Abstract:The surface water Subei Plain was polluted eriously, and the deep confined groundwater becomes the main exploitation aquifer, but high-water levels areas still exist after the extensive groundwater extraction. In order to investigate the cause of this phenomenon, the hydrogen and oxygen isotopes as well as water chemistry of river water and groundwater in Lianyungang,Huaian, Yangzhou, Taizhou and Yancheng were sampled and analyzed. The results showed that the hydrogen and oxygen isotopes of confined water in the Subei Plain are depleted relative to the surface water and the shallow groundwater, rather than from local infiltration of precipitation and recharge of the upper aquifer by transgressive flow. The recharge source is characterized by the obvious isotope depletion. Tritium dating data indicates that the groundwater receives modern precipitation recharge and apparent tritium from nuclear testing has been detected in the confined water. The large amount of metasilicic acid in the deep groundwater indicates that the groundwater water-rock reaction is dominated by the silicate reaction. Because multiple volcanic eruptions have occurred since the Pliocene in the northern Jiangsu area, the area of occult basalt beneath the Quaternary strata may be the main aquifer where deep groundwater reacted with water-rock to produce the metasilicic acid, and these metasilicic acid-rich groundwater then transported through the faults to the Quaternary confined aquifer.

Abstract:In order to deeply understand the chemical evolution of groundwater and scientifically guide the groundwater resource management in the alpine region, this study took the Golmud River Watershed as the typical alpine watershed, investigated the groundwater chemistry and explored the influencing factors in 2019. Meanwhile, the groundwater quality in the snowmelt, wet season and dry season was evaluated using the entropy water quality index, Durov diagram and sodium sorption ratio, and potential risks posed by nitrate and fluoride in the groundwater to human health were assessed using the mathematical model of health risk assessment. Hydro chemical results showed that chemical type of groundwater had little change with periods but varied greatly in space: HCO^-₃ type for phreatic groundwater in the mountain area, Cl^- type for phreatic groundwater in the plain area and HCO^-₃ type for confined groundwater in the plain area. The high ion concentrations of groundwater occurred mainly in the overflow zone of plain. Phreatic groundwater chemistry was mainly affected by the fertilizer use of spring tillage during the snowmelt season, by the industrial wastewater and domestic sewage discharge during the dry season, and by the water-rock interaction during the wet season. The results of water quality assessment indicated that shallow groundwater was not mostly suitable for irrigation in the watershed, and some was not suitable for drinking in the plain. The health risk evaluation found that the non-carcinogenic risk of fluoride was greater than that of nitrate to human health, and has already endangered children, and the non-carcinogenic risks of fluoride and nitrate were severer to human health during the dry period than other periods. Therefore, it is currently urgent to reduce the anthropogenic input such as domestic sewage, industrial discharge and agricultural discharge to protect the groundwater quality in the watershed.

Abstract:In order to improve the refined management and planning of the Yangtze River shoreline, the definition method for the shoreline protection scope of the lower reaches of the Yangtze River is preliminary explored in this paper. Referring to the Yangtze River Protection Law as well as the relevant literatures, standards and regulations, a defining and planning method for the shoreline protection scope of the lower reaches of the Yangtze River is proposed. In this method, both the shoreline administration scope for hydrological departments and a “shoreline-riparian zone-buffer zone” based protection scope are considered comprehensively. For the riparian zone and buffer zone, they can be obtained in consideration with ecology and hydrological functions of shorelines and utilization modes of hinterland areas. Based on the Yangtze River coastline in the Yangzhou section, the application analysis of the proposed definition method indicates that this method has a good correlation with the current shoreline management methods and shows good operability. The proposed methods can provide a support for the formulation of the shoreline protection plan for the lower reaches of the Yangtze River.

