kim ◽  
In-Mo Lee ◽  
Hee-Young Chung ◽  
Jeong-Jun Park ◽  
Young-Moo Ryu
Keyword(s):  
Water Content ◽  
Upper And Lower Bounds ◽  
Shield Tunnel ◽  
Particle Crushing ◽  
Pressure Balance ◽  
Soil Conditioning ◽  
Weathered Granite ◽  
Weathered Granite Soil ◽  
Granite Soil ◽  
Epb Shield

Soil conditioning is a key factor in increasing tunnel face stability and extraction efficiency of excavated soil when excavating tunnels using an earth pressure balance (EPB) shield tunnel boring machine (TBM). Weathered granite soil, which is abundant in the Korean Peninsula (also in Japan, Hong Kong, and Singapore), has different characteristics than sand and clay; it also has particle-crushing characteristics. Conditioning agents were mixed with weathered granite soils of different individual particle-size gradations, and three characteristics (workability, permeability, and compressibility) were evaluated to find an optimal conditioning method. The lower and upper bounds of the water content that are needed for a well-functioning EPB shield TBM were also proposed. Through a trial-and-error experimental analysis, it was confirmed that soil conditioning using foam only was possible when the water content was controlled within the allowable range, that is, between the upper and lower bounds; when water content exceeded the upper bound, soil conditioning with solidification agents was needed along with foam. By taking advantage of the particle-crushing characteristics of the weathered granite soil, it was feasible to adopt the EPB shield TBM even when the soil was extremely coarse and cohesionless by conditioning with polymer slurries along with foam. Finally, the application ranges of EPB shield TBM in weathered granite soil were proposed; the newly proposed ranges are wider and expanded to coarser zones compared with those proposed so far.

scholarly journals Environmental effects on efficacy of herbicides for postemergence goosegrass (Eleusine indica) control

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Avat Shekoofa ◽  
James T. Brosnan ◽  
Jose J. Vargas ◽  
Daniel P. Tuck ◽  
Matthew T. Elmore
Keyword(s):  
Soil Moisture ◽  
Environmental Effects ◽  
Vapor Pressure Deficit ◽  
Sandy Soils ◽  
Silica Sand ◽  
Soil Drying ◽  
Silt Loam ◽  
Evaporative Demand ◽  
Eleusine Indica ◽  
High Soil Moisture

AbstractExperiments were conducted to understand environmental effects on efficacy of herbicides used to control goosegrass (Eleusine indica L. Gaertn.). Herbicides were applied to goosegrass maintained at soil moisture contents (VMC) of < 12%, 12 to 20%, or > 20%. Herbicides included fenoxaprop-p-ethyl (140 g ha−1), topramezone (25 g ha−1), foramsulfuron (44 g ha−1), 2,4-D + dicamba + MCPP + carfentrazone (860 + 80 + 270 + 28 g ha−1), and thiencarbazone-methyl + foramsulfuron + halosulfuron-methyl (22 + 45 + 69 g ha−1). Goosegrass control increased as VMC increased. Vapor pressure deficit (VPD) and air temperature were manipulated to determine effects of evaporative demand on foramsulfuron. Effects of soil drying were also studied following foramsulfuron application. Reductions in transpiration rate (TR) and leaf area were greatest with foramsulfuron applications to goosegrass in silt-loam under high evaporative demand (3 kPa VPD, 38 °C). Foramsulfuron had no effect on goosegrass in silica-sand regardless of evaporative demand. TR dropped to 0.2 mmh−1 within eight days after application to goosegrass in silt-loam compared to 18 days in silica-sand. Overall, foramsulfuron efficacy on goosegrass was maximized under conditions of high soil moisture and evaporative demand, and may be reduced in sandy soils that hold less water.

