Shear Strength of Unsaturated Soils with Different Plasticity

A series of shear box tests were conducted on four different types of soils in this study. The first set , (clay1) is the host clay, Middle Delta Nile clay “MDNC” which was obtained from Mid Delta Nile zone, Qalyubiyya Governorate, Egypt. The second set, (clay2) consists of the host clay MDNC but mixed with 40% sand. The third set of tests (clay3) was carried out on natural low plastic clay samples brought from El-Tal El-Kbeer area in Ismailia Governorate. The fourth set (clayey sand -SC) consists of 25% of the host clay MDNC mixed with 75% sand. The purpose is to predict the unsaturated shear strength for various soil types. The results illustrate that for clay1, clay2, and clay3, the relationships between the unsaturated shear strength and matric suction are approximated to two linear failure envelopes intersected at matric suction equals to plastic limit. Each segment has an angle of internal friction due to matric suction  b ranging from 1.80 o to 2.90o for the first zone and  b ranging from 0.28 o to 0.20o for the second zone. Meanwhile, for SC soil it appears to have one linear failure envelope for all saturation levels with angle of internal friction due to matric suction;  b=1.19 o.. Design- Expert® software applied the least square method (LSM) to fit a mathematical model for the experimental data. The Response Surface Methodology (RSM) of the program is used to predict the required model. The paper proposed two general equations to calculate the shear strength of unsaturated clays and one equation for granular soils, which are presented at the end of the paper with their coefficients.

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Reliability of Shear-Box Tests Upon Soaking Process on the Sand Soil in Al-Najaf City

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.857.212 ◽

2020 ◽

Vol 857 ◽

pp. 212-220

Author(s):

Mohammed Sh. Mahmood ◽

Waseem H. Al-Baghdadi ◽

Asaad M. Rabee ◽

Suhad H. Almahbobi

Keyword(s):

Shear Strength ◽

Internal Friction ◽

Sandy Soil ◽

Shear Strength Parameters ◽

Strength Parameters ◽

Engineering Structures ◽

Angle Of Internal Friction ◽

Shear Box ◽

Testing Condition ◽

Direct Shear Apparatus

Accurate prediction of the soil shear strength parameters is essential in the reliable geotechnical design of civil engineering structures. This recent paper investigates the effect of the dry testing condition on the shear strength parameters of the sandy soil using the direct shear apparatus and compared with the saturated condition tests in previous researches on the same soil. The dry soil, usually above the water table, is the principal condition of the Al-Najaf city soil in Iraq. Samples are selected from the site of the University of Kufa, which represents the sandy soil of the city. For reliability purposes, the soil is exposed to different pre-soaking durations (one, two, and four weeks) then air-dried for shear tests. The main results revealed that the angle of internal friction (Φ) tested as a dry sample decreases about -6% up to two-weeks soaking then recovered upon four-week soaking about +6%. Compared to the saturated testing, there are increases in F between 6%-17% from saturated tests. Finally, it is recommended to aware in the selection of testing conditions for calculations of the angle of internal friction.

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Shear-strength characteristics of a residual soil

Canadian Geotechnical Journal ◽

10.1139/t95-005 ◽

1995 ◽

Vol 32 (1) ◽

pp. 60-77 ◽

Cited By ~ 155

Author(s):

H. Rahardjo ◽

T.T. Lim ◽

M.F. Chang ◽

D.G. Fredlund

Keyword(s):

Shear Strength ◽

Internal Friction ◽

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Matric Suction ◽

Residual Soil ◽

Test Results ◽

Angle Of Internal Friction ◽

Slip Surfaces

Shallow landslides in natural residual soils slopes are common all over the world. The slip surfaces associated with these landslides are often situated above the groundwater table. Therefore, it is important to quantify the contribution of negative pore-water pressure to the shear strength of soil. The shear-strength characteristics of residual soil from the Jurong Formation in Singapore were assessed using multistage, consolidated drained triaxial tests. These tests involved shearing under either a constant net confining pressure and varying matric suctions or under a constant matric suction and varying net confining pressures. An extended form of the Mohr–Coulomb equation was used to interpret the test results. The test results show that for matric suctions up to 400 kPa, the angle of internal friction associated with the matric suction, [Formula: see text], is similar to the effective angle of internal friction, [Formula: see text], which averages 26° for the residual soil of the Jurong Formation. The residual soil can maintain a high degree of saturation for matric suctions as high as 400 kPa. Examples involving stability analyses of a residual soil slope with varying pore-water pressure profiles indicate that soil suction contributes significantly to the factor of safety, particularly for shallow slip surfaces. Key words : residual soil, unsaturated soil, matric suction, shear strength, multistage triaxial test, slope stability.

