Abstract:In consideration of the dynamic response of a concrete-face rockfill dam(CFRD)to earthquakes, the calculation method and evaluation standards for seismic damage to CFRDs are investigated from the aspects of the seismic stability of dam slope, permanent deformation of dam body after earthquakes, liquefaction of foundation overburden, and deformation of slab joints of the CFRD. The maximum seismic capacity of a 135 m CFRD on an alluvium deposit is calculated using the three-dimensional finite element method. Result analysis shows that the dam has strong earthquake resistance, with a maximum seismic capacity of about 0.52g to 0.54g.

Abstract:The forces on a spherical particle settling in still water with a high Reynolds number were investigated based on the settlement mechanisms of single particles of sediment. The formulas of instantaneous settlement velocity, settlement duration, and settlement displacement during accelerating settlement were deduced. The computational results from the formulas were compared with the experimental results. It was found that the relative errors were all less than 5% between the computational displacement and experimental data, and most of them were less than 4%; and the relative errors were all less than 7% between the computational instantaneous settlement velocity and experimental data, and most of them were less than 5%, indicating that the computational values agreed with the experimental data.

Abstract:Based on the trend analysis method and the change-point testing method, trends of the hydro-meteorological elements for the Daling River Basin were detected. The annual runoff time series was divided into a “natural period” and an “impacted period” based on the human activities characteristics and change point analysis results for the river basin. A hydrological model was established based on hydrological, meteorological, and land use data from the upper Daling River Basin. Through the elastic coefficient method and hydrological simulation method, the effects of climate change and human activities on runoff in the study area were analyzed quantitatively. The results show that the precipitation of the study area has been increasing slightly during 1956—2006, and the potential evapotranspiration and runoff show a significant decreasing trend, mainly due to human activities.

Abstract:The chicken swarm optimization algorithm was validated using 15 complex functions, and the simulated results were compared with those of the Wolf algorithm, particle swarm optimization algorithm, fish swarm algorithm, and genetic algorithm. Using the chicken swarm optimization to search for the optimal projection direction of the projection pursuit model, a projection pursuit evaluation model was established. Using assessment of flood and drought disasters from 1990 to 2013 in Wenshan Prefecture as an example, five flood disaster evaluation indices, including disaster-affected population, and four drought disaster evaluation indices, including the disaster area of crops, were selected, and grading standards for flood and drought disaster assessment were constructed with the mean and standard deviation of the flood and drought disaster projection series. The results show that the chicken swarm optimization algorithm is robust and has high global optimization ability. Using the algorithm to select the optimal projection direction of the projection pursuit model can effectively improve the evaluation accuracy and prevent a high degree of variation from occurring in the optimal projection direction.

Abstract:In order to thoroughly research the hydrodynamic characteristics of a stilling basin with a drop sill, and provide a reference for its design and protection, the distribution characteristics, amplitude, and spectral features of the fluctuating pressure were studied based on physical model experiments. The experimental results show that the flow condition is the main factor influencing the fluctuating pressure, and the fluctuating pressure coefficient of the stilling basin slab increases and then decreases in the direction of streamflow, before finally stabilizing. The fluctuating pressure of the middle line of the slab is close to that of the side wall, and the maximum fluctuating pressure at these two locations reaches 5.1% of the total water head. The maximum fluctuating pressure occurs in the region near the chute sidewall extension line in the front of the stilling basin, and it reaches 11.5% of the total water head. Compared with a traditional stilling basin, the fluctuating pressure of the middle line in the front of the stilling basin significantly decreases, and the maximum difference reaches 55.2%.

Abstract:In order to improve the wave-dissipating performance, a new grille plate-type open breakwater is presented. Based on flume experiments, the wave-dissipating performance of this breakwater was analyzed, and the influence of parameters, including the relative spacing between the upper and lower plates and the gap ratio of the grille plate, on the transmission coefficient and reflection coefficient were investigated. The results show that the wave-dissipating performance of this breakwater is satisfying, and it is better when the breakwater is above the still water level than when the breakwater is submerged; the transmission coefficient of this breakwater decreases with the increase of relative plate spacing; and the breakwater performs best at a gap ratio of the top and bottom plates of 0.1.

