The analysis of effects on shear strength characteristics of loess by moisture content changes and freeze-thaw circle

2014 ◽  
pp. 433-438
Keyword(s):  
Shear Strength ◽  
Moisture Content ◽  
Strength Characteristics ◽  
Freeze Thaw

scholarly journals Shear Properties and Mechanism of Freeze-Thaw Interface in Unsaturated Coarse-Grained Soil from Qinghai-Tibet Plateau

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Yonglong Qu ◽  
Wankui Ni ◽  
Fujun Niu ◽  
Yanhu Mu ◽  
Jing Luo ◽  
...  
Keyword(s):  
Shear Strength ◽  
Moisture Content ◽  
Coarse Grained ◽  
Tibet Plateau ◽  
Dry Density ◽  
Direct Shear ◽  
Shear Properties ◽  
Freeze Thaw ◽  
Qinghai Tibet Plateau ◽  
Coarse Grained Soil

Freeze-thaw interface in unsaturated coarse-grained soil (CGS) is a weak plane which can cause slope failures in cold regions. This study presents a series of large-scale direct shear tests on freeze-thaw interface in CGS through a temperature control system. The tested soil was taken from a high slope in the Qinghai-Tibet Plateau. It was remolded with three dry densities (1.9, 2.0, and 2.15 g/cm3) and three moisture contents (9.0%, 11.5%, and 14.0%). With testing results, direct shear curves mainly performed as hardening deformation, and they were affected considerably by specimen conditions. The shear strength increased with both the increasing dry density and normal stress, but it was opposite with moisture content changed. The cohesion and internal friction angle increased with the increase in dry density but decreased with the moisture content. The particle movement and water migration of freeze-thaw interface in CGS during the test were significant, and they had close relations with the shear properties of specimens. And, an empirical model was produced to express the effect of pore ice on the shear strength of interface during the shear test. The tests and analysis in this study may provide useful references for CGS slope stability analysis in high cold regions.

Shear Strength Monitoring System Based on Measurement of Shear Wave Velocity and Moisture Content

2014 ◽  
Vol 635-637 ◽  
pp. 750-754
Author(s):  
Peng Hu ◽  
Qing Li ◽  
Yi Wei Xu ◽  
Nan Ying Shentu ◽  
Quan Yuan Peng
Keyword(s):  
Shear Strength ◽  
Moisture Content ◽  
Shear Wave ◽  
Monitoring System ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Bender Elements ◽  
Strength Measurement ◽  
Soil Shear Strength ◽  
The Relationship

Expound the importance of soil shear strength measurement at mudslide hidden point to release the loss caused by the disaster, explain the relationship between shear wave velocity, moisture content and shear strength, design the shear strength monitoring system combining the shear wave velocity measured by Piezoelectric bender elements and moisture content.

Characterization of Shear Strength and Interface Friction of Organic Soil

2020 ◽  
Vol 857 ◽  
pp. 203-211
Author(s):  
Majid Hamed ◽  
Waleed S. Sidik ◽  
Hanifi Canakci ◽  
Fatih Celik ◽  
Romel N. Georgees
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Internal Friction ◽  
Moisture Content ◽  
Water Content ◽  
Friction Angle ◽  
Structural Materials ◽  
Organic Soil ◽  
Internal Friction Angle ◽  
Interface Friction

This study was undertaken to investigate some specific problems that limit a safe design and construction of structures on problematic soils. An experimental study was carried out to examine the influence of loading rate and moisture content on shear strength of organic soil. Influece of moisture content on interface friction between organic soil and structural materials was also attempted. A commonly used soil in Iraq was prepared at varying moisture contents of 39%, 57% and 75%. The experimental results showed that the increase in water content will decrease the shear stress and the internal friction angle. An increase of the shearing rate was found to decrease the shear stress and internal friction angle for all percetanges of water contents. Further, direct shear tests were carried out to detect the interface shear stress behavior between organic soil and structural materials. The results revealed that the increase in water content was shown to have significant negetavie effects on the interface internal friction and angle shear strength.

