Abstract:Taking the Dalian City as the research area, based on the GIS technology, the analytic hierarchy process (AHP) and entropy weight method (EWM) were introduced to evaluate the comprehensive risk of rainstorm-flood disaster by using the daily precipitation data and socio-economic data of the Dalian City. 18 indicators in the risk assessment of rainstorm-flood disaster were selected to build the comprehensive risk assessment model of rainstorm-flood disaster in Dalian City from four factors, consisting of the hazard, exposure, vulnerability and emergency response & recover capability. The results of comprehensive risk assessment showed that the spatial hazard distribution of rainstorm-flood disaster in Dalian City has the characteristics of being higher in the northeast and southwest and lower in the middle. The exposure and emergency response & recover capability of rainstorm-flood disaster were lower in the northern Dalian, but higher in the southern Dalian. The vulnerability of rainstorm-flood disaster was higher in the southwest and central Dalian, while that was lower in the northeast and southern Dalian. The comprehensive risk grades of rainstorm-flood disaster in Dalian City were mainly medium risk, accounting for 41.3% of the whole study area, and they were distributed in patches from the northeast to the southwest. The low risk areas, accounting for 20.93% of the total area, were mainly distributed in the northwest of Zhuanghe and Wafangdian, while the high-risk areas were small, only accounting for 0.72% of the whole area, in the Shahekou District and the Changhai County. As the high-risk areas of rainstorm-flood disaster in Dalian City, they are extremely likely to encounter the flood disaster under extreme rainstorm conditions and have become key areas for the flood control with more attentions.

Abstract:After the extreme rainstorm disaster in Zhengzhou, urban roads, subway tunnels and other transportation projects are potentially to encounter dangers such as the road cavity, tunnel deformation and water seepage. In order to find out these hidden dangers, according to the categories of hidden dangers after the rain disaster and the characteristics of various detection methods, through the combination of vehicle mounted 3D ground penetrating radar, towed transient electromagnetic detection, mobile 3D laser scanning and other detection methods, the emergency detection of road cavity and tunnel diseases was carried out. The results show that the combination of vehicle mounted 3D ground penetrating radar and towed transient electromagnetic detection can effectively avoid the limitations of a single method and quickly find out the diseases, such as the cavity and the leakage of transportation engineering. The safety status of tunnel engineering can be quickly found out by using 3D laser scanning and then using the ground penetrating radar to investigate the main disease information of tunnel structure in detail.

Abstract:Based on observations from automatic weather stations, the extremes, periods and hourly variation characteristics of precipitation and the urban flooding influence are analyzed for the “7·20” extreme rainstorm in Zhengzhou City, Henan Province, and some suggestions on the prevention and control of waterlogging under over standard precipitation conditions are put forward. The results show that this is an extreme precipitation weather process, and can be divided into five obvious precipitation periods. The short-term heavy precipitation shows characteristics of frequent occurrence and repeated occurrence at the third and fourth periods, while the continuous precipitation heavier than 80 mm/h in the main urban of Zhengzhou from 12:00 to 18:00 CST on 20 July is the principal cause of the serious urban flooding. The current design standards of unban flooding prevention is not enough to prevent precipitation with this intensity in the main urban area of Zhengzhou City, but we could reduce the flooding disasters by improving the emergency system of urban flooding prevention while exceeding standard, raising the urban flooding prevention standards at prone points, and measures like this.

Abstract:Based on the observation of automatic weather station, the wind profile radar and the NCEP reanalysis data, this paper analyzes the fine characteristics and causes of the torrential rain caused by typhoon MAYSAK in 2020, and makes a brief comparison with typhoon Bolaven in 2012. The results show that: the precipitation brought by typhoon MAYSAK has the characteristics of the large influence range of wind and rain, the long duration of precipitation and the asymmetric precipitation; The heavy precipitation caused by MAYSAK in northeast China was closely related to the combination of MAYSAK and westerly system. The asymmetric structure developed after the northward typhoon entered northeast China, and the involvement of dry/cold air and frontogenesis area on the west side of MAYSAK led to the continuous and asymmetric distribution of precipitation; The large-scale circulation of Bolaven and Meshak showed a situation of "low in the west and high in the east", but the anomaly degree of the circulation of MAYSAK, the degree of the system tilting to the west with the height and the strength of the frontal zone were stronger than that of Bolaven, so the precipitation also showed a longer duration and a larger range.

