Slope stability in residual soils in Hong Kong

1982 ◽  
Vol 19 (4) ◽  
pp. 521-525 ◽  
Author(s):  
D. J. Sweeney ◽  
P. K. Robertson
Keyword(s):  
Shear Strength ◽  
Hong Kong ◽  
Slope Failure ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Residual Soils ◽  
Long Term Stability ◽  
Granite Residual Soil ◽  
Cut Slopes

A large number of steep, high cut slopes in residual soils exist in Hong Kong and many failures of such slopes have occurred, almost invariably during heavy rainfall. As a result, the long-term stability of many cut slopes is now in question.A brief review of past slope design and slope failure is presented.It has been found that the effective stress shear strength envelope of the Hong Kong soils is curved, particularly at low stress levels, and angles of friction are high. Shear strength results are presented from a series of multistage, consolidated drained, triaxial tests carried out on a typical decomposed Hong Kong granite residual soil. The results of the multistage tests are reviewed to assess the applicability of this type of test to residual soils.The importance of the curved shear strength envelope is discussed in relation to the observed slope failures.

EXPERIMENTAL STUDY ON NONLINEAR SHEAR STRENGTH BEHAVIOR OF A TROPICAL GRANITIC RESIDUAL SOIL (GRADE VI) AT VARIOUS INITIAL MOISTURE CONTENTS

2017 ◽  
Vol 79 (2) ◽  
Author(s):  
Pooya Saffari ◽  
Mohd Jamaludin Md Noor ◽  
Shervin Motamedi ◽  
Roslan Hashim ◽  
Zubaidah Ismail ◽  
...  
Keyword(s):  
Shear Strength ◽  
Slope Failure ◽  
Soil Mechanics ◽  
Characteristic Curve ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Strength Behavior ◽  
Non Linear ◽  
Linear Shear ◽  
Linear Envelope

The conventional theories of soil mechanics use linear envelope to derive shear strength; this however, leads to an overestimation of the factor of safety in the examination of slopes. Therefore, the incorporation of methods that acknowledge the existence of non-linear characteristics of shear strength is necessary in the analysis of slopes specifically. This is due to the substantial influence of non-linear shear strength behavior on the slope failure mechanism when they are at low stress levels. In this paper, the nonlinearity of shear strength for grade VI granitic residual soil is studied. “Non-Axis Translation Consolidated Drained Triaxial” tests were performed at various ranges of net stress and suction. Thereafter, to characterize shear strength behavior, shear strength parameters were derived. The soil-water characteristic curve was plotted after conducting “Pressure Plate Extractor” test at a series of suction. The result substantiated the non-linearity of shear strength for granitic residual soil based on net stress and suction.  

scholarly journals Stress–Strain Strength Characteristics of Undisturbed Granite Residual Soil Considering Different Patterns of Variation of Mean Effective Stress

2021 ◽  
Vol 11 (4) ◽  
pp. 1874
Author(s):  
Rongjun Shu ◽  
Lingwei Kong ◽  
Bingheng Liu ◽  
Juntao Wang
Keyword(s):  
Effective Stress ◽  
Stress Path ◽  
Strength Characteristics ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Residual Soils ◽  
Stress Strain ◽  
Tropical Regions ◽  
Granite Residual Soil ◽  
Pattern Of Variation

Granite residual soil is one of the most frequently encountered problem soils in tropical regions, whose mechanical behavior heavily depends on the pattern of variation of mean effective stress (p’) during shearing, which can be classified into three categories: increasing-p’, constant-p’, and decreasing-p’. Unfortunately, so far, the stress–strain strength characteristics of granite residual soils have been studied mainly under increasing-p’ stress paths, although it is very likely to encounter stress paths with decreasing p’ in practice, especially in excavation engineering. Moreover, most pertinent research has focused on remolded granite residual soils, whereas undisturbed specimens have not yet received enough attention. In this paper, stress path triaxial tests considering different patterns of variation of mean effective stress were conducted on an undisturbed granite residual soil. Subsequently, a variable termed loading angle was introduced to quantitatively represent stress path. The influences of stress path on the Mohr–Coulomb strength parameters, deformation characteristics, ductility, and shearing stiffness were analyzed, with an emphasis on the role of pattern of variation of mean effective stress. The experimental results show that friction angle of the soil increases while cohesion decreases with the increase in loading angle. The increase in loading angle leads to less volume contraction and smaller failure strain. During shearing, the soil exhibited a less brittle response under stress paths with smaller loading angles. The initial secant shear modulus first decreased and then increased as the loading angle increased, with the minimum shearing stiffness occurring at a certain loading angle lying between 90° and 123.7°.

