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American Society for Testing and Materials

Statistics and Data Analysis in Geology

Discrete particle simulation of particulate systems: A review of major applications and findings


 The spectral ratio between horizontal and vertical components (H/V ratio) of microtremors measured at the ground surface has been used to estimate fundamental periods and amplification factors of a site, although this technique lacks theoretical background. The aim of this article is to formulate the H/V technique in terms of the characteristics of Rayleigh and Love waves, and to contribute to improve the technique. The improvement includes use of not only peaks but also troughs in the H/V ratio for reliable estimation of the period and use of a newly proposed smoothing function for better estimation of the amplification factor. The formulation leads to a simple formula for the amplification factor expressed with the H/V ratio. With microtremor data measured at 546 junior high schools in 23 wards of Tokyo, the improved technique is applied to mapping site periods and amplification factors in the area.

Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors.

A review of the recent advances on the treatment of industrial wastewaters by Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs)

In this study, we investigated the feasibility of jarofix [a zinc (Zn) smelter by-product] as a potential geopolymer binder in soil stabilization for road applications. Different combinations of soil–jarofix (SJ) mixtures were prepared using sodium hydroxide (NaOH), sodium silicate (Na2SiO3), and a combination of NaOH + Na2SiO3 as alkali activators. Unconfined compressive strength (UCS) tests were performed to examine the mechanical performance of SJ mixtures, and the effects of the jarofix content, curing conditions, and curing time were investigated. Changes that occurred during the geopolymerization process were further corroborated using field-emission scanning electron microscope (FESEM) images and energy-dispersive X-ray spectroscopy (EDS) analysis. Durability tests were also performed to examine the weathering resistance of selected SJ mixtures against 12 cycles of alternating wetting and drying. Based on the experimental results, the compressive strength of bare soil was increased 8.8 times, from 0.31 to 2.75 MPa, under ambient curing (AC, at 27 ± 2°C) conditions and 6 times, from 1.1 to 6.55 MPa, under dry curing (DC, at 60°C) conditions. This increase in compressive strength was attributed to the formation of sodium alumino-silicate hydrate (N–A–S–H) gel structures during the geopolymerization process, which led to a compact soil matrix, as confirmed by the FESEM images. The specimens cured under DC conditions showed greater strength improvement than those cured under AC conditions owing to the faster rate of the geopolymerization reaction at elevated temperatures. In addition, the Na2SiO3 and NaOH + Na2SiO3 solutions were found to be the most efficient alkali activators for the SJ mixtures cured under AC and DC conditions, respectively. This durability study revealed that the alkali-activated SJ mixtures exhibit a significantly smaller loss in mass than bare soil when exposed to 12 cycles of alternating wetting and drying. Moreover, the specimens cured under DC conditions were found to be more resistant to weathering than those cured under AC conditions. Overall, soil amended with 15% jarofix (through alkali activation) satisfies the minimum strength and durability criteria recommended by Indian standards for its use as a subbase and subgrade material. The current study shows that jarofix has the potential to be used as a geopolymer binder for soil stabilization, which can help the mining sector in minimizing the volume to be stored in tailings storage facilities. 

Mechanical, Microstructural, and Durability Properties of Soil Stabilized with Alkali-Activated Jarofix for Road Applications

Equivalent continuum simulation of excavations in rock mass

In this paper the compressive strength/elastic modulus of the jointed rock mass was estimated as a function of intact rock strength/modulus and joint factor. The joint factor reflects the combined effect of joint frequency, joint inclination and joint strength. Therefore, having known the intact rock properties and the joint factor, jointed rock properties can be estimated. The test results indicated that the rock mass strength decreases with an increase in the joint frequency and a sharp transition was observed from brittle to ductile behavior with an increase in the number of joints. It was also found that the rocks with planar anisotropy exhibit the highest strength in the direction perpendicular to the anisotropy and the lowest at an inclination of 30o-45o in jointed samples. The anisotropy of the specimen influences the dynamic elastic modulus more than the static elastic modulus. The results were also compared well with the published works of different authors for different type of rocks.

Static and Dynamic Elastic Modulus of Jointed Rock Mass: Influence of Joint Frequency, Joint Inclination and Joint Factor

During earthquake, soil deposits are subjected to cyclic loading. Under undrained conditions, cyclic shear stress causes transient disturbance and gives rise to an increase in excess pore water pressure leading to loss of shear strength in saturated soil deposits, there will be excessive strains with continued loss of shear strength resulting in liquefaction. Researchers have identified a significant number of cases where ground failure took place during earthquake in soil deposits containing fines leading to considerable damage to buildings. Some studies show a decrease in liquefaction resistance and others show an increase in liquefaction resistance with an increase in fines content in soil deposit. There is no clarity regarding the effect of fines. In view of this, an experimental investigation has been carried out to evaluate the liquefaction potential of sand-clay mixtures. A series of undrained stress-controlled cyclic triaxial shear tests were performed on reconstituted samples obtained from Cauvery River sand and sand mixtures containing different percentages of plastic fines up to 30%. This paper reports the results of stress-controlled cyclic triaxial shear tests under undrained conditions at 100 kPa confining pressure at a frequency of 0.1 Hz. The results show that the cyclic strength decrease with an increase in fines content upto 20% beyond which it increases. In the present investigation, the limiting fines content is 20%. The results of CRR were analyzed in terms of relative density, fines content, and plasticity characteristics. The results indicate that flow liquefaction depends on the acceleration (CSR) and initial state (void ratio).

Liquefaction Behavior of Low to Medium Plasticity Sand-Fines Mixtures

Induced desaturation has been emerging as a new liquefaction mitigation technique Laboratory study carried out, so far, on induced desaturation has mainly focused on shaking table and centrifuge studies In the present study, triaxial specimens of saturated clean sand have been desaturated by injecting air/CO2 into it and stress-controlled undrained cyclic triaxial tests have been conducted on such samples Few tests have been conducted on partly saturated samples as well It is observed that the presence of air in the sample increases the liquefaction resistance of the sand Further, desaturation affected not only liquefaction resistance but also dilative and contractive tendency of the soil Slope of the phase transformation line on compression side initially increased and then decreased with reduction in degree of saturation whereas slope of phase transformation line on extension side initially decreased and then increased with reduction in the degree of saturation In most of the cases, slope of the phase transformation line on extension side is found to be smaller than that on compression side

T. G. Sitharam

Papers

Mechanical, Microstructural, and Durability Properties of Soil Stabilized with Alkali-Activated Jarofix for Road Applications

Equivalent continuum simulation of excavations in rock mass

Static and Dynamic Elastic Modulus of Jointed Rock Mass: Influence of Joint Frequency, Joint Inclination and Joint Factor

Liquefaction Behavior of Low to Medium Plasticity Sand-Fines Mixtures

Liquefaction Resistance of Desaturated and Partly Saturated Clean Sand