Abstract:To reveal the vertical distribution characteristics and potential ecological risk of nutrient elements and heavy metals in the sediment of a black and odorous urban river, taking the Nanhe River in Nanjing City as an example, sediment columnar samples (0 ~ 120 cm) from four sections were collected to analyze contents of total nitrogen (TN), total phosphorus (TP), organic matter (OM) and heavy metals (Cr, Ni, Cu, As, Cd, Hg, Pb, and Zn), and their potential ecological risk assessment and correlation analysis were studied. Results show that the nutrients and heavy metals in the sediment exhibited wide spatial differences, which is that the contents of TN, TP and OM in the sediments of northern section were significantly higher than those in the southern section. TN and TP increased with the depth and then decreased, with peaks at the depth of 40 ~ 80 cm. Contents of heavy metals in the southern and northern sections were higher, particularly the contents of Ni, Cd, and Pb in the sediments in the southern section and the contents of Cu, Hg, and Zn in the northern section reached more than twice of the middle section. Along the depth direction, except Hg and Zn, the content of heavy metals increased gradually with the depth within 60 cm. Potential ecological risk assessments showed that Hg and Cd in the sediments reached a very strong ecological hazard level, followed by Ni and Zn, while as showed little ecological hazard. Correlation analysis showed that Cu was significantly correlated with TP, TN, and OM, Ni and Cr were significantly positively correlated with Zn, and Cd, Pb, As, and Zn were significantly positively mutual-correlated. Heavy metals and nutrient elements in the sediment reached a high pollution level and showed a compound pollution trend.

Abstract:Considering that most projects in cold regions are located in arid or semi-arid regions, this paper comprehensively analyzes the migration mechanism of liquid water and gaseous water in the frozen soil and the model of hydrothermal coupling, in order to provide theoretical support for the study of the migration mechanism of mixed state water in frozen soil, as well as the prevention and control of engineering freezing damage. The research progress of soil water potential theory and vapor transfer-induced freezing theory are summarized, and at the same time, detailed reviews on the traditional moisture migration force theory of frozen soil and migration force theory of water vapor are analyzed. Then, a deeply analysis on the water increasing mechanism in the engineering foundation is conducted, and in addition, this study also summarizes coupled models of the water thermal force and water-vapor, with comparing the characteristics of different numerical model. According to the analysis, the following results can be obtained that considering that the concept of pressure of ice-water phase pressure is not clear, the applicability of Clapeyron equation in the frozen soil needs to be further evaluated. The traditional water migration theory is based on liquid water and ignores the influence of water vapor migration. The water accumulation mechanism of unsaturated soil is well explained by cold condensation and evaporation condensation of water vapor. Meanwhile, the theory of the vapor transfer-induced freezing can well explain the engineering freezing damage caused by the water vapor migration. Finally, the hydro-thermal coupling theory does not fully represent the action of stress field and cannot fully reveal the formation and development process of soil frost heave.

Abstract:A distributed Green-Ampt rainfall-runoff model based on orthogonal grids was built and applied to two semi-arid basins in the Loess Plateau of Northern Shaanxi Province to test its performance. The results show that in the two semi-arid basins, the distributed Green-Ampt model performs better than the GA-PIC model and the traditional Green-Ampt model, especially in the flood peak simulating. The distributed Green-Ampt model has higher accuracy in simulating the time from the confluence to outlet section of basin with the grid-based slope confluence and river confluence module. In addition, the distributed Green-Ampt model is able to calculate the runoff process at different locations of the basin more accurately, and also able to simulate the runoff area distribution of the basin more accurately. The spatial and temporal distribution of rainfall in the semi-arid area is uneven and the infiltrated-excess runoff is mainly affected by the rainfall intensity,therefore the rainfall observation accuracy has a great impact on the runoff forecasting accuracy.

Abstract:This study aims to improve the accuracy of flood simulation and forecasting based on improving the quality and spatiotemporal resolution of driven data (precipitation) in small and medium-sized watersheds. The utility of a multi-source precipitation merging method based on the mixed geographically weighted regression and MGWR-BI function was evaluated, and the effect of the merged precipitation to the calculation result of the WRF-Hydro model was studied. The merged precipitation data was used in the WRF-Hydro model for the flood forecasting in the Ziwuhe Basin, and the results were compared to the observation data of station. The comparison results show that the merged precipitation data have substantial higher quality than the downscaling CMORPH satellite data by comparing to the ground observations. Flood events are better captured by the WRF-Hydro model driven by the merged precipitation data than the downscaling CMORPH satellite data for small and medium-sized watersheds. Therefore, the WRF-Hydro model with merged precipitation data has a potential advantage of flood simulation and forecasting for small and medium-sized watersheds.

Abstract:The influence of microbial induced calcite precipitation (MICP) reinforcement on the static properties of large diameter monopile was studied by the numerical model, including the bearing capacity, internal force distribution and deformation mode of mono pile, and the sensitivity of different reinforcement range, reinforcement shape and reinforcement strength was also analyzed. The results show that MICP can effectively improve the bearing capacity (up to 70%) and the internal force distribution of monopile. As for the deformation mode of monopile, it does not change, but reinforcement will change the deformation range of soil around the pile. For different reinforcement ranges, the critical reinforcement depth is one pile diameter (1D), and the critical reinforcement radius is 3D. For different reinforcement shapes, the bearing capacity from large to small are the cylindrical shape, the inverted cone and the positive cone. Considering economic factors, it is suggested to use the inverted cone reinforcement in engineering practices. As the strength of reinforced soil increases, the bearing capacity also increases.