scholarly journals Shear Strength Deterioration of Compacted Residual Soils under a Wind Turbine due to Drying-Wetting Cycles and Vibrations

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Yan-Ming Zhou ◽  
Zong-Wei Deng ◽  
Zi-Jian Fan ◽  
Wen-Jie Liu
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Wind Turbine ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Residual Soils ◽  
Angle Of Internal Friction ◽  
Strength Deterioration ◽  
Deterioration Characteristics ◽  
Compaction Degree

The soil beneath a wind turbine withstands not only environmental impacts but also continuous vibrations transmitted from the superstructure. This paper presents an experimental study of the deterioration characteristics of shear strengths of residual soils affected by drying-wetting cycles and continuous vibrations. A series of triaxial tests were performed on compacted residual soil specimens after various drying-wetting cycles and vibrations. The influences of drying-wetting cycles and vibrations on the shear strengths of residual soils with different compaction degrees were analyzed. The results demonstrate that the shear strength and cohesion of compacted residual soils decreased as the number of drying-wetting cycles increased, and they tended to be stable after three drying-wetting cycles. The angle of internal friction decreased linearly with the reduction of compaction degree but was generally not affected by drying-wetting cycles. The shear strength of compacted residual soils also decreased because of continuous vibrations. After 10000 vibrations, the strength was stabilized gradually. Both the cohesion and angle of internal friction showed dynamic attenuation phenomenon. Finally, a modified Mohr–Coulomb strength equation considering the effects of drying-wetting cycles and vibrations was established. This equation could be used to predict the shear strength of compacted residual soils and further estimate the embedded depth of wind turbine foundations.

Small strain stiffness for granite residual soil: effect of stress ratio

2021 ◽  
Author(s):  
Xianwei Zhang ◽  
Xinyu Liu ◽  
Lingwei Kong ◽  
Gang Wang ◽  
Cheng Chen
Keyword(s):  
Stress Ratio ◽  
Small Strain ◽  
Residual Soil ◽  
Resonant Column ◽  
Residual Soils ◽  
Column Tests ◽  
Small Strain Stiffness ◽  
Deviator Stress ◽  
Granite Residual Soil ◽  
Stress Ratios

Most previous studies have focused on the small strain stiffness of sedimentary soil while little attention has been given to residual soils with different properties. Most studies also neglected the effects of the deviator stress, which is extensively involved in civil engineering. This note considers the effects of the deviator stress on the small-strain stiffness of natural granite residual soil (GRS) as established from resonant column tests performed under various stress ratios. Although increasing the stress ratio results in a greater maximum shear modulus for both natural and remolded residual soils, remolded soil is more sensitive to changes in the stress ratio, which highlights the effects of soil cementation. The data herein offers new insights to understand the stiffness of residual soil and other weathered geomaterials.

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.

On the Hypothesis of Effective Stress in Consolidation and Strength for Unsaturated Soils

2012 ◽  
Vol 256-259 ◽  
pp. 108-111
Author(s):  
Seboong Oh ◽  
Ki Hun Park ◽  
Oh Kyun Kwon ◽  
Woo Jung Chung ◽  
Kyung Joon Shin
Keyword(s):  
Shear Strength ◽  
Soil Water ◽  
Effective Stress ◽  
Unsaturated Soils ◽  
Water Retention Curve ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Soil Behavior ◽  
Soil Water Retention Curve ◽  
Soil Water Retention

The hypothesis on effective stress of unsaturated soils is validated by consolidation strength results of triaxial tests for the compacted residual soil. The effective stress can describe the unsaturated soil behavior, which was defined from shear strength or from soil water characteristic curves. Since the effective stress from consolidation agrees with that from the shear strength, the effective stress from soil water retention curve could describe the unsaturated behavior consistently on both consolidation path and stress at failure. The effective stress can describe the entire unsaturated behavior from consolidation to failure.

