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In order to explore the diffusion law of viscosity time-denatured slurry in a dynamic water environment, taking NF cement-based slurry as the research object, the time-varying test of slurry viscosity was carried out, and the time-varying function of viscosity was determined. Based on the level set method, by customizing the viscosity time-varying function in the numerical model, the numerical simulation of dynamic water grouting considering the time-varying viscosity of the slurry is realized, and the slurry diffusion pattern and diffusion distance with and without the time-varying viscosity are obtained. The results show that the NF cement-based grouts with a water-cement ratio of 0.6 to 1.0 belong to Bingham fluid, and their viscosity increases exponentially with time. In the process of slurry diffusion, the change of slurry viscosity in the flow field shows two stages: the stable stage and the decline stage. The diffusion shape changes from circular to elliptical at the initial stage to U-shaped at the end; the slurry diffusion distance is positively correlated with time, and decreases with the decrease of water-cement ratio; the diffusion distance obtained without considering the slurry viscosity is always greater than that obtained with considering the slurry viscosity, and with the increase of grouting time, the effect of the time-varying properties of slurry viscosity on the diffusion distance is more significant.

In order to study the distribution law of the stress field in the rough fractures hiding in coal and rock mass during the grouting process, the two-dimensional rough fracture profile is generated according to the random midpoint displacement method, and a fluid-solid coupled numerical model of grouting process was established by the COMSOL software. The stress field in the fractured coal and rock mass during the process is simulated, and the influence of the roughness and the grouting rate on the stress field of the mass is analyzed. The results show that the distribution form of the stress field during the grouting process mainly depends on the fracture roughness, and the stress is larger in the sunken region than the location of protrusion. With the increase of roughness, the distribution of the stress field is more complex and the stress concentration is more obvious in the coal and rock mass. At the same time, the grouting rate also affects the stress field. The grouting velocity has a linear relationship with the stress of the mass, and the impact of grouting velocity is more obvious. With the increase of roughness, the maximum stress of coal and rock mass is gradually reduced by the influence of grouting velocity.

Abstract: A novel hydrophilic cationic chain extender, 1,4‐butanediol di(3‐diethylamino‐2‐ hydroxylpropyl alcohol) ether (BDE), was successfully prepared, and then a series of lateral‐chain‐type cationic waterborne polyurethanes (CWPUs) with high solid content was synthesized. Compared with the traditional cationic chain extender, N‐methyl diethanol amine (MDEA), BDE with lateral amino groups shows more efficient hydrophilicity and ionization properties. CWPUs prepared from BDE possess lower viscosity, smaller particle size, and larger zeta‐potential. As predicted, stable CWPU latexes with higher solids content (≥50%) and lower hydrophilic group content were achieved. Further study indicated that other properties, including the molecular weight, glass transition temperature, thermal stability, and mechanical properties, of lateral‐chain‐type CWPUs were similar or superior to those of main‐chain‐type ones; no negative effect could be observed. [ABSTRACT FROM AUTHOR]

In order to study the dynamic failure characteristics and dynamic damage characteristics of coal rocks, using split Hopkinson pressure bar(SHPB) and stress loading system, impact tests and uniaxial compression experiments were performed on coal rock samples. According to the characteristics of stress-strain experiments curve, based on the overstress model, continuous damage theory and statistical strength theory are applied to establish an overstress damage model suitable for the dynamic characteristics of coal and rock. The results show that under dynamic load, when the strain rate is small, the coal rock crushing method is similar to that under static load; as the strain rate increases, the dynamic load failure strength increases significantly, and the dynamic modulus increases first. It remains the same after being large, the plastic deformation increases first and then decreases, and the stress-strain curve has obvious plastic flow characteristics; the experimental curve is fitted using the established constitutive equation of coal rock overstress damage model, and the comparison between the two verifies the correctness of the model.

In order to study the dynamic mechanical properties of hard coal and rock in northern Shaanxi Province, the basic dynamic and static tests of coal and rock specimens were carried out by using stress loading system and split Hopkinson pressure bar (SHPB) test device, and the failure mechanism was studied. The results show that under static load, most of the coal and rock specimens are damaged by single crack, while under dynamic load, the failure forms are relatively rich, such as splitting failure at low strain rate and crushing failure at high strain rate. The correlation between elastic modulus and strain rate of peak stress is significant, but the correlation between peak strain rate is weak. Under dynamic loading mode, the closure time of defects such as voids, cracks and particle spacing is too short due to the fast loading speed, which shows that the stress-strain curve is missing on the macro level.

In this paper, we use the analytic methods and the properties of the classical Gauss sums to study the properties of the error term of the fourth power mean of the generalized cubic Gauss sums and give two recurrence formulae for it.

