scholarly journals Field and Laboratory-based Approach for the Determination of Friction Angle of Geological Discontinuities of Malaysian Granites

2011 ◽  
Vol 28 (2) ◽  
pp. 151 ◽  
Author(s):  
R. A Ghani ◽  
T. L Goh ◽  
A. M Hariri ◽  
Y. N Baizura
Keyword(s):  
Friction Angle ◽  
Roughness Coefficient ◽  
Average Value ◽  
Peak Friction Angle ◽  
Maximum Value ◽  
Wide Range ◽  
Discontinuity Surfaces ◽  
Geological Discontinuities ◽  
Range Of Values

The basic friction angle, Φb for artificially sawn discontinuity planes for fresh granite, as determined by tilt testing, has an average value of 30º. For the natural rough discontinuity surfaces, a wide range of values have been determined for the peak friction angle, Φpeak ranging from 47º to a maximum value of 80º, depending on the joint roughness coefficient (JRC). The average values of the friction angles for the different degrees of roughness were as follows: JRC 2–4 = 58°; JRC 6–8 = 60°; JRC 8–10 = 47°; JRC 12–14 = 60°; JRC 14–16 = 71° ; JRC 18–20 = 80°.

Experimental determination of thermal conductivity of composite materials in a wide range of values at room temperature

2019 ◽  
Author(s):  
A.N. Chistov ◽  
M.Yu. Kladov ◽  
I.B. Pronin ◽  
A.S. Smirnov
Keyword(s):  
Thermal Conductivity ◽  
Composite Materials ◽  
Room Temperature ◽  
Measurement Procedure ◽  
Thermal Mode ◽  
Wide Range ◽  
Measurement Results ◽  
Transfer Problems ◽  
Range Of Values

In developing new composite materials and solving heat transfer problems, the thermal conductivity is an important characteristic that must be reliably determined. This often requires samples of the smallest dimensions, which is relevant for the production of pilot batches of material, as well as if they are taken directly from the product, when the amount of material is very limited. Most common methods for determining thermal conductivity require samples of relatively large sizes. To measure thermal conductivity on small-sized samples, an upgraded benchtop instrument is introduced. The instrument uses the relative method of longitudinal heat flux, which consists in a comparative measurement of a sample located between the heater and the standard in a stationary thermal mode. This paper presents the instrument design details, the requirements for the samples, explains the calibration features and the measurement procedure. The measurement results in a number of composite materials, as well as in materials with well-studied properties are analyzed. Findings show that the error of determining the thermal conductivity on a modernized instrument does not exceed several percent.

Free Molecule Flow Through a Vacuum Seal

1970 ◽  
Vol 92 (3) ◽  
pp. 405-410
Author(s):  
H. S. Yu ◽  
E. M. Sparrow
Keyword(s):  
Mass Flow ◽  
Numerical Solutions ◽  
Rarefied Gas ◽  
Coupled System ◽  
Mass Fluxes ◽  
Wide Range ◽  
Flow Through ◽  
Molecule Flow ◽  
Range Of Values

An analysis is made of the rate of the mass flow through a vacuum seal separating two rarefied gas environments. The determination of the mass throughflow characteristics involves the formulation and solution of a coupled system of six integral equations. The formulation is performed using the methods of kinetic theory. Numerical solutions are carried out for a wide range of values of the seal geometrical parameter. Mass flow results evaluated from these solutions are presented graphically. In addition, representative distributions of the mass fluxes at the participating surfaces are given.

scholarly journals The effects of grain size and different multi-stage shearing techniques on shear strength along rock discontinuities

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Alina Vattai ◽  
Nikoletta Rozgonyi-Boissinot
Keyword(s):  
Grain Size ◽  
Shear Strength ◽  
Normal Stress ◽  
Friction Angle ◽  
Coarse Grained ◽  
Roughness Coefficient ◽  
Peak Friction Angle ◽  
Grain Sizes ◽  
Multi Stage ◽  
Study Laboratory

AbstractThe effects of grain size and different multi-stage shearing techniques on shear strength along discontinuities were analyzed in this study. Laboratory direct shear tests were carried out on plaster mortar with maximum grain sizes of 0.5 mm and 1.0 mm. All specimen surfaces were essentially similar, copied from the same natural, Hungarian coarse-grained sandstone joint with a low joint roughness coefficient (JRC = 8). Tests within two different normal stress ranges (σn = 0.25–0.5 and 0.5–1.5 MPa) were performed simultaneously. Specimens tested using the technique involving modified shearing with repositioning were sheared three times while being subjected to the same degree of normal stress (shearing sequence n = 1, 2, 3) and those with multi-stage technique without repositioning were subjected to shearing once at three different degrees of normal stress. The changing values of the peak friction angle calculated from the resulting peak shear strength-normal stress data pairs (τp − σn) were examined. Failure curves were estimated using linear regression, according to the Mohr–Coulomb failure criterion. The differences between the various peak friction angles obtained from experiments in which different multi-stage shearing techniques were used tend to increase in significance with the increasing number of shearing sequences. Peak friction angle values vary according to grain size of the material, though further investigations using more grain sizes are required to establish the extent of the effect on shear strength along discontinuities.