Evolution of Meso-Structure of Intact Loess during Wetting

2012 ◽  
Vol 204-208 ◽  
pp. 188-191
Author(s):  
Xiang Wei Fang ◽  
Chun Ni Shen ◽  
Pei Jiang Cheng ◽  
Long Wang
Keyword(s):  
Volumetric Strain ◽  
Ct Images ◽  
Deviatoric Stress ◽  
Cell Stress ◽  
Degree Of Saturation ◽  
Triaxial Apparatus ◽  
Evolution Of Structure ◽  
Ct Data ◽  
Intact Loess

To study the evolution of meso-structure of unsaturated intact loess during wetting, a series of CT-triaxial-collapse tests were conducted using CT-multi-function triaxial apparatus. The distinct CT images and detailed CT data were attained nondestructively during wetting. A parameter and an evolution variable which characterized evolution of meso-structure were defined based CT data. An equation describing the evolution of structure during wetting was proposed. The equation reflected the influences of net cell stress, deviatoric stress and suction on the evolution of meso-structure. In the equation, volumetric strain, deviatoric strain and incremental degree of saturation are included.

Comparative study of coral sand and silica sand in creep under general stress states

2017 ◽  
Vol 54 (11) ◽  
pp. 1601-1611 ◽  
Author(s):  
Yaru Lv ◽  
Feng Li ◽  
Yawen Liu ◽  
Pengxian Fan ◽  
Mingyang Wang
Keyword(s):  
Grain Size ◽  
Creep Behavior ◽  
Confining Pressure ◽  
Silica Sand ◽  
Triaxial Tests ◽  
Particle Crushing ◽  
Particle Rotation ◽  
General Stress ◽  
Coral Sand ◽  
Stress States

Coral sand has individual characteristics that differ from silica sand, such as creep behavior that is always attributed to particle crushing under high stress states. To understand the creep behavior of coral sand under general stress levels, three series of comparative triaxial tests relevant to the deviator stress, confining pressure, and relative density were performed on coral sand and silica sand creeping for more than 5 days. The volumetric, axial, and shear creeps of coral sand are considerably larger than those of silica sand, particularly under a relatively high confining pressure. The volumetric creep strain of coral sand was found to be contractive, but that of silica sand appeared dilative according to the creep time. This difference is not mainly governed by particle crushing in coral sand because the grain-size distribution prior to and after creep is similar. The grain skeletons were observed using a scanning electron microscope, finding that, independent of the grain size and shape, the coral grains include large amounts of cavities. The creep of coral sand under general stress conditions is mainly caused by particle interlocking, i.e., the angular regions of some particles interlock into the cavities of other particles due to particle rotation. This structuration is induced by breakage of asperities and voids during creep such as the local instability near cavities.

Case Study on the Effect of Mean Stress on Ground Storage Vessels for Fuelling

2019 ◽  
Author(s):  
Daniel T. Peters ◽  
Myles Parr ◽  
Matthew Naugle
Keyword(s):  
High Pressure ◽  
Natural Gas ◽  
Gas Storage ◽  
Pressure Vessels ◽  
Lower Pressure ◽  
Mean Stress ◽  
Gaseous Fuels ◽  
Design Pressure

Abstract The use of high-pressure vessels for the purpose of storing gaseous fuels for land based transportation application is becoming common. Fuels such as natural gas and hydrogen are currently being stored at high pressure for use in fueling stations. This paper will investigate the use of autofrettage in high pressure cylinders and its effects on the life of a vessel used for gas storage. Unlike many high-pressure vessels, the life is controlled by fatigue when cycled between a high pressure near the design pressure and a lower pressure due to the emptying of the content of the vessels.

scholarly journals The influence of particle breakage on stress-dilatancy relationship for granular soils

2019 ◽  
Vol 92 ◽  
pp. 09004 ◽  
Author(s):  
Zenon Szypcio
Keyword(s):  
Internal Energy ◽  
Stress Level ◽  
Triaxial Compression ◽  
Volumetric Strain ◽  
Stress Path ◽  
State Theory ◽  
Particle Breakage ◽  
Compression Tests ◽  
Particle Crushing ◽  
Soil Gradation

The influence of particle breakage on soil behaviour is important from theoretical and practical perspectives. Particle breakage changes the internal energy in two ways. First, internal energy is consumed for particle crushing and second, the internal energy changes because of additional volumetric strain caused by particle crushing. These two effects may be quantified by use of Frictional State Theory. The analysed drained triaxial compression tests of Toyoura sand, gravel and Dog's Bay sand at different stress level and stress path revealed that the effect of particle breakage is a function of soil gradation, strength of soil grains, stress level and stress path.