Abstract:In order to study the impact of fine particles(d ≤ 0.075 mm)of the soil body of debris flow on the inoculation and startup mechanisms of debris flow during the rainfall infiltration and interstitial flow processes, an experiment on slope debris flow induced by artificial rainfall, using a self-made debris flow model tank and an indoor slope model made of three kinds of fine particle soil bodies, was carried out. The experiment studied the formation characteristics of slope runoff, soil erosion characteristics, and slope instability modes of the soil body of debris flow during the rainfall infiltration process. The experimental results show that fine particles of the slope will disperse, drain, and cause coarsening of the surface soil of the slope. The dispersed fine particles of a slope with high fine particle content will migrate to depth, block the holes, and decrease the permeability(infiltration capacity)of the slope soil, inducing slope runoff and slope failure before the wetting front extends to the lower soil-rock interface, with the failure surface being close to the wetting front(only a few centimeters away). The failure mode can be described as sliding-flowing failure of the block at first, and then gully erosion. The scale of soil erosion is related to the rainfall intensity and fine particle content. The failure mode of slope soil with low fine particle content can be described as retrogressive slumping. However, in the experimental process, no massive soil loss occurs, the blockage in the holes of soil with low fine particle content caused by the dispersion and migration of fine particles is not significant, and relatively stable flow with fine particles forms at the soil-rock inter-surface. The fine particle content of the slope soil is important to the slope failure mode and formation of the slope runoff. The security coefficient obtained from the slope stability analysis model considering the impact of the slope runoff shows better agreement with reality.

Abstract:In order to study the influence of concrete strength grade, volumes of fly ash and slag powder, and air-entraining content on the frost-salt resistance of concrete, an accelerated freeze-thaw test of concrete in salt solution was carried out. The correlation between the air-entraining contents of fresh concrete and hardened concrete was validated through measurement of bubble parameters of hardened concrete. The variation of surface characteristics, relative dynamic modulus of elasticity, and cumulative amount of spalling of concrete with the number of freeze-thaw cycles were investigated. The influence of concrete strength grade, volumes of fly ash and slag powder, and air-entraining content on the frost-salt resistance of concrete was examined. The results shows that a higher concrete strength does not always improve the frost-salt resistance, the air-entraining content is the decisive factor influencing the frost-salt resistance of medium-and low-strength grade concrete, and the volumes of fly ash and slag powder should be controlled within an appropriate range.

Abstract:In order to evaluate the impacts of hydropower development on the ecological environment, the impacts of the cascade development of hydropower projects in the main stream of the Tongtian River on the terrestrial ecological environment were analyzed and evaluated using the “3S” technology combined with the methods of landscape ecology and the ecological security index, as well as data from digital images and field surveys. The results show that, subsequent to cascade hydropower development, the water area increased by 300.72 km², the grassland area decreased by 296.80 km², and there was no significant change in the main vegetation types and land use patterns. Grassland was the dominant landscape type in the basin, followed by bare land and woodland. Landscape fragmentation decreased after hydropower development, while landscape dominance and diversity increased, which was conducive to the stability of regional ecosystem. Cascade hydropower development did not significantly affect the productivity of vegetation in the basin and the richness of species on both sides of the river. The productivity of vegetation decreased by 1.83×10⁵ t/a, and the productivity after the development only accounted for 0.78% of that before the development. The ecological security index of the overall basin was 0.819 after the development, 0.001 higher than that before it, indicating a high ecological security index. In summary, since there were no major changes in landscape patterns or in ecosystem features and functions, cascade hydropower development does not pose a threat to the ecological environment and safety in the Tongtian River Basin.

Abstract:Based on remote sensing technology and its comparison with different types of information, changes in the coastline in Yancheng City were identified during the planned period of reclamation. Combined with field investigation and expert consultation, evaluation was carried out in terms of spatial layout of the reclamation area, functional zoning, sustainable supply capacity of tidal flat resources, ecological environmental protection, and construction of integrated experimental areas. The results show that, due to the slow development and reclamation of tidal flats in Yancheng City, the future reclamation plan should be locally adjusted according to the natural conditions and economic development requirements. With abundant tidal flats suitable for future development in Yancheng City, and with infrastructure construction coordinated with the development progress of the reclamation area, the tidal flat resources have high sustainable development capacity. Large-scale development and utilization of tidal flats will influence the dynamic conditions of water and sediment as well as the marine ecological environment. It is pointed out that an integrated reclamation environmental impact assessment model should be built based on the costal environmental characteristics, so that it will provide a basis for the sustainable development and utilization of tidal flats in the future.

