The influence of pore structure, water transport properties and rock strength on salt weathering is evaluated by means of a thorough rock characterisation and a statistical analysis. The pore ...structure was described in terms of its porosity, pore size distribution (quantified by mean pore radius) and specific surface area, density and water transport was characterised by means of water permeability (saturated flow) and capillary imbibition (unsaturated flow); whilst the rock strength test was carried out using uniaxial compressive strength, compressional and shear wave velocities, dynamic elastic constants and waveform energy and attenuation were obtained from the digital analysis of the transmitted signal. A principal component analysis and a stepwise multiple regression model was carried out in order to examine the direct relationships between salt weathering and petrophysical properties. From the principal component analysis, two main components were obtained and assigned a petrophysical meaning. The first component is mostly linked to mechanical properties, porosity and density whereas the second component is associated with the water transport and pore structure. Salt weathering, quantified by the percentage of weight loss after salt crystallisation, was included in both principal components, showing its dependence on their petrophysical properties. The stepwise multiple regression analysis found that rock strength has a predominant statistical weight in the prediction of salt weathering, with a minor contribution of water transport and pore structure parameters.
The combined influence of rock fabric, pore geometry and mineralogy (petrological parameters) on transport properties in complex and heterogeneous naturally fractured rocks was studied ...experimentally. As fissure geometry quantification has rarely been addressed in most theoretical studies of transport properties, emphasis was placed on the effects of fissure geometry on both non-saturated media (capillary rise) and saturated media (permeability).
We proved that prediction of transport properties in complex rocks is not guaranteed by the estimation of the classic micro-structural variables considered in the literature and that accurate prediction can only be attained when petrological parameters are first quantified in depth, and then combined.
Principal component analysis and the regression models proposed here clearly demonstrated on the one hand that, a meaningful porous network in non-saturated media must be modelled with a combination of different geometrical capillary tubes representing the matrix (cylindrical) and the fissure (rectangular prism) and on the other hand, that in saturated media a well-in-deep fissure size quantification enabled a more accurate prediction of permeability to be made.
The experimental data confirm that transport properties and its anisotropy are closely dependent on fissure typology, textural characteristics, mineralogy and spatial distribution of the whole rock fabric elements. Enlarged-fissures weakly exert capillary suction due to the retarding effect of gravitational forces, but they are vital in controlling permeability. Cracklebreccias with small clasts, high dolomite cement content and high inter-clast fissure density exhibit strong capillary suction. However, high calcite cement produces abnormally low rates of capillary rise, due to possible pore surface contamination, together with a high contact angle effect. Good agreement between permeability and geometric factors provided a suitable basis for identifying preferred permeable directions. Additionally, we found a critical fissure density which defined the isotropic matrix permeability. We also present a new practical and simple linear model relating permeability to capillarity with meaningfully and easily estimated petrological parameters.
Results obtained in the present study demonstrated the correct identification and use of more directly related petrological variables for modelling transport properties. Moreover, the analysis of these results using multivariate analysis is considerably more demanding compared to the conventional approaches.
This paper presents a new procedure to quantify the petrology of materials with complex and heterogenic rock-fabric features. The classical methodologies for petrographic quantification by image ...analysis are not appropriate for this kind of rock due to both the high chromatic complexity of these materials and the scale with which the samples are studied. The proposed process is particularly interesting for materials with complex chromatic characteristics such as highly fractured rocks, concrete, etc. Two commercial varieties of highly fractured (brecciated) dolostones were selected for this study in order to test the designed methodology.
This new procedure is based on the analysis process of colour images obtained from mesoscopic sample scanning. Six petrographic parameters and diagrams have been designed in order to quantify the most influential aspects in compressional (
v
p) and shear (
v
s) ultrasonic wave propagation. These petrographic parameters and diagrams are: brecciation density, brecciation density map, clast size distribution, fine-grained matrix content, shape-preferred orientation and rose diagrams.
The results demonstrate that the proposed methodology is suitable for quantifying the petrography of these kinds of materials. Furthermore, the variations measured in
v
p and
v
s are fully explained by the values measured for the following parameters: brecciation density, fine-grained matrix content, clast size distribution and preferred orientation of clasts.
•Intrinsic sorptivity is used to predict water permeability.•Partial wetting of water is obtained in calcitic sedimentary rocks.•Relations relating permeability, imbibition, sorptivity, porosity and ...pore size are discussed.