Abstract:In order to improve the applicability of Grid-Xin’anjiang model (Grid-XAJ)in flood simulation and forecasting of the semi-arid and semi-humid areas, the dominant runoff generation mechanism of the basin grid in the process of runoff generation was dynamically identified by determining the relationship between rainfall and soil moisture in this study. The Grid-Xin’anjiang and saturation-infiltration double excess distributed model (Grid-XAJ-SIDE)was constructed based on the dynamic combination of saturation-excess and infiltration-excess runoff. The semi-arid Suide Watershed was selected for comparing the simulation results of the Grid-XAJ-SIDE, the Grid-XAJ and the Grid-GA models. The results show that the qualified rate of runoff simulation of the three models in the Suide watershed are all above 80.0%. Compared with the Grid-XAJ (53.0%)and Grid-GA (40.0%)models, the Grid-XAJ-SIDE (66.7%)model has a higher qualified rate for the flood peak simulation. Meanwhile, the Grid-XAJ-SIDE model can capture the control effects of rainfall and soil water content on the spatio-temporal distribution of runoff generation.

Abstract:The segmental Muskingum method,the Muskingum-Cunge (MC) algorithm with variable parameters and the Muskingum-Cunge-Todini (MCT) variable parameter method which reflecting the shape and hydraulic characteristics of the river cross-section were respectively used to study channel flow confluence for the Yuanling station-Wangjiahe station section inYuanshui Basin. The application effect of the routing method with distributed parameters in real river channel is discussed. The results show that the segmental Muskingum method,MC algorithm and MCT variable parameter method can all simulate pushing and tampering of flood in the river channel with high simulation accuracy,and the deterministic coefficients of MC algorithm and MCT variable parameter method are more accurate and stable than segmental Muskingum method. The MC algorithm and MCT variable parameter method improve the parameter characteristics of segmental Muskingum method well,and the MCT variable parameter method solves the problem of the inconsistency between the storage capacity and the steady state of MC algorithm. On the whole,the three methods have strong adaptability and reliability for flood frocast,and provide a new method for real-time flood forecast.

Abstract:Considering that satellite retrieved soil moisture (SRSM) products have relatively coarser spatiotemporal resolutions and, therefore, cannot meet the demand of flood forecasting in small and medium-sized watersheds, this study takes the Qinhuai River Basin as the research area to develope a method to merge three SRSM products and further downscale it to a finer resolution. The merged product was obtained based on three SRSM products, i.e., the SMOS, SMAP and AMSR2 products, via an assembling average method. The downscaling procedure was implemented to obtain the fine-scale soil moisture based on the relationship of topographic wetness index and soil moisture. The results showed that the RMSE of merged product is lower than that of original SRSM product. Besides, the merged product is close to the observations regarding both daily and seasonal average values. The method proposed in this paper can overcome the disadvantages of a single SRSM product, such as large time interval and lower precision, with a potential of worldwide applicability.

Abstract:In order to illustrate the structural adaptability, precision and accuracy of different PM correction models in wheat fields of Yongnian District of Handan City, the field evapotranspiration during key growth stages (from April to May) of winter wheat was simulated respectively through PM-1, PM-2 and PM-3, and simulation results were compared with the water balance results. The results show that the simulated evapotranspiration precision of PM-1 is the highest, of which the corresponding R 2 and GPI values are 0.773 and 3.105 respectively; the precision of PM-3 is the lowest, of which the corresponding R 2 and GPI are 0.701 and -2.904 respectively. The temporal distribution equilibrium of PM-1 simulated evapotranspiration is the best and that of PM-2 is the worst. These PM correction models have their own advantages and limitations, and PM-1 is more suitable for the evapotranspiration simulation of Yongnian District. The results can supply reference to the disclosure of wheat-fields evapotranspiration law in key growth stages and provide basis for the inversion and revision of remote sensing evapotranspiration in large scale.

