The residual shear strength of tropical soils

2006 ◽  
Vol 43 (4) ◽  
pp. 431-447 ◽  
Author(s):  
Marcelo Luvison Rigo ◽  
Rinaldo José Barbosa Pinheiro ◽  
Luiz Antônio Bressani ◽  
Adriano Virgílio Damiani Bica ◽  
Rodrigo Moraes da Silveira
Keyword(s):  
Shear Strength ◽  
Clay Fraction ◽  
Friction Angle ◽  
Tropical Soils ◽  
Plasticity Index ◽  
Residual Soils ◽  
Residual Shear Strength ◽  
Ring Shear Tests ◽  
Definition Of ◽  
Soil Behaviour

The paper discusses the residual shear strength of tropical soils. Ring shear tests have been performed with tropical soils from southern Brazil using the Bromhead apparatus. The data from the study are compared with data obtained in a comprehensive literature review of the subject. The residual friction angle of tropical residual soils from sedimentary formations decreases with increasing plasticity index following a general trend presented in the literature. Most of the residual soils described herein have also shown this trend. However, some of these residual soils, particularly basalt saprolitic soils, have shown quite low residual friction angles despite having low plasticity index and clay fraction values. It has been confirmed that the residual shear strength of tropical soils depends chiefly on mineralogy, particle size distribution, effective stress, parent rock, weathering degree, pedogenetic evolution and - when partly weathered minerals are present - degradation upon shearing. The substantial range of new data shown in the paper has allowed the definition of general boundaries of different soil behaviour in a chart of residual friction angle versus plasticity index. Each region has been associated with a different type of tropical soil.Key words: tropical soils, residual soils, residual shear strength, laboratory tests.

Long-runout mechanism and landsliding behaviour of large catastrophic landslide triggered by heavy rainfall in Guanling, Guizhou, China

2015 ◽  
Vol 52 (7) ◽  
pp. 971-981 ◽  
Author(s):  
Aiguo Xing ◽  
Gonghui Wang ◽  
Bin Li ◽  
Yao Jiang ◽  
Zhen Feng ◽  
...  
Keyword(s):  
Shear Strength ◽  
Heavy Rainfall ◽  
Source Area ◽  
Friction Angle ◽  
Shear Behaviour ◽  
Shear Tests ◽  
Long Runout ◽  
Residual Shear Strength ◽  
Ring Shear ◽  
Ring Shear Tests

A large catastrophic landslide was triggered by a heavy rainfall on 28 June 2010 in Guanling, Guizhou, China. The landslide buried two villages and killed 99 people along the runout path. The landslide involved the failure of about 985 000 m3 of sandstone from the source area, with a runout of about 1.4 km over a total vertical distance of about 420 m. To understand the possible long-runout mechanism and behaviour of the landslide, a detailed field survey of the landslide was conducted and samples were taken from the runout path. The shear behaviour of the sample based on a series of ring shear tests was examined, and numerical simulation of the landsliding behaviour by using a numerical runout model (DAN-W) was performed in which the shear strength obtained by ring shear tests was used. The experimental results reveal that the residual shear strength measured along the pre-existing shear surface is independent of the shear displacement rate under partially drained conditions, suggesting that the relationship between shear and normal stresses obeys the frictional model. A bulk basal friction angle of 14.4° at the base of the moving mass was then obtained from the test results. The simulated results show that the selected rheological model and parameters based on ring shear tests could provide the best performance in simulating the landslide. Therefore, it is expected that the model and parameters could improve the precision of hazard zonation for areas with geological, topographical, and climatic features similar to the Guanling landslide area.

scholarly journals Stabilization of Algerian Clayey Soils with Natural Pozzolana and Lime

2017 ◽  
Author(s):  
Khelifa Harichane ◽  
Mohamed Ghrici ◽  
Said Kenai
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Plasticity Index ◽  
Engineering Properties ◽  
High Plasticity ◽  
Expansive Clay ◽  
Clayey Soils ◽  
Natural Pozzolana

Cohesive soils with a high plasticity index present difficulties in construction operations because they usually contain expansive clay minerals. However, the engineering properties of soils can be improved by different techniques. The aim of this paper is to study the effect of using lime, natural pozzolana or a combination of both lime and natural pozzolana on plasticity, compaction and shear strength of two clayey soils classified as CH and CL according to the unified soil classification system (USCS). The obtained results indicated that for CH class clay soil, the plasticity index decreased significantly for samples stabilized with lime. On the other hand, for the soil classified as CL class clay, a high decrease in the plasticity index value was observed for samples stabilized with natural pozzolana compared to those stabilized with lime. Also, both the cohesion and internal friction angle in lime added samples were demonstrated to increase with time. The combination of lime and natural pozzolana exhibits a significant effect on the enhancement of both the cohesion and  internal friction angle at later stages. The lime-natural pozzolana combination appears to produce higher shear strength parameters than lime or natural pozzolana used alone.