The Cordovilla basin, located within the frontal thrust belt of the Betic Cordillera, SE Spain, is an elongated NW–SE graben showing discrete surface rupture generated by Holocene paleoearthquake ...activity. A main and an antithetic normal, NW–SE trending, active faults bound the basin. Paleoseismological evidence is reported on upslope-facing scarps of the antithetic fault, acting as dams to runoff, which contributed to temporary lacustrine conditions, as well as sediment uplift. The fluvial network in the area shows a poor drainage activity, whereas a present lake is dammed by the antithetic fault. The modern landscape is controlled by Holocene faulting, modifying the geological environment according to earthquake occurrence, from flat alluvial plains to lacustrine local basins. The application of the diffusion dating technique to unconsolidated sediments for the antithetic fault scarp indicates an age between 1 and 2 ka. Various geometric parameters have been obtained in order to reconstruct the paleoseismic history of the Cordovilla graben basin. The surface rupture and fault-offset values are associated with discrete active morpholineaments, parallel to the Pozohondo Fault. The Tobarra–Cordovilla segment (the structural boundary of the Cordovilla Basin) was generated by earthquakes with magnitudes (Mw) greater than 6.0, based on Wells and Coppersmith fault scarp relations.
In this study, an experimental salt weathering simulation and porous stone durability classification are proposed. There are many laboratory tests that quantify durability against salt ...crystallisation weathering action. These are usually based on the total immersion of samples into a saline solution, which is not representative of the salt weathering mechanism. An experimental test based on partial immersion is suggested. This is a comparable study of weight loss and degradation of visual appearance due to salt crystallisation using, on the one hand, a standard durability test (UNE), and, on the other, the proposed durability test. The weight loss and visual appearance in our test is comparable to the degradation of building stone. The differences between weight loss data in both tests depend on the petrophysical properties: porous media and degree of coherence.
From this testing, a new durability classification as a function of dry weight loss in the partial immersion test is proposed. Four divisions of different types of materials can be made in this classification, which quantifies salt weathering action mainly in environments and mild climatic conditions.
This study aims to understand the effect of salt and frost crystallisation on the petrophysical and durability properties of representative types of travertine and carbonate tufas. Results ...demonstrate that the studied travertines and tufas exhibit a very high durability against salt and ice crystallisation cycles, compared to carbonates rocks with similar porosity values. The variation of the loss of mass, effective porosity, capillary absorption coefficient, ultrasonic wave velocity and attenuation, and compressive strength was scarce during weathering tests. The evolution of petrophysical properties was slightly more intense after 30 cycles of salt crystallisation than 100 cycles of freeze–thaw. Petrophysical and durability properties of the travertines and carbonate tufas depend on porosity fraction and on the manner in which the vuggy porosity is connected. In the travertine facies, vuggy macropores show little connection and can be considered as separate-vug porosity. Their addition to interparticle porosity increases effective porosity and reduces their mechanical strength but does not significantly increase capillary transport and the effectiveness of salt and ice action over the stone. On the contrary, in the carbonate tufas, vugs act as touching-vug pores, as capillary imbibition coefficients reveal. However, scanning electron microscopy displays that they underwent microcracking processes related mainly to both thermal stresses and/or ice and salt pressures. These microcracks present little connection, and they do not enhance noticeably the water flow or decrease the mechanical properties. These results are finally discussed in terms of a nonlinear decay pattern, which with long periods of apparent stability might be followed by rapid and catastrophic decay.
This paper compares different experimental methods for measuring water permeability in 17 different porous building rocks. Both commercial apparatus and specially made designed permeameters are used ...for characterising intrinsic permeability and hydraulic conductivity, k, of rocks in the range of 10 super(-12) to 10 super(-4) m/s (~ 10 super(-19)-10 super(-11) m super(2) or ~ 10 super(-4)-10 super(4) mD). We use both falling head and constant head permeameter methods including the triaxial and modified triaxial tests and a classical constant head permeameter. Results showed that for very low and low permeability samples (k<10 super(-6) m/s), triaxial conditions were found the most accurate procedures and they provided similar or slightly lower permeability values than constant and falling head methods. The latter techniques were highly recommended for permeable and high permeable porous building materials. Water permeability values were also linked to effective porosity and interpreted in terms of interparticle and vugs porosity. Finally, some modifications in the apparatus and procedures were carried out in order to assess water permeability in soft materials, which involve the use of non-saturated samples.Original Abstract: Se comparan diferentes metodos experimentales para la medida de la permeabilidad al agua en rocas porosas usadas como material de construccion. Se usaron diferentes permeabilimetros, (comerciales y desarrollados especificamente) empleando los metodos triaxial, triaxial modificado, carga constante y carga variable. Se caracterizo la permeabilidad intrinseca y conductividad hidraulica, k, con valores que varian desde 10 super(-12) a 10 super(-4) m/s (~ 10 super(-19)-10 super(-11) m super(2) or ~10 super(-4)-10 super(4) mD). Para muestras poco y muy poco permeables el ensayo con celula triaxial fue el mas reproducible. Los ensayos de carga constante son muy recomendables para rocas porosas de construccion permeables y muy permeables. Ademas, se definen los parametros experimentales mas apropiados para caracterizar la permeabilidad de rocas de construccion. La permeabilidad al agua se relaciona con la porosidad efectiva y se interpreta en terminos de porosidad tipo interparticula y vugs. Finalmente, se modificaron los equipos y procedimientos para poder estimar la permeabilidad en materiales blandos.
