scholarly journals Instability of Compacted Residual Soil

Geosciences ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 403
Author(s):  
Sainulabdeen Mohamed Junaideen ◽  
Leslie George Tham ◽  
Chack Fan Lee
Keyword(s):  
Steady State ◽  
State Parameter ◽  
Triaxial Tests ◽  
Residual Soil ◽  
Test Results ◽  
Residual Soils ◽  
Constant Shear ◽  
Static Liquefaction ◽  
Constant Shear Stress ◽  
Stress Ratios

Static liquefaction of loose sands has been observed to initiate at stress ratios far less than the steady-state stress ratio. Different collapse surface concepts largely based on undrained triaxial test results have been proposed in the literature to explain the above instability phenomenon of loose sands. Studies of the instability behavior of fill material derived from residual soils remain limited. The present study investigated the instability behavior of a compacted residual soil using the conventional undrained triaxial tests and specially equipped constant shear triaxial tests. The test results were characterized in the p’: q: v space using the current state parameter with respect to the steady-state line for the residual soil. A modified collapse surface that has gradients varying with p’ and v was proposed for the loose residual soil to represent the instability states of undrained loading. Under constant shear stress conditions, the soil can mobilize stress ratios higher than those defined by the modified collapse surface. An instability surface was therefore presented for the instability states reached in static loading. Further, an alternative method of deducing the instability surface from the undrained stress paths was introduced.

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.

Modified state parameter for characterizing static liquefaction of sand with fines

2009 ◽  
Vol 46 (3) ◽  
pp. 281-295 ◽  
Author(s):  
D. C. Bobei ◽  
S. R. Lo ◽  
D. Wanatowski ◽  
C. T. Gnanendran ◽  
M. M. Rahman
Keyword(s):  
Critical State ◽  
Volumetric Strain ◽  
State Parameter ◽  
Confining Pressure ◽  
Log P ◽  
Test Results ◽  
Static Liquefaction ◽  
Isotropic Consolidation ◽  
Failure Line ◽  
Soil Behaviour

An experimental study was carried out to investigate the static liquefaction behaviour of sand with a small amount of plastic and nonplastic fines. Five series of tests were conducted in drained and undrained conditions. The drained test results indicate not only that the failure line coincides with the critical state, but also that the development of volumetric strain during shearing was not sensitive to the initial confining pressure. In both isotropically and anisotropically consolidated undrained tests, a so-called “reverse behaviour” was consistently observed. The results were also interpreted in the critical state framework. The critical and steady state (CS/SS) data were found to trace along the same curve in e–log( p′) space, irrespective of the stress history and effective stress paths. A comparison between the isotropic consolidation line (ICL) and critical state (CS) curve showed that a small amount of fines can significantly change the shape and position of the ICL relative to the CS curve. Furthermore, the soil behaviour manifested in both drained and undrained shearing led to the development of a modified state parameter.

Behaviour of recompacted residual soils in a constant shear stress path

2010 ◽  
Vol 47 (6) ◽  
pp. 648-661 ◽  
Author(s):  
S. M. Junaideen ◽  
L. G. Tham ◽  
K. T. Law ◽  
F. C. Dai ◽  
C. F. Lee
Keyword(s):  
Shear Stress ◽  
Soil Mechanics ◽  
Stress Path ◽  
Experimental Program ◽  
Published Data ◽  
Residual Soils ◽  
Constant Shear ◽  
Constant Shear Stress ◽  
Path Dependent ◽  
Soil Behaviour

The significance of studying soil behaviour in a constant shear stress path to understand rain-induced slope failures and debris flows has long been recognized. Studies with constant shear tests have, however, been limited, and some past results from undisturbed soils appear to show stress path–dependent volume change behaviour. The present study systematically investigates the behaviour of recompacted residual soils in a constant shear stress path using a comprehensive experimental program. It is shown that the results of this test program and previously published data can be interpreted using the concepts of critical-state soil mechanics.

Defining an appropriate steady state line for Merriespruit gold tailings

2001 ◽  
Vol 38 (4) ◽  
pp. 695-706 ◽  
Author(s):  
A B Fourie ◽  
G Papageorgiou
Keyword(s):  
South Africa ◽  
Steady State ◽  
Companion Paper ◽  
Tailings Dam ◽  
Test Results ◽  
Failure Investigation ◽  
Static Liquefaction ◽  
Flow Failure ◽  
Undrained Loading ◽  
Gold Tailings

Failure of the Merriespruit gold tailings dam in 1994 in South Africa was unusual in that never before had a gold tailings dam in South Africa failed in such a catastrophic fashion. Conventional thinking was that gold tailings would always exhibit dilative characteristics upon loading, primarily because of the method of deposition which allows significant consolidation to occur due to sun-drying. This paper demonstrates that the concept of a steady state line, which separates dilative from contractive behaviour upon undrained loading, is applicable to Merriespruit tailings. Four particle-size distributions of Merriespruit tailings were tested to determine the influence of the percent finer than 75 µm on the position of the steady state line. The tailings with the greater percentage of fines gave a steady state line that plotted above all the others, which translated to the requirement that a greater relative density was necessary to produce noncontractive behaviour than for the low-fines tailings samples. The difficulty of defining a unique steady state line for a particular tailings, due to errors in measurement of initial sizes, is illustrated and it is recommended that error bands be assigned to any steady state line. In a companion paper, evidence from the post-failure investigation is combined with the test results in this paper to explore the likelihood of static liquefaction as the cause of the Merriespruit flow failure.Key words: static liquefaction, tailings, steady state, flow failure.

