Abstract:Barrier systems are the most important structures for landfills in terms of groundwater pollution control. Analytical solutions to onedimensional models of transport of heavy metals and organic contaminants in clay barriers and composite barriers were summarized in order to evaluate the service life of the barrier systems. The analytical solutions include the solution to a onedimensional model of diffusion of contaminants in clay barriers under piecewise linear adsorption conditions, the solution to a onedimensional model of transport of contaminants in composite barriers with geomembrane defects, and the solution to a coupled model of transport of pollutants in clay barriers under thermal effects. The reliability of highgravity centrifuge tests of longterm transport of contaminants through barriers was assessed. Field investigation was carried out in a 17year old landfill in Anhui Province. The results showed that the maximum migration depth of chloride ion reached 9m, and the maximum migration depth of sodium ions and COD reached 3 to 4m. The technologies of vertical barriers for control of groundwater and soil contamination were summarized and assessed. It was found that the application of soilbentonite cutoff walls in China generates prosperity, and further research areas were discussed.

Abstract:The influence of the dryingwetting alternation on environmental effects of the riparian zone is discussed from four aspects: the physical properties of soil, microbial activity and enzyme activity, growth and distribution of plants, and migration and transformation of nitrogen and phosphorus. Further study on the response of environmental effects of the riparian zone to the dryingwetting alternation should be carried out from the aspects of microscopic mechanisms, the coupling of different mechanisms, and mathematical simulation.

Abstract:In the context of (composite) geomembrane being widely used in many earthrock dams in China and abroad, the reasons for defects and defect classification in geomembrane on the dam surface or inside dams are discussed. Based on a summary of research on the defects and leakage of (composite) geomembrane in China and abroad, it is shown that the existing results cannot be directly used to solve the defect and leakage problems of composite geomembrane used in high earthrock dams. It is also shown that defect evolution, the influence of defectinduced leakage on the dam seepage field distribution and dam safety, and effective measures for leakage control are the development bottlenecks for composite geomembrane application in high earthrock dams. Therefore, laboratory tests should be performed to study the defectinduced leakage of composite geomembrane. It is also necessary to conduct systematic research on some issues related to defect evolution and defectinduced leakage in composite geomembrane used in earthrock dams based on theoretical analysis, numerical simulation, and feedback analysis of practical projects, so as to provide guides for leakage prevention and estoration of composite geomembrane as well as safety evaluation of high earthrock dams with composite geomembrane used for seepage control.

Abstract:The community structures of periphytic algae, macroinvertebrates, and fish in the main streams and tributaries of the Weihe Basin were investigated based on aquatic ecological sampling and survey results from 77 sampling sites. An index of biotic integrity (IBI) was used to evaluate the biological integrity of the three organism groups. The results show that the health assessment results of the Weihe Basin differ with different organism groups, due to their particular responses to environmental disturbance. It was found that the assessment results based on macroinvertebrates were the best, followed by those based on periphytic algae, and the results based on fish were the worst. Generally, the health status of the aquatic ecosystem in the Weihe Basin was poor due to the high level of human disturbance. Throughout the basin, there was a tendency for the health status upstream to be better than that downstream. The main environmental variables that influence the integrity of fish, macroinvertebrates, and periphytic algae in the Weihe Basin were different from one another. Comprehensive investigation of community structure of different organism groups in the Weihe Basin will provide important scientific support for future aquatic ecosystem restoration.

Abstract:Based on the daily precipitation records at 14 national meteorological stations in Poyang Lake Basin from 1961 to 2010, extreme precipitation events were identified using a threshold determined with the percentile method. The spatial and temporal changes of extreme precipitation were analyzed, and the trends were examined through linear regression. The results show that, during the period from 1961 to 2010, extreme precipitation showed larger changes than annual precipitation. The intensity of extreme heavy precipitation showed a significantly increasing trend, while the duration of extreme heavy precipitation events showed a significantly decreasing trend. The areas showing a significantly increasing trend were mainly located in the Ganjiang Basin and Fuhe Basin. Extreme precipitation in most stations in the Poyang Lake Basin did not show abrupt change. The extreme precipitation events showed a more concentrated trend on a temporal scale. These changes of extreme precipitation events will lead to more serious challenges for water resources management in the Poyang Lake Basin.

Abstract:In order to study the water column separation phenomenon and analyze the factors of pressure boosts and breaking length during the process of stopping a pump for a system, a test model was designed to cause cavity water hammer to occur in two places at the same time. Through the test model, we observed the water column separation phenomena. These phenomena included a completely vaporized state, a completely blocked cavity state, a blocked cavity and vaporized state, and notcompletely block cavity state. The test results show that the initial flow rate and valve closing speed are the two most important factors that influence the water hammer pressure and breaking length. When the flow rate is higher, the water hammer pressure is greater and the breaking length is longer. When the valve closing speed is faster, the water hammer pressure is greater and the breaking length is longer. When there is a higher flow rate, the pipeline layout form has a large influence on water hammer pressure when the pipeline system has devascularization in two places.

