Static Liquefaction Behaviour of Gold Mine Tailings

2020 ◽  
Author(s):  
Guillermo Alexander Riveros ◽  
Abouzar Sadrekarimi
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Mining Industry ◽  
State Parameter ◽  
Empirical Method ◽  
Bender Element ◽  
Preparation Methods ◽  
Static Liquefaction ◽  
Gold Mine Tailings

Static liquefaction failure of tailings impoundments has been a persistent issue for the mining industry for many decades. In this study, the monotonic shearing response and instability of gold tailings is examined through a series of constant-volume and drained direct simple shear tests on slurry-deposited and moist-tamped specimens. The experiments were carried out on both the silt and the sand tailings produced at the mill and separated for use in dam construction. Laboratory shear wave velocity measurements made by means of bender element tests were also used to relate the shearing response and strength of the tailings to an in-situ geophysical measurement. Specimen fabric differences produced by the different preparation methods do not translate into significant differences in the critical state line, liquefaction triggering, or post-liquefaction strength for the sand tailings. Additionally, common trends of undrained yield and post-liquefaction strength ratios with state parameter were observed for both the sand and the silt tailings despite their different fines contents. An empirical method to evaluate the onset of instability and the post-liquefaction strength of the tailings using shear wave velocity is proposed.

scholarly journals Shear modulus of hydrate bearing calcareous sand-fines mixture

2019 ◽  
Vol 92 ◽  
pp. 04002
Author(s):  
Litong Ji ◽  
Abraham C.F. Chiu ◽  
Lu Ma ◽  
Chao Jian
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Hydrate Formation ◽  
Confining Pressure ◽  
Specimen Preparation ◽  
Bender Element ◽  
Calcareous Sand ◽  
Bender Element Test

This article presents a laboratory study on the maximum shear modulus of a THF hydrate bearing calcareous sand (CS)–fines mixture. The maximum shear modulus was inferred from the shear wave velocity measured from the bender elements installed in a temperature-controlled triaxial apparatus. The specimen preparation procedures were specially designed to mimic the hydrate formation inside the internal pores of CS. A trial test was conducted to validate whether the shear wave velocity is a feasible parameter to monitor the formation and dissociation of hydrate in the CS-fines mixture. Based on the bender element test results, hydrate has a more profound effect than confining pressure on enhancing the maximum shear modulus of CS-fines mixture.

Automatic Shear Wave Velocity Estimation in Bender Element Testing

2016 ◽  
Vol 39 (4) ◽  
pp. 20140197 ◽  
Author(s):  
M. Finas ◽  
H. Ali ◽  
G. Cascante ◽  
P. Vanheeghe
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Estimation ◽  
Bender Element

Geogrid Stabilization of Unbound Aggregates Evaluated Through Bender Element Shear Wave Measurement in Repeated Load Triaxial Testing

2020 ◽  
Vol 2674 (3) ◽  
pp. 113-125
Author(s):  
Mingu Kang ◽  
Joon Han Kim ◽  
Issam I. A. Qamhia ◽  
Erol Tutumluer ◽  
Mark H. Wayne
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Resilient Modulus ◽  
Triaxial Tests ◽  
Triaxial Testing ◽  
Bender Element ◽  
Wave Measurement ◽  
Repeated Load ◽  
Repeated Load Triaxial

This paper describes the use of the bender element (BE) shear wave measurement technology for quantifying the effectiveness of geogrid stabilization of unbound aggregate materials with improved mechanical properties from repeated load triaxial testing. Crushed stone aggregate specimens were prepared with three different gradations, that is, upper bound (UB), mid-range engineered (ENG), and lower bound, according to the dense graded base course gradation specification in Illinois. The specimens were compacted at modified Proctor maximum dry densities and optimum moisture contents. Two geogrids with different triaxial aperture sizes were placed at specimen mid-height, and unstabilized specimens with no geogrid were also prepared for comparison. To measure shear wave velocity, three BE pairs were placed at different heights above geogrid. Repeated load triaxial tests were conducted following the AASHTO T307 standard resilient modulus test procedure, while shear wave velocity was measured from the installed BE pairs. After initial specimen conditioning, and at low, intermediate, and high applied stress states, both the resilient moduli and accumulated permanent strains were determined to relate to the geogrid local stiffening effects in the specimens quantified by the measured shear wave velocities. The resilient modulus and shear wave velocity trends exhibited a directly proportional relationship, whereas permanent strain and shear wave velocity values were inversely related. The enhancement ratios calculated for the geogrid stabilized over the unstabilized specimens showed significant improvements in mechanical behavior for the UB and ENG gradations, and a maximum enhancement was achieved for the engineered gradation specimens stabilized with the smaller aperture geogrid.