Properties of Mine Tailings for Static Liquefaction Assessment

2021 ◽  
Author(s):  
Jorge Macedo ◽  
Luis Vergaray
Keyword(s):  
Mine Tailings ◽  
Mechanical Response ◽  
Fine Particles ◽  
Soil Mechanics ◽  
Small Strain ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Bender Element ◽  
Static Liquefaction ◽  
Stress Ratios

Static liquefaction has been associated with numerous recent failures of tailings storage facilities (TSFs) around the world (e.g., the 2019 Brumadinho failure). These failures lead to devastating consequences for the environment and civil infrastructure, as well as the loss of human lives. In this study, we present trends for the mechanical response of mine tailings considering a) triaxial tests, b) bender element tests, and c) consolidation tests on 53 mine tailings materials (including recent case histories). These materials have a broad range of states, particle size distributions, and compressibility. The trends are evaluated in the context of static liquefaction using critical state soil mechanics concepts, focusing on the variation of the shear strength (residual and peak), state and brittleness soil indexes, excess pore pressure indexes, instability stress ratios, and dilatancy. In particular, we highlight that mine tailings mechanical properties reflect both the properties of the particles themselves and the relative proportions of different particle sizes. For instance, the observed trends suggest that particle gradation influences the small strain stiffness and dilatancy; the proportion of voids to the size of fine particles influences strength, and particle shape affects dilatancy. Finally, we propose static liquefaction screening indexes based on the observed trends.

scholarly journals Static Liquefaction Capacity of Saturated Undisturbed Loess in South Jingyang Platform

Water ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 2298 ◽  
Author(s):  
Rui-Xin Yan ◽  
Jian-Bing Peng ◽  
Jin-Yuan Zhang ◽  
Shao-kai Wang
Keyword(s):  
Steady State ◽  
Strain Softening ◽  
Shaanxi Province ◽  
Triaxial Tests ◽  
Pore Throat ◽  
Long Distance ◽  
Particle Rearrangement ◽  
Static Liquefaction ◽  
Small Pore ◽  
Loess Landslides

According to a previous geological investigation, high-speed and long-distance loess landslides in the South Jingyang platform in Shaanxi Province are closely related to the static liquefaction of loess. Considering the typical loess landslides in this area, isotropic consolidated undrained (ICU) triaxial tests and scanning electron microscopy analyses were conducted in this study. The main conclusions are as follows: (1) The stress-strain curves indicate strong strain softening under different confining pressures. The pore water pressure increases significantly and then remains at a high level; (2) The liquefaction potential index (LPI) shows an increasing trend followed by stabilization; the larger the LPI is, the smaller the state parameter (Ψ) is. The steady-state points of the loess are in the instability region; however, the steady-state strength is not zero; (3) Based on the ICU test results, the average pore diameter decreases; the shape ratio remains essentially unchanged; and the fractal dimension and roundness show different trends. The proportions of the macropore and mesopore decrease; that of the small pore increases slightly; and that of the micropore increases significantly; (4) The compression deformation of the highly spaced pores causes rapid strain hardening. A rapid strain softening results from the pore throat blockage at the beginning of particle rearrangement and reorganization. A stable strain softening is related to the agglomeration blocking of the reconstructed pore throat in the gradually stable stage of particle rearrangement and reorganization.

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.

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.

Static liquefaction as a possible explanation for the Merriespruit tailings dam failure

2001 ◽  
Vol 38 (4) ◽  
pp. 707-719 ◽  
Author(s):  
A B Fourie ◽  
G E Blight ◽  
G Papageorgiou
Keyword(s):  
South Africa ◽  
Steady State ◽  
Companion Paper ◽  
Dam Failure ◽  
Triaxial Tests ◽  
Tailings Dam ◽  
Failure Investigation ◽  
Static Liquefaction ◽  
Gold Tailings

In 1994 the Merriespruit gold tailings dam in South Africa failed, resulting in 17 deaths. The post-failure investigation provided no explanation as to why the catastrophic flow failure, which contradicted all previous experiences of failures of gold tailings dams in South Africa, occurred. The documented history of the dam describes insufficient freeboard provision and often poor pool control, which is argued to have resulted in some areas of the dam having high in situ void ratios. Some of the undrained triaxial tests carried out on specimens obtained from zones adjacent to the failure scar exhibited nondilative behaviour. Laboratory triaxial tests that were conducted on reconstituted specimens and are reported in a companion paper defined a series of steady state lines that were dependent on the particle-size distribution of the tailings. Void ratios obtained from undisturbed samples taken during the post-failure investigation are compared with these steady state lines and it is shown that an appreciable percentage of the specimens were likely to have been contractant. The inference drawn is that a large volume of tailings was in a metastable state in situ and overtopping and erosion of the impoundment wall exposed this material, resulting in static liquefaction of the tailings and a consequent flow failure.Key words: static liquefaction, gold tailings, Merriespruit, failure.

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