scholarly journals Effect of Dry-wet Cycle on the Formation of Loess Slope Spalling Hazards

2018 ◽  
Vol 4 (4) ◽  
pp. 785 ◽  
Author(s):  
Wanjun Ye ◽  
Yuyu Zhang
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Clay Particles ◽  
Angle Of Internal Friction ◽  
Cycle Times ◽  
Direct Shear Tests ◽  
Loess Slope ◽  
Lower Shear ◽  
Content Variation ◽  
Water Contents

This paper investigates the effect of dry-wet cycle process on the formation of loess slope spalling hazards. Based on the CT scan tests and macroscopic fissures analysis, the fissure variation law of loess samples under different dry-wet cycle times were determined. Through the laboratory direct shear tests, the variation law of shear strength, cohesion and angle of internal friction of loess samples under different dry-wet cycle times and different dry-wet cycle water content variation ranges were discussed. The results show that the natural water contents of Luo-chuan loess were higher than Tong-chuan loess due to it’s higher contents of clay particles. With the increase of dry-wet cycle times, the internal fissure numbers of loess samples increased dramatically. The value of shear strength and cohesion of loess samples in two different areas decreased dramatically due to the increase of dry-wet cycle times. Higher water content variation ranges of dry-wet cycles leaded to lower shear strength of loess samples under the same dry-wet cycle times. Loess slope spalling hazards often happened due to the decrease of shear strength and the occurrence of internal fissures in loess induced by the dry-wet cycle process.

Experimental Study on Shear Strength of Gravel Silty Clay from a Post-Earthquake High Slope

2012 ◽  
Vol 166-169 ◽  
pp. 2395-2399
Author(s):  
Ping Yang ◽  
Zhan Yuan Zhu ◽  
You Mo ◽  
Bing Teng ◽  
Zu Yin Zou
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Safety Evaluation ◽  
Heavy Rain ◽  
Dry Density ◽  
Silty Clay ◽  
High Slope ◽  
Angle Of Internal Friction ◽  
Direct Shear Tests ◽  
Grain Diameter

Based on direct shear tests of gravel silty clay from the high slope of Daju Mountain in Niufei Village, Pingtong Town, Sichuan Province after the 5.12 Wenchuan Earthquake, change laws of shear strength under different water content, dry density and maximal grain-diameter were studied. Through analyzing variation curves on shear strength and two indexes, cohesion C and angle of internal friction , conclusions can be drawn that shear strength goes down along with the growth of water content, goes up along with the growth of dry density, and is sensitive to the change of maximal grain-diameter; the influence of water content on shear strength and the two indexes, is largest, dry density larger and maximal grain-diameter worst. And the change mechanism of shear strength was interpreted rationally. Simultaneously the powerful functions were used to fit the relationships between shear strength indexes and the three influencing factors respectively. The paper accumulates basic data for shear strength study of the post-earthquake soil and provides important references for safety evaluation of the post-earthquake high slopes under harmful conditions, for example heavy rain and so on.

scholarly journals Shear strength characteristics of Jerash expansive soil

2021 ◽  
Vol 3 (2) ◽  
pp. 74-80
Author(s):  
Talal Masoud
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Water Content ◽  
Direct Shear Test ◽  
Shear Test ◽  
Expansive Soil ◽  
Content Increase ◽  
Direct Shear ◽  
Initial Water ◽  
Angle Of Internal Friction

The results of the direct shear test on Jerash expansive soil show the effect of the initial water content on the cohesion (c) and on the angel of internal friction ( ) [shear strength parameters].it show that, as the initial water increase, the cohesion (c) of Jerash expansive soil also increase up to the shrinkage limit, after that increase of water even small amount, decrease the cohesion of the soil. On the other hand, the results of direct shear test show also  that as the water content increase, the angle of internal friction ( )remain unchanged up to shrinkage limit , any increase of water cause a large decrease on the angle of internal friction of Jerash expansive soil.

