Hydraulic Action Research Articles

Co-analysis of total suspended particles and discharge reveals the dynamic of mercury input into glacier meltwater runoff in the northern Tibetan Plateau

Climate warming has accelerated glacier melting, releasing legacy pollutants such as mercury (Hg) into aquatic ecosystems. While the relationship between Hg in glacier meltwater runoff, total suspended particles (TSP), and runoff discharges has been established, the underlying inter-relationships and governing factors remain poorly understood. To address this knowledge gap, we conducted a continuous fixed-point sampling at Laohugou No. 12 Glacier in the northern Tibetan Plateau from June to September 2019 spanning the entire glacier ablation season. Our study analyzed the variations of Hg partition in the meltwater runoff and conducted a comprehensive co-analysis of Hg with TSP and discharge to uncover the dominant factors of Hg input into meltwater runoff. The concentration of total Hg (THg) in the meltwater runoff ranged from 0.7 to 112.6 ng/L, with an average concentration of 26.6 ± 25.1 ng/L. Particulate Hg (PHg) was found to be the predominant partition, while dissolved Hg (DHg) exhibited a notable increase in June and September. THg concentration significantly correlated with TSP concentration (r = 0.94, P < 0.01), exceeding the correlation with discharge (r = 0.76, P < 0.01) during the entire ablation period. However, further examination during varying hydrological periods revealed differing associations among Hg speciation concentrations, TSP concentration, and discharge. During the rising limb of the hydrograph, THg (r = 0.86, P < 0.01) and PHg concentrations (r = 0.87, P < 0.01) exhibited a significant correlation with TSP concentration, primarily driven by TSP, implying that Hg availability determines the Hg input into meltwater runoff. Conversely, during the recession limb of the hydrograph, THg concentration was primarily influenced by discharge (r = 0.85, P < 0.01). PHg (r = 0.84, P < 0.01) and TSP (r = 0.97, P < 0.01) concentrations were strongly influenced by discharge, indicating that hydraulic action is the dominant factor affecting Hg input. Our study elucidated the impact of glacier hydrological processes on Hg transport, revealing the dominant factors of Hg input during different hydrological periods. This contributes to a deeper understanding of Hg input into meltwater runoff and improves predictions of Hg export through glacier melt in high mountain regions.

Wmic-GMTS and Wmic-GMERR criteria for micron-scale crack propagation in red-bed soft rocks under hydraulic action

Micron-scale crack propagation in red-bed soft rocks under hydraulic action is a common cause of engineering disasters due to damage to the hard rock–soft rock–water interface. Previous studies have not provided a theoretical analysis of the length, inclination angle, and propagation angle of micron-scale cracks, nor have they established appropriate criteria to describe the crack propagation process. The propagation mechanism of micron-scale cracks in red-bed soft rocks under hydraulic action is not yet fully understood, which makes it challenging to prevent engineering disasters in these types of rocks. To address this issue, we have used the existing generalized maximum tangential stress (GMTS) and generalized maximum energy release rate (GMERR) criteria as the basis and introduced parameters related to micron-scale crack propagation and water action. The GMTS and GMERR criteria for micron-scale crack propagation in red-bed soft rocks under hydraulic action (abbreviated as the Wmic-GMTS and Wmic-GMERR criteria, respectively) were established to evaluate micron-scale crack propagation in red-bed soft rocks under hydraulic action. The influence of the parameters was also described. The process of micron-scale crack propagation under hydraulic action was monitored using uniaxial compression tests (UCTs) based on digital image correlation (DIC) technology. The study analyzed the length, propagation and inclination angles, and mechanical parameters of micron-scale crack propagation to confirm the reliability of the established criteria. The findings suggest that the Wmic-GMTS and Wmic-GMERR criteria are effective in describing the micron-scale crack propagation in red-bed soft rocks under hydraulic action. This study discusses the mechanism of micron-scale crack propagation and its effect on engineering disasters under hydraulic action. It covers topics such as the internal-external weakening of nano-scale particles, lateral propagation of micron-scale cracks, weakening of the mechanical properties of millimeter-scale soft rocks, and resulting interface damage at the engineering scale. The study provides a theoretical basis for the mechanism of disasters in red-bed soft-rock engineering under hydraulic action.

