Permeability Coefficient Research Articles

Influence of hydraulic pressure on pore structure evolution and chloride transport in concrete

To study the influence of hydraulic pressure on pore structure evolution and chloride transport behaviour in concrete, the mass transport depth, chloride concentration and pore characteristics of specimens with different water/cement (w/c) ratios were investigated using silver nitrate spraying, potentiometric titration, mercury intrusion porosimetry, nitrogen adsorption tests and confocal laser scanning microscopy. The results showed that the chloride concentration increased with increases in the hydraulic pressure and w/c ratio. With increasing hydraulic pressure, the transport depths of water and chloride ion transport expanded from 5.2 mm to 25.4 mm. An increase in hydraulic pressure changed the pore structure of the concrete, leading to a surge in the specific surface area, greater porosity and larger average pore diameters. Notably, ink-bottle shaped pores emerged prominently and the proportion of fine mesopores and capillary pores markedly increased after the application of hydraulic pressure. A relationship between the chloride diffusion coefficient and hydraulic pressure was developed and a relationship between the modified permeability coefficient and hydraulic pressure was constructed based on the mesoporous contribution to express the hysteresis effect of chloride.

Interrelation between compressibility and permeability of reconstituted sandy clays with different sand fractions

It has been well recognized that sand particles significantly affect the mechanical properties of reconstituted sandy clays, including the hosted clay and sand particles. However, interrelation between the permeability and compressibility of reconstituted sandy clays by considering the structural effects of sand particles is still rarely reported. For this, a series of consolidation-permeability coefficient tests were conducted on reconstituted sandy clays with different sand fractions (), initial void ratio of hosted clays () and void ratio at liquid limit of hosted clays (). The roles of in both the relationships of permeability coefficient of hosted clay () versus effective vertical stress () and void ratio of hosted clay () versus were analyzed. The results show that the permeability coefficient of reconstituted sandy clays () is dominated by hosted clay (). Both and affect the of sandy clays by changing the at any given . Due to the partial contacts and densified clay bridges between the sand particles (i.e. structure effects), the in sandy clays is higher than that in clays at the same σ′v. The relationship of sandy clays is independent of and , but is a function of . The types of hosted clays affect the of sandy clays by changing the . Based on the relationship between permeability coefficient and void ratio for the reconstituted clays, an empirical method for determining the is proposed and validated for sandy clays. The predicted values are almost consistent with the measured values with = 0.6 - 2.5.

Power feasibility of single-staged full-scale PRO systems with hypersaline draw solutions

Pressure retarded osmosis (PRO) is a process that allow to generate energy from osmotic gradient. This process uses selective membranes in order to produce electrical energy through a hydraulic turbine. PRO can be used as a renewable energy technology where water resources are inexhaustible. PRO has the advantage of knowing when and how much energy will be produced. Unfortunately at the moment there are certain limiting factors concerning membrane and module characteristics that have prevented PRO to be fully exploited at full-scale. This study aims to assess the impact of hypersaline draw solutions (60–180 g L−1), membrane characteristics such as structural parameter, module membrane surface and permeability coefficients on the net energy generated by single-staged full-scale PRO system with up to 8 spiral wound membrane modules (SWMMs) in series in a pressure vessel. To carry out this study, characteristics of existing PRO membranes at lab-scale were scaled up to 8 inches SWMM. The results showed the change in the optimal operating parameters with the change of membrane characteristics and draw solution concentration. This study concluded that single-staged full-scale PRO process would be viable from an energy point of view if membranes were manufactured on an industrial scale and with the characteristics of existing membranes on a laboratory scale.

Anti-seepage performance and underlying mechanism of carboxymethyl cellulose sodium-modified bentonite in hydraulic engineering applications

Bentonite is widely utilized in hydraulic engineering projects. However, its performance may deteriorate under extreme environmental conditions. Hence, we aim to develop a sodium carboxymethyl cellulose (CMC)-modified bentonite and investigate its anti-seepage performance. The results showed that the 10% CMC-modified bentonite exhibited the best performance. Compared with unmodified bentonite, the expansion index of 10% CMC-modified bentonite significantly increased to 40 mL/2 g, indicating a high water absorption capacity and expansion property. Moreover, it showed a significant decrease in permeability coefficient (3.72×10−11 m/s) and an increase in porosity (1.90), indicating its excellent anti-seepage effect. Furthermore, under unconventional environmental conditions and long-term performance tests, the 10% CMC-modified bentonite shows improved stability compared to the unmodified bentonite. Therefore, it can be concluded that this study provides support for the utilization of CMC-modified bentonite in anti-seepage engineering and hydraulic engineering applications.