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A relationship describing the shear strength of unsaturated soils

Canadian Geotechnical Journal ◽

10.1139/t98-102 ◽

1999 ◽

Vol 36 (2) ◽

pp. 363-368 ◽

Cited By ~ 33

Author(s):

Daud W Rassam ◽

David J Williams

Keyword(s):

Shear Strength ◽

Soil Water ◽

Nonlinear Regression ◽

Unsaturated Soils ◽

Characteristic Curve ◽

Three Dimensional ◽

Matric Suction ◽

Linear Increase ◽

Soil Water Characteristic Curve ◽

Stress Dependent

A relationship describing the shear-strength profile of a desiccating soil deposit is essential for the purpose of analysis, especially when a numerical method is adopted where each zone in a discretised grid is assigned an elevation-dependent shear-strength value. The matric-suction profile of a desiccating soil deposit is nonlinear. Up to the air-entry value, an increase in matric suction is associated with a linear increase in shear strength. Beyond air entry, as the soil starts to desaturate, a nonlinear increase in shear strength occurs. The soil-water characteristic curve is stress dependent, as is the shear-strength gain as matric suction increases. In this paper, a three-dimensional, nonlinear regression analysis showed that a power-additive function is suitable to describe the variation of the shear strength of unsaturated soils with matric suction. The proposed function incorporates the effect of normal stress on the contribution of matric suction to the shear strength.Key words: air-entry value, matric suction, nonlinear regression, soil-water characteristic curve, tailings, unsaturated shear strength.

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Shear strength characteristics of Jerash expansive soil

Journal of Advanced Sciences and Engineering Technologies ◽

10.32441/jaset.03.02.08 ◽

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.

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Study on Water Characteristic Curve and Shear Characteristics of Typical Unsaturated Silty Clay in Shaoxing

Geofluids ◽

10.1155/2021/5510535 ◽

2021 ◽

Vol 2021 ◽

pp. 1-15

Author(s):

Ruiqian Wu ◽

Youzhi Tang ◽

Shaohe Li ◽

Wei Wang ◽

Ping Jiang ◽

...

Keyword(s):

Shear Strength ◽

Internal Friction ◽

Unsaturated Soil ◽

Direct Shear Test ◽

Shear Test ◽

Characteristic Curve ◽

Friction Angle ◽

Matric Suction ◽

Silty Clay ◽

Direct Shear

In order to probe into one simplified method to predict the shear strength of Shaoxing unsaturated silty clay, the test method combining unsaturated soil consolidation instrument and conventional direct shear instrument is used to study the shear strength, and the method is compared and verified with the results of equal suction direct shear test. The research results show that the soil water characteristic curve fitted by the measured data points and VG model has obvious stage characteristics in the range of 0~38 kPa, 38~910 kPa, and 910~10000 kPa. The shear strength of unsaturated soil measured by consolidation meter combined with conventional direct shear test is in good agreement with that measured by equal suction direct shear test in the range of 0~500 kPa. The results show that the shear strength, total cohesion, and effective internal friction angle of soil increase slightly with the increase of matric suction in the range of 0~38 kPa. When the matric suction increases from 38 kPa to 500 kPa, the shear strength and total cohesion force of the soil have similar stage characteristics with the SWCC, which first increases and then tends to be stable, while the effective internal friction angle changes slightly. Finally, taking the air-entry value as the demarcation point, an improved model of unsaturated shear strength is proposed by analyzing the error value. Compared with the measured value, the absolute value of relative error is basically kept in the range of 5%~10%, which is close to the measured value.

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Estimation of shear strength parameters of soil using Optimized Inference Intelligence System

Vietnam Journal of Earth Sciences ◽

10.15625/0866-7187/15926 ◽

2021 ◽

Vol 43 (2) ◽

Author(s):

Binh Thai Pham ◽

Mahdis Amiri ◽

Manh Duc Nguyen ◽

Trinh Quoc Ngo ◽

Kien Trung Nguyen ◽

...

