According to observed data of hydrology, sediment and topography of the bending braided channel at Wuhan’s Tianxingzhou reach in the middle Yangtze River, we analysed the changes of flow dynamic axis, flow velocity and sediment concentration distribution in the presence of varying flow and sediment. We also expounded the interaction between runoff and sediment load and fluvial processes, and predicted the evolution trend. Results suggest that the flow dynamic axis in river diversion zone shifts to the left with the flow increasing, giving rise to favorable conditions for the left branch and a long-term braided river pattern. But as the incoming sediment from the upstream reduces remarkably, erosion in the right branch is more severe than that in the left branch, favorable for the right branch to maintaining as the main branch.
Pentachlorophenol (PCP) has been widely used for killing oncomelania, the only intermediate host of schistosome in the middle and lower reaches of Yangtze River where schistosomiasis is epidemic in recent decades. Although the production and use of PCP is restricted currently, severe PCP contamination still exists in environment, which posed a potential danger to the aquatic ecosystem and human health. Soil and sediment are the primary containers of PCP in environment. Bioremediation is an option that may accelerate the removal of various environmental contaminants using the functions of biomes absorbing, metabolizing and biodegrading the contaminants, thus, bioremediation technology becomes a preferred way of treating PCP pollution. In the present paper, the effect and mechanism of bioremediation technology, inclusive of phytoremediation, microbial remediation, plant-microbial degradation technology, soil fauna remediation technology and composting technology are reviewed, and the future trend of bioremediation technology is predicted. The present paper aims to provide scientific basis and application fundamental for further research in the bioremediation technology and ecological remediation of PCP in aquatic environment in epidemic areas.
To explore the method of calculating river’s diffusion coefficient in the presence of pollution, a normal fuzzy linear regression model was built, and through the membership function of fuzzy set, the ranges of water quality parameters (transversal diffusion coefficient and average flow velocity) in the presence of different confidence levels were calculated. The model was built based on linear graphic method, and the tracer test data of water mass was analysed based on fuzzy numbers. The water quality parameters calculated by this model were very close to the real values, which accounts for the feasibility and rationality of this model. It could also reflect the uncertainty of river system and the effects of other uncertainties in practice.
Experiment points were set up in Liujiang river and a multi-index system of diatom is built up in order to effectively monitor water quality and improve physicochemical analysis. According to the results of correspondence analysis in different water functional zones of different water quality, AMIN, GOLI, DDEL, AMSA, ACLI, NAAN and NRHY are classified as clean species in the Liujiang river whereas Nitzschia and Luticola are stain species. Canonical correspondence analysis shows that the river water quality parameters are the main factors affecting the distribution of diatom communities. Nitrates, chlorides, total number of Fecal coliform and total phosphorus are the main variables, and physicochemical parameters are main variables based on the results of factor analysis. The results show that physicochemical variables are closely related with diatom indices IPS,IBD,TID, IDG and SLA. According to the water quality level from long-term monitoring and the data about clustering of water quality parameters and diatoms population, they are classified into three different water quality categories. IPS, IBD and CEE work well on the evaluation of water quality of the three categories while the diatom’s bio-diversity index are unsuitable for the evaluation. Through biological indices IBD and IPS, and VAN groups to divide eutrophic species percentages and physicochemical parameters, multi-index evaluation can be used to evaluate the quality of river water and ecological quality in order to improve the reliability of the evaluation.
Compared with traditional quantitative analysis methods and optimization methods, game theory could identify and interpret the behaviors of parties in water resource conflicts and describe the interactions among different parties. By comprehensively summarizing literatures, we make a review on the application of game theory to water resource conflicts from the perspectives of water allocation conflicts, trans-boundary water pollution conflicts and coordination mechanisms of water resource conflicts. In addition, some research prospects are proposed: macro-control of market economy is encouraged to be used to solve the conflict between water quality and water quantity; quantitative research on the allocation of initial water right needs to be intensified.