Development of 3D printable stabilized earth-based construction materials using excavated soil: Evaluation of fresh and hardened properties

Soil excavated during construction and demolition can be utilized to reduce the demand for natural sand in 3D printed constructions. This research attempts to systematically develop 3D printable stabilized earth-based materials using excavated soil (clay content of 42.5 %) as 25 % and 50 % replacement of natural sand, and examine their compressive strength, water permeable porosity, and moisture sensitivity. The effectiveness of two binder systems – Ordinary Portland Cement (OPC) and a combination of OPC and ground granulated blast furnace slag (GGBS used to replace 30 % OPC by mass), was investigated. Non-expansive clay in the soil leads to a steeper reduction in apparent viscosity, 12–15 % higher flow retention, and 50–60 % lower plastic viscosity of soil-based mixes, thus contributing to superior extrusion quality at 35–40 mm lower initial flow than OPC-sand and OPC-GGBS-sand mixes. The addition of GGBS, due to its irregular particle morphologies and interlocking effects, further enhances the shape retention of the printed layers by 8–26 % compared to OPC-soil mortars. The structural build-ups in OPC-soil and OPC-GGBS-soil mortars increase with the increase in clay content, which enabled buildability up to a height of 1.2 m compared to only 0.51–0.55 m for OPC-sand and OPC-GGBS-sand mortars. Higher water demand due to the addition of natural clay increases the porosity of 3D printed OPC-soil mortars, thereby lowering compressive strength and increasing moisture sensitivity. However, a blend of OPC and GGBS substantially reduces the moisture sensitivity of the printed mortars at 28-day age, attributed to better stabilization of clay through hydraulic and pozzolanic action of GGBS. 28-day wet compressive strength of 14–25 MPa is obtained for the printed soil-based mixes depending on the soil dosage and loading direction. In summary, the study provides a feasible solution for the 3D printing of stabilized earth structures with lower demand for natural sand and OPC.

Simulation Study and Engineering Application of Weakening Mine Pressure Behavior in Stope through Ground Fracturing Thick and Hard Rock Strata

Fracturing hard roofs by ground hydraulic action is an important control technology for the strong mine pressure in the stope. In this paper, a new simulation method, “separate + interface,” is proposed, and two physical simulation experiments are conducted; the phenomenon of increased goaf pressure and decreased front abutment pressure is discovered after fracturing in the key strata, and then the influence of different fractured crack shapes on the front abutment pressure and the goaf stress is revealed. The results are as follows: Firstly, the separation under the high-level hard strata blocks the transmission of overburden load to the goaf, leading to the high-stress concentration of the coal seam, which is the main reason for the large deformation of roadways and the breakage of a single hydraulic prop in the roadway. Secondly, the weakening effect of mine pressure differs when hard rock strata are fractured artificially with different types of cracks. The peak value of abutment pressure is reduced from 24.91 to 20.60 MPa, 17.80 MPa, and 16.13 MPa with the vertical crack spacing of 20 m, 15 m, and 10 m, respectively, and the related goaf pressure is increased from 2.61 to 3.54 MPa, 3.91 MPa, and 4.34 MPa, respectively. The peak value of abutment pressure decreased from 24.79 to 22.08 MPa, 19.88 MPa, and 17.73 MPa. The related goaf pressure increased from 2.61 to 3.39 MPa, 3.81 MPa, and 4.43 MPa, respectively, with the key strata also fractured into two horizontal layers, three horizontal layers, and four horizontal layers with horizontal fractures. Thirdly, after the hard roof is fractured above the No. 8202 working face, the first breaking step distance of the main roof decreased from 112.6 to 90.32 cm, while the first breaking step distances of KS2 and KS3 decreased from 106.3 and 135.8 cm to 93.5 cm and 104.8 cm, respectively, and the goaf pressure also increased. Compared to the adjacent unfractured No. 8203 working face, the mine pressure intensity of the No. 8202 working face is significantly reduced. The research results can provide useful guidance for the treatment of strong mine pressure.