Effects of Three Kinds of Carbohydrate Pharmaceutical Excipients-Fructose, Lactose and Arabic Gum on Intestinal Absorption of Gastrodin through Glucose Transport Pathway in Rats.

Some glucoside drugs can be transported via intestinal glucose transporters (IGTs), and the presence of carbohydrate excipients in pharmaceutical formulations may influence the absorption of them. This study, using gastrodin as probe drug, aimed to explore the effects of fructose, lactose, and arabic gum on intestinal drug absorption mediated by the glucose transport pathway. The influence of fructose, lactose, and arabic gum on gastrodin absorption was assessed via pharmacokinetic experiments and single-pass intestinal perfusion. The expression of sodium-dependent glucose transporter 1 (SGLT1) and sodium-independent glucose transporter 2 (GLUT2) was quantified via RT‒qPCR and western blotting. Alterations in rat intestinal permeability were evaluated through H&E staining, RT‒qPCR, and immunohistochemistry. Fructose reduced the area under the curve (AUC) and peak concentration (Cmax) of gastrodin by 42.7% and 63.71%, respectively (P < 0.05), and decreased the effective permeability coefficient (Peff) in the duodenum and jejunum by 58.1% and 49.2%, respectively (P < 0.05). SGLT1 and GLUT2 expression and intestinal permeability remained unchanged. Lactose enhanced the AUC and Cmax of gastrodin by 31.5% and 65.8%, respectively (P < 0.05), and increased the Peff in the duodenum and jejunum by 33.7% and 26.1%, respectively (P < 0.05). SGLT1 and GLUT2 levels did not significantly differ, intestinal permeability increased. Arabic gum had no notable effect on pharmacokinetic parameters, SGLT1 or GLUT2 expression, or intestinal permeability. Fructose, lactose, and arabic gum differentially affect intestinal drug absorption through the glucose transport pathway. Fructose competitively inhibited drug absorption, while lactose may enhance absorption by increasing intestinal permeability. Arabic gum had no significant influence.

Preparation and intestinal absorption mechanism of self-assembled nanoparticles of Herpetospermum caudigerum

In this experiment, the micro-precipitation method was used to prepare self-assembled nanoparticles of Herpetospermum caudigerum Wall.(MP-SAN). The process was optimized using average particle size and polydispersity index(PDI)as evaluation indexes. The mean particle size, PDI,zeta potential, and microstructure of MP-SAN were characterized. The intestinal absorption mechanism of dehydrodiconiferyl alcohol(DA)and herpetrione(Her)in MP-SAN was investigated through single-pass intestinal perfusion in rats. The optimized process parameters for producing MP-SAN were a stirring speed of 800 r·min~(-1),stirring time of 5 min, and rotary evaporation temperature of 40℃. The resulting MP-SAN exhibited a spherical-like structure and uniform morphology, with a mean particle size of(267.63±13.27) nm, a PDI of 0.062 0±0.043 9,and a zeta potential of(-46.18±3.66) mV. The absorption rate constant(K_a)and apparent permeability coefficient(P_(app))of DA in the ileal segment were significantly higher than those in the jejunal segment(P&lt;0.05). However, there was no significant difference in the absorption of Her between the ileal and jejunal segments. Intestinal absorption parameters of DA and Her tended to increase with increasing drug concentration. Specifically, the K_a and P_(app) of DA in MP-SAN in the high-concentration group were significantly higher than those in the low-concentration group(P&lt;0.01). The addition of verapamil, a P-glycoprotein inhibitor, did not significantly affect the intestinal absorption of DA and Her. However, the absorption of both DA and Her in MP-SAN was significantly increased by the addition of indomethacin(P&lt;0.05),suggesting that DA and Her may be substrates for multidrug resistance-associated protein 2.

