Crushed Tuff Research Articles

A New Approach for Classifying the Permanent Deformation Properties of Granular Materials under Cyclic Loading

A series of medium-sized cyclic triaxial tests were performed to investigate the permanent deformation properties of granular materials. The strain rate was then plotted against loading cycles to classify the permanent deformation properties of granular materials under different cyclic stress ratios (CSRs). It was found that (1) the permanent strain rate dεp/dN was linearly correlated with loading cycles N using a double-log coordinate on the condition of CSR < 60%; (2) the deformation tendency factor β, which was extracted from the linear relationship between dεp/dN and N, significantly varied with CSR and, thus, can be adopted to identify the deformation states; (3) β > 1 implying that permanent strain accumulation ceases in limited cycles and corresponds to the plastic shakedown range, while 0 < β ≤ 1 indicates the temporary steady state, corresponding to the plastic creep range; (4) sluggish decrease or remarkable increase in dεp/dN appeared as CSR ≥ 60%, leading to soil collapsed in limited loading cycles and resulting in an incremental collapse range. The new approach was validated by the crushed tuff aggregates and subgrade materials reported previously. It is expected that the new approach will have wider applicability than the traditional one and can provide technical guidance for the design and construction of substructures in roadway and railway engineering.

Noble gas adsorption to tuff

A method was developed to measure trace noble gas element adsorption to the surfaces of geologic materials in the presence of a background gas that could potentially compete for surface adsorption sites. Adsorption of four noble gas elements (Ne, Ar, Kr, and Xe) at a concentration of 100 ppm in helium and nitrogen were measured on a sample of crushed tuff at 0, 15, 30, and 45 °C. In addition, Ne, Ar, Kr, and Xe at 250 ppm and 500 ppm in nitrogen at 15 °C were measured. Noble gas adsorption was found to increase with increasing atomic mass and decreasing temperature. It was also observed that the relative increase in noble gas element adsorption with decreasing temperature tends to increase with increasing atomic mass. As the noble gas concentrations in nitrogen increased, adsorption increased in a slightly non-linear fashion which could be modeled using a Freundlich isotherm. For noble gas concentrations that were ≤100 ppm Henry's Law constant were calculated.

The effects of suction history on the cyclic behavior of unsaturated road base filling materials

Road base is usually subjected to cyclic traffic loadings as well as environment loads. Evidence shows that excessive permanent deformation of the road base may occur under the action of traffic loads and the complicated suction history induced by climate change. Currently, how the suction history of road base affects its long-term deformation remains unclear. To gain a deep understanding of the long-term deformation of road base, cyclic loading tests were conducted on the road base aggregates (mixture of crushed tuff aggregates and clay fines) under controlled suction and suction histories. A large-size soil-water characteristic curve (SWCC) test apparatus was designed and manufactured for the water retention test of the large-size specimen, and the large-diameter cyclic triaxial testing system (LDCTTS) was upgraded with the unsaturated control system to control the matric suction and suction history during the cyclic loading test. Test results show that the permanent axial strain of the mixture has a negative correlation with the current suction and maximum suction history. The effect of drying-wetting cycles on the permanent axial strain is significant. The permanent axial strain decreases with drying-wetting cycles at the drying path, while increases with drying-wetting cycles at the wetting path. The resilient modulus increases significantly with the current suction magnitude while is independent of the suction history.

Impact and Improvement of Crushed Tuff Sand on Sulfate Resistance of Cement Concrete at Low Temperature

AbstractExperimental tests were conducted to study the thaumasite formation of sulfate attack (TSA) erosion resistance of cement concrete made with crushed tuff sand. Different specimens made with ...

Effects of moisture content on the cyclic behavior of crushed tuff aggregates by large-scale tri-axial test

The crushed rock aggregates are widely used as road base and subbase fillings of road. The moisture content of the crushed aggregates changes due to rainfalls and water infiltration from the pavement cracks during the road service period, and this usually brings detrimental effects to the performance of road base and subbase. To investigate the effects of moisture content on the resilient modulus and accumulated strain of crushed aggregates under cyclic loadings, comparative experiments on samples under optimum moisture condition and saturated condition were conducted through a large-scale tri-axial apparatus. Different cyclic stress amplitudes, confining pressures and initial deviatoric stresses were also considered in the experiments. Test results show that the change from optimum to saturated moisture content aggravates the accumulated axial strain and reduces the resilient modulus of the aggregates under cyclic loading. The influence of moisture content on the cyclic behavior of CTAs is related to the factors such as cyclic stress ratio and initial deviatoric stress.

