scholarly journals Short Note on Slab-Avalanche Measurements

1978 ◽  
Vol 20 (82) ◽  
pp. 221-222
Author(s):  
R. Perla

AbstractFrom a study of 205 slab avalanches it is concluded that failure initiates where the slope is 25° or steeper, that slab failure stress is in the range 102N m-2 to 104N m-2, and that the slab failure plane is most commonly at a temperature of -5°C or warmer. The study also indicates that the shear strength of weak layers varies approximately as the square of the density.

1978 ◽  
Vol 20 (82) ◽  
pp. 221-222
Author(s):  
R. Perla

Abstract From a study of 205 slab avalanches it is concluded that failure initiates where the slope is 25° or steeper, that slab failure stress is in the range 102N m-2 to 104N m-2, and that the slab failure plane is most commonly at a temperature of -5°C or warmer. The study also indicates that the shear strength of weak layers varies approximately as the square of the density.


1977 ◽  
Vol 14 (2) ◽  
pp. 206-213 ◽  
Author(s):  
R. Perla

From a study of 205 slab avalanches it is concluded that failure initiates where the slope is 25° or steeper, that slab failure stress is in the range 102–104 N/m2, and that the slab failure plane is most commonly at a temperature of −5 °C or warmer.The in situ measurement of shear strength is still an unresolved problem. A statistical analysis of a shear-frame device shows that the device is sensitive to the rate of pull and to the frame area. The larger the frame area, the smaller the measured shear strength. Approximately 10 measurements are required to sample a mean shear strength of a slab failure plane to within 15% accuracy at 90% confidence.


2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Bo Meng ◽  
Hongwen Jing ◽  
Shengqi Yang ◽  
Yingchao Wang ◽  
Biao Li

The shear behavior of concrete blocks reinforced by fully grouted bolts with different diameters was studied in this paper. More than 90 intact cubic samples (100 mm × 100 mm × 100 mm) with bolts ranging from 2 mm to 5 mm in diameter were tested at a constant stain rate of 0.5 mm/min. An oblique shear apparatus, which could simultaneously apply shear and normal force on tested samples at three slope angles (53°, 58°, and 63°) of a predetermined shear plane, was employed. The results indicate that the bolt has no evident influence on the shear behavior of intact concrete blocks at the prepeak shear strength stage. The bolt could significantly reduce the shear strength drop in the peak shear strength of the concrete block and contribute to reserving the residual shear strength of concrete blocks, especially at steep slope angles of the shear failure plane. The shear resistance provided by the bolt to the concrete block at the residual shear slip stage has a positive relationship with the diameter. The bolt with a larger diameter inflected in the vicinity of the shear failure plane of concrete block at the postpeak shear strength stage; additional normal force and direct shear resistance could still be persistently provided. Two empirical equations of the apparent cohesion and apparent internal angle of the bolted concrete block were obtained by linear regression considering rb, which is the ratio of the cross-sectional area of the bolt to that of the bolted concrete block.


1998 ◽  
Vol 25 (3) ◽  
pp. 437-450 ◽  
Author(s):  
Robert E Loov

A review of the so-called simplified method of shear design described in CSA A23.3-94 "Design of concrete structures" shows that the method is not simple. The designer is required to check numerous equations and limits. The resulting relation between stirrup spacing and shear strength is found to be an extremely complex line resulting from the intersection of seven separate surfaces. A shear friction model has been developed which seems to predict the shear strength of beams rather well. Stirrups and longitudinal reinforcement provide a clamping force thereby increasing the friction force which can be transferred across a crack along a potential failure plane. This model is based on the shear strength after cracking so that no diagonal tension strength is included. The shear friction model has been used as the basis for determining approximate equations for maximum stirrup spacing. A comparison of these approximate shear friction predictions with those using the simplified method indicates a high degree of correlation but many important differences. It seems that shear design can be clarified as well as simplified by adoption of the shear friction approach.Key words: reinforced concrete, shear, shear friction, shear tests, stirrup spacing.