Durability Analysis of Concrete Cutoff Wall of Earth-Rock Dams Considering Seepage and Dissolution Coupling Effect

In this paper, a novel numerical model for characterizing the seepage and dissolution coupling effect on the durability of anti-seepage walls of earth-rock dams is proposed. The model considers the influence of hydraulic gradient-driven seepage on the non-equilibrium decomposition of the calcium dissolution in concrete, as well as the effects of seepage dissolution on pore structure, permeability, and diffusivity. The reasonableness of the model is validated by experimental and literature data, which is then applied to analyze the deterioration and failure processes of a concrete cutoff wall of an earth-rock dam in Zhejiang Province, China. On this basis, the seepage dissolution durability control indices of anti-seepage walls are identified. The findings demonstrate that the suggested method accurately explains the calcium leaching process in concrete. Under the seepage and dissolution coupling effect, calcium in the wall continuously decomposes and precipitates, leading to varying degrees of increases in structural performance parameters, which weaken the seepage control performance of the walls and consequently result in an increase in seepage discharge and hydraulic gradient. By proposing the critical hydraulic gradient as a criterion, the service life of the wall is projected to be 42.8 years. Additionally, the upstream hydraulic head, the initial permeability coefficient, and the calcium hydroxide (CH) content are three crucial indices affecting the durability of walls, and these indices should be reasonably controlled during the engineering design, construction, and operational phases.

Preparation, Physicochemical Characterization, and Stability Study of Lippia origanoides Essential Oil-based Nanoemulsion as a Topical Delivery System.

Fungal diseases are a priority in research, development, and health care, according to the WHO, mainly due to Candida spp. Essential oils (EOs) of the genus Lippia have demonstrated broad antimicrobial biological activity. Previous studies identified the anti-Candida potential of a thymol/p-cymene chemotype EO from Lippia origanoides H.B.K coded "0018". Nanoemulsions favor the biological activity of EOs and overcome limitations such as low solubility, instability against oxidizing agents, pH, light, and low permeability. To develop, characterize, and adjust a prototype of an O/W nanoemulsion containing the "0018" EO from Lippia origanoides for its evaluation in an in vitro permeability study. Nanoemulsions were obtained using a high energy high shear method. Their particle size distribution, Z potential, viscosity, pH, encapsulation efficiency (EE), thermodynamic stability and the Turbiscan Stability Index (TSI) were evaluated. The nanoemulsion prototype was adjusted to improve performance characteristics and microbiological efficacy. Thymol was used as an analyte in the EO quantification using UHPLC-DAD. An O/W nanoemulsion with hydrodynamic diameter <200 nm and polydispersity index <0.3, EE >95%, with TSI < 1.5, anti-Candida albicans efficiency >95% was obtained; permeable with a flow of 6.0264 μg/cm2/h and permeability coefficient of 1.3170x10-3 cm/h. A pharmaceutical formulation prototype is obtained that maintains the physical and physicochemical characteristics over time. Permeability is verified in an in-vitro model. It is proposed to evaluate its antifungal activity in preclinical or clinical studies as a contribution to the treatment of topical fungal diseases caused by Candida spp., through the use of biological resources and Colombian biodiversity.

A direct correlation between damage parameters and effective permeation coefficients in composite laminates

We introduce an innovative approach for determining the gas permeability of composite laminates, explicitly accounting for inter-fiber fracture. Our method forges a direct correlation between the Continuum Damage Mechanics (CDM) damage parameter for transverse inter-fiber fracture and the effective permeation coefficients, which are crucial in assessing leak tightness. This correlation stems from a geometric similarity between the ratio of the damaged material’s load-carrying capacity to that of its pristine state, and the relative projected crack length as crucial parameter for the effective permeability assessment. This CDM-based approach represents a significant advancement in directly deriving a laminate’s permeability from mechanical failure analysis results. This is essential for the design process of Type V hydrogen storage tanks. Literature-based experimental results validate the plausibility of our method, proving its effectiveness across various laminate orientations and damage scenarios. Nonetheless, the observed deviations highlight the need for detailed damage information, elaborate material characterization.