Study on the Influence of Gas Desorption Characteristics of Different Coal Bodies under Hydraulic Permeability Enhancement

To investigate the influence of hydraulic permeability enhancement on the gas desorption and accumulation characteristics of water-bearing coal bodies and deeply implement hydraulic fracturing measures to prevent and control gas disasters in coal seams, isothermal adsorption/desorption tests, low-pressure CO2 adsorption tests, and X-ray diffraction (XRD) tests were performed on anthracite from Anbao Coal Mine in Guizhou and bituminous coal from Huainan Pan’er Coal Mine. The study results showed that the gas desorption by kinds of water-bearing coal samples (anthracite) and bituminous coal (PE) was evidently promoted by stress. After each stress path, differences were observed between coal samples in gas desorption, which, however, presented similar variation trends. The gas desorption of the AB coal samples was greater than that of PE coal samples, and the increment of the limiting gas desorption by the AB coal samples was greater than that by the PE coal samples. The specific surface area of the AB coal samples was larger than that of the PE coal samples, and they both contained hydrophilic minerals and moisture. It was found through field observation that after hydraulic permeability enhancement acted upon water-bearing coal, the desorbed gas passively migrated under the stress action. When the coal body was free from the hydraulic stress action, gas started flowing back. The study results reveal the influence of hydraulic permeability enhancement on the accumulated gas desorption characteristics of water-bearing coal, and will be of theoretical and practical engineering significance for the prevention and control of gas disasters in coal seams using hydraulic measures.

Study on unit energy damage and prediction model of concrete under hydraulic impact

Based on the SPH-FEM (Smoothed Particle Hydrodynamics – Finite Element Method) coupling method, the hydraulic impact concrete model was established, and the numerical model was verified by hydraulic impact concrete experiments and CT (Computed Tomography) scanning experiments. Secondly, this paper proposes the comprehensive damage factor of unit energy consumption, and explores the damage law of unit energy consumption of concrete under different parameters and optimizes the hydraulic parameters by using image processing techniques. Finally, this paper analyzes the crushing process of concrete under hydraulic impact, and predicts the unit energy consumption comprehensive damage by the multiple linear regression model, the decision tree model and the GBDT (Gradient Boosting Decision Tree) model. The results show that the effects of different parameters on the comprehensive damage of unit energy consumption of hydraulic impact concrete changes in stages, and the concrete particles will completely fail when the concrete damage under hydraulic action accumulates to a certain degree and the von mises stress reaches a certain peak. Secondly, the prediction of the GBDT model is the best, and the study provides a theoretical basis and technical reference for the efficient and economic utilization of hydraulic impact concrete technology.

Enhanced delivery of remedial reagents in low-permeability aquifers through coupling with groundwater circulation well

Limited dispersion and mass transfer because of hydrogeological heterogeneity make it difficult to deliver remedial reagents to desired locations. Remediation alternatives that overcome mass transfer limitations are required urgently to improve the efficiency of in situ remediation techniques. In this study, a combination of two-dimensional sandbox experiments and numerical simulations was used to explore the migration process of remedial reagents driven by groundwater circulating well (GCW). The influences of the circulating flow rate, concentration of the remedial reagent (H2O2 as a model) and cycle operation mode on the migration of GCW enhanced remedial reagents were investigated. The flow rate of the pumped water can enhance the concentration gradient at the interface of different permeation zones. The redistribution of reagents by increased Fick diffusion significantly increased the dispersion range. The results of parametric sensitivity analysis showed that the aggregation effect of remedial reagents in the low permeability area (∼10-7 m/s) and related to the injection site. Considering remedial reagents attenuation, a reactive transport model can better simulate the concentration changes in low-permeability regions (R2 > 0.960). The numerical simulation results showed that the principal component of the hydrodynamic field was tangential to the main axis of the target area. The diffusion coefficient of the low-permeability region was one order of magnitude lower than that of the high-permeability region (∼10-3 m/s). Thus, the low-permeability region was less affected by the hydraulic action of the GCW and had a longer retention time for remedial reagents. Specific aquifer parameters and operating modes are key engineering design factors of a GCW that should be considered in conjunction with other in situ chemical technologies. This study provides some new insights for in situ remediation of contanminated aquifers with a GCW, and suggests that (i) the hydraulic circulation driven by GCW can promote the accumulation of injected remedial agents in low permeability areas, especially injection point is located near wellbore; and (ii) residence time of reagents in contaminated areas should be comprehensively considered when chemical remediation technology is coupled with GCW. The results of this study can be used to improve the delivery efficiency of remedial reagents in contaminated aquifers.