Abstract:In order to study the response characteristics of surface current to the changing wind field and the effect of wind field and surface current on the cyanobacteria migration in the Lake Taihu, systematic field observation was carried out. In this study, the surface current was observed by the GPS particle tracers, while the characteristics of surface current and the accumulation process of cyanobacteria blooms in the Lake Taihu under varying wind condition were analyzed by combining the variation characteristics of wind field and remote sensing map. The results show that the wind is the main driving force of surface current in the Lake Taihu. However, due to the influence of topographic characteristics, shoreline characteristics and et al, the response of surface current to the wind field in different water areas is not completely consistent. The surface currents of the Lake Taihu under the influence of wind field have wide spatial differences, which is the dominant factor leading to different concentrations of cyanobacteria in different areas during the migration process, and this phenomenon is one of the important reasons for the regional cyanobacteria bloom. The process of wind field, surface current and cyanobacteria migration and aggregation are a response system of successive conduction. The current field under the influence of suitable wind field is an important external factor to promote the large area of cyanobacteria blooms in a short time.

Abstract:Submerged plants, such as the Hydrilla verticillata, Vallisneria natans , Elodea nuttallii and Potamogeton crispus L , were selected as the research objects. This study used the scanning electron microscopy, fluorescence microscopy and 16S rRNA high-throughput sequencing technology to explore the bacterial community structure and influencing factors attached to the leaf surface of submerged plants in different habitats. The results show that the composition of algae attached to the leaf surface of submerged plants is significantly different from that in the environmental water body. Different submerged plants have different density of microorganisms on the leaf surface, and the density of microorganisms attached to the surface of lake samples are lower than the river samples. α-Proteobacteria, β-Proteobacteria and γ-Proteobacteria are the main bacterial classes in the biofilm on the leaves of submerged plants. These classes have the function of degrading pollutants and purifying water bodies. Redundant analysis shows that the concentration of nutrients in the water body has a great influence on the microbial community structure on the leaf surface of submerged plants.

Abstract:In this study, the ciprofloxacin (CFC) and copper (Cu) were selected as the target pollutants, indoor culture experiments were designed, and the interaction relationship between microbial communities and antibiotic resistance genes (ARGs)under ciprofloxacin and copper co-contamination in river sediments was explored using high throughput 16S rRNA sequencing and quantitative PCR. The results showed that the ARGs abundance, microbial community composition and functions were significantly different among different experimental groups (CFC contamination, Cu contamination and co-contamination). The total relative abundance of ARGs of each sample showed an increasing trend first, and then it decreased at the end of culture experiment. Co-occurrence network analysis suggested that intI 1 was associated with 3 types of ARGs and 8 bacterial communities, regarded as a bridge between ARGs and microbial community. Meanwhile, the bacteria that belonged to Proteobacteria, Acidobacteria, Firmicutes, Bacteroidetes and Chloroflexi was considered as the potential ARGs hosts in the aquatic environment. Based on the partial redundancy analysis, the microbial community had the highest overall interpretation rate (49.77%) for the change of ARGs abundance among MGEs, microbial communities, pollutants and other factors. At last, the path analysis showed that CFC and Cu pollutants indirectly affect the spread and diffusion of ARGs mainly through microbial communities.

Abstract:The stress state and the variation law of velocity in the falling process of rock breaking hammer are studied according to the immersed tunnel foundation trench in the Shenzhen-Zhongshan passage project. The FEM method is used to simulate the process of rock drilling, study the damage development characteristics of rock and analyze the influence law of water depth, impact velocity and drilling times on the rock failure and damage development. The results show that during the falling process, the velocity of rock breaking hammer increases linearly first, then decreases gradually, and finally tends to a stable ending velocity. The speed of the hammer decreases and the damage accumulates in the process of drilling. In addition, the water depth is negatively correlated with the rock damage, while the impact velocity and impact times are positively correlated with the rock damage.