Abstract:In order to reduce the influence of a plug energy dissipater on the conveyance capability, a tooth block energy dissipater was investigated through physical modeling experiments. Through the testing of three schemes with different numbers of tooth blocks and the same area contraction ratio of 0.375, the conveyance capacity, local head loss coefficient, energy dissipation effect, turbulence intensity, and characteristics of fluctuating pressure were analyzed. The results show that the number of tooth blocks has a certain effect on the energy dissipation effect, and, in the experimental range, with the increase of the number of tooth blocks, the conveyance capacity increases, the local head loss coefficient decreases, and the energy dissipation efficiency declines. The maximum turbulence intensity occurs 1.5 times the tunnel diameter away from the inlet of the tooth block, and then become stable further than 7 times the tunnel diameter away. The maximum fluctuating pressure occurs 1.3 to 1.6 times the tunnel diameter away from the inlet of the tooth block, then sharply decreases, and finally become stable 5.6 times the tunnel diameter away from the inlet of the tooth block.

Abstract:In order to study the air concentration distribution in the flow area near the solid bottom and walls of a chute, the length of a protective segment in response to a combination of bottom and lateral aerators with different heighttolength ratios was investigated through model experiments, and the sensitivity of the length of the protective segment of the aeration facility to the heighttolength ratio of the aerator was analyzed using the singleparameter sensitivity analysis method. The results show that, when the conditions of other factors remain unchanged, the length of the protective segment of the bottom aerator increases with the discharge and the heighttolength ratio of the bottom aerator, and increases slightly with the heighttolength ratio of the lateral aerator. The length of the protective segment of the lateral aerator increases with the discharge and, with the increase of the heighttolength ratio of the lateral aerator, it increases quickly at first and then slowly. Although the sensitivity of the length of the protective segment of the lateral aerator to the heighttolength ratio of the lateral aerator is higher than the sensitivity of the length of the protective segment of the bottom aerator to the heighttolength ratio of the bottom length, the heighttolength ratio of the bottom aerator is more important to the whole length of the protective segment of the aeration facility. The length of the protective segment can be effectively increased only when a reasonable combination of aeration facilities is used.

Abstract:In order to study the influence of the shear properties at the steelsoil interface with dryingwetting cycles on the softening deformation of soil around the steelcasing rocksocketed pile, initial samples with a certain moisture content, dry density, and gradation were designed. And shear tests on the steelsoil interface and soil body were carried out in five cases, including a initial state and four different numbers of dryingwetting cycles. In each case, samples were subjected to four vertical pressures: 50kPa, 100kPa, 150kPa, and 200kPa. The results show that the influence of dryingwetting circles on the shear strength of soil is greater than that on the shear strength of the steelsoil interface. During the shear process, there is an elasticplastic stressstrain relationship, and no strainsoftening phenomenon occurs at the steelsoil interface under dryingwetting circles. With the increase of the number of dryingwetting circles, the friction angles of the steelsoil interface and soil change little, while their cohesive forces increase first and then decrease.

Abstract:A novel extended embedded crack finite element method (XE-FEM) is proposed for modeling localized failures in concretelike quasibrittle materials and structures. Based on the unified multiscale kinematics recently developed by the authors, the displacement jumps at the cracking nodes, where cracks intersect with the element edges, are selected as the elemental enrichment parameters. In addition to constant displacement jumps induced by relative translations of rigid bodies, linear deformation modes caused by rigid body rotation and selfstretching are consistently accounted for in the kinematics, so that the spurious stress locking can be removed. The enrichment parameters, which are shared by neighboring elements, can be regarded as global variables in the numerical implementation. Thus, the continuity of the displacement jumps can be guaranteed along the crack propagation path. Two benchmark tests of concrete structures, i.e., the wedgesplitting test with modeI failure and the singleedge notched beam with mixedmode failure, were numerically simulated to validate the suggested method. The calculated response of load versus displacement and crack paths were compared to available experimental data and numerical results obtained from other methods. It is shown that the suggested method is stable and robust, with a high resolution in regard to coarse meshes.

Abstract:In order to improve the integrity and strength of rockfill material as well as the seismic stability of earthrockfill dams, a new technique of using polyurethane foam adhesive (PFA)reinforced rockfill material to reinforce the shallow zone beneath the dam crest and slope, based on analysis of seismic disasters and aseismic measures of high earthrockfill dams, is presented. The effects of PFA on the mechanical behavior of rockfill material were studied through static and dynamic triaxial tests. The test results show that PFA significantly increases the cohesion of rockfill material, slightly increases the dynamic elastic modulus of rockfill material, and significantly reduces the residual strain of rockfill material. The PFAreinforced rockfill material show good seismic behavior. The numerical results regarding a high earthrockfill dam show that, after use of the proposed technique, the minimum safety factor against sliding during an earthquake is increased by 10％, indicating that the seismic stability of the dam is improved.