scholarly journals The Shear Strength Characteristics of Frozen Coarse Granular Debris

1984 ◽  
Vol 30 (106) ◽  
pp. 348-357 ◽  
Author(s):  
W.G. Nickling ◽  
L. Bennett
Keyword(s):  
Shear Strength ◽  
Normal Load ◽  
Strength Characteristics ◽  
Shear Tests ◽  
Critical Limit ◽  
Load Rate ◽  
Polycrystalline Ice ◽  
Saturated Sample ◽  
The Difference ◽  
Ice Content

AbstractThe effect of ice content and normal load on the shear strength characteristics of a frozen coarse granular debris was investigated. 31 shear tests were carried out in a modified shearbox allowing a sample temperature of (–1.0 ± 0.2)° C and a load rate of 9.63 × 10−4 cm/min. The tests showed that as the ice content of the frozen debris was increased from 0% (under-saturated) to 25% (saturated), sample shear strength was markedly increased. In contrast, sample shear strength was reduced as ice content was increased from 25% (saturated) to 100% (supersaturated). The changes in shear strength with increasing ice content were attributed directly to changes in internal friction and the cohesive effects of the pore ice. The shear tests also indicate that shear strength increases with increasing normal load up to a critical limit. Above this limit, dilatancy is suppressed causing the shear strength to decrease or remain relatively constant with increased normal load.The stress-strain curves of the 31 tests indicated that samples with higher ice contents tended to reach peak strength (τP) with less displacement during shear. Moreover, the difference between τp and τr (residual strength) was lowest for pure polycrystalline ice and highest for ice-saturated samples. The Mohr-Coulomb failure envelopes displayed very distinctive parabolic curvilinearity. The degree of curvature is thought to be a function of ice creep at low normal loads and particle fracture and crushing at high normal loads.

Influence of Moisture Content in some Mechanical Properties of Two Brazilian Tropical Wood Species

2014 ◽  
Vol 1025-1026 ◽  
pp. 42-45 ◽  
Author(s):  
Luiz A. Melgaço N. Branco ◽  
Eduardo Chahud ◽  
André Luis Christoforo ◽  
Francisco Antonio Rocco Lahr ◽  
Rosane A.G. Battistelle ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Moisture Content ◽  
Analysis Of Variance ◽  
Wood Species ◽  
Modulus Of Elasticity ◽  
Modulus Of Rupture ◽  
Tropical Wood ◽  
Fiber Saturation ◽  
Brazilian Standard

This study aimed, with the aid of analysis of variance (ANOVA), to investigate and quantify the influence of moisture ranging between 12% and over 30% (fiber saturation) on the mechanical properties: strength and modulus of elasticity in compression and in tension parallel to grain; modulus of rupture and modulus of elasticity in static bending; shear strength parallel to grain considering wood species Ipê (Tabebuia sp) and Angelim Araroba (Vataireopsis araroba). Tests were performed according to the assumptions and calculating methods Brazilian standard ABNT NBR 7190, Anexx B, totalizing 400 tests. Results of ANOVA revealed a significant reduction (16% on average) for mechanical properties wood due to the increase in moisture content from 12% to over 30% (fiber saturation). The same behavior also occurred when assembly containing the two species was considered.

Selected Properties of Parallel Strand Lumber Made from Southern Pine and Yellow-Poplar

Holzforschung ◽  
2003 ◽  
Vol 57 (2) ◽  
pp. 207-212 ◽  
Author(s):  
Y. Liu ◽  
A.W.C. Lee
Keyword(s):  
Compressive Strength ◽  
Shear Strength ◽  
Specific Gravity ◽  
Moisture Content ◽  
Dimensional Stability ◽  
Modulus Of Rupture ◽  
Southern Pine ◽  
Yellow Poplar ◽  
Average Modulus ◽  
Parallel Strand Lumber