Abstract:Asymmetric excavation has become increasingly common with the development of construction and the progressive collapse caused by the local component failure has attracted many attentions. Aiming at this problem, the three-dimensional finite element software PLAXIS 3D is adopted to analyze the response of the whole retaining system to the asymmetric excavation after local component failure through the method of removing component. The results show that when the braces fail, the earth pressure of piles decreases in the failed area because of the unloading effect but is opposite in the adjacent area. Meanwhile, the moments of piles near intact braces increase greatly. The earth pressure and moment of piles on the same side of the failed piles increase greatly, while on the opposite side they decrease as piles get failed. Piles on the deep side push piles on the shallow side through braces, but the displacement reverses when piles on the deep side failed. The value of soil settlement on the shallow side is less than that on the deep side and increases with the increasing number of failed piles, but the range of settlement almost keeps unchanged. Earth pressure variation coefficient and moment transfer coefficient get surge when the depth difference increases. In addition, the change of depth boundary line has little effect on the earth pressure and pile moment. Finally, a design method is proposed to improve the redundancy of supporting structure through enlarging the reinforcement moment of piles.

Abstract:In order to explore the permeability characteristics of soilbags infilled with expansive soils, a large-scale permeability-test model box was developed. The permeability test was carried out according to the arrangement pattern of soilbags, water flow direction, water head and interlayer filling conditions. The experimental result showed that the horizontal permeability coefficient is greater than the vertical permeability coefficient. The infiltration water could be quickly discharged along the gap between the horizontal layers of soilbags, so that it was not easy to infiltrate into the compacted underlying layer of the expansive soil canal slopes. After filling the gaps between bags with expansive soils, the vertical permeability coefficient changed slightly, while the horizontal permeability coefficient decreased obviously. The permeability of soilbags infilled with expansive soils mainly depends on the size of the gaps. The effect of the soilbag arrangement on the permeability is essentially attributed to the changing of the gap number and shape. In practical, it is expected to provide more preferential flow paths along the horizontal direction if no compacted soils are infilled inside the gaps between soilbags during the actual construction conditions.

Abstract:Using the discrete element method (DEM), a series of numerical simulations of elastic wave propagation are carried out on the particle models of pure soil foundation and soil foundation containing a single-layered soilbag. The influence of the soilbag in the foundation on the elastic wave velocity and the damping of foundation is studied. Numerical simulation results show that the existence of soilbag in the foundation slightly reduces the elastic wave velocity and reduces the quality factor Q of the foundation. The change laws of elastic P-wave velocity and S-wave velocity are roughly the same when they pass through the soilbag. Under the condition of 100.kPa confining pressure and 500.Hz elastic wave input, the attenuation effect of a soilbag on the elastic wave is mainly concentrated when passing through the upper and lower geosynthetic interface.

Abstract:In order to solve the problem that the cement concrete of the airport pavement is easy to produce early micro cracks during the construction period and bring potential safety hazards to the aircraft operation during the service period, this study proposed a method to strengthen the surface performance of the airport pavement by laying fiber mesh in the concrete surface mortar layer. Carbon fiber, aramid fiber and basalt fiber mesh were selected as reinforcement materials to characterize the early cracking resistance of concrete with the early cracking performance of mortar. The effects of water cement ratio, cement sand ratio, fineness modulus and fiber mesh on the early cracking resistance of cement mortar in high temperature and multi wind simulation environment were studied. The results show that the early cracking resistance of cement mortar is the best when the water cement ratio is 0.43, the cement sand ratio is 0.47 and the fineness modulus is 3.4, and when the fiber mesh is basalt fiber with a grid size of 3 mm ×3 mm, the strengthening effect of early cracking resistance is the best.

Abstract:The traditional method to determine the soil moisture content and dry density, which uses the oven drying combined with the cutting-ring, has the problems of long testing period and sampling disturbance, thus a rapid non-destructive testing method was proposed based on the frequency domain reflectometry (FDR) technology in this study. Firstly, based on the relationships of dielectric constant and bulk electrical conductivity with the soil moisture content and dry density, and by using the fitting relationship of dielectric constant and bulk electrical conductivity, the solving equations for soil moisture content and dry density were derived. After that, both the calibration test and model test that simulated the layered filling construction were conducted to verify the applicability of the proposed method. It is found that the proposed mothed to detect the soil moisture content and dry density is feasible with high accuracy.