METHOD OF OBTAINING WATER-COAL SUSPENSION AND HEAT AND MASS EXCHANGE EQUIPMENT FOR ITS APPLICATION

The analysis of methods and equipment for obtaining water-coal suspensions was carried out. The purpose of the research is to improve the quality of the resulting suspension due to more effective grinding and increasing the amount of its solid component. Heat and mass exchange equipment has been developed, with the help of which it is possible to achieve an increase in the efficiency of hydraulic impact due to an increase in the frequency of pulsations when obtaining water-coal suspensions. The use of water-coal suspensions as an energy fuel makes it possible to improve the technical, economic and environmental performance of power plants. Thus, during the conversion of the boiler to water-coal fuel, it was possible to increase the thermal power of the boiler from 13,2 to 21,1 MW when replacing 70 % of coal with water-coal fuel. Currently, there are different methods and equipment for the preparation of water-coal suspension. However, they all have certain drawbacks. The main disadvantages of the method of obtaining water-coal suspensions are multi-stage, metal consumption, difficulty of installation and start-up, high energy costs, and the resulting suspension is of insufficiently high quality. Also, the disadvantages are the limited frequency of hydraulic shock pulses during processing in one cycle, which is insufficient for the preparation of highly concentrated suspensions that meet the requirements for liquid composite fuel intended for direct combustion. In order to improve the quality of the resulting suspension due to more effective grinding and increasing the amount of its solid component, heat and mass exchange equipment was developed, with the help of which it is possible to achieve an increase in the efficiency of the hydraulic impact action due to an increase in the frequency of pulsations during the production of water-coal suspensions. As heat and mass exchange equipment, rotary pulsation devices (RPD) operating according to the method of discrete-pulse energy input (DPEI) were used. The DPEI method involves the creation of a large number of working bodies or working elements evenly distributed in the water, which transform stationary thermal, mechanical or other types of energy into energetically powerful pulses, discrete in time and space.

Experimental study on influence of pressure fluctuation and cavitation characteristics of nozzle internal flow on near field spray

To investigate the causal relationship between the multi-frequency pressure fluctuations and the characteristics of the cavitation in the nozzle, as well as the influence mechanism on the near-field spray, a high-speed microscopic imaging technique was used to carry out the visualization experiment of the real-size tapered hole nozzle under different common rail pressures. The research show that the fluctuation trends such as pressure drop, fluctuation duration as well as coupling characteristics of high and low frequency can reflect the injection quantity, effective injection duration and cavitation morphology in the nozzle to some extent. The hydraulic servo action under different injection pressures affects the needle valve displacement, which in turn affects the throttling position and cavitation morphology during the injection process. After cavitation occurs, the pressure wave velocity and pressure wave transmission frequency in the pipe are obviously changed by affecting the bulk elastic modulus of the gas-mixed liquid. When geometry-induced cavitation occurs, the pressure fluctuates at low frequency, and the whole is relatively smooth. When string cavitation occurs, high-frequency pressure fluctuations tend to occur. The maximum lift and effective duration of needle valve determine the overall trend of pressure fluctuations, and cavitation characteristics affect the frequency characteristics and propagation speed of pressure fluctuations. The research provides theoretical support for the prediction method of fuel flow and cavitation characteristics in high-pressure nozzle based on high-low frequency identification of pressure fluctuations.

