scholarly journals Experimental Study on Main Physical Parameters Controlling Shear Strength of Unsaturated Loess

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Wen-tong Tian ◽  
Jian-hua Dong ◽  
Jun-jie Sun ◽  
Bo Yang
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Water Content ◽  
Quartz Sand ◽  
Clay Content ◽  
Friction Angle ◽  
Dry Density ◽  
Physical Parameters ◽  
Sandy Silt ◽  
Unsaturated Loess

It is particularly important to study the strength of unsaturated loess, and its accurate determination is crucial to the stability analysis of soil slope and foundation and calculation of earth pressure. In order to reveal the control mechanism of physical parameters on the shear strength of unsaturated loess, the intact and remolded loess were used as the research object; sandy silt, quartz flour, and quartz sand were used as contrast; the systematic direct shear tests of unsaturated loess, sandy silt, and quartz sand under different conditions of water content, dry density, and clay content were carried out. The results show that the cohesion, internal friction angle, and shear strength of unsaturated loess piecewise functionally decrease with the increase of water content, its shear strength increases linearly with the increase of dry density, and its internal friction angle shows an upward quadratic function relation with the increase of clay content. The law results of comparing sandy silt, quartz flour, and quartz sand with loess considering water content and dry density are the same; therefore, the equation of shear strength of unsaturated loess is proposed for practical engineering reference, and by the first derivative analysis of the equation, it is feasible to determine the control proportion of the three parameters on the shear strength of unsaturated loess. A stage-like difference between the three control proportions is observed, depending on the combination variations of water content and clay content.

The Physical and Mechanic Properties of the Loess Landslide

2012 ◽  
Vol 446-449 ◽  
pp. 3003-3006
Author(s):  
Li Hua Li ◽  
Meng Dang ◽  
Heng Lin Xiao ◽  
Hui Ming Tang
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Internal Friction ◽  
Water Content ◽  
Maximum Shear Stress ◽  
Friction Angle ◽  
Dry Density ◽  
Disaster Prevention ◽  
Loess Landslide ◽  
Landslide Disaster

The loess landslide in BaDong city, HuBei province China suffers great losses, which is an extremely typical landslide disaster. Variation in water level in the Yangtse River and rainfall has enormous influence on the loess landslide disaster. Some tests on loess have been done, which mainly include water content influence on shear strength of the loess, the relation between water content and dry density etc. The results have shown that When the water content average increasing with 3%, the cohesive strength reduces with 57%，49%，54% respectively and the internal friction angle average reduces 43%. The bigger the water content, the bigger the shear displacement at the same imposed load. When water content average increases with 3%, the corresponding maximum shear stress reduces with 50%, which may be in favor of loess landslide disaster prevention.

Research on Shear Strength of Compacted Loess

2013 ◽  
Vol 448-453 ◽  
pp. 1284-1288 ◽  
Author(s):  
Juan Juan Wang ◽  
Jun Tao Deng ◽  
Song Lin Wu
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Water Content ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Dry Density ◽  
Dam Foundation ◽  
Direct Shear Tests ◽  
Strength Formula ◽  
Compacted Loess

Compacted loss widely used in the construction, such as embankment, dam, foundation backfill and other projects. Influenced by rainfall factors, the moisture content of compacted loess often vary so the shear strength will also changed. This paper studies the shear strength parameters of compacted loess through direct shear tests. In the dry density under the same conditions, the cohesion, internal friction angle of compacted loess decreases with the increase of water content. Summed cohesion and water content showed a quadratic parabola and internal friction angle and water content was also found quadratic parabola; further considering the effects of water content and dry density of compacted loess got shear strength formula. Shear strength formula.

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 Determining the Shear Strength and Permeability of Soils for Engineering of New Paddy Field Construction in a Hilly Mountainous Region of Southwestern China

2020 ◽  
Vol 17 (5) ◽  
pp. 1555
Author(s):  
Zhen Han ◽  
Jiangwen Li ◽  
Pengfei Gao ◽  
Bangwei Huang ◽  
Jiupai Ni ◽  
...  
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Water Content ◽  
Engineering Design ◽  
Soil Water ◽  
Soil Water Content ◽  
Paddy Field ◽  
Friction Angle ◽  
Strength Properties ◽  
Mountainous Region