Estimating the undrained strength of sand: a theoretical framework

1995 ◽  
Vol 32 (5) ◽  
pp. 859-870 ◽  
Author(s):  
Catherine E. Fear ◽  
Peter K. Robertson
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Void Ratio ◽  
Triaxial Compression ◽  
State Parameter ◽  
In Situ Tests ◽  
Initial State ◽  
Undrained Strength

A framework for estimating the ultimate undrained steady state shear strength of sand (Su) from in situ tests, which combines the theory of critical state soil mechanics with shear wave velocity measurements, is presented. For a particular direction of undrained loading, samples of a given sand at a constant void ratio will reach the same Su, despite the magnitude of the initial effective confining stresses. Unique Su/p′ or [Formula: see text] ratios for a given direction of loading exist for a particular sand only if state parameter is constant throughout the deposit. Normalized shear wave velocity, Vs1, can be correlated with void ratio and is therefore used to estimate Su for a given initial state and direction of loading. Strengths in triaxial compression are examined in this paper; however, the same framework can be used to estimate strengths under other directions of loading. The Su–Vs1 relationship is shown to be relatively sensitive and should be used more as a screening tool rather than an accurate means of predicting Su. Vs1 is converted to equivalent values of SPT (N1)60 and CPT qc1, and the results are compared with the current methods of estimating Su. Key words : in situ testing, liquefaction, sand, undrained strength.

Dyadic wavelet analysis of bender element signals in determining shear wave velocity

2020 ◽  
Vol 57 (12) ◽  
pp. 2027-2030
Author(s):  
Guan Chen ◽  
Fang-Tong Wang ◽  
Dian-Qing Li ◽  
Yong Liu
Keyword(s):  
Wavelet Transform ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Near Field ◽  
Bender Element ◽  
Dyadic Wavelet ◽  
Wavelet Transform Modulus Maxima ◽  
Dyadic Wavelet Transform ◽  
Modulus Maxima

Determining shear wave velocity is a critical technique in bender element tests, as it can be readily affected by near-field effects, wave reflection, and other factors. This study proposes a new method based on the dyadic wavelet transform modulus maxima. Combining the local modulus maxima of dyadic wavelet transform approximate coefficients at fine decomposition levels and an appropriate threshold value, the proposed method can automatically detect the target point. For validation, a comparative study among the dyadic wavelet transform modulus maxima, peak-to-peak, first arrival, and cross-correlation methods was carried out using 140 sets of bender element signals. The comparison results show that the proposed method not only mitigates the adverse effects of near-field, later major peaks, and noise contamination, but is also more robust in estimating shear wave velocity.

scholarly journals Bender elements in stiff cemented clay: shear wave velocity (Vs) correction by applying wavelength considerations

2019 ◽  
Vol 56 (7) ◽  
pp. 1034-1041 ◽  
Author(s):  
Qasim Khan ◽  
Sathya Subramanian ◽  
Dawn Y.C. Wong ◽  
Taeseo Ku
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Near Field ◽  
Shear Stiffness ◽  
Propagation Distance ◽  
Small Strain ◽  
Bender Element ◽  
Bender Elements ◽  
Sine Signal

For the quality control of cement mixing in clays, small-strain shear stiffness Gmax is now increasingly being used due to enhanced repeatability in shear wave velocity (Vs) measurements. These stiff cemented clays have higher resonant frequencies that require the use of higher input frequencies in bender element testing for reliable Vs measurements. However, the practical requirements for suitable signals (with minimal near-field effects and wave reflections) can often be difficult to implement. To facilitate such Vs measurements, the current study proposes a methodology that can correct Vs values corresponding to lower wave propagation distance to wavelength ratios (Ltt/λ) to more reliable values of Vs at reference Ltt/λ criterion suggested in previous studies (e.g., 2, 3.33, and 4). Two clay types are mixed with ordinary Portland cement and various mix ratios are utilized to cover a wider range of soil stiffnesses. Based on the collected database, it is found that the resulting fitting functions enable the reasonable estimation of the stabilized Vs values corresponding to the suggested Ltt/λ criterion regardless of the nature of the input sine signal.

SHEAR WAVE VELOCITY BY TSP APPLIED BENDER ELEMENT TEST IN SAND

2006 ◽  
Vol 62 (1) ◽  
pp. 169-174 ◽  
Author(s):  
Toshihiro OGINO ◽  
Hiroshi OIKAWA ◽  
Toshiyuki MITACHI ◽  
Masaki TSUSHIMA ◽  
Kohta NISHIDA
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Bender Element ◽  
Bender Element Test

Shear wave velocity to evaluate in situ state of cohesionless soils

1995 ◽  
Vol 32 (5) ◽  
pp. 848-858 ◽  
Author(s):  
J.C. Cunning ◽  
P.K. Robertson ◽  
D.C. Sego
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Effective Stress ◽  
Shear Wave Velocity ◽  
Critical State ◽  
State Parameter ◽  
Worked Examples ◽  
Shear Loading ◽  
Cohesionless Soils

Shear wave velocity (Vs) measurements were carried out in a triaxial testing program on three different cohesionless soils. The Vs was measured using bender elements during consolidation and at ultimate steady state. After consolidation the soil samples were loaded in shear under constant strain rate triaxial compression either drained or undrained to determine their ultimate steady or critical state (USS) at large strains. The Vs measurements were used to develop relationships between the void ratio (e), mean normal effective stress (p′), and Vs. The shear loading results were expressed within the framework of critical state soil mechanics. The results of the Vs and USS information were combined with the state parameter concept to develop an equation to use field measured Vs to estimate the in situ consolidation state within a soil. Thus, the contractive–dilative boundary with respect to vertical effective stress for large strain loading can be determined from in situ measurements of Vs. These can then be used as a design aid to determine if a soil deposit is potentially susceptible to flow liquefaction. Worked examples to illustrate the procedure are given. Key words : shear wave velocity, cohesionless soil, in situ state, state parameter, liquefaction, laboratory testing.

Sign in / Sign up

Export Citation Format

Share Document