Vegetation affects gully headcut erosion processes by regulating runoff hydrodynamics in the Loess tableland region

Vegetation plays an important role in gully headcut erosion processes. However, it is still unclear how vegetation in the upstream area affects gully headcut erosion processes by changing the hydraulics. A series of in situ inflow scouring experiments were conducted on bare land plots and vegetation plots (including the upstream area, headwall, and gully bed) planted with Bothriochloa ischaemum (BI), Agropyron cristatum (AC), and Medicago sativa (MS) with clustered stems and Artemisia gmelinii (AG) with erect stems to investigate the influence of vegetation on the hydrodynamic parameters involved in gully headcut erosion processes. The results showed that, compared with bare land, vegetation increased the Manning roughness coefficient (n) and Darcy–Weisbach friction factor (f) in the upstream area by 0.2–2.5 times and 0.9–9.6 times, respectively, but reduced the runoff velocity in the upstream area and gully brink. However, the jet flow velocity at entry into the plunge pool increased rapidly after passing through the gully head. The influence of vegetation with clustered stems on roughness and runoff velocity was greater than that of vegetation with branched stems. At 3.6 m3/h inflow discharge, vegetation can increase the runoff shear stress of the upstream area. The energy consumption of the gully head, upstream area, and gully bed accounted for 74 to 76 %, 19 to 21 %, and 4 to 7 % of the total energy consumption, respectively. The four vegetation treatments reduced the gully headcut soil loss by 31 to 81 %, among which MS exhibited the highest reduction. The soil loss rate was positively correlated with the jet flow velocity and its kinetic energy, and the correlation was the best (R2 of 0.934 and 0.935, respectively, P < 0.01), presenting a logarithmic trend. These results are helpful to deepen the understanding of the roles of vegetation in regulating runoff hydraulic action during gully headcut erosion.

Channel instability and hydrogeomorphic adjustment in alluvial reach of Kangsabati River, India using Digital Shoreline Analysis System and Acoustic Doppler Current Profiler

Despite the stable stratigraphic setup in plateau basin, several anthropogenic interventions triggered geomorphic sensitivity by hydrodynamic metamorphosis. Present research focussed to evaluate the hydrogeomorphic evolution for anthropogenic interventions in Kangsabati River as measured by channel migration rate (CMR), bankline shifting, and erosion-accretion of last thirty years (1990–2020) in 454 mouza using Digital shoreline analysis system (DSAS). Acoustic Doppler Current Profiler (ADCP) was used to directly estimate bank scouring or erosion measuring of hydraulic variables during bankfull discharge across the DSAS transects. DSAS denoted that decaying CMR (64–46 km) decreased accretion area (4.08–1.44 km2) but increased erosion area (2.12–2.44 km2). ADCP revealed that sand mining induced super-critical flow, bridge and embankment generated maximum boundary shear, and mining bed slope increased hydraulic action for channel widening and bank erosion especially middle and lower segments. This study has provided information about channel instability, and bank erosion hazard planning and management.

Research on stability of steep bank slope and reserved thin-walled rock cofferdam during excavation of intake foundation pit

The intake of water diversion project is generally located on the bank slope above the large reservoir or deep water area of a river. Due to the influence of water level change and hydraulic action, the rock mass of bank slope is seriously weathered and broken, leading that the rock mass has low strength and is easy to collapse or landslide. In this paper, the water intake engineering of the long-distance diversion project in central Shanxi Province is selected as the research object. The multi-point displacement meter is used to monitor the slope deformation after anchorage and concrete retaining wall support. Based on the FLAC3D V6.0 software, the numerical simulation of the excavation process of the steep reinforced river bank slope is carried out, and the long-term deformation of the slope is predicted. The excavation scheme of retaining outer thin-walled rock wall as water cofferdam is proposed. The excavation process of foundation pit, which is supported with concrete-filled steel tubular pile reinforcing cofferdam and concrete supporting beam, is simulated. It is found that the upper part of the steep slope supported by anchor cable and concrete retaining wall is stable, and the large deformation and plastic failure of the water-retaining thin rock wall are mainly affected by the disturbance of foundation pit excavation. The concrete-filled steel tubular pile support avoids the collapse of the reserved thin-walled cofferdam, and the horizontal beam in the foundation pit improves the stress state of the external wall of the foundation pit. The research results of this paper reveal the evolution mechanism of rock mass deformation and failure during excavation of foundation pit on steep bank slope, and provide guidance for excavation and support of foundation pit for similar bank slope.