scholarly journals Influence of the structure on the collapse potential and shear strength of a residual soil in the semiarid region of Northeast Brazil

2021 ◽  
Vol 337 ◽  
pp. 01003
Author(s):  
Valteson da Silva Santos ◽  
Allan B.Silva de Medeiros ◽  
Romário S.Amaro da Silva ◽  
Olava F. Santos ◽  
Osvaldo de Freitas Neto ◽  
...  
Keyword(s):  
Shear Strength ◽  
Expansive Soils ◽  
Friction Angle ◽  
Semiarid Region ◽  
Original Structure ◽  
Residual Soil ◽  
Residual Soils ◽  
Strength Parameters ◽  
Effective Measure ◽  
Two Samples

In the last decades, several engineering works have been developed in the Northeast of Brazil, a region marked by the occurrence of collapsible and expansive soils. This work aimed to characterize and study the behavior of two samples of residual soils collected in the municipality of Salgueiro-PE regarding their collapse potentials and shear strength parameters, in natural and disturbed conditions, evaluating the influence of the applied vertical stresses and the structural arrangement in these properties. The results obtained showed that the two samples analyzed show collapsible behavior, however, the observed potential for collapse was lower after the original structure arrangement was undone. From the direct shear strength tests, the strength parameters of the two soils were obtained, which pointed effective friction angle close to 30° and cohesive intercept close to 0 kPa. The destructuring of the samples did not cause a considerable variation in these parameters. Thus, it was possible to conclude that for these samples the microstructure has a predominant influence on the occurrence of collapsibility, but does not have the same relevance on the shear strength, such that the material’s destructuring can be considered as an effective measure to reduce the potential collapse.

scholarly journals Shear rate effect on the residual strength characteristics of saturated loess

2019 ◽  
Author(s):  
Baoqin Lian ◽  
Jianbing Peng ◽  
Qiangbing Huang
Keyword(s):  
Shear Strength ◽  
Shear Rate ◽  
Normal Stress ◽  
Rate Effect ◽  
Shear Tests ◽  
Residual Shear Strength ◽  
Shear Rates ◽  
Ring Shear ◽  
Ring Shear Tests ◽  
The Difference

Abstract. Residual shear strength of soils is an important soil parameter for assessing the stability of landslides. To investigate the effect of the shear rate on the residual shear strength of loessic soils, a series of ring shear tests were carried out on loess from three landslides at two shear rates (0.1 mm/min and 1 mm/min). Naturally drained ring shear tests results showed that the shear displacement to achieve the residual stage for specimens with higher shear rate was greater than that of the lower rate; both the peak and residual friction coefficient became smaller with increase of shear rate for each sample; at two shear rates, the residual friction coefficients for all specimens under the lower normal stress were greater than that under the higher normal stress. The tests results revealed that the difference in the residual friction angle фr at the two shear rates, фr (1)–фr (0.1), under each normal stress level were either positive or negative values. However, the difference фr(1)–фr (0.1) under all normal stresses was negative, which indicates that the residual shear parameters reduced with the increasing of the shear rate in loess area. Such negative shear rate effect on loess could be attributed to a greater ability of clay particles in specimen to restore broken bonds at low shear rates.

scholarly journals Influence of the Diatomite Specie on the Peak and Residual Shear Strength of the Fine-Grained Soil

2021 ◽  
Vol 11 (4) ◽  
pp. 1352
Author(s):  
Carlos J. Slebi-Acevedo ◽  
Daniel A. Zuluaga-Astudillo ◽  
Juan C. Ruge ◽  
Daniel Castro-Fresno
Keyword(s):  
Shear Strength ◽  
Physical And Mechanical Properties ◽  
Friction Angle ◽  
Shear Resistance ◽  
Strength Test ◽  
Residual Shear Strength ◽  
Shear Strength Test ◽  
Fine Grained ◽  
Fine Grained Soil ◽  
Mexican Species

Diatomite is a powdering mineral mainly composed of diatom microfossils present in marine and lacustrine soils, which influences their physical and mechanical properties. Although many articles have been found in the literature concerning the influence of diatomite in the overall behavior of natural soils, few research efforts have been carried out to evaluate the influence of the diatom microfossil species on their shear resistance. Therefore, in this research, the influence of the diatomite species and the content in the peak and the residual shear strength of diatomite-fine grained soil mixtures was analyzed using the annular shear strength test. Scanning electron microscopy (SEM) and Atterberg limits were also carried out as additional tests to explain the interlocking effect between the microfossils and the soil. Overall, both diatomite species increased both peak and residual shear strength of the soil similar to dense sands. Nevertheless, the Mexican species reveal higher friction angle values compared with Colombian species.