scholarly journals Photogrammetric Prediction of Rock Fracture Properties and Validation with Metric Shear Tests

Geosciences ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 293
Author(s):  
Lauri Uotinen ◽  
Masoud Torkan ◽  
Alireza Baghbanan ◽  
Enrique Caballero Hernández ◽  
Mikael Rinne
Keyword(s):  
Shear Strength ◽  
Rock Fracture ◽  
Friction Angle ◽  
Jointed Rock ◽  
Roughness Coefficient ◽  
Rock Fractures ◽  
Shear Tests ◽  
Large Sample ◽  
Peak Friction Angle ◽  
Peak Shear Stress

An accurate understanding of jointed rock mass behavior is important in many applications ranging from deep geological disposal of nuclear waste, to deep mining, and to urban geoengineering projects. The roughness of rock fractures and the matching of the fracture surfaces are the key contributors to the shear strength of rock fractures. In this research, push shear tests with three normal stress levels of 3.6, 6.0, and 8.5 kPa were conducted on two granite samples with artificially induced well-matching tensile fractures with sizes of 500 mm × 250 mm and 1000 mm × 500 mm. The large sample reached on average a −60% weaker peak shear stress than the medium-sized sample, and a strong negative scale effect was observed in the peak shear strength. The roughness of the surfaces was measured using a profilometer and photogrammetry. The scale-corrected profilometer-based method (joint roughness coefficient, JRC) underestimates the peak friction angle for the medium-sized slabs by −27% for the medium sample and −9% for the large sample. The photogrammetry-based (Z′2) method produces an estimate with −7% (medium) and + 12% (large) errors. The photogrammetry-based Z′2 is an objective method that consistently produces usable estimates for the JRC and peak friction angle.

scholarly journals Determination of the Degree of Homogeneity for n Ge Crystals by Measurements of Magnetoresistance in Classically Weak Magnetic Fields

2015 ◽  
Vol 16 (3) ◽  
pp. 469-474
Author(s):  
G. P. Gaidar ◽  
P. I. Baranskii
Keyword(s):  
Spatial Distribution ◽  
Magnetic Fields ◽  
Crystallographic Orientation ◽  
Qualitative Assessment ◽  
Weak Magnetic Fields ◽  
Wide Range ◽  
The Relationship ◽  
Range Of Values ◽  
Degree Of Heterogeneity

In a wide range of values of the resistivity 0.0212 £ r £ 35 Ohm×cm for n‑Ge crystals with known crystallographic orientation the ratio , which was predicted by the theory, was experimentally confirmed. The experimentally measured deviations from the relationship , which are associated with the heterogeneity of the crystals, it is proposed to use for qualitative assessment of the degree of heterogeneity in the spatial distribution of dopants in the samples.

The interaction of falling water drops: coalescence

1972 ◽  
Vol 326 (1566) ◽  
pp. 393-408 ◽  
Keyword(s):  
Entire Range ◽  
Relative Velocity ◽  
Experimental Studies ◽  
Critical Value ◽  
Critical Conditions ◽  
Maximum Value ◽  
Satellite Drops ◽  
Wide Range ◽  
Water Drops ◽  
Range Of Values

Experimental studies have been conducted of the interaction of falling water drops of radii R and r (R > r ), density p and surface tension σ colliding in air with a relative velocity U and a perpendicular distance X between the centre of one drop and the undeflected trajectory of the other. R and r were varied from 150 to 750 μm, R/r from 1.0 to 2.5, U from 0.3 to 3.0 m s -1 and X from 0 (head-on collisions) to the maximum value for contact, R + r. Four types of interaction were observed: (1) bouncing; (2) permanent coalescence; (3) coalescence followed by separation; (4) coalescence followed by separation and the formation of satellite drops. The principal effort was devoted to a study of the critical conditions under which drops will separate after coalescence. It was found that there was a critical value of X, denoted by X c , below which the coalesced drops remained united and above which there was sufficient angular momentum for the drops to separate after coalescence. For a wide range of values of r, R and U the coalescence efficiency e = X e /(R + r) 2 was found to lie between 0.1 and 0.4 for drops of identical size and about 0.2 and 0.6 for drops with R/r = 2.0. A theoretical analysis based on energy concepts predicted that the coalescence efficiency is given by the equation where f(R/r) is a function which varies from 1.3 for R/r = 1 and 3.8 for R/r = 3. The predictions of this equation were in excellent agreement with the experimental results over the entire range of conditions studied. Investigations are also described of the critical conditions for the bouncing of colliding drops, the influence of electric charges upon the interactions and the elongation and splitting of a rotating drop.