Charge-switchable cell-penetrating peptides for rerouting nanoparticles to glioblastoma treatment

Glioblastoma (GB) is one of the most lethal types of neoplasms with unique anatomic, physiologic, and pathologic features that usually persist after exposure to standard therapeutic modalities. It is biologically aggressive, and the existence of the blood-brain barrier (BBB) limits the efficacy of standard therapies. In this work, we hypothesize the potential of surface-functionalized ultra-small nanostructured lipid carriers (usNLCs) with charge-switchable cell-penetrating peptides (CPPs) to overcome this biological barrier and improve targeted delivery to brain tumor tissues. The big question is: what is the potential of CPPs in directing nanoparticles toward brain tumor tissue? To answer this question, the usNLCs were functionalized with distinct biomolecules [five CPPs, c(RGDfK) and transferrin, Tf] through electrostatic interaction and its ability as a targeting approach to BBB (HBMEC) and glioma cells (U87 cells) evaluated in terms of physicochemical properties, cellular uptake, permeability in a 2D-BBB model, and tumor growth inhibition. Monte Carlo simulations elucidated CPP adsorption patterns. The permeability studies revealed that targeted usNLCs, especially usNLCsTf and usNLCsCPP4, exhibited an increased permeability coefficient compared to the non-targeted usNLCs. Functionalized usNLCs evidenced enhanced uptake in BBB cells, with smaller CPPs showing higher internalization (CPP1 and CPP2). Similarly, functionalized usNLCs exhibited more significant cytotoxicity in glioma cells, with specific CPPs promoting favorable internalization. Analysis of the endocytic pathway indicated that usNLCsCPPs were mainly internalized by direct translocation and caveolae-mediated endocytosis. Optimal usNLCs with dual targeting capabilities to both BBB and GB cells provide a promising therapeutic strategy for GB.

Theory-based cryopreservation mode of mesenchymal stromal cell spheroids

Cryopreservation of spheroids requires development of new improved methods. The plasma membranes permeability coefficients for water and cryoprotectants determine time characteristics of mass transfer through the cell membranes, and therefore the optimal modes of cells cryopreservation. Here we proposed an approach to cryopreservation of multicellular spheroids which considers their generalized characteristics as analogues of the membranes’ permeability coefficients of the individual cells. We have determined such integral characteristics of spheroids from mesenchymal stromal cells (MSCs) as osmotically inactive volume; permeability coefficients for water and Me2SO molecules and the activation energy of their penetration. Based on these characteristics, we calculated the osmotic behavior of multicellular spheroids under cooling conditions to select the optimal cooling rate. We also determined the optimal cooling rate of spheroids using the probabilistic model developed based on the two-factor theory of cryodamage. From the calculation it follows that the optimal cooling rate of the MSC-based spheroids is 0.75°С/min. To verify the obtained theoretical estimates, we conducted experiments on freezing MSC-based spheroids under different modes. The obtained results of primary viability screening indicate that freezing at a constant linear cooling rate of 0.75–1.0°С/min gives a good result. Theoretical prediction of the spheroid osmotic behavior during cooling provided the basis for experimental verification of varying the temperature to which slow cooling should be carried out before immersion in liquid nitrogen. Slow freezing of spheroids to −40 °C followed by immersion in liquid nitrogen was shown to preserve cells better than slow freezing to −80 °C. Obtained data allow more effective use of MSC-based spheroids in drug screening and regenerative medicine.

Development and evaluation of fiber-enhanced RAP interlayer for HMA overlay treatment

To scientifically and efficiently utilize reclaimed asphalt pavement (RAP) generated during asphalt pavement maintenance, and to promote resource recycling and sustainable development, this paper developed and evaluated the Fiber-enhanced RAP interlayer for HMA overlay and preservation treatments. In this paper, RAP interlayer was designed based on the Response Surface Methodology (RSM) and the pull-out strength and the shear strength of were tested. Through double-objective optimization and analysis, the recommended proportions were determined as 2.22 kg/m2 of rubber asphalt, 10.57 kg/m2 of aggregate, and 30% RAP content. Subsequently, the effects of different basalt fiber contents on the pull-out strength, shear strength, flexural strength, fatigue life, and permeability coefficient of asphalt mixture with interlayer containing RAP were investigated. The results indicated a significant improvement in these properties with an 80 g/m2 basalt fiber content. The performance of asphalt mixture with Fiber-enhanced RAP interlayer was obviously superior to the asphalt mixture with interlayer without fiber and RAP. According to the test results of Digital Image Correlation (DIC), it was found that basalt fibers effectively reduce stress concentration, delaying the initiation and propagation of cracks.