Abstract:Based on the characteristics of seawall failure, main factors threatening seawall safety are summarized in terms of the two forms of failure, overtopping and breaches. An index system for seawall safety assessment was established based on the analytic hierarchy process(AHP). Based on features of seawall design in China, the membership degree method from fuzzy mathematics was used to quantify every index according to the Code for Design of Sea Dike Project(SL 435—2008). The index system for seawall safety assessment was applied to a seawall in Taizhou, in Zhejiang Province, in order to assess the risks of overtopping and breaches. The results show that this seawall meets the design requirements for a return period of 50 years. The established index system for seawall safety assessment can be used to investigate the risks of overtopping and breaches of other seawalls.

Abstract:This study focuses on the transcendental equation with multiple unknowns for determining hydrogeological parameters in an anisotropic aquifer that cannot be directly determined through the conventional analytical methods. The existing methods for solving the equations, including the standard curve comparison method, linear graphic method, and improved linear analytical method, encounter many personal errors, a restricted application scope, and a burdensome and complicated computational process. In this study, adopting the optimum fitting method, a calculation formula for directly determining parameters was constructed using a simple function replacing the well function with a series expansion within the range of engineering adaptive parameters and a drawdown ratio relationship obtained through six selected points on the drawdown curves in three observation holes. The solution of the calculation formula is simple, intuitive, and easy to use. Precision analysis indicates that the maximum error is less than 2% across the range of engineering adaptive parameters, fully meeting the requirements of actual engineering calculation precision.

Abstract:The main engineering diseases and types of damage to road subgrade in China and abroad are briefly introduced, and the most commonly used detection methods are summarized. The principles, ranges of application, and advantages and disadvantages of these detection methods are comparatively analyzed. In combination with subgrade treatment of the Jiangsu coastal highway, applications of the core drilling detection method, which may cause damage, and the geological radar detection method, which does not cause damage, are analyzed in detail, and the effects of the two methods for subgrade treatments are also evaluated. The results show that the geological radar method can be used in grouting tests in the vertical direction, and the pile boundary can be clearly distinguished. They also show that the core drilling method can reflect indices of the plastic-liquid limit, density, dry density, and water content of road subgrade quantitatively and intuitively, and has obvious advantages in local surveying.

Abstract:In order to investigate the feasibility of using pumice lightweight aggregate concrete as channel lining material, a canal lining board of pumice lightweight aggregate concrete was produced using natural pumice, sand, cement, water, and industrial waste fly ash. The foundation soil temperatures of an unlined canal, a normal concrete-lined canal, and a pumice lightweight aggregate concrete-lined canal were compared. Meanwhile, the morphology characteristics of the normal concrete cross-section and the pumice lightweight aggregate concrete cross-section were compared using image-processing software. The results indicate that the pumice lightweight aggregate concrete lining can effectively slow down the rate of heat exchange between the foundation soil and surrounding environment, inducing that the foundation soil temperature changes slowly throughout the freezing period and foundation soil congelation delays or does not occur. The proportion of the area of visible closed holes of pumice lightweight aggregate concrete to the whole cross-section area is far greater than that of normal concrete in the case of the same amount of air-entraining agent.

Abstract:A review is conducted of advances and developing trends over recent years in numerical methods for simulation of landslides and surges in four stages, including slope instability, slope sliding, surge generation, and propagation, in reservoir districts. The achievements in numerical methods for simulation of slope sliding and surge generation are summarized. It is pointed out that landslides and surges should be considered an integrated continuous process from the slope instability to surge propagation stages, and, based on current research of each stage, the relevant research methods of solid and fluid mechanics should be combined in future research, so as to construct numerical models for the entire simulation process of landslides and surges in reservoir districts.

Abstract:Methods for description of fractal characteristics of geometric topological parameters of a rock fracture network system, including the length, aperture, orientation, and location, are reviewed. Percolation characteristics in the rock fracture network system and the important role of CT scanning technology in analyzing the fractal characteristic of fractures are pointed out. Achievements in research on the connectivity of the fracture network system using the percolation theory, methods for generation of the rock fracture network system based on the Monte-Carlo method, and simulation of fluid seepage in a fractal discrete fracture network system are systematically introduced. It is concluded that a model of the rock fractal discrete fracture network system constructed based on fractal characteristics and percolation characteristics can reflect the real rock fracture structure and seepage mechanism in the fracture network system. However, there is no large-scale commercial software for numerical simulation of percolation at present. Construction of a numerical model for the fractal discrete fracture network system based on the percolation theory will become the major research focus.