Geological monitoring as an effective technique of disaster prevention, has engineering significance for the monitoring of landslide deformation. IBIS-L (Image by Interferometric Survey) is an integration of interferometric survey, SAR technology, and stepped frequency wave. It is widely used in the monitoring of ground surface micro-deformation, but less applied to landslide deformation monitoring and in lack of unified monitoring and data processing method. A landslide in southwestern China was taken as an example and was monitored using this method based on preliminary geological understandings of the landslide on the prototype. The approaches of monitoring process and data processing are described in emphasis, and the deformation behavior are analysed. Comparison between the monitoring result with numerical simulation result verifies the feasibility of this IBIS-L system.
In order to get the explicit calculation formula of conjugate depth for semi-cubic, square, and cubic parabolic-shaped channels, the jump equations of the three parabola-shaped channels were transformed identically and the relationships between the dimensionless water depth x before jump and the dimensionless water depth y after jump were obtained according to the property that the critical depth was between the pre-jump depth and the post-jump depth. Their iterative formulas were further obtained respectively. Hence, a set of explicit calculation formulas of conjugate depth for semi-cubic, square, and cubic parabolic-shaped channels were obtained by fitting the iterative initial value through excel in common engineering scope. Finally, example and error analysis shows that the absolute value of maximum relative error of dimensionless water depth x before jump was 0.25%, 0.17%, and 0.31% respectively for the semi-cubic, square, and cubic parabolic-shaped channel, and that of dimensionless water depth y after jump was respectively -0.23%, -0.29%, and 0.39%. The formulas were convenient and highly accurate with clear physical meaning and wide application scope.
As stepped spillway has special structure and complex flow patterns, researches on the pressure in stepped spillway are not consistent. In view of this, we investigate into the effects of flow discharge, air entrainment, step size and spillway’s slope gradient on the distribution of time-averaged pressure through analysing the pressure data of skimming flow in several stepped spillways. Results reveal that big discharge per unit width leads to big time-averaged pressure. Air entrainment could effectively reduce positive time-averaged pressure and increase negative pressure. Effect of the step size is complicated: when the step size is small with gentle slope, pressure is small in the middle but large on both ends in vertical plane of the step; when step size is small with steep slope, minimum pressure occurs on the bottom and top of step in vertical plane; while when the step size is large, pressure decreases from the bottom to the top, and pressure variation intensifies with the increase of slope gradient.
Anchor cable is closely contacted with geotechnical body through reaction support. After a certain pre-stress is applied on anchor cable, the geotechnical body also deforms under the action of pre-stress. Due to the creep property of geotechnical body, its deformation doesn’t complete instantaneously but changes with time, which causes the long-term loss of pre-stress. In this research, anchor cable is equivalent to two models (elasticity body and generalized Kelvin body), and geotechnical body is assumed to be model of H+nK (n≤3) which could simulate the creep property of geotechnical body. According to the coupling deformation between anchor cable and geotechnical body and the initial conditions, formulas of calculating the pre-stress of anchor cable with the change of time are obtained. Through comparison with the results of previous studies, the correctness of this model is verified. Moreover, the fitting curve could be more consistent with the measured pre-stress variation if the number of K in creep model of geotechnical body is increased and the relaxation of anchor cable stress is considered in the theoretical model.
Puli bridge is a large suspension bridge with a main span of 628 m and tunnel-type anchorage on one side. Rock mass unloading and karst problem are the key issues of engineering geology in the tunnel anchorage area. An exploration hole of 120 m long was excavated through the center of the anchorage, and in-situ rock mechanical test, sonic test and geological description were conducted in the exploration hole. The physical and mechanical parameters of rock masses and the classification of basic quality of rock masses were obtained. On this basis, the regularities of rock mass unloading and karst development varying with elevation and embedded depth were analyzed. Comprehensive investigation technologies and analysis methods involving ground surface geological survey, geological mapping, drilling, tunnel excavation, pitting, trenching, elastic wave testing, and in-situ testing are explored in view of the possible engineering geological problems of tunnel anchorage in karst region. These technologies provide fundamental data for the design of tunnel anchorage and the stability analysis, and are worth to be popularized in similar works.
