Water Content Of Rocks Research Articles

Effects of rock water content on CERCHAR Abrasivity Index

Cerchar Abrasivity Index (CAI) has been commonly used to represent rock abrasion for estimation of tool wear in rock excavation applications. This test is a simple and effective measure of rock abrasion but operating parameters can impact its results. This paper focuses on the influence of water saturation on CAI values based on laboratory testing of 33 sedimentary rock units collected from different regions of Pakistan. The tests include CAI measurements as well as engineering rock properties on both dry and saturated rocks. It was found that overall 79% of CERCHAR abrasivity index values measured on saturated rock surfaces “CAIsat” were less than the CERCHAR abrasivity index values measured on dry rock surfaces “CAIdry”. Meanwhile, 52% of CAIsat values showed significant reduction from CAIdry values in the statistical analysis of CAI results with significance level of 15% (α=0.15). Regression analysis was used to correlate CAIsat values with CAIdry, normally measured in CERCHAR testing. The proposed formula can be used to estimate CAIsat from result of laboratory testing where CAI reported is often CAIdry. This could lead into more accurate estimation of tool wear and related adjustments when CAI is used for estimation of tool wear when excavation is done under wet conditions. Multiple regression was also used to establish a predictive model of CAIsat with petrographical, wear indices and geotechnical rock properties of saturated rock samples. In addition, the validity of correlations of CAI with rock properties that are already published was evaluated.

Efficiency of ionic liquids for chemical enhanced oil recovery

Substantial amount of crude oil remains in the reservoir after primary and secondary production. Chemical flooding is one of the enhanced oil recovery (EOR) methods; however, chemicals (i.e., Surfactant) used are sensitive to the harsh environment characterizing the local reservoirs. The current study aimed at investigating the utilization of ionic liquids (ILs), known as environment friendly salt with good solubility, thermal stability and effective surface activity, as an alternative to conventional organic surfactants in enhanced oil recovery process. In this work, screening tests of nine ILs were performed. These ILs were diluted in different brine solutions of different salt compositions at 10 % (w/w) salinity and their solubility, thermal stability and surface activity in presence of Saudi medium crude oil were tested. Tetra alkyl ammonium sulfate known as Ammoeng 102 was found to be the ionic liquid of choice. Further investigations on Ammoeng 102 solutions at 10 and 20 % (w/w) salinity were conducted and IFT measurements indicate enhanced surface activity of Ammoeng 102 with increasing solution salinity. Effects of pressure and temperature on interfacial tension (IFT) were also tested and the results indicate minor effects. Adsorption test indicates high Ammoeng 102 adsorption tendency with more adsorption for higher salinity solution. Different flooding scenarios were conducted in sandstone rock samples to investigate the effectiveness of Ammoeng 102 IL as an EOR chemical. The findings indicate promising results for ionic solution flooding in secondary mode at irreducible water saturation (S wirr). Ultimate recovery obtained is higher than that obtained with combined secondary brine flooding followed by tertiary ionic solution flooding at residual oil saturation (S or). Injection of slug of ionic solution in secondary mode provides lower recovery compared to that recovered with continuous ionic solution injection in the same mode. Rock water content affects recovery efficiency indicating higher oil recovery for secondary brine and tertiary ionic solution flooding at low S wirr. Contact angle and relative permeability measurements demonstrate the role of wettability alteration behind the extra oil recovery which is very much affected by ionic liquid concentration that can be altered by dilution with formation and injected brines.