Formulation and microstructural evaluation of tuff repair mortar

Abstract The purpose of this study was to develop a compatible repair mortar for two lithotypes of Peracica tuff (Slovenia): fine-grained and coarse-grained. Mineralogical–petrographic characterization of tuff was carried out via optical microscopy and X-ray powder diffraction, and the relevant physical–mechanical properties of tuff and repair mortars were determined: capillary water absorption, water absorption at atmospheric pressure, open porosity, compressive strength and resistance to salt crystallization. A repair mortar was prepared by mixing crushed Peracica tuff and quartz sand, with different grain size and mass ratios, and ethyl silicate (KSE 500 STE, Remmers) as a binder. The results showed that with an appropriate combination of crushed tuff, quartz sand and ethyl silicate, a compatible repair mortars can be obtained for both lithotypes.

Three‐Dimensional Multiphase Segmentation of X‐Ray CT Data of Porous Materials Using a Bayesian Markov Random Field Framework

Advancements in noninvasive imaging methods such as X‐ray computed tomography (CT) have led to a recent surge of applications in porous media research with objectives ranging from theoretical aspects of pore‐scale fluid and interfacial dynamics to practical applications such as enhanced oil recovery and advanced contaminant remediation. While substantial efforts and resources have been devoted to advance CT technology, microscale analysis, and fluid dynamics simulations, the development of efficient and stable three‐dimensional multiphase image segmentation methods applicable to large data sets is lacking. To eliminate the need for wet–dry or dual‐energy scans, image alignment, and subtraction analysis, commonly applied in X‐ray micro‐CT, a segmentation method based on a Bayesian Markov random field (MRF) framework amenable to true three‐dimensional multiphase processing was developed and evaluated. Furthermore, several heuristic and deterministic combinatorial optimization schemes required to solve the labeling problem of the MRF image model were implemented and tested for computational efficiency and their impact on segmentation results. Test results for three grayscale data sets consisting of dry glass beads, partially saturated glass beads, and partially saturated crushed tuff obtained with synchrotron X‐ray micro‐CT demonstrate great potential of the MRF image model for three‐dimensional multiphase segmentation. While our results are promising and the developed algorithm is stable and computationally more efficient than other commonly applied porous media segmentation models, further potential improvements exist for fully automated operation.

Physical and chemical determinants of colloid transport and deposition in water-unsaturated sand and Yucca Mountain tuff material.

Colloid mobility was determined in a system consisting of quartz sand or crushed Yucca Mountain tuff, simulated groundwater (J-13), and hydrophilic latex particles. Water content (theta) and ionic strength (I; DI water, 0.1x, 1x, 10x groundwater dilution) were manipulated to define limiting conditions for colloid transport atthe Yucca Mountain site. Colloid transport, measured with a centrifuge method at relatively high theta (saturation >36% for sand, >62% for crushed tuff) in DI water, was equivalent to transport at 100% saturation measured with conventional columns. When variables were isolated, increasing I and decreasing theta resulted in a greater extent of colloid deposition; I was more important at higher theta; physical properties were more important at lower theta. I and theta had an interactive effect on colloid deposition whereby synergism was generally observed, especially for simulated groundwater (1x); antagonism was observed at 10x groundwater dilution. At 19% moisture saturation on the crushed tuff, a decreasing rate of colloid deposition was observed. This corresponded to a hydrodynamic condition of 79% immobile water where solute tracers were excluded from a fraction of the pore volume. This suggests that a portion of the favorable sites for deposition were associated with the excluded or immobile water domain and were not accessible to colloids.