Background
Tobacco addiction is the leading cause of preventable morbidity and mortality worldwide, but only 1 in 20 cessation attempts is supervised by a health professional. The potential ...advantages of mobile health (mHealth) can circumvent this problem and facilitate tobacco cessation interventions for public health systems. Given its easy scalability to large populations and great potential, chatbots are a potentially useful complement to usual treatment.
Objective
This study aims to assess the effectiveness of an evidence-based intervention to quit smoking via a chatbot in smartphones compared with usual clinical practice in primary care.
Methods
This is a pragmatic, multicenter, controlled, and randomized clinical trial involving 34 primary health care centers within the Madrid Health Service (Spain). Smokers over the age of 18 years who attended on-site consultation and accepted help to quit tobacco were recruited by their doctor or nurse and randomly allocated to receive usual care (control group CG) or an evidence-based chatbot intervention (intervention group IG). The interventions in both arms were based on the 5A’s (ie, Ask, Advise, Assess, Assist, and Arrange) in the US Clinical Practice Guideline, which combines behavioral and pharmacological treatments and is structured in several follow-up appointments. The primary outcome was continuous abstinence from smoking that was biochemically validated after 6 months by the collaborators. The outcome analysis was blinded to allocation of patients, although participants were unblinded to group assignment. An intention-to-treat analysis, using the baseline-observation-carried-forward approach for missing data, and logistic regression models with robust estimators were employed for assessing the primary outcomes.
Results
The trial was conducted between October 1, 2018, and March 31, 2019. The sample included 513 patients (242 in the IG and 271 in the CG), with an average age of 49.8 (SD 10.82) years and gender ratio of 59.3% (304/513) women and 40.7% (209/513) men. Of them, 232 patients (45.2%) completed the follow-up, 104/242 (42.9%) in the IG and 128/271 (47.2%) in the CG. In the intention-to-treat analysis, the biochemically validated abstinence rate at 6 months was higher in the IG (63/242, 26%) compared with that in the CG (51/271, 18.8%; odds ratio 1.52, 95% CI 1.00-2.31; P=.05). After adjusting for basal CO-oximetry and bupropion intake, no substantial changes were observed (odds ratio 1.52, 95% CI 0.99-2.33; P=.05; pseudo-R2=0.045). In the IG, 61.2% (148/242) of users accessed the chatbot, average chatbot-patient interaction time was 121 (95% CI 121.1-140.0) minutes, and average number of contacts was 45.56 (SD 36.32).
Conclusions
A treatment including a chatbot for helping with tobacco cessation was more effective than usual clinical practice in primary care. However, this outcome was at the limit of statistical significance, and therefore these promising results must be interpreted with caution.
Trial Registration
Clinicaltrials.gov NCT 03445507; https://tinyurl.com/mrnfcmtd
International Registered Report Identifier (IRRID)
RR2-10.1186/s12911-019-0972-z
Crystallisation pressure of soluble salts in porous media of a stone is one of the most important mechanisms which contributes to the deterioration of porous ornamental stones. This mechanism may ...strongly modify porous media and in addition to this may also indirectly serve to quantify the pressure crystallisation efficiency as a function of supersaturation and porous size distribution. We establish a thermodynamic model, based on Young–Laplace and Pitzer's models of pressure crystallisation:
P
C
=(Ω/
ΔV
0)+(2γ/r)
, where
Ω is the degree of supersaturation, Δ
V
0 is the increase of the molar volume,
γ the interfacial tension and
r the pore size. This model explains the variation of porous media identified in the experimental samples, taking into account both the supersaturation and size distribution in porous media that former models use separately. Data of porous media variation obtained from tested samples and fresh samples are in agreement with the thermodynamic model. For the experimental study of the modification of porous media we used a 4
m
Na
2SO
4 solution, taking into account the large temperature changes which occur in the values of the supersaturation. The modifications of the porous media were investigated using optical microscopy, SEM and mercury porosimetry.
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