Las rocas blandas o de baja resistencia: la tiza como caso de análisis

The following paper presents general comments about chalk as a soft rock, emphasizing on its mechanical classification and laboratory analysis. Considerinq their caracterization, the mechanical tests analized in the laboratory were: pulse ultrasonic velocity test, point load test, uniaxial and triaxial tests at different misture contents. The pulse ultrasonic velocity test helped establish some correlation bettween the velocity and the moisture content. It was observed that when the moisture content of the chalk decreased the propagation of velocity increased (and viceversa) to an specific value of moisture content when the rock's behaviour was totally opposed. In the point load test samples on the same size but with some moisture content showed a 43% reduction in their resistance value when compared with the dry samples. In the uniaxial compressive strength test, dry and moist core samples of 50 mm diameter and 125mm length were analized. The observations showed that the rock's water content increased, the uniaxial compressive strength of 4.8 MN/m2 and those with some water content showed an average value of 2.6 MN/m2. Finally, during the triaxial test some samples with 38 mm of diameter of 76 mm of length under dry conditions and with 26 % of moisture content were compared with other samples with a diameter Of 76 mm and 152 mm of length also under dry conditions. According to the obtained data, it is possible to conclude that these samples with different diameter (38 and 76 mm) under dry conditions showed aproximately the same value of cohesion (15-17 Kgff/cm2 and a basic friction angle (34-35°). The principal difference was found in those with a moisture content of 26% which gave a lower value of cohesion (7 Kgrf/cm2)than those under dry conditions, for die presence of water reduces the strength characteristics and the cohesion of the rocks.

Hydrophilic and strength-softening characteristics of calcareous shale in deep mines

To better understand the mechanism of the strength weakening process of soft rocks in deep mines after interacting with water, a self-developed experimental system, Intelligent Testing System for Water Absorption in Deep Soft Rocks (ITSWADSR), is employed to analyze the hydrophilic behavior of deep calcareous shale sampled from Daqiang coal mine. Experimental results demonstrate that the relation between water absorption and time can be expressed by power functions, and the soakage rate decreases while the soakage increases with time. In order to quantitatively calculate the weight coefficients of the influential factors for water absorbing capacity of rocks, a series of testing methods are adopted, including scanning electron microscope (SEM), X-ray diffraction and mercury injection test. It is demonstrated that the effective porosity has a positive correlation with the water absorbing capacity of rocks and the contents of illite and illite/smectite. The initial water content presents a negative correlation with the water absorption capacity of rocks. According to the absolute value of weight coefficients of various influential factors, the order of magnitude from high to low is captured: initial water content, illite, illite/smectite formation (S=5%), and the effective porosity. After water absorption tests, uniaxial compressive strength (UCS) tests were performed on rock specimens allowing a linear relationship between the UCS and the water content of rock to be established, indicating that the strength of calcareous shale decreases linearly with the increasing water content.

Numerical modeling of thawing in frozen rocks of underground mines caused by backfilling

The thawing effect due to backfilling in permafrost mining rocks is investigated. The heat transfer equation in rock and backfill is obtained by considering the effect of phase change, heat generation due to cement hydration and temperature dependent material properties. The governing equations are solved using a finite volume numerical method and the phase change phenomenon is modeled based on the manipulation of specific heat, thermal conductivity and density of rock and backfill. The harmonic mean method was employed to handle the change of thermal properties. The effects of different influential parameters such as cement content of backfill, water content of rock and backfill, thermal conductivity of rock and filling material, and the number of adjacent stopes are investigated. Eventually, using the resulting temperature and phase field, a new parameter regarded as the radius of thawing, is introduced.

Effect of the grain-size distribution and water content of rock on the natural attenuation of diesel fuel in the vadose zone

Five simulating columns were used to investigate the effect of the grain-size distribution and water content of rock on the migration and natural attenuation of diesel fuel in the vadose layer. Natural attenuation of fuel was observed for 90 days. It was shown that as the grain size of the rock increases, the water content that cannot be replaced by diesel fuel in the rock decreases. An increase of the water content has a positive effect on the natural attenuation of diesel fuel.