Polarimetric and photometric studies of lunar samples

1977 ◽  
Vol 285 (1327) ◽  
pp. 397-402 ◽  
Keyword(s):  
Phase Angle ◽  
Scattered Light ◽  
Degree Of Polarization ◽  
Surface Textures ◽  
Versus Phase ◽  
Maximum Value ◽  
Planetary Satellites ◽  
Wide Range ◽  
Lunar Samples

The polarization of scattered light has been investigated for lunar samples from six Apollo and two Luna missions. Over a wide range of the phase angle between incidence and observation directions, the light is found to be polarized only either normal (called positive) or parallel (negative) with respect to the incidence/observation plane. The resulting characteristic curves, of degree of polarization versus phase angle, are indicative of surface properties: the maximum value of polarization is inversely proportional to albedo, for dust-covered surfaces, and the slope is inversely proportional to albedo for most surfaces; the width and depth of the negative-going part of the curve indicate the type and complexity of the surface texture, as confirmed by Stereoscan photographs. This information may now be applied to the determination of albedos and surface textures for objects such as asteroids and planetary satellites, for which no samples are available but for which some polarization measurements have been made.

scholarly journals Determination of Passive Failure Surface Geometry for Cohesionless Backfills

2020 ◽  
Author(s):  
Behzad Soltanbeigi ◽  
Adlen Altunbas ◽  
Ahmet Talha Gezgin ◽  
Ozer Cinicioglu
Keyword(s):  
Relative Density ◽  
Failure Surface ◽  
Friction Angle ◽  
Model Tests ◽  
Small Scale ◽  
Geometrical Parameters ◽  
Surface Geometry ◽  
Peak Friction Angle ◽  
Non Linear

Correct determination of the passive failure surface geometry is necessary for the design of retaining structures. The conventional theories assume linear passive failure surfaces even though it is known that the actual failure surfaces are non-linear. Many researchers claimed the appropriateness of a hybrid curved-linear method. This approach estimates the curved section by a log-spiral function, which then connects to the backfill surface with the conventional linear assumption. The main drawback here is that the geometric properties of the hybrid mathematical function is not directly related to the mechanical properties of soils. Thus, this study attempts to provide a mechanical description for the assumed geometrical parameters. For this purpose, a series of 1 g small scale retaining wall model tests, simulating passive failure, are conducted on two different backfill soils. The relative density is varied in the model tests and the resultant peak friction angles of the backfills are calculated as functions of failure stress state and relative density using a well-known empirical equation. Transparent sidewalls allow for visualization of the failure surface evolution, which is obtained by capturing images and analysing then through Particle Image Velocimetry (PIV) technique. Subsequently, the quantified slip zones are fitted with the hybrid curved-linear approach. The relationships between the peak friction angle and the geometrical characteristics of the best-fit log-spiral and linear functions are investigated. Obtained results are used to propose a set of equations that allow the estimation of non-linear passive failure surfaces as function of peak friction angle.

scholarly journals Determination of soil and ground sealing in functional zones of Volgograd based on remote sensing data

2021 ◽  
pp. 116-138
Author(s):  
O. A. Gordienko
Keyword(s):  
Urban Areas ◽  
Remote Sensing Data ◽  
Likelihood Method ◽  
Territorial Planning ◽  
Automated Method ◽  
Wide Range ◽  
Functional Zones ◽  
The City ◽  
Range Of Values

The paper presents the results of interpretation of sealed soils and ground for the territory of Volgograd and its various functional zones. Determination of the sealed portion was performed by means of automated method using ENVI 4.7 software by means of QuickBird space image classification using the “maximum likelihood” method. The study objects were the territories of all districts of Volgograd, as well as residential and recreational functional zones. It was found that the sealed surfaces occupy about 169.4 km2 (20.5% of the total area of the city). However, the city districts and functional zones differ significantly in proportion of sealed areas. The most sealed surfaces were those of Tractorozavodsky (24.2%), Voroshilovsky (33.0%), Dzerzhinsky (37.4%), Centralny (45.2%), Krasnooktyabrsky (39.4%) and Krasnoarmeisky (26.6%) districts of Volgograd. Soil cover of the Sovetsky (13.5%) and Kirovsky (12.9%) districts is least sealed. Sealing of functional zones also varies widely. Thus, the highest values of sealing (up to 63%) characterize the multi-, low- and medium-rise constructions zones. A wide range of values (from 26 to 51%) corresponds to the areas of individual residential development, as well as collective gardens and dachas (from 9.6 to 39.5%). In the recreational zone average sealing is at 27.6% level. Thus, the identified share of sealed surfaces on the territory of Volgograd and its functional zones will allow solving effectively the problems of territorial planning in the further implementation of works on gardening and landscaping of urban areas.

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