Summary This study was conducted to explore basic physical and mechanical properties of parallel strand lumber (PSL) made exclusively from southern pine and yellow-poplar, respectively, and to examine their relationships using statistical analysis. Small specimens were prepared from commercial southern pine PSL and yellow-poplar PSL billets and tested for specific gravity, moisture content, dimensional stability, bending properties, shear strength and compressive strength. Results indicate average specific gravity of southern pine PSL is higher than that of yellow-poplar PSL, while their average moisture content and dimensional stability are very similar. Southern pine PSL has higher average modulus of elasticity but lower average modulus of rupture than yellow-poplar PSL. While average longitudinal shear strength does not exhibit differences between southern pine PSL and yellow-poplar PSL, average compressive strength of southern pine PSL is higher than that of yellow-poplar PSL. There are positive correlations among modulus of elasticity, modulus of rupture and specific gravity. PSL improves some properties of solid wood from which PSL is made.

scholarly journals Identifying erosive periods by using RUSLE factors in mountain fields of the Central Spanish Pyrenees

2008 ◽  
Vol 12 (2) ◽  
pp. 523-535 ◽  
Author(s):  
M. López-Vicente ◽  
A. Navas ◽  
J. Machín
Keyword(s):  
Soil Moisture ◽  
Moisture Content ◽  
Soil Loss ◽  
Rainfall Intensity ◽  
Soil Moisture Content ◽  
Rainfall Erosivity ◽  
Soil Erodibility ◽  
Maximum Rainfall ◽  
Freeze Thaw ◽  
Soil Losses

Abstract. The Mediterranean environment is characterized by strong temporal variations in rainfall volume and intensity, soil moisture and vegetation cover along the year. These factors play a key role on soil erosion. The aim of this work is to identify different erosive periods in function of the temporal changes in rainfall and runoff characteristics (erosivity, maximum intensity and number of erosive events), soil properties (soil erodibility in relation to freeze-thaw processes and soil moisture content) and current tillage practices in a set of agricultural fields in a mountainous area of the Central Pyrenees in NE Spain. To this purpose the rainfall and runoff erosivity (R), the soil erodibility (K) and the cover-management (C) factors of the empirical RUSLE soil loss model were used. The R, K and C factors were calculated at monthly scale. The first erosive period extends from July to October and presents the highest values of erosivity (87.8 MJ mm ha−1 h−1), maximum rainfall intensity (22.3 mm h−1) and monthly soil erosion (0.25 Mg ha−1 month−1) with the minimum values of duration of erosive storms, freeze-thaw cycles, soil moisture content and soil erodibility (0.007 Mg h MJ−1 mm−1). This period includes the harvesting and the plowing tillage practices. The second erosive period has a duration of two months, from May to June, and presents the lowest total and monthly soil losses (0.10 Mg ha−1 month−1) that correspond to the maximum protection of the soil by the crop-cover ($C$ factor = 0.05) due to the maximum stage of the growing season and intermediate values of rainfall and runoff erosivity, maximum rainfall intensity and soil erodibility. The third erosive period extends from November to April and has the minimum values of rainfall erosivity (17.5 MJ mm ha−1 h−1) and maximum rainfall intensity (6.0 mm h−1) with the highest number of freeze-thaw cycles, soil moisture content and soil erodibility (0.021 Mg h MJ−1 mm−1) that explain the high value of monthly soil loss (0.24 Mg ha−1 month−1). The interactions between the rainfall erosivity, soil erodibility, and cover-management factors explain the similar predicted soil losses for the first and the third erosive periods in spite of the strong temporal differences in the values of the three RUSLE factors. The estimated value of annual soil loss with the RUSLE model (3.34 Mg ha−1 yr−1) was lower than the measured value with 137Cs (5.38 Mg ha−1 yr−1) due to the low values of precipitation recorded during the studied period. To optimize agricultural practices and to promote sustainable strategies for the preservation of fragile Mediterranean agrosystems it is necessary to delay plowing till October, especially in dryland agriculture regions. Thus, the protective role of the crop residues will extend until September when the greatest rainfall occurs together with the highest runoff erosivity and soil losses.

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