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Excavations for underground structures, such as working shafts, underground grain silos, and parking garages, are characterized by uniformity, consistent dimensions, large quantities, and strict timelines. Prefabricated recyclable supporting structures (PRSS) are gaining attention over traditional retaining structures due to their standardized design, efficient construction, and reusability, which suit such excavations better. To validate their performance, full-scale tests are conducted to analyze the deformation and stress characteristics of PRSS. The results show that the average maximum lateral displacement of supporting pile is 0.07% of the excavation depth (He), roughly half that of steel plate. Differences in ground surface settlement behind steel plates and the supporting piles are not as significant as those in their lateral displacements. While the displacement of the supporting piles is insufficient to induce soil movement into the active limit state on the non-excavation side, the circular excavation's arching effect reduces the earth pressure on this side of the supporting piles below the active earth pressure limit. Furthermore, the earth pressure acting on the steel plates is lower than that acting on the supporting piles, suggesting the presence of a soil arching effect between two adjacent piles. These findings offer valuable insights for guiding the construction of PRSS. [ABSTRACT FROM AUTHOR]

The present study employs the k-epsilon turbulence model to investigate the influence of stable stratification with different Richardson numbers (Rib) on flow patterns and pollutant dispersion near tall buildings. The results show that thermal stratification significantly affects the flow pattern around buildings. As Rib increases, the leeward stagnation point gradually shifts upward toward the top of the building, while the recirculation region on the top of the building moves downward, and the length of the recirculation region on the windward side initially increases and then decreases. The vortex position gradually moves above the building. The region with high TKE/uH2 is primarily concentrated on the top of the building and within the downwind recirculation area. As Rib increases, the TKE/uH2 decreases in the top and wake regions of the building. With increasing Rib, the ground-level pollutant concentration first increases and then decreases, the height of the downwind plume gradually reduces, while the maximum concentration in the plume rises. [ABSTRACT FROM AUTHOR]

The stable hydrogen and oxygen isotope technique is typically used to explore plant water uptake; however, the accuracy of the technique has been challenged by hydrogen isotope offsets between plant xylem water and its potential source water. In this study, the soil hydrogen and oxygen isotope waterline was used to correct the hydrogen isotope offsets for Salix psammophila and Caragana korshinskii , two typical shrub species on the Chinese Loess Plateau. Five different types of isotopic data [(i) δ18O, (ii) δ2H, (iii) combination δ18O with δ2H, (iv) corrected δ2H and (v) combination δ18O with corrected δ2H] were separately used to determine the water-use patterns of the two shrubs. The δ2H offset values of S. psammophila and C. korshinskii did not show significant temporal variation among the sampling months (May, July and September) but showed notable differences between the two shrubs (−0.4 ± 0.5‰ in S. psammophila vs −4.3 ± 0.9‰ in C. korshinskii). The obtained water absorption proportion (WAP) of S. psammophila in the different soil layers (0–20, 20–60 and 60–200 cm) did not differ significantly among the five different input data types. However, compared with the input data types (iii) and (v), the data types (i), (ii) and (iv) overestimated the WAP of C. korshinskii in the 0–20 cm soil layer and underestimated that in the 60–200 cm layer. The data type (iii) overestimated the WAP of C. korshinskii in 0–20 cm soil layer (25.9 ± 0.8%) in July in comparison with the WAP calculated based on data type (v) (19.1 ± 1.1%). The combination of δ18O and corrected δ2H, i.e. data type (v), was identified as the best data type to determine the water use patterns of C. korshinskii due to the strong correlation between the calculated WAP and soil water content and soil sand content. In general, S. psammophila mainly used (57.9–62.1%) shallow soil water (0–60 cm), whereas C. korshinskii mainly absorbed (52.7–63.5%) deep soil water (60–200 cm). We confirm that the hydrogen isotope offsets can cause significant errors in determining plant water uptake of C. korshinskii , and provide valuable insights for accurately quantifying plant water uptake in the presence of hydrogen isotope offsets between xylem and source water. This study is significant for facilitating the application of the stable hydrogen and oxygen isotope technique worldwide, and for revealing the response mechanism of shrub key ecohydrological and physiological processes to the drought environment in similar climate regions. [ABSTRACT FROM AUTHOR]