The preferential flow is common in the soil with preferential paths, which affects soil water infiltration greatly. Although previous studies have made a great progress in preferential flow, the effect of preferential paths on preferential flow has not been reported, and a great effort is necessary to understand how precipitation intensities affect preferential flow. Therefore, in this paper, five undisturbed soil columns were sampled at the depth of 0-100 cm with different distribution of preferential paths from the Experimental Station of the Institute of Hydrogeology and Environmental Engineer, Chinese Academy of Geological Science (Hebei, China) and from Luancheng Experimental Station of Chinese Academy of Science (Hebei, China). Tests of different precipitation intensities, i.e., 0.23-0.24, 0.07-0.11, and 0.008-0.042 cm/min, were done to investigate preferential flow of the five soil columns. And the Hydrus-1D software coupling a dual-permeability model was applied to simulate the preferential flow of the soil columns under differential rainfall intensities. The results showed that the preferential paths played a vital role in development of the preferential flow since the levels of preferential flow were higher with more preferential paths in the soils. The relative transport abilities of preferential paths, which were defined by the ratio of velocity of preferential flow to rainfall intensity, increased with heavier rainfall. When the rainfall intensities were larger than the maximal coefficients of hydraulic conductivity of the intact soil columns, the velocities of preferential flow increased remarkably with increase of rainfall intensities. However, when the rainfall intensities were smaller than the maximal coefficients of hydraulic conductivity, the velocities of preferential flow increased little or no change. The effect of rainfall intensities on the ν and increased ranges of ν was related to the development of preferential paths in the intact soil columns, i.e., the effect can be stronger with the higher degree of preferential paths. In the soil columns with better development of preferential paths, the initial times of soil water flowing out at the bottom of the soil columns were shorter when rainfall intensities were larger, while in the soil columns with well developed preferential paths, the initial times of soil water flowing out at the bottom of the soil columns decreased firstly with a higher rainfall intensity, and then increased. The dual-permeability model described preferential flow well but couldn't simulate the process that soil water in the soil matrix flowed out horizontally to preferential paths after the rainfalls. As such the model was not suitable for the soils with plenty of soil fissures. The percentage of preferential flow obtained from the results of modeling was 93.6%-99.9%, which was in agreement with the tested results in undisturbed to disturbed soil. It suggested the model could simulate the preferential flow well. However, the results may be affected by size of columns since the characteristics of preferential flow varied with study scales. Therefore, further studies were needed to improve the understanding of preferential flow in larger scales. The results here will be useful to evaluate the groundwater recharge, water saving methods and movement of soil pollutants in arable land. [ABSTRACT FROM AUTHOR]

Preferential flow is a main type of soil water movement in the structured soil. Although previous researches have made a great progress in preferential flow, how to compare the level of preferential flow based on the dyed pattern of soil profile by dyeing tracers is not reported yet. Therefore, in this paper, the Brilliant Blue FCF (C.I. 42090) dye tracer experiment was designed to investigate and quantify the preferential flow in five intact and five disturbed soil columns sampled at the depth of 0-100 cm from the Experimental Station of the Institute of Hydrogeology and Environmental Engineer, Chinese Academy of Geological Science (Hebei, China) and from Luancheng Experimental Station of Chinese Academy of Science (Hebei, China). Soil water movement patterns of the intact and disturbed soil columns were compared. The results showed that the preferential flow was developed in the intact soil columns, while the piston flow in the disturbed soil columns. The characters of preferential flow in the soil profiles varied along both horizontal and vertical directions. The coefficients of variation (C.V) of the dyed area percentages in the whole profiles of soil columns were proposed to quantify preferential flow in the undisturbed columns and the capacity of soil water movement in the disturbed columns as long as 1) the irrigation conditions were same for all columns; 2) the area of preferential flow was larger than that of uniform flow in intact columns; and 3) the mass-transfer coefficients of soil water flowing horizontally from the preferential path to the matrix were same. Small C.V value represented the high levels of preferential flow in the intact columns. The C.V≥0.5% indicated the low levels of preferential flow, while C.V of >0.25%~<0.5% and ≤0.25% suggested the medium and high levels, respectively. However, the estimated principle may be not suitable for intact soil columns with different kinds of preferential path, i.e., soil cracks and plants' root and earthworm burrows. The preferential levels of the soil columns assessed by the C.V of the dyed area percentages were verified successfully by the irrigation test of undistributed and distributed columns designed to quantify the percentage of preferential flow. However, the results of preferential flow levels estimated by the C.V may be affected by size of columns, because the characters of preferential flow varied with study scales. Therefore, more studies were needed to verify the feasibility of C.V in estimating the preferential flow level. The study here proposed a quantitative method to assess the preferential flow level directly from the dyed pattern of the soil profile, and to evaluate the groundwater recharge, saving water and soil polluting in agriculture. [ABSTRACT FROM AUTHOR]

Slightly acidic electrolyzed water (SAEW) spray has been considered as a novel approach for airborne bacteria reduction in animal housing. This study aimed to optimize the operating parameters of SAEW spray based on the size distribution of sprayed aerosols, the available chlorine travelling loss in sprayed aerosols, and the reduction efficiency of airborne culturable bacteria (CB). The optimized operating parameters were the nozzle orifice diameter and the spray pressure. The size distribution characteristics of sprayed SAEW aerosols under different operating parameters were quantified. The pH and available chlorine concentrations of the original SAEW solution and the SAEW aerosols collected at 0 m, 0.25 m, 0.50 m, 0.75 m, and 1.00 m from the spray nozzle head were analyzed. A bioaerosol nebulizing generator was used to simulate animal housing environment in an environmentally-controlled chamber. Six SAEW spray trials under different operating parameters were conducted at a spray dosage of 80 mL/m2 in the chamber. Airborne CB concentrations before and after spray were measured to investigate the reduction efficiency of airborne CB. Dv(50), the volume-based diameter below which 50% of the particle being present, increased with the nozzle orifice diameter and decreased with the spray pressure. The travelling loss of available chlorine in the sprayed SAEW aerosols was greatly dependent on Dv(50). SAEW spray with medium size sprayed aerosols (Dv(50) = 86.62 μm, 67.94 μm, and 54.53 μm) showed significantly higher airborne CB reduction efficiencies than large (Dv(50)=121.80 μm and 96.00 μm) or small size aerosols (Dv(50) = 42.57 μm). The spray operating parameters that provide medium size sprayed aerosols (Dv(50) ~ 60-90 μm) are recommended for SAEW spray in animal housing. [ABSTRACT FROM AUTHOR]