Axially confined point load testing

Standard penetration test is often used as an index for prediction of geomaterial elastic and strength properties. It consists of releasing a 63.5 kg hammer from a specified distance of 762 mm on a series of connected drill rods. The N-value is defined after a total 457 mm of penetration is achieved by counting the below counts for the last 300 mm of penetration. This required penetration is not often achieved in weak rocks due to their relatively large compressive strength. To eliminate the need for achieving a total required 457 mm of penetration, a novel approach is introduced where the rate of penetration of the split spoon sampler is used for the characterization of the engineering properties of the weak argillaceous rocks. The rate of penetration is defined as the slope of the final segment of the blow count versus penetration plot. The test results show that the average penetration rate at each test depth approaches a relatively constant value as the penetration increases. It is found that penetration rate is affected by the unconfined compressive strength, deformation modulus, and water content of the rock mass as well as the mean effective stress at the elevation of each test. Using in situ tests from 21 weak rock sites in Illinois, United States, models are proposed for the prediction of deformation modulus and unconfined compressive strength based on the penetration rate. The models account for the influence of mean effective stresses and the in situ water content of rock.

Monitoring of water and heat transfer in the vadose zone of a carbonate formation: An example of an underground quarry in Gironde, France

This article studies the water and heat transfer in the vadose zone of a carbonate formation during three hydrological cycles (August 2001–May 2004). The application of the time domain reflectometry (TDR) method to determine the volumetric water content of porous rocks has been widely investigated. The study of more than 285 monthly point measurements of the rock water content during three hydrological cycles, distributed throughout an abandoned underground quarry in Gironde, France, shows a permanently undersaturated limestone (between 35% and 50%). Three periods of maximum volumetric water content correspond to the occurrence of three effective rainfall events. The phase lag and amplitude damping of the hydraulic and thermal signals with depth can be modelled and explained by the hydraulic and thermal properties of the porous medium in the unsaturated zone.

Four-year comparison of water contents beneath a grass ley and a deciduous oak wood overlying Triassic sandstone in lowland England

Differences in the seasonal water dynamics of a sand soil overlying Triassic sandstone have been investigated to a depth of 9 m beneath both a grass ley and a pendunculate oak woodland within Clipstone Forest, Nottinghamshire, England. Fortnightly measurements with a neutron-probe over a four-year period allowed a comparison of the soil–rock water content to depths rarely reported. In spring, the rate of decrease of water content of the uppermost 2 m of soil was much greater under grass than oak woodland. In contrast, the rate of decrease under oak was greater after leafing out in May, while the rate of rewetting in early autumn was lower for this land-use until senescence and leaf-fall in late autumn. In the uppermost 2 m of soil – a depth that includes all plant roots – the soil moisture minima were between 47 and 58 mm lower under oak than grass in each year of monitoring. As a result of both these drier conditions and the comparatively late leaf fall of this species, penetration of the winter-season wetting front to 2 m was delayed by between one and three months at the oak site relative to grass in years of near-average rainfall. Rewetting at 9 m lags by 10–12 months, compared to the surface, giving an average penetration rate for the wetting front to this depth of 25–30 mm day −1 , with little observable differences between the land-uses. Preferential flow is evident under both sites, affecting the profile to 3 m in all years and to at least 6 m following winters experiencing exceptional rainfall.

Modelling the migration of contaminants through variably saturated dual-porosity, dual-permeability chalk

In the Hesbaye region in Belgium, tracer tests performed in variably saturated fissured chalk rocks presented very contrasting results in terms of transit times, according to artificially controlled water recharge conditions prevailing during the experiments. Under intense recharge conditions, tracers migrated across the partially or fully saturated fissure network, at high velocity in accordance with the high hydraulic conductivity and low effective porosity (fracture porosity). At the same time, a portion of the tracer was temporarily retarded in the almost immobile water located in the matrix. Under natural infiltration conditions, the fissure network remained inactive. Tracers migrated downward through the matrix, at low velocity in relation with the low hydraulic conductivity and the large porosity of the matrix. Based on these observations, Brouyère et al. (2004a) [Brouyère, S., Dassargues, A., Hallet, V., 2004a. Migration of contaminants through the unsaturated zone overlying the Hesbaye chalky aquifer in Belgium: a field investigation, J. Contam. Hydrol., 72 (1–4), 135–164, doi: 10.1016/j.conhyd.2003.10.009] proposed a conceptual model in order to explain the migration of solutes in variably saturated, dual-porosity, dual-permeability chalk. Here, mathematical and numerical modelling of tracer and contaminant migration in variably saturated fissured chalk is presented, considering the aforementioned conceptual model. A new mathematical formulation is proposed to represent the unsaturated properties of the fissured chalk in a more dynamic and appropriate way. At the same time, the rock water content is partitioned between mobile and immobile water phases, as a function of the water saturation of the chalk rock. The groundwater flow and contaminant transport in the variably saturated chalk is solved using the control volume finite element method. Modelling the field tracer experiments performed in the variably saturated chalk shows the adequacy and usefulness of the new conceptual, mathematical and numerical model.