Experimental study of the effect of stress on α → β quartz transformation at lower continental crust pressure and temperature conditions

2020 ◽  
Author(s):  
Arefeh Moarefvand ◽  
Julien Gasc ◽  
Julien Fauconnier ◽  
Damien Deldicque ◽  
Loic Labrousse ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Continental Crust ◽  
Elastic Properties ◽  
Deviatoric Stress ◽  
P Wave ◽  
Time Shift ◽  
Monitoring Method ◽  
Lower Continental Crust ◽  
Temperature Conditions

&lt;p&gt;Based on experimental observations, there have been claims that deviatoric stresses may trigger high pressure phase transitions below their equilibrium transition pressures. This implies that the phase assemblages observed in exhumed rocks may reflect stresses induced by tectonic overpressure rather than mere lithostatic pressure, thus resulting in overestimated maximum depths of burial. Despite the numerous studies that have addressed whether mean or principal stress may trigger polymorphic phase changes, the case is still not completely clear. The aim of this study is therefore to investigate the role of deviatoric stress on phase transitions at high PT conditions. In this study, we investigated the &amp;#945;-&amp;#946; transition of quartz, which is one of the most common mineral of the Earth&amp;#8217;s crust. This transition has a particular importance for the lower continental crust because of the significantly different elastic properties of the two polymorphs. The &amp;#945;-&amp;#946; quartz transition is also a good experimental candidate because of its displacive and quasi-instantaneous nature.&lt;/p&gt;&lt;p&gt;A series of experiments was performed with a new high pressure Griggs-type apparatus equipped with ultrasonic monitoring, at the ENS Paris. Cored rock samples of Arkansas Novaculite (mean grain size of 5.6 mm) were subjected to pressure and temperature conditions of 0.5-1.5 GPa and ~ 850 &amp;#176;C. The deviatoric stress was increased to cross the transition while keeping the temperature constant. Two p-wave transducers were used on top and bottom of the assembly as transmitter and receiver to measure travel times across the assembly. The quartz a-b transition was directly observed by a time-shift of the p-wave arrival in the order of 10 ns. The mechanical data clearly show that the phase transformation is controlled by mean stress. The quartz &amp;#945;-&amp;#946; transition induces a softening behavior on our sample because of the volume change induced by the reaction. According to the elastic properties of &amp;#945; and &amp;#946; quartz, the variation of p wave velocity for the quartz &amp;#945;-&amp;#946; transition is in the order of 10 %. The present active monitoring method allowed us to detect variations smaller than 5 %, which can be explained by a partial transformation due to local stress heterogeneities in the sample, since microscopic stress at the grain scale can be different than the macroscopic stress that we measure.&lt;/p&gt;

CRUSHING CHARACTERISTICS OF SOIL PARTICLE ON THE EFFECT OF STRESS PATH

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Keigo Fukuda ◽  
Haruyuki Yamamoto
Keyword(s):  
Axial Compression ◽  
Mechanical Characteristics ◽  
Shear Failure ◽  
Stress Path ◽  
Deviatoric Stress ◽  
Particle Crushing ◽  
Principal Stresses ◽  
The Mean ◽  
Lode Angle ◽  
Failure Line

In previous studies, we have conducted tests under various conditions of stress for the particle crushing. Anyway, it is necessary to perform the crushing test that assumed stress conditions in ground under controlled each principal stresses individually, to find the mechanical characteristics of the soil with particle crushing. Therefore, the purpose of this study is to confirm the effect for particle crushing under various stress paths in the combination of principal stresses. We planned four combinations of principal stresses when operate the mean stress p and deviatoric stress q up to the Shear Failure Line (SFL) on the 𝜋-plane. First, we set tri-axial extension test as Lode angle 𝛳=60° and tri-axial compression test as 𝛳=0°, and set two of the remainder as 𝛳=40°, 20°. The crushing tests are carried out using the high pressure true tri-axial compression apparatus under the planned stress paths. As a result, the progress of the particle crushing becomes active in order of 𝛳=40°, 20°, 60°, 0°, and found out that deviatoric stress q has essential effect on the particle crushing.

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