Abstract:The bending characteristics of drainage plate in super soft foundation and its influence are studied by the theoretical calculation and the model test. Based on the utilization of waste materials, a new type of ribbed structure is proposed, and its bending resistance is theoretically and experimentally analyzed. The results show that the P cr of Euler critical force is very small, and the water flow of Z bend is obviously smaller than that of S bend. When the bending rate increases from 10% to 20%, the vacuum degree of drainage plate core will decrease by 3 to 8 kPa, while the vacuum degree of drainage plate core will decrease by 34 to 46 kPa when the bending rate increases from 20% to 30%. The influence of bending rate on the vacuum degree of plate core and the excess pore pressure of soil is nonlinear. The influence degree is obviously intensified when the bending rate reaches 30%. Based on the idea of waste utilization, the ribbed plate structure is proposed, and the section bending stiffness of ribbed plate structure is 8 times that of the common plate, and the bending resistance of plate body could be increased several times. After reinforcement, the cross-plate strength of dredger fill reaches 16-23 kPa, and the characteristic value of the bearing capacity of mud surface foundation reaches 60-63 kPa, with basically erect plate body after excavation. The ribbed drainage board plays a certain role in enhancing the bending resistance of drainage plate and improving the drainage consolidation effect.

Abstract:In order to solve the defects of relying on the engineering experience, difficult maintenance and reducing the efficiency of the turbine in the traditional layout scheme of the water supply cooler in the secondary circulation technology of the hydropower station, this paper proposes an optimization method for the layout scheme of tail water coolers based on computational fluid dynamics(CFD) through the steady-state numerical simulation of three-dimensional flow in the tailrace. By analyzing the spatial distribution characteristics of multiple physical quantities such as streamlines, flow velocity, turbulent kinetic energy and other physical quantities of the flow field in the area where the cooler is to be installed on the platform above the draft tube in the simulation results, the location with a higher flow velocity from the cooler is selected as the appropriate installation position. The three-dimensional flow domain of the complex tailrace channel considering the geometric model of the actual cooler is established for the numerical simulation and verification to check the rationality of the layout. The simulation and verification results show that this scheme not only meets the cooling requirements of the cooler, but also facilitates the maintenance and avoids any impact on the operation of the unit.

Abstract:In order to improve the efficiency of cable force measurement in the long-span cable-stayed bridge, a cable force measurement method based on the microwave interferometric radar is proposed and the measurement results are compared with those of JMM-268 and DaspBCF. Firstly, the displacements of cables of the bridge were measured by the IBIS-S radar system. Then, based on the collected displacement information, fast Fourier transform (FFT) algorithm was adopted to obtain the frequency spectrum as well as the fundamental frequency of the target cables. Finally, the forces of multiple cables were identified by the oscillating frequency technique. The test results show that: the dynamic information of multiple cables can be measured by the microwave interferometric radar simultaneously with high efficiency; test method that transmits the radar wave from bottom to top can greatly avoid the influence of noise; relative errors between the cable forces calculated by data measured with radar and conventional accelerometers are less than 2.2%, which proves that the test results are reliable. The cable force measurement method in this paper is of high efficiency and easy to operate, which is worth promotion.

Abstract:To effectively suppress the overvoltage of HVDC receiving end system caused by the fault elimination, a coordinated control strategy of synchronous condenser and inverter side extinction angle is proposed. A reactive power regulator (QPC) is added to the conventional control system with a fixed extinction angle at the inverter side for realizing the reactive power control of the converter station by adjusting extinction angle at the inverter side, and at the same time coordinating the reactive power regulator parameters of both the synchronous condenser and the DC control system. The numerical simulation model of HVDC system with the synchronous condenser is built based on the PSCAD/EMTDC environment. The simulation results show that the coordinated control method can effectively reduce the overvoltage of HVDC receiving end system after the accident occurrence and speed up the recovery time of the AC system voltage.