scholarly journals Influence of shear rate on the soil's shear strength

2021 ◽  
Vol 8 (1-2) ◽  
pp. 39-47
Author(s):  
Anja Bek ◽  
Goran Jeftić ◽  
Stjepan Strelec ◽  
Jasmin Jug
Keyword(s):  
Shear Strength ◽  
Shear Rate ◽  
Maximum Shear Stress ◽  
Friction Angle ◽  
Second Phase ◽  
High Plasticity ◽  
Direct Shear ◽  
Strength Parameters ◽  
Residual Shear Strength ◽  
Two Samples

One of the most important mechanical properties is shear strength. It is conditioned by the value of the maximum shear stress that the soil can withstand before failure. Exceeding the shear strength causes one particle to slide next to another, causing the failure of soil. The shear strength of the soil for effective stresses is1 a combination of drained strength parameters: internal friction angle (φ) and cohesion (c) defined by the Mohr-Coulomb failure criterion. It is determined “in situ” and by laboratory experiments. Direct shear is the oldest and the simplest laboratory experiment to determine the shear strength of the soil. The first phase of experiment is specimen consolidation under specific vertical stress, and in the second phase specimens are sheared at a given shear rate, depending on the consolidation properties of the soil. Cohesionless soils are sheared at up to 100 times higher shear rate compared to cohesive soils. Shear rate and drainage conditions affect the magnitude of soil strength parameters. The paper is based on the comparison and demonstration of the influence of different shear rates on the peak and residual shear strength in the direct shear device. The tests were performed on two samples of low plasticity clay (CL) and one sample of high plasticity clay (CH).

scholarly journals Shear rate effect on the residual strength characteristics of saturated loess in naturally drained ring shear tests

2020 ◽  
Vol 20 (10) ◽  
pp. 2843-2856
Author(s):  
Baoqin Lian ◽  
Xingang Wang ◽  
Jianbing Peng ◽  
Qiangbing Huang
Keyword(s):  
Shear Strength ◽  
Shear Rate ◽  
Normal Stress ◽  
Rate Effect ◽  
Shear Tests ◽  
Residual Shear Strength ◽  
Shear Rates ◽  
Ring Shear ◽  
Ring Shear Tests ◽  
The Difference

Abstract. Residual shear strength of soils is an important soil parameter for assessing the stability of landslides. To investigate the effect of the shear rate on the residual shear strength of loessic soils, a series of naturally drained ring shear tests were carried out on loess from three landslides at two shear rates (0.1 and 1 mm min−1). Experimental results showed that the shear displacement to achieve the residual stage for specimens with higher shear rate was greater than that of the lower rate; both the peak and residual friction coefficient became smaller with increase in shear rate for each sample; at two shear rates, the residual friction coefficients for all specimens under the lower normal stress were greater than those under the higher normal stress. Moreover, specimens with almost the same low fraction of clay (CF) showed a similar shear rate effect on the residual friction coefficient, with normal stress increasing, whereas specimens with high CF (24 %) showed a contrasting tendency, indicating that such an effect is closely associated with CF. The test results revealed that the difference in the residual friction angle ϕr at the two shear rates, ϕr(1)−ϕr(0.1) under each normal stress level are either positive or negative values, of which the maximum magnitude is about 0.8∘. However, the difference ϕr(1)−ϕr(0.1) determined under all normal stress levels was negative, which indicates that the residual shear parameters reduced with the increasing of the shear rate in the loess area. Such a negative shear rate effect on loess could be attributed to a greater ability of clay particles in specimens to restore broken bonds at low shear rates.

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 Influence of Structural Plane Microscopic Parameters on Direct Shear Strength

2018 ◽  
Vol 2018 ◽  
pp. 1-7 ◽  
Author(s):  
Yanhui Cheng ◽  
Weijun Yang ◽  
Dongliang He
Keyword(s):  
Particle Size ◽  
Shear Strength ◽  
Internal Friction ◽  
Direct Shear Test ◽  
Shear Test ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Direct Shear ◽  
Stiffness Ratio ◽  
Structural Plane

Structural plane is a key factor in controlling the stability of rock mass engineering. To study the influence of structural plane microscopic parameters on direct shear strength, this paper established the direct shear mechanical model of the structural plane by using the discrete element code PFC2D. From the mesoscopic perspective, the research on the direct shear test for structural plane has been conducted. The bonding strength and friction coefficient of the structural plane are investigated, and the effect of mesoscopic parameters on the shear mechanical behavior of the structural plane has been analyzed. The results show that the internal friction angle φ of the structural plane decreases with the increase of particle contact stiffness ratio. However, the change range of cohesion is small. The internal friction angle decreases first and then increases with the increase of parallel bond stiffness ratio. The influence of particle contact modulus EC on cohesion c is relatively small. The internal friction angle obtained by the direct shear test is larger than that obtained by the triaxial compression test. Parallel bond elastic modulus has a stronger impact on friction angle φ than that on cohesion c. Under the same normal stress conditions, the shear strength of the specimens increases with particle size. The shear strength of the specimen gradually decreases with the increase of the particle size ratio.

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