Keyword(s):

Shear Strength ◽

Internal Friction ◽

Physical Parameters ◽

Shear Strength Parameters ◽

Strength Parameters ◽

Inference System ◽

Angle Of Internal Friction ◽

Intelligence System ◽

Statistical Measures ◽

Model Study

In recent years, machine learning techniques have been developed and used to build intelligent information systems for solving problems in various fields. In this study, we have used Optimized Inference Intelligence System namely ANFIS-PSO which is a combination of Adaptive Neural-Fuzzy Inference System (ANFIS) and Particle Swarm Optimization (PSO) for the estimation of shear strength parameters of the soils (Cohesion “C” and angle of internal friction “φ”). These parameters are required for designing the foundation of civil engineering structures. Normally, shear parameters of soil are determined either in the field or in the laboratory which require time, expertise and equipments. Therefore, in this study, we have applied a hybrid model ANFIS-PSO for quick and cost-effective estimation of shear parameters of soil based on the other six physical parameters namely clay content, natural water content, specific gravity, void ratio, liquid limit and plastic limit. In the model study, we have used data of 1252 soft soil samples collected from the different highway project sites of Vietnam. The data was randomly divided into 70:30 ratios for the model training and testing, respectively. Standard statistical measures: Root Mean Square Error (RMSE), Mean Absolute Error (MAE) and Correlation Coefficient (R) were used for the performance evaluation of the model. Results of the model study indicated that performance of the ANFIS-PSO model is very good in predicting shear parameters of the soil: cohesion (RMSE = 0.075, MAE = 0.041, and R = 0.831) and angle of internal friction (RMSE = 0.08, MAE = 0.058, and R = 0.952).

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The Influence of Compaction and Water Conditions on Shear Strength and Friction Resistance between Geotextiles and Ash-Slag Mixture

Energies ◽

10.3390/en13051086 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1086

Author(s):

Andrzej Gruchot ◽

Tymoteusz Zydroń ◽

Agata Michalska

Keyword(s):

Shear Strength ◽

Internal Friction ◽

Water Saturation ◽

Friction Angle ◽

Interaction Coefficient ◽

Interfacial Friction ◽

Shear Strength Parameters ◽

Strength Parameters ◽

Angle Of Internal Friction ◽

Friction Resistance

The paper presents the results of tests of the shear strength of the ash–slag mixture taken from the landfill located in Kraków (Poland) and the interfacial friction resistance at the contact between the ash–slag mixture and woven or nonwoven geotextiles. The tests were carried out in a direct shear apparatus on samples with and without water saturation. The samples for testing were formed in the apparatus box at the optimum moisture by compacting them to IS = 0.90 and 1.00. The test results reveal that the shear strength parameters of the ash-slag mixture were large. It was stated the significant influence of the compaction, the growth of which has resulted in an increase in the angle of internal friction (from 7% to 9%) and cohesion (from 60% to 97%). Whereas the saturation of the samples reduced the shear strength parameters (from 4% to 6%, of the internal friction angle and 30% to 43% of cohesion). The values of the interfacial friction resistance at the contact between the ash–slag mixture and the geotextiles were large as well, but slightly smaller than the values of the shear strength parameters of the mixture itself. The compaction caused an increase in the angle of interfacial friction (from 1% to 5%) and adhesion (from 31% to 127%). The water-saturation of the samples caused a change in the angle of interfacial friction (from −6% to 3%) and decline in the adhesion (from 22% to 69%). Values of the interaction coefficient were about 0.8–1.0 and they tended to rise with increasing the normal stress. Higher values of this parameter were obtained in tests with water saturation and for non-woven geotextiles.

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Simulating a direct shear box test by DEM

Canadian Geotechnical Journal ◽

10.1139/t05-097 ◽

2006 ◽

Vol 43 (2) ◽

pp. 155-168 ◽

Cited By ~ 44

Author(s):

S H Liu

Keyword(s):