Measurement of the Solid Dielectric Permittivity of Clay Minerals and Granular Samples Using a Time Domain Reflectometry Immersion Method

Both porosity and water content of rocks, sediments, and soils can be estimated from measurements of the effective dielectric permittivity. To achieve accurate modeling to obtain either water content or porosity the permittivity of the solid phase must be known. Until recently the most common method of obtaining the permittivity of the solid phase of granular materials relied on packing samples in air and using a mixing model to estimate the permittivity of the solid. This approach preassumes the correctness of the mixing models that we want to test. This work develops a recently proposed immersion methodology suitable for fine‐grained mineral samples and clay minerals. Measured permittivity values were 4.4 for ground quartz, 9.1 for Iceland Spar calcite, 6.0 for biotite mica, 5.8 for phlogopite mica, 5.3 for talc, 5.1 for kaolin, 5.8 for illite, and 5.5 for montmorillonite. The methodology was found to work well other than for the high surface montmorillonite sample where the immersion polar fluid adsorbed to the clay.

Measurement of the Solid Dielectric Permittivity of Clay Minerals and Granular Samples Using a Time Domain Reflectometry Immersion Method

Both porosity and water content of rocks, sediments, and soils can be estimated from measurements of the effective dielectric permittivity. To achieve accurate modeling to obtain either water content or porosity the permittivity of the solid phase must be known. Until recently the most common method of obtaining the permittivity of the solid phase of granular materials relied on packing samples in air and using a mixing model to estimate the permittivity of the solid. This approach preassumes the correctness of the mixing models that we want to test. This work develops a recently proposed immersion methodology suitable for fine-grained mineral samples and clay minerals. Measured permittivity values were 4.4 for ground quartz, 9.1 for Iceland Spar calcite, 6.0 for biotite mica, 5.8 for phlogopite mica, 5.3 for talc, 5.1 for kaolin, 5.8 for illite, and 5.5 for montmorillonite. The methodology was found to work well other than for the high surface montmorillonite sample where the immersion polar fluid adsorbed to the clay.

High-characterization of Vadose Zone Dynamics in Limestone Underground Quarries by Time Domain Reflectometry

The aim of this paper is to study the vadose zone dynamics during a hydrological cycle. The application of the Time Domain Reflectometry (TDR) method to determine the water content of porous rock has been widely investigated. More than 657 point measurements of rock water content observed during a hydrological cycle and distributed among three abandoned underground quarries in Gironde, France show a permanently undersaturated limestone. Two periods of maximum water content correspond to two occurring effective precipitations. The dephasing and amplitude attenuation of the hydraulic wave with the depth can be modelled and explained by the physical properties of the porous medium. Maps of the spatial distribution of water content show the heterogeneity of water flow in a vadose zone.