Abstract:The composition, characteristics, construction equipment, construction process, and quality inspection method of cast-in-place concrete piles (TC piles), with singlewall corrugated PVC plastic tubes used in the construction process, are introduced. In combination with the soft foundation project of the Lianshi-Hangzhou section of the Shen-Jia-Hu-Hang Expressway reinforced by TC piles, the distribution and variation of the soil stress on the top of pile caps, and that between and under pile caps were compared and analyzed based on observations by embedded earth pressure cells and rebar stress meters. Variation curves of the pilesoil stress ratio and load sharing ratio against the filled load were obtained. The results show that the embankment load is gradually transferred to TC piles, and the pilesoil stress ratio increases first and then decreases as the height of embankment is increased. During the measurement period, the pilesoil stress ratio and load sharing ratio of TC piles tend to increase.

Abstract:The boundary face method (BFM), combined with a fast algorithm, was applied to transient heat conduction analysis of concrete dams during the pouring process, so as to predict the temperature distribution and its time history in concrete dams during the construction process. Using the time convolution method to compute the time integration and the Taylor series expansion method to separate the spatial variables and time variables in fundamental solutions, the spatial variable integrals can be calculated and stored at the same time, improving the calculation efficiency of the convolution integral. A case study shows that the temperature distribution obtained by the fast BFM agrees with the results of the finite element method, demonstrating the feasibility of application of the fast BFM to transient heat conduction analysis during the actual dam construction process.

Abstract:In order to test the reliability and performance of a flexiblewall permeameter (FWP), comparative tests of a FWP and a fallinghead permeameter were conducted with cementsoil samples, cement slurry samples, and soil samples, and comparative tests of different seepage pressures and sample heights and diameters were conducted for the FWP. The test results show that the FWP can provide accurate results, a reliable performance, and airproofed flexible walls, and it does not have strict requirements for sample preparation, which enable us to freely select the height and diameter of samples within a certain range. Permeability test with the FWP can be quickly finished using highseepage pressures. The FWP can be used to test cementsoil, cement slurry, and plastic concrete samples with permeability coefficients less than 1×10^-5cm／s and hard soil samples with permeability coefficients less than 1×10^-6cm／s.

Abstract:Based on analysis and measurement of a geostress field at the dam site of the Jiangpinghe Hydropower Station, and comparison of calculated and measured stress at the points for stress fitting, inverse analysis of the initial geostress field at the dam site of the Jiangpinghe Hydropower Station was conducted using a threedimensional numerical model with different boundary loading conditions. The results show that the initial geostress is low at the dam site of the Jiangpinghe Hydropower Station, the maximum principal stress is 2.5MPa and its direction is N45°W, and the minimum principal stress is 1.5MPa with a direction of N45°E. There is agreement between the calculated and measured stress at the points for stress fitting, indicating that the initial geostress field at the dam site obtained by inverse analysis is reasonable and conforms to the historical background of the geological structure.

Abstract:The optimal design of an overall sluice structure on a soft foundation was studied,with a sluice in North Jiangsu Province as a case study. A mathematical model for the optimal design of the sluice was established, in which the key geometrical parameters for the sluice chamber and pile group foundation structure were the design variables, the minimum cost for the construction of the sluice chamber and pile group foundation was the objective function, and the antisliding stability of the chamber structure, bearing capacity of the foundation, stress in the basement, strengths of the chamber and pile foundation structures, settlement of the chamber structure, and horizontal displacement at the top of piles were the main constraint conditions. Using the optimization module in the software ANSYS, the optimal design schemes for the overall sluice structure and chamber structure were obtained, respectively. Compared with the optimal design scheme for the chamber structure, the optimal design scheme for the overall sluice structure shows that the total cost in the sluice construction decreases by 2.7％, and the horizontal displacement at the top of piles reaches the critical limit, demonstrating a better optimization effect.

Abstract:In order to control the maximum temperature in an arch dam during its construction period, a performance function for control of the maximum temperature in the dam body was constructed based on the reliability theory, in which the influences of randomness of the atmospheric temperature and concrete parameters on the temperature field and stress field of the arch dam were considered, and the atmospheric temperature and concrete parameters were taken as the random variables. The response surface method was used to solve the problem, in which the performance function cannot be explicitly expressed, and a new mode for solving the failure probability and reliability index of temperature control in the dam body during the construction of the arch dam was developed. The calculation results show that the error of this method is less than 8.36％ as compared with the results of the Monte Carlo method. The method allows the user to avoid largescale numerical computation and improve the computational efficiency significantly with a high level of accuracy.