Contact Angle ◽

Internal Friction ◽

Granular Material ◽

Distinct Element ◽

Contact Forces ◽

Interparticle Contact ◽

Direct Shear ◽

Angle Of Internal Friction ◽

Shear Box ◽

Direct Shear Box Test

Distinct element simulation was performed for direct shear box (DSB) tests on a dense and a loose two-dimensional (2D) sample of 3259 cylinders. Special attention was devoted to the effect that the frictional force between the inside surface of the upper shear box and the sample had on the measured shear strength in the DSB test. Some ways of minimizing this interface frictional force were introduced in the paper. Given that the deformation approximates simple shear within the deforming zone across the sample centre (referred to as the shear zone), a method was proposed to evaluate the overall strains in the DSB test. The numerically simulated data were used to interpret, on a microscopic scale, the angle of internal friction and a 2D stressdilatancy equation for the mobilized plane in granular material. It was found that the angle of internal friction in granular material is not directly related to the interparticle friction angle (ϕµ). Instead, it relates to the average interparticle contact angle ([Formula: see text]) on the mobilized plane and the ratio k/f0, representing the degree of the probability distribution of the interparticle contact forces that is biased toward the positive zone of the contact angle θ (along the shear direction), where k is the slope of the linear distribution of the average interparticle contact forces against the interparticle contact angle; and f0 is the average interparticle contact force.Key words: angle of internal friction, direct shear box test, distinct element method, friction, granular material, stressdilatancy.

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A Method of Data Processing for Determining Shear Strength Parameters of Rock

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.97-98.397 ◽

2011 ◽

Vol 97-98 ◽

pp. 397-401 ◽

Cited By ~ 2

Author(s):

Zhi Rong Jia ◽

Jun Shi

Keyword(s):

Shear Strength ◽

Slope Stability ◽

Least Square Method ◽

Least Square ◽

Mechanical Parameters ◽

Shear Strength Parameters ◽

Strength Parameters ◽

New Approach ◽

Calculating Method ◽

Main Factors

One of the main factors that influence the analytic results of slope stability is the determining of mechanical parameters. When the least square method is adopted as the method for determining the rock shear strength parameters, its precondition that the observation errors exist only in one observation variable is always being neglected. By analysis, the calculating of shear strength parameters is divided into three kind of situations, and a new approach to calculate the shear strength parameters is obtained according to the fact that the quadratic sum of distance between line and points in minimum, and the calculating formulae and applying scopes of three different calculating methods are also put forward. A calculating case shows that there are obvious differences among different calculating methods for determining the strength parameters, and it is necessary to select the calculating method based on the observation errors.

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The influence of grain size and frictional/cohesional shear strength components on UK salt marsh substrate stability

10.5194/egusphere-egu2020-17681 ◽

2020 ◽

Author(s):

Helen Brooks ◽

Iris Moeller ◽

Tom Spencer ◽

Kate Royse

Keyword(s):

Shear Strength ◽

Salt Marsh ◽

Internal Friction ◽

Water Levels ◽

Systematic Research ◽

Surface Erosion ◽

Marsh Edge ◽

Angle Of Internal Friction ◽

Erosion Processes ◽

Ring Shear

Salt marshes attenuate waves and currents, thus protecting landward-lying constructed defences and the hinterland from incoming waves and extreme water levels. As such, understanding the stability of the marsh sedimentary platform is important, particularly as marsh edge erosion is common on many shores. To understand why marshes are losing material from their exposed fringes, we must better understand the relations between the marsh fabric and incoming hydrodynamic energy; this is likely to be strongly influenced by marsh biological, geochemical and sedimentological/geotechnical properties. Currently there is little systematic research into the within- and between-marsh variability in these properties and how they affect both marsh edge and marsh surface erosion processes.&#160;We compare Tillingham marsh, eastern England, where the sediment is clay/silt-dominated and the marsh canopy is species-rich, to Warton marsh, Morecambe Bay, NW England, where the sediment is sand/silt-dominated and the vegetation species-poor. We determine soil shear strength by applying geotechnical methods which, to the best of our knowledge, have not previously been applied to salt marsh environments. Shear box and ring shear tests are used to determine the natural- and residual (i.e. post-failure) shear strength of the substrate, respectively. This is expressed as the cohesion of the sediment and the angle of internal friction. We demonstrate that the ring shear test consistently returns a lower angle of internal friction for the substrate, which is expected for the residual angle of internal friction. However, we are also able to link this reduction in the angle of internal friction to substrate composition (e.g. root content, organic matter and particle size distribution). This enhanced methodological understanding will improve our comprehension of marsh resistance to edge erosion and thus our ability to predict future erosion. Ultimately, accurate measurements of the shear strength of natural foreshores are essential for the informed implementation of nature-based coastal flood defences, including &#8216;de-embankment&#8217;/&#8216;managed realignment&#8217; schemes.

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