Investigation of Weak Sandstones

1986 ◽  
Vol 2 (1) ◽  
pp. 199-205
Author(s):  
L. Dobereiner ◽  
M. H. de Freitas
Keyword(s):  
Compressive Strength ◽  
Moisture Content ◽  
Uniaxial Compressive Strength ◽  
Wave Velocity ◽  
Compressional Wave ◽  
Weak Rock ◽  
Index Test ◽  
Compressional Wave Velocity ◽  
Compressional Waves ◽  
Weak Sandstone

AbstractIt is proposed that coverage of the class of material described in BS 5930 as weak rock, is in need of improvement.Results from research into the behaviour of weak sandstone (0.5-20 MPa uniaxial compressive strength) are presented to illustrate this need. The strength, deformability, and propagation of compressional waves are reported for weak sandstones and recommendations presented for describing these materials and for testing their strength and deformability. Problems associated with the measurement of compressional wave velocity are also considered.An index test for assessing the strength of weak sandstone (the index of vacuum saturated moisture content) is described and presented.

Seismic refraction shooting in an area of the Eastern Atlantic

1952 ◽  
Vol 244 (890) ◽  
pp. 561-594 ◽  
Keyword(s):  
Wave Velocity ◽  
Deep Sea ◽  
Sea Water ◽  
Seismic Refraction ◽  
Compressional Wave ◽  
Crystalline Rock ◽  
Compressional Wave Velocity ◽  
Compressional Waves ◽  
A Value ◽  
Sedimentary Layer

For the experiments described in this paper a new method of seismic refraction shooting was developed. With this method hydrophones suspended at a depth of about 100 ft. below the surface of the sea acted as receivers for the compressional waves developed by depth charges exploding at a depth of approximately 900 ft. The hydrophones were connected with sono-radio buoys which radio-transmitted the electrical signals to a recording system in the ship from which the charges were dropped. Four buoys were in use simultaneously, distributed at differing ranges from the ship. The experiments were carried out at three positions in an area of the eastern Atlantic around the point 53° 50' N, 18° 40' W, where the water depth is approximately 1300 fm. (2400 m). The results showed that the uncrystalline sedimentary layer in this area varied in thickness from 6200 ft. to 9700 ft. (1900 to 3000 m), and that the velocity of compressional waves in it increased from the value for sea water, 4900 ft./s (1.5 km/s), at the surface with an approximately constant gradient of 2.5/s to a limiting value of 8200 ft./s (2.5 km/s). Below the sedimentary layer there was a crystalline rock with compressional wave velocity of approximately 16500 ft./s (5.0 km/s) and of thickness varying between 8800 ft. (2700 m) and 11100 ft. (3400 m). The base of this layer was in both determinations at approximately 25500 ft. (7800 m) below sea-level. The lowest layer concerning which information was obtained gave a value for the compressional wave velocity of about 20500 ft./s (6.3 km/s), but was of undetermined thickness. The characteristics of the sedimentary layer were such as might be expected for a continuous succession of deep-sea sediments, the thickness on this basis being such as to indicate the long existence of the ocean in this area. On the other hand, it is possible that it represents a downwarped continental shelf. The layer below the sedimentary layer has a compressional wave velocity which is low for an igneous rock at this depth, and it is probable that it represents a crystalline sedimentary rock. From the evidence it is not possible to determine whether this rock is of continental or deep-sea origin. The lowest layer of these experiments is unlikely to have a constitution similar to that of the European granitic layer, since the compressional wave velocity in it would, on this hypothesis, be exceptionally high. The value is, however, close to that calculated by Jeffreys for the intermediate layer.

VELOCITY OF COMPRESSIONAL WAVES IN POROUS MEDIA AT PERMAFROST TEMPERATURES

Geophysics ◽  
1968 ◽  
Vol 33 (4) ◽  
pp. 584-595 ◽  
Author(s):  
A. Timur
Keyword(s):  
Porous Media ◽  
Wave Velocity ◽  
Compressional Wave ◽  
Freezing Process ◽  
Rock Matrix ◽  
Compressional Wave Velocity ◽  
Compressional Waves ◽  
Average Equation ◽  
Wave Velocities ◽  
Time Average

Measurements of velocity of compressional waves in consolidated porous media, conducted within a temperature range of 26 °C to −36 °C, indicate that: (1) compressional wave velocity in water‐saturated rocks increases with decreasing temperature whereas it is nearly independent of temperature in dry rocks; (2) the shapes of the velocity versus temperature curves are functions of lithology, pore structure, and the nature of the interstitial fluids. As a saturated rock sample is cooled below 0 °C, the liquid in pore spaces with smaller surface‐to‐volume ratios (larger pores) begins to freeze and the liquid salinity controls the freezing process. As the temperature is decreased further, a point is reached where the surface‐to‐volume ratio in the remaining pore spaces is large enough to affect the freezing process, which is completed at the cryohydric temperature of the salts‐water system. In the ice‐liquid‐rock matrix system, present during freezing, a three‐phase, time‐average equation may be used to estimate the compressional wave velocities. Below the cryohydric temperature, elastic wave propagation takes place in a solid‐solid system consisting of ice and rock matrix. In this frozen state, the compressional wave velocity remains constant, has its maximum value, and may be estimated through use of the two‐phase time average equation. Limited field data for compressional wave velocities in permafrost indicate that pore spaces in permafrost contain not only liquid and ice, but also gas. Therefore, before attempting to make velocity estimates through the time‐average equations, the natures and percentages of pore saturants should be investigated.