Chemistry and mineralogy of Zr- and Ti-rich minerals sourced from Cox’s Bazar beach placer deposits, Bangladesh: Implication of resources processing and evaluation

Zircon is always found in association with Ti-rich minerals; therefore, it is produced mainly as a co-product in the production of ilmenite and rutile from placer mining operations. In Cox’s Bazar beach sands, they contain at 2.8, 12.1 and 2.7 wt% (average) respectively in the heavies. In order to scrutinize mineralogical and geochemical variability among Zr- and Ti- rich minerals, XRF, XRD, SEM and EPMA were implemented. Petrogenesis manifests the nature of impurities in mineral concentrates where they included through cationic substitution during alteration and metamictization, whereas their coating and pore filling occurred by hydraulic action in fluvial process. The impurities of oxides, silicates and phosphates gangue mineral phases degrade the quality of zircon concentrate (ZrO2 + HfO2 = 63.73 wt%) in achieving premium grade. Although the process of hot acid leaching (HAL) upgrades the quality enhancing ZrO2 + HfO2 (69.10 wt%) content, yet to be eliminated Fe and U to reach premium grade. Thermal annealing and calcining treatment is suggested to fully recover the zircon prior to industrial use. Similar to zircon, ilmenite and rutile they both contain trace levels of gangue mineral phases. The content of TiO2 and Ti/(Ti + Fe) (48.1 wt% and 0.5 respectively) indicates unaltered ilmenite. Therefore, upgrading the unaltered low grade ilmenite concentrate to chlorination feedstock, ilmenite smelting and the synthetic rutile routes are suggested. In addition, the TiO2 (83.84 wt%) content in the bulk rutile concentrate shows as much as the high grade ilmenite display due to contaminants. Mentioning, two of the major impurities such as tin and zirconium occurred as mineral grain cassiterite and zircon and as substitutions for titanium (Ti ⇌ Sn, Zr) in crystal lattice. The way of acid leaching can be instrumental not only for upgrading rutile but also for extracting Sn and Zr as byproduct of Ti metal/ TiO2 pigment.

Microplastic abundance, characteristics and removal in large-scale multi-stage constructed wetlands for effluent polishing in northern China

Wastewater treatment plants (WWTPs) are considered to be an important source of microplastics (MPs) to the aquatic environment. Multi-stage constructed wetlands (CWs) are widely used for the advanced treatment of effluent from the WWTPs. Research on the abundance, characteristics, and removal of MPs in multi-stage CWs is limited. Therefore, we studied two large-scale multi-stage CW systems (Lingang Ecological Wetland Park and Konggang CW system) in Tianjin, China. The removal efficiency of MPs in two CW systems was greater than 89.0% (from 8.4 to 28.9 particles L−1 in the influent to 0.2–0.9 particles L−1 in the effluent). During the treatment, the horizontal subsurface flow CWs (HSSFCWs) in Lingang Ecological Wetland Park and the integrated vertical flow CWs (VFCWs) in Konggang CW system removed 82.8%-88.9% of MPs. 27.3%-60.0% of MPs were removed by surface flow constructed wetland (SFCW) in two CW systems. Among detected MPs, five types of polymers were identified by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR), including polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP), polyethylene terephthalate (PET), and polyethylene (PE). The characteristics of MPs, such as sizes, shapes, and types influenced the removal of MPs in various treatment processes in two CW systems. Specifically, microfibers could be intertwined to form coils by hydraulic action, and effectively removed by HSSFCWs. Results of the present study indicated that large-scale multi-stage CW systems could substantially reduce the MP pollution discharged from WWTPs into the aquatic environments, and provided a theoretical basis for understanding the migration and distribution of MPs in the aquatic environment.