Permeability of needle-punched nonwoven geotextiles subjected to uniaxial tensile strains

During service life, needle-punched nonwoven geotextiles are frequently subjected to uniaxial tensile strains, which may impact their permeability behavior. The basic model of the permeability coefficient in nonwoven geotextiles is extended to the uniaxial tensile strain condition. The influence of the fiber orientation distribution was considered. The model is expressed as the functions of the tortuosity fractal dimension, pore size characteristics, fiber orientation, physical parameters, and tensile strain. To address the errors in the results of traditional permeability tests attributed to the inhomogeneity and multiple layers of specimens, in-situ X-ray computed tomography (CT) was employed to acquire three-dimensional images of the geotextile during stretching. The three-dimensional imaging technique was employed to extract the microstructure, facilitating fluid flow simulations for determining the permeability of two nonwoven geotextiles, thereby validating the theoretical method. It is shown that the simulated permeability coefficient decreases slightly and then increases with increasing uniaxial tensile strain and necking ratio. The permeability theoretical model exhibits a decreasing trend and then increases around 0.3% strain. The theoretical model can accurately predict the permeability values and rate of change of geotextiles subjected to specific uniaxial tensile strains, thereby offering valuable insights and tools for their effective utilization in various engineering applications.

Numerical Simulation of Rainfall-Induced Erosion on Infiltration and Slope Stability

In slopes where a mixture of coarse and fine particles is present, the infiltration of rainfall can cause the migration of fine particles. This migration alters the hydraulic properties of the soil and has implications for slope stability. In this study, the slope under investigation is a tailings dam composed of loosely consolidated soil with a wide particle size distribution. Due to rainfall infiltration, fine particles tend to migrate within the voids of the coarse particle framework, leading to changes in hydraulic properties and inducing slope instability. The classical internal erosion constitutive model, known as the Cividini and Gioda erosion criterion, is commonly used to predict the behavior and effects of fine particle erosion in geotechnical engineering. However, certain parameters in this erosion criterion equation, such as long-term density, are challenging to obtain through experiments. To investigate the coupled evolution of seepage and erosion within landfill slopes under the influence of rainfall infiltration and to understand the mechanisms of slope instability, this research assumes the erosion of fine particle suspension and adopts the Worman and Olafsdottir erosion criterion to establish a coupled model of unsaturated seepage and internal erosion. The developed model simulates the coupled response of seepage and erosion in unsaturated landfill slopes under three different rainfall intensities. It is then combined with the infinite slope model to quantitatively analyze the impact of fine particle migration on soil permeability and slope stability. The numerical simulations provide the following findings: The Worman and Olafsdottir erosion criterion, unlike the Cividini and Gioda erosion criterion, only requires the determination of the soil’s gradation curve to estimate the erosion rate. Internal erosion primarily occurs within the leading edge of moisture penetration, accelerating the advancement of the wetting front and reducing slope stability. When the rainfall intensity is lower than the saturated permeability coefficient, the influence of internal erosion can be disregarded. However, under rainfall intensities equal to or greater than the saturated permeability coefficient, considering internal erosion results in a difference in the depth of the wetting front of up to 34.2 cm after 6 h in the R2 scenario. The safety factor without considering internal erosion is 1.12, whereas considering internal erosion yields safety factors between 1.08 and 1.09. In the R3 scenario, the difference in the depth of the wetting front reaches 53.8 cm after 6 h, with a safety factor of 1.12 without considering internal erosion and safety factors between 1.06 and 1.07 when considering internal erosion.

Polylactic Acid/Saqqez Gum Blends for Chewing Gum Applications: Impact of Plasticizers on Thermo-Mechanical and Morphological Properties.