Influence of Water Contents on Shear Strength of Rammed Earth Wall of Earth-Building

2011 ◽  
Vol 382 ◽  
pp. 172-175
Author(s):  
Ren Wei Wu ◽  
Xing Qian Peng ◽  
Li Zhang
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Triaxial Compression ◽  
Friction Angle ◽  
World Heritage Site ◽  
Rammed Earth ◽  
Compression Tests ◽  
Rammed Earth Wall ◽  
Influence Of Water ◽  
Water Contents

As the "Fujian earth-building" have been inscribed by UNESCO in 2008 as World Heritage Site, attentions of protection about the "Fujian earth-building" has getting more and more. This article takes samples of a rammed-earth wall from Yongding earth-buildings and determines the shear strength of the samples with different water content through triaxial compression tests. The influence on shear strength of water content of rammed-earth samples is analyzed. Test results show that the shear strength of rammed-earth has much to do with the water content of the soil, the greater the water content is，the smaller the shear strength is. With water content increasing, cohesion and internal friction angle of rammed-earth were decreases, and its changing trend is of marked characteristic of stage. When water contents of rammed-earth is under some value, its cohesion changes in small ranges; when water contents of rammed-earth is over the value, its cohesion decreases with water content increasing.

Effect of Glass Fiber on Shear Strength of Soil

2018 ◽  
Vol 775 ◽  
pp. 603-609
Author(s):  
Himadri Shekhar Saha ◽  
Debjit Bhowmik
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Moisture Content ◽  
Glass Fiber ◽  
Water Content ◽  
Soil Samples ◽  
Fiber Content ◽  
Triaxial Tests ◽  
Angle Of Internal Friction ◽  
Increase With Increase

This paper investigates the effect of glass fiber reinforcement on the shear strength properties of the sand clay mixture. The soil samples were prepared by mixing 50% of locally available Barak river sand with 50% of local clay soil. Triaxial tests were conducted on the soil samples containing five different percentage of fiber to know the effect of fiber content on the shear strength of the soil. Unconsolidated Undrained (UU) Triaxial tests were conducted under three different confining pressures for each sample. Samples were prepared with five different values of moisture content considering 2% less than OMC (Optimum Moisture Content), 1% less than OMC, OMC, 1% more than OMC, and 2% more than OMC to study the effect of water content (w) on behavior of fiber reinforced soil. A parametric study has been carried out in this paper to know the effect of different influencing parameters on the cohesion value and angle of internal friction. The results show that the failure stress and angle of internal friction increase with increase in fiber content up to an optimum value then decrease. On the other hand, the cohesion value increases consistently with increase in fiber content. The study also indicates that the peak deviator stress, angle of internal friction and cohesion values increase with increase in water content up to an optimum value which is less than OMC then decrease with further increase in water content.

Influence of Matric Suction on Shear Strength Behavior of Unsaturated Silty Sand

2012 ◽  
Vol 446-449 ◽  
pp. 1627-1632
Author(s):  
Qian Dong ◽  
Liu Liu ◽  
Long Hou
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Peak Effect ◽  
Silty Sand ◽  
Direct Shear Tests ◽  
Suction Control ◽  
Two Factors ◽  
The Matrix ◽  
Matrix Suction ◽  
The Relationship

In order to research matrix suction how to influence the shear strengt of unsaturated silty sand. Based on the analysis of the Soil-water characteristic of unsaturated silty sand through pressure plate instrument test,the suction control direct shear tests under the different suction condition of unsaturated silty sand are studied. And then, the microscopic structure of two kinds soil sample with different water content are scanned to analyze the relationship between the matrix suction and the shear strengt of unsaturated silty sand. The results of the research show that unsaturated silty sand different from unsaturated clayey soil.When water content gradually reduce, the soil shear strength of unsaturated silty sand is not always increased with the increase of matrix suction, but there is a "peak effect".The appearance of "peak effect" is due to unsaturated silty sand has own microstructure characteristics.On the other hand, when the moisture content reduction constantly,the existence form of moisture change gradually.The two factors lead to the effect area of matrix suction change constantly,and then influence shear strengt of unsaturated silty sand to appear "peak effect". In addition,the stress environment also can influence contribution degree of matrix suction to the shear strengt of unsaturated silty sand.