ЗАБЕЗПЕЧЕННЯ КАРБОНІЗАЦІЙНОЇ СТІЙКОСТІ ГАЗОБЕТОНУ АВТОКЛАВНОГО ТВЕРДНЕННЯ

The analysis of tendencies of production of autoclaved aerated concrete is resulted. Given the price factor, energy and environmental status of the industry of construction wall and insulation materials, autoclaved aerated concrete has significant advantages over traditional wall materials and prospects for production. Studies of the durability of autoclaved aerated concrete are due to the increase in its production and use in the construction industry in recent years due to rising energy costs and the need to reduce greenhouse gas emissions. At the same time, the density of aerated concrete decreased almost 2 times. The transition to the production of low-density autoclaved aerated concrete D300, D150 on the one hand improves the thermophysical characteristics of aerated concrete, reduces material consumption, on the other - increases the specific cost of binder (cement) per unit mass of aerated concrete and increases its vapor and air permeability. High vapor permeability and adsorption properties of water vapor and gases from the air pose a potential threat due to possible carbonization of aerated concrete, "loosening" of the macrostructure of the material during wetting and drying, irreversible deformation during freezing and thawing of wet aerated concrete, which occur almost simultaneously. Under the conditions of soaking, capillary suction of water and adsorption of water vapor, the processes of carbonization of autoclaved aerated concrete are accelerated. The material can adsorb moisture and carbon dioxide from the air. The formation of carbon dioxide in aerated concrete reduces the alkaline environment, neutralizes free lime and the destruction of calcium hydrosilicates and corrosion of reinforced products. Carbonization can have both positive and negative effects on cement concrete. To ensure the carbonization stability of autoclaved aerated concrete should be achieved by implementing a number of technological solutions that increase the carbonization resistance of autoclaved aerated concrete while reducing the clinker component in the mineral binder. The results of the use of natural mineral additives of hydraulic and pozzolanic action in the composition of autoclaved aerated concrete are given.

Empirical Formulas to Predict the Maximum Scour Depth With Debris Accumulation Around A Single Cylindrical Bridge Pier: An Experimental Study

The probability of debris accumulation near bridge piers during the heavy storm and river flood convert the ‎hydraulic action of flow and increase the scour depth due to the reduction of flow area and the increase in ‎velocity of flow. In this paper, the effects of debris accumulation length, width and submerged depth on ‎scour depth near bridge pier were investigated. An experimental study for three groups of woody debris ‎accumulation was conducted under clear water condition to investigate the effects on maximum scour depth. ‎The results showed that the increase of blocked area of debris ‎to 27% increases the scour depth by approximately 140%. Furthermore, two empirical exponential formulas was proposed to predict the effect of ‎debris on the maximum scour depth and the modification factor required for single pier. Well agreement ‎was obtained for both derived formulas with coefficient of determination (R2) of 0.96. ‎

Biological Zonation and Bedrock Strength on a High Energy Granite Shore Platform

Burningham, H. and Knight, J. 2020. Biological zonation and bedrock strength on a high energy granite shore platform. In: Malvarez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 23-28. Coconut Creek (Florida), ISSN 0749-0208.Many studies have shown that downwearing of rock shore platforms results from interactions between biological and geomorphological processes, but the relative roles of biological, lithological and external (wave hydraulic action) in shaping rock shore platforms have not been examined in detail. This is important, however, because surface organisms can both increase and decrease rates of platform downwearing by biological weathering and bioprotection, respectively. This study presents biological and geomorphological results from a high energy shoreline in northwest Ireland. Here, the 50-100 m wide granite shore platform has a slope of ∼1:6 and extends from 7-9 m above the level of mean high water springs to ∼2 m below mean low water. Organisms attached to the bedrock surface were surveyed by the quadrat method along two shore-normal topographic transects. At each quadrat site, bedrock hardness was measured using an Equotip instrument. Results show clear ecological zonation that can be directly related to the tidal frame. There is very little evidence for cross-shore changes in bedrock hardness. Elevation is the most significant driving factor for the presence of different species, but bedrock hardness is only associated with the abundance of specific species such as barnacles, demonstrating complexity in biogeomorphological relationships at local scales.