Evaporative chemical evolution of natural waters at Yucca Mountain, Nevada

The authors report results from experiments on the evaporative chemical evolution of the two major types of natural waters present at Yucca Mountain, Nevada. The first is represented by J13 well water, a dilute Na–HCO 3–CO 3 water similar to saturated horizons in volcanic tuffs across the western United States. The second is represented by Ca–C1–SO 4-rich pore water that has a higher dissolved ion content, from the unsaturated zone above the repository horizon. Data include anion and cation analysis and qualitative mineral identification for a series of open system experiments, with and without crushed tuff present, conducted at sub-boiling temperatures (75–85°C). This work is motivated by a need to characterize the chemistry of concentrated aqueous films that might form on engineered components at the potential high-level, nuclear-waste repository at Yucca Mountain, Nevada and lead to electrochemical corrosion. The experiments indicate the evolution of high pH, Na–HCO 3–CO 3 brines from J13-like waters and the evolution of near-neutral pH brines from the pore water compositions. The minerals recovered after complete evaporation of the J13 water alone experiments include amorphous silica, aragonite, calcite, halite, niter, thermonatrite and, possibly, gypsum, anhydrite and hectorite. Tachyhydrite and gypsum were observed to form in equivalent experiments with pore waters from the unsaturated zone.

Nutrient Limitation and Microbially Mediated Chemistry:Studies Using Tuff Inoculum Obtained from the Exploratory Studies Facility, Yucca Mountain

Abstract

Design of bentonite/crushed rock seals

The use of bentonite/crushed rock mixtures to form hydraulic barriers has greatly increased in recent years. To obtain an appropriate composition for such mixture sealants generally requires extensive laboratory work. Bentonite content and gradation of the crushed rock component are two key parameters in the seal design. This study investigates the effect of crushed rock gradation on the bulk porosity and permeability of systems of crushed tuff particles. Five different gradations are selected from the literature. The bulk porosity of systems of crushed tuff in the presence of bentonite is examined. The Fuller-Thompson gradations yield denser particle arrangements. For mixture samples containing 15% bentonite by weight, the amount of clay accounts for only 45 to 56% of the weight required to fill the interparticle pore space. The bentonite occupancy percentage amounts to 65 to 80% and 75 to 86.5% for samples having 25 and 35% bentonite by weight, respectively. The water content of bentonite at saturation is reduced and the resistance to piping and flow of bentonite is enhanced by the addition of clay. To reduce the bulk porosities of the mixtures containing 25% or more bentonite, a compaction energy higher than the standard Proctor compaction is necessary.

Actinide behavior on crushed rock columns

The interactions of dissolved or colloidal actinides with tuffaceous rock are being studied at Los Alamos National Laboratory in support of the Nevada Nuclear Waste Storage Investigations project. We have used small columns of crushed tuff to obtain information on the sorption of neptunium, plutonium and americium during short (<1 day) time spans. Data from these experiments supplement information obtained from longer term batch-type experiments and provide insight concerning sorption kinetics, speciation, and colloid migration. We find that Np(V), Pu(VI) and Pu(V) show limited sorption on crushed tuff. Pu(IV) polymer and Am(III) are largely retained by the tuff, with a small fraction of the imput material moving through the column as colloids.

The role of a bentonite-based packing in limiting steady radionuclide release from an underground high-level waste respository

Steady fractional release rates are calculated for an isolated waste canister protected by bentonite-based and alternative packing materials in both basalt and tuff repositories. The bentonite-based packing is shown to be superior to either crushed basalt or crushed tuff packing in reducing nuclide release. Additional fractional release rates assessing the role of the packing permeability, K p, are also studied. Nuclide release is found to be insensitive to large changes in K p, reducing concern over possible alteration of the bentonite to nonsmectite minerals.

Parametric Testing of A DWPF Borosilicate Glass

AbstractA series of tests have been performed to characterize the chemical stability of a DWPF borosilicate glass sample as part of the Waste Package Task of the NNWSI Project. This material was prepared at the Savannah River Laboratory for the purpose of testing the 165-frit matrix doped with a simulated non-radioactive waste. All tests were conducted at 90°C using deionized water and J-13 water (a tuffaceous formation groundwater). In the deionized water tests, both monoliths and crushed glass were tested at various ratios of surface area of the sample to volume of water in order to compare leach rates for different sample geometries or leaching times. Effects on the leach rates due to the presence of crushed tuff and stainless steel material were also investigated in the tests with J-13 water.