This study investigated a blend of poly (lactic acid) (PLA) and Saqqez gum, with a weight ratio of 70:30, respectively, along with two plasticizers, acetyl tributyl citrate (ATBC) and polyethylene glycol (PEG), at three different concentrations (14%, 16% and 18% by weight of the PLA). The blend was analyzed using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile tests, water-absorption behavior (coefficients of water absorption, sorption, diffusion and permeability of the samples during 240 h) and chemical resistance (exposure to 1 mol/L HCl and 1 mol/L NaOH for 240 h). The desired elastomer blend was then used to prepare natural chewing gum, which was subsequently subjected to texture profile analyzer (TPA) tests and sensory evaluation. The results showed that the addition of both plasticizers increased the tensile properties of the blend. Compared to neat PLA, all the blends exhibited an increase in elongation at break and a decrease in yield strength, with the maximum elongation at break (130.6%) and the minimum yield strength (12.2 MPa) observed in the blend containing 16% ATBC. Additionally, all the thermal attributes studied, including Tg, Tc and Tm, were lower than those of neat PLA, and the Tg values deviated from the values predicted via Fox's equation. SEM images of the blends confirmed that plasticization improved the homogeneity and distribution of the components in the blend structure. PEG 18% and ATBC 16% exhibit the highest and lowest water-absorption behavior, respectively. Regarding chemical resistance, all blends showed weight gain when exposed to HCl, while no weight loss was observed for resistance to NaOH. The chewing gum sample obtained similar values for the mentioned tests compared to the commercial control sample. Overall, the results indicate that plasticization enhances the structure and performance of the PLA/Saqqez gum blend and further investigation is warranted.

Slope stability considering multi-fissure seepage under rainfall conditions

Fissures form the channel for rainwater infiltration, which accelerate the infiltration of rainwater into slope bodies, hence its important impact on the seepage field and stability of the slope. In this paper, taking one landslide of Liang-Wan freeway as the research object, firstly, the equivalent permeability coefficient method is used to homogenize the fissured soil. Then considering the boundary conditions of rainfall infiltration and groundwater level, a fluid–structure coupling model is established based on saturated–unsaturated seepage theory, and evolution characteristics of seepage, displacement and stress of the slope are studied. Based on these, the slope stability coefficient is determined. The results show that the rising rate of pore water pressure and volume water content of topsoil increases when multi-fissure seepage is considered, and the pore water velocity is larger in the local seepage range of fissures. With the increase of buried depth, the closer to groundwater level, the influence of multi-fissure seepage gradually weakens. The theoretical calculation results of slope displacement are more consistent with the field monitoring results. With the increase of rainfall time, the stability coefficient of slope decreases gradually, and the rate and range of decrease are greater.

Structure regulation of PDMS coating on PTFE membrane surface to achieve efficient separation of gaseous peppermint aromatic water

This study harnessed polydimethylsiloxane (PDMS)-coated polytetrafluoroethylene (PTFE) composite (PDMS/PTFE) membranes for the separation of peppermint aromatic water in vapor state. The effects of the PDMS coatings’ morphology structure on the separation performance of the membrane were investigated. The vapor permeation process, selective-permeation mechanism, and membrane stability were explored. Results showed that the separation effect of the membranes depended on the degree of polymerization of PDMS coating. Almost no water molecules can pass through the membrane during the 6 h separation process, and the separation factor was as high as 668. The main pharmacodynamic components in the separated permeate were L-menthol, L-menthone, and menthyl acetate, accounting for 49.16 %, 26.3 %, and 5.46 %, respectively, which conformed to the standard of the European Pharmacopoeia. The parameters of membrane separation showed that the maximum permeability coefficients of L-menthol, L-menthone, menthyl acetate, and water were 40.80, 20.28, 4.211, and 0.3945, respectively, at 105 °C and 65 kPa. This finding indicated that the large difference in permeability coefficient was the key to the excellent selectivity of the PDMS/PTFE membrane for separating volatile pharmaceutical components and water molecules in the peppermint aromatic-water system.