Acceptance of BANCS model for predicting stream bank erosion potential and rate in the left bank of Ganga river of Diara region in Malda district, North East India

River bank erosion is a hazardous problem of Malda district. Different parts of Malda are mainly eroded by hydraulic action of River Ganga. Bank assessment for non-point source consequences of sediment model is a well accepted process for predicting stream bank erosion hazard potential. In the present study, river bank stability condition has been measured form field survey on 15 sample segments for 185 km stretched from Rajmahal in Sahibganj district, Jharkhand to upstream of Farakka barrage in Malda. In the present study, bank erosion hazard index (BEHI), near bank stress (NBS) and field based data have been considered for assessing stream bank erosion. The result shows that BEHI is high along the whole given left bank line extension of river Ganga, among these BEHI is very high in the upper segments of the river and adjacent river bank line extension of Farakka barrage, overall NBS conditions along left river bank line are less compare to the BEHI. Dominant NBS conditions are belong under moderate to low along the river bank line. Loosely compact alluvial soil, sparse vegetation, steep slope, unorganized agricultural activities; sinuous channel can be responsible for river bank erosion hazard potentiality. On an average 976,068.991 metric tons of sediments entrains to the river in a year. Bank has experienced variants bank erosion from same BEHI and NBS combinations. So, it can be concluded that BEHI and NBS are potentially not significant model for predicting bank erosion in present study.

Technical solutions of vibration safety cold riveting performed ship repair

The parameters of heating and cooling of rivets made of steel and aluminum alloy, as well as data of fi lling holes with these rivets during hot and cold riveting are compared. The features of the process of performing cold impact riveting by direct and reverse methods, as well as the possibility of reducing the force of this riveting by improving the closing heads and constructive transformation of the rivets themselves are considered. Features of physiological infl uence of cold shock riveting on hands, elbows and shoulders of workers are determined. Describes the construction of riveting hammers and supports with spring shock absorbers that prevent the disease of workers vibration disease, portable riveting presses of pneumatic and hydraulic action. A description of the press equipment and technology of bolt-riveting connections, allowing mechanizing the process of cold riveting is given.

ВЗАЄМОДІЯ ДРЕНАЖНИХ СВЕРДЛОВИН У ПРОТИФІЛЬТРАЦІЙНИХ ЗАВІСАХ

The decrease of water levels in the drainage wells of the coastal anti-filtration drainage system with the siphon method of water intake from them was analyzed. The interaction of water-lowering wells with different depths and located at variable distances from each other is considered, which makes it possible to ensure uniform drainage from each well and to achieve a steady decrease in the level of groundwater over the entire length of the antifiltration drainage system.The results of the performed analytical studies are presented. The example of the Kamyanka-Dniprovska's anti-filtration drainage system shows that the decrease in water levels in wells at the same flow rate of pumped water depends on their hydraulic interaction, hydrogeological conditions of water filtration from the aquifer and the distance of the antifiltration drainage system from the bank-side. The results obtained indicate that the highest level of water depletion of the coastal vertical anti-filtration drainage system line with siphon drainage from wells is achieved at a distance of a number of wells from the Kakhovsky reservoir bank-side a = 100 m, at the same water flow rate from each of the drainage wells (Q = 604,8 m3 /day), located at different distances from each other. The highest rate of additional reduction of water obtained through mutual hydraulic action was obtained in the 7th well, which has a depth of 14,9 m, and it is located at a distance of 100 m from the 6th well and at a distance of 110 m from the 8th well. The lowest indicator of the level of groundwater reductions at different indicators of the distance of a number of drainage wells to the bank-side a (30, 50, 80, 100 m) is observed in the first well, farthest from the water collection well.