Shear strength of remolded soils at consistency limits

2010 ◽  
Vol 47 (3) ◽  
pp. 259-266 ◽  
Author(s):  
Kamil Kayabali ◽  
Osman Oguz Tufenkci
Keyword(s):  
Shear Strength ◽  
Linear Relationship ◽  
Water Content ◽  
Undrained Shear Strength ◽  
Liquid Limit ◽  
Soil Samples ◽  
Atterberg Limits ◽  
Plastic Limit ◽  
Water Contents ◽  
Undrained Shear

The undrained shear strength of remolded soils is of concern in certain geotechnical engineering applications. Several methods for determining this parameter exist, including the laboratory vane test. This study proposes a new method to estimate the undrained shear strength, particularly at the plastic and liquid limits. For 30 inorganic soil samples of different plasticity levels, we determined the Atterberg limits, then performed a series of reverse extrusion tests at different water contents. The plastic and liquid limits are derived from the linear relationship between the logarithm of the extrusion pressure and water content. The tests show that the average undrained shear strength determined from the extrusion pressures at the plastic limit is about 180 kPa, whereas the average undrained shear strength at the liquid limit is 2.3 kPa. We show that the undrained shear strength of remolded soils at any water content can be estimated from the Atterberg limits alone. Although the laboratory vane test provides a reasonable undrained shear strength value at the plastic limit, it overestimates the undrained shear strength at the liquid limit and thus, care must be taken when the laboratory vane test is used to determine undrained shear strengths at water contents near the liquid limit.

scholarly journals Shear Behavior and Anisotropy Characteristics of the Fracture Morphology of Sandstone with Different Water Contents

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-8 ◽  
Author(s):  
Changang Du ◽  
Lulu Sun ◽  
Botao Qin ◽  
Jiang Xu ◽  
Yixin Liu
Keyword(s):  
Water Content ◽  
Shear Failure ◽  
Shear Fracture ◽  
Failure Process ◽  
Three Dimensional ◽  
Fracture Morphology ◽  
Jointed Rock ◽  
Direct Shear Tests ◽  
Initiation And Propagation ◽  
Water Contents

Hydromechanical coupling in rock masses is an important issue for many rock mechanics and hydrogeology applications. The change of a water-bearing state will induce the fracture of the intact rocks and further accelerate the shear slip instability of the sheared surface. To investigate the weakening effect of water content on the mechanical properties of a rock mass, laboratory direct shear tests combined with three-dimensional analysis of sheared surfaces were carried out on sandstone samples with different water contents. The variogram parameters, sill and range, were applied to quantify the morphology of shear fracture surfaces, to reflect the shear failure process of the intact rock, and to provide a basis for resliding instability of jointed rock. It was determined that the sill represents the height of the fluctuation body in the fracture surface and the range represents the single fluctuation body and may reflect the frequency of fluctuations. The test results revealed that the increase in water content had a clear weakening effect on the shear strength and deformation behavior of rock, especially under saturated conditions. Moreover, the distribution of water in the samples directly affected the crack initiation and propagation and characteristics of the fracture morphology.

scholarly journals Study on the Rheological Behavior of a Model Clay Sediment

2021 ◽  
Vol 9 (1) ◽  
pp. 81
Author(s):  
Yuan Lin ◽  
Huaitao Qin ◽  
Jin Guo ◽  
Jiawang Chen
Keyword(s):  
Water Content ◽  
Yield Stress ◽  
Rheological Behavior ◽  
Seabed Sediment ◽  
Clay Particles ◽  
Face To Face ◽  
The Face ◽  
Clay Sediment ◽  
Main Component ◽  
Water Contents