Abstract:In order to improve the problem of the unreasonable structure of inland water transport development, considering the game relationship between cargo owners, shipping enterprises and waterway network planners, a bi-level programming model for the optimization of waterway network is constructed in this paper. The upper-level model takes the minimum sum of the construction cost and the operating cost of the waterway network optimization plan as the objective function, and the lower-level model adopts the waterway network assignment model based on the user equilibrium. Finally, by taking Shandong Province as an example, the genetic algorithm is used to solve the model, and three evaluation indicators are selected to compare and evaluate the results of the optimized plan and the original plan. The results show that the Shandong Province waterway network optimization scheme obtained in this bi-level programming model is more superior to the original program, which improves the actual transportation efficiency of the waterway and verifies the effectiveness of the proposed model.

Abstract:Mathematical models for coupled morphological evolution of beach-dune system considering both the subaqueous and aeolian sediment transport processes can better predict the sandy coastal evolution on a larger spatial scale, providing the basis for coastal protection and the comprehensive management. This paper summarizes the research progress of beach-dune morphological models, including the conceptual models, the nearshore hydrodynamic and sediment transport models, the coastal aeolian sediment transport models, and the coupled subaqueous and aeolian sediment transport models. The state-of-the-art models can address the storm-induced beach-dune erosion and sediment exchange, as well as the supply limited aeolian sediment transport and the dune recovery on the time scale of years. They are still limited in universality, accuracy and computational efficiency. Four aspects of future research are suggested, including the consideration of key process, the improvement of computational efficiency, the expansion of spatial dimension and the test of practical application.

Abstract:In order to participate in the international exchange of Bailong buoy data with the standard format, the data transmission process is designed, including the data measurement, satellite transmission, station receiving, real-time data quality control, storage in cloud, and data link for uploading to China Meteorological Administration (CMA) via FTP. According to the standard binary universal form of the representation of meteorological data (BUFR) recommended by World Meteorological Organization (WMO), CMA converts the original format into BUFR and packs them according to the rules of Global Telecommunication System (GTS). At present, the meteorological and ocean observation data of Bailong buoy is distributed and shared to GTS in real time. Global users can get the Bailong buoy data from GTS, and identify and decode the data by the header identification. The Bailong buoy becomes the first Chinese mooring buoy shared with other countries by GTS, which indicates that the data providing capacity of China's climate mooring buoy has achieved the world's advanced level.

Abstract:Based on the higher resolution wave data in the fifth-generation reanalysis dataset provided by the European Centre for Medium-Range Weather Forecasts, the temporal and spatial distribution characteristics of surge and mixed wave energy flux in eastern China Sea area in 2017 were calculated and analyzed, and the transmission characteristics of wave energy flux in this area were studied as well in this paper. The results show that the mixed wave and swell wave energy flux in the study area mainly flow to the open sea, and the transfer direction of wave energy flux is basically the same. The energy flux of swell wave is larger than that of mixed wave in number. Generally speaking, there is a large wave energy current in the eastern part of China’s continental shelf, which flows from each channel to the open sea. The distribution of mixed wave energy flux in the study area has obvious seasonality, which is larger in autumn and winter and smaller in spring and summer, and the largest value is located near the Tokara, Amami, Miyako and Taiwan Strait.

Abstract:In order to investigate the dissolution mechanism of chloride in the desalination process of sea sand, desalination experiments were conducted by different methods to analyze the relationships of the amount of dissolved chloride with time and water-sand mass ratio. Based on the distribution and dissolution characteristics of chloride in sea sand, a chloride dissolution model considering both the surface chloride solution and the internal chloride dissolution was developed, from the dissolution and diffusion theory derived from the Fick's law. The results of model validations show that this model can well describe the chloride dissolution process and reflect the influences of time and water-sand mass ratio on the desalination effect of sea sand.

Abstract:To analyze the influence of confining pressure and pore air pressure on the rock mechanical properties under different stress paths, conventional triaxial tests under the gas undrained condition were carried out on a low-permeability and tight red sandstone. The experimental results show that the confining pressure has a strengthening effect on the sandstone. As the confining pressure increases, the strength and ductility of the rock increase significantly, and the rocks eventually show the form of shear failure. The pore air pressure reduces the compressive strength, while increasing the brittleness and internal tension of the sandstone, by damaging the internal continuous structure and leading to the occurrence of splitting failure plane.

Abstract:In order to reduce the traffic accidents that occur in rainy days due to the water film effect, this paper reviewed the research progress of water film on asphalt pavement,analyzed the calculation results of water film thickness at home and abroad, and summarized the types and decision criteria of hydroplaning. Meanwhile,the critical hydroplaning velocity was described in detail from the aspects of experiment, formula or equation established by the mechanical model,numerical modeling and simulation. Finally, the summary and comparative analysis were conducted.