The evolution of fractures in deep, weakly cemented overlying strata and the characteristics of severe and mild fracture zones

Fracture development in the overlying strata of a quarry is a key factor leading to aquifer water loss. Clearly understanding the fracture characteristics of deeply weakly cemented overburden is of significant importance for water-preserved mining. In order to investigate further the laws governing fracture evolution and zoning characteristics of deep, weakly cemented overlying strata, research methods, including theoretical analysis, numerical simulation, and engineering measurement, are employed. The calculation method of seepage velocity is derived by using the formula for the vertical permeability coefficient of the mining aquiclude. Based on the relationship between the seepage velocity of the aquiclude and the recharge velocity of the overlying aquifer under critical water conservation conditions, a quantitative formula characterizing the water-blocking capacity of the aquiclude is proposed. It is found that the variation in permeability of the aquiclude is negatively correlated with the distance from the working face. Consequently, the fracture zoning characteristics of deeply weakly cemented overburden rock, centered around the water-blocking capacity of fractured rock strata, are summarized. The simulation analysis of the evolution of fractures in overlying rock reveals that the compaction range of fractures increases as the working face lengthens. However, the overall development range of fractures remains largely unchanged. Additionally, the expansion of the tensile fracture range occurs solely in the vertical direction as mining height increases, while the compaction range of fractures gradually diminishes. Microseismic monitoring indicates higher incidences of fractures in the structural equilibrium zone and severe fracture zone, with more frequent occurrences of tensile and shear failures. Conversely, the mild fracture zone exhibits fewer occurrences of fractures.

Effects of granite stratum with different weathering levels on water discharge in metro tunnels

This paper proposes a method for calculating the water discharge in metro tunnels considering limited drainage. With this method, groundwater resources and vegetation can be protected on the premise of ensuring the structural safety of tunnel linings. The water discharge in drainage-limited tunnels constructed through weathered granite was investigated. The water discharge characteristics were explored under different parameters of the shotcrete layer and grouting ring. The effects of the thickness and permeability coefficient of the weathered granite strata on the water discharge in the tunnel were discussed and the results were validated by in-situ monitoring of the water discharge. The results showed that the water discharge decreases with the increase in the thickness ratio of the grouting ring and shotcrete layer and with the decrease in the permeability coefficient ratio of the shotcrete layer and grouting ring. The water discharge can be effectively reduced by increasing the thickness or decreasing the permeability coefficient of the grouting ring. Once the ratio of the grouting ring to the thickness of the shotcrete layer exceeds 20, the water discharge no longer decreases significantly, and by tuning the parameters of the grouting ring, tunnel construction costs can be reduced without affecting the groundwater resource or vegetation around the tunnel. The proposed method can serve as a basis for regulating the water discharge in tunnels located in ecologically fragile regions.

Concentration properties of biopolymers via dead-end forward osmosis

Extracellular polymeric substances (EPSs) in excess sludge of wastewater treatment plants are valuable biopolymers that can act as recovery materials. However, effectively concentrating EPSs consumes a significant amount of energy. This study employed novel energy-saving pressure-free dead-end forward osmosis (DEFO) technology to concentrate various biopolymers, including EPSs and model biopolymers [sodium alginate (SA), bovine serum albumin (BSA), and a mixture of both (denoted as BSA-SA)]. The feasibility of the DEFO technology was proven and the largest concentration ratios for these biopolymers were 94.8 % for EPSs, 97.1 % for SA, 97.8 % for BSA, and 98.4 % for BSA-SA solutions. An evaluation model was proposed, incorporating the FO membrane's water permeability coefficient and the concentrated substances' osmotic resistance, to describe biopolymers' concentration properties. Irrespective of biopolymer type, the water permeability coefficient decreased with increasing osmotic pressure, remained constant with increasing feed solution (FS) concentration, increased with increasing crossing velocity in the draw side, and showed little dependence on draw salt type. In the EPS DEFO concentration process, osmotic resistance was minimally impacted by osmotic pressure, FS concentration, and crossing velocity, and monovalent metal salts were proposed as draw solutes. The interaction between reverse diffusion metal cations and EPSs affected the structure of the concentrated substances on the FO membrane, thus changing the osmotic resistance in the DEFO process. These findings offer insights into the efficient concentration of biopolymers using DEFO.