Author(s):  
N. Matasovic ◽  
C. Conkle ◽  
A. F. Witthoeft ◽  
A. Stern ◽  
T. Hadj-Hamou

1974 ◽  
Vol 11 (3) ◽  
pp. 430-437 ◽  
Author(s):  
A. K. Loh ◽  
R. T. Holt

The undrained shear strength and the fabric of a lacustrine clay from Winnipeg, Manitoba, have been determined with respect to the orientation of the natural bedding plane. Unconfined compression tests show that both the undrained shear strength and the normalized secant modulus of 'undisturbed' clay were anisotropic. The fabric, determined by X-ray diffraction analysis, was also found to be anisotropic in the 'undisturbed' samples. The same material in the remolded condition was isotropic with respect to both undrained shear strength and fabric. Observations of the failure plane have been used to calculate the resolved shear stress on the failure plane, and the results agree qualitatively with prediction, according to Jaeger's weak plane hypothesis. The variation of undrained shear strength with orientation may be due to (1) the clay fabric and (2) stratification, although these two factors may be interdependent.


2021 ◽  
Vol 11 (3) ◽  
pp. 1086
Author(s):  
Atsushi Takano ◽  
Chao Li ◽  
Ryuta Kitamura

Strength tests on single lap joints with one adhesive (AV138/HV998) and one adhesive layer thickness (0.5 mm), three peel stoppers (brass bolt, nylon bolt and steel pin), and four lap lengths (12.5 mm, 25 mm, 40 mm and 100 mm) were conducted to investigate the effects of varying the lap length and stiffness of the peel-stop fasteners. Joint failure stress decreased, but failure force increased with lap length. Furthermore, joint failure stress was higher with the peel stopper. The effect of the brass-bolt peel stoppers was significant, whereas the effects of the nylon bolts and steel pins were smaller than that of the brass bolts. This indicates that the axial clamp strength and stiffness of the peel stopper are important factors in the shear strength of the lap. In addition, the effect of the stopper was negligible for the 12.5 mm lap. The reason is that the shear strength in the case of the 12.5 mm lap was large and thus the effect of the peel stopper was comparatively small. Moreover, the strength of the 100 mm lap reached the adherent material’s strength.


1983 ◽  
Vol 29 (103) ◽  
pp. 485-491 ◽  
Author(s):  
R. Perla ◽  
T. M. H. Beck

AbstractThe shear frame is a simple in situ device for indexing the shear strength of thin weak layers. The index is sensitive to shear-frame geometry, rate-of-pull, and shear-frame mass. It is time-consuming to carefully align the device on the Gleitschicht (shear failure plane) in a slab avalanche zone. The ratio shear frame index/shear stress of the Gleitschicht has a high variance, and may not be a fundamental measure of slab avalanche stability. Corrections for the normal stress on the Gleitschicht reduce the variance only slightly. Despite these limitations, the shear frame is a useful tool for gathering statistical data on strength distributions and anisotropies of the Gleitschicht until a more fundamental technique is developed.


2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jianhang Chen ◽  
Fan Zhang ◽  
Hongbao Zhao ◽  
Junwen Zhang

Cement grout is widely used in civil engineering and mining engineering. The shear behaviour of the cement grout plays an important role in determining the stability of the systems. To better understand the shear behaviour of the cement grout, numerical direct shear tests were conducted. Cylindrical cement grout samples with two different strengths were created and simulated. The numerical results were compared and validated with experimental results. It was found that, in the direct shear process, although the applied normal stress was constant, the normal stress on the contacted shear failure plane was variable. Before the shear strength point, the normal stress increased slightly. Then, it decreased gradually. Moreover, there was a nonuniform distribution of the normal stress on the contacted shear failure plane. This nonuniform distribution was more apparent when the shear displacement reached the shear strength point. Additionally, there was a shear stress distribution on the contacted shear failure plane. However, at the beginning of the direct shear test, the relative difference of the shear stresses was quite small. In this stage, the shear stress distribution can be assumed uniform on the contacted shear failure plane. However, once the shear displacement increased to around the shear strength point, the relative difference of the shear stresses was obvious. In this stage, there was an apparent nonuniform shear stress distribution on the contacted shear failure plane.


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