Triaxial creep tests on Q2 loess of different moisture contents were carried out to explore the creep properties of water-containing Q2 loess. Test results show that the rheological property of Q2 loess strengthens with the increase of moisture content. Furthermore, since the soft-matter element built by fractional calculus could simulate the material between ideal solid and ideal fluid, a four-element nonlinear creep model which contains the soft-matter element was applied to fit data, and the model parameters under different moisture contents were analyzed. The results suggest that instantaneous deformation modulus EH and viscoelastic coefficient ξ1 have a negative relationship with moisture content with an exponential decline. A water damage evolution equation of each creep parameter was obtained by introducing the water damage variable D(ω), which was further used to establish a nonlinear creep model in consideration of water damage effect. The nonlinear creep model was verified by test data. It was proved that the nonlinear creep model considering water damage could effectively characterize the overall rheological property of Q2 loess,and has a good application prospect.
In order to make sure that the deformation behavior of waste landfill’s vertical diaphragm wall meets requirements, we conducted nonlinear simulation on the deformation and stress of plastic diaphragm wall using ANSYS. The diaphragm wall of industrial waste landfill at Jashanzi in Changzhou, Jiangsu province was taken as an example. The plastic diaphragm wall was poured from anti-seepage slurry with bentonite, cement, and fly ash as main materials. Results reveal that the stress and deformation of the diaphragm wall meet the requirements. The stress and horizontal displacement both reached maximum at the bottom of the wall, the principal stress of wall increased at the clayey stratum, and no tensile stress was found; the maximum horizontal displacement of the wall is in linear relationship with the square of wall height. The results are reasonable and provide theoretical basis for engineering design and operation of waste landfill’s diaphragm walls.
A large bedded landslide occurred in Sunjia Town, Wanzhou District of Chongqing. There were multiple disintegration modes in the sliding process. In order to study the slip model of such bedded rock landslide, the slip structure and ground rupture were investigated. Furthermore on this basis, the landslide was partitioned and the sliding distance, movement patterns and building’s vulnerability were analysed. Results reveal that 1) potentially unstable slopes were made free by slope cutting of the leading edge of the quarry, and the anti-sliding force decreased, which triggered the sliding of shallow bedded weak shale in the middle and weathered contact zone in the back; 2) the primary slip body slid about 29.5m, the main slide direction was 5° and the thickness of slip body was about 15m; 3) affected by the change of weathered layer thickness and the previous topographical conditions, the partitioned disintegration was obvious after the sliding. The intensity of each partition’s effect on building’s vulnerability can be ranged as: front accumulation zone (Ⅵ) > groove damaging zone in the back edge (Ⅱ) > central nappe zone (Ⅳ), crushing zone (Ⅶ) > local block sliding zone (Ⅴ) > central thrust zone (Ⅳ) > integral sliding zone (Ⅲ1, Ⅲ2 )> affected zone in the back edge (Ⅰ). Moreover, the zoning map of landslide’s crushing and disintegration is given, and it has reference value for analyzing landslide risk distribution.
The physical and mechanical parameters (peak stress, peak strain), failure mechanism and post-peak strain softening (softening performance) of concrete with different sizes under different strain rates were researched through uniaxial dynamic compression test. The test was conducted on cubic concrete specimens of different sizes (150mm,300mm, 450mm) at different strain rates (10-5/s, 10-4/s, 10-3/s, 10-2/s) by large multi-functional electro-hydraulic servo static triaxial machine. Results showed that concrete’s peak stress and peak strain both reduced with the increase of specimen size; concrete strength increased with the increase of strain rate; after the peak strain occurred, the absolute value of the stress-strain curve slope increased whereas the ductility reduced as the specimen size increases. For the specimen size of 150mm, concrete softening strengthened with increasing strain rate, and the softening degree increased; while for the specimen size of 300mm and 450mm, the softening weakened when strain rate increased, but when the strain rate increased to a certain value, the softening became apparent. At the same strain rate, the softening was increasingly apparent with the increase of specimen size.