As a constructed wetland ecosystem, paddy field plays an irreplaceable role in flood storage and detention, groundwater replenishment, environmental protection, and ecological balance maintenance. New paddy field construction can give full play to the production and ecological functions of paddy field and can adjust the development structure of the agricultural industry effectively. The soil properties of shear strength and permeability, which provide a theoretical basis for engineering design, construction, and post-operation, are important indexes in the site selection of new paddy field. The shear strength and permeability properties of soils from different land use types (vegetable field, gentle slope dryland, corn field, grapery, and abandoned dryland) for engineering new paddy field construction were investigated in this study. The results showed that the soil water content had a significant effect on the soil shear strength, internal friction angle, and cohesion. The total pressure required for soil destruction decreased with increasing water content under the same vertical pressure, resulting in easier destruction of soils. The internal friction angle decreased with increasing soil water content, and the soil cohesion first increased and then decreased with increasing soil water content. Considering that paddy fields were flooded for a long time, the soil strength properties had certain water sensitivity. Effective measures must be taken to reduce the change in soil water content, so as to ensure the stability of the embankment foundation, roadside ditch foundation, and cutting slope. In addition, the influence of changing soil water content on the strength properties of paddy soils should be fully considered in engineering design and construction, and the soil bulk density at the plough pan should reach at least 1.5 g cm−3 or more to ensure better water retention and the anti-seepage function of paddy field. The study can provide construction technology for engineering new paddy field construction in a hilly mountainous region of southwestern China.

Experimental Research on the Characteristics of Soil Strength Freeze-Thaw Weakening in Songhua River Songpu Bank

2014 ◽  
Vol 501-504 ◽  
pp. 403-409
Author(s):  
Xue Han ◽  
Zi Long Zhao ◽  
Zi Rui Gao
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Friction Angle ◽  
Soil Strength ◽  
Internal Friction Angle ◽  
Physical Parameters ◽  
Freezing And Thawing ◽  
Songhua River ◽  
Freeze Thaw ◽  
Soil Shear Strength

In order to study characteristics of soil strength freeze-thaw weakening in the Songhua River Songpu bank，basic physical parameters tests and triaxial compression tests were performed on that paragraph bank .The results showed that: after thawing the sample cohesion will drop substantially, the internal friction angle will increase greatly and soil shear strength will increase significantly; the cohesion of sample after repeated freezing and thawing will significantly decline，internal friction angle of soil will greatly increase，the soil shear strength will increase after the first freezing and thawing，with the increase in the number of freeze-thaw cycles, the soil shear strength will significantly decline. The results can provide Songhua slope stability analysis with a scientific basis.

Study on the Effect of Water Content on Shearing Strength Parameters of Unsaturated Loess

2014 ◽  
Vol 638-640 ◽  
pp. 585-588 ◽  
Author(s):  
Si Zhong Qian
Keyword(s):  
Internal Friction ◽  
Water Content ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Direct Shear ◽  
Strength Parameters ◽  
Direct Shear Tests ◽  
Micro Particles ◽  
Shearing Strength ◽  
Unsaturated Loess

This paper experiments on typical Malan loess, performs consolidated quick direct shear tests under different water contents by conventional direct shear apparatus, then analyzes the effects of water content on shearing strength parameters, namely cohesion and internal friction angle. The results show that cohesion decreases linearly as the water content increasing, and the relation could be obtained by data fitting. However, internal friction angle keeps basically stable with the increase of water content. Finally, based on the force analysis for micro particles, the changing rules of cohesion and internal friction angle with water content were deeply explained.

scholarly journals Influence of water content on the shear strength parameters of clayey soil in relation to stability analysis of a hillside in Brno region

2013 ◽  
Vol 61 (6) ◽  
pp. 1583-1588 ◽  
Author(s):  
Kristýna Bláhová ◽  
Lenka Ševelová ◽  
Pavla Pilařová
Keyword(s):  
Shear Strength ◽  
Stability Analysis ◽  
Water Content ◽  
Clayey Soil ◽  
Friction Angle ◽  
Dry Density ◽  
Stability Analyses ◽  
Influence Of Water ◽  
Moisture Conditions ◽  
Processing Stability

Shear strength of soils is highly affected by moisture conditions (i.e. water content), especially if the soil contains clay materials. Usually the laboratory specimen, which are used to determine shear strength of soil are prepared at water content and dry density same as in the field conditions, without respect to the fact, that the conditions in the future might not remain the same. For the purpose of this study soil specimen were compacted and the optimum moisture content was identified. After compaction soil was tested at the dry side of optimum water content at w = 9 %, 10 % and 11 %. Parameters of shear strength were obtained and used for stability analysis with software GEOSLOPE/W 2012. According to referenced literature, it was expected for the shear strength of the soil to decrease with increasing water content. This hypothesis was not proven for clayey soil from Brno region. Development of values of friction angle and cohesion exhibited anomalous behaviour and such development was found also for values of Factor of safety (FOS) obtained from stability analyses. Results proved the necessity of taking moisture conditions into account, when processing stability analyses, in order to achieve reliable and safe constructions.

scholarly journals Effect of conglomeration gradation on loess shear strength with different water content

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110105
Author(s):  
Dequan Kong ◽  
Rong Wan ◽  
Chenkai Zhao ◽  
Jiumei Dai ◽  
Tijian Dong ◽  
...  
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Water Content ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Empirical Formulas ◽  
Factors Affecting ◽  
Direct Shear Tests ◽  
Loess Particles ◽  
The Difference