The diffusion of chemical grouts in porous media is important for soil reinforcement and stabilization. Slurry diffusion radius and pressure change are important parameters to measure the grouting effect. Using flower tube grouting to make Newtonian fluid slurries diffuse in a column–hemispherical shape is common in engineering, but its diffusion law is still unclear. In terms of the diffusion process, the grout adjacent to the grouting hole first spherically diffuses; with the continuous grouting, it will gradually intersect and overlap and then enter the second diffusion stage, at which the grout will continue to diffuse in a spheroidicity and the slurry in the middle does not spread out vertically anymore. If the stages during grouting are not considered, there will be some errors between the slurry diffusion and the actual situation. Meanwhile, in the traditional study of slurry diffusion law, the tortuous effect of the pore channels and viscosity time denaturation of grout is not considered, resulting in an obvious deviation between the calculated grouting diffusion diameter and the actual value. Therefore, based on the fractal theory, a two-stage column–hemispherical diffusion model of Newtonian fluid was derived considering the tortuosity of porous media and the time-dependent viscosity behavior of slurry. The influences of grouting flow rate, slurry viscosity and pore tortuosity on grouting pressure and diffusion radius under constant flow grouting mode were analyzed. The results show that the grouting flow rate had a positive effect on both of the diffusion radius and the grouting pressure, while the slurry viscosity and porosity tortuosity had a positive effect on the grouting pressure but a negative effect on the diffusion radius. Under the same condition, compared with the traditional column–hemispherical grouting diffusion model, the column–hemispherical grouting diffusion model with two-stage diffusion considering porosity zigzag had a larger diffusion radius and required a lower grouting pressure. The numerical simulation and model test also proved that the calculated diffusion radius and injection pressure from the theoretical model developed in this study were closer to the measured results, with an error of less than 10% in the diffusion radius and less than 20% in the grouting pressure. Therefore, the model may provide a certain reference for grouting design, construction and theoretical research. [ABSTRACT FROM AUTHOR]

The porosity of porous media is a key factor affecting cement slurry diffusion. In this paper, a theoretical model of cement slurry diffusion in porous media considering the variation of porosity is proposed. The model is validated through comparison with the experimental results in the literature. The influence of injection parameters (i.e., the water–cement ratio and the pore fractal dimension) on the porosity and strength of porous media is analyzed. The results indicate that: under the same pore fractal dimension, the porosity of the specimen increases gradually with the increase in diffusion distance, and the rate increases rapidly in the later stage. However, when the fractal dimension of porosity increases to 2.1, the porosity of the consolidated body after grouting does not change with the diffusion distance. The water–cement ratio also affects the porosity of the sample. At a distance below 1.0 m, the sample porosity is larger at a larger water–cement ratio of 1.5. When the distance is more than 1.0 m, the smaller the porosity decreases with increasing water–cement ratios. With the increase in distance, the compressive strength of the specimen first decreases slowly, and then rapidly from 90 kPa to 0 kPa. This is further verified by the pore variation law obtained by SEM. The model is applied to selecting grouting parameter design in road maintenance. The pavement deflection after grouting is effectively reduced, verifying the theoretical model's applicability. [ABSTRACT FROM AUTHOR]

The resistance properties of the interface between polyurethane(PU) grouting materials and rocks subjected to water erosion are the theoretical basis for evaluating the long‐term performance, which, however, is not clear yet. Herein, surface free energy (SFE) theory is used to analyze the mechanism of water damage at the interface between the polyurethane and rock. The surface energy parameters of various PU grouting materials with different densities, limestone, and granite rock materials are tested. The adhesion and peeling work indices are calculated by the SFE theory. The results show that water brings little influence on PU grouting materials. The lower the density of PU is, the better the hydrophobicity is. The increase in the density of PU promotes adhesion between the PU and rock with and without water. Moreover, density increases the difference between SFEs of PU–rock and water–rock, decreasing the detachment tendency of PU over the rocks. Lithology also affects the adhesion of PU and rocks. PU–granite composite exhibits the largest adhesion work and smallest peeling work, which indicates that it has stronger water damage resistance. Finally, the validity of the surface energy theory is proved by mechanical, bond tests and the application. [ABSTRACT FROM AUTHOR]

Isotope geochemistry of precipitation, river water, well water and spring water in the Babao River basin, China, during different seasons showed that regional runoff was dominated by precipitation in summer and autumn and by underground water in winter and spring. The δO and δD values of precipitation and spring water displayed a clear altitude effect. Water from the main stream and tributaries displayed a converse altitude effect in the summer-wet season. The isotopic composition of the various water sources was not well correlated with elevation during the winter-dry season. The spatial distribution of the stable isotope signals of river water demonstrated the influence of rainfall inputs, evaporation and variable flow. An end-member mixing model used for hydrograph separation indicated that in the summer-wet season, the Babao River water was recharged by precipitation (71.9 %), spring water (11.7 %) and well water (16.4 %), whereas the winter-dry season recharge was sourced from spring water (28.2 %) and well water (71.8 %). [ABSTRACT FROM AUTHOR]

orption ability for heavy metals varies among plant species. This study is to evaluate the absorption characteristics of different plant species and planting patterns for heavy metals. Five plant species (tomato, maize, greengrocery, cabbage, and Japan clover herb) were cultivated in monoculture and in intercropping in soil contaminated with heavy metals (Cd, Pb, Cr, Cu, and Fe), to determine the absorption status. Tomato absorbs greater amounts of heavy metals (especially Cd). Furthermore, accumulation of heavy metals increased when tomato was intercropped with other plant species. Maize accumulates greater amounts of Cr, Cu, and Fe. The heavy metal concentrations were reduced when maize was intercropped. Cd and Pb accumulated more in roots of Japan Clover Herb, and the levels of all five heavy metals decreased when intercropped. Tomato intercropping is a feasible method for phytoremediation of heavy metal-contaminated soil, and maize intercropping is feasible for obtaining safe harvest which can be eaten securely. [ABSTRACT FROM AUTHOR]