Mechanisms and patterns of O and H isotopic exchange during hydrothermal alteration of the North Shore Volcanic Group and related hypabyssal sills, Midcontinent Rift System, Minnesota

Hydrothermal flow systems developed in volcanic and interflow sedimentary rocks in response to the emplacement of ∼1.1Ga mafic plutonic rocks during intracontinental rifting in the midcontinent region. Oxygen and hydrogen isotopic studies of the North Shore Volcanic Group (NSVG) (northeastern Minnesota) and related hypabyssal sills demonstrate the importance of both permeability and temperature in controlling isotopic exchange in the rift-related hydrothermal system. Oxygen isotopic values of mineral separates and volcanic whole rocks range from 5.5‰ to 17.7‰, and show a strong correlation with whole rock water content and intensity of hydrothermal alteration. In the shallow portion of the stratigraphic sequence, elevated δ 18O values and mineralogical alteration are confined principally to highly permeable amygdaloidal flow tops and bottoms. Massive flow interiors show little or no perturbation from δ 18O values considered normal for fresh basaltic rocks. With increased depth and temperature, isotopic exchange becomes more pervasive, δ 18O values remain elevated, and oxygen isotopic profiles show no difference between flow margins and interiors. At depths where greenschist facies mineral assemblages are found, flow margins show a reversal to δ 18O values as low as 6.6‰ and δD values decrease to <−70‰. Both increased temperature and the involvement of a relatively D-depleted fluid at depth have played a role in lowering previously elevated δ 18O and δD values. Enhanced rates for hydrogen isotopic exchange relative to oxygen are suggested by whole rock δD values that tend to be uniform throughout flows that are less than ∼7 m thick. δD profiles that parallel those of δ 18O values are found in thicker flows. The correlation between degree of hydrothermal alteration and δ 18O values suggests that solution-recrystallization was the primary mechanism of isotopic exchange in the hydrothermal system. Individual feldspar phenocrysts from a single lava flow may show a range of δ 18O values from 10.5‰ to 17.7‰, and ranges in individual altered phenocrysts may be as large as 4.8‰. Feldspar isotopic heterogeneity suggests that permeability varied on a grain to grain scale, and that flow through microfractures was important in controlling isotopic variations. Coexisting plagioclase and pyroxene from hypabyssal sills show a very steep slope on a δ 18O plagioclase– δ 18O pyroxene plot, also suggestive of kinetically dominated exchange. Assuming a fluid-buffered system in the permeable flow margins, a duration of isotopic exchange on the order of 40,000 years is calculated. This time period is short compared to the lifetime of the intrusive activity in the rift, and suggests that fluid flow was either episodic in nature, or confined to the late stages of magmatic evolution.

Application of time domain reflectometry to determination of volumetric water content in rock

Time domain reflectometry (TDR) is a widely used technique for measuring soil water content. To examine its applicability to rock, the authors applied TDR to a variety of rocks in the laboratory. The obtained relationships between the apparent dielectric constant and the volumetric water content showed a behavior that can be partly explained by the effect of gaps between the TDR probe and rock. For rocks with an effective porosity smaller than that of soil, the well‐known model presented by Topp et al. [1980] for soil tended to overestimate the water content. For such rocks it was determined that an individual calibration was needed for accurate determination of water content. If no experimental calibration is possible, frequently used mixing models may be used to establish the calibration function. Our investigations suggest that TDR showed the potential for measuring the apparent dielectric constant of rock and, further, for determining water content in rock.

Neutron Probe Calibration in Unsaturated Tuff

AbstractThe measurement of water content in unsaturated media using neutron moisture probes requires a calibration relationship between neutron counts and water contents. Techniques for obtaining the relationship in unconsolidated geologic media may be unsuitable for consolidated media due to the difficulty of extracting undisturbed samples for water content analysis. The calibration relationship, θ = α0 + (α1 + α2ρb)C = α3ρb, with C = neutron counts, and ρb = dry bulk density, provided a good predictor of volumetric water content, θ, for consolidated media at the Apache Leap Tuff Site. Four techniques were employed to obtain data necessary to construct this relationship. Two methods employed a neutron transport code to predict neutron counts from scattering and absorption neutron cross sections. The first method calculated cross sections from elemental compositions, while the second used cross sections obtained from rock samples placed in a graphite pile containing a neutron source. The third method used in situ neutron counts measured in two access holes constructed in unsaturated rock with known water contents estimated from rock fragments excavated surrounding the access holes using a pneumatic hammer. The fourth technique used neutron counts from crushed rock packed into containers and maintained at prescribed water contents. Neutron cross sections obtained from elemental analyses were smaller than graphite‐pile values, although the differences were insignificant at the 95% confidence level and the difference in rock water content predictions was small. The neutron transport model provided neutron count estimates consistent with in situ counts and counts from saturated crushed rock in containers.