scholarly journals Predicting Unconfined Compressive Strength Decrease of Carbonate Building Materials against Frost Attack Using Nondestructive Physical Tests

2020 ◽  
Vol 12 (4) ◽  
pp. 1379 ◽  
Author(s):  
Marzouk Mohamed Aly Abdelhamid ◽  
Dong Li ◽  
Gaofeng Ren
Keyword(s):  
Compressive Strength ◽  
Wave Velocity ◽  
Unconfined Compressive Strength ◽  
Building Materials ◽  
Construction Materials ◽  
Strong Relationship ◽  
Compressional Wave ◽  
Compressional Wave Velocity ◽  
Frost Weathering ◽  
Spatial Attenuation

Carbonate building materials and engineering constructions are exposed to severe seasonal environmental fluctuations and result in a full or partial disintegration, especially in cold regions, and employment of nondestructive methods for evaluating the durability of building materials subject to frost weathering is gaining great significance. This research aims to obtain reliable relationships between unconfined compressive strength decrease and nondestructive parameters variations of limestone types under frost conditions and provide useful information regarding their durability in order to ensure the long-term viability or sustainability of these materials used for constructions against frost conditions. In this study, five important types of Chinese limestone used as construction materials were subjected to 50 frost cycles. Unconfined compressive strength, compressional wave velocity and spatial attenuation, and porosity were obtained at the end of every 10 cycles. As a result of progression in frost cycles, the increase and decrease rates were determined at the end of every 10 cycles, and the relationships between them were obtained to predict the loss ratios of unconfined compressive strength (RDσc). Results indicated that at the end of 40th cycles, there was a high correlation between RDσc and spatial attenuation loss with an R2 of 0.8584. Furthermore, there was also a strong relationship between RDσc and compressional wave velocity decrease after the end of 20th and 50th cycles with an R2 of 0.9089 and 0.9025, respectively. Therefore, these relations are reliable to provide useful information for durability and viability of studied samples under frost conditions and support the use of the ultrasonic measurements. It can also be successfully used for pre-estimation of unconfined compressive strength loss of studied limestone types against frost weathering without any tests.

THE PROPAGATION OF THE COMPRESSIONAL WAVE IN THE CRUST: II. SYNTHETIC SEISMOGRAMS

1965 ◽  
Vol 2 (6) ◽  
pp. 560-576 ◽  
Author(s):  
M. J. Keen ◽  
C. F. Tsong
Keyword(s):  
Nova Scotia ◽  
Wave Velocity ◽  
Atlantic Coast ◽  
Compressional Wave ◽  
Synthetic Seismograms ◽  
The Other ◽  
Compressional Wave Velocity ◽  
Compressional Waves ◽  
The One

Synthetic seismograms have been generated in an attempt to measure the attenuation of compressional waves beneath the Atlantic coast of Nova Scotia; the results suggest that the value of Q must be of the order of 300 whatever the mechanism of propagation may be. Comparison with results of experiments in the Gulf of St. Lawrence shows that attenuation of first events in the range of distance up to 60 km is more rapid in the rocks beneath the Gulf than in those beneath the Atlantic coast of Nova Scotia, This may be due either to attenuation in the upper sedimentary layers, present in the one place but not in the other, or to greater attenuation within rocks in which the compressional wave velocity is the same as in those beneath the Atlantic coast.

On: “EFFECT OF POROSITY, GRAIN CONTACTS, AND CEMENT ON COMPRESSIONAL WAVE VELOCITY THROUGH SYNTHETIC SANDSTONES” BY ANDRIS VIKSNE, JOSEPH W. BERG, JR., and KENNETH L. COOK (GEOPHYSICS, FEBRUARY, 1961, PP. 77–84).

Geophysics ◽  
1962 ◽  
Vol 27 (5) ◽  
pp. 720-721
Author(s):  
L. P. Stephenson ◽  
R. D Tooley
Keyword(s):  
Experimental Data ◽  
Wave Velocity ◽  
Cement Content ◽  
Compressional Wave ◽  
Experimental Measurements ◽  
Compressional Wave Velocity ◽  
Rigorous Analysis ◽  
Compressional Waves

The experimental data reported by Viksne, Berg, and Cook have been reinterpreted in the light of a more rigorous analysis of the variables. Since the experimentally determined velocities of compressional waves in the synthetic cores can be described analytically in terms of the porosity and cement content alone with an accuracy comparable to that expected of the experimental measurements, it is not possible to establish what influence manufacturing pressure may have on velocity (other than that resulting from its effect on porosity). In particular, it cannot be said that the reported experiments have demonstrated that grain‐to‐grain contacts affect the velocity in any way. These conclusions are substantially different from those drawn from the same data by Viksne, Berg, and Cook.

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