Clay sediments are the main component of seabed sediment. Interactions between the nano-sized, disk-shaped and charged clay particles are complicated, as they control the sediment’s rheology. In this study, we studied the rheological behavior of the clay sediment modeled by laponite and bentonite suspensions experimentally using a rotational rheometer. The yield stress decreased when water content increased. Meanwhile, the yield stress of the laponite suspension first increased and then decreased with increasing salinity. It is considered that the face-to-face repulsive electrostatic interaction between clay platelets dominated the yield behavior. A yield stress model was developed to describe the change of the yield stress with both the water content and the salinity. When the system started to flow, the viscosity decreased with increasing shear. A master curve of viscosity is was from the viscosity-stress curves at different water contents if the applied shear stress was normalized by the yield stress and the viscosity normalized by a characteristic viscosity. This study provides a preliminary understanding of the clay sediment rheology and its mechanism for the investigation on the flowing of the sediment systems with strong interparticle interaction.

scholarly journals Effect of Soaking and Non-soaking Condition on Shear Strength Parameters of Sandy Soil Treated with Additives

2019 ◽  
Vol 5 (5) ◽  
pp. 1147-1161
Author(s):  
Roaa M. Fadhil ◽  
Haifaa A. Ali
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Sandy Soil ◽  
Dry Weight ◽  
Natural State ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Angle Of Internal Friction ◽  
Direct Shear Tests ◽  
Before And After

The present paper aims to improve shear strength parameters: cohesion (c), and angle of internal friction (∅) for sandy soil treated by additives before and after soaking. The samples of sandy soil were obtained from Karbala city and then classified as poorly graded sand (SP) with relative density Dr (30%) according to the system of (USCS). The experiment has three stages. In the first stage ,the soil was treated with three different  percentages of cement (3 ,5 and 7%) of dry weight for the soil with three different percentages of water content (2, 4 and 8%) in each above percentage of cement, while the second stage includes (2%) of lime  from  soil weight  mixed with each different percentage of cement . In the third stage, (50%) of polymer of cement weight was mixed with each different percentage of cement. An analysis of behavior sandy soils treated by additives was carried out with the Direct Shear Tests. All the samples were cured (3) days before and after soaking. The results of the experiment showed that increase in shear strength parameters of sandy soil; especially the angle of internal friction with the rate value (16.6 %) of cement only, (21.88 %) of cement with lime , (20.3%) of cement with the polymer before soaked condition. After soaking condition, it was increased with the rate value (14.3%) with cement only, (23.57%) of cement with lime, and (15.38%) of cement with the polymer as compared with soil in the natural state.

scholarly journals Mechanical Properties of Frozen Glacial Tills due to Short Periods of Thawing

2021 ◽  
Vol 9 ◽  
Author(s):  
Yanju Fu ◽  
Yao Jiang ◽  
Jiao Wang ◽  
Ziming Liu ◽  
Xingsheng Lu
Keyword(s):  
Shear Strength ◽  
Initial Phase ◽  
Peak Stress ◽  
Friction Angle ◽  
Initial Water ◽  
Direct Shear Tests ◽  
Warming Climate ◽  
Marked Decline ◽  
Glacial Tills ◽  
Water Contents

Due to the warming climate, glacier retreat has left massive glacial tills in steep gullies; ice in the soil is prone to change phase resulting in the decrease of the ice strength and bonding of soil particles; collapse of thawing tills can lead to debris flows with disastrous consequences for geotechnical infrastructures. To improve our understanding of the mechanics of thawing glacial tills, we conducted unconsolidated–undrained direct shear tests on glacial tills from Tianmo gully on the southeastern Tibetan Plateau. Control specimens were not subjected to freeze–thaw action. A total of 648 specimens with three different dry densities, three initial water contents, and 18 thawing times were tested. Peak shear strength, peak stress to displacement ratio (0.857), and cohesion were the highest in frozen specimens. After a thawing time of 0.25 h, there was a marked decline in shear strength; maximum friction was 2.58, which was far below the value of cohesive strength. For thawing times of 0.25–4 h, peak strength varied little with thawing time, but cohesion decreased and internal friction angle increased with increasing thawing time. Our results indicate that thawing of the solid ice in the till during the initial phase of till thawing is the key control of peak till strength; the effect of ice on cohesion is greater during the initial phase of thawing and in loose tills. Moreover, frequent sediment recharge of gullies may be explained by the decrease of cohesion with increasing thawing time caused by short-term destruction of ice bonding.

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