Production rate systematics of in-situ-produced cosmogenic nuclides in terrestrial rocks: Monte Carlo approach of investigating 35Cl (n, γ) 36Cl

A model is presented to investigate the systematics of in-situ low-energy neutron-capture-produced cosmogenic nuclides in terrestrial rocks, in particular 35Cl(n, γ) 36Cl, by using a Monte Carlo neutron transport code. The model is validated by comparison of its results with experimental measurements of low-energy cosmogenic neutrons on the Earth's surface. The dependence of 36Cl production on the elemental composition and water content of rocks has been determined.

Combined chemical and physical model for plutonic devolatilization: A non-Rayleigh fractionation algorithm

Modeling of magmatic-hydrothermal processes requires the estimation of intensive parameters, the experimental determination of partition coefficients and other equilibria, and quantitative models of processes such as magmatic crystallization and devolatilization. In this paper, a new chemical model for magmatic devolatilization, based on a physical model for volatile release during second boiling, is presented. Models are presented for stable isotopes and nonchloride complexed elements. The release of volatiles during isobaric, plutonic crystallization (second boiling) has been modeled as either a batch (closed-system) or Rayleigh-fractional (open-system) process. However, when the chemical mass transfer, attendant to second boiling, is modeled in conjunction with a simple physical model involving critical percolation of the magmatic volatile phase, the mass transfer can be shown to occur as a transitional batch-fractionation process. Early devolatilization during second boiling follows a batch law as discrete bubbles grow. Depending on the depth (pressure) of intrusion, and the initial volatile content of the magma, the discrete volumes of the volatile phase will achieve a spanning cluster of volumes at some stage in devolatilization progress. When connectivity of volatile phase volumes is established, devolatilization will follow a modified fractionation law wherein a finite, rather than infinitesimal volume of the fractionating phase is in equilibrium with the melt. For devolatilization of melts of a given initial volatile concentration, increasing depth leads to later formation of a spanning cluster and increasing batch character. Extreme depletions of magmatic chlorine or deuterium, or enrichments of magmatic molybdenum or fluorine are made more probable by early establishment of spanning clusters of volatile volumes. A new algorithm for calculating the δD of hydrous phases in intrusive rocks as a function of whole rock water content predicts D depletions on the order of −100 (relative to SMOW).

Potential use of time domain reflectometry for measuring water content in rock : Hokett, S L; Chapman, J B; Russell, C E J Hydrol V138, N1/2, Sept 1992, P89–96

Potential use of time domain reflectometry for measuring water content in rock : Hokett, S L; Chapman, J B; Russell, C E J Hydrol V138, N1/2, Sept 1992, P89–96

Potential use of time domain reflectometry for measuring water content in rock

Quantifying water movement through bedrock materials requires a technique which can accurately measure water content at precise locations within the medium. Time Domain Reflectometry (TDR) is widely used to measure the water content of soil and has a measurement sensitivity which is tightly confined to the area immediately surrounding the probes. This study applies TDR to the measurement of water content in rocks. The technique was evaluated using sandstone and welded tuff in a series of laboratory experiments. A block of each rock type was instrumented with a series of evenly spaced TDR probes. Each block was first saturated with water and then allowed to air dry. The water content was determined gravimetrically using the TDR over a period of several weeks. The results indicate that the TDR technique can be used to determine the water content of rock with an accuracy comparable with that reported for the technique used in soils.