Anisotropic shear strength of a residual soil of sandstone

2008 ◽  
Vol 45 (3) ◽  
pp. 367-376 ◽  
Author(s):  
Adriano Virgilio Damiani Bica ◽  
Luiz Antônio Bressani ◽  
Diego Vendramin ◽  
Flávia Burmeister Martins ◽  
Pedro Miguel Vaz Ferreira ◽  
...  
Keyword(s):  
Shear Strength ◽  
Effective Stress ◽  
Yield Surface ◽  
Triaxial Compression ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Compression Tests ◽  
Soil Stiffness ◽  
Particle Bonding

This paper discusses results of laboratory tests carried out with a residual soil originated from the weathering of eolian sandstone from southern Brazil. Parent rock features, like microfabric and particle bonding, are remarkably well preserved within this residual soil. Stiffness and shear strength properties were evaluated with consolidated drained (CID) and consolidated undrained (CIU) triaxial compression tests. Undisturbed specimens were tested with two different orientations between the specimen axis and bedding surfaces (i.e., parallel (δ = 0°) or perpendicular (δ = 90°)) to investigate the effect of anisotropy. When CID triaxial tests were performed with δ = 0°, the yield surface associated with the structure was much larger than when tests were performed with δ = 90°. Coincidently, CIU tests with δ = 0° showed peak shear strengths much greater than for δ = 90° at comparable test conditions. Once the peak shear strength was surpassed, CIU tests followed collapse-type effective stress paths not shown by corresponding tests with remolded specimens. A near coincidence was observed between the yield surface determined with CID tests and the envelope of collapse-type effective stress paths for δ = 0° and δ = 90°.

Geological and soil engineering properties of shallow landslides occurring in the Kutupalong Rohingya Camp in Cox’s Bazar, Bangladesh

Landslides ◽  
2022 ◽  
Author(s):  
A. S. M. Maksud Kamal ◽  
Farhad Hossain ◽  
Md. Zillur Rahman ◽  
Bayes Ahmed ◽  
Peter Sammonds
Keyword(s):  
Shear Strength ◽  
Bulk Density ◽  
Mineralogical Composition ◽  
Fine Sand ◽  
Liquid Limit ◽  
Engineering Properties ◽  
Anthropogenic Factors ◽  
Residual Soil ◽  
Geological Condition ◽  
Residual Soils

AbstractThe Forcibly Displaced Myanmar Nationals (FDMN), historically known as ‘Rohingya’ who fled the 2017 ethnic atrocities and genocide in the Northern Rakhine State of Myanmar, took shelter in Cox’s Bazar District of Bangladesh. The camp network, known as Kutupalong Rohingya Camp (KRC), is situated in the tectonically active tertiary hilly terrain. The KRC has been experiencing hydrometeorological hazards, where landslides are frequent. This study investigated the slopes’ geological condition, engineering properties and human interventions, which influence the landslides. The exposed slopes were relatively high (> 10 m) and steep ranging from 40° to 60° that have numerous polygonal tension cracks and fissures. From the geological and geotechnical aspects, there are three successive units of slope materials: (1) residual soils of sandy silt with clay, (2) highly weathered silty sandstones and (3) shale/clay with silt and fine sand intercalations at the bottom of the slopes. Field observations revealed that most slope failures occurred in the residual soil and weathered silty sandstone units. The residual soils have a bulk density of 1.49–1.97 g/cm3, a liquid limit of 25–48%, a plasticity index of 5–16% and an undrained shear strength of 23–46 kPa. The silty sandstones have a bulk density of 1.44–1.94 g/cm3, an internal friction angle of 34°–40° and a cohesion of 0.5–13 kPa. The mineralogical composition determined by the X-ray diffraction shows low clay mineral content, which does not affect landslides. However, the slope geometry, low shear strength with strain softening properties and torrential rainfall accompanied by anthropogenic factors cause numerous landslides every year. This study will help take proper mitigation and preparedness measures for slope protection in the KRC area and surroundings.

Effect of Water Chemical Corrosion on Strength and Cracking Characteristics of Rocks - A Review

2004 ◽  
Vol 261-263 ◽  
pp. 1355-1360 ◽  
Author(s):  
Xia Ting Feng ◽  
Shao Jun Li ◽  
Sih Li Chen
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Shear Strength ◽  
Water Chemistry ◽  
Chemical Corrosion ◽  
Long Term Stability ◽  
Effect Of Water ◽  
Triaxial Compressive Strength ◽  
Cracking Characteristics

Study of effect of water chemistry corrosion on strength and cracking characters of rocks is an important aspect to improve long-term stability of rock engineering and increase efficiency of geothermal and petroleum developing. This paper reviews new progress of study on this topic. It includes effect of water chemical corrosion on triaxial compressive strength, uniaxial compressive strength, shear strength, tensile strength, and cracking characteristics of rocks. The mechanism of water chemical corrosion is analyzed. The further study on this topic is also discussed.

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