Particle gradation and water content are important factors affecting shear strength of soil. However, due to chemical cementation and molecular attraction, loess particles commonly stick together forming conglomerations. Till date, the superposition effect of water content and conglomeration gradation on loess shear strength has rarely been studied and undeniably requires further systematic explorations and development. In this study, loess samples were prepared with three conglomeration gradations and five water contents, and the direct shear tests were systematically performed. The shear strength of sample 1 (continuous conglomeration gradation) was found to be the best, followed by sample 2 (large size conglomerations), and sample 3 (small size conglomerations). The difference of samples’ shear strength decreased with increasing water content, and almost closed to zero when water content was 20%. The cohesion of samples first increased and then decreased with increasing water content, the maximum cohesion occurred at 10% water content. The internal friction angles decreased with increasing water content, and reached similar minimum values when the water content was 15%. The increased percentage values of cohesion and internal friction angle caused by conglomeration gradation are in the range of 33.2%–42.1% and 9.8%–32.5%, respectively. Finally, the empirical formulas for water content-cohesion and water content-internal friction angle of different conglomeration gradations samples were established, and the calculated values are in good agreement with test data. The effect of loess conglomeration gradation on shear strength decreased with increasing water content. When the water content was less than 15%, using a good conglomeration graduation could effectively improve loss shear strength.

scholarly journals Strength of Vegetated Coal-Bearing Soil under Dry-Wet Cycles: An Experimental Study

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Gang Huang ◽  
Mingxin Zheng
Keyword(s):  
Internal Friction ◽  
Water Content ◽  
Southern China ◽  
Orthogonal Design ◽  
Friction Angle ◽  
Chain Structure ◽  
Internal Friction Angle ◽  
Soil Reinforcement ◽  
Dry Density ◽  
Mineral Particles

Strength of vegetated coal-bearing soil is of great significance to evaluate the shallow stability of vegetated slopes in coal-bearing soil regions. This paper takes D-W cycles, dry density, water content, and vegetation root (VR) content as four factors and carries out the triaxial test for the orthogonal design of vegetated coal-bearing soil in southern China. The strength curves of vegetated coal-bearing soil under four factors were obtained. The Taguchi method was used to quantitatively analyse the effects of four factors. The microstructure of coal-bearing soil under D-W cycles and the theory of soil reinforcement by VR were discussed. The results indicated that D-W cycles had a significant effect on the cohesion and internal friction angle ( P < 0.05 ). The internal friction angle was little affected by the water content and VR content, which had considerable influence on the cohesion. The cohesion could be improved with less than 2% VR content. The cohesion was the largest for no D-W cycles, 10% water content, and 2% VR content. The links between mineral particles go from a stable layered structure to unsteadiness chain structure with the increase in the number of D-W cycles.

scholarly journals Estimation of Soil Shear Strength Indicators Using Soil Physical Properties of Paddy Soils in the Plastic State

2021 ◽  
Vol 11 (12) ◽  
pp. 5609
Author(s):  
Qianjing Jiang ◽  
Ming Cao ◽  
Yongwei Wang ◽  
Jun Wang ◽  
Zhuoliang He
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Clay Content ◽  
Friction Angle ◽  
Soil Samples ◽  
Internal Friction Angle ◽  
Paddy Soils ◽  
Interactive Effects ◽  
Soil Cohesion ◽  
Soil Shear Strength

Saturated soil shear strength is a primary factor that reflects the driving resistance of agricultural machinery in paddy soils. The determination of soil shear strength indicators, such as cohesion and internal frictional angle, is crucial to improve the walking efficiency of agricultural machinery in paddy soils. However, the measurement of these indicators is often costly and time-consuming. Soil moisture content, density, and clay content are crucial factors that affect the cohesion and internal friction angle, while very limited studies have been performed to assess the interactive effects of the three factors on soil shear characteristics, especially on paddy soils. In this study, eight soil samples were taken from eight paddy fields in Southeastern China, and the central composition rotatable design was used to classify the soil samples into five levels based on different clay content (X1), moisture content (X2), and density (X3). The direct shear tests were carried out indoors on the remolded paddy soil using a self-made shear characteristic measuring device. Then, both individual and interactive effects of X1, X2, and X3 on soil cohesion and internal friction angles on paddy soils were systematically investigated and analyzed using the regression analysis method in the data processing software Design-Expert. Our results indicated that the effects of the three environmental factors on soil cohesion were in the order of X1 > X2 > X3, while the order was X2 > X3 > X1 for the impact on internal friction angle. The interactive effects were in the order of X1X2 > X1X3 > X2X3 for cohesion and X1X2 > X2X3 > X1X3 for internal friction angle. Two prediction models were successfully established to quantify the soil cohesion and internal friction angle as affected by soil physical properties, and the coefficient of determination (R2) was 0.91 and 0.89 for the two equations, respectively. The model validations using new soil samples suggested that the models were capable of predicting the shear characteristic parameters under different physical parameters effectively, with errors between predicted and measured soil shear strength indicators within 15% and relative root mean square error less than 11%.

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